Journal articles: 'Accuracy assessment phantom'

1

Nakanishi, Nobuto, Shigeaki Inoue, Rie Tsutsumi, Yusuke Akimoto, Yuko Ono, Joji Kotani, Hiroshi Sakaue, and Jun Oto. "Rectus Femoris Mimicking Ultrasound Phantom for Muscle Mass Assessment: Design, Research, and Training Application." Journal of Clinical Medicine 10, no. 12 (June 20, 2021): 2721. http://dx.doi.org/10.3390/jcm10122721.

Full text

Abstract:

Ultrasound has become widely used as a means to measure the rectus femoris muscle in the acute and chronic phases of critical illness. Despite its noninvasiveness and accessibility, its accuracy highly depends on the skills of the technician. However, few ultrasound phantoms for the confirmation of its accuracy or to improve technical skills exist. In this study, the authors created a novel phantom model and used it for investigating the accuracy of measurements and for training. Study 1 investigated how various conditions affect ultrasound measurements such as thickness, cross-sectional area, and echogenicity. Study 2 investigated if the phantom can be used for the training of various health care providers in vitro and in vivo. Study 1 showed that thickness, cross-sectional area, and echogenicity were affected by probe compression strength, probe angle, phantom compression, and varying equipment. Study 2 in vitro showed that using the phantom for training improved the accuracy of the measurements taken within the phantom, and Study 2 in vivo showed the phantom training had a short-term effect on improving the measurement accuracy in a human volunteer. The new ultrasound phantom model revealed that various conditions affected ultrasound measurements, and phantom training improved the measurement accuracy.

APA, Harvard, Vancouver, ISO, and other styles

2

Paštyková, Veronika, Josef Novotný, Tomáš Veselský, Dušan Urgošík, Roman Liščák, and Josef Vymazal. "Assessment of MR stereotactic imaging and image co-registration accuracy for 3 different MR scanners by 3 different methods/phantoms: phantom and patient study." Journal of Neurosurgery 129, Suppl1 (December 2018): 125–32. http://dx.doi.org/10.3171/2018.7.gks181527.

Full text

Abstract:

OBJECTIVEThe aim of this study was to compare 3 different methods to assess the geometrical distortion of two 1.5-T and one 3-T magnetic resonance (MR) scanners and to evaluate co-registration accuracy. The overall uncertainty of each particular method was also evaluated.METHODSThree different MR phantoms were used: 2 commercial CIRS skull phantoms and PTGR known target phantom and 1 custom cylindrical Perspex phantom made in-house. All phantoms were fixed in the Leksell stereotactic frame and examined by a Siemens Somatom CT unit, two 1.5-T Siemens (Avanto and Symphony) MRI systems, and one 3-T Siemens (Skyra) MRI system. The images were evaluated using Leksell GammaPlan software, and geometrical deviation of the selected points from the reference values were determined. The deviations were further investigated for both definitions including fiducial-based and co-registration–based in the case of the CIRS phantom images. The same co-registration accuracy assessment was also performed for a clinical case. Patient stereotactic imaging was done on 3-T Skyra, 1.5-T Avanto, and CT scanners.RESULTSThe accuracy of the CT scanner was determined as 0.10, 0.30, and 0.30 mm for X, Y, and Z coordinates, respectively. The total estimated uncertainty in distortion measurement in one coordinate was determined to be 0.32 mm and 0.14 mm, respectively, for methods using and not using CT as reference imaging. Slightly more significant distortions were observed when using the 3-T than either 1.5-T MR units. However, all scanners were comparable within the estimated measurement error. Observed deviation/distortion for individual X, Y, and Z stereotactic coordinates was typically within 0.50 mm for all 3 scanners and all 3 measurement methods employed. The total radial deviation/distortion was typically within 1.00 mm. Maximum total radial distortion was observed when the CIRS phantom was used; 1.08 ± 0.49 mm, 1.15 ± 0.48 mm, and 1.35 ± 0.49 mm for Symphony, Avanto, and Skyra, respectively. The co-registration process improved image stereotactic definition in a clinical case in which fiducial-based stereotactic definition was not accurate; this was demonstrated for 3-T stereotactic imaging in this study. The best results were shown for 3-T MR image co-registration with CT images improving image stereotactic definition by about 0.50 mm. The results obtained with patient data provided a similar trend of improvement in stereotactic definition by co-registration.CONCLUSIONSAll 3 methods/phantoms used were evaluated as satisfactory for the image distortion measurement. The method using the PTGR phantom had the lowest uncertainty as no reference CT imaging was needed. Image co-registration can improve stereotactic image definition when fiducial-based definition is not accurate.

APA, Harvard, Vancouver, ISO, and other styles

3

Prionas, Nicolas D., Shonket Ray, and John M. Boone. "Volume assessment accuracy in computed tomography: a phantom study." Journal of Applied Clinical Medical Physics 11, no. 2 (March 2010): 168–80. http://dx.doi.org/10.1120/jacmp.v11i2.3037.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Lee, Ki Baek, Ki Chang Nam, Ji Sung Jang, and Ho Chul Kim. "Feasibility of the Quantitative Assessment Method for CT Quality Control in Phantom Image Evaluation." Applied Sciences 11, no. 8 (April 16, 2021): 3570. http://dx.doi.org/10.3390/app11083570.

Full text

Abstract:

Computed tomography (CT) quality control (QC) is regularly performed with standard phantoms, to bar faulty equipment from medical use. Its accuracy may be improved by replacing qualitative methods based on good visual distinction with pixel value-based quantitative methods. We hypothesized that statistical texture analysis (TA) that covers the entire phantom image would be a more appropriate tool. Therefore, our study devised a novel QC method based on the TA for contrast resolution (CR) and spatial resolution (SR) and proposed new, quantitative CT QC criteria. TA of CR and SR images on an American Association of Physicists in Medicine (AAPM) CT Performance Phantom were performed with nine CT scanner models. Six texture descriptors derived from first-order statistics of grayscale image histograms were analyzed. Principal component analysis was used to reveal descriptors with high utility. For CR evaluation, contrast and softness were the most accurate descriptors. For SR evaluation, contrast, softness, and skewness were the most useful descriptors. We propose the following ranges: contrast for CR, 29.5 ± 15%, for SR, 29 ± 10%; softness for CR, <0.015, for SR, <0.014; and skewness for SR, >−1.85. Our novel TA method may improve the assessment of CR and SR of AAPM phantom images.

APA, Harvard, Vancouver, ISO, and other styles

5

Petraikin, A. V., M. Ya Smoliarchuk, F. A. Petryaykin, L. A. Nisovtsova, Z. R. Artyukova, K. A. Sergunova, E. S. Akhmad, D. S. Semenov, A. V. Vladzymyrsky, and S. P. Morozov. "Assessment the Accuracy of Densitometry Measurements Using DMA PP2 Phantom." Traumatology and Orthopedics of Russia 25, no. 3 (October 18, 2019): 124–34. http://dx.doi.org/10.21823/2311-2905-2019-25-3-124-134.

Full text

Abstract:

Purpose of the study — to assess the accuracy of dual energy x-ray absorptiometry (DXA ) for measurements of mineral bone density, bone mineral content, area of selected spine zone of examination as well as impact of subcutaneous fat layer and correction of auto-segmenting of the spine on the mentioned parameters. Material and Methods. The study was performed on iDXA scanner using the designed phantom DMA PP2 of the lumber spine with inlays to simulate subcutaneous fat (SF). To ensure correct assessment of measurements (precision and accuracy) the authors performed fivefold repeated scanning. Two modifications of the phantom were used, with and without SF inlays, as well as two methods for selection of spine range for examination – automatic and correction of autosegmentation. Results. Scanning of the phantom without SF inlays demonstrated a systematic understated values of bone mineral density (BMD) and bone mineral content (BMC) along the full measured interval: mean relative error of BMD for L1-L4 interval was 10.62% with automatic segmentation and 7.43% — with correction of autosegmentation. The least accuracy for BMD and BMC (1.53% and 0.90%, respectively) was observed during SF simulation and with correction of auto-segmentation of the spine. Analysis of variation coefficient for area of examined vertebrae, BMC and BMD demonstrated rather high precision of measurements, namely for BMD without SF in the L1-L4 interval amounted to 1.00% (auto-segmentation) and 0.56% (correction). Variation coefficient for scanning including SF inlays in the interval L1-L4 was 1.00% (auto-segmentation) and 0.68% (correction). Conclusion. The lowest level of accuracy was observed with the SFL object; in this case, the variation coefficient did not exceed 1% for all BMD interval. The mean value of the BMC accuracy also did not exceed 1% with the optimal scan parameters. The study proved the effectiveness of “RSK PK2” phantom when estimating the accuracy of BMD and BMC on iDXA scanner.

APA, Harvard, Vancouver, ISO, and other styles

6

Petraikin, A. V., K. A. Sergunova, D. S. Semenov, E. S. Akhmad, S. Yu Kim, A. I. Gromov, and S. P. Morozov. "Dynamic Phantom for Flow Model in Magnetic Resonance Angiography." Medical Visualization, no. 6 (December 28, 2017): 130–39. http://dx.doi.org/10.24835/1607-0763-2017-6-130-139.

