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Medical Physics

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https://www.readbyqxmd.com/read/29136287/quantification-of-mri-visibility-and-artefacts-at-3t-of-liquid-fiducial-marker-in-a-pancreas-tissue-mimicking-phantom
#1
Sergej Schneider, Rasmus Irming Jølck, Esther Gera Cornelia Troost, Aswin Louis Hoffmann
PURPOSE: X-ray based position verification of the target volume in image-guided radiation therapy (IGRT) of patients with pancreatic ductal adenocarcinoma (PDAC) is currently performed on solid fiducial markers that are implanted under endoscopic ultrasonography. A new biodegradable liquid fiducial marker has recently been introduced. To assess its potential use for magnetic resonance imaging (MRI) guided photon or proton radiotherapy of PDAC, the MRI visibility and artefacts of this marker were quantified and compared against solid gold markers...
November 14, 2017: Medical Physics
https://www.readbyqxmd.com/read/29136282/principal-component-reconstruction-pcr-for-cine-cbct-with-motion-learning-from-2d-fluoroscopy
#2
Hao Gao, Yawei Zhang, Lei Ren, Fang-Fang Yin
PURPOSE: This work aims to generate cine CT images (i.e., 4D images with high temporal resolution) based on a novel principal component reconstruction (PCR) technique with motion learning from 2D fluoroscopic training images. METHODS: In the proposed PCR method, the matrix factorization is utilized as an explicit low-rank regularization of 4D images that are represented as a product of spatial principal components and temporal motion coefficients. The key hypothesis of PCR is that temporal coefficients from 4D images can be reasonably approximated by temporal coefficients learned from 2D fluoroscopic training projections...
November 14, 2017: Medical Physics
https://www.readbyqxmd.com/read/29136280/transitqa-a-new-method-for-transit-dosimetry-of-tomotherapy-patients
#3
Olivier Pisaturo, Frédéric Miéville, Pierre-Alain Tercier, Abdelkarim Said Allal
PURPOSE: TransitQA is an innovative method for Tomotherapy transit dosimetry using the on-board detector (OBD). Our previously published model for Tomotherapy treatment plan verification (AirQA) has been enhanced to take into account patient and couch transmission. AirQA estimates the OBD signal during irradiation with nothing in the beam path from the leaf control sinogram, allowing us to check whether the planned treatment is correctly delivered by the machine. TransitQA allows us to check the treatment delivery with the patient on the couch, potentially showing the effects of changes in the patient anatomy and delivery errors...
November 14, 2017: Medical Physics
https://www.readbyqxmd.com/read/29134674/experimental-validation-of-two-dual-energy-ct-methods-for-proton-therapy-using-heterogeneous-tissue-samples
#4
Esther Bär, Arthur Lalonde, Rongxiao Zhang, Kyung-Wook Jee, Kai Yang, Gregory Sharp, Bob Liu, Gary Royle, Hugo Bouchard, Hsiao-Ming Lu
PURPOSE: The purpose of this work is to evaluate the performance of dual-energy CT (DECT) for determining proton stopping power ratios (SPRs) in an experimental environment and to demonstrate its potential advantages over conventional single-energy CT (SECT) in clinical conditions. METHODS: Water equivalent range (WER) measurements of 12 tissue-equivalent plastic materials and 12 fresh animal tissue samples are performed in a 195 MeV broad proton beam using the dose extinction method...
November 14, 2017: Medical Physics
https://www.readbyqxmd.com/read/29131409/field-size-correction-factors-of-a-radiophotoluminescent-glass-dosimeter-for-small-field-and-intensity-modulated-radiation-therapy-beams
#5
Shimpei Hashimoto, Yukio Fujita, Tetsurou Katayose, Hideyuki Mizuno, Hidetoshi Saitoh, Katsuyuki Karasawa
PURPOSE: We evaluated the energy responses of a radiophotoluminescent glass dosimeter (RPLD) to variations in small-field and intensity-modulated radiation therapy (IMRT) conditions using experimental measurements and Monte Carlo simulation. METHODS: Several sizes of the jaw and multileaf collimator fields and various plan-class IMRT-beam measurements were performed using the RPLD and an ionization chamber. The field-size correction factor for the RPLD was determined for 6- and 10-MV X-rays...
