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Medical Physics

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https://www.readbyqxmd.com/read/28339110/a-fast-non-iterative-approach-for-accelerated-high-temporal-resolution-cine-cmr-using-dynamically-interleaved-streak-removal-in-the-power-spectral-encoded-domain-with-low-pass-filtering-dispel-and-modulo-prime-spokes-mops
#1
Keigo Kawaji, Mita B Patel, Charles G Cantrell, Akiko Tanaka, Marco Marino, Satoshi Tamura, Hui Wang, Yi Wang, Timothy J Carroll, Takeyoshi Ota, Amit R Patel
PURPOSE: To introduce a pair of accelerated non-Cartesian acquisition principles that when combined, exploit the periodicity of k-space acquisition, and thereby enable acquisition of high-temporal cine-Cardiac Magnetic Resonance (CMR). METHODS: The mathematical formulation of a non-iterative, undersampled non-Cartesian cine acquisition and reconstruction is presented. First, a low-pass-filtering step that exploits streaking artifact redundancy is provided; (i.e...
March 24, 2017: Medical Physics
https://www.readbyqxmd.com/read/28339109/validation-of-dynamic-treatment-couch-tracking-for-prostate-sbrt
#2
Stefanie Ehrbar, Simon Schmid, Alexander Jöhl, Stephan Klöck, Matthias Guckenberger, Oliver Riesterer, Stephanie Tanadini-Lang
PURPOSE: In stereotactic body radiation therapy (SBRT) of prostatic cancer, a high dose per fraction is applied to the target with steep dose gradients. Intrafractional prostate motion can occur unpredictably during the treatment and lead to target miss. This work investigated the dosimetric benefit of motion compensation with dynamic treatment-couch tracking for prostate SBRT treatments in the presence of prostatic motion. METHODS: Ten SBRT treatment plans for prostate cancer patients with integrated boosts to their index lesion were prepared...
March 24, 2017: Medical Physics
https://www.readbyqxmd.com/read/28339108/very-high-energy-electron-vhee-beams-in-radiation-therapy-treatment-plan-comparison-between-vhee-vmat-and-ppbs
#3
Emil Schüler, Kjell Eriksson, Elin Hynning, Steven L Hancock, Susan M Hiniker, Magdalena Bazalova-Carter, Tony Wong, Quynh-Thu Le, Billy W Loo, Peter G Maxim
PURPOSE: The aim of this study was to evaluate the performance of very high energy electron beams (VHEE) beams in comparison to clinically derived treatment plans generated with volumetric modulated arc therapy (VMAT) and proton pencil beam scanning (PPBS) technology. We developed a custom optimization script that could be applied automatically across modalities to eliminate operator bias during IMRT optimization. METHODS: Four clinical cases were selected (prostate cancer, lung cancer, pediatric brain tumor, and head and neck cancer (HNC))...
March 24, 2017: Medical Physics
https://www.readbyqxmd.com/read/28339107/studies-of-signal-estimation-bias-in-grating-based-x-ray-multi-contrast-imaging
#4
Xu Ji, Yongshuai Ge, Ran Zhang, Ke Li, Guang-Hong Chen
PURPOSE: In grating-based x-ray multi-contrast imaging, signals of three contrast mechanisms-absorption contrast, differential phase contrast (DPC), and dark-field contrast-can be estimated from the same set of acquired data. The estimated sig-nals, N0 (related to absorption), N1 (related to dark-field), and ϕ (related to DPC) may be intrinsically biased. However, it is yet unclear how large these biases are and how the data acquisition parameters affect the biases in the extracted signals...
March 24, 2017: Medical Physics
https://www.readbyqxmd.com/read/28339103/iterative-dataset-optimization-in-automated-planning-implementation-for-breast-and-rectal-cancer-radiotherapy
#5
Jiawei Fan, Jiazhou Wang, Zhen Zhang, Weigang Hu
PURPOSE: To develop a new automated treatment planning solution for breast and rectal cancer radiotherapy. METHODS: The automated treatment planning solution developed in this study includes selection of the iterative optimized training dataset, dose volume histogram (DVH) prediction for the organs at risk (OARs), and automatic generation of clinically acceptable treatment plans. The iterative optimized training dataset is selected by an iterative optimization from 40 treatment plans for left-breast and rectal cancer patients who received radiation therapy...
