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Journal of Applied Clinical Medical Physics

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https://www.readbyqxmd.com/read/29790261/-characterization-of-elekta-srs-cone-collimator-using-high-spatial-resolution-monolithic-silicon-detector-array
#1
Khalsa Al Shukaili, Stéphanie Corde, Marco Petasecca, Vladimir Pereveratylo, Michael Lerch, Michael Jackson, Anatoly Rosenfeld
PURPOSE: To investigate the accuracy of the dosimetry of radiation fields produced by small ELEKTA cone collimators used for stereotactic radiosurgery treatments (SRS) using commercially available detectors EBT3 GafchromicTM film, IBA Stereotactic diode (SFD), and the recently developed detector DUO, which is a monolithic silicon orthogonal linear diode array detector. METHODS: These three detectors were used for the measurement of beam profiles, output factors, and percentage depth dose for SRS cone collimators with cone sizes ranging from 5 to 50 mm diameter...
May 22, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29785839/optimization-of-a-secondary-voi-protocol-for-lung-imaging-in-a-clinical-ct-scanner
#2
Thomas C Larsen, Vissagan Gopalakrishnan, Jianhua Yao, Catherine P Nguyen, Marcus Y Chen, Joel Moss, Han Wen
We present a solution to meet an unmet clinical need of an in-situ "close look" at a pulmonary nodule or at the margins of a pulmonary cyst revealed by a primary (screening) chest CT while the patient is still in the scanner. We first evaluated options available on current whole-body CT scanners for high resolution screening scans, including ROI reconstruction of the primary scan data and HRCT, but found them to have insufficient SNR in lung tissue or discontinuous slice coverage. Within the capabilities of current clinical CT systems, we opted for the solution of a secondary, volume-of-interest (VOI) protocol where the radiation dose is focused into a short-beam axial scan at the z position of interest, combined with a small-FOV reconstruction at the xy position of interest...
May 21, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29785834/development-of-a-robust-mri-fiducial-system-for-automated-fusion-of-mr-us-abdominal-images
#3
Christopher P Favazza, Krzysztof R Gorny, Matthew R Callstrom, Anil N Kurup, Michael Washburn, Pamela S Trester, Charles L Fowler, Nicholas J Hangiandreou
We present the development of a two-component magnetic resonance (MR) fiducial system, that is, a fiducial marker device combined with an auto-segmentation algorithm, designed to be paired with existing ultrasound probe tracking and image fusion technology to automatically fuse MR and ultrasound (US) images. The fiducial device consisted of four ~6.4 mL cylindrical wells filled with 1 g/L copper sulfate solution. The algorithm was designed to automatically segment the device in clinical abdominal MR images...
May 21, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29785729/tg-51-reference-dosimetry-for-the-halcyon%C3%A2-a-clinical-experience
#4
Samantha A M Lloyd, Tze Yee Lim, Xenia Fave, Everardo Flores-Martinez, Todd F Atwood, Vitali Moiseenko
Halcyon™ is a single-energy (6 MV-FFF), bore-enclosed linear accelerator. Patient setup is performed by first aligning to external lasers mounted to the front of the bore, and then loading to isocenter through pre-defined couch shifts. There is no light field, optical distance indicator or front pointer mechanism, so positioning is verified through MV imaging with kV imaging scheduled to become available in the future. TG-51 reference dosimetry was successfully performed for Halcyon™ in this imaging-based setup paradigm...
May 21, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29785725/density-scaling-of-phantom-materials-for-a-3d-dose-verification-system
#5
Kensuke Tani, Yukio Fujita, Akihisa Wakita, Ryohei Miyasaka, Ryuzo Uehara, Takumi Kodama, Yuya Suzuki, Ako Aikawa, Norifumi Mizuno, Jiro Kawamori, Hidetoshi Saitoh
In this study, the optimum density scaling factors of phantom materials for a commercially available three-dimensional (3D) dose verification system (Delta4) were investigated in order to improve the accuracy of the calculated dose distributions in the phantom materials. At field sizes of 10 × 10 and 5 × 5 cm2 with the same geometry, tissue-phantom ratios (TPRs) in water, polymethyl methacrylate (PMMA), and Plastic Water Diagnostic Therapy (PWDT) were measured, and TPRs in various density scaling factors of water were calculated by Monte Carlo simulation, Adaptive Convolve (AdC, Pinnacle3 ), Collapsed Cone Convolution (CCC, RayStation), and AcurosXB (AXB, Eclipse)...
