Dissertations / Theses: 'Medical imaging : Medical physics'

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Rolland, Jannick Paule Yvette. "Factors influencing lesion detection in medical imaging." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185096.

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An important goal in medical imaging is the assessment of image quality in a way that relates to clinical efficacy. An objective approach is to evaluate the performance of diagnosis for specific tasks, using ROC analysis. We shall concentrate here on classification tasks. While many factors may confine the performance achieved for these tasks, we shall investigate two main limiting factors: image blurring and object variability. Psychophysical studies followed by ROC analysis are widely used for system assessment, but it is of great practical interest to be able to predict the outcome of psychophysical studies, especially for system design and optimization. The ideal observer is often chosen as a standard of comparison for the human observer since, at least for simple tasks, its performance can be readily calculated using statistical decision theory. We already know, however, of cases reported in the literature where the human observer performs far below ideal, and one of the purposes of this dissertation is to determine whether there are other practical circumstances where human and ideal performances diverge. Moreover, when the complexity of the task increases, the ideal observer becomes quickly intractable, and other observers such as the Hotelling and the nonprewhitening (npw) ideal observers may be considered instead. A practical problem where our intuition tells us that the ideal observer may fail to predict human performance occurs with imaging devices that are characterized by a PSF having long spatial tails. The investigation of the impact of long-tailed PSFs on detection is of great interest since they are commonly encountered in medical imaging and even more generally in image science. We shall show that the ideal observer is a poor predictor of human performance for a simple two-hypothesis detection task and that linear filtering of the images does indeed help the human observer. Another practical problem of considerable interest is the effect of background nonuniformity on detectability since, it is one more step towards assessing image quality for real clinical images. When the background is known exactly (BKE), the Hotelling and the npw ideal observers predict that detection is optimal for an infinite aperture; a spatially varying background (SVB) results in an optimum aperture size. Moreover, given a fixed aperture size and a BKE, an increase in exposure time is highly beneficial for both observers. For SVB, on the other hand, the Hotelling observer benefits from an increases in exposure time, while the npw ideal observer quickly saturates. In terms of human performance, results show a good agreement with the Hotelling-observer predictions, while the performance disagrees strongly with the npw ideal observer.

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Pellegrini, Giulio. "Technology development of 3D detectors for high energy physics and medical imaging." Thesis, University of Glasgow, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269510.

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Badawi, Ramsey Derek. "Aspects of optimisation and qualification in 3D positron emission tomography." Thesis, King's College London (University of London), 1998. https://kclpure.kcl.ac.uk/portal/en/theses/aspects-of-optimisation-and-qualification-in-3d-positron-emission-tomography(47a88023-9d6c-453f-aa8d-fcc5b83ae168).html.

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Yao, Zhen. "OPTIMIZING RF AND GRADIENT COILS IN MRI." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1402058570.

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Alarady, Mamdooh R. "Characterization of Image Quality between Multi-Slice Computed Tomography and Cone Beam Computed Tomography for Clinical Used Protocols in Radiation Therapy Treatment Planning." University of Toledo Health Science Campus / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=mco151080400269082.

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Khan, Zein A. "Medical imaging using the acousto-electromagnetic technique." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:017c096e-c2fc-462a-9266-2b8731ff31b3.

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Greer, Peter Brian. "A dual assembly multileaf collimator for radiotherapy." Title page, table of contents and abstract only, 2000. http://web4.library.adelaide.edu.au/theses/09PH/09phg81659.pdf.

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Bibliography: leaves 241-250. A multileaf collimator for radiation therapy has been designed that splits each leaf bank into two vertically displaced assemblies or levels with each level consisting of alternate leaves and leaf spaces. The radiation profiles transmitted for image formation through the collimator design were investigated to examine their dependence on the collimator design features.

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Liang, Chen. "Design of miniature microscope objective optics for biomedical imaging." Diss., The University of Arizona, 2002. http://hdl.handle.net/10150/280105.

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The topic of this dissertation is on the design and construction of miniature microscope objective optics. The design of miniature microscope objective is both similar and different from conventional microscope objective. The design and construction of two miniature microscope objectives are presented in this dissertation. The first one is a high numerical aperture (NA), water-immersion objective and it is a part of a fiber confocal reflectance microscope (FCRM). The second one is a moderate NA dry objective and it is a part of a miniature microscope array (MMA). The capability, complexity and fabrication method of the two miniature objectives are different but they both share some similar design traits as result of their miniaturization. FCRM's miniature objective has a NA of 1.0 and it is designed to operate at near infrared lambda = 1,064 nm. It is 7 mm in outer diameter and 21 mm in length (measured from object plane to image plane). This kind of dimension is approximately 10 times smaller than a conventional microscope objective of similar caliber. Sub-micrometer resolution has been experimentally demonstrated with this miniature objective. MMA's miniature objective has a NA of 0.4 and it is designed to operate over the visible spectrum. It is 1.2 mm in diameter and 9.4 mm in length. The image quality of MMA's miniature objective is experimentally demonstrated to be comparable to the state-of-art commercial microscope objective.

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Lee, Junwon. "The development of a miniature imaging system: Design, fabrication and metrology." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/289892.

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The topic of dissertation is on the development of a miniature imaging device named as multi-modal miniature microscope [a.k.a. 4M Device]. Generally speaking, the development of an optical imaging device involves three main processes: optical design, fabrication and metrology. They are interdependent and often comprise a feedback loop. This dissertation will address these three processes sequentially. The 4M device is miniature compound microscope consisting of miniature optics, electronic imaging device, and mechanical device. Every component is integrated on single silicon substrate. The main purpose of 4M device is to provide an imaging capability for the detection of pre-cancer without biopsy. It uses a novel optics called hybrid lens that is fabricated by using a grayscale photomask and photolithographic technique. The hybrid lens is made of sot-gel material and glass substrate. It has 1.2mm of diameter and its surface is conic. Given lens design constraints from the fabrication, the series of lens design for 4M device are implemented and presented. Each design delivers diffraction-limited imaging performance with N.A ranging from 0.4 to 0.7. The 4M device that is currently built has 0.4 of N.A. The imaging quality assessments of 4M device are also implemented in quantitative and qualitative ways. There are two instruments for imaging quality assessment: Multi-modal imaging testbed for entire imaging device and Shack-Hartmann wavefront sensor for individual element. The qualitative assessment includes multi-modal imaging experiments under different illumination modes. The object is a cervical cancer cell prepared by Dr. Kortum's Group at Univ. of Texas at Austin. The qualitative assessment includes the surface characterization and wavefront measurement of individual optics and the MTF measurement of entire device. The results of imaging quality assessment show the potential of 4M device for medical imaging device. They also explain the degradation of imaging quality.

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Brown, Oliver. "Novel dissymmetric copper bis(thiosemicarbazone) complexes for medical diagnostic imaging by positron emission tomography." Thesis, University of Kent, 2015. https://kar.kent.ac.uk/53590/.