March 24, 2017: Medical Physics
https://www.readbyqxmd.com/read/28332211/a-multi-channel-block-matching-denoising-algorithm-for-spectral-photon-counting-ct-images
#6
Adam P Harrison, Ziyue Xu, David A Bluemke, Amir Pourmorteza, Daniel J Mollura
PURPOSE: We present a denoising algorithm designed for a whole-body prototype photon-counting computed tomography (PCCT) scanner with up to 4 energy thresholds and associated energy-binned images. METHODS: Spectral PCCT images can exhibit low signal to noise ratios (SNRs) due to the limited photon counts in each simultaneously-acquired energy bin. To help address this, our denoising method exploits the correlation and exact alignment between energy bins, adapting the highly-effective block-matching 3D (BM3D) denoising algorithm for PCCT...
March 23, 2017: Medical Physics
https://www.readbyqxmd.com/read/28332199/investigating-the-feasibility-of-classifying-breast-microcalcifications-using-photon-counting-spectral-mammography-a-simulation-study
#7
Bahaa Ghammraoui, Stephen J Glick
PURPOSE: A dual-energy material decomposition method using photon-counting spectral mammography was investigated as a non-invasive diagnostic approach to differentiate between Type I calcifications, consisting of calcium oxalate dihydrate or weddellite compounds that are more often associated with benign lesions, and Type II calcifications containing hydroxyapatite that are predominantly associated with malignant tumors. METHODS: The study was carried out by numerical simulation to assess the feasibility of the proposed approach...
March 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28317129/towards-robust-adaptive-radiation-therapy-strategies
#8
Michelle Böck, Anders Forsgren, Kjell Eriksson, Björn Hårdemark
PURPOSE: To set up a framework combining robust treatment planning with adaptive reoptimization in order to maintain high treatment quality, to respond to interfractional geometric variations and to identify those patients who will benefit the most from an adaptive fractionation schedule. METHODS: The authors propose robust adaptive strategies based on stochastic minimax optimization for a series of simulated treatments on a one-dimensional patient phantom. The plan applied during the first fractions should be able to handle anticipated systematic and random errors...
March 20, 2017: Medical Physics
https://www.readbyqxmd.com/read/28317128/comparison-of-dce-mri-kinetic-parameters-and-fmiso-pet-uptake-parameters-in-head-and-neck-cancer-patients
#9
Urban Simoncic, Sara Leibfarth, Stefan Welz, Nina Schwenzer, Holger Schmidt, Gerald Reischl, Christina Pfannenberg, Christian la Fougère, Konstantin Nikolaou, Daniel Zips, Daniela Thorwarth
PURPOSE: Tumour hypoxia is a major cause of radiation resistance, often present in various solid tumours. Dynamic [(18) F]-fluoromisonidazole (FMISO) PET imaging is able to reliably assess tumour hypoxia. Comprehensive characterization of tumour microenvironment through FMISO-PET and dynamic contrast enhanced (DCE) MR multimodality imaging might be a valuable alternative to the dynamic FMISO-PET acquisition. The aim of this work was to explore the correlation between the FMISO-PET and DCE-MRI kinetic parameters...
March 20, 2017: Medical Physics
https://www.readbyqxmd.com/read/28317125/referenceless-magnetic-resonance-temperature-imaging-using-gaussian-process-modeling
#10
Joshua P Yung, David Fuentes, Christopher J MacLellan, Florian Maier, Yannis Liapis, John D Hazle, R Jason Stafford
PURPOSE: During magnetic resonance (MR)-guided thermal therapies, water proton resonance frequency shift (PRFS) based MR temperature imaging can quantitatively monitor tissue temperature changes. It is widely known that the PRFS technique is easily perturbed by tissue motion, tissue susceptibility changes, magnetic field drift, and modality-dependent applicator induced artifacts. Here a referenceless Gaussian process modeling (GPM) based estimation of the PRFS is investigated as a methodology to mitigate unwanted background field changes...
