Dissertations / Theses: 'Dosimeters – Evaluation'

1

Griffis, Neale Jeff. "Performance evaluation of the Dosicard electronic personal dosimeter." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/16991.

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2

Lhallabi, Abdessamad. "Evaluation des incertitudes dans la preparation et la realisation des traitements par radiotherapie transcutanee." Toulouse 3, 1987. http://www.theses.fr/1987TOU30076.

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3

Langdal, Ingrid. "Dosimetry and evaluation of algorithm for inverseoptimized doseplanning for brachytherapy." Thesis, Norwegian University of Science and Technology, Department of Physics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-6287.

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Abstract:

Purpose

Individual optimized treatment planning is recommended when creating treatment plans for brachytherapy of cervical cancer. Manual alteration of the dose distribution is time consuming and the treatment plan may be dependent on the person creating it. Inverse planning simulated anneahng (IPSA) is an algorithm that can optimize the dose distribution considering dose to several delineated structures. This algorithm, currently available in the treatment planning system Masterplan, has been evaluated for brachytherapy of cervical cancer. The Masterplan system simulates a source type from at different manufacturer than the type used for treatment at St. Olavs Hospital at the time being. The dose distribution from the two source types were evaluated to see if Masterplan an be used to simulate the source type used for treatment at St. Olavs Hospital.

Methods and materials

The dose distributions from the two source types were compared based on calcuations from two treatment planning systems (Masterplan and Plato) simulating each source type.

Dose measurements of the source used at St. Olavs Hospital for brachytherapy treatment of cervical cancer were taken. These were compared with the dose distribution calculated by the two treatment planning systems.

At St. Olavs Hospital treatment are executed using a Fletcher type applicator. MR-images are taken with the applicator in place. Target and organs at risk are delineated in the images before the treatment planning is performed. For 11 patients treated with brachytherapy of cervical cancer at St. Olavs Hospital, three different IPSA-plans with different dose constraints (IPSA1, IPSA2 and IPSA3) and one treatment plan with equal dwell times were made in retrospect. All IPSA-plans constrain the same dose to the target. IPSA1 and IPSA3 have the same constraints to organs at risk, while IPSA2 allow a higher dose to the organs at risk. IPSA3 sets a limit for maximum dose in target volume. For evaluation of the quality of the treatment plans, dose parameters of chnical relevance were extracted from dose volume histograms.

Results

Deviations in the calculated dose distribution up to 30% is found for the two source types in certain areas. These deviations are found close to the source and below the connector end of the source. For distances ≥ 4 mm from the source center along one axis, deviations of the calculations were ≤ 4%. This is in correspondance with the measured dose values.

Target coverage for IPSA2 is 0.92. For IPSA1 and IPSA3 target coverage is 0.84 and 0.81 respectively. The number of treatment plans exceeding tolerance limit for one or more OAR is 82% for IPSA2, 55% for IPSA1 and 35% for IPSA3. The plan with equal dwell times have a target coverage of 0.66 and 45% of the treatment plans exceed the given tolerance limit for one or more organs at risk.

Conclusion

Deviations are found in the simulated dose distribution of the two source types tested, but only in clinical irrelevant areas for brachytherapy of cervical cancer. Masterplan can be used for simulating the dose distribution of the source used for treatment at St. Olavs Hospital.

Using IPSA is better when it comes to improving target coverage and not violating tolerance limit for organs at risk, than a conservative treatment plan with equal dwell times. Due to too high doses to organs at risk, IPSA2 should be rejected. IPSA1 has better target coverage and IPSA3 have lower dose to the organs at risk. To avoid inhomogeneities in dwell time values, IPSA3 is probably the best suggestion.

Sammendrag

Formål

Det er anbefalt & lage individuelt optimaliserte plan når behandlingsplaner skal lages i forbindelse med brachyterapi av livmorhalskreft. Manuell endring av dosefordelingen er tidkrevende og resultatet kan bli preget av personen som lager planen. 'Iverse planning simulated anneahng' (IPSA) er en algoritme som kan optimalisere dosefordehngen slik at dose til flere skisserte strukturer blir tatt hensyn til. Denne algoritmen, tilgjengehg i doseplanleggingssystemet Masterplan, har blitt vurdert for brachyterapi av livmorhalskreft.

Masterplan simulerer en kildetype fra en annen produsent enn den kildetypen som blir brukt til behandling på St. Olavs hospital i dag. Dosefordehngen til de to kildetypene har blitt vurdert for å se om Masterplan kan brukes til å simulere kildetypen brukt til behandling.

Metode og utstyr

Dosefordehngen fra de to kildetypene ble sammenlignet ved hjelp av doseberegninger fra to doseplanleggingssystemer (Masterplan og Plato) som simulerer hver sin kildetype.

Det ble tatt målinger av dosen fra kilden brukt på St. Olavs hospital til brachyterapi av livmorhalskreft. Disse ble sammenlignet med dosefordelingen regnet ut av de to planleggingssystemene.

På St. Olavs hospital blir en Fletcher type apphkator brukt til behandling. MR-bilder blir tatt etter at applikatoren er posisjonert. I bildene blir målvolum og risikooganer skissert før behandlingsplanleggingen gjennomføres. I denne studien har tre ulike IPSA-planer med forskjellig doserestriksjoner (IPSA1, IPSA2 and IPSA3) og en plan med lik liggetid i kildeposisjonene, blitt laget i ettertid for 11 pasienter behandlet for livmorhalskreft på St. Olavs hospital. IPSA-planene har samme doserestriksjoner til målvolum. IPSA1 og IPSA3 har samme begrensning til risikoorganer, mens IPSA2 tillater høyere dose til risikoorganer. IPSA3 har en begrensning for maksimum dose til volum for måvolumet. For vurdering av kvaliteten til planene ble klinisk relevante doseparametre funnet fra dosevolum-histogram.

Resultat

Det ble funnet avvik opp til 30% for beregnet dose i ulike punkt for de to kildetypene i visse omr&der. Disse avvikene ligger nærme kilden og rett under koblingsenden. For avstander ≥ 4 mm fra kildesenter transversalt på kilden er avvikene i beregningene ≤4%. Dosemålingene som ble tatt støtter dette.

Dekning av målvolum er 0.92 for IPSA2. For IPSA1 og IPSA3 er denne dekninjen henholdsvis 0.84 og 0.81. Antall planer hvor en definert grense for dosen til et eller flere risikoorgan har blitt oversteget, er 82% for IPSA2, 55% for IPSA1 og 35% for IPSA3. Planen hvor liggetidene er fordelt likt har malvolumdekning på 0.66 og 45% av planene overstiger den definerte toleranse grensen for et eller flere risikoorgan.

Konklusjon

Det ble funnet avvik i de simulerte dosefordelingene mellom de to kildetypene, men kun i klinisk irrelevante områder for brachyterapi av livmorhalskreft. Masterplan kan bli brukt til å simulere dosefordelingen til kilden som blir brukt til behandling på St. Olavs hospital.

Bruk av IPSA gir bedre resultater enn den konservative behandlingsplanen med lik liggetid ncir det gjelder dekning av målvolum og å overholde toleransegrensene som er satt for risikorganene. På grunn av for høye doser til risikoorganer burde IPSA2 forkastes. IPSA3 gir bedre dekning av måvolum mens IPSA3 gir lavere dose til risikoorganer. For å unngå store forskjeller mellom liggetidene i de ulike kildeposisjonene vil antagelig IPSA3 gi best utganspunkt for videre planlegging.

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4

PASCOALINO, KELLY C. da S. "Estudo comparativo das respostas de diodos de Si para dosimetria de radiacao gama." reponame:Repositório Institucional do IPEN, 2010. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9517.

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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5

Pollitt, David Frederic. "Performance evaluation of a second generation metaphase finder for chromosome-based radiation dosimetry." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0009/MQ32550.pdf.

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6

Tölli, Heikki. "Ionization chamber dosimetry for brachytherapy evaluation of correction factors for absorbed dose determination /." Göteborg : Dept. of Radiation Physics, University of Göteborg, 1997. http://catalog.hathitrust.org/api/volumes/oclc/38990266.html.

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7

Meesat, Ridthee. "Evaluation of the radiosensitizing or radioprotective/antioxidant potential of some selected compounds by polyacrylamide gel dosimetry and Fricke dosimeter, and utilization of the femtosecond infrared laser pulse filamentation as a novel, powerful beam for cancer radiotherapy." Thèse, Université de Sherbrooke, 2012. http://hdl.handle.net/11143/6246.

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In radiation treatment, a sufficiently high radiation dose must be delivered to the tissue volumes containing the tumor cells while the lowest possible dose should be deposited in surrounding healthy tissue. We developed an original approach that is fast and easy to implement for the early assessment of the efficiency of radiation sensitizers and protectors. In addition, we characterized a new femtosecond laser pulse irradiation technique. We are able to deposit a considerable dose with a very high dose rate inside a well-controlled macroscopic volume without deposition of energy in front or behind the target volume. The radioprotective efficiency was measured by irradiation of the Fricke solution incorporating a compound under study and measuring the corresponding production of ferric ions G (Fe3+ ). The production of ferric ions is most sensitive to the radical species produced in the radiolysis of water. We studied experimentally and simulated with a full Monte-Carlo computer code the radiation-induced chemistry of Fricke/cystamine solutions. Results clearly indicate that the protective effect of cystamine originates from its radical-capturing ability, which allows this compound to compete with the ferrous ions for the various fre radicals - especially · OH radicals and H· atoms - formed during irradiation of the surrounding water. The sensitizing capacity of radiation sensitizers was measured by irradiation of a polyacrylamide gel (PAG) dosimeter incorporating a compound under study and measuring the corresponding increase in the gradient between spin-spin relaxation rate (R2 ) and absorbed dose. We measured an irradiation energy-dependent increase in R 2 -dose sensitivity for halogenated compounds or a decrease for radioprotectors. Finally, we studied a novel laser irradiation method called "filamentation". We showed that this phenomenon results in an unprecedented deposition of energy and the dose rate thus achieved exceeds by orders of magnitude values previously reported for the most intense clinical radiotherapy systems. Moreover, the length of the dose-fre entrance region was adjusted by selecting the duration of femtosecond laser pulses. In addition, we provided evidence that the biological damage caused by this irradiation was similar to other ionizing radiation sources. [symboles non conformes]

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8

MARRE, DELPHINE. "Evaluation des perturbations induites sur la mesure de la dose absorbee avec des chambres d'ionisation, des dosimetres chimiques et des dosimetres thermoluminescents dans des faisceaux d'electrons de haute energie." Toulouse 3, 2000. http://www.theses.fr/2000TOU30083.

