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Medical Physics

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https://www.readbyqxmd.com/read/28737014/clinical-implementation-of-an-exit-detector-based-dose-reconstruction-tool-for-helical-tomotherapy-delivery-quality-assurance
#1
Shrikant Deshpande, Aitang Xing, Peter Metcalfe, Lois Holloway, Philip Vial, Mark Geurts
PURPOSE: To validate the accuracy of an exit detector based dose reconstruction tool for Helical Tomotherapy (HT) delivery quality assurance (DQA). METHODS AND MATERIAL: Exit detector based DQA tool was developed for patient specific HT treatment verification. The tool performs a dose reconstruction on the planning image using the sinogram measured by the HT exit detector with no objects in the beam (i.e. static couch), and compares the reconstructed dose to the planned dose...
July 24, 2017: Medical Physics
https://www.readbyqxmd.com/read/28736930/technical-note-mobile-accelerator-guidance-using-an-optical-tracker-during-docking-in-ioert-procedures
#2
Eugenio Marinetto, Juan González Victores, Mónica García-Sevilla, Mercedes Muñoz, Felipe Ángel Calvo, Carlos Balaguer, Manuel Desco, Javier Pascau
PURPOSE: Intraoperative electron radiation therapy (IOERT) involves the delivery of a high radiation dose during tumor resection in a shorter time than other radiation techniques, thus improving local control of tumors. However, a linear accelerator device is needed to produce the beam safely. Mobile linear accelerators have been designed as dedicated units that can be moved into the operating room and deliver radiation in situ. Correct and safe dose delivery is a key concern when using mobile accelerators...
July 24, 2017: Medical Physics
https://www.readbyqxmd.com/read/28736864/brain-tumor-segmentation-using-holistically-nested-neural-networks-in-mri-images
#3
Ying Zhuge, Andra V Krauze, Holly Ning, Jason Y Cheng, Barbara C Arora, Kevin Camphausen, Robert W Miller
PURPOSE: Gliomas are rapidly progressive, neurologically devastating, largely fatal brain tumors. Magnetic Resonance Imaging (MRI) is a widely used technique employed in the diagnosis and management of gliomas in clinical practice. MRI is also the standard imaging modality used to delineate the brain tumor target as part of treatment planning for the administration of radiation therapy. Despite more than 20 years of research and development, computational brain tumor segmentation in MRI images remains a challenging task...
July 24, 2017: Medical Physics
https://www.readbyqxmd.com/read/28736826/impact-of-respiratory-motion-and-acquisition-settings-on-spect-liver-dosimetry-for-radioembolization
#4
Remco Bastiaannet, Max A Viergever, Hugo W A M de Jong
PURPOSE: Respiratory motion may impose significant inaccuracies on emission activity estimation in quantitative SPECT. This effect may be a major issue in dosimetry as used in management of liver radioembolization. The purpose of this study was to investigate the impact of respiratory motion on radioembolization liver dosimetry for different SPECT acquisition settings. METHODS: In a series of SPECT/CT Monte Carlo simulations using several digital XCAT phantoms, the following parameters were varied: breathing/non-breathing, liver tumor size (0...
July 24, 2017: Medical Physics
https://www.readbyqxmd.com/read/28736809/dose-evaluation-of-grid-therapy-using-a-6-mv-flattening-filter-free-fff-photon-beam-a-monte-carlo-study
#5
Immaculada Martínez-Rovira, Josep Puxeu, Yolanda Prezado
PURPOSE: Spatially fractionated radiotherapy is a strategy to overcome the main limitation of radiotherapy, i.e., the restrained normal tissue tolerances. A well-known example is Grid Therapy, which is currently performed at some hospitals using megavoltage photon beams delivered by Linacs. Grid Therapy has been successfully used in the management of bulky abdominal tumors with low toxicity. The aim of this work is to evaluate whether an improvement in therapeutic index in Grid Therapy can be obtained by implementing it in a flattening filter-free (FFF) Linac...