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Bis(thiosemicarbazone) ligand derivatives and their metal complexes have long been of interest as they have applications as anticonvulsants, super-oxide dismutase-like radical scavengers, in the investigation of Alzheimer’s disease and diagnostic imaging. Copper (II) bis(thiosemicarbazone) derivatives have been used extensively in the imaging of oxygen deficient (hypoxic) cells for the detection and imaging of cancerous tissues and heart disease via Positron Emission Tomography (PET). It is possible to fine tune the bis(thiosemicarbazone) complexes redox potentials and lipophilicity by altering the substituents on the Q1 and Q2 position and the R1, R2, R3 and R4 locations respectively. To date only symmetric bis(thiosemicarbazone) ligands (R1=R3, R2=R4) have been evaluated for hypoxia imaging. This thesis reports the synthesis of dissymmetric ligands (R1≠R3, R2≠R4) in order to gain further control of the properties of the complexes and therefore the locations they will migrate to. A range of ligands has also been synthesised for the monitoring of copper metabolism within the brain for the investigation of Alzheimer’s disease and other neurodegenerative disorders. Ligand synthesis has been achieved by controlling the condensation reactions between dicarbonyl compounds and 4-substituted-3-thiosemicarbazides. Synthesis via an alternative acetal protecting method has also been investigated. Thirty bis(thiosemicarbazone) ligands have been successfully synthesised, of which thirteen are symmetric and seventeen dissymmetric. From this library of ligands, eighteen copper complexes have been synthesised along with twenty zinc complexes. The zinc complexes have the potential to act as convenient precursors for the rapid synthesis of radio-copper complexes via a transmetalation method. All ligands, complexes and intermediates have been fully characterised by a range of techniques including IR spectroscopy, Raman spectroscopy, NMR spectroscopy, UV-vis spectroscopy, elemental analysis and mass spectroscopy. A new cyclic by-product from the ligand synthesis has also been isolated and fully characterised.

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Gill, Sukhdeep Kaur. "A Study of Evaluation of Optimal PTV Margins for Patients Receiving Prostate IGRT based on CBCT Data Dose Calculation." University of Toledo Health Science Campus / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=mco1404732511.

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Volin, Curtis Earl. "Portable snapshot infrared imaging spectrometer." Diss., The University of Arizona, 2000. http://hdl.handle.net/10150/289203.

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A practical, field-capable, 3.0 to 5.0 μm mid-wave infrared Computed-Tomography Imaging Spectrometer (CTIS) has been demonstrated. The CTIS employs a simple optical system in order to measure the object cube without any scanning . The data is not measured directly, but in a manner which requires complicated post-processing to extract an estimate of the object's spectral radiance. The advantage of a snapshot imaging spectrometer is that it can collect information about a dynamic event which a standard scanning spectrometer could either miss or corrupt with temporal artifacts. Results were presented for reconstructions of laboratory targets with sampling up to 46 x 46 x 21 voxels over a variable field-of-view, or 0.1 μm spectral sampling. Demonstration of the snapshot capability has been performed on both static targets and targets with rapidly varying content. The contents of this dissertation are directed towards two ends. The primary undertaking is a realization of the theoretical model of the CTIS is a practical, field-capable MWIR instrument. The design, calibration, and operation of the MWIR CTIS are explained in detail in the text and appendices. Of additional interest is the advancement of the theory to improve the design and functionality of the spectrometer. A new algorithm for design of the holographic disperser component of the CTIS is introduced. The design process dramatically extends the set of possibilities for the disperser. In order to improve the reconstruction potential of the spectrometer, the analytic expressions which describe the CTIS have been expanded into a principal component basis set. The result is a technique for creating an initial estimate of the object and a technique for improving the reconstruction algorithm.

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Kalita, Spartak A. "Transfer of students' learning about x-rays and computer-assisted tomography from physics to medical imaging." Diss., Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/1052.

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Meakin, James A. "Velocity selective preparations in Magnetic Resonance Imaging." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:a4247c64-d113-42e6-beee-5795e78a4cdc.

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Arterial Spin Labeling (ASL) is a Magnetic Resonance Imaging (MRI) technique that is able to non-invasively quantify the rate of delivery of arterial blood to tissue, known as perfusion. In this thesis a method that uses Velocity Selective (VS) preparations to generate contrast between blood and tissue spins is investigated. The systematic errors associated with performing a VSASL experiment on imperfect hardware is first investigated. It is shown through simulations and experiments that some VS preparations will underestimate perfusion due to static and transmit magnetic field errors, and that eddy currents caused by switching of magnetic gradients lead to an overestimation of perfusion with VSASL by up to a factor 2. A novel VS preparation, BIR-8, is presented which is shown to be the most robust to these imperfections. The BIR-8 VSASL technique is then applied in brain tumours where it is found that significant VSASL signal can be detected in less than 5 minutes. However, in a comparison with a spatially selective ASL technique it is found that VSASL overestimates perfusion in these tumours, despite agreeing in Grey Matter. The systematic errors due to physiology are then modelled, and it is shown that both diffusion and bulk motion will systematically bias the VSASL measurement. A diffusion insensitive VSASL technique, VS-TILT, is then developed and it is found that a significant proportion of the VSASL signal originates from diffusion effects. Theoretical models for the shape of the bolus in vascular networks are also derived, and it is shown that an isotropic network of laminar vessels produces the most efficient saturation, but saturation is also achieved with plug flow. The diffusion insensitive VS preparation is then applied in an attempt to isolate the venous compartment in order to measure Oxygen Extraction Fraction. A kinetic model is derived in order to optimise the acquisition. However, it is found that accurate measurements of OEF would not be produced by this sequence in a clinically realistic time.

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Marais, Johan. "An investigation into the limitations of myocardial perfusion imaging." Thesis, University of Northampton, 2012. http://nectar.northampton.ac.uk/8874/.

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Müller, Bernhard. "Medical imaging with a laser-driven undulator x-ray source." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-167164.

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Vaidya, Manushka. "Steering Electromagnetic Fields in MRI| Investigating Radiofrequency Field Interactions with Endogenous and External Dielectric Materials for Improved Coil Performance at High Field." Thesis, New York University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10261392.

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Although 1.5 and 3 Tesla (T) magnetic resonance (MR) systems remain the clinical standard, the number of 7 T MR systems has increased over the past decade because of the promise of higher signal-to-noise ratio (SNR), which can translate to images with higher resolution, improved image quality and faster acquisition times. However, there are a number of technical challenges that have prevented exploiting the full potential of ultra-high field (≥ 7 T) MR imaging (MRI), such as the inhomogeneous distribution of the radiofrequency (RF) electromagnetic field and specific energy absorption rate (SAR), which can compromise image quality and patient safety.

To better understand the origin of these issues, we first investigated the dependence of the spatial distribution of the magnetic field associated with a surface RF coil on the operating frequency and electrical properties of the sample. Our results demonstrated that the asymmetries between the transmit (B₁⁺) and receive (B₁^–) circularly polarized components of the magnetic field, which are in part responsible for RF inhomogeneity, depend on the electric conductivity of the sample. On the other hand, when sample conductivity is low, a high relative permittivity can result in an inhomogeneous RF field distribution, due to significant constructive and destructive interference patterns between forward and reflected propagating magnetic field within the sample.

