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Detectability of MLC Stop Position Error During Treatment by Gantry-Mounted Transmission Detector

H Honda1,2*, M Tominaga3,M Sasaki4,Y Uto5,M Oita6, Y Hamamoto7,T Mochizuki8,T Kido9,Y Ishii10,R Yamamoto11,K Omoto12 (1) Department of Radiological Technology, Ehime University Hospital, Ehime, JP, (2) Graduate School of Advanced Technology and Science, Tokushima University, Jp, (3) Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, JP, (4) Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, JP, (5) Institute of Bioscience and Bioindustry, Tokushima University, Tokushima, Jp, (6) Okayama University Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama, JP, (7)Department of Radiological Technology, Ehime University Hospital, Ehime, JP,(8) Department of Radiological Technology, Ehime University Hospital, Ehime.JP,(9) Department of Radiology, Ehime University Graduate School of Medicine, Ehime, JP, (10) Department of Radiological Technology, Ehime University Hospital, Ehime, JP, (11) Department of Radiological Technology, Ehime University Hospital, Ehime, JP, (12) Department of Radiological Technology, Ehime University Hospital, Ehime, JP,

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: purpose of this research is to investigate the possibility of detecting errors during treatment using a gantry-mounted transmission detector.
Methods: compared the result of dose verification using the Delta4Discover® (D4D) of a gantry mounted transmission detector and the Delta4 Phantom + (D4P). In this study, ten prostates were evaluated. The simulation plan for detecting errors during treatment consists of the MLC of all control points is displaced from B side (X1 side) to Aside (X2 side) by 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0mm from the original plan. Dose deviation (DD), distance-to-agreement (DTA), and gamma index analysis (GA) were used to validate the dose distribution. The evaluation criteria were DD at 3%, DTA at 2mm, and GA at 3.0% / 2.0mm, and the threshold hold was evaluated at 10%. We performed a significant difference test using Welch's t-test as an evaluation of the significant difference between the original plan and the simulated plans.
Results: D4D When DD, DTA, and GA parameters were used, the detection of MLC error was 2.0 mm for DD and 1.5 mm for DTA and GA. Also, For D4P, MLC error detection was 2.0 mm for DD, 1.0 mm for DTA, and 1.5 mm for GA.
Conclusion: has almost the same detection power as D4P, and can be detected with an MLC position error of 1.5 mm or more by using DTA or GA. Based on our results, a transmission type detector seemed to be suitable for IVD.

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Keywords

In Vivo Dosimetry

Taxonomy

TH- External Beam- Photons: portal dosimetry, in-vivo dosimetry and dose reconstruction

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