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Medical Physics

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https://www.readbyqxmd.com/read/28107554/inclusion-of-a-variable-rbe-into-proton-and-photon-plan-comparison-for-various-fractionation-schedules-in-prostate-radiation-therapy
#1
Jakob Ödén, Kjell Eriksson, Iuliana Toma-Dasu
PURPOSE: A constant relative biological effectiveness (RBE) of 1.1 is currently used in proton radiation therapy to account for the increased biological effectiveness compared to photon therapy. However, there is increasing evidence that proton RBE vary with the linear energy transfer (LET), the dose per fraction and the type of the tissue. Therefore, this study aims to evaluate the impact of disregarding variations in RBE when comparing proton and photon dose plans for prostate treatments for various fractionation schedules using published RBE models and several α/β assumptions...
January 20, 2017: Medical Physics
https://www.readbyqxmd.com/read/28107548/mri-based-prostate-cancer-detection-with-high-level-representation-and-hierarchical-classification
#2
Yulian Zhu, Li Wang, Mingxia Liu, Chunjun Qian, Ambereen Yousuf, Aytekin Oto, Dinggang Shen
PURPOSE: Extracting the high-level feature representation by using deep neural networks for detection of prostate cancer, and then based on high-level feature representation for constructing hierarchical classification to refine the detection results. METHODS: High-level feature representation is first learned by a deep learning network, where multi-parametric MR images are used as the input data. Then, based on the learned high-level features, a hierarchical classification method is developed, where multiple random forest classifiers are iteratively constructed to refine the detection results of prostate cancer...
January 20, 2017: Medical Physics
https://www.readbyqxmd.com/read/28100004/technical-note-measurement-of-common-carotid-artery-lumen-dynamics-using-black-blood-mr-cine-imaging
#3
Erpeng Dai, Li Dong, Zhe Zhang, Lyu Li, Hui Zhang, Xihai Zhao, Jinnan Wang, Chun Yuan, Hua Guo
PURPOSE: To demonstrate the feasibility of measuring the common carotid artery (CCA) lumen dynamics using a black blood cine (BB-cine) imaging method. METHODS: Motion-sensitized driven-equilibrium (MSDE) prepared spoiled gradient sequence was used for the BB-cine imaging. CCAs of eleven healthy volunteers were studied using this method. Lumen dynamics, including lumen area evolution waveforms and distension values, were measured and evaluated by comparing this method with bright blood cine (BrB-cine) imaging...
January 18, 2017: Medical Physics
https://www.readbyqxmd.com/read/28099995/technical-note-fast-respiratory-motion-estimation-using-sorted-singles-without-unlist-processing-a-feasibility-study
#4
Jaewon Yang, Mehdi Khalighi, Thomas A Hope, Karen Ordovas, Youngho Seo
PURPOSE: The study aims to demonstrate the feasibility of fast respiratory motion estimation using singles data available as a sorted format in list-mode files acquired in an integrated PET/MRI system for a proof-of-concept. METHODS: The derivation of SDRM is enabled by singles recorded and binned by second for each detector crystal in PET list-mode data acquired in a SIGNA PET/MR. The proposed method is to derive a SDRM trace by summing up all singles from all detectors through the PET data acquisition...
January 18, 2017: Medical Physics
https://www.readbyqxmd.com/read/28097674/monte-carlo-simulations-of-ceiling-scatter-in-nuclear-medicine-99m-tc-131-i-and-18-f
#5
Roald S Schnerr, Anouk N de Jong, Guillaume Landry, Cécile R L P N Jeukens, Roel Wierts
PURPOSE: In the design of nuclear medicine treatment and examination rooms, an important consideration is the shielding required for ionizing radiation from the radioactive isotopes used. The shielding in the walls is normally limited to a height lower than the actual ceiling height. The direct radiation, possibly with build-up correction, can be calculated relatively easily. However, little data is available to estimate the dose contribution from ionizing radiation traveling over the wall shielding and scattering off the ceiling...