March 20, 2017: Medical Physics
https://www.readbyqxmd.com/read/28317123/motion-management-strategies-and-technical-issues-associated-with-stereotactic-body-radiotherapy-of-thoracic-and-upper-abdominal-tumors-a-review-from-nrg-oncology
#11
Edward D Brandner, Indrin J Chetty, Tawfik G Giaddui, Ying Xiao, M Saiful Huq
The efficacy of stereotactic body radiotherapy (SBRT) has been well demonstrated. However, it presents unique challenges for accurate planning and delivery especially in the lungs and upper abdomen where respiratory motion can be significantly confounding accurate targeting and avoidance of normal tissues. In this paper we review the current literature on SBRT for lung and upper abdominal tumors with particular emphasis on addressing respiratory motion and its affects. We provide recommendations on strategies to manage motion for different, patient specific situations...
March 20, 2017: Medical Physics
https://www.readbyqxmd.com/read/28317122/an-anthropomorphic-abdominal-phantom-for-deformable-image-registration-accuracy-validation-in-adaptive-radiation-therapy
#12
Yuliang Liao, Linjing Wang, Xiangdong Xu, Haibin Chen, Jiawei Chen, Guoqian Zhang, Huaiyu Lei, Ruihao Wang, Shuxu Zhang, Xuejun Gu, Xin Zhen, Linghong Zhou
PURPOSE: To design and construct a three-dimensional (3D) anthropomorphic abdominal phantom for geometric accuracy and dose summation accuracy evaluations of deformable image registration (DIR) algorithms for adaptive radiation therapy (ART). METHOD: Organ molds, including liver, kidney, spleen, stomach, vertebra and two metastasis tumors, were 3D printed using contours from an ovarian cancer patient. The organ molds were molded with deformable gels made of different mixtures of polyvinyl chloride (PVC) and the softener dioctyl terephthalate...
March 20, 2017: Medical Physics
https://www.readbyqxmd.com/read/28303582/generation-and-analysis-of-clinically-relevant-breast-imaging-x-ray-spectra
#13
Andrew M Hernandez, J Anthony Seibert, Anita Nosratieh, John M Boone
PURPOSE: The purpose of this work was to develop and make available x-ray spectra for some of the most widely used digital mammography (DM), breast tomosynthesis (BT), and breast CT (bCT) systems in North America. METHODS: The Monte Carlo code MCNP6 was used to simulate minimally-filtered (only beryllium) x-ray spectra at 8 tube potentials from 20 to 49 kV for DM/BT, and 9 tube potentials from 35 to 70 kV for bCT. Vendor-specific anode compositions, effective anode angles, focal spot sizes, source-to-detector distances, and beryllium filtration were simulated...
March 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28295434/the-potential-of-dual-energy-ct-to-reduce-proton-beam-range-uncertainties
#14
Esther Bär, Arthur Lalonde, Gary Royle, Hsiao-Ming Lu, Hugo Bouchard
PURPOSE: Dual-energy CT (DECT) promises improvements in estimating stopping power ratios (SPRs) for proton therapy treatment planning. Although several comparable mathematical formalisms have been proposed in literature, the optimal techniques to characterize human tissue SPRs with DECT in a clinical environment are not fully established. The aim of this work is to compare the most robust DECT methods against conventional single-energy CT (SECT) in conditions reproducing a clinical environment, where CT artifacts and noise play a major role on the accuracy of these techniques...
March 15, 2017: Medical Physics
https://www.readbyqxmd.com/read/28295418/technical-note-on-the-accuracy-of-parametric-two-parameter-cross-section-models-in-dual-energy-ct-applications
#15
Dong Han, Mariela A Porras-Chaverri, Joseph A O'Sullivan, David G Politte, Jeffrey F Williamson
PURPOSE: To evaluate and compare the theoretically achievable accuracy of two families of two-parameter photon cross-section models: basis vector model (BVM) and modified parametric fit model (mPFM). METHOD: The modified PFM assumes that photoelectric absorption and scattering cross sections can be accurately represented by power functions in effective atomic number and / or energy plus the Klein-Nishina cross section, along with empirical corrections that enforce exact prediction of elemental cross sections...