We then investigated the use of high permittivity materials (HPMs) as a method to alter the field distribution and improve transmit and receive coil performance in MRI. We showed that HPM placed at a distance from an RF loop coil can passively shape the field within the sample. Our results showed improvement in transmit and receive sensitivity overlap, extension of coil field-of-view, and enhancement in transmit/receive efficiency. We demonstrated the utility of this concept by employing HPM to improve performance of an existing commercial head coil for the inferior regions of the brain, where the specific coil’s imaging efficiency was inherently poor. Results showed a gain in SNR, while the maximum local and head SAR values remained below the prescribed limits. We showed that increasing coil performance with HPM could improve detection of functional MR activation during a motor-based task for whole brain fMRI.

Finally, to gain an intuitive understanding of how HPM improves coil performance, we investigated how HPM separately affects signal and noise sensitivity to improve SNR. For this purpose, we employed a theoretical model based on dyadic Green’s functions to compare the characteristics of current patterns, i.e. the optimal spatial distribution of coil conductors, that would either maximize SNR (ideal current patterns), maximize signal reception (signal-only optimal current patterns), or minimize sample noise (dark mode current patterns). Our results demonstrated that the presence of a lossless HPM changed the relative balance of signal-only optimal and dark mode current patterns. For a given relative permittivity, increasing the thickness of the HPM altered the magnitude of the currents required to optimize signal sensitivity at the voxel of interest as well as decreased the net electric field in the sample, which is associated, via reciprocity, to the noise received from the sample. Our results also suggested that signal-only current patterns could be used to identify HPM configurations that lead to high SNR gain for RF coil arrays. We anticipate that physical insights from this work could be utilized to build the next generation of high performing RF coils integrated with HPM.

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Sirois, Luc M. "3-D automatic anatomy-based image registration in portal imaging." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0025/MQ50880.pdf.

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Sarfehnia, Arman. "The use of orthogonal bremsstrahlung beams for imaging in radiation therapy /." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99203.

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Since portal images are created by megavoltage, forward-directed bremsstrahlung beams, their image quality is inferior to that of images produced by kilovoltage beams. In this study, characteristics of orthogonal bremsstrahlung photons produced by megavoltage electron beams were studied and their suitability for radiotherapy imaging was evaluated. Orthogonal bremsstrahlung beams with kilovoltage effective energies can be obtained from megavoltage electrons striking low atomic number targets. A 10 MeV electron beam emerging out of the research port of a Varian Clinac-18 linac was made to strike carbon, aluminum and copper targets. Percentage depth dose and attenuation measurements of forward and orthogonal beams were performed, and experimental results were compared with Monte Carlo-calculated findings. Images of simple contrast objects taken using the orthogonal bremsstrahlung beams showed superior contrast levels in comparison to those produced by the forward beams.

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Eck, Brendan Lee. "Myocardial Perfusion Imaging with X-Ray Computed Tomography." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1525187076597075.

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Conill, Annette L. "Dosimetric consequences of the parotid glands using CT-to-CBCT deformable registration during IMRT for late stage head and neck cancers." Thesis, Florida Atlantic University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10154925.

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Patients receiving Intensity Modulated Radiation Therapy (IMRT) for late stage head and neck (HN) cancer often experience anatomical changes due to weight loss, tumor regression, and positional changes of normal anatomy (1). As a result, the actual dose delivered may vary from the original treatment plan. The purpose of this study was (a) to evaluate the dosimetric consequences of the parotid glands during the course of treatment, and (b) to determine if there would be an optimal timeframe for replanning. Nineteen locally advanced HN cancer patients underwent definitive IMRT. Each patient received an initial computerized tomography simulation (CT-SIM) scan and weekly cone beam computerized tomography (CBCT) scans. A Deformable Image Registration (DIR) was performed between the CT-SIM and CBCT of the parotid glands and Planning Target Volumes (PTVs) using the Eclipse treatment planning system (TPS) and the Velocity deformation software. A recalculation of the dose was performed on the weekly CBCTs using the original monitor units. The parameters for evaluation of our method were: the changes in volume of the PTVs and parotid glands, the dose coverage of the PTVs, the lateral displacement in the Center of Mass (COM), the mean dose, and Normal Tissue Complication Probability (NTCP) of the parotid glands. The studies showed a reduction of the volume in the PTVs and parotids, a medial displacement in COM, and alterations of the mean dose to the parotid glands as compared to the initial plans. Differences were observed for the dose volume coverage of the PTVs and NTCP of the parotid gland values between the initial plan and our proposed method utilizing deformable registration-based dose calculations.

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Snell, Rodney James 1965. "A digital-electronic video-rate reconstruction system for magnetic resonance imaging." Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/278071.

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A digital-electronic video-rate reconstruction system for Magnetic Resonance Imaging (MRI) has been designed to first order. The maturation of ultra-fast acquisition techniques in MRI has produced the need for a reconstruction system that will enable dynamic processes to be viewed on-line. Conventional reconstruction hardware is not configured for real-time reconstruction and previous developments are limited in accuracy and flexibility. The real-time reconstruction system presented here consists of three main subsystems. A digitizer interfaces with an MR scanner to digitize data matrices of resolutions up to 256 x 256 at arbitrary rates up to video rates. A Fourier processor performs either 2D Fourier transformation or projection filtering on the digitized data at video-rates. A backprojector performs the backprojection operation on filtered-projection data at video-rates. The complete system would be able to reconstruct data acquired from nearly any acquisition technique. True real-time MRI is then possible.

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Hoffman, David. "Hybrid PET/MRI Nanoparticle Development and Multi-Modal Imaging." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/3253.

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The development of hybrid PET/MRI imaging systems needs to be paralleled with the development of a hybrid intrinsic PET/MRI probes. The aim of this work was to develop and validate a novel radio-superparamagnetic nanoparticle (r-SPNP) for hybrid PET/MRI imaging. This was achieved with the synthesis of superparamagnetic iron oxide nanoparticles (SPIONs) that intrinsically incorporated 59Fe and manganese iron oxide nanoparticles (MIONs) that intrinsically incorporated 52Mn. Both [59Fe]-SPIONs and [52Mn]-MIONs were produced through thermal decomposition synthesis. The physiochemical characteristics of the r-SPNPs were assessed with TEM, DLS, and zeta-potential measurements, as well as in imaging phantom studies. The [59Fe]-SPIONs were evaluated in vivo with biodistribution and MR imaging studies. The biodistrubution studies of [59Fe]-SPIONs showed uptake in the liver. This corresponded with major MR signal contrast measured in the liver. 52Mn was produced on natural chromium through the 52Cr(p,n)52Mn reaction. The manganese radionuclides were separated from the target material through a liquid-liquid extraction. The αVβ3 integrin binding of [52Mn]-MION-cRGDs was evaluated with αVβ3 integrin solid phase assays, and the expression of αVβ3 integrin in U87MG xenograft tumors was characterized with fluorescence flow cytometry. [52Mn]-MION-cRGDs were used for in vivo PET and MR imaging of U87MG xenograft tumor bearing mice. PET data showed increased [52Mn]-MION-cRGD uptake compared with untargeted [52Mn]-MIONs. ROI analysis of PET and MRI data showed that MR contrasted corresponded with PET signal. Future work will utilize [52Mn]-MION-cRGDs in other tumor models and with hybrid PET/MRI imaging systems.

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Aldawood, Saad [Verfasser], and Peter [Akademischer Betreuer] Thirolf. "Commissioning of a Compton camera for medical imaging / Saad Aldawood ; Betreuer: Peter Thirolf." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2017. http://d-nb.info/1124395784/34.

