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https://www.readbyqxmd.com/read/28940609/technical-note-scanning-of-parallel-plate-ionization-chamber-and-diamond-detector-for-measurements-of-water-dose-profiles-in-the-vicinity-of-a-narrow-x-ray-microbeam
#1
Nobuteru Nariyama
PURPOSE: Scanning of dosimeters facilitates dose distribution measurements with fine spatial resolutions. This paper presents a method of conversion of the scanning results to water-dose profiles and provides an experimental verification. METHODS: An Advanced Markus chamber and a diamond detector were scanned at a resolution of 6 μm near the beam edges during irradiation with a 25-μm-wide white narrow x-ray beam from a synchrotron radiation source. For comparison, GafChromic films HD-810 and HD-V2 were also irradiated...
September 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28940607/fast-segmentation-of-kidney-components-using-random-forests-and-ferns
#2
Chao Jin, Fei Shi, Dehui Xiang, Lichun Zhang, Xinjian Chen
PURPOSE: This paper studies the feasibility of developinga fast and accurate automatic kidney component segmentation method. The proposed method segments the kidney into four components: renal cortex, renal column, renal medulla and renal pelvis. METHOD: In this paper, we have proposed a highly efficient approach which strategically combines random forests and random ferns methods to segment the kidney into four components: renal cortex, renal column, renal medulla and renal pelvis...
September 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28940528/assessment-of-a-photon-counting-detector-for-a-dual-energy-c-arm-angiographic-system
#3
Moiz Ahmad, Rebecca Fahrig, Leland Pung, Martin Spahn, Niko S Köster, Silke Reitz, Teri Moore, Jang-Hwan Choi, Waldo Hinshaw, Yan Xia, Kerstin Müller
PURPOSE: This article presents the implementation and assessment of photon-counting dual-energy x-ray detector technology for angiographic C-arm systems in interventional radiology. METHODS: A photon-counting detector was successfully integrated into a clinical C-arm CT system. Detector performance was assessed using image uniformity metrics in both 2D projections and 3D cone-beam computed tomography (CBCT) images. Uniform exposure fields were acquired to analyze projection images and scans of a homogeneous cylinder phantom were taken to analyze 3D reconstructions...
September 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28940520/direction-modulated-brachytherapy-dmbt-for-treatment-of-cervical-cancer-a-planning-study-with-192ir-60co-and-169yb-hdr-sources
#4
Habib Safigholi, Dae Yup Han, Shahram Mashouf, Abraam Soliman, Ali S Meigooni, Amir Owrangi, William Y Song
PURPOSE: To evaluate plan quality of a novel MRI-compatible direction modulated brachytherapy (DMBT) tandem applicator using 192Ir, 60Co, and 169Yb HDR brachytherapy sources, for various cervical cancer high-risk clinical target volumes (CTVHR ). MATERIALS AND METHODS: The novel DMBT tandem applicator has six peripheral grooves of 1.3-mm diameter along a 5.4-mm thick nonmagnetic tungsten alloy rod. Monte Carlo (MC) simulations were used to benchmark the dosimetric parameters of the 192Ir, 60Co, and 169Yb HDR sources in a water phantom against the literature data...
September 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28940483/improved-quantitative-90-y-bremsstrahlung-spect-ct-reconstruction-with-monte-carlo-scatter-modeling
#5
Yuni K Dewaraja, Se Young Chun, Ravi N Srinivasa, Ravi K Kaza, Kyle C Cuneo, Bill S Majdalany, Paula M Novelli, Michael Ljungberg, Jeffrey A Fessler
PURPOSE: In (90) Y microsphere radioembolization (RE), accurate post-therapy imaging-based dosimetry is important for establishing absorbed dose versus outcome relationships for developing future treatment planning strategies. Additionally, accurately assessing microsphere distributions is important because of concerns for unexpected activity deposition outside the liver. Quantitative (90) Y imaging by either SPECT or PET is challenging. In (90) Y SPECT model based methods are necessary for scatter correction because energy window-based methods are not feasible with the continuous bremsstrahlung energy spectrum...