Full text

Abstract:

Purpose. To develop phantom for flow modeling in magnetic resonance angiography (MRA): relative contrast assessment, accuracy of the linear velocity and volumetric flow, what improve accuracy of diagnostic in cardiac and neurosurgical clinics (quality assessment of blood and cerebrospinal fluid motion). To compare scanners of different manufactures in points of the MRA efficiency using the developed phantom.Materials and methods. The main part of dynamic phantom consists of a disc filled with agarose gel (for linear and volumetric velocity control) and silicone tubes for fluid flow modelling. MR study was performed at MRI units of two manufactures for comparing quantitative assessments of MRA sequences: 2DTOF, 3DTOF, and at three MRI units of one firm for estimated accuracy calibration curve calculating and linear velocity and volumetric flow determination for PC MRA. Phantom study well correlate with clinical MRA results.Results. Obtained phantom scanning results in 2DTOF, 3DTOF sequences allow for objective comparing two MRI units of different manufactures. For 2DTOF mode was showed more effective signal enhancement affected by TOF effect for scanner of manufacture 2, then manufacture 1: 8.86 ± 0.88 и 6.07 ± 0.03 corresponding. For 3DTOF was observed rather more inflow relative contrast affected by TOF effect for scanner of manufacture 1: 6.06 ± 0.47 and 3.17 ± 0.83 corresponding. However, for manufacture 1 was showed more significant signal suppression for fat tissue, which improve vasculature visualization. Accuracy linear velocity fluid flow measurement in 2DPC is equal to ±2σ = ±0,4 by five pixels for three scanners of one manufacture. Using developed phantom was modelled MRA effects in 3DPC and Time-SLIP modes.Conclusions. The developed dynamic phantom can be used for calibration tests in MRA. The case of MRI units of two manufactures were compared quantitative assessments of MRA sequences and analyzed methods of enhancement fluid flow signal.

APA, Harvard, Vancouver, ISO, and other styles

7

Ringel, Florian, Dominik Ingerl, Stephanie Ott, and Bernhard Meyer. "VARIOGUIDE: A NEW FRAMELESS IMAGE‐GUIDED STEREOTACTIC SYSTEM—ACCURACY STUDY AND CLINICAL ASSESSMENT." Operative Neurosurgery 64, suppl_5 (May 1, 2009): ons365—ons373. http://dx.doi.org/10.1227/01.neu.0000341532.15867.1c.

Full text

Abstract:

Abstract OBJECTIVE VarioGuide (BrainLAB AG, Feldkirchen, Germany) is a new system for frameless image-guided stereotaxy. In the present study, we aimed to assess target point accuracy in a laboratory setting and the clinical feasibility of the system. METHODS Using the phantom of our frame-based stereotactic system (Riechert-Mundinger; Inomed Medizintechnik GmbH, Teningen, Germany), target points were approached from different angles with the frameless system. Target point deviation in the x, y, and z planes was assessed. Furthermore, patients harboring intracranial lesions were diagnostically biopsied using VarioGuide. RESULTS Phantom-based accuracy measurements yielded a mean target point deviation of 0.7 mm. Between February 2007 and April 2008, 27 patients were diagnostically biopsied. Lesion volumes ranged from 0.2 to 117.6 cm3, trajectory length ranged from 25.3 to 64.1 mm, and the diagnostic yield was 93%. CONCLUSION Concluding from the phantom measurements with ideal image-object registration, assumed spherical lesions with a volume of 0.524 cm3 can be biopsied with 100% target localization. Early clinical data revealed VarioGuide to be safe and accurate for lesions of 0.2 cm3 and larger. Thereby, the system seems feasible for the biopsy of most intracranial lesions.

APA, Harvard, Vancouver, ISO, and other styles

8

Halim, Fatin, Hizwan Yahya, Khairul Nizam Jaafar, and Syahir Mansor. "Accuracy Assessment of SUV Measurements in SPECT/CT: A Phantom Study." Journal of Nuclear Medicine Technology 49, no. 3 (March 15, 2021): 250–55. http://dx.doi.org/10.2967/jnmt.120.259168.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Hoffman, Edward J., P. Duffy Cutler, Thomas M. Guerrero, Ward M. Digby, and John C. Mazziotta. "Assessment of Accuracy of PET Utilizing a 3-D Phantom to Simulate the Activity Distribution of [18F]Fluorodeoxyglucose Uptake in the Human Brain." Journal of Cerebral Blood Flow & Metabolism 11, no. 1_suppl (March 1991): A17—A25. http://dx.doi.org/10.1038/jcbfm.1991.32.

Full text

Abstract:

A three-dimensional brain phantom has been developed to simulate the activity distributions found in human brain studies currently employed in positron emission tomography (PET). The phantom has a single contiguous chamber and utilizes thin layers of lucite to provide apparent relative concentrations of 5, 1, and 0 for gray matter, white matter, and CSF structures, respectively. The phantom and an ideal image set were created from the same set of data. Thus, the user has a basis for comparing measured images with an ideal set that allows a quantitative evaluation of errors in PET studies with an activity distribution similar to that found in patients. The phantom was employed in a study of the effect of deadtime and scatter on accuracy in quantitation on a current PET system. Deadtime correction factors were found to be significant (1.1–2.5) at count rates found in clinical studies. Deadtime correction techniques were found to be accurate to within 5%. Scatter in emission and attenuation correction data consistently caused 5–15% errors in quantitation, whereas correction for scatter in both types of data reduced errors in accuracy to <5%.

APA, Harvard, Vancouver, ISO, and other styles

10

Radojcic, Đeni Smilovic, David Rajlic, Bozidar Casar, Manda Svabic Kolacio, Nevena Obajdin, Dario Faj, and Slaven Jurkovic. "Evaluation of two-dimensional dose distributions for pre-treatment patient-specific IMRT dosimetry." Radiology and Oncology 52, no. 3 (April 30, 2018): 346–52. http://dx.doi.org/10.2478/raon-2018-0019.

Full text

Abstract:

Abstract Background The accuracy of dose calculation is crucial for success of the radiotherapy treatment. One of the methods that represent the current standard for patient-specific dosimetry is the evaluation of dose distributions measured with an ionization chamber array inside a homogeneous phantom using gamma method. Nevertheless, this method does not replicate the realistic conditions present when a patient is undergoing therapy. Therefore, to more accurately evaluate the treatment planning system (TPS) capabilities, gamma passing rates were examined for beams of different complexity passing through inhomogeneous phantoms. Materials and methods The research was performed using Siemens Oncor Expression linear accelerator, Siemens Somatom Open CT simulator and Elekta Monaco TPS. A 2D detector array was used to evaluate dose distribution accuracy in homogeneous, semi-anthropomorphic and anthropomorphic phantoms. Validation was based on gamma analysis with 3%/3mm and 2%/2mm criteria, respectively. Results Passing rates of the complex dose distributions degrade depending on the thickness of non-water equivalent material. They also depend on dose reporting mode used. It is observed that the passing rate decreases with plan complexity. Comparison of the data for all set-ups of semi-anthropomorphic and anthropomorphic phantoms shows that passing rates are higher in the anthropomorphic phantom. Conclusions Presented results raise a question of possible limits of dose distribution verification in assessment of plan delivery quality. Consequently, good results obtained using standard patient specific dosimetry methodology do not guarantee the accuracy of delivered dose distribution in real clinical cases.

APA, Harvard, Vancouver, ISO, and other styles

11

Peppa, M. V., J. Hall, J. Goodyear, and J. P. Mills. "PHOTOGRAMMETRIC ASSESSMENT AND COMPARISON OF DJI PHANTOM 4 PRO AND PHANTOM 4 RTK SMALL UNMANNED AIRCRAFT SYSTEMS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W13 (June 4, 2019): 503–9. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w13-503-2019.

Full text

Abstract:

<p><strong>Abstract.</strong> Consumer-grade Unmanned Aircraft Systems (UAS), and particularly Small Unmanned Aircraft (SUA) weighing less than 20&thinsp;kg, have recently become very attractive for photogrammetric data acquisition across a wide range of applications. Compared to other more expensive remote-sensing technology, DJI Phantom series SUA provide a trade-off between cost, sensor quality, functionality and portability. Because of the significant interest in such systems, rigorous accuracy assessment of metric performance is crucial. This research investigates the capabilities of the Phantom 4 Pro (P4P) and the recently launched Phantom 4 RTK (P4RTK) SUA through both laboratory and in-situ assessments with multi-scale photogrammetric blocks. The study adopts self-calibrating bundle adjustments from conventional photogrammetry and from a Structure-from-Motion (SfM)-photogrammetric approach. Both systems deliver planimetric and vertical absolute accuracies of better than one and two pixels ground sampling distance, respectively, against independent check points. This can be achieved if the imaging network configuration includes a mixed range of nadir and oblique imagery and several ground control points are established as reference information. Ongoing analysis is investigating the strength of all bundle adjustment solutions. It is also evaluating the GNSS capabilities of the P4RTK SUA after post-processing raw observations of its trajectory. Findings from a comprehensive accuracy assessment can support non-experts in designing the pre-flight photogrammetric data acquisition plan and aid understanding of the performance of such popular off-the-shelf SUA.</p>

APA, Harvard, Vancouver, ISO, and other styles

12

Hauck, Sven R., Alexander Kupferthaler, Marlies Stelzmüller, Wolf Eilenberg, Marek Ehrlich, Christoph Neumayer, Florian Wolf, Christian Loewe, and Martin A. Funovics. "Endovascular Stent-Graft Repair of the Ascending Aorta: Assessment of a Specific Novel Stent-Graft Design in Phantom, Cadaveric, and Clinical Application." CardioVascular and Interventional Radiology 44, no. 9 (June 27, 2021): 1448–55. http://dx.doi.org/10.1007/s00270-021-02859-5.