May 21, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29781165/dose-rate-response-of-digital-megavolt-imager-detector-for-flattening-filter-free-beams
#6
Zhigang Xu, Jinkoo Kim, James Han, An Ting Hsia, Samuel Ryu
In this study we investigated the dose rate response characteristics of the Digital Megavolt Imager (DMI) detector, including panel saturation, linearity, and imager ghosting effects for flattening filter-free (FFF) beams. The DMI detector dose rate response characteristics were measured as a function of dose rate on a Varian TrueBeam machine. Images were acquired at dose rates ranging from 400 to 1400 MU/min for 6XFFF and 400 to 2400 MU/min for 10XFFF. Line profiles and central portal doses derived from the images were analyzed and compared...
May 21, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29781144/comp-report-cpqr-technical-quality-control-guidelines-for-conventional-radiotherapy-simulators
#7
Marie-Joëlle Bertrand
The Canadian Organization of Medical Physicists (COMP), in close partnership with the Canadian Partnership for Quality Radiotherapy (CPQR) has developed a series of Technical Quality Control (TQC) guidelines for radiation treatment equipment. These guidelines outline the performance objectives that equipment should meet in order to ensure an acceptable level of radiation treatment quality. The TQC guidelines have been rigorously reviewed and field tested in a variety of Canadian radiation treatment facilities...
May 21, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29781138/comparison-of-the-progressive-resolution-optimizer-and-photon-optimizer-in-vmat-optimization-for-stereotactic-treatments
#8
Han Liu, Benjamin Sintay, Keith Pearman, Qingyang Shang, Lane Hayes, Jacqueline Maurer, Caroline Vanderstraeten, David Wiant
The photon optimization (PO) algorithm was recently released by Varian Medical Systems to improve volumetric modulated arc therapy (VMAT) optimization within Eclipse (Version 13.5). The purpose of this study is to compare the PO algorithm with its predecessor, progressive resolution optimizer (PRO) for lung SBRT and brain SRS treatments. A total of 30 patients were selected retrospectively. Previously, all the plans were generated with the PRO algorithm within Eclipse Version 13.6. In the new version of PO algorithm (Version 15), dynamic conformal arcs (DCA) were first conformed to the target, then VMAT inverse planning was performed to achieve the desired dose distributions...
May 20, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29766643/does-the-apex-optimization-line-matter-for-single-channel-vaginal-cylinder-brachytherapy-planning
#9
Yusung Kim, Katherine Cabel, Wenqing Sun
The objective of this study is to test the impact of the use of the apex optimization line for new vaginal cylinder (VC) applicators. New single channel VC applicators (Varian) that have different top thicknesses but the same diameters as the old VC applicators (2.0 cm diameter, 2.3, 2.6, 3.0, and 3.5 cm) were compared using phantom studies. Old VC applicator plans without the apex optimization line were also compared to the plans with an apex optimization line. The apex doses were monitored at 5 mm depth doses (eight points) where a prescription dose (Rx) of 6 Gy was prescribed...
May 16, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29761625/beam-focal-spot-position-determination-for-an-elekta-linac-with-the-agility-%C3%A2-head-practical-guide-with-a-ready-to-go-procedure
#10
Jacek M Chojnowski, Lee M Taylor, Jonathan R Sykes, David I Thwaites
A novel phantomless, EPID-based method of measuring the beam focal spot offset of a linear accelerator was proposed and validated for Varian machines. In this method, one set of jaws and the MLC were utilized to form a symmetric field and then a 180o collimator rotation was utilized to determine the radiation isocenter defined by the jaws and the MLC, respectively. The difference between these two isocentres is directly correlated with the beam focal spot offset of the linear accelerator. In the current work, the method has been considered for Elekta linacs...
