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https://www.readbyqxmd.com/read/28102944/a-simple-and-robust-trajectory-based-stereotactic-radiosurgery-treatment
#1
Byron Wilson, Karl Otto, Ermias Gete
INTRODUCTION: We present a Trajectory-based Volumetric Modulated Arc Therapy (TVMAT) technique for Stereotactic Radiosurgery (SRS) that takes advantage of a modern linacs ability to modulate dose rate and move the couch dynamically. In addition, we investigate the quality of the developed TVMAT method and the dosimetric accuracy of the technique. METHODS: The main feature of the TVMAT technique is a standard beam trajectory formed by dynamic motion of the treatment couch and the linac gantry...
January 2017: Medical Physics
https://www.readbyqxmd.com/read/28079525/a-model-based-3d-patient-specific-pre-treatment-qa-method-for-vmat-using-the-epid
#2
Peter M McCowan, Ganiyu Asuni, Timothy van Beek, Eric Van Uytven, Kaden Kujanpaa, Boyd McCurdy
This study reports the development and validation of the first model-based, 3D patient dose reconstruction method for pre-treatment quality assurance using EPID images. The method is also investigated for sensitivity to potential MLC delivery errors. Each cine-mode EPID image acquired during plan delivery was processed using a previously developed back-projection dose reconstruction model providing a 3D dose estimate on the CT simulation data. Validation was carried out using 24 SBRT-VMAT patient plans by comparing: 1) ion chamber point dose measurements in a solid water phantom, 2) the treatment planning system (TPS) predicted 3D dose to the EPID reconstructed 3D dose in a solid water phantom, and 3) the TPS predicted 3D dose to the EPID and our forward predicted reconstructed 3D dose in the patient (CT data)...
January 12, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28079260/an-experimentally-validated-couch-and-mlc-tracking-simulator-used-to-investigate-hybrid-couch-mlc-tracking
#3
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/28066146/high-fat-diet-confers-vascular-hyper-contractility-against-angiotensin-ii-through-upregulation-of-mlck-and-cpi-17
#4
Jee In Kim
Obesity is a critical risk factor for the hypertension. Although angiotensin II (Ang II) in obese individuals is known to be upregulated in obesity-induced hypertension, direct evidence that explains the underlying mechanism for increased vascular tone and consequent increase in blood pressure (BP) is largely unknown. The purpose of this study is to investigate the novel mechanism underlying Ang II-induced hyper-contractility and hypertension in obese rats. Eight-week old male Sprague-Dawley rats were fed with 60% fat diet or normal diet for 4 months...
January 2017: Korean Journal of Physiology & Pharmacology
https://www.readbyqxmd.com/read/28065699/evaluation-of-mlc-performance-in-vmat-and-dynamic-imrt-by-log-file-analysis
#5
José Olasolo-Alonso, Alejandro Vázquez-Galiñanes, Santiago Pellejero-Pellejero, José Fernando Pérez-Azorín
PURPOSE: This multi-institution study assessed the positioning accuracy of multileaf collimators (MLC) by analyzing log files. It determined the main machine parameters that affect MLC positioning errors for pre-TrueBeam (Clinac) and TrueBeam linacs. METHODS: Around 30,000 dIMRT and VMAT log files belonging to 6 linacs from 4 different centers were analyzed. An in-house software was used to calculate 95th percentile and RMS error values and their correlation with certain parameters such as maximum leaf speed, mean leaf speed and gantry angle...
January 5, 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28051926/the-process-of-change-in-complicated-grief-group-therapy-for-bereaved-dementia-caregivers-an-evaluation-using-the-meaning-of-loss-codebook
#6
Katherine P Supiano, Lara Burns Haynes, Vicki Pond
Caring for a person with dementia is challenging and has adverse health and mental health effects that, for 9-25% of caregivers persist into bereavement in the form of complicated grief (CG). For those bereaved dementia caregivers unable to satisfactorily process grief, specialized Complicated Grief Group Therapy (CGGT) can restore a healthy grief process. We investigated the progression of therapeutic change in CGGT participants (N = 16 in three treatment groups), using an adapted version of Meaning of Loss Codebook (MLC; Gillies et al...