January 18, 2017: Medical Physics
https://www.readbyqxmd.com/read/28094862/software-platform-for-simulation-of-a-prototype-proton-ct-scanner
#6
Valentina Giacometti, Vladimir A Bashkirov, Pierluigi Piersimoni, Susanna Guatelli, Tia E Plautz, Hartmut F-W Sadrozinski, Robert P Johnson, Andriy Zatserklyaniy, Thomas Tessonnier, Katia Parodi, Anatoly B Rosenfeld, Reinhard W Schulte
PURPOSE: Proton computed tomography (pCT) is a promising imaging technique to substitute or at least complement x-ray CT for more accurate proton therapy treatment planning as it allows calculating directly proton relative stopping power from proton energy loss measurements. A proton CT scanner with a silicon-based particle tracking system and a 5 stage scintillating energy detector has been completed. In parallel a modular software platform was developed to characterize the performance of the proposed pCT...
January 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28094856/percent-depth-doses-and-x-ray-beam-characterizations-of-a-fluoroscopic-system-incorporating-copper-filtration
#7
Kevin A Wunderle, Andrew R Godley, Zhilei Liu Shen, Joseph T Rakowski, Frank F Dong
PURPOSE: In this investigation, we sought to characterize X-ray beam qualities and quantify percent depth dose (PDD) curves for fluoroscopic X-ray beams incorporating added copper (Cu) filtration, such as those commonly used in fluoroscopically guided interventions (FGI). The intended application of this research is for dosimetry in soft tissue from FGI procedures using these data. METHODS: All measurements in this study were acquired on a Siemens (Erlangen, Germany) Artis zeego fluoroscope...
January 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28094855/technical-note-dose-distributions-in-the-vicinity-of-high-density-implants-using-3d-gel-dosimeters
#8
Andre Asena, Shaun Thomas Smith, Tanya Kairn, Scott Bradley Crowe, Kazuyuki Hosokawa, Steven Sylvander, Jamie Vincent Trapp
PURPOSE: In this work, we develop a methodology for using Fricke gel dosimeters for dose distribution measurements surrounding high-density implants which circumvents artefact production by removing the obstruction during imaging. METHODS: Custom 3D printed moulds were used to set cavities in Fricke gel phantoms to allow for the suspension of high density implants in different geometries. This allowed for the metal valve extracted from a temporary tissue expander to be suspended during irradiation, and removed during optical-CT scanning...
January 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28094853/high-dose-per-pulse-electron-beam-dosimetry-a-model-to-correct-for-the-ion-recombination-in-the-advanced-markus-ionization-chamber
#9
Kristoffer Petersson, Maud Jaccard, Jean-François Germond, Thierry Buchillier, François Bochud, Jean Bourhis, Marie-Catherine Vozenin, Claude Bailat
PURPOSE: The purpose of this work was to establish an empirical model of the ion recombination in the Advanced Markus ionization chamber for measurements in high dose rate/dose-per-pulse electron beams. In addition, we compared the observed ion recombination to calculations using the standard Boag two-voltage-analysis method, the more general theoretical Boag models, and the semi-empirical general equation presented by Burns and McEwen. METHODS: Two independent methods were used to investigate the ion recombination: 1) Varying the grid tension of the linear accelerator (linac) gun (controls the linac output) and measuring the relative effect the grid tension has on the chamber response at different source-to-surface distances (SSD)...
January 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28094850/discriminating-solitary-cysts-from-soft-tissue-lesions-in-mammography-using-a-pretrained-deep-convolutional-neural-network
#10
Thijs Kooi, Bram van Ginneken, Nico Karssemeijer, Ard den Heeten
PURPOSE: It is estimated that 7% of women in the western world will develop palpable breast cysts in their lifetime. Even though cysts have been correlated with risk of developing breast cancer, many of them are benign and do not require follow-up. We develop a method to discriminate benign solitary cysts from malignant masses in digital mammography. We think a system like this can have merit in the clinic as a decision aid or complementary to specialised modalities. METHODS: We employ a deep Convolutional Neural Network (CNN) to classify cyst and mass patches...
