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Original Article

Korean Journal of Medical Physics 2012; 23(2): 91-98

Published online June 25, 2012

Copyright © Korean Society of Medical Physics.

Development of an Offline Based Internal Organ Motion Verification System during Treatment Using Sequential Cine EPID Images

연속촬영 전자조사 문 영상을 이용한 오프라인 기반 치료 중 내부 장기 움직임 확인 시스템의 개발

Sang Gyu Ju*, Chae-Seon Hong*, Woong Huh, Min Kyu Kim, Youngyih Han*, Eunhyuk Shin*, Jung Suk Shin*, Jing Sung Kim*, Hee Chul Park*, Sung-Hwan Ahn*, Do Hoon Lim*, Doo Ho Choi*

주상규*ㆍ홍채선*ㆍ허웅ㆍ김민규ㆍ한영이*ㆍ신은혁*ㆍ신정석*ㆍ김진성*ㆍ박희철*ㆍ안성환*ㆍ임도훈*ㆍ최두호*

*Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Department of Electronics Engineering, Myongji University, Yongin, Korea

*성균관대학교 의과대학 삼성서울병원 방사선종양학교실, 명지대학교 전자공학과

Abstract

Verification of internal organ motion during treatment and its feedback is essential to accurate dose delivery to the moving target. We developed an offline based internal organ motion verification system (IMVS) using cine EPID images and evaluated its accuracy and availability through phantom study. For verification of organ motion using live cine EPID images, a pattern matching algorithm using an internal surrogate, which is very distinguishable and represents organ motion in the treatment field, like diaphragm, was employed in the self-developed analysis software. For the system performance test, we developed a linear motion phantom, which consists of a human body shaped phantom with a fake tumor in the lung, linear motion cart, and control software. The phantom was operated with a motion of 2 cm at 4 sec per cycle and cine EPID images were obtained at a rate of 3.3 and 6.6 frames per sec (2 MU/frame) with 1,024×768 pixel counts in a linear accelerator (10 MVX). Organ motion of the target was tracked using self-developed analysis software. Results were compared with planned data of the motion phantom and data from the video image based tracking system (RPM, Varian, USA) using an external surrogate in order to evaluate its accuracy. For quantitative analysis, we analyzed correlation between two data sets in terms of average cycle (peak to peak), amplitude, and pattern (RMS, root mean square) of motion. Averages for the cycle of motion from IMVS and RPM system were 3.98±0.11 (IMVS 3.3 fps), 4.005±0.001 (IMVS 6.6 fps), and 3.95±0.02 (RPM), respectively, and showed good agreement on real value (4 sec/cycle). Average of the amplitude of motion tracked by our system showed 1.85±0.02 cm (3.3 fps) and 1.94±0.02 cm (6.6 fps) as showed a slightly different value, 0.15 (7.5% error) and 0.06 (3% error) cm, respectively, compared with the actual value (2 cm), due to time resolution for image acquisition. In analysis of pattern of motion, the value of the RMS from the cine EPID image in 3.3 fps (0.1044) grew slightly compared with data from 6.6 fps (0.0480). The organ motion verification system using sequential cine EPID images with an internal surrogate showed good representation of its motion within 3% error in a preliminary phantom study. The system can be implemented for clinical purposes, which include organ motion verification during treatment, compared with 4D treatment planning data, and its feedback for accurate dose delivery to the moving target.

KeywordsCine EPID, Organ motion tracking, Internal surrogate, 4D RT

Korean Society of Medical Physics

Vol.35 No.1
March 2024

pISSN 2508-4445
eISSN 2508-4453
Formerly ISSN 1226-5829

Frequency: Quarterly

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