January 4, 2017: Journal of Gerontological Social Work
https://www.readbyqxmd.com/read/28048909/su-f-p-36-automation-of-linear-accelerator-star-shot-measurement-with-advanced-xml-scripting-and-electronic-portal-imaging-device
#7
N Nguyen, N Knutson, M Schmidt, M Price
PURPOSE: To verify a method used to automatically acquire jaw, MLC, collimator and couch star shots for a Varian TrueBeam linear accelerator utilizing Developer Mode and an Electronic Portal Imaging Device (EPID). METHODS: An XML script was written to automate motion of the jaws, MLC, collimator and couch in TrueBeam Developer Mode (TBDM) to acquire star shot measurements. The XML script also dictates MV imaging parameters to facilitate automatic acquisition and recording of integrated EPID images...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048852/su-f-t-645-to-test-spatial-anddosimetric-accuracy-of-small-cranial-target-irradiation-based-on-1-5-t-mriscans-using-static-arcs-with-mlcdefined-fields
#8
I Brezovich, X Wu, R Popple, S Shen, R Cardan, M Bolding, J Fiveash, J Kraus, S Spencer
PURPOSE: To test spatial and dosimetric accuracy of small cranial target irradiation based on 1.5 T MRI scans using static arcs with MLC-defined fields METHODS: A plastic (PMMA) phantom simulating a small brain lesion was mounted on a GammaKnife headframe equipped with MRI localizer. The lesion was a 3 mm long, 3.175 mm diameter cylindrical cavity filled with MRI contrast. Radiochromic film passing through the cavity was marked with pin pricks at the cavity center. The cavity was contoured on an MRI image and fused with CT to simulate treatment of a lesion not visible on CT...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048850/su-g-brc-14-multi-lesion-multi-rx-brain-radiosurgery-with-novel-single-isocenter-technique
#9
N Honig, S Alani, A Schlocker, N Shtraus, A Kanner
PURPOSE: There is a strong trend to treat multiple brain metastases with radiosurgery rather than whole brain irradiation. This feasibility study investigates a novel planning technique for radio-surgical treatment of multiple brain lesions with differing dose prescriptions, a single isocenter, and dynamic conformal arcs. The novel technique will be compared to the well-established single-isocenter volumetric modulated arc therapy (VMAT) technique commonly used for treating brain lesions...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048836/su-f-j-30-application-of-intra-fractional-imaging-for-pretreatment-cbct-of-breath-hold-lung-sbrt
#10
D Cao, M Jermoumi, V Mehta, D Shepard
PURPOSE: Clinical implementation of gated lung SBRT requires tools to verify the accuracy of the target positioning on a daily basis. This is a particular challenge on Elekta linacs where the XVI imaging system does not interface directly to any commercial gating solution. In this study, we used the Elekta's intra-fractional imaging functionality to perform the pretreatment CBCT verifications and evaluated both the image quality and gating accuracy. METHODS: To use intrafraction imaging tools for pretreatment verifications, we planned a 360-degree arc with 1mmx5mm MLC opening...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048811/su-g-tep4-15-the-roucoulette-a-set-of-quality-control-tests-for-dynamic-trajectory-4pi-treatment-delivery-techniques
#11
T Teke
PURPOSE: To present and validate a set of quality control tests for trajectory treatment delivery using synchronized dynamic couch (translation and rotation), MLC and collimator motion. METHODS: The quality control tests are based on the Picket fence test, which consist of 5 narrow band 2mm width spaced at 2.5cm intervals, and adds progressively synchronized dynamic motions. The tests were exposed on GafChromic EBT3 films. The first test is a regular (no motion and MLC static while beam is on) Picket Fence test used as baseline...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048770/su-g-jep1-05-clinical-impact-of-mlc-tracking-for-lung-sabr
#12
V Caillet, E Colvill, K Szymura, M Stevens, J Booth, P Keall
PURPOSE: The objective of this study was to investigate the dosimetric benefits of multi-leaf collimator (MLC) tracking for lung SABR treatments in end-to-end clinically realistic planning and delivery scenarios. METHODS: The clinical benefits of MLC tracking were assessed using previously delivered treatment plans and physical experiments. The 10 most recent single lesion lung SABR patients were re-planned following a 4D-GTV-based real-time adaptive protocol (PTV defined as the end-of-exhalation GTV plus 5...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048769/mo-fg-202-04-gantry-resolved-linac-qa-for-vmat-a-comprehensive-and-efficient-system-using-an-electronic-portal-imaging-device
#13
B J Zwan, M Barnes, J Hindmarsh, E Seymour, D J O'Connor, P J Keall, P B Greer
PURPOSE: To automate gantry-resolved linear accelerator (linac) quality assurance (QA) for volumetric modulated arc therapy (VMAT) using an electronic portal imaging device (EPID). METHODS: A QA system for VMAT was developed that uses an EPID, frame-grabber assembly and in-house developed image processing software. The system relies solely on the analysis of EPID image frames acquired without the presence of a phantom. Images were acquired at 8.41 frames per second using a frame grabber and ancillary acquisition computer...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048766/su-g-bra-16-target-dose-comparison-for-dynamic-mlc-tracking-and-mid-ventilation-planning-in-lung-radiotherapy-subject-to-intrafractional-baseline-drifts
