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WE‐G‐213CD‐09: Quality Assurance of the Surrogate Signal‐Based Dynamic Tumor‐Tracking Irradiation with Vero4DRT (MHI‐TM2000)
Author(s) -
Mukumoto N,
Nakamura M,
Sawada A,
Suzuki Y,
Takahashi K,
Miyabe Y,
Kaneko S,
Mizowaki T,
Kokubo M,
Hiraoka M
Publication year - 2012
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4736210
Subject(s) - imaging phantom , quality assurance , tracking (education) , irradiation , nuclear medicine , materials science , physics , optics , computer science , biomedical engineering , medicine , psychology , pedagogy , external quality assessment , pathology , nuclear physics
Purpose: To perform the quality assurance for the dynamic tumor‐tracking (DTT) irradiation with Vero4DRT (MHI‐Tm 2 000). Methods: Vero4DRT swings its gimbaled 6‐MV C‐band x‐ray head along the pan and tilt direction to track a moving tumor. Surrogate signal‐based DTT system implemented in Vero4DRT was used. Before DTT irradiation, the correlation model (4D‐model) between motion of the IR markers on the abdominal wall and the tumor position was created with synchronously monitoring by the IR camera and orthogonal kV x‐ray imaging subsystem. During beam delivery, the 4D‐model predicted the future tumor position from the displacement of the IR markers in real‐time, and then contentiously transferred the corresponding tracking orientation to the gimbaled x‐ray head.Water‐equivalent phantoms were set on a 1D motor‐driven base with IR markers. A film placed at a depth of 10 cm in the phantom was irradiated under the following conditions: stationary state, and tracking and non‐ tracking state for sinusoidal patterns. In addition, the geometric accuracy was evaluated using a 3D moving phantom and Polaris Spectra for the previously‐acquired patient's respiratory pattern. Results: Compared to the stationary conditions, reductions in lateral distance between 95% doses of the dose profile were 1.2 mm for tracking and 29.6 mm for non‐tracking state for (amplitude [A], period [T]) = (20 mm, 2 s); and 0.2 mm and 29.4 mm for (A, T) = (20 mm, 4 s); and 0.0 mm and 11.2 mm for (A, T) = (10 mm, 2 s), respectively. In the geometric accuracy testing, 95th percentile of the tracking error was 0.5 mm in left‐right, 1.0 mm in superior‐inferior, and 0.5 mm in anterior‐posterior direction. Conclusions: We demonstrated that Vero4DRT substantially reduced the blurring effects on dose distribution with high tracking accuracy, and confirmed the safety of the DTT irradiation for a clinical application. This research was supported by the Japan Society for the Promotion of Science (JSPS) through its Funding Program for World‐Leading Innovation R&D on Science and Technology (FIRST Program), and sponsored in part by Mitsubishi Heavy Industries, Ltd.