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https://www.readbyqxmd.com/read/28325019/frameless-stereotactic-radiosurgery-fsrs-end-to-end-test-with-ebt-xd-gafchromic-film
#1
Yulin Song, Ceferino Obcemea, Boris Mueller, Borys Mychalczak
Frame-based stereotactic radiosurgery (SRS) has been widely used to treat functional disorders, vascular lesions, and primary benign and malignant tumors. Recently, SRS is being increasingly used to treat solitary brain metastases. However, due to its highly invasive nature, frame-based SRS is being gradually replaced by frameless SRS (fSRS). fSRS aims at improving patient comfort and achieving stable patient immobilization with non-invasive means and accurate target localization with image guidance technique...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28303745/grid-therapy-using-high-definition-multileaf-collimators-realizing-benefits-of-the-bystander-effect
#2
Valery Peng, Natalka Suchowerska, Linda Rogers, Elizabeth Claridge Mackonis, Samantha Oakes, David R McKenzie
BACKGROUND: In microbeam radiotherapy (MRT), parallel arrays of high-intensity synchrotron x-ray beams achieve normal tissue sparing without compromising tumor control. Grid-therapy using clinical linacs has spatial modulation on a larger scale and achieves promising results for palliative treatments of bulky tumors. The availability of high definition multileaf collimators (HDMLCs) with 2.5 mm leaves provides an opportunity for grid-therapy to more closely approach MRT. However, challenges to the wider implementation of grid-therapy remain because spatial modulation of the target volume runs counter to current radiotherapy practice and mechanisms for the beneficial effects of MRT are not fully understood...
March 17, 2017: Acta Oncologica
https://www.readbyqxmd.com/read/28300376/moving-gpu-opencl-based-monte-carlo-dose-calculation-toward-clinical-use-automatic-beam-commissioning-and-source-sampling-for-treatment-plan-dose-calculation
#3
Zhen Tian, Yongbao Li, Nima Hassan-Rezaeian, Steve B Jiang, Xun Jia
We have previously developed a GPU-based Monte Carlo (MC) dose engine on the OpenCL platform, named goMC, with a built-in analytical linear accelerator (linac) beam model. In this paper, we report our recent improvement on goMC to move it toward clinical use. First, we have adapted a previously developed automatic beam commissioning approach to our beam model. The commissioning was conducted through an optimization process, minimizing the discrepancies between calculated dose and measurement. We successfully commissioned six beam models built for Varian TrueBeam linac photon beams, including four beams of different energies (6 MV, 10 MV, 15 MV, and 18 MV) and two flattening-filter-free (FFF) beams of 6 MV and 10 MV...
March 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28298966/radiation-dose-enhancement-in-skin-therapy-with-nanoparticle-addition-a-monte-carlo-study-on-kilovoltage-photon-and-megavoltage-electron-beams
#4
Xiao J Zheng, James C L Chow
AIM: To investigated the dose enhancement due to the incorporation of nanoparticles in skin therapy using the kilovoltage (kV) photon and megavoltage (MV) electron beams. Monte Carlo simulations were used to predict the dose enhancement when different types and concentrations of nanoparticles were added to skin target layers of varying thickness. METHODS: Clinical kV photon beams (105 and 220 kVp) and MV electron beams (4 and 6 MeV), produced by a Gulmay D3225 orthovoltage unit and a Varian 21 EX linear accelerator, were simulated using the EGSnrc Monte Carlo code...