Full text

Abstract:

Abstract Purpose To test a stent-graft specifically designed for the ascending aorta in phantom, cadaver, and clinical application, and to measure deployment accuracy to overcome limitations of existing devices. Methods A stent-graft has been designed with support wires to fixate the apices toward the inner curvature, thereby eliminating the forward movement of the proximal end which can happen with circumferential tip capture systems. The device was deployed in three aortic phantoms, and in four cadavers, deployment precision was measured. Subsequently, the device was implanted in a patient to exclude a pseudoaneurysm originating from the distal anastomosis after ascending aortic replacement. Results The stent-grafts were successfully deployed in all phantoms and cadavers. Deployment accuracy of the proximal end of the stent-graft was within 1 mm proximally and 14 mm distally to the intended landing zone on the inner curvature, and 2–8 mm distal to the intended landing zone on the outer curvature. In clinical application, the pseudoaneurysm could be successfully excluded without complications. Conclusion The novel stent-graft design promises accurate placement in the ascending aorta. The differential deployment of the apices at the inner and outer curvatures allows deployment perpendicular to the aortic axis. Level of Evidence No level of evidence.

APA, Harvard, Vancouver, ISO, and other styles

13

Krell, Gerald, Nazila Saeid Nezhad, Mathias Walke, Ayoub Al-Hamadi, and Günther Gademann. "Assessment of Iterative Closest Point Registration Accuracy for Different Phantom Surfaces Captured by an Optical 3D Sensor in Radiotherapy." Computational and Mathematical Methods in Medicine 2017 (2017): 1–13. http://dx.doi.org/10.1155/2017/2938504.

Full text

Abstract:

An optical 3D sensor provides an additional tool for verification of correct patient settlement on a Tomotherapy treatment machine. The patient’s position in the actual treatment is compared with the intended position defined in treatment planning. A commercially available optical 3D sensor measures parts of the body surface and estimates the deviation from the desired position without markers. The registration precision of the in-built algorithm and of selected ICP (iterative closest point) algorithms is investigated on surface data of specially designed phantoms captured by the optical 3D sensor for predefined shifts of the treatment table. A rigid body transform is compared with the actual displacement to check registration reliability for predefined limits. The curvature type of investigated phantom bodies has a strong influence on registration result which is more critical for surfaces of low curvature. We investigated the registration accuracy of the optical 3D sensor for the chosen phantoms and compared the results with selected unconstrained ICP algorithms. Safe registration within the clinical limits is only possible for uniquely shaped surface regions, but error metrics based on surface normals improve translational registration. Large registration errors clearly hint at setup deviations, whereas small values do not guarantee correct positioning.

APA, Harvard, Vancouver, ISO, and other styles

14

Finucane, Ciara M., Iain Murray, Jane K. Sosabowski, Julie M. Foster, and Stephen J. Mather. "Quantitative Accuracy of Low-Count SPECT Imaging in Phantom and In Vivo Mouse Studies." International Journal of Molecular Imaging 2011 (March 16, 2011): 1–8. http://dx.doi.org/10.1155/2011/197381.

Full text

Abstract:

We investigated the accuracy of a single photon emission computed tomography (SPECT) system in quantifying a wide range of radioactivity concentrations using different scan times in both phantom and animal models. A phantom containing various amounts of In-111 or Tc-99m was imaged until the activity had decayed close to background levels. Scans were acquired for different durations, employing different collimator pinhole sizes. VOI analysis was performed to quantify uptake in the images and the values compared to the true activity. The phantom results were then validated in tumour-bearing mice. The use of an appropriate calibration phantom and disabling of a background subtraction feature meant that absolute errors were within 12% of the true activity. Furthermore, a comparison of in vivo imaging and biodistribution studies in mice showed a correlation of 0.99 for activities over the 200 kBq to 5 MBq range. We conclude that the quantitative information provided by the NanoSPECT camera is accurate and allows replacement of dissection studies for assessment of radiotracer biodistribution in mouse models.

APA, Harvard, Vancouver, ISO, and other styles

15

Cercenelli, Laura, Marina Carbone, Sara Condino, Fabrizio Cutolo, Emanuela Marcelli, Achille Tarsitano, Claudio Marchetti, Vincenzo Ferrari, and Giovanni Badiali. "The Wearable VOSTARS System for Augmented Reality-Guided Surgery: Preclinical Phantom Evaluation for High-Precision Maxillofacial Tasks." Journal of Clinical Medicine 9, no. 11 (November 5, 2020): 3562. http://dx.doi.org/10.3390/jcm9113562.

Full text

Abstract:

Background: In the context of guided surgery, augmented reality (AR) represents a groundbreaking improvement. The Video and Optical See-Through Augmented Reality Surgical System (VOSTARS) is a new AR wearable head-mounted display (HMD), recently developed as an advanced navigation tool for maxillofacial and plastic surgery and other non-endoscopic surgeries. In this study, we report results of phantom tests with VOSTARS aimed to evaluate its feasibility and accuracy in performing maxillofacial surgical tasks. Methods: An early prototype of VOSTARS was used. Le Fort 1 osteotomy was selected as the experimental task to be performed under VOSTARS guidance. A dedicated set-up was prepared, including the design of a maxillofacial phantom, an ad hoc tracker anchored to the occlusal splint, and cutting templates for accuracy assessment. Both qualitative and quantitative assessments were carried out. Results: VOSTARS, used in combination with the designed maxilla tracker, showed excellent tracking robustness under operating room lighting. Accuracy tests showed that 100% of Le Fort 1 trajectories were traced with an accuracy of ±1.0 mm, and on average, 88% of the trajectory’s length was within ±0.5 mm accuracy. Conclusions: Our preliminary results suggest that the VOSTARS system can be a feasible and accurate solution for guiding maxillofacial surgical tasks, paving the way to its validation in clinical trials and for a wide spectrum of maxillofacial applications.

APA, Harvard, Vancouver, ISO, and other styles

16

Sapin, E., K. Briot, S. Kolta, P. Gravel, W. Skalli, C. Roux, and D. Mitton. "Bone mineral density assessment using the EOS® low-dose X-ray device: A feasibility study." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 222, no. 8 (November 1, 2008): 1263–71. http://dx.doi.org/10.1243/09544119jeim450.

Full text

Abstract:

To predict bone strength in the case of osteoporosis, it could be a real benefit to assess the three-dimensional (3D) geometry and the bone mineral density (BMD) with a single low-dose X-ray device, such as the EOS system (Biospace Med, Paris, France). EOS 3D reconstructions of the spine have already been validated. Thus, this study aims at evaluating the accuracy of this low-dose system as a densitometer first ex vivo. The European Spine Phantom (ESP) (number 129) was scanned ten times using both the EOS and a Hologic device (Hologic, Inc., Massachusetts, USA). Accuracy was given by the sum of the systematic error (difference between BMDs assessed and true values given by the phantom manufacturer) and the random error (coefficient of variation). EOS BMDs and Hologic BMDs of 41 ex-vivo vertebrae were calculated and compared. The reproducibility of the method evaluating the EOS BMD was assessed giving the coefficient of variation of three measurements of the 41 vertebrae. The accuracy of the EOS system is below 5.2 per cent, versus 7.2 per cent for the Hologic system in the same conditions. EOS BMDs are significantly higher than Hologic BMDs, but they are strongly correlated. The reproducibility of the method of assessment is equal to 0.95 per cent. The EOS system is accurate for ex-vivo BMD assessments, which is promising regarding the use of this new system to predict vertebral strength.

APA, Harvard, Vancouver, ISO, and other styles

17

Kashani, Rojano, Martina Hub, Marc L. Kessler, and James M. Balter. "Technical note: A physical phantom for assessment of accuracy of deformable alignment algorithms." Medical Physics 34, no. 7 (June 13, 2007): 2785–88. http://dx.doi.org/10.1118/1.2739812.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Zani, M., L. Marrazzo, S. Calusi, C. Talamonti, S. Scoccianti, D. Greto, L. Livi, and S. Pallotta. "EP-2090 Helical tomography radiation therapy for multiple brain lesions: in-phantom accuracy assessment." Radiotherapy and Oncology 133 (April 2019): S1154—S1155. http://dx.doi.org/10.1016/s0167-8140(19)32510-1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Dorward, Neil L., Olaf Alberti, James D. Palmer, Neil D. Kitchen, and David G. T. Thomas. "Accuracy of true frameless stereotaxy: in vivo measurement and laboratory phantom studies." Journal of Neurosurgery 90, no. 1 (January 1999): 160–68. http://dx.doi.org/10.3171/jns.1999.90.1.0160.