November 13, 2017: Medical Physics
https://www.readbyqxmd.com/read/29131363/automatic-renal-lesion-segmentation-in-ultrasound-images-based-on-saliency-features-improved-lbp-and-an-edge-indicator-under-level-set-framework
#6
Luying Gui, Xiaoping Yang
PURPOSE: Segmentation of lesions in ultrasound images is widely used for preliminary diagnosis. In this paper, we develop an automatic segmentation algorithm for multiple types of lesions in ultrasound images. The proposed method is able to detect and segment lesions automatically as well as generate accurate segmentation results for lesion regions. METHODS: In the detection step, two saliency detection frameworks which adopt global image information are designed to capture the differences between normal and abnormal organs as well as these between lesions and the normal tissues around them...
November 13, 2017: Medical Physics
https://www.readbyqxmd.com/read/29131361/modeling-the-frequency-dependent-detective-quantum-efficiency-of-photon-counting-x-ray-detectors
#7
Karl Stierstorfer
PURPOSE: To find a simple model for the frequency dependent detective quantum efficiency (DQE) of photon counting detectors in the low flux limit. METHODS: Formula for the spatial crosstalk, the noise power spectrum and the DQE of a photon counting detector working at a given threshold are derived. Parameters are probabilities for types of events like single counts in the central pixel, double counts in the central pixel and a neighboring pixel or single count in a neighboring pixel only...
November 13, 2017: Medical Physics
https://www.readbyqxmd.com/read/29131353/accelerated-nonrigid-motion-compensated-isotropic-3d-coronary-mr-angiography
#8
Teresa Correia, Gastão Cruz, Torben Schneider, René M Botnar, Claudia Prieto
PURPOSE: To develop an accelerated and nonrigid motion compensated technique for efficient isotropic 3D whole-heart coronary magnetic resonance angiography (CMRA) with Cartesian acquisition. METHODS: Highly efficient whole-heart 3D CMRA was achieved by combining image reconstruction from undersampled data using compressed sensing (CS) with a nonrigid motion compensation framework. Undersampled acquisition was performed using a variable-density Cartesian trajectory with radial order (VD-CAPR)...
November 13, 2017: Medical Physics
https://www.readbyqxmd.com/read/29131351/ion-recombination-and-polarity-correction-factors-for-a-plane-parallel-ionization-chamber-in-a-proton-scanning-beam
#9
Małgorzata Liszka, Liliana Stolarczyk, Magdalena Kłodowska, Anna Kozera, Dawid Krzempek, Natalia Mojżeszek, Anna Pędracka, Michael Patrick Russell Waligórski, Paweł Olko
PURPOSE: To evaluate the effect on charge collection in the ionization chamber (IC) in proton pencil beam scanning (PBS), where the local dose-rate may exceed the dose rates encountered in conventional MV therapy by up to 3 orders of magnitude. METHODS: We measured values of the ion recombination (ks ) and polarity (kpol ) correction factors in water, for a plane-parallel Markus TM23343 IC, using the cyclotron-based Proteus-235 therapy system with an active proton PBS of energies 30-230 MeV...
November 13, 2017: Medical Physics
https://www.readbyqxmd.com/read/29131346/evaluation-of-the-latency-and-the-beam-characteristics-of-a-respiratory-gating-system-using-an-elekta-linear-accelerator-and-a-respiratory-indicator-device-abches
#10
Masahide Saito, Naoki Sano, Koji Ueda, Yuki Shibata, Kengo Kuriyama, Takafumi Komiyama, Kan Marino, Shinichi Aoki, Hiroshi Onishi
PURPOSE: To evaluate the basic performance of a respiratory gating system using an Elekta linac and an Abches respiratory monitoring device. METHODS: The gating system was comprised of an Elekta Synergy linac equipped with a Response(TM) gating interface module and an Abches respiratory monitoring device. The latencies from a reference respiratory signal to the resulting Abches gating output signal and the resulting monitor-ion-chamber output signal were measured...