May 14, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29756267/evaluation-of-prototype-of-improved-electron-collimation-system-for-elekta-linear-accelerators
#11
Garrett M Pitcher, Kenneth R Hogstrom, Robert L Carver
PURPOSE: This study evaluated a new electron collimation system design for Elekta 6-20 MeV beams, which should reduce applicator weights by 25%-30%. Such reductions, as great as 3.9 kg for the largest applicator, should result in considerably easier handling by members of the radiotherapy team. METHODS: Prototype 10 × 10 and 20 × 20-cm2 applicators, used to measure weight, in-field flatness, and out-of-field leakage dose, were constructed according to the previously published design with two minor modifications: (a) rather than tungsten, lead was used for trimmer material; and (b) continuous trimmer outer-edge bevel was approximated by three steps...
May 13, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29756261/study-of-the-relationships-between-brachytherapy-plan-parameters-in-an-attempt-to-verify-total-dwell-time-in-vaginal-cylinder-applications
#12
Emmanuel O Oyekunle, Bidemi I Akinlade, Mutiu A Jimoh
PURPOSE: Source strength (Sk ), sizes of vaginal cylinder applicators (VCA), number of dwell positions (DPs), and the prescribed dose (D) are basic parameters in brachytherapy (BT) treatment planning contributing to total dwell time (TDT). This study was aimed at assessing the relationships between the specified variables in an attempt to verify the TDT in high-dose-rate (HDR) vaginal cylinder applications. METHODS: One hundred and twenty-one patients treated with Gynesource-Co60 (Bebig, Germany) using VCAs of diameters 20, 25, and 30 mm at University College Hospital, Nigeria, were enrolled in this study...
May 13, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29754467/teaching-treatment-planning-for-protons-with-educational-open-source-software-experience-with-foca-and-matrad
#13
Daniel Sanchez-Parcerisa, Jose Udías
Open-source, MATLAB-based treatment planning systems FoCa and matRAD were used in a pilot project for training prospective medical physicists and postgraduate physics students in treatment planning and beam modeling techniques for proton therapy. In the four exercises designed, students learnt how proton pencil beams are modeled and how dose is calculated in three-dimensional voxelized geometries, how pencil beam scanning plans (PBS) are constructed, the rationale behind the choice of spot spacing in patient plans, and the dosimetric differences between photon IMRT and proton PBS plans...
May 12, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29749048/evaluation-of-projection-and-dual-energy-based-methods-for-metal-artifact-reduction-in-ct-using-a-phantom-study
#14
Zaiyang Long, Michael R Bruesewitz, David R DeLone, Jonathan M Morris, Kimberly K Amrami, Mark C Adkins, Katrina N Glazebrook, James M Kofler, Shuai Leng, Cynthia H McCollough, Joel G Fletcher, Ahmed F Halaweish, Lifeng Yu
OBJECTIVES: Both projection and dual-energy (DE)-based methods have been used for metal artifact reduction (MAR) in CT. The two methods can also be combined. The purpose of this work was to evaluate these three MAR methods using phantom experiments for five types of metal implants. MATERIALS AND METHODS: Five phantoms representing spine, dental, hip, shoulder, and knee were constructed with metal implants. These phantoms were scanned using both single-energy (SE) and DE protocols with matched radiation output...
May 10, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29745011/comp-report-cpqr-technical-quality-control-guidelines-for-major-dosimetry-equipment
#15
Gérard Lagmago Kamta
The Canadian Organization of Medical Physicists (COMP), in close partnership with the Canadian Partnership for Quality Radiotherapy (CPQR) has developed a series of Technical Quality Control (TQC) guidelines for radiation treatment equipment. These guidelines outline the performance objectives that equipment should meet to ensure an acceptable level of radiation treatment quality. The TQC guidelines have been rigorously reviewed and field tested in a variety of Canadian radiation treatment facilities. The development process enables rapid review and update to keep the guidelines current with changes in technology (the most update version of this guideline can be found on the CPQR website)...