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Le but de cette these est d'ameliorer la precision sur la determination de la dose absorbee avec des detecteurs usuels en radiotherapie, en particulier les chambres d'ionisation, les dosimetres chimiques et les dosimetres thermoluminescents (dtl), dans des faisceaux d'electrons de haute energie. En effet, la composition de ces detecteurs est generalement differente de celle du milieu environnant, ce qui engendre des perturbations sur la mesure de la dose absorbee. Le but recherche est de determiner les differents facteurs de correction qui sont associes a ces detecteurs dans les faisceaux d'electrons de 6 a 50 mev. Une approche experimentale et deux approches theoriques sont menees : la dosimetrie de fricke est prise comme reference pour la partie experimentale. Des calculs par la methode de monte carlo (egs4 et penelope) et la theorie generale de la cavite sont utilises pour la theorie. Les resultats theoriques sont ensuite confrontes aux mesures. La determination de la dose absorbee avec les chambres d'ionisation dans les faisceaux d'electrons s'effectue par l'application des protocoles de dosimetrie (par exemple iaea 1997 et 2000). Ces protocoles donnent des valeurs de facteurs de correction plus ou moins approchees pour certaines chambres d'ionisation, alors que d'autres ne sont pas repertoriees. Notre etude consiste a evaluer avec la meilleure precision possible les facteurs de correction de perturbation et de correction de qualite de faisceau pour les chambres d'ionisation plates et cylindriques. Notre etude des dtl consiste a evaluer le facteur de correction de qualite de faisceau pour le lif sous forme de poudre (dtl937). L'energie du faisceau d'electrons, les dimensions du dtl et la nature du milieu environnant sont les parametres d'influence etudies. Les resultats obtenus sont actuellement directement appliques pour la determination de la dose absorbee par dtl dans le laboratoire europeen de controle de qualite en radiotherapie equal-estro installe a l'igr.

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9

Belanger, Philippe. "MR based frickle-gelatin dosimetry : uncertainty evaluation and computerised analysis of measured dose distributions." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32759.

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Dynamically delivered intensity modulated beams (IMBs) pose unique verification problems that may be addressed with the use of integrating continuous 3D dosimeters such as gel based Fricke dosimeters. Accurate knowledge of the ability of these dosimeters to measure adequately and precisely the delivered dose is a prerequisite for their clinical use. The magnetic properties of the ferrous and ferric ions present in the gel based Fricke dosimeter after its irradiation are the basis for the use of magnetic resonance imaging (MRI) in the measurement of dose. This thesis presents the investigation of a 3D gel based Fricke dosimetry system (Fricke-gel). A software system is developed and spin-lattice relaxation rate (R1) images are computed from MR images of irradiated Fricke-gel phantoms in order to quantify the dosimetric uncertainties resulting from the MR imaging system, from the gel itself, as well as from the external parameters. The sensitivity and the minimum detectable dose of the Fricke-gel dosimeter are determined. Validation of the dosimeter's capacity to measure dose distributions is made through measurement of percent depth dose curves (PDD's), and field profiles (open and wedged). An example of clinical utilisation of the Fricke-gel dosimeter is presented. Dose distributions are evaluated visually by 3D software tools and quantitatively analyzed by dose-volume histograms. Results show a good correlation between the Fricke-gel measured dose distributions and treatment planning software dose calculations.

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10

Paudel, Nava R. "Nanoparticle-aided Radiation Therapy: Micro-dosimetry and Evaluation of the Mediators Producing Biological Damage." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1403142628.

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11

Antonovic, Laura. "Evaluation of the lithium formate EPR dosimetry system for dose measurements around 192Ir brachytherapy sources." Thesis, Stockholm University, Medical Radiation Physics (together with KI), 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-8317.

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The dose distribution around brachytherapy (BT) sources is characterized by steep dose gradients and an energy spectrum varying rapidly with depth in water around the source. These two properties make experimental verification of the dose distribution difficult, and put high demands on the dosimetry system in use regarding precision, size and energy dependence. The American Association of Physicists in Medicine (AAPM) recommends lithium fluoride (LiF) thermo-luminescence dosimetry (TLD) to be used for verification measurements, as it is the only dosimetry system meeting the requirements, but still the total combined uncertainty in dose-rate determination is as high as 7-9 % (1 σ). Lithium formate is a new dosimetry material that is less energy dependent than LiF, but more sensitive than the most common EPR (electron paramagnetic resonance) dosimetry material, alanine. In order to evaluate lithium formate EPR for BT dosimetry, dosimeters were produced for experimental dose determination around BT source 192Ir. The dosimeters were calibrated against an ionization chamber in a high energy photon beam. Dose to water was determined at 1, 3 and 5 cm radial distance from the source, which was stepped along a straight line in a PMMA phantom. The experiments were performed twice using 4 dosimeters per distance and experiment. Methods to correct for energy dependence were developed and evaluated. The uncertainty in measured dose was estimated. The experimental dose values agreed with the values from the treatment planning system with a maximum deviation of 3.3 %, and an average 1 σ uncertainty of 3 % at 3 and 5 cm and 5 % at 1cm. Uncertainty in radial distance from the source as well as source calibration were the dominating contributions to the total combined uncertainty. Lithium formate EPR has been shown to be a promising alternative to LiF TLD for BT dosimetry.

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12

Edén, Strindberg Jerker. "Evaluation of materials for ESR-dosimetry: Salts of formic and lactic acid as an example." Thesis, Stockholm University, Medical Radiation Physics (together with KI), 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-8318.

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The technique of ESR-dosimetry and strategies for investigation of new materials as in regard to their applicability as ESR-dosimeters for radiotherapy has been reviewed. As an example six salts of formic and lactic acid has been evaluated. The applicability of the dosimeter has been judged by evaluating the tissue equivalence, radical yield, radical stability, spectral suitability, optimal readout parameters, dose response and sensitivity of the dosimetric system. Dependence of material characteristics and influence parameters has been analysed.

The reviewed methods have been successfully used for evaluation of the new materials. Lithium formate has been shown to be a good candidate relative to the state of the art dosimeter of alanine. Using optimal readout parameters lithium formate has been shown to be nine times as sensitive but even at moderate settings lithium formate is more sensitive. The results for lithium formate are in accordance to those of previous studies. The signal intensity of sodium formate has also proved to be high but unfortunately the signal fades rapidly.

Two new methods have been proposed as synthesis of the reviewed methods. The first allows flexible, effective and objective baseline correction of the ESR-spectrum. The second deals with dose response measurement by linear regression of the entire spectrum and was found to be successful in separating the spectral peaks of the induced radicals from the background signal.

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13

Al-Yahya, Khalid S. "Energy modulated electron therapy : design, implementation, and evaluation of a novel method of treatment planning and delivery." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102951.

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Energy modulated electron therapy (EMET) is a promising treatment modality that has the fundamental capabilities to enhance the treatment planning and delivery of superficially located targets. Although it offers advantages over x-ray intensity modulated radiation therapy (IMRT), EMET has not been widely implemented to the same level of accuracy, automation, and clinical routine as its x-ray counterpart. This lack of implementation is attributed to the absence of a remotely automated beam shaping system as well as the deficiency in dosimetric accuracy of clinical electron pencil beam algorithms in the presence of beam modifiers and tissue heterogeneities. In this study, we present a novel technique for treatment planning and delivery of EMET. The delivery is achieved using a prototype of an automated "few leaf electron collimator" (FLEC). It consists of four copper leaves driven by stepper motors which are synchronized with the x-ray jaws in order to form a series of collimated rectangular openings or "fieldlets". Based on Monte Carlo studies, the FLEC has been designed to serve as an accessory tool to the current accelerator equipment. The FLEC was constructed and its operation was fully automated and integrated with the accelerator through an in-house assembled control unit. The control unit is a portable computer system accompanied with customized software that delivers EMET plans after acquiring them from the optimization station. EMET plans are produced based on dose volume constraints that employ Monte Carlo pre-generated and patient-specific kernels which are utilized by an in-house developed optimization algorithm. The structure of the optimization software is demonstrated. Using Monte Carlo techniques to calculate dose allows for accurate modeling of the collimation system as well as the patient heterogeneous geometry and take into account their impact on optimization. The Monte Carlo calculations were validated by comparing them against output measurements with an ionization chamber. Comparisons with measurements using nearly energy-independent radiochromic films were performed to confirm the Monte Carlo calculation accuracy for 1-D and 2-D dose distributions. We investigated the clinical significance of EMET on cancer sites that are inherently difficult to plan with IMRT. Several parameters were used to analyze treatment plans where they show that EMET provides significant overall improvements over IMRT.

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14

Petrie, Christian M. "Evaluation of Scattered Radiation in a Calibration Range Using Exposure Rate Energy Spectra." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313095840.

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15

Manninen, A. L. (Anna-Leena). "Clinical applications of radiophotoluminescence (RPL) dosimetry in evaluation of patient radiation exposure in radiology:determination of absorbed and effective dose." Doctoral thesis, Oulun yliopisto, 2014. http://urn.fi/urn:isbn:9789526206240.

