- 期刊
Characteristics, Advantages and Limitations of a Treatment Planning System for Gamma Knife Radiosurgery
加馬刀放射手術治療計畫的特色優點及限制
摘要
本文主旨在介紹加馬刀治療計畫KULA系統的特色，並以一復發鼻咽為例，討論臨床上使用該系統之優缺點。 自1993年3月起本院開始以立體定位加馬手術刀治療腦內之動靜脈畸型，聽神經瘤及其他顱內良性或惡性腫瘤。為計算201個鈷六十射源的合成劑量，此種放射手術應用了特別設計的治療計畫電腦軟體(KULA)。治療的原理是堆積不同大小之照射聚焦中心(shots)來涵蓋腫瘤範圍。KULA使用三度空間劑量計算，並以水平面、冠狀切面、矢狀切面等二度空間的方式呈現劑量分布圖。不但可以用單一聚焦中心治療較小的腫瘤，堆積最多達十二個聚焦中心也可治療較大的腫瘤。計算結果可獲得相當良好的精確度及令人滿意的劑量分佈，但對於體積較大且形狀不規則的腫瘤，例如復發於顱底的鼻咽癌，治療計畫所花的時問相當冗長。主要原因之一是KULA系統在輸入指令，執行計算及顯示等劑量曲線圖的功能上，效率不佳。它未能將影像檢查資料納入計畫系統內，也沒有提供使用者與圖形的介面。雖然經過多次的修正後仍能得到滿意意的劑量分布，但所費的時聞相當不經濟。在新一代的治療計畫軟體尚未啟用前，熟悉KULA系統的特性及聚焦中心的配置組合原則，是進行高效率治療計畫的唯一途徑。
並列摘要
Stereotactic radiosurgery refers to the use of small, well-collimated beams of ionizing radiation to ablate intracranial lesions. In our hospital radiosurgery with the Leksell Gamma Knife was used to treat AVM, acoustic neuroma, meningioma, glioma and other benign or malignant brain tumors. To deal with 201 cobalt-60 sources of the Gamma Knife, the complex dosimetry was performed using specially developed computer software (KULA). The treatment planning with KULA for a recurrent nasopharyngeal cancer after external beam radiotherapy is presented. After initial rough planning with 12 shots to cover the tumor, repeated revisions of coordinates and weights of most shots resulted in a 50% isodose curve matching the tumor contour in 3 dimensions. The possibility of neurological complication is low due to the relative low dose (＜30%) to the neighboring optic nerve and brain stem. Though the result of this laborious and prolonged treatment planning is good, the amenity and efficiency of using KULA are unsatisfactory for this large and irregular shaped tumor. When stacking of multiple isocenters or shots in 3 dimensions to fill the tumor volume, the melded isodose curves can be very differnt from the simple combination of individual curves and trials and errors are inevitable. For efficient planning of large and irregular shaped tumors with KULA, it is essential to be familiar with the principle of allocation and methods of fine adjustment of parameters of shots.