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Title: SU-G-BRB-09: Kompeito-Shot: Development of a Novel Verification System for 3D Beam Alignment Including the Sag of Gantry Head

Abstract

Purpose: High accuracy of beam axis is required for high-precision radiation therapy. It is impossible to quantitatively and directly evaluate the sagging effect of the gantry head using current methods (star-shot and Winston-Lutz tests) when the gantry head sags under the weight of MLC and X-Y jaws. We introduce a novel method “Kompeito-shot (3D star-shot)” for the verification of 3D beam alignment (3D isocentricity). This method enables direct measurement of the sagging effect. We developed the system and examined the concept of this system. Methods: The system composed of a plastic scintillator (PS), a truncated cone-shaped mirror, a plane mirror and a CCD camera. Two types of PS were compared. One consisted of a column PS (Co system), the other consisted of a column PS inserted into a barrel PS with shading film in between (Co-Ba system). The system was irradiated with a 6-MV photon beam and the scintillation light was measured using the CCD camera through the mirror system. The gantry angle was set from 270 to 300 degrees to mimic the sagging of the gantry head for evaluating the accuracy of the system. The distance between a center of PS and entrance / exit points were calculated tomore » analyze the gantry angle. And, the calculated gantry angle and the irradiated gantry angle were compared. Results: We compared the measured image of Co system and that of Co-Ba system. Entrance and exit areas were visualized clearly. The histogram showing the difference between the calculated gantry angle and the irradiated gantry angle was fitted with a Gaussian function. Mean and standard deviation of Co-Ba system were smaller than that of Co system by one order of magnitude. Conclusion: We developed the Kompeito-shot system and evaluated the accuracy of the system. The basic concept works for the verification of 3D isocentricity.« less

Authors:
;  [1]; ; ;  [1];  [2];  [3];  [4];  [5];  [1];  [2];  [1];  [2];  [2]
  1. Hiroshima University, Hiroshima (Japan)
  2. (Japan)
  3. Hiroshima University Hospital, Hiroshima (Japan)
  4. Rikkyo University, Tokyo (Japan)
  5. The University of Tokyo, Tokyo (Japan)
Publication Date:
OSTI Identifier:
22649281
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; A CENTERS; ACCURACY; ALIGNMENT; CHARGE-COUPLED DEVICES; COBALT; HEAD; IRRADIATION; PHOTON BEAMS; VERIFICATION; VISIBLE RADIATION