September 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28940372/esophagus-segmentation-in-ct-via-3d-fully-convolutional-neural-network-and-random-walk
#6
Tobias Fechter, Sonja Adebahr, Dimos Baltas, Ismail Ben Ayed, Christian Desrosiers, Jose Dolz
PURPOSE: Precise delineation of organs at risk is a crucial task in radiotherapy treatment planning for delivering high doses to the tumour while sparing healthy tissues. In recent years, automated segmentation methods have shown an increasingly high performance for the delineation of various anatomical structures. However, this task remains challenging for organs like the esophagus, which have a versatile shape and poor contrast to neighboring tissues. For human experts, segmenting the esophagus from CT images is a time-consuming and error-prone process...
September 21, 2017: Medical Physics
https://www.readbyqxmd.com/read/28940306/calibration-and-error-analysis-of-metal-oxide-semiconductor-field-effect-transistor-dosimeters-for-computed-tomography-radiation-dosimetry
#7
Sigal Trattner, Peter Prinsen, Jens Wiegert, Elazar-Lars Gerland, Efrat Shefer, Tom Morton, Carla M Thompson, Yoad Yagil, Bin Cheng, Sachin Jambawalikar, Rani Al-Senan, Maxwell Amurao, Sandra S Halliburton, Andrew J Einstein
PURPOSE: Metal-oxide-semiconductor field-effect transistors (MOSFETs) serve as a helpful tool for organ radiation dosimetry, and their use has grown in computed tomography (CT). While different approaches have been used for MOSFET calibration, those using the commonly-available 100 mm pencil ionization chamber have not incorporated measurements performed throughout its length, and moreover no previous work has rigorously evaluated the multiple sources of error involved in MOSFET calibration...
September 21, 2017: Medical Physics
https://www.readbyqxmd.com/read/28921564/machine-specific-quality-assurance-procedure-for-stereotactic-treatments-with-dynamic-couch-rotations
#8
Byron Wilson, Ermias Gete
OBJECTIVE: We present a method in which the treatment couch's accuracy is measured using the electronic portal imaging device (EPID) and a phantom of our own construction. Using this phantom, we were able to quantify the treatment couch walkout, and the rotation angle accuracy for both static and dynamic couch treatments. These measurements were used to provide an accurate measure of the treatment couch isocentre as well as to verify the couch rotation angle recorded in the trajectory log...
September 18, 2017: Medical Physics
https://www.readbyqxmd.com/read/28921541/automatic-labeling-of-mr-brain-images-through-extensible-learning-and-atlas-forests
#9
Lijun Xu, Hong Liu, Enmin Song, Meng Yan, Renchao Jin, Chih-Cheng Hung
PURPOSE: Multi-atlas-based method is extensively used in MR brain images segmentation because of its simplicity and robustness. This method provides excellent accuracy while time-consuming and limited in terms of obtaining information about new atlases. In this study, an automatic labeling of MR brain images through extensible learning and atlas forest is presented to address these limitations. METHODS: We propose an extensible learning model which allows the multi-atlas-based framework capable of managing the datasets with numerous atlases or dynamic atlas datasets and simultaneously ensure the accuracy of automatic labeling...
September 18, 2017: Medical Physics
https://www.readbyqxmd.com/read/28921538/a-fast-inverse-treatment-planning-strategy-facilitating-optimized-catheter-selection-in-image-guided-high-dose-rate-interstitial-gynecologic-brachytherapy
#10
Christian V Guthier, Antonio L Damato, Juergen W Hesser, Akila N Viswanathan, Robert A Cormack
PURPOSE: Interstitial high-dose-rate (HDR) brachytherapy is an important therapeutic strategy for the treatment of locally advanced gynecologic (GYN) cancers. The outcome of this therapy is determined by the quality of dose distribution achieved. This paper focuses on a novel yet simple heuristic for catheter selection for GYN HDR brachytherapy and their comparison against state of the art optimization strategies. The proposed technique is intended to act as a decision-supporting tool to select a favorable needle configuration...