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Abstract Computed tomography (CT) and interventional procedures cause relatively high patient doses compared with other imaging modalities in radiology. The optimization of the imaging equipment and procedures is important and necessary due to the known risks caused by ionization radiation. The different irradiation geometries and dose units between imaging techniques complicate the comparison of patients’ radiation exposure. Absorbed doses (D) of organs predict the tissue reactions of the procedures, while effective dose (E) is a useful means of comparing the stochastic effects of the different imaging procedures. A and E can be estimated from dosimetric measurements in a phantom. In vivo measurements are used during a radiological examination. In the present thesis, various properties of radiophotoluminescence dosimeters (RPLD) were investigated to verify the applicability of RPL dosimetry in radiology. The absorbed dose was determined in vaginal fornix of seven pregnant women, in the area near the head of the fetus during prophylactic catheterization before uterine artery embolization (UAE). The evaluation of the radiation exposure of digital subtraction angiography (DSA) and computed tomography angiography (CTA) was performed using an anthropomorphic phantom. Absorbed doses of organs and effective dose were determined for a typical four-vessel angiography of the cerebral area, including intracranial vessels, and for the cervicocerebral area, including both cervical and intracranial vessels. RPLD shows excellent dose linearity and minimal fading. The low dose detection threshold was determined to be 20 µGy with a coefficient of variation (CV) of 12.2%. The methodology is independent of photon energy in the energy range used in radiology. For seven patients studied, the mean value of D in vaginal fornix was 11.2 mGy (range 2.2–28.7) being low dose study when pulsed fluoroscopy with an optimized protocol is used without angiography exposures. In the assessment of cerebral vessels, the effective dose for CTA was approximately one-fifth of the dose compared with DSA. The dose for cervicocerebral vessels CTA was approximately one third higher compared with DSA. Conversion factors from the DAP and the DLP to the effective dose were calculated for the specific angiographic protocols. RPL dosimetry shows sufficient reliability in measuring radiation doses in radiology
Tiivistelmä Tietokonetomografiakuvauksissa ja toimenpideradiologisissa tutkimuksissa potilaan säteilyaltistus on suhteellisesti korkeampi verrattuna muihin radiologisiin kuvausmenetelmiin. Kuvauslaitteiden erilaiset kuvausgeometriat ja annosyksiköt hankaloittavat potilaan säteilyaltistuksen vertailua eri tutkimusmenetelmien välillä. Kudokseen absorboituneen annoksen (D) avulla arvioidaan ionisoivan säteilyn suoraa haittavaikutusta kudokselle, kun taas efektiivisen annoksen (E) määrittämisellä arvioidaan säteilyn satunnaista haittaa. D ja E voidaan mitata annosmittarilla käyttäen potilasvastinetta. In vivo mittauksella saadaan annostietoa tutkimuksen aikana suoraan potilaasta. Radiofotoluminesenssiannosmittarin (RPLD) soveltuvuus radiologisiin annosmittauksiin varmistettiin tutkimalla mittarin eri fysikaalisia ominaisuuksia. RPLD:a käytettiin intravaginaalisen annoksen mittauksessa seitsemällä raskaana olevalla naisella. Potilaille tehtiin massiivisen verenvuodon ehkäisemiseksi kohdun valtimosuonten katetrointi läpivalaisuohjattuna ennen kohtuvaltimoiden tukkimishoitoa (UAE). Mittaustulokset antavat tietoa kudokseen absorboituneesta annoksesta lähellä syntymätöntä lasta. Tietokonetomografia-angiografia (TTA) ja digitaalinen subtraktioangiografia (DSA) tutkimusten annosmittaukset tehtiin potilasvastineessa käyttäen RPLD:a. Elinannoksista laskettiin efektiivinen annos aivovaltimoiden ja aivokaulavaltimoiden angiografiatutkimuksille. RPL -annosmittausmenetelmän havaittiin olevan lineaarinen ja annoksen häviäminen mittarista on vähäistä. Matalan annoksen mittausraja oli 20 µGy 12.2% toistettavuudella. RPLD on riippumaton säteilyenergiasta radiologiassa käytettävällä energia-alueella. Seitsemän potilaan keskimääräinen absorboitunut annos oli 11.2 mGy (vaihteluväli 2.2–28.7 mGy) emättimen pohjukasta mitattuna. Annostaso osoittaa, että katetrointitoimenpide on matala-annostutkimus, kun toimenpide tehdään läpivalaisuohjauksessa, eikä angiografisia kuvia käytetä. Aivovaltimoiden TTA:n efektiivinen annos oli viidesosa DSA menetelmän annoksesta. Aivokaulavaltimoiden TTA:n efektiivinen annos oli arviolta 35% korkeampi kuin DSA menetelmän annos. Konversiokertoimet DAP ja DLP yksiköistä efektiivisen annoksen laskemiseksi määritettiin tutkimuksessa käytetyille kuvausohjelmille. RPL -menetelmä osoitti riittävää luotettavuutta radiologisten säteilyannosten mittauksessa

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Collins, Kevin Scott. "EVALUATING DIFFERENCES IN TEST ACHIEVEMENT OF MEDICAL DOSIMETRY STUDENTS PARTICIPATING IN INSTRUCTION WITH SYNCHRONOUS VERSUS ASYNCHRONOUS VIDEO CONSIDERING PERSONAL LEARNING STYLE AND BLOOM'S TAXONOMY LEVEL." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/dissertations/371.

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The purpose of this study was to determine the dominant learning style of dosimetry students. The study also investigated to see if there was a significant difference in test performance based on synchronous/asynchronous participation, specific learning style, and the Bloom's taxonomy level of the test questions. To conduct the study, 25 medical dosimetry students enrolled at an accredited university were studied. Fifteen students participated in the course through a synchronous format using live video conferencing. Ten students used streaming video for their instruction in an asynchronous format. To determine the students' learning styles, Kolb's Learning Style Inventory was used. Findings from the study indicated the most common learning styles of dosimetry students were converging and assimilating. The study also found no significant differences in test performance by students based on synchronous or asynchronous class participation, individual learning style, or the item's Bloom's taxonomy level. Even though no significant differences were found, this study offers insight to potential students and dosimetry educators about taking or offering distance education courses.

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17

McKinnies, Richard C. "Evaluating Assessment and Effectiveness Data to Program Characteristics in Accredited Medical Dosimetry Programs in the United States." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/dissertations/1801.

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The purpose of this study is to analyze medical dosimetry programs in the United States with regard to their assessment data and specific program characteristics. I identified participating programs through the Joint Review Committee on Education in Radiologic Technology (JRCERT) program directory web page for medical dosimetry programs. Once I acquired the email addresses of each program director for all 18 programs, I emailed the program directors requesting their participation in the study. Six program directors responded to the email request and sent all the needed data for the study. The specific data evaluated in this study is assessment data for all four student learning objectives (SLO’s) identified by the JRCERT and program effectiveness data (i.e. certification pass rates, job placement rates for graduates, and attrition rates). I correlated the assessment data and program effectiveness data for each program to look for significance in comparison to the length of time a program received accreditation by the (JRCERT), length of each program academically, and the degree granted by each program. For the variables, I ran a Pearson Correlation and a linear regression, which also provides a significance value for the linear regression. The findings of the study illustrated no significance within the data when comparing it to the specific program characteristics. The study did illustrate some predictability within the linear regression, but did not illustrate any significant linear regression among the data points. This illustrates the dependent variables do not correlate with the independent variables, but are able to explain some of the variability in the dependent variable. Program accreditation is an important aspect for any medical dosimetry program and should be an integral part of the daily mechanisms. Educators need to continually look for ways to improve their assessment endeavors to help improve their programs and student success. Based on the findings of this study, research should continue on assessment data in the field of radiologic sciences and specifically in the field of medical dosimetry with larger population groups.

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Koyama, Shuji, Takahiko Aoyama, Nobuhiro Oda, and Chiyo Yamauchi-Kawaura. "Radiation dose evaluation in tomosynthesis and C-arm cone-beam CT examinations with an anthropomorphic phantom." American Institute of Physics, 2009. http://hdl.handle.net/2237/14184.

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19

Stambaugh, Cassandra. "The Evaluation and Study of Modern Radiation Dosimetry Methods as Applied to Advanced Radiation Therapy Treatments Using Intensity Modulated Megavoltage Photon Beams." Scholar Commons, 2015. https://scholarcommons.usf.edu/etd/5587.

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The purpose of this work is to evaluate quasi-3D arrays for use with intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) and to determine their clinical relevance. This is achieved using a Delta4 from Scandidos and ArcCheck from Sun Nuclear and the associated software. While certain aspects of these devices and software have been previously evaluated, the main goal of this work is to evaluate the new aspects, such as reconstructing dose on a patient CT set, and extending the capabilities. This includes the capability to reconstruct the dose based on a helical delivery as well as studying the dose to a moving target using measurement-guided motion simulations. It was found that Sun Nuclear's ArcCheck/3DVH system exhibited excellent agreement for dose reconstruction for IMRT/VMAT using a traditional C-arm linear accelerator and stringent 2%/2mm comparison constraints. It also is a powerful tool for measurement-guided dose estimates for moving targets, allowing for many simulations to be performed based on one measurement and the target motion data. For dose reconstruction for a helical delivery, the agreement was not as good for the stringent comparison but was reasonable for the clinically acceptable 3%/3mm comparison. Scandidos' Delta4 shows good agreement with stringent 2%/2mm constraints for its dose reconstruction on the phantom. However, the dose reconstruction on the patient CT set was poor and needs more work. Overall, it was found that quasi-3D arrays are powerful tools for dose reconstruction and treatment plan comparisons. The ability to reconstruct the dose allows for a dose resolution comparable to the treatment plan, which negates the previous issues with inadequate sampling and resolution issues found when just comparing the diodes. The ability to quickly and accurately compare many plans and target motions with minimum setup makes the quasi-3D array an attractive tool for both commissioning and patient specific quality assurance.

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20

Kalavagunta, Chaitanya. "Evaluation of optically stimulated luminescence A1₂O₃:C detectors for use in diagnostic computed tomography." Oklahoma City : [s.n.], 2008.

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21

Palmer, Randahl Christelle. "Evaluation of internal contamination levels after a radiological dispersal device using portal monitors." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37115.