November 13, 2017: Medical Physics
https://www.readbyqxmd.com/read/29131344/aerrow-a-probe-format-graphite-calorimeter-for-absolute-dosimetry-of-high-energy-photon-beams-in-the-clinical-environment
#11
James Renaud, Arman Sarfehnia, Julien Bancheri, Jan Seuntjens
In this work, the design, operation, initial experimental evaluation, and characterization of a small-scale graphite calorimeter probe - herein referred to as the Aerrow - developed for routine use in the clinical environment, is described. Similar in size and shape to a Farmer type cylindrical ionization chamber, the Aerrow represents the first translation of calorimetry intended for direct use by clinical physicists in the radiotherapy clinic METHODS: Based on a numerically-optimized design obtained in previous work, a functioning Aerrow prototype capable of two independent modes of operation (quasi-adiabatic and isothermal) was constructed in-house...
November 13, 2017: Medical Physics
https://www.readbyqxmd.com/read/29131343/extracting-wair-from-the-electron-beam-measurements-of-domen-and-lamperti
#12
Frédéric Tessier, Claudiu Dorin Cojocaru, Carl Kenneth Ross
PURPOSE: The average energy expended by an energetic electron to create an ion pair in dry air, Wair, is a key quantity in radiation dosimetry. Although Wair is well established for electron energies up to about 3 MeV there is limited data for higher energies. The measurements by Domen and Lamperti [Med. Phys. 3, 294{301 (1976)] using electron beams in the energy range from 15 to 50 MeV can, in principle, be used to deduce values for Wair, if the electron stopping power of graphite and air are known...
November 13, 2017: Medical Physics
https://www.readbyqxmd.com/read/29121409/image-quality-and-dose-for-a-multi-source-cone-beam-ct-extremity-scanner
#13
Grace Jianan Gang, Wojciech Zbijewski, Mahadevappa Mahesh, Gaurav Thawait, Nathan Packard, John Yorkston, Shadpour Demehri, Jeffrey Harrold Siewerdsen
PURPOSE: This work investigates the dose characteristics and image quality of a multi-source cone-beam CT scanner dedicated for extremity imaging. METHODS: The scanner has an x-ray source with three separate anode-cathode units evenly distributed along the longitudinal direction. A nominal scan protocol fires the three sources sequentially, and a total of 600 projections (200 for each source) are acquired over a source-detector orbit of 210(o) . Dose was measured using a Farmer chamber in three CTDI phantoms stacked end-to-end...
November 9, 2017: Medical Physics
https://www.readbyqxmd.com/read/29121397/virtual-phantom-magnetic-resonance-imaging-vip-mri-on-a-clinical-mri-platform
#14
Hervé Saint-Jalmes, Alejandro Bordelois, Giulio Gambarota
PURPOSE: To implement Virtual Phantom Magnetic Resonance Imaging (ViP MRI), a technique that allows for generating reference signals in MR images using radiofrequency (RF) signals, on a clinical MR system and to test newly designed virtual phantoms. METHODS: MRI experiments were conducted on a 1.5 T MRI scanner. Electromagnetic modelling of the ViP system was done using the Principle of Reciprocity. The ViP RF signals were generated using a compact waveform generator (dimensions of 26cm x 18cm x 16cm), connected to a home-built 25mm-diameter RF coil...
November 9, 2017: Medical Physics
https://www.readbyqxmd.com/read/29106741/development-and-characterization-of-a-handheld-hyperspectral-raman-imaging-probe-system-for-molecular-characterization-of-tissue-on-mesoscopic-scales
#15
Karl St-Arnaud, Kelly Aubertin, Mathias Strupler, Wendy-Julie Madore, Andrée-Anne Grosset, Kevin Petrecca, Dominique Trudel, Frédéric Leblond
PURPOSE: Raman spectroscopy is a promising cancer detection technique for surgical guidance applications. It can provide quantitative information relating to global tissue properties associated with structural, metabolic, immunological and genetic biochemical phenomena in terms of molecular species including amino acids, lipids, proteins, and nucleic acid (DNA). To date in vivo Raman spectroscopy systems mostly included probes and biopsy needles typically limited to single-point tissue interrogation over a scale between 100 and 500 microns...