Full text

Abstract:

✓ The authors present the results of accuracy measurements, obtained in both laboratory phantom studies and an in vivo assessment, for a technique of frameless stereotaxy. An instrument holder was developed to facilitate stereotactic guidance and enable introduction of frameless methods to traditional frame-based procedures. The accuracy of frameless stereotaxy was assessed for images acquired using 0.5-tesla or 1.5-tesla magnetic resonance (MR) imaging or 2-mm axial, 3-mm axial, or 3-mm helical computerized tomography (CT) scanning. A clinical series is reported in which biopsy samples were obtained using a frameless stereotactic procedure, and the accuracy of these procedures was assessed using postoperative MR images and image fusion.The overall mean error of phantom frameless stereotaxy was found to be 1.3 mm (standard deviation [SD] 0.6 mm). The mean error for CT-directed frameless stereotaxy was 1.1 mm (SD 0.5 mm) and that for MR image—directed procedures was 1.4 mm (SD 0.7 mm). The CT-guided frameless stereotaxy was significantly more accurate than MR image—directed stereotaxy (p = 0.0001). In addition, 2-mm axial CT-guided stereotaxy was significantly more accurate than 3-mm axial CT-guided stereotaxy (p = 0.025). In the clinical series of 21 frameless stereotactically obtained biopsies, all specimens yielded the appropriate diagnosis and no complications ensued. Early postoperative MR images were obtained in 16 of these cases and displacement of the biopsy site from the intraoperative target was determined by fusion of pre- and postoperative image data sets. The mean in vivo linear error of frameless stereotactic biopsy sampling was 2.3 mm (SD 1.9 mm). The mean in vivo Euclidean error was 4.8 mm (SD 2 mm). The implications of these accuracy measurements and of error in stereotaxy are discussed.

APA, Harvard, Vancouver, ISO, and other styles

20

Pérez Curbelo, Javier, Rogelio Diaz Moreno, and Roberto Caballero Pinelo. "Test cases for commissioning an add-on micro multi-leaf collimator Apex for stereotactic radiosurgery treatments." Revista Brasileira de Física Médica 14 (December 6, 2020): 533. http://dx.doi.org/10.29384/rbfm.2020.v14.19849001533.

Full text

Abstract:

Two comprehensive test cases are presented for dosimetric commissioning of a radiosurgery system, in a hospital where dedicated phantoms are not available. The system consisted of an Elekta Precise linear accelerator, an Apex micro multi-leaf collimator, and a Monaco treatment planning system (TPS). The purpose of Test I was to assess the dose accuracy with coplanar arc beams. Test II was an end-to-end type test, a rigid Leksell stereotactic frame was fixed to a watermelon phantom and Ergo++ TPS was used for stereotactic coordinates definition. The purpose of Test II was to assess the dose accuracy with non-coplanar arc beams and the influence of geometrical accuracy in the whole process. Ionization chambers were used for dose measurements. Results of Test I showed that discrepancies below 1% are achievable, while results of Test II allowed detection of geometric shifts < 1 mm with dose discrepancies lower than 1%. To the best of our knowledge, there are not published works reporting test cases for commissioning a stereotactic radiosurgery system like the one tested in this work. The designed test cases showed adequacy for assessment of TPS accuracy in complex treatment configurations, like those used in stereotactic radiosurgery.

APA, Harvard, Vancouver, ISO, and other styles

21

Taddia, Yuri, Laura González-García, Elena Zambello, and Alberto Pellegrinelli. "Quality Assessment of Photogrammetric Models for Façade and Building Reconstruction Using DJI Phantom 4 RTK." Remote Sensing 12, no. 19 (September 24, 2020): 3144. http://dx.doi.org/10.3390/rs12193144.

Full text

Abstract:

Aerial photogrammetry by Unmanned Aerial Vehicles (UAVs) is a widespread method to perform mapping tasks with high-resolution to reconstruct three-dimensional (3D) building and façade models. However, the survey of Ground Control Points (GCPs) represents a time-consuming task, while the use of Real-Time Kinematic (RTK) drones allows for one to collect camera locations with an accuracy of a few centimeters. DJI Phantom 4 RTK (DJI-P4RTK) combines this with the possibility to acquire oblique images in stationary conditions and it currently represents a versatile drone widely used from professional users together with commercial Structure-from-Motion software, such as Agisoft Metashape. In this work, we analyze the architectural application of this drone to the photogrammetric modeling of a building with particular regard to metric survey specifications for cultural heritage for 1:20, 1:50, 1:100, and 1:200 scales. In particular, we designed an accuracy assessment test signalizing 109 points, surveying them with total station and adjusting the measurements through a network approach in order to achieve millimeter-level accuracy. Image datasets with a designed Ground Sample Distance (GSD) of 2 mm were acquired in Network RTK (NRTK) and RTK modes in manual piloting and processed both as single façades (S–F) and as an overall block (4–F). Subsequently, we compared the results of photogrammetric models generated in Agisoft Metashape to the Signalized Point (SP) coordinates. The results highlight the importance of processing an overall photogrammetric block, especially whenever part of camera locations exhibited a poorer accuracy due to multipath effects. No significant differences were found between the results of network real-time kinematic (NRTK) and real-time kinematic (RTK) datasets. Horizontal residuals were generally comparable to GNSS accuracy in NRTK/RTK mode, while vertical residuals were found to be affected by an offset of about 5 cm. We introduced an external GCP or used one SP per façade as GCP, assuming a poorer camera location accuracy at the same time, in order to fix this issue and comply with metric survey specifications for the widest architectural scale range. Finally, both S–F and 4–F projects satisfied the metric survey requirements of a scale of 1:50 in at least one of the approaches tested.

APA, Harvard, Vancouver, ISO, and other styles

22

Kudo, Kohsuke, Soren Christensen, Makoto Sasaki, Leif Østergaard, Hiroki Shirato, Kuniaki Ogasawara, Max Wintermark, and Steven Warach. "Accuracy and Reliability Assessment of CT and MR Perfusion Analysis Software Using a Digital Phantom." Radiology 267, no. 1 (April 2013): 201–11. http://dx.doi.org/10.1148/radiol.12112618.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Novotný, J., J. Novotný, J. Vymazal, R. Liščák, and V. Vladyka. "Assessment of the Accuracy of Stereotactic Target Localization Using Magnetic Resonance Imaging: A Phantom Study." Journal of Radiosurgery 1, no. 2 (June 1998): 99–111. http://dx.doi.org/10.1023/b:jora.0000010893.37324.87.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Mirzaalian Dastjerdi, Houman, Dominique Töpfer, Stefan J. Rupitsch, and Andreas Maier. "Measuring Surface Area of Skin Lesions with 2D and 3D Algorithms." International Journal of Biomedical Imaging 2019 (January 15, 2019): 1–9. http://dx.doi.org/10.1155/2019/4035148.

Full text

Abstract:

Purpose. The treatment of skin lesions of various kinds is a common task in clinical routine. Apart from wound care, the assessment of treatment efficacy plays an important role. In this paper, we present a new approach to measure the skin lesion surface in two and three dimensions. Methods. For the 2D approach, a single photo containing a flexible paper ruler is taken. After semi-automatic segmentation of the lesion, evaluation is based on local scale estimation using the ruler. For the 3D approach, reconstruction is based on Structure from Motion. Roughly outlining the region of interest around the lesion is required for both methods. Results. The measurement evaluation was performed on 117 phantom images and five phantom videos for 2D and 3D approach, respectively. We found an absolute error of 0.99±1.18 cm2 and a relative error 9.89± 9.31% for 2D. These errors are <1 cm2 and <5% for five test phantoms in our 3D case. As expected, the error of 2D surface area measurement increased by approximately 10% for wounds on the bent surface compared to wounds on the flat surface. Using our method, the only user interaction is to roughly outline the region of interest around the lesion. Conclusions. We developed a new wound segmentation and surface area measurement technique for skin lesions even on a bent surface. The 2D technique provides the user with a fast, user-friendly segmentation and measurement tool with reasonable accuracy for home care assessment of treatment. For 3D only preliminary results could be provided. Measurements were only based on phantoms and have to be repeated with real clinical data.

APA, Harvard, Vancouver, ISO, and other styles

25

Mai, Jerome J., Fermin A. Lupotti, and Michael F. Insana. "Vascular Elasticity from Regional Displacement Estimates." Ultrasonic Imaging 25, no. 3 (July 2003): 171–92. http://dx.doi.org/10.1177/016173460302500305.

Full text

Abstract:

A recently-developed ultrasonic technique for measuring elastic properties of vascular tissue is evaluated using computer simulations, phantom and in vivo human measurements. A time sequence of displacement images is measured over the cardiac cycle to describe the spatial and temporal patterns of deformation surrounding arteries. This information is combined with a mathematical model to estimate an elastic modulus. Computer simulations of ultrasonic echo data from deformed tissues are analyzed to define a signal processing approach. Measurements in flow phantoms, with and without vessel-simulating channel walls, provide an assessment of the accuracy and precision of this technique for vascular elasticity measurements. Finally, preliminary results for the stiffness index (β) in a study group of healthy human volunteers are compared with previously reported data. We find that careful measurement technique is required to control measurement variability.

APA, Harvard, Vancouver, ISO, and other styles

26

Vakharia, Vejay N., Roman Rodionov, Andrew W. McEvoy, Anna Miserocchi, Rachel Sparks, Aidan G. O’Keeffe, Sebastien Ourselin, and John S. Duncan. "Improving patient safety during introduction of novel medical devices through cumulative summation analysis." Journal of Neurosurgery 130, no. 1 (February 2018): 213–19. http://dx.doi.org/10.3171/2017.8.jns17936.