January 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28094849/the-collimator-monitoring-fill-factor-of-a-two-dimensional-detector-array-a-measure-of-its-ability-to-detect-collimation-errors
#11
Tenzin Sonam Stelljes, Hui Khee Looe, Dietrich Harder, Björn Poppe
PURPOSE: Two-dimensional detector arrays are routinely used for constancy checks and treatment plan verification in photon-beam radiotherapy. In addition to the spatial resolution of the dose profiles, the "coverage" of the radiation field with respect to the detection of any beam collimation deficiency appears as the second characteristic feature of a detector array. The here proposed "collimator monitoring fill factor" (CM fill factor) has been conceived to serve as a quantitative characteristic of this "coverage"...
January 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28090633/magnetic-field-effects-on-particle-beams-and-their-implications-for-dose-calculation-in-mr-guided-particle-therapy
#12
Hermann Fuchs, Philipp Moser, Martin Gröschl, Dietmar Georg
PURPOSE: To investigate and model effects of magnetic fields on proton and carbonion beams for dose calculation. METHODS: In a first step Monte Carlo simulations using Gate 7.1/Geant4.10.0.p03 were performed for proton and carbon ion beams in magnetic fields ranging from 0 to 3 T. Initial particle energies ranged from 60-250 MeV (protons) and 120-400 MeV/u (carbon ions), respectively. The resulting dose distributions were analyzed focusing on beam deflection, dose deformation as well as the impact of material het- erogeneities...
January 16, 2017: Medical Physics
https://www.readbyqxmd.com/read/28079267/estimating-4d-cbct-from-prior-information-and-extremely-limited-angle-projections-using-structural-pca-and-weighted-free-form-deformation-for-lung-radiotherapy
#13
Wendy Harris, You Zhang, Fang-Fang Yin, Lei Ren
PURPOSE: To investigate the feasibility of using structural-based principal component analysis (PCA) motion-modeling and weighted free-form deformation to estimate on-board 4D-CBCT using prior information and extremely limited angle projections for potential 4D target verification of lung radiotherapy. METHODS: A technique for lung 4D-CBCT reconstruction has been previously developed using a deformation field map (DFM)-based strategy. In the previous method, each phase of the 4D-CBCT was generated by deforming a prior CT volume...
January 12, 2017: Medical Physics
https://www.readbyqxmd.com/read/28079264/electromagnetic-computation-and-modeling-in-mri
#14
REVIEW
Xin Chen, Michael Steckner
Electromagnetic (EM) computational modeling is used extensively during the development of a Magnetic Resonance Imaging (MRI) scanner, its installation, and use. MRI, which relies on interactions between nuclear magnetic moments and the applied magnetic fields, uses a range of EM tools to optimize all of the magnetic fields required to produce the image. The main field magnet is designed to exacting specifications but challenges in manufacturing, installation, and use require additional tools to maintain target operational performance...
January 12, 2017: Medical Physics
https://www.readbyqxmd.com/read/28079260/an-experimentally-validated-couch-and-mlc-tracking-simulator-used-to-investigate-hybrid-couch-mlc-tracking
#15
Jakob Toftegaard, Rune Hansen, Thomas Ravkilde, Kristijan Macek, Per Rugaard Poulsen
PURPOSE/OBJECTIVE: Couch and MLC tracking are two novel techniques to mitigate intrafractional tumor motion on a conventional linear accelerator, but both techniques still have residual dosimetric errors. Here, we first propose and experimentally validate a software tool to simulate couch and MLC tracking, and then use the simulator to study hybrid couch-MLC tracking for improved tracking performance. MATERIALS AND METHODS: The tracking simulator requires a treatment plan and a motion trajectory as input and simulates the delivered monitor units and motion of all accelerator parts as function of time...
January 12, 2017: Medical Physics
https://www.readbyqxmd.com/read/28079257/a-safe-cheap-and-easy-to-use-isotropic-diffusion-mri-phantom-for-clinical-and-multicenter-studies
#16
Pim Pullens, Piet Bladt, Jan Sijbers, Andrew I R Maas, Paul M Parizel
PURPOSE: Since Diffusion Weighted Imaging (DWI) data acquisition and processing are not standardized, substantial differences in DWI derived measures such as Apparent Diffusion Coefficient (ADC) may arise which are related to the acquisition or MRI processing method, but not to the sample under study. Quality assurance using a standardized test object, or phantom, is a key factor in standardizing DWI across scanners. METHODS: Current diffusion phantoms are either complex to use, not available in larger quantities, contain substances unwanted in a clinical environment, or are expensive...