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In the event of a radioactive dispersal device (RDD), the assessment of the internal contamination level of victims is necessary to determine if immediate medical follow-up is necessary. Thermo Scientific's TPM-903B Portal Monitor was investigated to determine if it is a suitable first cut screening tool for internal contamination assessment of victims. A portal monitor was chosen for this study because they are readily accessible, transportable, easy to assemble, and provide whole body count rates due to the detector size. The TPM-903B was modeled in Monte Carlo N-Particles Transport Code Version 5 (MCNP). This computational model was validated against the portal monitor's response to a series of measurements made with four point sources in a polymethyl methacrylate (PMMA) slab box. Using the validated MCNP5 model and models of the MIRD male and female anthropomorphic phantoms, the response of the portal monitor was simulated for the inhalation and ingestion radionuclides from an RDD. Six representative phantoms were considered: Reference Male, Reference Female, Adipose Male, Adipose Female, Post-Menopausal Adipose Female, and 10-Year-Old Child. The biokinetics via Dose and Risk Calculation Software (DCAL) was implemented using both the inhalation and ingestion pathways to determine the radionuclide concentrations in the organs of the body which were then used to determine the count rate of the portal monitor as a function of time. Dose coefficients were employed to determine the count rate of the detector associated with specific dose limits. These count rates were then compiled into procedure sheets to be used by first responders during the triaging of victims following an RDD.

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22

FERREIRA, IVALDO HUMBERTO. "Evaluation des perturbations induites sur la mesure de la dose absorbee avec des dosimetres thermoluminescents et des chambres d'ionisation dans des faisceaux de photons de haute energie." Toulouse 3, 1998. http://www.theses.fr/1998TOU30168.

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La determination de la dose absorbee dans un milieu irradie par des faisceaux de photons de haute energie avec des dosimetres thermoluminescents et des chambres d'ionisation implique la prise en compte des perturbations induites par la presence de ces detecteurs dans le milieu. L'objectif de cette etude est de determiner ces facteurs de correction de perturbation avec une grande exactitude et de les analyser en vue d'une application pour la dosimetrie en radiotherapie externe, et en particulier pour le domaine d'energie de faisceaux allant des photons du #6#0co aux rayons x de 25 mv. Deux methodes sont considerees : l'une est experimentale et l'autre theorique, fondee d'une part sur des calculs analytiques et d'autre part sur des calculs par la methode de monte carlo (code egs4-presta i). L'etude concernant les dosimetres thermoluminescents (dtl) montre l'influence des differents facteurs tels que les dimensions et la masse volumique du dtl et la concentration du dopant dans le cadre de la theorie generale de la cavite de burlin. La variation de la reponse des dtl en fonction de la qualite du faisceau d'irradiation a egalement ete etudiee. Dans le cas pratique des controles de qualite en radiotherapie effectues a l'institut gustave-roussy, une etude a ete realisee sur l'influence de differents parametres sur la reponse des dtl : support et conditionnement des dtl, heterogeneites autour des dosimetres. Les incertitudes associees a la determination de la dose absorbee dans l'eau a partir des dosimetres thermoluminescents ont ete calculees. Pour les chambres d'ionisation, les differents facteurs de correction, dus a la presence de la paroi, des capuchons d'etancheite et de l'electrode centrale sont determines. Une evaluation par calculs de monte carlo des facteurs globaux de correction de perturbation a ete realise pour des chambres d'ionisation etalons primaire (bipm) et secondaire (ird). Cette evaluation a permis la validation de la methode de calcul par monte carlo du facteur global de correction de perturbation, utilise lors de la determination de la dose absorbee dans l'eau.

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BANADOS, PEREZ HOMERO E. "Desenvolvimento de um sistema calorimetrico para dosimetria de feixes de eletrons em processos por radiacao." reponame:Repositório Institucional do IPEN, 1994. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10356.

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Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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24

TAIPINA, MAGDA S. "Efeito da radiacao gama sobre o conteudo de tocoferois em produtos naturais e industrializados e avaliacao sensorial." reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9381.

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IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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25

GROPPO, DANIELA P. "Caracterização dosimétrica de amostras de BeO em feixes de radiação alfa, beta e X por técnicas luminescentes." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10576.

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IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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26

Reis, Cristiano Queiroz Melo dos. "Study and evaluation of correction factors applied to ionization chambers in radiotherapy photon beams." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/59/59135/tde-08092015-164732/.

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The use of a beam quality correction factor,kQ, is needed in dosimetry of radiotherapy beams for correcting differences between chamber responses at the calibration beam quality, Q0 and at the quality beam of the user, Q. The purpose of this study is to determine the beam quality correction factor for the NE2571 ionization chamber widely used in radiotherapy and its dependence with the stopping-power and the chamber perturbation factors. In addition, an investigation of the use of parallel plate chambers for determining surface doses in photon beams is also performed using the EGSrnc Monte Carlo code system. Results obtained with PENELOPE show that simulations with phase-space files appropriately scored can be up to ten times shorter than using a full spectrum in the input-file. Values of kQ, and its components show good agreement with published values in the literature and are provided with typical statistical uncertainties of 0.2%. Values of kQ and absorbed dose to water conversion factors obtained with egs_chamber user code for parallel plate chambers are also provided with maximum statistical uncertainty of 0.7%. Therefore, the results obtained are expected to contribute with improving dosimetry protocols and the quality of life of radiotherapy patients.
O uso de uma fator de correção para a qualidade do feixe, kQ, é necessário em dosimetria de feixes radioterápicos para a correçãoo das diferenças entre a resposta de câmaras de ionização nas qualidades do feixe de calibração, Q0 e do usuário Q. O propósito deste trabalho consiste em determinar o fator de correção da qualidade de feixe para a câmara de ionização NE2571 amplamente utilizada em radioterapia e sua dependência com o stopping-power e os fatores de perturbação da câmara. Além disso, uma investigação do uso de câmaras de placas paralelas para determinar doses na superfície em feixes de fótons é também realizada usando o sistem de códigos em Monte Carlo EGSnrc. Resultados obtidos com o PENELOPE mostram que simulações usando phase-space, podem ser cerca de dez vezes menos longa do que simula ções usando um espectro completo no arquivo de entrada. Valores de kQ e suas componentes mostraram boa concordncia com dados publicados na literatura e são fornecidos com incertezas estatísticas típicas de 0.2%. Valores de kQ e fatores de conversão pra dose absorvida na água obtidos para as câmaras de placas paralelas com o código de usuário egs_chamber são também fornecidos com incerteza estatística máxima de 0.7%. Deste modo, espera-se que os resultados obtidos possam contribuir com o aperfeiçoamento de protocolos de dosimetria e com a qualidade de vida de pacientes radioterpicos.

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El, Barouky Jad. "Evaluation des algorithmes de calcul de dose pour les faisceaux d’électrons utilisés en radiothérapie : comparaison aux mesures par films radiochromiques." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA11T002/document.

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La précision du calcul de dose est cruciale pour la qualité de la planification et de la réalisation des traitements en radiothérapie. L’objectif de ce travail était d’évaluer la qualité des algorithmes de calcul de dose des faisceaux d’électrons pour des conditions particulières proches des situations cliniques rencontrées. Une méthodologie spécifique de dosimétrie par films radiochromiques des faisceaux d’électrons a été développée et validée, y compris pour des situations difficiles avec une précision de 3.1% en dose absolue et 2.6% en dose relative. Cette technique a permis de développer des tests de Contrôle Qualité généralistes rapides et efficaces qui servent de base de données mesurées en cas de changement de version du système de planification de traitement et/ou d’algorithme de calcul de dose. Les mesures par films ont été comparées avec les calculs de deux algorithmes de calcul de dose Pencil Beam et Monte Carlo. Les deuxcodes ont donné des résultats similaires dans les tests d’obliquité, d’irrégularité et de DSP étendue. En revanche, les calculs Monte Carlo sont plus précis en présence d’hétérogénéités. D’autre part, cette méthode de dosimétrie par films radiochromiques a permis de développer un nouveau mode d’évaluation des plans de traitement avec des films découpés et insérés dans des fantômes anthropomorphiques (de type thorax et tête) de manière à obtenir la distribution de dose en 2D dans un plan transversal donné ; ces tests cliniques pouvant aussi être utilisés dans le cadre d’un Contrôle de Qualité interne adapté à l’activité clinique du service. La comparaison des mesures avec les calculs a montré une meilleure précision dans les calculs Monte Carlo par rapport aux calculs Pencil Beam au niveau des hétérogénéités, notamment dans les poumons, les cavités et les os
In radiotherapy, the dose calculation accuracy is crucial for the quality and the outcome of the treatments. The purpose of our study was to evaluate the accuracy of dose calculation algorithms for electron beams in situations close to clinical conditions. A new practical approach of radiochromic film dosimetry was developed and validated especially for difficult situations. An accuracy of 3.1% and 2.6% was achieved for absolute and relative dosimetry respectively. Using this technique a measured database of dose distributions was developed to form the basis of several fast and efficient QualityAssurance tests. Such tests are intended to be used also when the dose calculation algorithm is changed or the Treatment Planning System replaced. Pencil Beam and Monte Carlo dose calculations were compared to the measured data for simple geometrical phantom setups. They both gave similar results for obliquity, surface irregularity and extended SSD tests but the Monte Carlo calculation was more accurate in presence of heterogeneities. The same radiochromic film dosimetry method was applied to film cuts inserted into anthropomorphic phantoms providing a 2D dose distribution for any transverse plan. This allowed us to develop clinical test that can be also used for internal Quality Assurance purposes. As for simpler geometries, the Monte Carlo calculations showed better agreement with the measured data than the Pencil Beam calculation, especially in presence of heterogeneities such as lungs, cavities and bones

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ALMEIDA, SHIRLANE B. de. "Validação e avaliação dosimétrica empregando as técnicas de TL e OSL de materiais termoluminescentes para aplicação na dosimetria de feixes clínicos de elétrons utilizados na irradiação total da pele - TSI." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/27973.