#14
M J Menten, M F Fast, S Nill, U Oelfke
PURPOSE: Lung tumor motion during radiotherapy can be accounted for by expanded treatment margins, for example using a mid-ventilation planning approach, or by localizing the tumor in real-time and adapting the treatment beam with multileaf collimator (MLC) tracking. This study evaluates the effect of intrafractional changes in the average tumor position (baseline drifts) on these two treatment techniques. METHODS: Lung stereotactic treatment plans (9-beam IMRT, 54Gy/3 fractions, mean treatment time: 9...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048747/su-f-t-230-a-simple-method-to-assess-accuracy-of-dynamic-wave-arc-irradiation-using-an-electronic-portal-imaging-device-and-log-files
#15
H Hirashima, Y Miyabe, K Yokota, M Nakamura, N Mukumoto, T Mizowaki, M Hiraoka
PURPOSE: The Dynamic Wave Arc (DWA) technique, where the multi-leaf collimator (MLC) and gantry/ring move simultaneously in a predefined non-coplanar trajectory, has been developed on the Vero4DRT. The aim of this study is to develop a simple method for quality assurance of DWA delivery using an electronic portal imaging device (EPID) measurements and log files analysis. METHODS: The Vero4DRT has an EPID on the beam axis, the resolution of which is 0.18 mm/pixel at the isocenter plane...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048745/tu-d-brc-01-novel-applications-for-current-epid-technology
#16
J Rottmann
There has been increased deployment of gantry-mounted linacs with onboard kilovoltage x-ray imagers. Despite this trend, most clinics still employ beam's-eye-view (BEV) imaging using flat panel electronic portal imaging devices (EPIDs) as a highly useful means of verifying geometric localization pre- and post-delivery. In recent years, there has been increased interest in the use of EPIDs for a variety of clinical and investigational applications ranging from megavoltage cone-beam CT, in vivo dosimetry, patient-specific QA to real-time target localization for dynamic MLC-based tumor tracking...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048717/mo-fg-202-09-virtual-imrt-qa-using-machine-learning-a-multi-institutional-validation
#17
G Valdes, M Chan, R Scheuermann, J Deasy, T Solberg
PURPOSE: To validate a machine learning approach to Virtual IMRT QA for accurately predicting gamma passing rates using different QA devices at different institutions. METHODS: A Virtual IMRT QA was constructed using a machine learning algorithm based on 416 IMRT plans, in which QA measurements were performed using diode-array detectors and a 3%local/3mm with 10% threshold. An independent set of 139 IMRT measurements from a different institution, with QA data based on portal dosimetry using the same gamma index and 10% threshold, was used to further test the algorithm...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048691/tu-ab-brc-11-moving-a-gpu-opencl-based-monte-carlo-mc-dose-engine-towards-routine-clinical-use-automatic-beam-commissioning-and-efficient-source-sampling
#18
Z Tian, Y Li, M Folkerts, S Jiang, X Jia
PURPOSE: We have previously developed a GPU-OpenCL-based MC dose engine named goMC with built-in analytical linac beam model. To move goMC towards routine clinical use, we have developed an automatic beam-commissioning method, and an efficient source sampling strategy to facilitate dose calculations for real treatment plans. METHODS: Our commissioning method is to automatically adjust the relative weights among the sub-sources, through an optimization process minimizing the discrepancies between calculated dose and measurements...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048673/su-f-t-288-impact-of-trajectory-log-files-for-clarkson-based-independent-dose-verification-of-imrt-and-vmat
#19
R Takahashi, T Kamima, H Tachibana
PURPOSE: To investigate the effect of the trajectory files from linear accelerator for Clarkson-based independent dose verification in IMRT and VMAT plans. METHODS: A CT-based independent dose verification software (Simple MU Analysis: SMU, Triangle Products, Japan) with a Clarksonbased algorithm was modified to calculate dose using the trajectory log files. Eclipse with the three techniques of step and shoot (SS), sliding window (SW) and Rapid Arc (RA) was used as treatment planning system (TPS)...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048659/tu-fg-201-03-automatic-pre-delivery-verification-using-statistical-analysis-of-consistencies-in-treatment-plan-parameters-by-the-treatment-site-and-modality
#20
S Liu, Y Wu, X Chang, H Li, D Yang
PURPOSE: A novel computer software system, namely APDV (Automatic Pre-Delivery Verification), has been developed for verifying patient treatment plan parameters right prior to treatment deliveries in order to automatically detect and prevent catastrophic errors. METHODS: APDV is designed to continuously monitor new DICOM plan files on the TMS computer at the treatment console. When new plans to be delivered are detected, APDV checks the consistencies of plan parameters and high-level plan statistics using underlying rules and statistical properties based on given treatment site, technique and modality...
June 2016: Medical Physics
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