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Kang, Jun. "Thin film CdTe as high energy x-ray detector material for medical applications." Connect to full text in OhioLINK ETD Center, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1228060515.

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Noshirvani, Allahabadi Golchehr, and Allahabadi Golchehr Noshirvani. "Bessel Light Sheet Structured Illumination Microscopy." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621810.

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Biomedical study researchers using animals to model disease and treatment need fast, deep, noninvasive, and inexpensive multi-channel imaging methods. Traditional fluorescence microscopy meets those criteria to an extent. Specifically, two-photon and confocal microscopy, the two most commonly used methods, are limited in penetration depth, cost, resolution, and field of view. In addition, two-photon microscopy has limited ability in multi-channel imaging. Light sheet microscopy, a fast developing 3D fluorescence imaging method, offers attractive advantages over traditional two-photon and confocal microscopy. Light sheet microscopy is much more applicable for in vivo 3D time-lapsed imaging, owing to its selective illumination of tissue layer, superior speed, low light exposure, high penetration depth, and low levels of photobleaching. However, standard light sheet microscopy using Gaussian beam excitation has two main disadvantages: 1) the field of view (FOV) of light sheet microscopy is limited by the depth of focus of the Gaussian beam. 2) Light-sheet images can be degraded by scattering, which limits the penetration of the excitation beam and blurs emission images in deep tissue layers. While two-sided sheet illumination, which doubles the field of view by illuminating the sample from opposite sides, offers a potential solution, the technique adds complexity and cost to the imaging system. We investigate a new technique to address these limitations: Bessel light sheet microscopy in combination with incoherent nonlinear Structured Illumination Microscopy (SIM). Results demonstrate that, at visible wavelengths, Bessel excitation penetrates up to 250 microns deep in the scattering media with single-side illumination. Bessel light sheet microscope achieves confocal level resolution at a lateral resolution of 0.3 micron and an axial resolution of 1 micron. Incoherent nonlinear SIM further reduces the diffused background in Bessel light sheet images, resulting in confocal quality images in thick tissue. The technique was applied to live transgenic zebra fish tg(kdrl:GFP), and the sub-cellular structure of fish vasculature genetically labeled with GFP was captured in 3D. The superior speed of the microscope enables us to acquire signal from 200 layers of a thick sample in 4 minutes. The compact microscope uses exclusively off-the-shelf components and offers a low-cost imaging solution for studying small animal models or tissue samples.

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Youniss, Fatma. "MULTI – MODALITY MOLECULAR IMAGING OF ADOPTIVE IMMUNE CELL THERAPY IN BREAST CANCER." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3323.

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Cancer treatment by adoptive immune cell therapy (AIT) is a form of immunotherapy that relies on the in vitro activation and/or expansion of immune cells. In this approach, immune cells, particularly CD8+ T lymphocytes, can potentially be harvested from a tumor-bearing patient, then activated and/or expanded in vitro in the presence of cytokines and other growth factors, and then transferred back into the same patient to induce tumor regression. AIT allows the in vitro generation and activation of T-lymphocytes away from the immunosuppressive tumor microenvironment, thereby providing optimum conditions for potent anti-tumor activity. The overall objective of this study is to: a) develop multi-modality (optical- and radionuclide-based) molecular imaging approaches to study the overall kinetics of labeled adoptively transferred T- lymphocytes in vivo, b) to non-invasively image and assess in-vivo, targeting and retention of adoptively transferred labeled T-lymphocytes at the tumor site. T-lymphocytes obtained from draining lymph nodes of 4T1 (murine breast cancer cell) sensitized BALB/C mice were activated in vitro with Bryostatin/ Ionomycin for 18 hours, and were grown in either Interleukin-2 (IL-2) or combination of Interleukin-7 and Interleukin-15 (IL-7/IL-15) for 13 days, (cells grown in IL-2 called IL2 cells, and cells grown in IL7/15 called IL7/15 cells). In order to validate the methodology and to offer future clinical translation, both direct and indirect cell labeling methods were expanded and employed. The first method was based on direct in vitro cell labeling by lipophilic near-infrared (NIR) fluorescent probe, 1,1- dioctadecyltetramethyl indotricarbocyanine iodide, (DiR), followed by intravenous (i.v.) injection into BALB/C mice for multi-spectral fluorescence imaging (MSFI). The second method was based on indirect labeling of T- lymphocytes through transduction of a reporter gene (cell cytoplasm labeling Herpes Simplex Virus type 1- thymidine kinase (HSV-1 tk). The product of this reporter gene is an enzyme (HSV-1TK) which phosphorylates a radio labeled substrate 2-fluoro-2-deoxy-1 β- D- arabinofuranosyl-5-iodouracil ([124I]-FIAU) for Positron Emission tomography (PET) imaging. ATP based cell viability assay, flow cytometry and interferon-γ (IFN-γ) ELISA were used to investigate if there are any changes in cell viability, proliferation and function respectively, before and after direct and indirect labeling. The results showed that cell viability, proliferation, and function of labeled 4T1 specific T-lymphocytes were not affected by labeling for direct labeling methods at DiR concentration of 320µg/ml. For the indirect labeling method, the viability and proliferation results showed that cell viability decreases as multiplicity of infectious (MOI) increases. In particular, at MOI of 10 almost all cells die 3 days post transduction. At MOI of 5, cells viability was ≤ 30% and at MOI of 2 was ≤ 60%. Cell viability was 80% at MOI of 1. The results of optical imaging were as follows: when the recipient mice with established 4T1 tumors were injected with DiR labeled 4T1 specific T-lymphocytes, the 4T1 specific T-lymphocytes (IL2 cells) infused into tumor-bearing mice showed high tumor retention, which peaked 3 or 6 days post infusion depending on the tumor size and persisted at the tumor site for 3 weeks. In contrast, IL7/15 cells showed lower signal at the tumor site and this peaked on day 8. On the other case when 4T1 tumor cells were implanted 1-week post-infusion of labeled T-lymphocytes. IL2 T-lymphocytes moved out of lymphoid compartments to the site of subsequent 4T1 inoculation within two hours and peaked on day 3 and the signal persisted for 2 more weeks. In contrast with infusion of IL7/15 cells, the signal was barely detected and did not show a similar trafficking pattern as with IL2 cells. The results of the indirect labeling method, PET reporter gene (PRG) system (HSV-1tk / [124I ] FIAU ) showed that both IL2 and IL7/15 cells were successfully transduced as verified ex vivo by real time PCR and western blot. T Cells transduction efficiency was assessed from cell uptake study in comparison to stable transduced Jurkat cells which have transduction efficiency of 100 %. Both IL2 and IL7/15 cells showed lower transduction efficiency (≤ 30%) compared to Jurkat cells. Consequently, PET imaging did not show a detectable signal of transduced T cells in vivo. Biodistribution study was carried out on day 3 post [124I]-FIAU injections. Results were consistent with the optical imaging results, except for IL7/15 cells. Transduced and untransduced IL2 and IL7/15 cells were labeled with DiR and injected ( i.v.) into Balb / C mice and then imaged by both imaging modalities (MSFI and PET) at the same time. MSFI images of transduced IL2 cell showed detectable signal starting from 2 hours, peaked at 72 hours and persisted up to 2 weeks, while IL7/15 cells were detectable at the tumor site starting at 24 hours, peaked at 72 hours and persisted up to 2 weeks. By the end of this study animals were dissected and tissue activities were counted using gamma counting and expressed as % Injected dose/gram of tissue (%ID/gm). Transduced IL2 and IL7/15 cells showed higher %ID/gm than other organs at lungs, liver, spleen, tumor, lymph nodes and bone/bone marrow. IL7/15 cells compared to IL2 cells showed higher %ID/gm at same organs. Neither IL2 nor IL7/15 untransduced DiR labeled cells showed any activity at tumor site, and their activities at other organs was very low compared to transduced cells. To investigate whether labeled T-lymphocytes will localize at tumor metastases or not, and to study the difference in their migration patterns to the tumor site versus tumor metastases, 4T1 tumor cells were successfully transduced with HSV-1tk as confirmed by RT-PCR , western blot and cell uptake study. Transduced 4T1 cells were implanted in the right flank or in the mammary fat pad of the mouse. Serial PET imaging was carried out in the third and fourth week post tumor implantation to know when the tumor will metastasizes. PET imaging showed only signal at the tumor site and no metastasis were detected.