Full text

Abstract:

OBJECTIVEThe aim of this study was to implement cumulative summation (CUSUM) analysis as an early-warning detection and quality assurance system for preclinical testing of the iSYS1 novel robotic trajectory guidance system.METHODSAnatomically accurate 3D-printed skull phantoms were created for 3 patients who underwent implantation of 21 stereoelectroencephalography electrodes by surgeons using the current standard of care (frameless technique). Implantation schema were recreated using the iSYS1 system, and paired accuracy measures were compared with the previous frameless implantations. Entry point, target point, and implantation angle accuracy were measured on postimplantation CT scans. CUSUM analysis was undertaken prospectively.RESULTSThe iSYS1 trajectory guidance system significantly improved electrode entry point accuracies from 1.90 ± 0.96 mm (mean ± SD) to 0.76 ± 0.57 mm (mean ± SD) without increasing implantation risk. CUSUM analysis was successful as a continuous measure of surgical performance and acted as an early-warning detection system. The surgical learning curve, although minimal, showed improvement after insertion of the eighth electrode.CONCLUSIONSThe iSYS1 trajectory guidance system did not show any increased risk during phantom preclinical testing when used by neurosurgeons who had no experience with its use. CUSUM analysis is a simple technique that can be applied to all stages of the IDEAL (idea, development, exploration, assessment) framework as an extra patient safety mechanism. Further clinical trials are required to prove the efficacy of the device.

APA, Harvard, Vancouver, ISO, and other styles

27

Wang, Y., H. Jacobsson, S. H. Jacobson, S. Kimiaei, and S. A. Larsson. "A 3-D Method for Delineation of Activity Distributions and Assessment of Functional Organ Volumes with Spect." Acta Radiologica 36, no. 4-6 (July 1995): 536–44. http://dx.doi.org/10.1177/028418519503600443.

Full text

Abstract:

The distribution volume of an organ may have a clinical impact in many cases and various methods have been designed to make volume assessments. In this paper, we describe a new method for delineation of the distribution outline and volume determination. The method is based on smoothing, differentiation, image relaxation and voxel counting of single photon emission computer tomography (SPECT) image sets with 3-D operators. A special routine corrects for the inherent thickness of the voxel-based outline. Phantom experiments, using a SPECT system with LEGP-collimator and a 64×64 acquisition matrix with 6.3×6.3 mm2 pixel size, demonstrated good correlation between the measured and the true volumes. For volumes larger than 120 cc the correlation coefficient was 0.9999 with SE 1.0 cc and an average relative deviation of 0.49%. For volumes below 120 cc, the accuracy was impaired due to low resolution power. By improving the system spatial resolution with an LEHR-collimator and a smaller pixel-size (4.1×4.1 mm2), good accuracy was achieved also for volumes in the range from 3 to 120 cc. Measurements of 15 differently shaped phantoms of volumes between 3 and 104 cc demonstrated high correlation between measured and true volumes: R=0.9921 and SE=0.74 cc (5.3%). For volumes as small as 3 and 5 cc, the difference between the true and the assessed volume was 0.6 cc. The reproducibility of the method was within 3% for volumes above 120 cc and within 7% for volumes below. Due to this accuracy, we conclude that the method can be applied for various clinical routine and research applications using SPECT.

APA, Harvard, Vancouver, ISO, and other styles

28

Arshed, Waheed, Khalid Mahmood, Ikramullah Qazi, Asad Ullah, Perveen Akhter, Salman Ahmad, and Zeeshan Jamil. "A comparison of in-air and in-water calibration of a dosimetry system used for radiation dose assessment in cancer therapy." Nuclear Technology and Radiation Protection 25, no. 1 (2010): 51–54. http://dx.doi.org/10.2298/ntrp1001051a.

Full text

Abstract:

An accurate calibration of the therapy level radiation dosimetry system has a pivotal role in the accuracy of dose delivery to cancer patients. The two methods used for obtaining a tissue equivalent calibration of the system: air kerma calibration and its conversion to a tissue equivalent value (absorbed dose to water) and direct calibration of the system in a water phantom, have been compared for identical irradiation geometry. It was found that the deviation between the two methods remained within a range of 0% to ?1.7% for the PTW UNIDOS dosimetry system. This means that although the recommended method is in-water calibration, under exceptional circumstances, in-air calibration may be used as well.

APA, Harvard, Vancouver, ISO, and other styles

29

Zhang, Chen, Robin Bruggink, Frank Baan, Ewald Bronkhorst, Thomas Maal, Hong He, and Edwin M. Ongkosuwito. "A new segmentation algorithm for measuring CBCT images of nasal airway: a pilot study." PeerJ 7 (January 28, 2019): e6246. http://dx.doi.org/10.7717/peerj.6246.

Full text

Abstract:

Background Three-dimensional (3D) modeling of the nasal airway space is becoming increasingly important for assessment in breathing disorders. Processing cone beam computed tomography (CBCT) scans of this region is complicated, however, by the intricate anatomy of the sinuses compared to the simpler nasopharynx. A gold standard for these measures also is lacking. Previous work has shown that software programs can vary in accuracy and reproducibility outcomes of these measurements. This study reports the reproducibility and accuracy of an algorithm, airway segmentor (AS), designed for nasal airway space analysis using a 3D printed anthropomorphic nasal airway model. Methods To test reproducibility, two examiners independently used AS to edit and segment 10 nasal airway CBCT scans. The intra- and inter-examiner reproducibility of the nasal airway volume was evaluated using paired t-tests and intraclass correlation coefficients. For accuracy testing, the CBCT data for pairs of nasal cavities were 3D printed to form hollow shell models. The water-equivalent method was used to calculate the inner volume as the gold standard, and the models were then embedded into a dry human skull as a phantom and subjected to CBCT. AS, along with the software programs MIMICS 19.0 and INVIVO 5, was applied to calculate the inner volume of the models from the CBCT scan of the phantom. The accuracy was reported as a percentage of the gold standard. Results The intra-examiner reproducibility was high, and the inter-examiner reproducibility was clinically acceptable. AS and MIMICS presented accurate volume calculations, while INVIVO 5 significantly overestimated the mockup of the nasal airway volume. Conclusion With the aid of a 3D printing technique, the new algorithm AS was found to be a clinically reliable and accurate tool for the segmentation and reconstruction of the nasal airway space.

APA, Harvard, Vancouver, ISO, and other styles

30

Orman, J., Ö. Gürvit, and D. Bartz. "Accurate Volumetric Measurements of Anatomical Cavities." Methods of Information in Medicine 43, no. 04 (2004): 331–35. http://dx.doi.org/10.1055/s-0038-1633876.

Full text

Abstract:

Summary Objectives: The volumetric assessment of anatomical cavities is of high relevance for various applications in medicine. Based on 3D scanning (i.e., CT) of these cavities, the volume can be determined by counting the volume elements of a segmentation of that cavity. Unfortunately, elements on the boundary of the segmentation require special treatment to obtain accurate volumetric measurements. In this paper, we propose a novel technique that in particular increases the accuracy of the volume estimation for the boundary elements of segmented anatomical objects. Methods: Based on a 3D segmentation of an anatomical cavity, we recursively subdivide boundary volume elements into a set of simple situations, where the volume can be estimated easily. Results: We performed volumetric measurements on seven datasets of phantom models made of plexiglass (see Fig. 1) scanned by a biplane angiography unit and assessed the quality of our method by comparing the measured volume by our novel method and by the fluid required to fill the phantom cavities. Conclusions: Our method calculates a significantly more accurate volume of the segmented cavities than previous methods. Nevertheless, it is only slightly more computationally expensive.

APA, Harvard, Vancouver, ISO, and other styles

31

Kim, Hyeon-Sik, Byeong-il Lee, and Jae-Sung Ahn. "Assessment of MicroPET Image Quality Based on Reconstruction Methods and Post-Filtering." Applied Sciences 11, no. 18 (September 18, 2021): 8707. http://dx.doi.org/10.3390/app11188707.

Full text

Abstract:

The accuracy of positron emission tomography (PET) imaging is hampered by the partial volume effect (PVE), which causes image blurring and sampling. The PVE produces spillover phenomena, making PET analysis difficult. Generally, the PVE values vary based on reconstruction methods and filtering. Thus, selection of the proper reconstruction and filtering method can ensure accurate and high-quality PET images. This study compared the values of factors (recovery coefficient (RC), uniformity, and spillover ratio (SOR)) associated with different reconstruction and post-filtering methods using a mouse image quality phantom (NEMA NU 4), and we present an effective approach for microPET images. The PET images were obtained using a microPET scanner (Inveon, Siemens Medical Solutions, Malvern, PA, USA). PET data were reconstructed and/or post-filtered. For tumors smaller than 3 mm, iterative reconstruction methods provided better image quality. For tumor sizes bigger than 3 mm, reconstruction methods without post-filtering showed better results.