February 28, 2017: World Journal of Radiology
https://www.readbyqxmd.com/read/28297456/is-the-dose-distribution-distorted-in-imrt-and-rapidarc-treatment-when-patient-plans-are-swapped-across-beam-matched-machines
#5
Chockkalingam Krishnappan, Chandrasekaran Anu Radha, Vendhan Subramani, Madhan Kumar Gunasekaran
The purpose of this study is to evaluate the degree of dose distribution distortion in advanced treatments like IMRT and RapidArc when patient plans are swapped across dosimetrically equivalent so-called "beam-matched" machines. For this purpose the entire work is divided into two stages. At forefront stage all basic beam properties of 6 MV X-rays like PDD, profiles, output factors, TPR20/10 and MLC transmission of two beam-matched machines - Varian Clinac iX and Varian 600 C/D Unique - are compared and evaluated for differences...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297447/verification-measurements-of-an-emc-algorithm-using-a-2d-ion-chamber-array
#6
Mark D Wanklyn, Ghirmay Kidane, Liz Crees
The aim of this study was to assess the suitability of the Im'RT MatriXX 2D ion chamber array for performing verification measurements on the Varian Eclipse electron Monte Carlo (eMC) algorithm for a range of clinical energies (6, 12, and 20 MeV) on a Varian 2100iX linear accelerator. Firstly, the suitability of the MatriXX for measuring percentage depth doses (PDD) in water was assessed, including characterization of the inherent buildup found in the MatriXX. Secondly the suitability of the MatriXX for measuring dose distributions in homogeneous and heterogeneous phantoms was assessed using gamma analysis at 3%/3 mm...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297443/comparison-of-automatic-image-registration-uncertainty-for-three-igrt-systems-using-a-male-pelvis-phantom
#7
Jeffrey Barber, Jonathan R Sykes, Lois Holloway, David I Thwaites
A series of phantom images using the CIRS Virtual Human Male Pelvis was acquired across available dose ranges for three image-guided radiotherapy (IGRT) imaging systems: Elekta XVI CBCT, Varian TrueBeam CBCT, and TomoTherapy MV CT. Each image was registered to a fan-beam CT within the XVI software 100 times with random initial offsets. The residual registration error was analyzed to assess the role of imaging hardware and reconstruction in the uncertainty of the IGRT process. Residual translation errors were similar for all systems and <0...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297428/a-dosimetric-comparison-of-copper-and-cerrobend-electron-inserts
#8
Benjamin D Rusk, Robert L Carver, John P Gibbons, Kenneth R Hogstrom
The purpose of this work was to evaluate differences in dose resulting from the use of copper aperture inserts compared to lead-alloy (Cerrobend) aperture inserts for electron beam therapy. Specifically, this study examines if copper aperture inserts can be used clinically with the same commissioning data measured using lead-alloy aperture inserts. The copper inserts were acquired from .decimal, Inc. and matching lead-alloy, Cerrobend inserts were constructed in-house for 32 combinations of nine square insert field sizes (2×2 to 20×20 cm2) and five applicator sizes (6×6 to 25×25 cm2)...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297427/a-comparative-study-of-identical-vmat-plans-with-and-without-jaw-tracking-technique
#9
Hao Wu, Fan Jiang, Haizhen Yue, Qiaoqiao Hu, Jian Zhang, Zhuolun Liu, Jian Gong, Sha Li, Jianhao Geng, Yibao Zhang
The unwanted radiation transmission through the multileaf collimators could be reduced by the jaw tracking technique which is commercially available on Varian TrueBeam accelerators. On the basis of identical plans, this study aims to investigate the dosimetric impact of jaw tracking on the volumetric-modulated arc therapy (VMAT) plans. Using Eclipse treatment planning system (TPS), 40 jaw-tracking VMAT plans with various tumor volumes and shapes were optimized. Fixed jaw plans were created by editing the jaw coordinates of the jaw-tracking plans while other parameters were identical...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297418/characterization-of-a-2-5-mv-inline-portal-imaging-beam
#10
James L Gräfe, Jennifer Owen, J Eduardo Villarreal-Barajas, Rao F H Khan
A new megavoltage (MV) energy was recently introduced on Varian TrueBeam linear accelerators for imaging applications. This work describes the experimental characterization of a 2.5 MV inline portal imaging beam for commissioning, routine clinical use, and quality assurance purposes. The beam quality of the 2.5 MV beam was determined by measuring a percent depth dose, PDD, in water phantom for 10×10 cm2 field at source-to-surface distance 100 cm with a CC13 ion chamber, plane parallel Markus chamber, and GafChromic EBT3 film...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297351/output-factor-comparison-of-monte-carlo-and-measurement-for-varian-truebeam-6-mv-and-10-mv-flattening-filter-free-stereotactic-radiosurgery-system
#11
Jason Y Cheng, Holly Ning, Barbara C Arora, Ying Zhuge, Robert W Miller
The dose measurements of the small field sizes, such as conical collimators used in stereotactic radiosurgery (SRS), are a significant challenge due to many factors including source occlusion, detector size limitation, and lack of lateral electronic equilibrium. One useful tool in dealing with the small field effect is Monte Carlo (MC) simulation. In this study, we report a comparison of Monte Carlo simulations and measurements of output factors for the Varian SRS system with conical collimators for energies of 6 MV flattening filter-free (6 MV) and 10 MV flattening filter-free (10 MV) on the TrueBeam accelerator...