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28

Brümmer, Theresa [Verfasser], and Florian [Akademischer Betreuer] Grüner. "Design Study of a Laser-Driven X-ray Source for Medical Fluorescence Imaging / Theresa Brümmer ; Betreuer: Florian Grüner." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2018. http://d-nb.info/1160036063/34.

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29

Brümmer, T. [Verfasser], and Florian [Akademischer Betreuer] Grüner. "Design Study of a Laser-Driven X-ray Source for Medical Fluorescence Imaging / Theresa Brümmer ; Betreuer: Florian Grüner." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2018. http://nbn-resolving.de/urn:nbn:de:gbv:18-91354.

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30

Adjeiwaah, Mary. "Quality assurance for magnetic resonance imaging (MRI) in radiotherapy." Licentiate thesis, Umeå universitet, Institutionen för strålningsvetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-142603.

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Magnetic resonance imaging (MRI) utilizes the magnetic properties of tissues to generate image-forming signals. MRI has exquisite soft-tissue contrast and since tumors are mainly soft-tissues, it offers improved delineation of the target volume and nearby organs at risk. The proposed Magnetic Resonance-only Radiotherapy (MR-only RT) work flow allows for the use of MRI as the sole imaging modality in the radiotherapy (RT) treatment planning of cancer. There are, however, issues with geometric distortions inherent with MR image acquisition processes. These distortions result from imperfections in the main magnetic field, nonlinear gradients, as well as field disturbances introduced by the imaged object. In this thesis, we quantified the effect of system related and patient-induced susceptibility geometric distortions on dose distributions for prostate as well as head and neck cancers. Methods to mitigate these distortions were also studied. In Study I, mean worst system related residual distortions of 3.19, 2.52 and 2.08 mm at bandwidths (BW) of 122, 244 and 488 Hz/pixel up to a radial distance of 25 cm from a 3T PET/MR scanner was measured with a large field of view (FoV) phantom. Subsequently, we estimated maximum shifts of 5.8, 2.9 and 1.5 mm due to patient-induced susceptibility distortions. VMAT-optimized treatment plans initially performed on distorted CT (dCT) images and recalculated on real CT datasets resulted in a dose difference of less than 0.5%. The magnetic susceptibility differences at tissue-metallic,-air and -bone interfaces result in local B0 magnetic field inhomogeneities. The distortion shifts caused by these field inhomogeneities can be reduced by shimming. Study II aimed to investigate the use of shimming to improve the homogeneity of local B0 magnetic field which will be beneficial for radiotherapy applications. A shimming simulation based on spherical harmonics modeling was developed. The spinal cord, an organ at risk is surrounded by bone and in close proximity to the lungs may have high susceptibility differences. In this region, mean pixel shifts caused by local B0 field inhomogeneities were reduced from 3.47±1.22 mm to 1.35±0.44 mm and 0.99±0.30 mm using first and second order shimming respectively. This was for a bandwidth of 122 Hz/pixel and an in-plane voxel size of 1×1 mm2. Also examined in Study II as in Study I was the dosimetric effect of geometric distortions on 21 Head and Neck cancer treatment plans. The dose difference in D50 at the PTV between distorted CT and real CT plans was less than 1.0%. In conclusion, the effect of MR geometric distortions on dose plans was small. Generally, we found patient-induced susceptibility distortions were larger compared with residual system distortions at all delineated structures except the external contour. This information will be relevant when setting margins for treatment volumes and organs at risk. The current practice of characterizing MR geometric distortions utilizing spatial accuracy phantoms alone may not be enough for an MR-only radiotherapy workflow. Therefore, measures to mitigate patient-induced susceptibility effects in clinical practice such as patient-specific correction algorithms are needed to complement existing distortion reduction methods such as high acquisition bandwidth and shimming.

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31

Karakas, Zeynep N. "Comparative Motion and Dosimetric Analysis of Organs at Risk near Pancreatic Tumors Treated with Stereotactic Body Radiation Therapy with and without Abdominal Compression using 4DCT Datasets." University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1463151135.

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32

Cochran, Eric R. "Silicon Detectors for PET and SPECT." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1285082615.

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33

Che, Ahmad Azlan. "Dynamic contrast-enhanced MRI of breast cancer at 3T." Thesis, University of Aberdeen, 2011. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=165831.

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3T MRI provides higher signal-to-noise ratio images compared to lower field machines. However, a major drawback of 3T MRI is a higher B1 transmission-field inhomogeneity across the field-of-view compared to imaging at lower fields. B1-field mapping was performed on volunteers using a Philips 3.0T MR scanner and a typical head-first prone patient positioning technique. The B1-field transmitted in the breasts was found to be reduced towards the right side of the body. In some volunteers, the B1-field was reduced to about one-half of the nominal field in the right breast. To minimize the B1 inhomogeneity artefacts, a saturation recovery snapshot FLASH (SRSF) imaging sequence was proposed. Different saturation techniques were assessed. The best saturation efficiency was produced by Hoffmann’s saturation method. By using Hoffmann’s SRSF sequence, the error in the enhancement ratio (ER) can be reduced to about one half compared to imaging obtained using typical FLASH sequence in the presence of a 50% B1-field reduction. Other techniques i.e. bilateral power optimization and a dedicated patient support system were also tested. Both of these approaches produced substantial reductions of the B1 inhomogeneity seen with the standard technique. To address the effects of the native T1 (T10) of different tissues on DCE-MRI, novel enhancement factor indices calculated using SRSF sequence images were introduced and assessed. Computer simulations and gel phantom experiments showed that less error was observed in the indices calculated compared to the ER calculated using the conventional and widely used FLASH sequence. Furthermore, the effect of B1-field inhomogeneity on the novel indices is also reduced. One of the indices proposed is directly related to the contrast agent concentration. The theory and results presented show that the SRSF pulse sequence and the quantification techniques proposed have the potential to improve the accuracy of breast DCE-MRI at 3T.

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34

Lamichhane, Narottam. "Multimodality Molecular Imaging of [18F]-Fluorinated Carboplatin Derivative Encapsulated in [111In]-Labeled Liposome." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3347.