July 24, 2017: Medical Physics
https://www.readbyqxmd.com/read/28731267/heuristic-knowledge-based-planning-for-single-isocenter-stereotactic-radiosurgery-to-multiple-brain-metastases
#6
Benjamin P Ziemer, Parag Sanghvi, Jona Hattangadi-Gluth, Kevin L Moore
PURPOSE: Single-isocenter, volumetric modulated arc therapy (VMAT) stereotactic radiosurgery (SRS) for multiple brain metastases (multi-mets) can deliver highly conformal dose distributions and reduce overall patient treatment time compared to other techniques. However, treatment planning for multi-met cases is highly complex due to variability in numbers and sizes of brain metastases, as well as their relative proximity to organs-at-risk (OARs). The purpose of this study was to automate the VMAT planning of multi-met cases through a knowledge-based planning (KBP) approach that adapts single target SRS dose predictions to multiple target predictions...
July 21, 2017: Medical Physics
https://www.readbyqxmd.com/read/28730606/technical-note-empirical-altitude-correction-factors-for-well-chamber-measurements-of-permanent-prostate-and-breast-seed-implant-sources
#7
Elizabeth Watt, David P Spencer, Tyler Meyer
PURPOSE: Previous studies in the literature have measured an altitude effect for low-energy brachytherapy seeds; a correction factor applied in addition to PTP to account for the breakdown of Bragg-Gray cavity theory at low energies in well-type ionization chambers. In clinical practice, many centres use altitude correction factors that are not seed-model-specific. The purpose of this work is to present altitude correction factors for several seed models without documented factors in the literature...
July 21, 2017: Medical Physics
https://www.readbyqxmd.com/read/28722180/a-generic-tg-186-shielded-applicator-for-commissioning-model-based-dose-calculation-algorithms-for-high-dose-rate-192-ir-brachytherapy
#8
Yunzhi Ma, Javier Vijande, Facundo Ballester, Åsa Carlsson Tedgren, Domingo Granero, Annette Haworth, Firas Mourtada, Gabriel Paiva Fonseca, Kyveli Zourari, Panagiotis Papagiannis, Mark J Rivard, Frank André Siebert, Ron S Sloboda, Ryan Smith, Marc J P Chamberland, Rowan M Thomson, Frank Verhaegen, Luc Beaulieu
PURPOSE: A joint working group was created by the American Association of Physicists in Medicine (AAPM), the European Society for Radiotherapy and Oncology (ESTRO), and the Australasian Brachytherapy Group (ABG) with the charge, among others, to develop a set of well-defined test case plans and perform model-based dose calculation algorithms (MBDCA) dose calculations and comparisons. Its main goal is to facilitate a smooth transition from the AAPM Task Group No. 43 (TG-43) dose calculation formalism, widely being used in clinical practice for brachytherapy, to the one proposed by Task Group No...
July 19, 2017: Medical Physics
https://www.readbyqxmd.com/read/28718888/assessing-lung-function-using-contrast-enhanced-dual-energy-computed-tomography-for-potential-applications-in-radiation-therapy
#9
Andréanne Lapointe, Houda Bahig, Danis Blais, Hugo Bouchard, Édith Filion, Jean-François Carrier, Stéphane Bedwani
PURPOSE: There is an increasing interest in the evaluation of lung function from physiological images in radiation therapy treatment planning to reduce the extent of post-radiation toxicities. The purpose of this work is to retrieve reliable functional information from contrast-enhanced dualenergy computed tomography (DECT) for new applications in radiation therapy. The functional information obtained by DECT is also compared with other methods using single energy CT (SECT) and single-photon emission computed tomography (SPECT) with CT...
July 18, 2017: Medical Physics
https://www.readbyqxmd.com/read/28715130/average-glandular-dose-coefficients-for-pendant-geometry-breast-ct-using-realistic-breast-phantoms
#10
Andrew M Hernandez, John M Boone
PURPOSE: To design volume-specific breast phantoms from breast CT (bCT) data sets and estimate the associated normalized mean glandular dose coefficients for breast CT using Monte Carlo methods. METHODS: A large cohort of bCT data sets (N=215) was used to evaluate breast volume into quintiles (plus the top 5%). The average radius profile was then determined for each of the six volume-specific groups and used to both fabricate physical phantoms and generate mathematical phantoms (V1-V6; "V" denotes classification by volume)...