May 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297342/in-house-quality-check-of-external-beam-plans-using-3d-treatment-planning-systems-a-dvh-comparison
#12
Ayyalasomayajula Anil Kumar, Roopa Rani Akula, Komanduri Ayyangar, Reddy P Krishna, Srinivas Vuppu, P V Lakshmi Narayana, A Durga Prasada Rao
This paper presents a new approach towards the quality assurance of external beam plans using in-house-developed DICOM import and export software in a clinical setup. The new approach is different from what is currently used in most clinics, viz., only MU and point dose are verified. The DICOM-RT software generates ASCII files to import/export structure sets, treatment beam data, and dose-volume histograms (DVH) from one treatment planning system (TPS) to the other. An efficient and reliable 3D planning system, ROPS, was used for verifying the accuracy of treatment plans and treatment plan parameters...
May 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297327/small-field-detector-correction-factors-effects-of-the-flattening-filter-for-elekta-and-varian-linear-accelerators
#13
Madelaine K Tyler, Paul Z Y Liu, Christopher Lee, David R McKenzie, Natalka Suchowerska
Flattening filter-free (FFF) beams are becoming the preferred beam type for stereotactic radiosurgery (SRS) and stereotactic ablative radiation therapy (SABR), as they enable an increase in dose rate and a decrease in treatment time. This work assesses the effects of the flattening filter on small field output factors for 6 MV beams generated by both Elekta and Varian linear accelerators, and determines differences between detector response in flattened (FF) and FFF beams. Relative output factors were measured with a range of detectors (diodes, ionization chambers, radiochromic film, and microDiamond) and referenced to the relative output factors measured with an air core fiber optic dosimeter (FOD), a scintillation dosimeter developed at Chris O'Brien Lifehouse, Sydney...
May 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297306/epid-based-dosimetry-to-verify-imrt-planar-dose-distribution-for-the-as1200-epid-and-fff-beams
#14
Narges Miri, Peter Keller, Benjamin J Zwan, Peter Greer
We proposed to perform a basic dosimetry commissioning on a new imager system, the Varian aS1200 electronic portal imaging device (EPID) and TrueBeam 2.0 linear accelerator for flattened (FF) and flattening filter-free (FFF) beams, then to develop an image-based quality assurance (QA) model for verification of the system delivery accuracy for intensity-modulated radiation therapy (IMRT) treatments. For dosimetry testing, linearity of dose response with MU, imager lag, and effectiveness of backscatter shielding were investigated...
November 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297295/a-comparison-of-methods-for-monitoring-photon-beam-energy-constancy
#15
Song Gao, Peter A Balter, Mark Rose, William E Simon
In extension of a previous study, we compared several photon beam energy metrics to determine which was the most sensitive to energy change; in addition to those, we accounted for both the sensitivity of each metric and the uncertainty in determining that metric for both traditional flattening filter (FF) beams (4, 6, 8, and 10 MV) and for flattening filter-free (FFF) beams (6 and 10 MV) on a Varian TrueBeam. We examined changes in these energy metrics when photon energies were changed to ±5% and ±10% from their nominal energies: 1) an attenuation-based metric (the percent depth dose at 10 cm depth, PDD(10)) and, 2) profile-based metrics, including flatness (Flat) and off-axis ratios (OARs) measured on the orthogonal axes or on the diagonals (diagonal normalized flatness, FDN)...