May 9, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29745009/a-fast-jaw-tracking-model-for-vmat-and-imrt-monte-carlo-simulations
#16
Reid Townson, Hilary Egglestone, Sergei Zavgorodni
Modern radiotherapy techniques involve routine use of volumetric arc therapy (VMAT) and intensity modulated radiotherapy (IMRT) with jaw-tracking - dynamic motion of the secondary collimators (jaws) in tandem with multi-leaf collimators (MLCs). These modalities require accurate dose calculations for the purposes of treatment planning and dose verification. Monte Carlo (MC) methods for radiotherapy dose calculation are widely accepted as capable of achieving high accuracy. This paper presents an efficiency-enhancement method for secondary collimator modeling, presented in the context of a tool for MC-based dose second checks...
May 9, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29740971/target-position-reproducibility-in-left-breast-irradiation-with-deep-inspiration-breath-hold-using-multiple-optical-surface-control-points
#17
Aurora Fassi, Giovanni B Ivaldi, Paola Tabarelli de Fatis, Marco Liotta, Ilaria Meaglia, Patrizia Porcu, Lea Regolo, Marco Riboldi, Guido Baroni
The aim of this study was to investigate the use of 3D optical localization of multiple surface control points for deep inspiration breath-hold (DIBH) guidance in left-breast radiotherapy treatments. Ten left-breast cancer patients underwent whole-breast DIBH radiotherapy controlled by the Real-time Position Management (RPM) system. The reproducibility of the tumor bed (i.e., target) was assessed by the position of implanted clips, acquired through in-room kV imaging. Six to eight passive fiducials were positioned on the patients' thoraco-abdominal surface and localized intrafractionally by means of an infrared 3D optical tracking system...
May 8, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29729075/relationship-between-size-specific-dose-estimates-and-image-quality-in-computed-tomography-depending-on-patient-size
#18
Hiroki Kawashima, Katsuhiro Ichikawa, Shinsuke Hanaoka, Kosuke Matsubara, Tadanori Takata
This study investigates the relationship between contrast-to-noise ratio (CNR) and size-specific dose estimate (SSDE) in computed tomography (CT) depending on patient size. In addition, the relationship to the auto exposure control (AEC) techniques is examined. A tissue-equivalent material having human-liver energy dependence is developed and used to evaluate these relationships. Three exposure dose levels (constant CT dose index, constant SSDE, and with AEC) are tested using four different phantom sizes (diameter: 15, 20, 25 and 30 cm) in two different CT scanners (SOMATOM Definition Flash, Siemens, and LightSpeed VCT, GE)...
May 4, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29707904/investigation-of-ebt3-radiochromic-film-s-response-to-humidity
#19
Elsa Y León-Marroquín, José M Lárraga-Gutiérrez, J Alfredo Herrera-González, Miguel A Camacho-López, José E Villarreal Barajas, Olivia A García-Garduño
PURPOSE: The aim of this work is to investigate the effects of immersing EBT3 radiochromic film in water and to evaluate its contribution to the total uncertainty in dose determination. MATERIALS AND METHODS: We used 3 cm × 3 cm EBT3 radiochromic films irradiated in the range of 0-70 Gy to study the impact of water immersion on the change in net optical density. These films were placed in a water container for a period of 24 h. The net optical density was measured before (0 h) and after of the immersion in water (1, 3, 6, 12, 18, and 24 h)...
April 29, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29707895/gamma-irradiation-of-ocular-melanoma-and-lymphoma-cells-in-the-presence-of-gold-nanoparticles-in-vitro-study
#20
Mozhgan Rezaei Kanavi, Somayeh Asadi, Sahar Balagholi, Fatemeh Alikarami, Hassan Nosrati, Hamid Ahmadieh
The aim of this work was to determine whether conjugation of cultivated choroidal melanoma and Burkitt's lymphoma cells with gold nanoparticles (GNPs) is beneficial for these series of ocular cancer patients. GNPs are radiosensitizers and can sensitize tumors to radiotherapy.This application has been examined in several tumor types, but not in choroidal melanoma. This study shows the results of in vitro study on the choroidal melanoma and also Burkitt's lymphoma cells in the presence of GNPs during continuous gamma irradiation...
April 29, 2018: Journal of Applied Clinical Medical Physics
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