March 15, 2017: Medical Physics
https://www.readbyqxmd.com/read/28295405/optimal-reconstruction-and-quantitative-image-features-for-computer-aided-diagnosis-tools-for-breast-ct
#16
Juhun Lee, Robert M Nishikawa, Ingrid Reiser, John M Boone
PURPOSE: The purpose of this study is to determine the optimal representative reconstruction and quantitative image feature set for a computer-aided diagnosis (CADx) scheme for dedicated breast computer tomography (bCT). METHOD: We used 93 bCT scans that contain 102 breast lesions (62 malignant, 40 benign). Using an iterative image reconstruction (IIR) algorithm, we created 37 reconstructions with different image appearances for each case. In addition, we added a clinical reconstruction for comparison purposes...
March 15, 2017: Medical Physics
https://www.readbyqxmd.com/read/28295403/toward-a-3d-transrectal-ultrasound-system-for-verification-of-needle-placement-during-high-dose-rate-interstitial-gynecologic-brachytherapy
#17
Jessica Robin Rodgers, Kathleen Surry, Eric Leung, David D'Souza, Aaron Fenster
PURPOSE: Treatment for gynecologic cancers, such as cervical, recurrent endometrial, and vaginal malignancies, commonly includes external-beam radiation and brachytherapy. In high-dose-rate (HDR) interstitial gynecologic brachytherapy, radiation treatment is delivered via hollow needles that are typically inserted through a template on the perineum with a cylinder placed in the vagina for stability. Despite the need for precise needle placement to minimize complications and provide optimal treatment, there is no standard intra-operative image-guidance for this procedure...
March 15, 2017: Medical Physics
https://www.readbyqxmd.com/read/28295396/the-use-of-gadolinium-based-contrast-agents-should-be-discontinued-until-proven-safe
#18
Stacy Matthews Branch, Michael F Tweedle, Colin G Orton
Gadolinium-based contrast agents (GBCAs) are widely used in MRI to increase the visibility of tissues. Some believe, however, that due to their documented toxicity, clinical use of these agents should be discontinued until proven safe. This is the premise debated in this month's Point/Counterpoint. This article is protected by copyright. All rights reserved.
March 15, 2017: Medical Physics
https://www.readbyqxmd.com/read/28295388/subjects-such-as-strategic-planning-extra-disciplinary-communication-and-management-have-become-crucial-to-medical-physics-clinical-practice-and-should-become-an-integral-part-of-the-medical-physics-curriculum
#19
Carmel J Caruana, J Adam M Cunha, Colin G Orton
In addition to their clinical duties, many medical physicists find themselves in a situation where they have to do managerial work such as strategic planning and communication within a hospital or with outside agencies. Typically, these skills are obtained on-the-job or by taking extra-curricular courses. However, some believe that such strategic planning and communication and management skills are so important that courses on these topics should become an integral part of the medical physics curriculum. This is the claim debated in this month's Point/Counterpoint...
March 15, 2017: Medical Physics
https://www.readbyqxmd.com/read/28295385/technical-note-the-design-and-function-of-a-horizontal-patient-rotation-system-for-the-purposes-of-fixed-beam-cancer-radiotherapy
#20
Ilana Feain, Lloyd Coleman, Hue Wallis, Richard Sokolov, Ricky O'Brien, Paul Keall
PURPOSE: Cancer radiation therapy treatment is performed by delivering a 3D dose distribution to the tumour via the relative rotation between beam and patient. Whilst most modern machines rotate the radiation beam around a still patient, the treatment can also be delivered by rotating the patient relative to a fixed beam. Fixed-beam, patient rotation radiotherapy machines show promise for reducing the size, surface area footprint, and shielding requirements compared with rotating gantry machines...
March 15, 2017: Medical Physics
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