November 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28296328/out-of-field-doses-and-neutron-dose-equivalents-for-electron-beams-from-modern-varian-and-elekta-linear-accelerators
#16
Carlos E Cardenas, Paige L Nitsch, Rajat J Kudchadker, Rebecca M Howell, Stephen F Kry
Out-of-field doses from radiotherapy can cause harmful side effects or eventually lead to secondary cancers. Scattered doses outside the applicator field, neutron source strength values, and neutron dose equivalents have not been broadly investigated for high-energy electron beams. To better understand the extent of these exposures, we measured out-of-field dose characteristics of electron applicators for high-energy electron beams on two Varian 21iXs, a Varian TrueBeam, and an Elekta Versa HD operating at various energy levels...
July 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28296322/predicting-deliverability-of-volumetric-modulated-arc-therapy-vmat-plans-using-aperture-complexity-analysis
#17
Kelly C Younge, Don Roberts, Lindsay A Janes, Carlos Anderson, Jean M Moran, Martha M Matuszak
The purpose of this study was to evaluate the ability of an aperture complexity metric for volumetric-modulated arc therapy (VMAT) plans to predict plan delivery accuracy. We developed a complexity analysis tool as a plug-in script to Varian's Eclipse treatment planning system. This script reports the modulation of plans, arcs, and individual control points for VMAT plans using a previously developed complexity metric. The calculated complexities are compared to that of 649 VMAT plans previously treated at our institution from 2013 to mid-2015...
July 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28296309/characterization-and-evaluation-of-2-5-mv-electronic-portal-imaging-for-accurate-localization-of-intra-and-extracranial-stereotactic-radiosurgery
#18
Kwang Hyun Song, Karen Chin Snyder, Jinkoo Kim, Haisen Li, Wen Ning, Robert Rusnac, Paul Jackson, James Gordon, Salim M Siddiqui, Indrin J Chetty
2.5 MV electronic portal imaging, available on Varian TrueBeam machines, was characterized using various phantoms in this study. Its low-contrast detectability, spatial resolution, and contrast-to-noise ratio (CNR) were compared with those of conventional 6 MV and kV planar imaging. Scatter effect in large patient body was simulated by adding solid water slabs along the beam path. The 2.5 MV imaging mode was also evaluated using clinically acquired images from 24 patients for the sites of brain, head and neck, lung, and abdomen...
July 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28296308/clinical-implications-of-the-overshoot-effect-for-treatment-plan-delivery-and-patient-specific-quality-assurance-for-step-and-shoot-imrt
#19
John A Baines, Sylwia J Zawlodzka, Matthew L Parfitt, Brigid E Hickey, Andrew P Pullar
In this work, overshoot and undershoot effects associated with step-and-shoot IMRT (SSIMRT) delivery on a Varian Clinac 21iX are investigated, and their impact on patient-specific QA point dose measurements and treatment plan delivery are evaluated. Pinnacle(3) SSIMRT plans consisting of 5, 10, and 15 identical 5×5 cm2 MLC defined segments and MU/segment values of 5 MU, 10 MU, and 20 MU were utilized and delivered at 600/300 MU/min. Independent of the number of segments the overshoot and undershoot at 600 MU/min were approximately ±10%,±5%, and ±2...
July 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28296305/on-flattening-filter-free-portal-dosimetry
#20
Eduardo Pardo, Juan Castro Novais, María Yolanda Molina López, Sheila Ruiz Maqueda
Varian introduced (in 2010) the option of removing the flattening filter (FF) in their C-Arm linacs for intensity-modulated treatments. This mode, called flattening filter-free (FFF), offers the advantage of a greater dose rate. Varian's "Portal Dosimetry" is an electronic portal imager device (EPID)-based tool for IMRT verification. This tool lacks the capability of verifying flattening filter-free (FFF) modes due to saturation and lack of an image prediction algorithm. (Note: the latest versions of this software and EPID correct these issues...
July 2016: Journal of Applied Clinical Medical Physics
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