APA, Harvard, Vancouver, ISO, and other styles

32

Ren, J., A. McNiven, and D. Letourneau. "SU-E-T-161: Assessment of Phantom Positioning Accuracy in IMRT Quality Assurance: Insert Design and Implementation." Medical Physics 40, no. 6Part13 (June 2013): 241. http://dx.doi.org/10.1118/1.4814596.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Sasaki, Makoto, Kohsuke Kudo, Timothé Boutelier, Fabrice Pautot, Soren Christensen, Ikuko Uwano, Jonathan Goodwin, Satomi Higuchi, Kenji Ito, and Fumio Yamashita. "Assessment of the accuracy of a Bayesian estimation algorithm for perfusion CT by using a digital phantom." Neuroradiology 55, no. 10 (July 14, 2013): 1197–203. http://dx.doi.org/10.1007/s00234-013-1237-7.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Mabray, Marc C., Sanjit Datta, Prasheel V. Lillaney, Teri Moore, Sonja Gehrisch, Jason F. Talbott, Michael R. Levitt, Basavaraj V. Ghodke, Paul S. Larson, and Daniel L. Cooke. "Accuracy of flat panel detector CT with integrated navigational software with and without MR fusion for single-pass needle placement." Journal of NeuroInterventional Surgery 8, no. 7 (June 5, 2015): 731–35. http://dx.doi.org/10.1136/neurintsurg-2015-011799.

Full text

Abstract:

PurposeFluoroscopic systems in modern interventional suites have the ability to perform flat panel detector CT (FDCT) with navigational guidance. Fusion with MR allows navigational guidance towards FDCT occult targets. We aim to evaluate the accuracy of this system using single-pass needle placement in a deep brain stimulation (DBS) phantom.Materials and methodsMR was performed on a head phantom with DBS lead targets. The head phantom was placed into fixation and FDCT was performed. FDCT and MR datasets were automatically fused using the integrated guidance system (iGuide, Siemens). A DBS target was selected on the MR dataset. A 10 cm, 19 G needle was advanced by hand in a single pass using laser crosshair guidance. Radial error was visually assessed against measurement markers on the target and by a second FDCT. Ten needles were placed using CT-MR fusion and 10 needles were placed without MR fusion, with targeting based solely on FDCT and fusion steps repeated for every pass.ResultsMean radial error was 2.75±1.39 mm as defined by visual assessment to the centre of the DBS target and 2.80±1.43 mm as defined by FDCT to the centre of the selected target point. There were no statistically significant differences in error between MR fusion and non-MR guided series.ConclusionsSingle pass needle placement in a DBS phantom using FDCT guidance is associated with a radial error of approximately 2.5–3.0 mm at a depth of approximately 80 mm. This system could accurately target sub-centimetre intracranial lesions defined on MR.

APA, Harvard, Vancouver, ISO, and other styles

35

De Landro, Martina, Jacopo Ianniello, Maxime Yon, Alexey Wolf, Bruno Quesson, Emiliano Schena, and Paola Saccomandi. "Fiber Bragg Grating Sensors for Performance Evaluation of Fast Magnetic Resonance Thermometry on Synthetic Phantom." Sensors 20, no. 22 (November 12, 2020): 6468. http://dx.doi.org/10.3390/s20226468.

Full text

Abstract:

The increasing recognition of minimally invasive thermal treatment of tumors motivate the development of accurate thermometry approaches for guaranteeing the therapeutic efficacy and safety. Magnetic Resonance Thermometry Imaging (MRTI) is nowadays considered the gold-standard in thermometry for tumor thermal therapy, and assessment of its performances is required for clinical applications. This study evaluates the accuracy of fast MRTI on a synthetic phantom, using dense ultra-short Fiber Bragg Grating (FBG) array, as a reference. Fast MRTI is achieved with a multi-slice gradient-echo echo-planar imaging (GRE-EPI) sequence, allowing monitoring the temperature increase induced with a 980 nm laser source. The temperature distributions measured with 1 mm-spatial resolution with both FBGs and MRTI were compared. The root mean squared error (RMSE) value obtained by comparing temperature profiles showed a maximum error of 1.2 °C. The Bland-Altman analysis revealed a mean of difference of 0.1 °C and limits of agreement 1.5/−1.3 °C. FBG sensors allowed to extensively assess the performances of the GRE-EPI sequence, in addition to the information on the MRTI precision estimated by considering the signal-to-noise ratio of the images (0.4 °C). Overall, the results obtained for the GRE-EPI fully satisfy the accuracy (~2 °C) required for proper temperature monitoring during thermal therapies.

APA, Harvard, Vancouver, ISO, and other styles

36

Gutjahr, Ralf, Robbert C. Bakker, Feiko Tiessens, Sebastiaan A. van Nimwegen, Bernhard Schmidt, and Johannes Frank Wilhelmus Nijsen. "Quantitative dual-energy CT material decomposition of holmium microspheres: local concentration determination evaluated in phantoms and a rabbit tumor model." European Radiology 31, no. 1 (August 7, 2020): 139–48. http://dx.doi.org/10.1007/s00330-020-07092-1.

Full text

Abstract:

Abstract Objectives The purpose of this study was to assess the feasibility of dual-energy CT-based material decomposition using dual-X-ray spectra information to determine local concentrations of holmium microspheres in phantoms and in an animal model. Materials and methods A spectral calibration phantom with a solution containing 10 mg/mL holmium and various tube settings was scanned using a third-generation dual-energy CT scanner to depict an energy-dependent and material-dependent enhancement vectors. A serial dilution of holmium (microspheres) was quantified by spectral material decomposition and compared with known holmium concentrations. Subsequently, the feasibility of the spectral material decomposition was demonstrated in situ in three euthanized rabbits with injected (radioactive) holmium microspheres. Results The measured CT values of the holmium solutions scale linearly to all measured concentrations and tube settings (R2 = 1.00). Material decomposition based on CT acquisitions using the tube voltage combinations of 80/150 Sn kV or 100/150 Sn kV allow the most accurate quantifications for concentrations down to 0.125 mg/mL holmium. Conclusion Dual-energy CT facilitates image-based material decomposition to detect and quantify holmium microspheres in phantoms and rabbits. Key Points • Quantification of holmium concentrations based on dual-energy CT is obtained with good accuracy. • The optimal tube-voltage pairs for quantifying holmium were 80/150 Sn kV and 100/150 Sn kV using a third-generation dual-source CT system. • Quantification of accumulated holmium facilitates the assessment of local dosimetry for radiation therapies.

APA, Harvard, Vancouver, ISO, and other styles

37

Elangovan, Hariprashanth, Wei Yao, and Kypros Nicolaides. "A Multimodality Navigation System for Endoscopic Fetal Surgery: A Phantom Case Study for Congenital Diaphragmatic Hernia." Surgical Innovation 26, no. 1 (November 28, 2018): 27–36. http://dx.doi.org/10.1177/1553350618813244.

Full text

Abstract:

This article presents a multi-modality tracking and navigation system achieved by merging optical tracking and ultrasound imaging into a novel navigation software to help in surgical pre-planning and real-time target setting and guidance. Fetal surgeries require extensive experience in coordination of hand-eye-ultrasound-surgical equipment, knowledge, and precise assessment of relative anatomy. While there are navigation systems available for similar constrained working spaces in arthroscopic and cardiovascular procedures, fetal minimally invasive surgery does not yet have a dedicated navigation platform capable of supporting robotic instruments that can be adapted to the set of unique procedures. This article discusses the testing of the novel multi-modality navigation system in a phantom environment developed for this purpose. The outcomes suggest that the subjects demonstrated an increase in average reaching accuracy by about 60% and an overall reduction in time taken by 33.6%. They also showed higher levels of confidence in reaching the targets, which was visualised from the pattern of trajectory of movements during the procedure. To evaluate the navigation system, a phantom surgical environment was found necessary. Therefore, the article also discusses the details of the development of a fetal phantom environment for congenital diaphragmatic hernia for surgical testing, evaluation, and training. A surgical procedure was conducted on the phantom using the proposed tracking navigation system and using only ultrasound.

APA, Harvard, Vancouver, ISO, and other styles

38

Lee, Chang-Lae, Junyoung Park, Sangnam Nam, Jiyoung Choi, Yuna Choi, Sangmin Lee, Kyoung-Yong Lee, and Minkook Cho. "Metal artifact reduction and tumor detection using photon-counting multi-energy computed tomography." PLOS ONE 16, no. 3 (March 5, 2021): e0247355. http://dx.doi.org/10.1371/journal.pone.0247355.

