直線加速器立體定位放射手術系統

A System for Stereotactic Radiosurgery with Linear Accelerator

羅濟慶(Chi-Ching Lo) ； 趙良曉(Liung-Sheau Chao) ； 陳光耀(Kuang-Yao Chen) ； 林光大(Kuang-Tah Lin)

《放射治療與腫瘤學》 4卷4期 (1997/12) Pp. 271-279

https://doi.org/10.6316/TRO/199704(4)271

摘要

前言：本研究之目的，為在臺北榮民總醫院發展利用直線加速器給予顱內小腫瘤單次高劑量之照射方法。其照射精準度在機械幾何上可達1mm，而在劑量之準確度可達3％之誤差範圍內。
材料與方法：本研究設備是採用varian CL-1800直線加速器與Leksell立體定位系統。治療技術則使用多重非共面弧形照射並配合附加於鉛擋板溝槽之二級準直儀，其內部之圓柱形準直器之材質爲10cm厚之不誘鋼，其照野直徑由15mm到30mm ，可準確的限制劑量僅落於照射點上，而對於照射區之外，則劑量將會急速的向外下降；病患固定系統則包含立體定位固定環與固定於治療床的立體定位底座；定位框及等中心點指示器則用於定出照射靶擊中心位置；深度量尺可用來測量腫瘤距各不同方向與截面之照射深度。
結果：此系統測試之標準須達到1mm之機械幾何之準確度，在劑量之準確度須達到 3%；準直系統之漏射量須小於7％。劑量輸出率及組織與假體比表格已建立可供計算劑量，等劑暈分佈圖也已利用水假體測試系統建立完成，並經LiF熱發光晶片驗證。
討論：三度空間頭部立體定位放射治療計畫系統在整佃計畫中扮演著一個不可或缺的角色。而可用於測量至5mm 直徑大小照野面積之偵測器以及精密度達到1mm以下的光密度儀，亦為從事放射手術品質管制中必備的儀器。
結論：本研究之設備與基礎劑量研究都已完成，此技術已可供日後臨床使用與評估。
［放射治療與腫瘤學 1997; 4:271-279］

關鍵字

立體定位治療 ； 多重非共面弧形照射 ； 劑量急速下降梯度 ； 二級準直機 ； 等劑量分佈圖

並列摘要

Purpose：The aim of this study is to develop a technique at Veterans General Hospital-Taipei to irradiate small lesion in the brain to a high dose per fraction with 1mm geometric accuracy and 3% dosimetric accuracy.
Materials and Methods: The technique employs Varian CL-1800 linear accelerator with 10MV X-Ray and the Leksell stereotactic system. This treatment technique combines with multiple non-coplanar arc irradiation and secondary rigid collimator mouhting to the slot of block tray. The cylindrical collimator inserts are made by stainless steel with 10cm thickness. Their field size opening range from 15mm to 30mm in diameter and confine the accurate dose to the target and steep dose fall-off outside the target volume. The patient fixation system consists of stereotactic base ring and head fixing posts that can be directly mounted on the treatment couch. The target position frame and isocenter front pointer are used for adjusting the target point of isocenter. A ruler is used for measuring depth of tumor at various planes and directions.
Results：This system was systematically tested within 1-mm mechanical geometric and 2% dosimetric accuracy respectively. All of collimator inserts showed no flaw and the radiation leakage was less than 7%. Dose rate and tissue-phantom-ratio table had been setup for dosimetry purpose. Isodose curve were established by water phantom and verified by radiation sensitive films and TLD dosimetry.
Discussion：A three-dimensional computerized treatment planning system is essential for stereotactic radio-surgery device. Dosimetry detetors capable of measuring 5-mm diameter field and film dosimetry with 1mm accuracy are indispensable equipment for quality control of this radiosurgery procedure.
Conclusion: Apparatus test and basic dosimetry study had been complied; The technique is ready for future pre-clinical study and evaluation.
［Therapeot Radiol Oncol 1997; 4:27 1-279］

並列關鍵字

Stereotactic radiosurgery ； Non-coplanar ； Steep gradient dose ； Secondary collimator ； Isodose curve