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A dosimetria in vivo têm se tornado um papel importante para o tratamento da irradiação total da pele dentro de um rigoroso programa de garantia de qualidade que deve ser parte integrante nos departamentos radioterápicos. A dosimetria em TSI é difícil, devido à complexidade do tratamento em avaliar a uniformidade da dose e medir a dose absorvida em profundidades rasas em toda extensão da superfície cutânea, tendo como consequência uma ampla variação na distribuição da dose. Os TLDs tem provado ser muito úteis para a distribuição e verificação da dose prescrita para o paciente, pois a dose pode diferir de local para local devido a geometria do corpo do paciente, sobreposições de estruturas e assimetrias do campo de radiação. A utilização de TLDs in vivo pode identificar variações da dose prescrita por apresentarem uma grande exatidão e precisão nas medidas. Nos setores de radioterapia vêm sendo empregado vários tipos de dosímetros, os mais utilizados são o Flureto de Lítio (TLD-100), onde obtém uma longa história neste tipo de aplicação. Novos materiais dosímetricos vêm ganhado grande importância na aplicação da dosímetria de feixes clínicos de elétrons, como o Sulfato de Cálcio dopado com Disprósio (TL) e o Óxido de Alumínio dopado com Carbono (OSL), este trabalho avalia o desempenho dosímetrico dos respectivos dosímetros termoluminescentes e a luminescência opticamente estimulada na aplicação da dosímetria de feixes clínicos de elétrons utilizados na irradiação total da pele.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

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29

MARTINI, GISELA de A. "Avaliação da citotoxicidade do Dietiltoluamida (DEET) em mexilhões Perna perna (Linnaeus, 1758) irradiados e não irradiados com radiação gama de sup(60)Co." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10579.

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IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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30

Arns, Anna Maria [Verfasser], and Frederik [Akademischer Betreuer] Wenz. "Towards clinical implementation of ultrafast combined kV-MV cone-beam CT for IGRT of lung tumors within breath-hold: evaluation of dosimetry and registration accuracy based on phantom studies / Anna Maria Arns ; Betreuer: Frederik Wenz." Heidelberg : Universitätsbibliothek Heidelberg, 2017. http://d-nb.info/1180735986/34.

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31

McKenna, Frederick W. "Studies of cell survival curve fitting, effective doses for radiobiological evaluation in SBRT treatment techniques and the dependence of optical density growth in Gafchromic EBT film used in IMRT." Oklahoma City : [s.n.], 2009.

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32

Amaral, Leonardo Lira do. "Desenvolvimento de uma metodologia de avaliação dosimétrica de transmissão, usando filmes radiocrômicos em tratamentos radioterápicos." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/59/59135/tde-13052014-144712/.

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Apesar da introdução do controle da qualidade individual nas técnicas complexas de tratamentos, tem-se comprovado que, mesmo assim, é possível a ocorrência de erros na aplicação da dose no momento da aplicação. No entanto, ainda não estão bem estabelecidas as ferramentas de redundância a fim de controlar a dose no momento da terapêutica, além do que, as técnicas mais modernas de tratamento radioterápico desenvolvem as aplicações com feixes rotacionais e os dosímetros tradicionalmente utilizados em controle da qualidade oferecem limitações angulares. Assim, este trabalho vem contribuir para o desenvolvimento de uma metodologia de controle da qualidade de transmissão in vivo utilizando filmes radiocrômicos acoplados ao cabeçote do acelerador linear, durante aplicações radioterápicas nas técnicas de tratamento conformacional e IMRT. A metodologia de controle da qualidade desenvolvida neste trabalho baseia-se na obtenção da distribuição de dose in vivo de tratamentos radioterápicos com um filme radiocrômico EBT2 posicionado em um suporte acrílico, semelhante a uma bandeja, a uma distância fonte-superfície de 56,8 cm, acoplado ao acessório holder do acelerador linear durante a aplicação de todo o tratamento teleterápico. Posteriormente, foi realizada uma análise gama para comparação da distribuição de dose medida pelo filme com a esperada pelo sistema de planejamento, obtida no plano coronal e central de um objeto simulador, com dimensões semelhantes ao suporte acrílico, posicionado à distância de 100 cm, como resultado da transferência do plano em questão. Com os resultados encontrados na seção conformacional, avaliando tanto a simulação Monte Carlo quanto as irradiações, pode-se concluir que a diferença entre a distribuição de dose do sistema de planejamento, na distância foco detector de 100 cm, e do filme, na distância de 56,8 cm, é diminuta e, desta forma, é viável criar uma metodologia para verificação dosimétrica de transmissão utilizando o filme radiocrômico acoplado ao cabeçote do acelerador. O controle da qualidade proposto na técnica de IMRT concordou com o esperado em 24 das 25 situações testadas, apresentando apenas um resultado diferente, ou seja, uma concordância de 96% com o esperado. As avaliações in vivo concordaram com 98% dos controles avaliados. Desta forma, pode-se concluir que a metodologia proposta neste trabalho é factível para o controle da qualidade de transmissão in vivo, em tratamentos radioterápicos que usam a técnica de tratamento conformacional e IMRT e, como ela não oferece dificuldades para o deslocamento angular do gantry, ela poderá ser aplicada em técnicas teleterápicas mais modernas.
Even with the introduction of the individual quality control in the complex techniques of radiation therapy treatments, the occurrence of errors in the release of the dose at the time of application is possible. However, in order to monitor the dose at the time of therapy, redundancy tools are not yet well established, Besides that, the most modern techniques of radiation treatment use rotational beams to deliver the desired dose distributions and the dosimeters traditionally used in quality control of radiation therapy suffer angular limitations. In this way, this work aims to contribute to the development of a methodology of transmission quality control in vivo presenting a dose control technique using radiochromic film coupled to the headstock linear accelerator for radiotherapy applications to monitor conformational techniques and IMRT treatment. The quality control methodology developed in this work is based on obtaining the in vivo dose distribution of radiotherapy treatments with a radiochromic film EBT2, positioned on an acrylic stand, similar to a tray at a source-surface distance of 56.8 cm, coupled to the linear accelerator accessory holder during application of any treatment. It was subsequently performed a gama analysis for comparison of the dose distribution measured by the film with the expected dose distribution by the treatment planning system. The expected dose distribution was obtained in the coronal and central plane of a phantom, with similar dimensions to the acrylic stand and positioned on a source-surface distance of 100 cm as a result of the transfer of the plan in question. Based on the results presented in the conformational section, evaluating both, Monte Carlo simulation and irradiation results, it can be concluded that the difference between the distribution of the dose planning system, focus distance 100 cm detector, and the film, on distance of 56.8 cm, are small, and in this way it is feasible to create a methodology for dosimetry verification using radiochromic film coupled to the head of the accelerator. The proposed quality control in IMRT technique agreed with expected in 24 simulations of the 25 situations tested, showing only one different result, i.e., there was a 96% concordance with the expected. In this way, it can be concluded that the methodology proposed in this work is feasible for the in vivo quality control of radiation therapy treatments that use the conformational and IMRT treatment techniques, and also can be applied to the most modern radiotherapy techniques since, it does not offer difficulties with the angular displacement of the gantry.

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BRANCO, ISABELA S. L. "Estudo dos efeitos na dose devido à heterogeneidade em braquiterapia com fontes de I125." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28045.

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A braquiterapia de baixas taxas de dose realizada com sementes de 125I tem sido amplamente usada por décadas em variados sítios anatômicos, com bons resultados clínicos. O advento de algoritmos para cálculo de dose baseados em modelos (MBDCAs) permitiu aprimorar oestudo de deposição da dose considerando heterogeneidades como diferentes tecidos, órgãos,aplicadores com composições diferentes da água, proporcionando a análise em geometriascomplexas. As simulações matemáticas realizadas através destes algoritmos possibilitam odesenvolvimento de modelos fisicamente mais acurados que estendem sua aplicabilidade àverificação de sistemas de planejamento em braquiterapia. Neste trabalho foram estudadasconfigurações de objetos simuladores confeccionados para medidas experimentais e simuladosatravés do código MCNP de Monte Carlo a fim de observar as diferenças ocasionadas pelaintrodução de heterogeneidades quando presentes fontes de 125I de baixa taxa de dose. Para estepropósito, distintas as vertentes do tema foram abordadas, entre elas o estudo da influênciaexercida pelos parâmetros de densidade e composição dos materiais tecido equivalentes. Osresultados obtidos demonstraram que, o efeito que a composição de cada um dos materiaisexerce sobre a deposição de dose é mais expressivo que o efeito de sua densidade. Em outroestudo, foi estabelecida uma relação para estimar, de maneira simples, a dose de atenuação detecidos heterogêneos a partir da aferição ou simulação da dose obtida num objeto simuladorconstituído por PMMA, metodologia que pode ser desenvolvida e implementada na rotina clínica.Para complementação das análises dos estudos dosimétricos com a presença deheterogeneidades, foi realizada a validação da geometria simulada da semente de 125I, onde sereproduziu a metodologia de cálculo dosimétrico presente no TG-43 da AAPM. Além disto, foirealizado o estudo teórico da dependência energética dos dosímetros termoluminescentes paraanalisar a variação de sua resposta conforme a energia. A metodologia desenvolvida para oestudo dos efeitos da heterogeneidade na deposição de dose é recomendada na avaliação desistemas de planejamento computadorizados que possuem algoritmos de cálculo de dosebaseados em modelos, quando utilizadas fontes de 125I com baixa taxa de dose, de forma acontribuir na incorporação de novas estimativas de doses com maior acurácia.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

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34

Tietze, Lorrie R. "Evaluation of a four-element beta gamma personnel dosimetry badge." 1985. http://hdl.handle.net/2097/27560.

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CHEN, CHI-CHUNG, and 陳志忠. "Evaluation of radiation dose and occupational safety in cardiac catherization room using optically stimulated luminescent dosimeters." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/rs2fs3.