Full text

Abstract:

Metal artifacts are considered a major challenge in computed tomography (CT) as these adversely affect the diagnosis and treatment of patients. Several approaches have been developed to address this problem. The present study explored the clinical potential of a novel photon-counting detector (PCD) CT system in reducing metal artifacts in head CT scans. In particular, we studied the recovery of an oral tumor region located under metal artifacts after correction. Three energy thresholds were used to group data into three bins (bin 1: low-energy, bin 2: middle-energy, and bin 3: high-energy) in the prototype PCD CT system. Three types of physical phantoms were scanned on the prototype PCD CT system. First, we assessed the accuracy of iodine quantification using iodine phantoms at varying concentrations. Second, we evaluated the performance of material decomposition (MD) and virtual monochromatic images (VMIs) using a multi-energy CT phantom. Third, we designed an ATOM phantom with metal insertions to verify the effect of the proposed metal artifact reduction. In particular, we placed an insertion-mimicking an iodine-enhanced oral tumor in the beam path of metallic objects. Normalized metal artifact reduction (NMAR) was performed for each energy bin image, followed by an image-based MD and VMI reconstruction. Image quality was analyzed quantitatively by contrast-to-noise ratio (CNR) measurements. The results of iodine quantification showed a good match between the true and measured iodine concentrations. Furthermore, as expected, the contrast between iodine and the surrounding material was higher in bin 1 image than in bin 3 image. On the other hand, the bin 3 image of the ATOM phantom showed fewer metal artifacts than the bin 1 image because of the higher photon energy. The result of quantitative assessment demonstrated that the 40-keV VMI (CNR: 20.6 ± 1.2) with NMAR and MD remarkably increased the contrast of the iodine-enhanced region compared with that of the conventional images (CNR: 10.4 ± 0.5) having 30 to 140 keV energy levels. The PCD-based multi-energy CT imaging has immense potential to maximize the contrast of the target tissue and reduce metal artifacts simultaneously. We believe that it would open the door to novel applications for the diagnosis and treatment of several diseases.

APA, Harvard, Vancouver, ISO, and other styles

39

Pearson, J., P. Ruegsegger, J. Dequeker, M. Henley, J. Bright, J. Reeve, W. Kalender, et al. "European semi-anthropomorphic phantom for the cross-calibration of peripheral bone densitometers: assessment of precision accuracy and stability." Bone and Mineral 27, no. 2 (January 1994): 109–20. http://dx.doi.org/10.1016/s0169-6009(08)80213-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Law, M. W. K., J. Yuan, G. G. Lo, A. Y. Ding, O. L. Wong, K. F. Cheng, K. T. Chan, K. Y. Cheung, and S. K. Yu. "PO-0975: Quantitative assessment of 3D geometric accuracy of a 1.5T wide-bore MR-simulator: a phantom study." Radiotherapy and Oncology 115 (April 2015): S518—S519. http://dx.doi.org/10.1016/s0167-8140(15)40967-3.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Toepker, Michael, Christopher L. Schlett, Thomas Irlbeck, Amir A. Mahabadi, Fabian Bamberg, Christiane Leidecker, Patrick Donnelly, and Udo Hoffmann. "Accuracy of dual-source computed tomography in quantitative assessment of low density coronary stenosis—a motion phantom study." European Radiology 20, no. 3 (September 2, 2009): 542–48. http://dx.doi.org/10.1007/s00330-009-1587-z.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

Duan, Yunsuo, Tamer S. Ibrahim, Bradley S. Peterson, Feng Liu, and Alayar Kangarlu. "Assessment of a PML Boundary Condition for Simulating an MRI Radio Frequency Coil." International Journal of Antennas and Propagation 2008 (2008): 1–10. http://dx.doi.org/10.1155/2008/563196.

Full text

Abstract:

Computational methods such as the finite difference time domain (FDTD) play an important role in simulating radiofrequency (RF) coils used in magnetic resonance imaging (MRI). The choice of absorbing boundary conditions affects the final outcome of such studies. We have used FDTD to assess the Berenger's perfectly matched layer (PML) as an absorbing boundary condition for computation of the resonance patterns and electromagnetic fields of RF coils. We first experimentally constructed a high-pass birdcage head coil, measured its resonance pattern, and used it to acquire proton phantom MRI images. We then computed the resonance pattern and field of the coil using FDTD with a PML as an absorbing boundary condition. We assessed the accuracy and efficiency of PML by adjusting the parameters of the PML and comparing the calculated results with measured ones. The optimal PML parameters that produce accurate (comparable to the experimental findings) FDTD calculations are then provided for the birdcage head coil operating at 127.72 MHz, the Larmor frequency of at 3 Tesla (T).

APA, Harvard, Vancouver, ISO, and other styles

43

Ho, Anthony K., Dongshan Fu, Cristian Cotrutz, Steven L. Hancock, Steven D. Chang, Iris C. Gibbs, Calvin R. Maurer, and John R. Adler. "A Study of the Accuracy of CyberKnife Spinal Radiosurgery Using Skeletal Structure Tracking." Operative Neurosurgery 60, suppl_2 (February 1, 2007): ONS—147—ONS—156. http://dx.doi.org/10.1227/01.neu.0000249248.55923.ec.

Full text

Abstract:

Abstract Objective: New technology has enabled the increasing use of radiosurgery to ablate spinal lesions. The first generation of the CyberKnife (Accuray, Inc., Sunnyvale, CA) image-guided radiosurgery system required implanted radiopaque markers (fiducials) to localize spinal targets. A recently developed and now commercially available spine tracking technology called Xsight (Accuray, Inc.) tracks skeletal structures and eliminates the need for implanted fiducials. The Xsight system localizes spinal targets by direct reference to the adjacent vertebral elements. This study sought to measure the accuracy of Xsight spine tracking and provide a qualitative assessment of overall system performance. Methods: Total system error, which is defined as the distance between the centroids of the planned and delivered dose distributions and represents all possible treatment planning and delivery errors, was measured using a realistic, anthropomorphic head-and-neck phantom. The Xsight tracking system error component of total system error was also computed by retrospectively analyzing image data obtained from eleven patients with a total of 44 implanted fiducials who underwent CyberKnife spinal radiosurgery. Results: The total system error of the Xsight targeting technology was measured to be 0.61 mm. The tracking system error component was found to be 0.49 mm. Conclusion: The Xsight spine tracking system is practically important because it is accurate and eliminates the use of implanted fiducials. Experience has shown this technology to be robust under a wide range of clinical circumstances.

APA, Harvard, Vancouver, ISO, and other styles

44

Ginty, Olivia K., John M. Moore, Yuanwei Xu, Wenyao Xia, Satoru Fujii, Daniel Bainbridge, Terry M. Peters, Bob B. Kiaii, and Michael W. A. Chu. "Dynamic Patient-Specific Three-Dimensional Simulation of Mitral Repair." Innovations: Technology and Techniques in Cardiothoracic and Vascular Surgery 13, no. 1 (January 2018): 11–22. http://dx.doi.org/10.1097/imi.0000000000000463.

Full text

Abstract:

Objective Planned mitral repair strategies are generally established from preoperative echocardiography; however, specific details of the repair are often determined intraoperatively. We propose that three-dimensional printed, patient-specific, dynamic mitral valve models may help surgeons plan and trial all the details of a specific patient's mitral repair preoperatively. Methods Using preoperative echocardiography, segmentation, modeling software, and three-dimensional printing, we created dynamic, high-fidelity, patient-specific mitral valve models including the subvalvular apparatus. We assessed the accuracy of 10 patient mitral valve models anatomically and functionally in a heart phantom simulator, both objectively by blinded echocardiographic assessment, and subjectively by two mitral repair experts. After this, we attempted model mitral repair and compared the outcomes with postoperative echocardiography. Results Model measurements were accurate when compared with patients on anterior-posterior diameter, circumference, and anterior leaflet length; however, less accurate on posterior leaflet length. On subjective assessment, Likert scores were high at 3.8 ± 0.4 and 3.4 ± 0.7, suggesting good fidelity of the dynamic model echocardiogram and functional model in the phantom to the preoperative three-dimensional echocardiogram, respectively. Mitral repair was successful in all 10 models with significant reduction in mitral insufficiency. In two models, mitral repair was performed twice, using two different surgical techniques to assess which provided a better outcome. When compared with the actual patient mitral repair outcome, the repaired models compared favorably. Conclusions Complex mitral valve modeling seems to predict an individual patient's mitral anatomy well, before surgery. Further investigation is required to determine whether deliberate preoperative practice can improve mitral repair outcomes.

APA, Harvard, Vancouver, ISO, and other styles

45

Mostardeiro, Thomaz R., Ananya Panda, Robert J. Witte, Norbert G. Campeau, Kiaran P. McGee, Yi Sui, and Aiming Lu. "Whole-brain 3D MR fingerprinting brain imaging: clinical validation and feasibility to patients with meningioma." Magnetic Resonance Materials in Physics, Biology and Medicine 34, no. 5 (May 4, 2021): 697–706. http://dx.doi.org/10.1007/s10334-021-00924-1.

Full text

Abstract:

Abstract Purpose MR fingerprinting (MRF) is a MR technique that allows assessment of tissue relaxation times. The purpose of this study is to evaluate the clinical application of this technique in patients with meningioma. Materials and methods A whole-brain 3D isotropic 1mm3 acquisition under a 3.0T field strength was used to obtain MRF T1 and T2-based relaxometry values in 4:38 s. The accuracy of values was quantified by scanning a quantitative MR relaxometry phantom. In vivo evaluation was performed by applying the sequence to 20 subjects with 25 meningiomas. Regions of interest included the meningioma, caudate head, centrum semiovale, contralateral white matter and thalamus. For both phantom and subjects, mean values of both T1 and T2 estimates were obtained. Statistical significance of differences in mean values between the meningioma and other brain structures was tested using a Friedman’s ANOVA test. Results MR fingerprinting phantom data demonstrated a linear relationship between measured and reference relaxometry estimates for both T1 (r2 = 0.99) and T2 (r2 = 0.97). MRF T1 relaxation times were longer in meningioma (mean ± SD 1429 ± 202 ms) compared to thalamus (mean ± SD 1054 ± 58 ms; p = 0.004), centrum semiovale (mean ± SD 825 ± 42 ms; p < 0.001) and contralateral white matter (mean ± SD 799 ± 40 ms; p < 0.001). MRF T2 relaxation times were longer for meningioma (mean ± SD 69 ± 27 ms) as compared to thalamus (mean ± SD 27 ± 3 ms; p < 0.001), caudate head (mean ± SD 39 ± 5 ms; p < 0.001) and contralateral white matter (mean ± SD 35 ± 4 ms; p < 0.001) Conclusions Phantom measurements indicate that the proposed 3D-MRF sequence relaxometry estimations are valid and reproducible. For in vivo, entire brain coverage was obtained in clinically feasible time and allows quantitative assessment of meningioma in clinical practice.

