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Medical Physics

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https://www.readbyqxmd.com/read/29344955/development-of-an-advanced-two-dimensional-microdosimetric-detector-based-on-thick-gas-electron-multipliers
#1
Sahar Darvish-Molla, William V Prestwich, Soo Hyun Byun
PURPOSE: The THick Gas Electron Multiplier (THGEM) based tissue-equivalent proportional counter (TEPC) has been proven to be useful for microdosimetry due to its flexibility in varying the gaseous sensitive volume and achieving high multiplication gain. Aiming at measuring the spatial distribution of radiation dose for mixed neutron-gamma fields, an advanced two-dimensional (2-D) THGEM TEPC was designed and constructed at McMaster University which will enable us to overcome the operational limitation of the classical TEPCs, particularly for high dose rate fields...
January 18, 2018: Medical Physics
https://www.readbyqxmd.com/read/29322528/mr-and-ct-data-with-multi-observer-delineations-of-organs-in-the-pelvic-area-part-of-the-gold-atlas-project
#2
Tufve Nyholm, Stina Svensson, Sebastian Andersson, Joakim Jonsson, Maja Sohlin, Christian Gustafsson, Elisabeth Kjellén, Karin Söderström, Per Albertsson, Lennart Blomqvist, Björn Zackrisson, Lars E Olsson, Adalsteinn Gunnlaugsson
PURPOSE: We describe a public dataset with MR and CT images of patients performed in the same position with both multi observer and expert consensus delineations of relevant organs in the male pelvic region. The purpose is to provide means for training and validation of segmentation algorithms and methods to convert MR to CT like data, i.e., so called synthetic CT (sCT). ACQUISITION AND VALIDATION METHODS: T1 and T2 weighted MR images as well as CT data was collected for 19 patients at three different departments...
January 11, 2018: Medical Physics
https://www.readbyqxmd.com/read/29319842/quantitative-evaluation-of-potential-irradiation-geometries-for-carbon-ion-beam-grid-therapy
#3
Toshiro Tsubouchi, Thomas Henry, Ana Ureba, Alexander Valdman, Niels Bassler, Albert Siegbahn
PURPOSE: Radiotherapy using grids containing cm-wide beam elements has been carried out sporadically for more than a century. During the past two decades, preclinical research on radiotherapy with grids containing small beam elements, 25 μm - 0.7 mm wide, has been performed. Grid therapy with larger beam elements is technically easier to implement, but the normal-tissue tolerance to the treatment is decreasing. In this work, a new approach in grid therapy, based on irradiations with grids containing narrow carbon-ion beam elements was evaluated dosimetrically...
January 10, 2018: Medical Physics
https://www.readbyqxmd.com/read/29314080/a-simple-model-for-transit-dosimetry-based-on-a-water-equivalent-epid
#4
S Deshpande, S J Blake, A Xing, P E Metcalfe, L C Holloway, P Vial
PURPOSE: To demonstrate a new model for implementing a transit dosimetry system as a means of in vivo dose verification with a water-equivalent electronic portal imaging device (WE-EPID) and a conventional treatment planning system (TPS). METHOD AND MATERIALS: A standard amorphous silicon (a-Si) EPID was modified to a WE-EPID configuration by replacing the metal-plate/phosphor screen situated above the photodiode detector with a 3 cm thick water equivalent plastic x-ray converter material...
January 3, 2018: Medical Physics
https://www.readbyqxmd.com/read/29314060/dynamic-field-of-view-imaging-to-increase-temporal-resolution-in-the-early-phase-of-contrast-media-uptake-in-breast-dce-mri-a-feasibility-study
#5
Federico D Pineda, Ty O Easley, Gregory S Karczmar
PURPOSE: To increase diagnostic accuracy of breast MRI by increasing temporal resolution and more accurately sampling the early kinetics of contrast media uptake. We tested the feasibility of accelerating bilateral breast DCE-MRI by reducing the FOV, allowing aliasing, and unfolding the resulting images. METHODS: Previous experience with an 'ultrafast' protocol for bilateral breast DCE-MRI (6s-10s temporal resolution) showed that the number of significantly enhancing voxels is very low in the first 30 to 45 seconds after contrast media injection...