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碩士
元培醫事科技大學
醫學影像暨放射技術系碩士在職專班
104
Changes in Taiwanese people’s living and dietary habits have led to an increase in the number of patients with cardiovascular disease. According to a statistical report released by the Taiwan Ministry of Health and Welfare in 2014,cardio- and cerebrovascular diseases ranked second and third among the 10 leading causes of death, respectively. In Taiwan, the prevalence of hypercholesterolemia increased from 4.3% in the 1970s to 12.7% in the 1990s, and the prevalence of hypertriglyceridemia increased from 6.5% to 24.1%; indicating that 12–24 in 100 people have had vascular disease. Although cardiac catheterization is an invasive test, its diagnostic efficacy is excellent, and patients can be treated without undergoing surgery. X-rays are an indispensable interventional radiologicalprocedure, but patients treated at cardiac catheterization laboratories and angiography roomsare exposed to long-term radiation, which can also affect staff. Therefore, this study employed an optically stimulated luminescence dosimeter to measure the environmental radiation dose received by patients and staff in a cardiac catheterization laboratory during cardiac catheterizationto elucidate possible radiation safety problemsfrom performing X-rays during cardiac catheterization.real intention to implement screening. In this study, an optical stimulated luminescence dosimeter (OSLD) was employed to determine the required dose level for cardiac catheterization photography and to understand radiation safety and space dose rates for cardiac catheterization examination. The seasonal period from November 2014 to January 2015, which featured the highest number of cardiac catheterization examinations, was chosen to investigate dose assessment, the use of proper positions for dose distribution measurement, the placement of the OSLD fabricated from aluminum oxide on a prosthesis surface inside and outside the optical field, and the measurement of accumulated space dose rates. According to the results, the highest dose level at the radiation source center among various cardiac catheterization examination durations was 84 mSv; on average, for every 100,000 people who received cardiac catheterization surgery, 14.98 people were diagnosed with lethal cancer. Because some doctors did not wear a lead collar, for every 100,000 doctors, 0.485 doctors were diagnosed with lethal thyroid cancer. The dose level was related to the X-ray fluoroscopy duration, photographic conditions, disease complexity, and operation skills. The average fluoroscopy time for the highest surface dose level was 1488 s. We suggest that the fluoroscopy time should not influence diagnosis quality and that patients should avoid long exposure to fluoroscopy; accordingly, efficient fluoroscopy procedures should be implemented.

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Huang, Tsung-Chieh, and 黃琮傑. "N-isopropylacrylamide Gel Dosimeters for Dose Verification of IMRT Treatment using 3D Gamma evaluation and Dose-volume Histogram." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/87994149062416856080.

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碩士
中臺科技大學
醫學影像暨放射科學系暨研究所
103
Polymer gel dosimeters can record integrated absorbed dose in 3D. In addition, polymer gel dosimeters can exhibit 3D dose distribution of patients. In this study, N-isopropylacrylamide (NIPAM) gel dosimetry with magnetic resonance imaging (MRI) was employed to measure 3D dose distributions in clinical radiation treatment of eye tumor patients. This study comprised the following two stages. Stage one: NIPAM gels results were compared with measurement results obtained using EBT3 dosimetry films. Both dosimeters were evaluated using an isodose curve and 2D gamma evaluation with the criteria of 3% dose and 3 mm DTA. The results obtained using the NIPAM gel dosimeter and films were highly consistent for the ≥70% dose region. However, the film measurements and treatment planning system-calculated distribution were different at the low-dose region (<70%). The gamma passing rate of the NIPAM gel was 96.969%, which was higher than that of the film (57.599%). Stage two: NIPAM gel dosimetry was investigated using dose–volume histograms (DVHs) and 3D gamma evaluation. The long-term stability of irradiated NIPAM gel dosimeter was also investigated. Results show that the gamma values exceeded 98% 12 h post-irradiation and the DVHs were consistent for the ≥30% dose region, which became evident through the NIPAM gel method. Gamma passing rates and DVH had no considerable changes two months post-irradiation, which indicated the high stability of NIPAM gels. NIPAM gel dosimetry with MRI successfully estimated the 3D dose distribution during clinical radiation treatment. Therefore, NIPAM gel can serve as a 3D tool for verification of dose distribution during clinical radiation treatment.

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CHANG, CINA-HSIN, and 張家鑫. "Evaluation of 3-D Polymer Gel Dosimeters of Ultrasound Computed Tomography and Dynamic Mechanical Analyzer on Ultrasonic Attenuation and Speed of Propagation and Storage Modulus." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/03395461407764639795.

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碩士
中臺科技大學
醫學影像暨放射科學系暨研究所
104
The sensitivity of polymer gel dosimeter is high in radiation detection, which will be polymerized or cross-linked under the radiation exposure. The new NIPAM polymer gel dosimeter changes in the ultrasonic echo signals at different radiation dose. Set ultrasonic measurement system device, for tuning and system integration, to find out the optimum operating frequency and parameters, calculation and correction of NIPAM polymer gel dosimeter attenuation coefficient.The storage modulus of DMA was 2.24X10-3 MPa in 0Gy, 3.22X10-3 MPa in 5Gy, 4.01X10-3 MPa in 10Gy, 5.86X10-3 MPa in 15Gy. The ultrasonic attenuation of UCT was 0.76dB in 0Gy,1.31 dB in 5Gy, 2.22 dB in 10Gy,3.4 dB in 15Gy. The ultrasonic speeds of gel dosimeters in UCT were 1786 m/s in 0Gy, 1754 m/s in 5Gy, 1717 m/s in 10Gy, 1675 m/s in 15Gy.

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Jarvi, Mark. "Evaluation of Photophysical Methods for Photodynamic Therapy Dosimetry." Thesis, 2012. http://hdl.handle.net/1807/32746.

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In photodynamic therapy (PDT), the combination of light, photosensitizer and molecular oxygen generates reactive oxygen species, including singlet oxygen (1O2), which is regarded as the primary cytotoxin and effector with most clinical photosensitizers. PDT has gained some acceptance for the treatment of cancer and other conditions. However, its clinical utility and effectiveness has been limited by variability in treatment response and failure to integrate adequate treatment planning and dosimetry. Direct PDT dosimetry through the detection of ultra-weak near-infrared 1O2 luminescence emission at 1270 nm (SOL) collapses the complexity of PDT into a single parameter, the 1O2 concentration. Prior to the present studies, it was shown that SOL was well correlated with PDT response in vitro and in vivo under controlled experimental conditions. However, SOL detection is technically challenging because of the very low radiative probability of 1O2 (~ 10-8 in biological environments), dynamic background signals and limited sensitivity of suitable photodetectors in this wavelength region. A technologically simpler and less costly PDT dosimetry approach is to use photosensitizer photobleaching to estimate the 1O2 dose. The first objective in this thesis was to characterize the dynamics of SOL measurements, in particular the influence of oxygen depletion, in order to improve the quantification of SOL and its use as an accurate PDT dose metric. Subsequently, direct comparison of SOL and photobleaching-based dosimetry during in vitro PDT treatment with meso-tetra(hydroxyphenyl)chlorin (mTHPC) showed that SOL dosimetry is robust but that photobleaching-based dosimetry can fail under hypoxic conditions. However, the latter can be salvaged through the identification of a previously unreported 613 nm emission from mTHPC that indicates hypoxia. These studies were carried forward into an in vivo dorsal skin-fold window chamber tumor model, which showed promising initial correlation between 1O2 dose and tumor response. This work also identified SOL detection limitations and opportunities for further development. Additionally, SOL measurements were used as a ‘gold standard’ to evaluate novel activatable PDT beacons and a novel “PDT biodosimeter” based on STAT3 cross-linking. Future work includes further tumor dose-response studies, characterization of novel photosensitizing agents, improvement on signal detection and processing, and studies in normal human skin.

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Reich, Paul D. "A theoretical evaluation of transmission dosimetry in 3D conformal radiotherapy." 2008. http://hdl.handle.net/2440/49483.

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Two-dimensional transmission dosimetry in radiotherapy has been discussed in the literature for some time as being a potential method for in vivo dosimetry. However, it still remains to become a wide spread practice in radiotherapy clinics. This is most likely due to the variety in radiotherapy treatment sites and the challenges they would present in terms of detection and interpretation at the transmitted dose level. Thus, the full potential and limitations of applying transmission dosimetry in the presence of dosimetry errors still need to be demonstrated. This thesis is a theoretical evaluation of transmission dosimetry using the Pinnacle3 treatment planning system. The accuracy of predicting reliable and accurate absolute transmitted dose maps using the planning system dose algorithm for comparison with measured transmitted dose maps was initially investigated. The resolution in the dose calculations at the transmitted level was then evaluated for rectilinear and curved homogeneous phantoms and rectilinear inhomogeneous phantoms, followed by studies combining both surface curvature and heterogeneities using anthropomorphic phantoms. In order to perform transmitted dose calculations at clinically relevant beam focus-to-transmitted dose plane distances using clinical patient CT data it was first necessary to extend the CT volume. Finally, the thesis explored the efficacy of applying transmission dosimetry in the clinic by simulating realistic dosimetry errors in the planning system using patient treatment plans for a prostate, head and neck, and breast CRT (Conformal Radiotherapy) treatment. Any differences at the transmitted dose level were interpreted and quantified using the gamma formalism. To determine whether the transmitted dose alone was a sufficient indicator of the dosimetry errors, the magnitude in transmission dose differences were compared with those predicted at the midplane of the patient. Dose-Volume Histograms (DVHs) were also used to evaluate the clinical significance of the dose delivery errors on the target volume and surrounding healthy tissue structures.
http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1339807
Thesis (Ph.D.) - University of Adelaide, School of Chemistry and Physics, 2008

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Chen, Liang-Cheng, and 陳亮丞. "Molecular Imaging, Pharmacokinetics, Dosimetry and Therapeutic Evaluation of 188Re Radiopharmaceuticals." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/70485769320022337140.