July 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28715090/learning-based-automated-segmentation-of-the-carotid-artery-vessel-wall-in-dual-sequence-mri-using-subdivision-surface-fitting
#11
Shan Gao, Ronald Van't Klooster, Pieter H Kitslaar, Bram F Coolen, Alexandra M van den Berg, Loek P Smits, Rahil Shahzad, Denis P Shamonin, Patrick J H de Koning, Aart J Nederveen, Rob J van der Geest
PURPOSE: The quantification of vessel wall morphology and plaque burden requires vessel segmentation, which is generally performed by manual delineations. The purpose of our work is to develop and evaluate a new 3D model-based approach for carotid artery wall segmentation from dual-sequence MRI. METHODS: The proposed method segments the lumen and outer wall surfaces including the bifurcation region by fitting a subdivision surface constructed hierarchical-tree model to the image data...
July 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28714067/evaluation-of-plastic-scintillator-detector-for-small-field-stereotactic-patient-specific-quality-assurance
#12
Yujiao Qin, Stephen J Gardner, Joshua Kim, Yimei Huang, Ning Wen, Anthony Doemer, Indrin J Chetty
PURPOSE: To evaluate the performance of a commercial plastic scintillator detector (PSD) for small-field stereotactic patient-specific quality assurance (QA) measurements using flattening-filter-free beam. METHODS: A total of ten spherical targets (volume range: [0.03cc-2cc]) were planned with two techniques: (1) Dynamic Conformal Arc (DCA-10 plans), and (2) Volumetric Modulated Arc Therapy (VMAT-10 plans). All plans were generated using Varian Eclipse treatment planning system, and AcurosXB v...
July 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28710871/detection-and-quantification-of-coronary-calcium-from-dual-energy-chest-x-rays-phantom-feasibility-study
#13
Bo Zhou, Di Wen, Katelyn Nye, Robert C Gilkeson, Brendan Eck, David Jordan, David L Wilson
PURPOSE: We have demonstrated the ability to identify coronary calcium, a reliable biomarker of coronary artery disease, using non-gated, 2-shot, dual energy (DE) chest x-ray imaging. Here we will use digital simulations, backed up by measurements, to characterize DE calcium signals and the role of potential confounds such as beam hardening, x-ray scatter, cardiac motion, and pulmonary artery pulsation. For the DE calcium signal, we will consider quantification, as compared to CT calcium score, and visualization...
July 15, 2017: Medical Physics
https://www.readbyqxmd.com/read/28710866/response-of-synthetic-diamond-detectors-in-proton-carbon-and-oxygen-ion-beams
#14
Séverine Rossomme, Marco Marinelli, Gianluca Verona-Rinati, Francesco Romano, G A Pablo Cirrone, Andrzej Kacperek, Stefaan Vynckier, Hugo Palmans
PURPOSE: In this work, the LET-dependence of the response of synthetic diamond detectors is investigated in different particle beams. METHOD: Measurements were performed in three non-modulated particle beams (proton, carbon and oxygen). The response of five synthetic diamond detectors was compared to the response of a Markus or an Advanced Markus ionization chamber. The synthetic diamond detectors were used with their axis parallel to the beam axis and without any bias voltage...
July 15, 2017: Medical Physics
https://www.readbyqxmd.com/read/28710805/a-method-to-measure-the-absorbed-dose-of-the-thyroid-during-i-131-therapy-using-a-collar-detector-system-and-a-spect-acquisition
#15
Koen van Gils, Peter Brinks, Jules Lavalaye, Hein J Verberne, Jan B A Habraken
PURPOSE: Due to variations in biological half-life, accurate thyroid dosimetry for I-131 therapy is not trivial in clinical practice. In recent publications, systems are described to measure the uptake of I-131 in the thyroid repeatedly over time. In this work we present a method to calculate patient specific pharmacokinetics and absorbed dose using such a collar detector system (CoTI) in combination with a SPECT acquisition and a two-compartment model fit. METHODS: For three patients receiving I-131 therapy for benign thyroid conditions, the complete uptake profile is measured over a period of 15 to 25 days after administration...
July 15, 2017: Medical Physics
https://www.readbyqxmd.com/read/28703922/sensitivity-evaluation-and-selective-plane-imaging-geometry-for-x-ray-induced-luminescence-imaging
#16
Bryan P Quigley, Corey D Smith, Shih-Hsun Cheng, Jeffrey S Souris, Charles A Pelizzari, Chin-Tu Chen, Leu-Wei Lo, Chester S Reft, Rodney D Wiersma, Patrick J La Riviere
PURPOSE: X-ray induced luminescence (XIL) is a hybrid X-ray/optical imaging modality that employs nanophosphors that luminescence in response to X-ray irradiation. X-ray-activated phosphorescent nanoparticles have potential applications in radiation therapy as theranostics, nanodosimeters, or radiosensitizers. Extracting clinically relevant information from the luminescent signal requires the development of a robust imaging model that can determine nanophosphor distributions at depth in an optically scattering environment from surface radiance measurements...