Citation Formats

Tsuneda, M, Nishio, T, Saito, A, Kawahara, D, Ochi, Y, Hiroshima University Hospital, Hiroshima, Hioki, K, Matsushita, K, Tanaka, S, Ozawa, S, Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima, Nagata, Y, Hiroshima University Hospital, Hiroshima, and Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima. SU-G-BRB-09: Kompeito-Shot: Development of a Novel Verification System for 3D Beam Alignment Including the Sag of Gantry Head. United States: N. p., 2016. Web. doi:10.1118/1.4956916.
Tsuneda, M, Nishio, T, Saito, A, Kawahara, D, Ochi, Y, Hiroshima University Hospital, Hiroshima, Hioki, K, Matsushita, K, Tanaka, S, Ozawa, S, Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima, Nagata, Y, Hiroshima University Hospital, Hiroshima, & Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima. SU-G-BRB-09: Kompeito-Shot: Development of a Novel Verification System for 3D Beam Alignment Including the Sag of Gantry Head. United States. doi:10.1118/1.4956916.
Tsuneda, M, Nishio, T, Saito, A, Kawahara, D, Ochi, Y, Hiroshima University Hospital, Hiroshima, Hioki, K, Matsushita, K, Tanaka, S, Ozawa, S, Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima, Nagata, Y, Hiroshima University Hospital, Hiroshima, and Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima. Wed . "SU-G-BRB-09: Kompeito-Shot: Development of a Novel Verification System for 3D Beam Alignment Including the Sag of Gantry Head". United States. doi:10.1118/1.4956916.
@article{osti_22649281,
title = {SU-G-BRB-09: Kompeito-Shot: Development of a Novel Verification System for 3D Beam Alignment Including the Sag of Gantry Head},
author = {Tsuneda, M and Nishio, T and Saito, A and Kawahara, D and Ochi, Y and Hiroshima University Hospital, Hiroshima and Hioki, K and Matsushita, K and Tanaka, S and Ozawa, S and Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima and Nagata, Y and Hiroshima University Hospital, Hiroshima and Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima},
abstractNote = {Purpose: High accuracy of beam axis is required for high-precision radiation therapy. It is impossible to quantitatively and directly evaluate the sagging effect of the gantry head using current methods (star-shot and Winston-Lutz tests) when the gantry head sags under the weight of MLC and X-Y jaws. We introduce a novel method “Kompeito-shot (3D star-shot)” for the verification of 3D beam alignment (3D isocentricity). This method enables direct measurement of the sagging effect. We developed the system and examined the concept of this system. Methods: The system composed of a plastic scintillator (PS), a truncated cone-shaped mirror, a plane mirror and a CCD camera. Two types of PS were compared. One consisted of a column PS (Co system), the other consisted of a column PS inserted into a barrel PS with shading film in between (Co-Ba system). The system was irradiated with a 6-MV photon beam and the scintillation light was measured using the CCD camera through the mirror system. The gantry angle was set from 270 to 300 degrees to mimic the sagging of the gantry head for evaluating the accuracy of the system. The distance between a center of PS and entrance / exit points were calculated to analyze the gantry angle. And, the calculated gantry angle and the irradiated gantry angle were compared. Results: We compared the measured image of Co system and that of Co-Ba system. Entrance and exit areas were visualized clearly. The histogram showing the difference between the calculated gantry angle and the irradiated gantry angle was fitted with a Gaussian function. Mean and standard deviation of Co-Ba system were smaller than that of Co system by one order of magnitude. Conclusion: We developed the Kompeito-shot system and evaluated the accuracy of the system. The basic concept works for the verification of 3D isocentricity.},
doi = {10.1118/1.4956916},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}
  • Purpose: To investigate the sensitivity of an EPID-based 3D dose verification system to detect delivery errors in VMAT treatments. Methods: For this study 41 EPID-reconstructed 3D in vivo dose distributions of 15 different VMAT plans (H&N, lung, prostate and rectum) were selected. To simulate the effect of delivery errors, their TPS plans were modified by: 1) scaling of the monitor units by ±3% and ±6% and 2) systematic shifting of leaf bank positions by ±1mm, ±2mm and ±5mm. The 3D in vivo dose distributions where then compared to the unmodified and modified treatment plans. To determine the detectability of themore » various delivery errors, we made use of a receiver operator characteristic (ROC) methodology. True positive and false positive rates were calculated as a function of the γ-parameters γmean, γ1% (near-maximum γ) and the PTV dose parameter ΔD{sub 50} (i.e. D{sub 50}(EPID)-D{sub 50}(TPS)). The ROC curve is constructed by plotting the true positive rate vs. the false positive rate. The area under the ROC curve (AUC) then serves as a measure of the performance of the EPID dosimetry system in detecting a particular error; an ideal system has AUC=1. Results: The AUC ranges for the machine output errors and systematic leaf position errors were [0.64 – 0.93] and [0.48 – 0.92] respectively using γmean, [0.57 – 0.79] and [0.46 – 0.85] using γ1% and [0.61 – 0.77] and [ 0.48 – 0.62] using ΔD{sub 50}. Conclusion: For the verification of VMAT deliveries, the parameter γmean is the best discriminator for the detection of systematic leaf position errors and monitor unit scaling errors. Compared to γmean and γ1%, the parameter ΔD{sub 50} performs worse as a discriminator in all cases.« less
  • Purpose: The novel 3 dimensional (3D)-printed spine quality assurance (QA) phantoms generated by two different 3D-printing technologies, digital light processing (DLP) and Polyjet, were developed and evaluated for spine stereotactic body radiation treatment (SBRT). Methods: The developed 3D-printed spine QA phantom consisted of an acrylic body and a 3D-printed spine phantom. DLP and Polyjet 3D printers using the high-density acrylic polymer were employed to produce spine-shaped phantoms based on CT images. To verify dosimetric effects, the novel phantom was made it enable to insert films between each slabs of acrylic body phantom. Also, for measuring internal dose of spine, 3D-printedmore » spine phantom was designed as divided laterally exactly in half. Image fusion was performed to evaluate the reproducibility of our phantom, and the Hounsfield unit (HU) was measured based on each CT image. Intensity-modulated radiotherapy plans to deliver a fraction of a 16 Gy dose to a planning target volume (PTV) based on the two 3D-printing techniques were compared for target coverage and normal organ-sparing. Results: Image fusion demonstrated good reproducibility of the fabricated spine QA phantom. The HU values of the DLP- and Polyjet-printed spine vertebrae differed by 54.3 on average. The PTV Dmax dose for the DLP-generated phantom was about 1.488 Gy higher than for the Polyjet-generated phantom. The organs at risk received a lower dose when the DLP technique was used than when the Polyjet technique was used. Conclusion: This study confirmed that a novel 3D-printed phantom mimicking a high-density organ can be created based on CT images, and that a developed 3D-printed spine phantom could be utilized in patient-specific QA for SBRT. Despite using the same main material, DLP and Polyjet yielded different HU values. Therefore, the printing technique and materials must be carefully chosen in order to accurately produce a patient-specific QA phantom.« less
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