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Platinum based chemotherapy is amongst the mainstream DNA-damaging agents used in clinical cancer therapy today. Agents such as cisplatin, carboplatin are clinically prescribed for the treatment of solid tumors either as single agents, in combination, or as part of multi-modality treatment strategy. Despite the potent anti-tumor activity of these drugs, overall effectiveness is still hampered by inadequate delivery and retention of drug in tumor and unwanted normal tissue toxicity, induced by non-selective accumulation of drug in normal cells and tissues. Utilizing molecular imaging and nanoparticle technologies, this thesis aims to contribute to better understanding of how to improve the profile of platinum based therapy. By developing a novel fluorinated derivative of carboplatin, incorporating a Flourine-18 (18F) moiety as an inherent part of the molecule, quantitative measures of drug concentration in tumors and normal tissues can be directly determined in vivo and within the intact individual environment. A potential impact of this knowledge will be helpful in predicting the overall response of individual patients to the treatment. Specifically, the aim of this project, therefore, is the development of a fluorinated carboplatin drug derivative with an inherent positron emission tomography (PET) imaging capability, so that the accumulation of the drug in the tumor and normal organs can be studied during the course of therapy . A secondary objective of this research is to develop a proof of concept for simultaneous imaging of a PET radiolabeled drug with a SPECT radiolabeled liposomal formulation, enabling thereby bi-modal imaging of drug and delivery vehicle in vivo. The approach is challenging because it involves development in PET radiochemistry, PET and SPECT imaging, drug liposomal encapsulation, and a dual-modal imaging of radiolabeled drug and radiolabeled vehicle. The principal development is the synthesis of fluorinated carboplatin 19F-FCP using 2-(5-fluoro-pentyl)-2-methyl malonic acid as the labeling agent to coordinate with the cisplatin aqua complex. It was then used to treat various cell lines and compared with cisplatin and carboplatin at different concentrations ranging from 0.001 µM to 100 µM for 72 hrs and 96 hrs. IC50 values calculated from cell viability indicated that 19F-FCP is a more potent drug than Carboplatin. Manual radiosynthesis and characterization of [18F]-FCP was performed using [18F]-2-(5-fluoro-pentyl)-2-methyl malonic acid with coordination with cisplatin aqua complex. Automated radiosynthesis of [18F]-FCP was optimized using the manual synthetic procedures and using them as macros for the radiosynthesizer. [18F]-FCP was evaluated in vivo with detailed biodistribution studies and PET imaging in normal and KB 3-1 and KB 8-5 tumor xenograft bearing nude mice. The biodistribution studies and PET imaging of [18F]-FCP showed major uptake in kidneys which attributes to the renal clearance of radiotracer. In vivo plasma and urine stability demonstrated intact [18F]-FCP. [111In]-Labeled Liposomes was synthesized and physiochemical properties were assessed with DLS. [111In]-Labeled Liposome was evaluated in vivo with detailed pharmacokinetic studies and SPECT imaging. The biodistribution and ROI analysis from SPECT imaging showed the spleen and liver uptake of [111In]-Labeled Liposome and subsequent clearance of activity with time. [18F]-FCP encapsulated [111In]-Labeled Liposome was developed and physiochemical properties were characterized with DLS. [18F]-FCP encapsulated [111In]-Labeled Liposome was used for in vivo dual tracer PET and SPECT imaging from the same nanoconstruct in KB 3-1 (sensitive) and COLO 205 (resistant) tumor xenograft bearing nude mice. PET imaging of [18F]-FCP in KB 3-1 (sensitive) and COLO 205 (resistant) tumor xenograft bearing nude mice was performed. Naked [18F]-FCP and [18F]-FCP encapsulated [111In]-Labeled Liposome showed different pharmacokinetic profiles. PET imaging of [18F]-FCP showed major uptake in kidneys and bladder. However, [18F]-FCP encapsulated [111In]-Labeled Liposome showed major uptake in RES in both PET and SPECT images. ROI analysis of SPECT image enabled by 111In corresponded with PET image enabled by 18F demonstrating the feasibility of dual tracer imaging from the single nanoconstruct. Future work involves the intensive in vitro characterization of [18F]-FCP encapsulated [111In]-Labeled Liposome and detailed in vivo evaluation of [18F]-FCP encapsulated [111In]-Labeled Liposome in various tumor models.

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35

Walker, Justin A. "The Use of an On-Board MV Imager for Plan Verification of Intensity Modulated Radiation Therapy and Volumetrically Modulated Arc Therapy." University of Toledo Health Science Campus / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=mco1372701428.

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36

Sanders, William F. IV. "Computed Tomography Reconstruction: Investigating the Effect of Varying Circle Diameter." Wright State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=wright1308095868.

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37

Antonelli, Maria Rosaria. "Biomedical applications of polarimetric imaging contrast. Initial studies for scattering media and human tissues." Phd thesis, Ecole Polytechnique X, 2011. http://pastel.archives-ouvertes.fr/pastel-00652201.

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L'amélioration de la visualisation in vivo des lésions précancéreuse (dysplasies) du col utérin est essentielle pour mieux identifier les zones à biopsier et pour optimiser la définition des limites d'exérèse chirurgicale. Dans ce but nous étudions une nouvelle technique d'imagerie polarimétrique en rétrodiffusion, que nous avons mise en oeuvre sur des échantillons ex vivo dans des configurations expérimentales variées afin d'optimiser le diagnostic in vivo. Comme cette optimisation passe par la compréhension des contrastes polarimétriques observés, nous avons réalisé de nombreuses simulations de la propagation de lumière polarisée dans des structures multicouche représentatives des tissus. Ces structures comprennent typiquement une couche comportant des diffuseurs dans une matrice homogène et représentant l'épithélium ou le tissu conjonctif superficiel, et un substrat lambertien totalement dépolarisant pour les couches plus profondes. Ces simulations ont été effectuées au moyen d'un code Monte Carlo que nous avons adapté à notre problématique. Nous avons ainsi montré que la contribution des noyaux cellulaires est très faible en rétrodiffusion. Pour le tissu conjonctif, les fibres de collagène, modélisées par des diffuseurs sphériques de 200 nm de rayon, donnent une contribution plus importante que les noyaux, mais ne reproduisent pas la réponse polarimétrique de type Rayleigh observée dans tous les tissus étudiés, qu'ils soient sains ou pathologiques. En revanche, l'inclusion de diffuseurs de taille nettement inférieure à la longueur d'onde, modélisés par des sphères de 50 nm, permet de reproduire cette réponse de manière très stable. Ces diffuseurs correspondent a priori aux protéines intracellulaires. Dans le cadre de ce modèle, les contrastes observés entre tissus sains et cancéreux s'expliquent essentiellement par une variation de la concentration de ces petits diffuseurs. Ce résultat, encore préliminaire, suggère que l'imagerie polarimétrique en rétrodiffusion peut être sensible non seulement à la morphologie, mais également à l'état physiologique du tissu, ce qui peut s'avérer important pour la détection sélective des dysplasies.

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38

Wu, Yong. "Relaxation Effects in Magnetic Nanoparticle Physics: MPI and MPS Applications." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1370865200.

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39

Levi, Jacob. "Automated Beam Hardening Correction for Myocardial Perfusion Imaging using Computed Tomography." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1553868329519413.

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40

Poon, Chien Sing. "Early Assessment of Burn Severity in Human Tissue with Multi-Wavelength Spatial Frequency Domain Imaging." Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1484582176416423.

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41

Gaaß, Thomas [Verfasser], Axel [Akademischer Betreuer] Haase, and Franz [Akademischer Betreuer] Pfeiffer. "Acceleration of Radial Data Acquisition in Medical Imaging via Iterative, Histogram-Constrained Reconstruction / Thomas Gaaß. Gutachter: Axel Haase ; Franz Pfeiffer. Betreuer: Axel Haase." München : Universitätsbibliothek der TU München, 2013. http://d-nb.info/1046404695/34.

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42

Lindbäck, Elias. ""Imaging with CBCT and 4D-CT of objects moving with respiratory motions"." Thesis, Stockholms universitet, Medicinsk strålningsfysik (tills m KI), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-89053.

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AB S TRACT purpose : To further investigate the effects of respiratory motions on CBCT imaging, as well as 4D-CT examinations, with a future goal of using obtained results to implement new methods for individual margins and daily matching procedures into routine clinical practice. background : Since the implementation of CBCT combined with modern accelerators, a higher degree of accuracy has been made possible in RT. However, due to the slow gantry speed of linear accelerators, the imaging procedure of CBCT is a slow process which is thereby degraded by internal motion such as respiration. material and methods : Attain patient specific respiratory motion patterns from CBCT projection data of previous examinations. Utilize this data to perform simulations for both CBCT and 4D-CT using a steering system which allows for arbitrary motion patterns in the longitudinal direction. results : Various imaging with CBCT showed that the resulting images during respiratory motion, can be described by the Probability Density Function of the motion for as long as it does not cause related distortions. This also meant that convolution could be implemented as a model to estimate the CBCT images during oscillation, knowing the object and motion pattern. The 4D-CT examinations using the steering system showed that irregular motion patterns were less accurately described than regular patterns, making the actual motion an important feature to combine together with the measured amplitude. conclusions : It was made clear that CBCT images can be described by the PDF, and thus can be seen as a Color Intensity Projection of the object position. Also it has been shown that the projection data of CBCT images contains valuable information about the respiratory motion of the patient. Another conclusion is that with the help of fiducials, the position of the target within the respiratory cycle can be determined relative to the 4D-CT examination, enabling further input data as to the daily matching procedure, proper applied margins as well as dose to the OAR.

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43

Young, Anthony M. "Investigation of Laser Speckle Contrast Imaging's Sensitivity to Flow." Miami University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=miami153256524246362.

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44

Corwin, Frank. "Characterization of a Blast Wave Device and Blast Wave Induced Traumatic Brain Injury in a Rat Model by Magnetic Resonance Imaging and Spectroscopy." VCU Scholars Compass, 2011. http://scholarscompass.vcu.edu/etd/2403.

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Blast wave induced traumatic brain injury (bTBI) is a modality of injury that has come into prominence at the current time due to the large number of military and civilian personnel who have experienced the localized shock wave produced by explosive devices. The shock wave will travel concentrically outward from the explosive center, being absorbed and transmitted thru soft objects, such as tissue, and reflecting off stationary obstructions. Transmission and absorption in tissues can result in a number of physiological measureable injuries, the most common of which being what is frequently called “blast lung”. Blast lung involves the spalling effect at air-tissue interfaces. Another documented effect involves the asynchronous motion of tissue, particularly in the cranium, as the shock wave passes by. This predominately manifests itself in what is believed to be diffuse axonal injury and initiation of secondary injury mechanism. This study is designed to explore the relationship between shock waves and bTBI. A blast device was constructed for generating a free field shock wave through the high pressure rupture of a polycarbonate membrane. Air pressure in a small chamber is increased to a value several orders of magnitude greater than ambient air pressure and is held in place with the polycarbonate member. At the rupture of this membrane a shock wave is created. Measurements of this blast event, carried out with a piezoelectric pressure transducer, have shown that this shock wave is reproducible for the different membrane materials tested and is symmetrical with respect to the central axis of the high pressure chamber and exit nozzle. Having characterized the shock wave properties in the blast field, a location was chosen at which maximum shock wave pressure could be applied to the cranium for inducing bTBI. Experiments involving blast wave exposure were performed on two separate groups of animals in an attempt at establishing injury. One group was placed at a fixed distance directly below the blast nozzle, thereby experiencing both the shock wave and the associated air blast from the residual air in the chamber, and one placed at a defined distance off-axis to avoid the air blast, yet receiving two sequential blast exposures. All animal studies were approved by the VCU Institutional Animal Care and Use Committee. The degree of injury was then assessed with the use of magnetic resonance imaging (MRI) and spectroscopy (MRS). Image Data was acquired on a 2.4 Tesla magnet for assessing changes in either the total percent water concentration or the apparent diffusion coefficients (ADC) of selected regions of interest in the brain of rats. Localized proton spectroscopic data was acquired from a voxel placed centrally in the brain. The baseline values of these parameters were established before the induction of bTBI. After the blast exposure, the animals were followed up with MRI and MRS at defined intervals over a period of one week. The first group of animals received blast exposure directly underneath the blast device nozzle and the MR data does suggest changes in some of the measureable parameters from baseline following blast exposure. This blast wave data though is confounded with additional and undesirable characteristics of the blast wave. The second group of animals that received a pure shock wave blast exposure revealed no remarkable changes in the MR data pre- to post- blast exposure. The percent water concentration, ADC and spectroscopic parameters were for statistical purposes identical before and after the blast. The resolution of this negative result will require reconsideration of the free field blast exposure concept.

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45

Thapa, Bishnu Bahadur. "DEVELOPMENT OF A PATIENT SPECIFIC IMAGE PLANNING SYSTEM FOR RADIATION THERAPY." UKnowledge, 2013. http://uknowledge.uky.edu/physastron_etds/11.

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A patient specific image planning system (IPS) was developed that can be used to assist in kV imaging technique selection during localization for radiotherapy. The IPS algorithm performs a divergent ray-trace through a three dimensional computed tomography (CT) data set. Energy-specific attenuation through each voxel of the CT data set is calculated and imaging detector response is integrated into the algorithm to determine the absolute values of pixel intensity and image contrast. Phantom testing demonstrated that image contrast resulting from under exposure, over exposure as well as a contrast plateau can be predicted by use of a prospective image planning algorithm. Phantom data suggest the potential for reducing imaging dose by selecting a high kVp without loss of image contrast. In the clinic, image acquisition parameters can be predicted using the IPS that reduce patient dose without loss of useful image contrast.

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46

Pépin, Jérémy. "Développement de l’imagerie métabolique par IRM-CEST : application à la maladie de Huntington." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS032/document.

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La maladie de Huntington (MH) est une maladie neurodégénérative héréditaire qui affecte le cerveau. Cette maladie est caractérisée par des signes cliniques tels que la dépression, la démence ainsi que des troubles moteurs s’aggravant au fil du temps. Ces déficiences sont dues à une augmentation anormale de la taille des répétitions CAG dans le gène codant la protéine huntingtine. Celle-ci s’accumule dans les cellules cérébrales et entraine leur mort. Des études antérieures ont démontré que le profil métabolique mesuré en spectroscopie RMN ¹H pouvait être altéré chez les patients atteints de cette maladie ainsi que des atrophies majeures de certaines structures du cerveau. Des hypothèses impliquant des défauts du métabolisme énergétique ont été avancées pour expliquer en partie la physiopathologie de la maladie. Les acteurs du métabolisme pourraient ainsi constituer des biomarqueurs d’intérêt. A l'aide d'une modalité d'IRM prometteuse appelée CEST (Chemical Exchange Saturation Transfer : Transfert de Saturation par Echange Chimique) il est possible de détecter des protons labiles faiblement concentrés qui sont classiquement indétectables en IRM. Il devient ainsi possible de cartographier in vivo la distribution de métabolites comme le glutamate (qui est un neurotransmetteur) ou le glucose (qui est le carburant des cellules) qui sont potentiellement impliqués dans les maladies neurodégénératives. Les développements méthodologiques effectués lors de cette thèse ont ensuite été appliqués à des modèles de rongeurs de la maladie de Huntington (souris KI140, souris R6/1, rats BACHD) afin d'identifier les biomarqueurs potentiels de la pathologie et d'évaluer la pertinence de ces méthodes IRM innovantes. L’ensemble de ces résultats et des méthodes mises en place durant cette thèse montrent le potentiel de l’imagerie CEST pour l’étude des maladies neurodégénératives
Huntington's disease (HD) is a inherited neurodegenerative disease affecting the brain. This disease is characterized by clinical symptoms such as psychiatric, cognitive and motor disorders worsening over time. These deficiencies are due to an abnormal increase in the size of the CAG repeats in the gene encoding the huntingtin protein. Thisaccumulates in the brain cells and causes their death. Previous studies have shown that the metabolic profile measured in ¹H NMR spectroscopy can be altered in patients with this disease as well as major atrophy of certain structures of the brain. Hypotheses involving defects in energy metabolism have been advanced to explain partially the pathophysiology of the disease. The metabolic actors could thus be biomarkers of interest. Using a promising MRI modality called Chemical Exchange Saturation Transfer (CEST), it is possible to detect low-concentrated labile protons that are classically undetectable in MRI. It thus becomes possible to map in vivo the distribution of metabolites such as glutamate (which is a neurotransmitter) or glucose (which is the fuel of cells) which are potentially involved in neurodegenerative diseases. The methodological developments carried out during this thesis were then applied to rodent models of Huntington's disease (KI140 mice, R6/1 mice, BACHD rats) in order to identify potential biomarkers of the pathology and to evaluate the relevance of these innovative MRI methods. All of these results and methods implemented during this thesis show the potential of CEST imaging for the study of neurodegenerative diseases

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47

Nilsson, Erik. "Super-Resolution for Fast Multi-Contrast Magnetic Resonance Imaging." Thesis, Umeå universitet, Institutionen för fysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-160808.

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There are many clinical situations where magnetic resonance imaging (MRI) is preferable over other imaging modalities, while the major disadvantage is the relatively long scan time. Due to limited resources, this means that not all patients can be offered an MRI scan, even though it could provide crucial information. It can even be deemed unsafe for a critically ill patient to undergo the examination. In MRI, there is a trade-off between resolution, signal-to-noise ratio (SNR) and the time spent gathering data. When time is of utmost importance, we seek other methods to increase the resolution while preserving SNR and imaging time. In this work, I have studied one of the most promising methods for this task. Namely, constructing super-resolution algorithms to learn the mapping from a low resolution image to a high resolution image using convolutional neural networks. More specifically, I constructed networks capable of transferring high frequency (HF) content, responsible for details in an image, from one kind of image to another. In this context, contrast or weight is used to describe what kind of image we look at. This work only explores the possibility of transferring HF content from T1-weighted images, which can be obtained quite quickly, to T2-weighted images, which would take much longer for similar quality. By doing so, the hope is to contribute to increased efficacy of MRI, and reduce the problems associated with the long scan times. At first, a relatively simple network was implemented to show that transferring HF content between contrasts is possible, as a proof of concept. Next, a much more complex network was proposed, to successfully increase the resolution of MR images better than the commonly used bicubic interpolation method. This is a conclusion drawn from a test where 12 participants were asked to rate the two methods (p=0.0016) Both visual comparisons and quality measures, such as PSNR and SSIM, indicate that the proposed network outperforms a similar network that only utilizes images of one contrast. This suggests that HF content was successfully transferred between images of different contrasts, which improves the reconstruction process. Thus, it could be argued that the proposed multi-contrast model could decrease scan time even further than what its single-contrast counterpart would. Hence, this way of performing multi-contrast super-resolution has the potential to increase the efficacy of MRI.

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48

Evans, Eleanor. "Improved quantification in small animal PET/MR." Thesis, University of Cambridge, 2015. https://www.repository.cam.ac.uk/handle/1810/252640.

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In translational medicine, complementary functional and morphological imaging techniques are used extensively to observe physiological processes in vivo and to assess structural changes as a result of disease progression. The combination of magnetic resonance imaging (MRI) and positron emission tomography (PET) provides excellent soft tissue contrast from MRI with exceptional sensitivity and specificity from PET. This thesis explores the use of sequentially acquired PET and MR images to improve the quantification of small animal PET data. The primary focus was to improve image-based estimates of the arterial input function (AIF), which defines the amount of PET tracer within blood plasma over time. The AIF is required to produce physiological parameters quantifying key processes such as metabolism or perfusion from dynamic PET images. The gold standard for AIF measurement, however, requires serial blood sampling over the course of a PET scan, which is invasive in rat studies but prohibitive in mice due to small total blood volumes. To address this issue, the geometric transfer matrix (GTM) and recovery coefficient (RC) techniques were applied using anatomical MR images to enable the extraction of partial volume corrected image based AIFs from mouse PET images. A non-invasive AIF extraction method was also developed for rats, beginning with the optimization of an automated voxel selection algorithm to assist in extracting MR contrast agent signal time courses from dynamic susceptibility contrast (DSC) MRI data. This procedure was then combined with dynamic contrast enhanced (DCE) MRI to track a combined injection of Gadolinium-based contrast agent and PET tracer through the rat brain. By comparison with gold standard tracer blood sample data, it was found that normalized MRI-based AIFs could be successfully converted into PET tracer AIFs in the first pass phase when fitted with gamma variate functions. Finally, a MR image segmentation method used to provide PET attenuation correction in mice was validated using the Cambridge split magnet PET/MR scanner?s transmission scanning capabilities. This work recommends that contributions from MR hardware in the PET field of view must be accounted forto gain accurate estimates of tracer uptake and standard uptake values (SUVs). This thesis concludes that small animal MR data taken in the same imaging session can provide non-invasive methods to improve PET image quantification, giving added value to combined PET/MR studies over those conducted using PET alone.

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Greene, Carmen M. "Experience using a small field of view gamma camera for intraoperative sentinel lymph node procedures." Thesis, Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-01132006-160335/.

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Kellermeier, Markus [Verfasser], and Reinhold [Akademischer Betreuer] Müller. "Physical assessment of a novel concept for computed tomography with a stationary source ring of fixed X-ray anodes for medical imaging / Markus Kellermeier. Gutachter: Reinhold Müller." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2015. http://d-nb.info/1076120326/34.

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Dissertations / Theses on the topic 'Medical imaging : Medical physics'

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