January 3, 2018: Medical Physics
https://www.readbyqxmd.com/read/29314058/impact-of-using-scatter-mimicking-beams-instead-of-standard-beams-to-measure-penetration-when-assessing-the-protective-value-of-radiation-protective-garments
#6
A Kyle Jones, Alexander S Pasciak, Louis K Wagner
PURPOSE: Use standardized methods to determine how assessment of protective value of radiation-protective garments changes under conditions employing standard beam qualities, scatter-mimicking primary beams, and a modified Hp (10) measurement. METHODS: The shielding properties of radiation-protective garments depend on the spectrum of beam energies striking the garment and the attenuation properties of materials used to construct the garment, including X-ray fluorescence produced by these materials...
January 3, 2018: Medical Physics
https://www.readbyqxmd.com/read/29314051/water-equivalent-presage%C3%A2-for-synchrotron-radiation-therapy-dosimetry
#7
Frank M Gagliardi, Liam Day, Christopher M Poole, Rick D Franich, Moshi Geso
PURPOSE: Synchrotron Radiation Therapy techniques are currently being trialled and commissioned at synchrotrons around the world. The patient treatment planning systems (TPS) developed for these treatments use simulated data of the synchrotron x-ray beam to produce the dosimetry in the treatment plan. The purpose of this study was to investigate a water equivalent PRESAGE® dosimeter capable of 3D dosimetry over an energy range suitable for synchrotron x-ray beams. METHODS: Water equivalent PRESAGE® dosimeters were fabricated with a radiological effective atomic number similar to water over an energy range of 10 keV to 10 MeV...
January 3, 2018: Medical Physics
https://www.readbyqxmd.com/read/29297939/technical-note-the-impact-of-deformable-image-registration-methods-on-dose-warping
#8
An Qin, Jian Liang, Xiao Han, Nicolette O'Connell, Di Yan
PURPOSE: To investigate the clinical-relevant discrepancy between doses warped by pure-image based deformable image registration (IM-DIR) and by biomechanical-model based DIR (BM-DIR) on intensity homogeneous organs. METHODS AND MATERIALS: Ten patients (5Head&Neck, 5Prostate) were included. A research DIR tool (ADMRIE_v1.12) was utilized for IM-DIR. After IM-DIR, BM-DIR was carried out for organs (parotids, bladder, and rectum) which often encompass sharp dose gradient...
January 3, 2018: Medical Physics
https://www.readbyqxmd.com/read/29266262/performance-of-commercially-available-deformable-image-registration-platforms-for-contour-propagation-using-patient-based-computational-phantoms-a-multi-institutional-study
#9
Gianfranco Loi, Marco Fusella, Eleonora Lanzi, Elisabetta Cagni, Cristina Garibaldi, Giuseppina Iacoviello, Francesco Lucio, Enrico Menghi, Roberto Miceli, Lucia C Orlandini, Antonella Roggio, Federica Rosica, Michele Stasi, Lidia Strigari, Silvia Strolin, Christian Fiandra
PURPOSE: To investigate the performance of various algorithms for deformable image registration (DIR) to propagate regions of interest (ROIs) using multiple commercial platforms. METHODS AND MATERIALS: Thirteen institutions participated in the study with six commercial platforms: RayStation (RaySearch Laboratories, Stockholm, Sweden), MIM (Cleveland, OH), VelocityAI and Smart Adapt (Varian Medical Systems, Palo Alto, CA), Mirada XD (Mirada Medical Ltd, Oxford, UK) and ABAS (Elekta AB, Stockholm, Sweden)...
December 20, 2017: Medical Physics
https://www.readbyqxmd.com/read/29265558/a-silicon-strip-detector-array-for-energy-verification-and-quality-assurance-in-heavy-ion-therapy
#10
Emily Debrot, Matthew Newall, Susanna Guatelli, Marco Petasecca, Naruhiro Matsufuji, Anatoly B Rosenfeld
PURPOSE: The measurement of depth dose profiles for range and energy verification of heavy ion beams is an important aspect of quality assurance procedures for heavy ion therapy facilities. The steep dose gradients in the Bragg peak region of these profiles require the use of detectors with high spatial resolution. The aim of this work is to characterise a one dimensional monolithic silicon detector array called the "serial Dose Magnifying Glass" (sDMG) as an independent ion beam energy and range verification system used for quality assurance conducted for ion beams used in heavy ion therapy...
December 19, 2017: Medical Physics
https://www.readbyqxmd.com/read/29265414/technical-note-comparison-of-first-and-second-generation-photon-counting-slit-scanning-tomosynthesis-systems
#11
Karl Berggren, Björn Cederström, Mats Lundqvist, Erik Fredenberg
PURPOSE: Digital breast tomosynthesis (DBT) is an emerging tool for breast-cancer screening and diagnostics. The purpose of this study is to present a second-generation photon-counting slit-scanning DBT system and compare it to the first-generation system in terms of geometry and image quality. The study presents the first imagequality measurements on the second-generation system. METHOD: The geometry of the new system is based on a combined rotational and linear motion, in contrast to a purely rotational scan motion in the first generation...
December 19, 2017: Medical Physics
https://www.readbyqxmd.com/read/29251777/an-adaptive-motion-regularization-technique-to-support-sliding-motion-in-deformable-image-registration
#12
Yabo Fu, Shi Liu, H Harold Li, Hua Li, Deshan Yang
PURPOSE: Isotropic smoothing has been conventionally used to regularize deformation vector fields (DVFs) in deformable image registration (DIR). However, the isotropic smoothing method enforces global smoothness and therefore cannot accurately model the complex tissue deformation, such as sliding motion at organ boundaries. To accurately model and estimate sliding tissue motion, an adaptive direction-dependent DVF regularization technique was developed in this study. METHODS: A DVF is computed and updated iteratively by minimizing the intensity differences between the images...
December 18, 2017: Medical Physics
https://www.readbyqxmd.com/read/29244904/pharmacokinetics-of-the-cannabinoid-receptor-ligand-18-f-mk-9470-in-the-rat-brain-evaluation-of-models-using-micropet
#13
Isabelle Miederer, Hans-Georg Buchholz, Andrea Kronfeld, Stephan Maus, Veronika Weyer-Elberich, Philipp Mildenberger, Beat Lutz, Mathias Schreckenberger
PURPOSE: The positron emission tomography ligand [18 F]MK-9470 is an inverse agonist that binds reversibly and with high affinity to the cannabinoid type 1 receptor. Due to its slow brain kinetics, care is required in the definition of its dissociation rates from the receptor. The goal of this study was to investigate pharmacokinetic analysis methods using an arterial input function. METHODS: Five Sprague-Dawley rats received injections of 13 to 25 MBq of [18 F]MK-9470 and were scanned over a period of 90 min...
December 15, 2017: Medical Physics
https://www.readbyqxmd.com/read/29244902/feasibility-of-predicting-tumor-motion-using-online-data-acquired-during-treatment-and-a-generalized-neural-network-optimized-with-offline-patient-tumor-trajectories
#14
Troy Teo, Syed Bilal Ahmed, Nadia Alayoubi, Neil Bruce, Ethan Lyn, Stephen Pistorius
PURPOSE: The accurate prediction of intra-fraction lung tumor motion is required to compensate for system latency in image-guided adaptive radiotherapy systems. The goal of this study was to identify an optimal prediction model that has a short learning period so that prediction and adaptation can commence soon after treatment begins, and requires minimal re-optimization for individual patients. Specifically, the feasibility of predicting tumor position using a combination of a generalized (i...
December 15, 2017: Medical Physics
https://www.readbyqxmd.com/read/29244899/spatial-response-of-synthetic-microdiamond-and-diode-detectors-measured-with-kilovoltage-synchrotron-radiation
#15
Duncan J Butler, Toby Beveridge, Joerg Lehmann, Christopher P Oliver, Andrew W Stevenson, Jayde Livingstone
PURPOSE: To map the spatial response of four solid-state radiation detectors of types commonly used for radiotherapy dosimetry. METHODS: PTW model 60016 Diode P, 60017 Diode E, 60018 Diode SRS and 60019 microDiamond detectors were radiographed using a high resolution conventional X-ray system. Their spatial response was then investigated using a 0.1 mm diameter beam of 95 keV average energy photons generated by a synchrotron. The detectors were scanned through the beam while their signal was recorded as a function of position, to map the response...
December 15, 2017: Medical Physics
https://www.readbyqxmd.com/read/29239005/automated-image-quality-assessment-for-chest-ct-scans
#16
Anthony P Reeves, Yiting Xie, Shuang Liu
PURPOSE: Medical image quality needs to be maintained at standards sufficient for effective clinical reading. Automated computer analytic methods may be applied to medical images for quality assessment. METHODS: For chest CT scans in a lung cancer screening context, an automated quality assessment method is presented that characterizes image noise and image intensity calibration. This is achieved by image measurements in three automatically segmented homogeneous regions of the scan: external air, trachea lumen air, and descending aorta blood...
December 14, 2017: Medical Physics
https://www.readbyqxmd.com/read/29238999/physiological-gas-exchange-mapping-of-hyperpolarized-129-xe-using-spiral-ideal-and-moxe-in-a-model-of-regional-radiation-induced-lung-injury
#17
Brandon Zanette, Elaine Stirrat, Salomeh Jelveh, Andrew Hope, Giles Santyr
PURPOSE: To map physiological gas exchange parameters using dissolved hyperpolarized (HP) 129 Xe in a rat model of regional radiation-induced lung injury (RILI) with spiral-IDEAL and the model of xenon exchange (MOXE). Results are compared to quantitative histology of pulmonary tissue and red blood cell (RBC) distribution. METHODS: Two cohorts (n=6 each) of age-matched rats were used. One was irradiated in the right-medial lung, producing regional injury. Gas exchange was mapped four weeks post-irradiation by imaging dissolved-phase HP 129 Xe using spiral-IDEAL at five gas exchange timepoints using a clinical 1...
December 14, 2017: Medical Physics
https://www.readbyqxmd.com/read/29237238/directional-probe-for-radio-guided-surgery-a-pilot-study
#18
Roberto Massari, Antonio Ucci, Annunziata D'Elia, Costantino Campisi, Emilio Bertani, Alessandro Soluri
The sentinel lymph node (SLN) biopsy technique has highly evolved during the last twenty years. Consequently, the intraoperative use of Gamma Probes (GPs) for SLN mapping is increased. This preliminary study evaluates a novel directional GP prototype. This proof-of-concept prototype is designed to identify the direction of radiopharmaceuticals uptakes, by combining the information from multiple detectors. The purpose of this work is to develop a tool able to effectively guide the surgeon reducing the surgery time...
December 13, 2017: Medical Physics
https://www.readbyqxmd.com/read/29237232/3d-printed-phantoms-mimicking-cortical-bone-for-the-assessment-of-ultrashort-echo-time-magnetic-resonance-imaging
#19
Robba Rai, David Manton, Michael G Jameson, Sonal Josan, Michael B Barton, Lois C Holloway, Gary P Liney
PURPOSE: Human cortical bone has a rapid T2 * decay, and it can be visualised using ultrashort echo time (UTE) techniques in magnetic resonance imaging (MRI). These sequences operate at the limits of gradient and transmit-receive signal performance. Development of multicompartment anthropomorphic phantoms that can mimic human cortical bone can assist with quality assurance and optimisation of UTE sequences. The aims of this study were to 1) characterise the MRI signal properties of a photopolymer resin that can be 3D printed, 2) develop multi-compartment phantoms based on the resin, and 3) demonstrate the feasibility of using these phantoms to mimic human anatomy in the assessment of UTE sequences...
December 13, 2017: Medical Physics
https://www.readbyqxmd.com/read/29235131/measured-and-monte-carlo-simulated-surface-dose-reduction-for-superficial-x-rays-incident-on-tissue-with-underlying-air-or-bone
#20
John Baines, Sylwia Zawlodzka, Tim Markwell, Millicent Chan
PURPOSE: Measurement of surface dose reduction effects for superficial x-rays incident on tissue with underlying air or bone and comparison with Monte Carlo simulations of such effects. Further to investigate the correlation between surface dose reduction and changes in Compton backscatter spectra with tissue-bone separation. METHODS: An Advanced Markus chamber with entrance window facing downstream on the surface of a solid water phantom was used to investigate changes in surface dose with an underlying air or bone interface located at various depths below the surface...
December 12, 2017: Medical Physics
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