November 6, 2017: Medical Physics
https://www.readbyqxmd.com/read/29106739/evaluation-of-tomotherapy-dose-calculations-with-intra-fractional-motion-and-motion-compensation
#16
Edward H Chao, Daniel Lucas, Eric Schnarr
PURPOSE: Anatomical motion, both cyclical and aperiodic, can impact the dose delivered during external beam radiation. In this work, we evaluate the use of a research version of the clinical TomoTherapy(®) dose calculator to calculate dose with intra-fraction rigid motion. We also evaluate the feasibility of a method of motion compensation for helical tomotherapy using the jaws and MLC. METHODS: Treatment plans were created using the TomoTherapy treatment planning system...
November 6, 2017: Medical Physics
https://www.readbyqxmd.com/read/29106708/surface-applicator-of-a-miniature-x-ray-tube-for-superficial-electronic-brachytherapy-of-skin-cancer
#17
Hyun Nam Kim, Ju Hyuk Lee, Han Beom Park, Hyun Jin Kim, Sung Oh Cho
PURPOSE: We designed and fabricated a surface applicator of a novel carbon nanotube (CNT) based miniature X-ray tube for the use in superficial electronic brachytherapy of skin cancer. To investigate the effectiveness of the surface applicator, the performance of the applicator was numerically and experimentally analyzed. METHODS: The surface applicator consists of a graphite flattening filter and an X-ray shield. A Monte Carlo radiation transport code, MCNP6, was used to optimize the geometries of both the flattening filter and the shield so that X-rays are generated uniformly over the desired region...
November 6, 2017: Medical Physics
https://www.readbyqxmd.com/read/29105791/implementation-of-dosimetry-equipment-and-phantoms-at-the-medaustron-light-ion-beam-therapy-facility
#18
Loϊc Grevillot, Markus Stock, Hugo Palmans, Jhonnatan Osorio Moreno, Virgile Letellier, Ralf Dreindl, Alessio Elia, Hermann Fuchs, Antonio Carlino, Stanislav Vatnitsky
PURPOSE: To describe the implementation of dosimetry equipment and phantoms into clinical practice of light ion beam therapy facilities. This work covers standard dosimetry equipment such as computerized water scanners, films, 2D-array, thimble and plane parallel ionization chambers, but also dosimetry equipment specifically devoted to the pencil beam scanning delivery technique such as water columns, scintillating screens or multi-layer ionization chambers. METHOD: Advanced acceptance testing procedures developed at MedAustron and complementary to the standard acceptance procedures proposed by the manufacturer are presented...
November 4, 2017: Medical Physics
https://www.readbyqxmd.com/read/29105093/technical-note-parallel-implementation-of-the-egsnrc-monte-carlo-simulation-of-ionizing-radiation-transport-using-openmp
#19
Edgardo Doerner, Paola Caprile
PURPOSE: To present the implementation of a new option for parallel processing of the EGSnrc Monte Carlo system using the OpenMP API, as an alternative to the provided method based on the use of a batch queuing system (BQS). METHODS: The parallel solution presented, called OMP_ EGS, makes use of OpenMP features to control the workload distribution between the compute units. These features were inserted into the original EGSnrc source code through properly defined macros...
November 4, 2017: Medical Physics
https://www.readbyqxmd.com/read/29095489/modeling-and-evaluation-of-a-high-resolution-cmos-detector-for-cone-beam-ct-of-the-extremities
#20
Qian Cao, Alejandro Sisniega, Michael Brehler, J Webster Stayman, John Yorkston, Jeffrey H Siewerdsen, Wojciech Zbijewski
PURPOSE: Quantitative assessment of trabecular bone microarchitecture in extremity cone-beam CT (CBCT) would benefit from the high spatial resolution, low electronic noise, and fast scan time provided by complementary metal-oxide semiconductor (CMOS) x-ray detectors. We investigate the performance of CMOS sensors in extremity CBCT, in particular with respect to potential advantages of thin (<0.7 mm) scintillators offering higher spatial resolution. METHODS: A cascaded systems model of a CMOS x-ray detector incorporating the effects of CsI:Tl scintillator thickness was developed...
November 2, 2017: Medical Physics
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