July 13, 2017: Medical Physics
https://www.readbyqxmd.com/read/28696514/modulation-of-lateral-positions-of-bragg-peaks-via-magnetic-fields-inside-cancer-patients-towards-magnetic-field-modulated-proton-therapy
#17
Wencheng Shao, Xiaobin Tang, Yanling Bai, Changran Geng, Diyun Shu, Chunhui Gong, Da Chen
PURPOSE: This work investigated whether the Bragg peak (BP) positions of proton beams can be modulated to produce uniform doses and cover a tumor under the magnetic fields inside cancer patients, and whether magnetic field modulated proton therapy (MMPT) is effective in vital organ protection. METHODS: The authors initially constructed an ideal water phantom comprising a central tumor surrounded by cuboid organ regions using GEANT4. Second, we designed the proton beams passing through the gap between two adjacent organ regions during beam configuration...
July 11, 2017: Medical Physics
https://www.readbyqxmd.com/read/28696500/development-of-a-silicon-diode-detector-for-skin-dosimetry-in-radiotherapy
#18
Nikolina Vicoroski, Anthony Espinoza, Mitchell Duncan, Bradley Michael Oborn, Martin Carolan, Peter Metcalfe, David Menichelli, Vladimir L Perevertaylo, Michael L F Lerch, Anatoly B Rosenfeld, Marco Petasecca
PURPOSE: The aim of in-vivo skin dosimetry is to measure the absorbed dose to the skin during radiotherapy, when treatment planning calculations cannot be relied on. It is of particularly importance in hypo-fractionated stereotactic modalities, where excessive dose can lead to severe skin toxicity. Currently commercial diodes for such applications are with water equivalent depths ranging from 0.5 to 0.8 mm. In this study, we investigate a new detector for skin dosimetry based on a silicon epitaxial diode, referred to as the skin diode...
July 11, 2017: Medical Physics
https://www.readbyqxmd.com/read/28692137/portable-perfusion-phantom-for-quantitative-dce-mri-of-the-abdomen
#19
Harrison Kim, Mina Mousa, Patrick Schexnailder, Robert Hergenrother, Mark Bolding, Bernard Ntsikoussalabongui, Vinoy Thomas, Desiree E Morgan
PURPOSE: To develop a portable perfusion phantom and validate its utility in quantitative dynamic contrast-enhanced magnetic resonance imaging of the abdomen. METHODS: A portable perfusion phantom yielding a reproducible contrast enhancement curve (CEC) was developed. A phantom package including perfusion and static phantoms were imaged simultaneously with each of three healthy human volunteers in two different 3T MR scanners. Look-up tables correlating reference (known) contrast concentrations with measured ones were created using either the static or perfusion phantom...
July 10, 2017: Medical Physics
https://www.readbyqxmd.com/read/28692129/distortion-free-diffusion-mri-using-an-mri-guided-tri-cobalt-60-radiotherapy-system-sequence-verification-and-preliminary-clinical-experience
#20
Yu Gao, Fei Han, Ziwu Zhou, Minsong Cao, Tania Kaprealian, Mitchell Kamrava, Chenyang Wang, John Neylon, Daniel A Low, Yingli Yang, Peng Hu
PURPOSE: Monitoring tumor response during the course of treatment and adaptively modifying treatment plan based on tumor biological feedback may represent a new paradigm for radiotherapy. Diffusion MRI has shown great promises in assessing and predicting tumor response to radiotherapy. However, the conventional diffusion-weighted single-shot echo-planar-imaging (DW-ssEPI) technique suffers from limited resolution, severe distortion and possibly inaccurate ADC at low field strength. The purpose of this work is to develop a reliable, accurate and distortion-free diffusion MRI technique that is practicable for longitudinal tumor response evaluation and adaptive radiotherapy on a 0...
July 10, 2017: Medical Physics
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