APA, Harvard, Vancouver, ISO, and other styles

46

Nazeer, Muhammad Rizwan, Farhan Raza Khan, and Munawwar Rahman. "In vitro assessment of the accuracy of extraoral periapical radiography in root length determination." European Journal of Dentistry 10, no. 01 (January 2016): 034–39. http://dx.doi.org/10.4103/1305-7456.175681.

Full text

Abstract:

ABSTRACT Objective: To determine the accuracy of extra oral periapical radiography in obtaining root length by comparing it with the radiographs obtained from standard intraoral approach and extended distance intraoral approach. Materials and Methods: It was an in vitro, comparative study conducted at the dental clinics of Aga Khan University Hospital. ERC exemption was obtained for this work, ref number 3407Sur-ERC-14. We included premolars and molars of a standard phantom head mounted with metal and radiopaque teeth. Radiation was exposed using three radiographic approaches: Standard intraoral, extended length intraoral and extraoral. Since, the unit of analysis was individual root, thus, we had a total of 24 images. The images were stored in VixWin software. The length of the roots was determined using the scale function of the measuring tool inbuilt in the software. Data were analyzed using SPSS version 19.0 and GraphPad software. Pearson correlation coefficient and Bland–Altman test was applied to determine whether the tooth length readings obtained from three different approaches were correlated. P = 0.05 was taken as statistically significant. Results: The correlation between standard intraoral and extended intraoral was 0.97; the correlation between standard intraoral and extraoral method was 0.82 while the correlation between extended intraoral and extraoral was 0.76. The results of Bland–Altman test showed that the average discrepancy between these methods is not large enough to be considered as significant. Conclusions: It appears that the extraoral radiographic method can be used in root length determination in subjects where intraoral radiography is not possible.

APA, Harvard, Vancouver, ISO, and other styles

47

Arumugam, Sankar, Michael G. Jameson, Aitang Xing, and Lois Holloway. "An accuracy assessment of different rigid body image registration methods and robotic couch positional corrections using a novel phantom." Medical Physics 40, no. 3 (February 8, 2013): 031701. http://dx.doi.org/10.1118/1.4789490.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Conti, C. A., E. Votta, C. Corsi, D. De Marchi, G. Tarroni, M. Stevanella, M. Lombardi, O. Parodi, E. G. Caiani, and A. Redaelli. "Left ventricular modelling: a quantitative functional assessment tool based on cardiac magnetic resonance imaging." Interface Focus 1, no. 3 (March 23, 2011): 384–95. http://dx.doi.org/10.1098/rsfs.2010.0029.

Full text

Abstract:

We present the development and testing of a semi-automated tool to support the diagnosis of left ventricle (LV) dysfunctions from cardiac magnetic resonance (CMR). CMR short-axis images of the LVs were obtained in 15 patients and processed to detect endocardial and epicardial contours and compute volume, mass and regional wall motion (WM). Results were compared with those obtained from manual tracing by an expert cardiologist. Nearest neighbour tracking and finite-element theory were merged to calculate local myocardial strains and torsion. The method was tested on a virtual phantom, on a healthy LV and on two ischaemic LVs with different severity of the pathology. Automated analysis of CMR data was feasible in 13/15 patients: computed LV volumes and wall mass correlated well with manually extracted data. The detection of regional WM abnormalities showed good sensitivity (77.8%), specificity (85.1%) and accuracy (82%). On the virtual phantom, computed local strains differed by less than 14 per cent from the results of commercial finite-element solver. Strain calculation on the healthy LV showed uniform and synchronized circumferential strains, with peak shortening of about 20 per cent at end systole, progressively higher systolic wall thickening going from base to apex, and a 10° torsion. In the two pathological LVs, synchronicity and homogeneity were partially lost, anomalies being more evident for the more severely injured LV. Moreover, LV torsion was dramatically reduced. Preliminary testing confirmed the validity of our approach, which allowed for the fast analysis of LV function, even though future improvements are possible.

APA, Harvard, Vancouver, ISO, and other styles

49

Allard, Haven M., Marcela G. Weyhmiller, Ashutosh Lal, and Ellen B. Fung. "In-Accuracy Of Bone Density Measurements By DXA In Patients With Hemoglobinopathies and Iron Overload." Blood 122, no. 21 (November 15, 2013): 966. http://dx.doi.org/10.1182/blood.v122.21.966.966.

Full text

Abstract:

Abstract Introduction When monitoring bone health in patients with hemoglobinapathies, it is unknown if iron in surrounding tissues can lead to inaccuracies in the 2-dimensional assessment by Dual Energy X-ray Absorptiometry (DXA). Objective The aims of this study were: 1) to determine if the accuracy of lumbar spine assessment by DXA is affected by high liver iron concentration in patients with Sickle Cell Disease (SCD) or Thalassemia (Thal), 2) to test the effect of high tissue iron on vertebral Z-scores using phantoms, 3) to explore the ability to account for potential high-iron content effects when performing DXA examinations. Methods This study consisted of a retrospective chart review of data collected by the Children’s Hospital & Research Center Oakland, Bone Density Clinic and Iron Measurement Program. Data from both DXA and Super Conducting Quantum Interference Device (SQUID) examinations collected between 2002 and 2013 from were abstracted. Only those patients with a diagnosis of SCD or Thal, who had a DXA and SQUID measurement within the same year were divided into an iron overload group (liver iron concentration (LIC) >3,000 µg Fe/g wet) and low iron (LIC <500 µg Fe/g wet) group. These patients were compared with healthy controls of which only 13 had both DXA and SQUID tests, 34 had DXA only. The 34 healthy controls without a SQUID test were included because it was assumed, based on their health screen that their liver-iron content would not interfere with DXA. In order to explore aim 1, a lumbar spine scan, by DXA, of each subject was re-analyzed to compare the derived areal bone mineral density (aBMD) Z-scores of lumbar vertebrae that are covered by the liver (presumed L1 or L1/L2) with the Z-scores of the lumbar vertebrae not covered by the liver (L3/L4). To explore aim 2, phantoms were designed to mimic the geometry of iron loaded tissues in order to explore the contribution of iron in specific tissues on the accuracy of DXA assessments. Phantoms were constructed using KNOX® brand gelatin and iron(II) sulfate heptahydrate and had concentrations ranging from 3,000 to 7,000 ug Fe/g gelatin. The iron-loaded phantoms were positioned obtusely overlying L1/L2 of the DXA daily quality control phantom to mimic the position of the liver. All data were analyzed by STATA ver.9.2 and were considered significant with a p<0.05. Results Data from 102 total visits abstracted from 88 subjects [19 SCD (13 F), 24 Thal (12 F), age: 30.1 ± 11.9 years, mean ± SD], and 45 healthy controls (24 F, age: 25.4 ± 11.0 yrs) were analyzed. The SCD and Thal group had an average LIC by SQUID of 4651 ± 2079 µg Fe/g wet tissue and serum ferritin of 5408±2706 ng/mL; while the healthy controls, with both a DXA and a SQUID (n=17), had an average LIC of 251±144. Average aBMD Z-score of the lumbar spine L1-L4 in the Thal group was -2.0 ± 1.1 , the SCD was -2.0 ± 1.6 and the healthy controls: -0.3 ± 0.9. However, when individual vertebrae are analyzed separately, a significant difference was observed between the lumbar spine L1 BMD Z-scores compared to the combined means of L3/L4 Z-scores in the iron loaded population (Table 1). The discrepancy was even greater in subjects with LIC >5000 ug/g wet tissue. These findings were reproduced using heavily iron loaded phantoms. Conclusions Initial results for this study show that there is a relationship between liver iron content and lumbar spine aBMD Z-scores when evaluated by DXA. The BMD Z-score for L1 appears to be more significantly affected by the liver iron content then L2, which was unanticipated. When evaluating patients with liver iron content >3,000 ug/g wet tissue, it is important to consider the effects of iron contribution from the liver on the DXA spine scans and delete L1 and/or L2 from the total Z-score prior to making an interpretation. Failing to do so may under diagnose low bone mass in this at risk patient population. Disclosures: No relevant conflicts of interest to declare.

APA, Harvard, Vancouver, ISO, and other styles

50

Song, Jae-Kwan, Duk-Hyun Kang, Mark D. Handschumacher, and Robert A. Levine. "Assessment of the Accuracy of Digitally Recorded Velocity Information of Color Doppler Flow Mapping:in vitro Validation Using a Flow Phantom." Korean Circulation Journal 29, no. 4 (1999): 429. http://dx.doi.org/10.4070/kcj.1999.29.4.429.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Accuracy assessment phantom'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles