| Summary: | 碩士 === 高雄醫學大學 === 醫學影像暨放射科學系碩士在職專班 === 105 === Objectives：This study aimed to investigate the setup error between three immobilization devices of lower abdominal cancer patients through image registration and analysis by cone beam computed tomography (CBCT), provide suitable option to physicians and radiologists for improving reproducibility.
Material and methods：The research participants comprised 43 lower abdominal cancer patients who received radiation therapy during the period between 2014 and 2016. The three-axis translation error and the rotation error were obtained by comparing the CBCT(Elekta AXESSE®) images before treatment with the thermoplastic cast(Klarity breast & pelvis baseplate, Klarity pelvic mask 53.5╳48.7 cm), the vacuum bag(ELEATA BlueBAG™ 85╳100 cm), and the feetfix(CIVCO Feetfix™ 2) as the daily immobilization device. The three kinds of immobilization devices were compared with evaluate the position reproducibility in each axial direction.
Results：The translation error of the thermoplastic cast of was 2.1±1.7 mm, 4.6±3.3 mm, 1.6±1.6 mm along the Tx, Ty, Tz, and the TVE was 5.9±3.1, and the rotation error was 0.9°±0.9°, 0.7°±0.5°, 1.1°±0.7° along the Rx, Ry, Rz. The translation error of the vacuum bag was 2.7±2.3 mm,1.8±1.3 mm,3.4±2.8 mm along the Tx, Ty, Tz, and the TVE was 5.3±2.8, and the rotation error was 1°±1.1°, 0.7°±0.6°, 1.2°±0.8° along the Rx, Ry, Rz. The translation error of the feetfix was 2.7±2.4 mm,1.6±1.4 mm,3.7±3.3 mm along the Tx, Ty, Tz, and the TVE was 5.5±3.4, and the rotation error was 1.1°±1.2°,0.7°±0.5°,1°±1° along the Rx, Ry, Rz.
Conclusion：In the case of the reproducibility of the lower abdominal cancer patient, the pelvic cavity and the lower limb site were fixed with the thermoplastic cast, and the treatment is performed with the image guidance. If the clinical consideration of the patient is not conducive to long lying or easy to move, we should use the vacuum bag and as far as possible to extend the fixed range, it could also reduce the positioning error without using of image guidance.
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