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博士
國立中興大學
獸醫學系暨研究所
105
Cancer is one of major leading death in the World and Taiwan. According to global health observatory data repository of WHO in 2014, the cancer is among the leading causes of morbidity and mortality worldwide. In this study, we focus on the radiopharmaceuticals for anti-cancer drug in colon cancer and liver cancer. First, the biodistribution, pharmacokinetics, dosimetry and comparative therapeutic efficacy of intravenously administrated 188Re-BMEDA-labeled pegylated liposome (188Re-liposome) and 5-FU were investigated in the colon cancer lung-metastatic model. After intravenous administration of the 188Re-liposome, tumor accumulation from the radioactivity was observed. Levels of radioactivity in tumors were maintained at steady levels (from 5.40 to 5.67%ID/g) after 4 h to 24 h. In pharmacokinetics, the AUC(o→∞), MRT(o→∞) and Cl of 188Re-liposome in blood via intravenous route were 998 h*%ID/mL, 28.7 h and 0.1 mL/h, respectively. The total excreted fractions of feces and urine were 0.61 and 0.26, respectively. Absorbed doses for 188Re-liposome in the liver and red marrow were 0.31 and 0.08 mSv/MBq, respectively. Tumor-absorbed doses for the 188Re-liposome ranged from 48.4 to 1.73 mGy/MBq at 10 to 300 g tumor spheres. In therapeutic efficacy, the survival times of mice after 188Re-liposome (80%MTD; 29.6 MBq), 5-FU (80%MTD; 144 mg/kg), liposome or normal saline treatments were evaluated. Consequently, radiotherapeutics of 188Re-liposome attained longer life span (increase 34.9%; P = 0.005) of mice than that of normal saline group. The increase in life span of 188Re-liposome group was 2.5-fold greater than that of the 5-FU group. Therefore, intravenous administration of 188Re-liposome could provide a benefit and it is a promising strategy for delivery of passive nanotargeted radiotherapeutics in oncology applications. Liver cancer is the second most common cause of death worldwide. This study was to investigate the SPECT/CT, ultrasound, biodistribution and therapeutic evaluation of 188Re-human serum albumin microspheres (188Re-HSAM) in the orthotopic hepatoma rat model. HSAM was labeled with 188Re by using home-made kit and microwave system. The 188Re-HSAM was administered via intraarterial route. The in vivo distribution of 188Re-HSAM was determined by biodistribution analysis and nanoSPECT/CT system. In efficacy, tumor volumes were tracked longitudinally by three-dimensional ultrasound. The biodistribution and nanoSPECT/CT imaging showed that 188Re-HSAM could accumulate in liver and tumor. The correlation coefficient of tumor volumes done by three-dimensional ultrasound and at autopsy was 0.997. In efficacy, tumor volume in the normal saline treated group was 1803.2 mm3 at 54 days after tumor inoculation. Tumor volumes in the 103.6 MBq and 240.5 MBq of 188Re-HSAM treated groups were 381 mm3 and 267.4 mm3 (P = 0.001 and 0.004), respectively. These results show that three-dimensional ultrasound with a high spatial resolution and contrast in soft tissue can become imaging modality in assessing tumor burden and tumor progression in orthotopic rat model. The longitudinally therapeutic evaluation of 188Re-HSAM demonstrated dose-dependent tumor growth inhibition with increased dose in the orthotopic hepatoma rat model.

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Kuo, Chia-wei, and 郭佳瑋. "Implementation of Laser Scanning System Applied on Dose Evaluation of Polymer Gel Dosimeter." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/5gp6hx.

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碩士
中臺科技大學
醫學工程暨材料研究所
96
Gel dosimeter is used to measure 3-Dimensional dose distribution. It can evaluate the treatment planning. In this study, in order to improve the accuracy of measurement, a laser scanning system was developed and was applied on the dose measurement of polymer gel dosimeter In this study, by using a He-Ne laser with wavelength 632.8 nm, attenuation coefficient of polymer gel can be calculated from the optical intensity measured by optical power meter. Three polymer gels was measured including SIGMA, WAKO, and DEMA. In addition, the measurement results were compared with that by MRI measurement. The conclusions can be described as follows: 1.A laser scanning system is well-established and the uncertainty of this system is less than 2.97 %. 2.For SIGMA gel, the best linear dose range is from 0 to 10 Gy. The linearity is 0.996 and the sensitivity is 0.0196. 3.For WAKO gel, the best linear dose range is from 0 to 10 Gy. The linearity is 0.996 and the sensitivity is 0.0288. 4.For DEMA gel, the best linear dose range is from 0 to 30 Gy. The linearity is 0.996 and the sensitivity is 0.001 5.From the results of MRI, for SIGMA gel, the best linear dose range is from 0 to 15 Gy. The linearity is 0.995 and the sensitivity is 0.1029. For WAKO gel, the best linear dose range is from 0 to 15 Gy. The linearity is 0.993 and the sensitivity is 0.1112. 6.The measurement results of each gel are similar by using various optical intensities.

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42

Chang, Yen-Lin, and 張雁翎. "Dose evaluation of Multi-Slice Computed Tomography for different parameters using thermoluminescent dosimeter method." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/rujv2b.

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碩士
元培科技大學
放射技術研究所
98
In radiodiagnosis, optimization is defined as a method of reducing the patient-absorbed doses without affecting image quality. In this study, we aimed to determine the parameters of a multi-slice CT (MSCT) scanner that ensure the least organ dose with the best image quality for chest examinations, which are the most frequently used radio diagnostic investigations. Organ doses of an anthropomorphic phantom were measured during MSCT chest scans by using GR-100 (TLDs) attached to various parts of the organs. The accumulated equivalent doses were calculated to evaluate the radiation risk to sensitive organs by using different scan conditions and measuring the absorbed doses, because different scan parameters (e.g., pitch, tube current, scan type, etc.) may affect the dose contribution to these organs. By means of the radiation and tissue weighting factors recommended in the ICRP 103 report, the effective dose was then estimated. When the pitch value was increased by 1.4 times, the effective dose decreased by 1.34 times was compared. The results revealed that the organ doses in the phantom reduced by 5.64 times when the tube current was reduced by 5 times in the low-dose chest examination, because of the lower tube current used for this protocol. Compared with fix mA, the effective dose was decreased 2.5 times in Smart mA. The pitch value and tube current were the main parameters affecting the organ doses of the phantom: increase in the pitch value and reduction of the tube current decreased the absorbed doses without impacting the image resolution and diagnostic information. Consequently, radiologists can establish an optimization protocol in MSCT and acquire high-resolution images with adequate diagnostic information while using the lowest exposure dose for examinations.

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Mac, Yi-Tan Chen, and 陳奕壇. "Evaluation of Magnetic Resonance Imaging Scanning for 3-Dimentional NIPAM gel dosimetry." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/55634260780156697309.

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碩士
中臺科技大學
放射科學研究所
98
Polymer gel dosimeters have high radiation sensitivity. The monomer component exposed to radiation, radiation induced polymerization and cross-linking reactions. As the result of this polymerization, the gel can be used as a dosimetric verification tool in clinics. But the performance of current polymer gel dosimeters were limited by the high toxicity and oxygen inhibition of the polymerization processes. The new less toxic monomer N-isopropyl acrylamide (NIPAM) was evaluated for use in new dosimeters and used as a dosimeter to obtain 3-D dose distribution. For future using in large volume radiotherapy like stereotactic surgery(SRS), brachytherapy(HDR), and total body irradiation(TBI), as an potential dosimeter. NIPAM gel dosimeter have been studied using Optical Computer Tomography (OCT) and have good linearity for the dose response from 0Gy to 5Gy. The polymer gel also revealed the characteristic of non-energy dependence, but very few studies on magnetic resonance imaging (MRI), through the field inhomogeneity problem effects the image. In this study, we used the Taguchi method for optimizing MRI parameter of the gel dosimeter. Through the new evaluated Gd jelly phantom for MRI imaging, we could solve the field inhomogeneity, and measured samples could be maximized to 1~17 tubes of NIPAM gel in the new phantom. Analyzing the images could obtain the relaxation rate(R2) for each exposed NIPAM gel, then finding the relation on the linearity of the gel. Through Taguchi method, we have indicated that the optimum combination of levels of the factors providing NIPAM gel with MRI were ：repetition time(TR), 3200ms; echo time(TE), 28 and 224 ms; phase encoding (Gph),128; and slice thickness, 3mm. The result shows a great increase in the linearity of 0.9984. By using the stabilized Gd jelly phantom, we could greatly solve the motion and instability problem, to find better linearity; we could then prove the higher stability of NIPAM gel. NIPAM gel is able to achieve high linearity with MRI by using the optimized parameters. With the Gd jelly is also able to solve the field inhomogeneity of the high Tesla MRI machines.

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Selemela, Letlhogonolo Patrick. "Spot evaluation of dosimetry compliance amongst diagnostic radiology staff in a medical facility." Thesis, 2018. https://hdl.handle.net/10539/25371.

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A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Medicine in Diagnostic Radiology (MMed Rad.D) Johannesburg, 2018.
INTRODUCTION It is important for radiation workers to wear a dosimeter while working in a radiology department as part of their daily practice. This is one of the requirements for radiation control set by the Department of Health (DoH). Dosimeters are used for monitoring the amount of radiation received by radiation workers while at work. AIM The aim of this study was to assess compliance with the wearing and correct placing of radiation dosimeters by radiation workers in four medical facilities. METHOD A prospective descriptive study was performed in the radiology departments of the Helen Joseph Hospital (HJH), Chris Hani Baragwanath Academic Hospital (CHBAH), Rahima Moosa Mother and Child Hospital (RHM), and Charlotte Maxeke Johannesburg Academic Hospital (CMJAH). Radiology staff workers were interviewed on an individual basis to determine whether they were wearing their dosimeter badge, and if so, whether they were wearing it in the correct manner. Unannounced spot checks and interviews were done on a random day. Data were collected in the general X-ray, computed-tomography (CT), fluoroscopy, and mammography units of each of the hospitals concerned. RESULTS Of the 85 participants, almost half (49.41%) did not have their dosimeter while working in their usual work environment. Of those who had their dosimeter on their person, 38% were wearing their dosimeter on either their collar or their chest pocket. In the sample, 25% of the consultant radiologists, 56% of the qualified radiographers, 41% of the radiology registrars and 83% of the radiographer students were wearing their dosimeter while at work. Sixty-seven per cent of the participants under the age of 32 were wearing their dosimeter, while only 30% of the participants between the ages of 33 and 65 had their dosimeter at work. 6 CONCLUSIONS As shown by this study, there was a low level of dosimeter compliance among senior radiographers and radiologists, and a non-existent level of compliance among nursing staff, working in the radiology departments concerned. The study highlighted a need for the introduction of targeted work-related educational and reinforcement programmes that would improve the knowledge and increase the awareness of radiation safety of all staff working in radiology departments.
LG2018

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Li, Yao-Ting, and 李曜廷. "Dose Evaluation of the NIPAM Gel Dosimetry by Cone Beam Optical CT Scanner." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/75246336600477005082.