January 12, 2017: Medical Physics
https://www.readbyqxmd.com/read/28079249/fractal-analysis-of-visual-search-activity-for-mass-detection-during-mammographic-screening
#17
Folami Alamudun, Hong-Jun Yoon, Kathleen B Hudson, Garnetta Morin-Ducote, Tracy Hammond, Georgia D Tourassi
PURPOSE: The objective of this study is to assess the complexity of human visual search activity during mammographic screening using fractal analysis and to investigate its relationship with case and reader characteristics. METHODS: The study was performed for the task of mammographic screening with simultaneous viewing of four coordinated breast views as typically done in clinical practice. Eye-tracking data and diagnostic decisions collected for 100 mammographic cases (25 normal, 25 benign, 50 malignant) and 10 readers (three board certified radiologists and seven radiology residents), formed the corpus data for this study...
January 12, 2017: Medical Physics
https://www.readbyqxmd.com/read/28074545/development-and-testing-of-a-database-of-nih-research-funding-of-aapm-members-a-report-from-aapm-working-group-for-the-development-of-a-research-database-wgdrd
#18
Brendan Whelan, Eduardo Moros, Rebecca Fahrig, James Deye, Thomas Yi, Michael Woodward, Paul Keall, Jeff Siewerdsen
PURPOSE: To produce and maintain a database of National Institutes of Health (NIH) funding of American Association of Physicists in Medicine (AAPM) members, to perform a top level analysis of this data, and to make this data (hereafter referred to as the AAPM research database) available for the use of the AAPM and its members. METHODS: NIH funded research dating back to 1985 is available for public download through the NIH exporter website, and AAPM membership information dating back to 2002 was supplied by the AAPM...
January 11, 2017: Medical Physics
https://www.readbyqxmd.com/read/28074528/respiratory-motion-prediction-and-prospective-correction-for-free-breathing-arterial-spin-labeled-perfusion-mri-of-the-kidneys
#19
Hao Song, Dan Ruan, Wenyang Liu, V Andrew Stenger, Rolf Pohmann, Maria A Fernandez Seara, Tejas Nair, Sungkyu Jung, Jingqin Luo, Yuichi Motai, Jingfei Ma, John D Hazle, H Michael Gach
PURPOSE: Respiratory motion prediction using an artificial neural network (ANN) was integrated with pseudocontinuous arterial spin labeling (pCASL) MRI to allow free-breathing perfusion measurements in the kidney. In this study, we evaluated the performance of the ANN to accurately predict the location of the kidneys during image acquisition. METHODS: A pencil-beam navigator was integrated with a pCASL sequence to measure lung/diaphragm motion during ANN training and the pCASL transit delay...
January 11, 2017: Medical Physics
https://www.readbyqxmd.com/read/28064435/3d-volume-reconstruction-from-serial-breast-specimen-radiographs-for-mapping-between-histology-and-3d-whole-specimen-imaging
#20
Thomy Mertzanidou, John H Hipwell, Sara Reis, David J Hawkes, Babak Ehteshami Bejnordi, Mehmet Dalmis, Suzan Vreemann, Bram Platel, Jeroen van der Laak, Nico Karssemeijer, Meyke Hermsen, Peter Bult, Ritse Mann
PURPOSE: In breast imaging, radiological in-vivo images, such as X-ray mammography and Magnetic Resonance Imaging (MRI), are used for tumour detection, diagnosis and size determination. After excision, the specimen is typically sliced into slabs and a small subset is sampled. Histopathological imaging of the stained samples is used as the gold standard for characterisation of the tumour microenvironment. A 3D volume reconstruction of the whole specimen from the 2D slabs could facilitate bridging the gap between histology and in-vivo radiological imaging...
January 8, 2017: Medical Physics
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