September 18, 2017: Medical Physics
https://www.readbyqxmd.com/read/28921536/technical-note-a-simulation-study-on-the-feasibility-of-radiotherapy-dose-enhancement-with-calcium-tungstate-and-hafnium-oxide-nano-and-microparticles
#11
Nicholas J Sherck, You-Yeon Won
PURPOSE: To assess the radiotherapy dose enhancement (RDE) potential of calcium tungstate (CaWO4 ) and hafnium oxide (HfO2 ) nano- and microparticles (NPs). A Monte Carlo simulation study was conducted to gauge their respective RDE potentials relative to that of the broadly studied gold (Au) NP. The study was warranted due to the promising clinical and preclinical studies involving both CaWO4 and HfO2 NPs as RDE agents in the treatment of various types of cancers. The study provides a baseline RDE to which future experimental RDE trends can be compared to...
September 18, 2017: Medical Physics
https://www.readbyqxmd.com/read/28921613/voxel-based-multi-model-fitting-method-for-modelling-time-activity-curves-in-spect-images
#12
David Sarrut, Adrien Halty, Jean-Noel Badel, Ludovic Ferrer, Manuel Bardiès
PURPOSE: Estimating the biodistribution and the pharmacokinetics from timesequence SPECT images on a per-voxel basis is useful for studying activity nonuniformity or computing absorbed dose distributions by convolution of voxel kernels or Monte-Carlo radiation transport. Current approaches are either region-based, thus assuming uniform activity within the region, or voxel-based but using the same fitting model for all voxels. METHODS: We propose a voxel-based multi-model fitting method (VoMM) that estimates a fitting function for each voxel by automatically selecting the most appropriate model among a predetermined set with Akaike criteria...
September 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28921588/integrating-prior-information-into-microwave-tomography-part-2-impact-of-errors-in-prior-information-on-microwave-tomography-image-quality
#13
Douglas Kurrant, Anastasia Baran, Joe LoVetri, Elise Fear
PURPOSE: The authors have developed a method to combine a patient-specific map of tissue structure and average dielectric properties with microwave tomography. The patient-specific map is acquired with radar-based techniques and serves as prior information for microwave tomography. The impact that the degree of structural detail included in this prior information has on image quality was reported in a previous investigation. The aim of the present study is to extend this previous work by identifying and quantifying the impact that errors in the prior information have on image quality, including the reconstruction of internal structures and lesions embedded in fibroglandular tissue...
September 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28921580/integrating-prior-information-into-microwave-tomography-part-1-impact-of-detail-on-image-quality
#14
Douglas Kurrant, Anastasia Baran, Joe LoVetri, Elise Fear
PURPOSE: The authors investigate the impact that incremental increases in the level of detail of patient-specific prior information have on image quality and the convergence behavior of an inversion algorithm in the context of near-field microwave breast imaging. A methodology is presented that uses image quality measures to characterize the ability of the algorithm to reconstruct both internal structures and lesions embedded in fibroglandular tissue. The approach permits key aspects that impact the quality of reconstruction of these structures to be identified and quantified...
September 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28921931/technical-note-a-simple-algorithm-to-convert-epid-grey-values-into-absorbed-dose-to-water-without-prior-knowledge
#15
Christine Boutry, Aurélie Sors, Jimmy Fontaine, Nolwenn Delaby, Gregory Delpon
PURPOSE: Full integration of EPID-based dosimetry in a global quality control workflow is still complicated. All the actual solutions are based on a relation between image grey-level signal and total linac delivered dose. In this study, we propose a simple algorithm relying pixel grey-level of EPID image with average linac delivered dose per acquisition frame. METHODS: Calibration models are constructed for Varian and Elekta linacs including scattering conditions and EPID-arm backscatter specific corrections...