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碩士
中臺科技大學
醫學影像暨放射科學系暨研究所
103
Recent years, cancer is a leading cause of deaths. Radiotherapy commonly used in cancer treatment. Radiotherapy treatment with verify dosimetry is even important. Polymer gel dosimeters have characteristics of three-dimensional(3D) dose distribution and and demands of clinic. Optical CT scanner have advantage of no radiation and fast, has been widely used in gel dosimeter dose measurement. Cone Beam Optical CT scanner (VISTA ™) has been often use in radiochromic gel dose measurement. In this study, we use N-isopropylacrylamide(NIPAM) polymer gel and cone beam optical CT scanner (CB Optical-CT) (Vista™) was applied to single field treatment plan. The dose distributions obtained from Vista scanner were compared with the calculated dose distribution generated by the treatment planning system (TPS). The results indicated, under 3%/3mm criteria, the pass rate could reach as high as 92%. Otherwise, gamma pass rate were 99% under 5% dose difference and 5 mm distance-to-agreement criteria. With dose verification, using EBT3, the pass rate was as high as 89% using 3%/3mm criteria. The present study demonstrated the feasibility of 3D dose verification using cone beam optical CT scanner Vista™ of NIPAM gel dosimeter. Furthermore, the results indicated that NIPAM gel dosimeter was stable and reliable. Hence, it is a potential 3D dosimeter in radiotherapy.

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Brock, Terry A. "The quantitative evaluation of radiological workplace indicators." Thesis, 2002. http://hdl.handle.net/1957/32484.

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Lu, Jia-Wen, and 呂嘉文. "Evaluation of The DeskCAT™ as Readout Tool for n-NIPAM Polymer Gel Dosimetry." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/21517279890200099390.

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碩士
中臺科技大學
醫學影像暨放射科學系暨研究所
103
Optical computed tomography (OCT) for 3D radiation dosimetry has many features in common with x-ray CT. In fact, optical CT scanner- DeskCAT™ was development for the purpose of teaching the principles of x-ray CT. Polymer gel dosimeters have high radiation sensitivity. The gel can be used as a dosimetric verification tool in clinics. This evaluation study is used DeskCAT™ as the readout tool of the n-NIPAM polymer gel dosimeter. The n-NIPAM was composed of 5% gelatin, 5% monomer, and 3% cross-linker and inserted with 5 mM THPC for deoxygenation. Dose responses of 6 Gy delivered by a linear accelerator were exarnined. In this study, use different scanning conditions to scanned and readout NIPAM dosimetry by DeskCAT™ . The dose profiles were found to be consistent at the depths of 5.0 cm to 7.0 cm for the gel phantom. The gamma pass rates highest were calculated to be 93.16±1.28 using 3% dose difference and 3 mm distance-to-agreement criterion. The DeskCAT™ could be used to demonstrate the principle of optical CT for teaching and if further investigated could be a potential optical readout device for gel dosimetry.

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Tutt, Teresa Elizabeth. "Experimental validation and evaluation of uncertainty in the monte carlo modeling of electron irradiation of complex objects." 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2560.

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Monte Carlo method is an invaluable tool in the field of radiation protection, used to calculate shielding effectiveness, as well as dose for medical applications. With few exceptions, most of the objects currently simulated have been homogeneous materials that vary in density by a factor of 3 or less. In the irradiation of very heterogeneous objects, particularly layered or leafy food items, one will encounter air pockets within the bundle as a matter of course. These pockets will cause variations in density of up to three orders of magnitude. Air pockets in a tissue equivalent phantom were found to produce “hot spots” in the dose distribution, and introduced significant deviations between the calculated and measured distribution of dose to the phantom. To date, very little published work had been done in the area of Monte-Carlo simulation of objects of such disparate density. Before Monte Carlo methods can be used successfully in this regime, further code development and experimental validation will be necessary, of which this work is just a beginning. Phantoms were made of corrugated low-Z material similar in electron density to plant based material. These phantoms incorporated air gaps of comparable size to those found in the leafy objects of interest. Dimensions were chosen to bracket electron ranges in the material of the objects modeled. Monte Carlo analysis will provide a reasonable qualitative picture of the dose distribution, but such a picture is not yet sufficiently accurate in a quantitative sense. Air gaps within the plant material produced large discrepancies between calculation and measurement. Smaller air gaps were observed to produce greater discrepancy between calculation and measurement.

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49

Sibbald, Regan Estcourt. "Evaluation of an amorphous silicon electronic portal imaging device for use in radiation therapy dosimetry." Thesis, 2005. http://hdl.handle.net/2429/16467.

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The objective of external beam radiation therapy is to deliver a high dose of sterilizing radiation to a diseased tumor site while minimizing the dose to as much of the surrounding normal tissue as possible. This is often accomplished by directing one or more megavoltage xray treatment portals at the diseased area from different directions. In theory, this principle maximizes the dose to the target site while minimizing the dose to surrounding healthy tissue. The efficacy of a course of radiation therapy may however be compromised by several factors. Geometric factors related to the accuracy to which the beam delivery system can reproduce the desired treatment set-up may cause deviations from the desired results. Patient set-up uncertainties are another factor and are related to the alignment of skin markings with respect to the underlying target structures within the body. In addition, a presumably fixed target may be geometrically shifted due to its proximity to neighboring organs or the patient may simply move during treatment thereby shifting the treatment portal with respect to the intended target. All of these factors contribute to a sub-optimal treatment outcome and possibly an increase in the normal tissue complication probability (NTCP). On-line electronic portal imaging devices (EPIDs) have been developed to monitor and help correct the inaccuracies encountered in radiation therapy. EPIDs were developed for verification of geometric accuracy, as they are capable of producing near real-time 2D projection images of the target volume during a radiotherapy treatment. However, it has also become apparent that in addition to geometric verification, EPIDs can provide valuable dosimetric information, indicating points of interest in terms of over and under dosage. In this thesis, the dosimetric characteristics of the amorphous silicon EPID are investigated. First, the EPIDs ability to accurately and reproducibly measure dose as a function of fluence rate is investigated. EPID pixel intensity values were found to vary by up to ±3% from the average value with a standard deviation of 1.3% when measuring the same dose with varying dose rates for both 6 and 18 MV photons. Next the water equivalent depth of the inherent buildup material on the EPID is determined. The inherent build-up of the portal imaging device was found to be 1.4 ± 0.2 cm for 6 MV and 2.2 ± 0.2 cm for 18 MV. A comparison of EPID and film images acquired during enhanced dynamic wedge treatments indicated that the film profiles show an increased response of film compared to the EPID as the distance from the central axis increases. The EPIDS dose response curve was characterized by comparing ion chamber measurements to EPID pixel intensity values. The dose response dependence on incident photon energy and fluence rate was also investigated. The ratio of dose to total pixel value was found to be to be 1.42 x 10⁻⁴ cGy/pix for 18 M V and 1.44 x 10⁻⁴ cGy/pix for 6 M V with confidence intervals of 0.05 x 10⁻⁴ cGy/pix. Dose measurements were found to be reproducible with a standard deviation of 1.3% for both 6 and 18 M V photons. All calibration equations were verified over the dose range of 10 cGy to 100 cGy.
Science, Faculty of
Physics and Astronomy, Department of
Graduate

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LI, HUI-JU, and 李蕙如. "An Evaluation of Entrance Surface Dose in Clinical Application of Special Radiography with the use of Optical Stimulated Luminescence Dosimeter." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/59525051290117267207.

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碩士
元培醫事科技大學
醫學影像暨放射技術系碩士班
104
Fluoroscopy, also known as the special graphy, is becoming more common in clinical use. Despite the fact that radiation dose from medical imaging is not considered for the measurement of annual dose limitation, it is possible that the future risks of medical imaging for unfit indications, repetitive examinations for the same indications, or other available medical imaging might outweigh the benefit from the examinations. In other words, optimization of radiation dose for medical imaging means that radiation exposures to patients should be reduced to levels that are as low as reasonably achievable (ALARA) without compromising the diagnostic value of the examination. Therefore, this research aims to study radiation safety in special radiography by evaluating entrance surface dose (ESD) of optical stimulated luminescence dosimeter (OSLD) in clinical application of special radiography. The study used the three imaging exams that were conducted the most times at Radiology Department from April-June 2015 as the dose assessment standard and relative position of organs for the distribution measurement of entrance surface dose (ESD). Optical Stimulated Luminescence Dosimeter (OSLD) infused with Aluminum oxide (Al2O3) was placed on the phantom surface, field and field within. Cumulative dose of fluoroscopy and routine exposure, which were both conducted for three times, was recorded. The examinations conducted were double-contrast barium enema, upper GI series, which uses a combination of air and barium to create a more detailed view of the stomach lining, and esophagography, which also known as barium swallow. The result of the research showed that, field within and field, dose measurements of ESD for double-contrast barium enema were 9.50 mSv and 0.72 mSv, 2.46 mSv and 0.68 mSv for upper GI series and 1.21 mSv and 0.67 mSv for esophagography, radiation dose was higher in double-contrast barium enema which had the most imaging conditions and longer fluoroscopy duration. Evaluation of ESD is mainly associated with fluoroscopy time, imaging conditions, complexity of the lesion, and technical skills of the instructor. The average fluoroscopy time of the maximum ESD in this study was 437 s. It is suggested that radiation exposure to patients should be minimized without compromising the diagnostic quality in order to achieve ALARA.

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