September 16, 2017: Medical Physics
https://www.readbyqxmd.com/read/28913919/technical-note-on-the-use-of-cylindrical-ionization-chambers-for-electron-beam-reference-dosimetry
#16
Bryan R Muir, Malcolm R McEwen
PURPOSE: To investigate the use of cylindrical chambers for electron beam dosimetry independent of energy by studying the variability of relative ion chamber perturbation corrections, one of the main concerns for electron beam dosimetry with cylindrical chambers. METHODS: Measurements are made with sets of cylindrical and plane-parallel reference-class chambers as a function of depth in water in 8 MeV and 18 MeV electron beams. The ratio of chamber readings for similar chambers is normalized in a high-energy electron beam and can be thought of as relative perturbation corrections...
September 14, 2017: Medical Physics
https://www.readbyqxmd.com/read/28905399/microdosimetric-measurements-of-a-clinical-proton-beam-with-micrometer-sized-solid-state-detector
#17
Sarah E Anderson, Keith M Furutani, Linh T Tran, Lachlan Chartier, Marco Petasecca, Michael Lerch, Dale A Prokopovich, Mark Reinhard, Vladimir L Perevertaylo, Anatoly B Rosenfeld, Michael G Herman, Chris Beltran
PURPOSE: Microdosimetry is a vital tool for assessing the microscopic patterns of energy deposition by radiation, which ultimately govern biological effect. Solid-state, silicon-on-insulator microdosimeters offer an approach for making microdosimetric measurements with high spatial resolution (on the order of tens of micrometers). These high-resolution, solid-state microdosimeters may therefore play a useful role in characterizing proton radiotherapy fields, particularly for making highly-resolved measurements within the Bragg peak region...
September 14, 2017: Medical Physics
https://www.readbyqxmd.com/read/28905394/neutron-damage-induced-in-cardiovascular-implantable-electronic-devices-from-a-clinical-18-mv-photon-beam-a-monte-carlo-study
#18
Ahad Ollah Ezzati, Matthew T Studenski
PURPOSE: To quantify the relative neutron damage induced in CIEDs from clinical 18 MV photon beams for varying field sizes, depths and off axis distances. METHODS AND MATERIALS: Damage was assessed using silicon damage response functions and ICRP neutron dose conversion factors in MCNPX. Particular attention was devoted to the modelling of the Varian 2100C/D linear accelerator to ensure accurate contamination neutron spectra. Neutron dose, fluence and relative damage to CIEDs was calculated...
September 14, 2017: Medical Physics
https://www.readbyqxmd.com/read/28905393/pet-motion-correction-in-context-of-integrated-pet-mr-current-techniques-limitations-and-future-projections
#19
REVIEW
Ashley Gillman, Stephen Rose, Jye Smith, Paul Thomas, Nicholas Dowson
Patient motion is an important consideration in modern PET image reconstruction. Advances in PET technology mean motion has an increasingly important influence on resulting image quality. Motion-induced artefacts can have adverse effect on clinical outcomes, including missed diagnoses and oversized radiotherapy treatment volumes. This review aims to summarise the wide variety of motion correction techniques available in PET and combined PET/CT and PET/MR, with a focus on the latter. A general framework for the motion correction of PET images is presented, consisting of acquisition, modelling and correction stages...
September 14, 2017: Medical Physics
https://www.readbyqxmd.com/read/28905390/validation-of-the-gatortail-method-for-accurate-sizing-of-pulmonary-vessels-from-3d-medical-images
#20
Walter G O'Dell, Anne K Gormaley, David A Prida
PURPOSE: Detailed characterization of changes in vessel size is crucial for the diagnosis and management of a variety of vascular diseases. Because clinical measurement of vessel size is typically dependent on the radiologist's subjective interpretation of the vessel borders, it is often prone to high inter- and intra-user variability. Automatic methods of vessel sizing have been developed for two-dimensional images but a fully three-dimensional (3D) method suitable for vessel sizing from volumetric X-ray computed tomography (CT) or magnetic resonance imaging has heretofore not been demonstrated and validated robustly...
September 14, 2017: Medical Physics
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