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分段照野技術在攝護腺癌的臨床應用

Clinical Applications of Segmental Field Technique for Prostate Cancer Treatment

摘要


本文由照野內外加分段小照野技術,使劑量曲線分布能更順著攝護腺腫瘤,以減少直腸劑量,並以此提高整個攝護腺腫瘤的劑量給予。 選取六位曾在本科利用分段照野技術治療的攝護腺癌病患資料。每位病患皆使用固定系統,以及接受電腦斷層掃瞄,影像厚度為3mm。所得影像傳至ADAC Pinnacle治療計畫系統內,執行兩種治療計畫。第一,三度空間順形計畫,採六個共平面射束---兩側前後斜角照野與兩側照野;第二,利用第一種模式的六個角度,並各於兩側後斜角照野內外加一個遮擋直腸的分段小照野。兩種計畫每次給予腫瘤200 cGy,總劑量為7000 cGy,各射束比重以正向思考調整至最佳化。比較兩種計畫之腫瘤內劑量均勻度,等劑量曲線分布與攝護腺腫瘤、直腸、膀胱、股骨的劑量體積直方圖。 分段照野技術相對於三度空間順形計畫而言,50%的直腸體積劑量皆減少,且若給予腫瘤劑量為7000 cGy時,接受劑量大於6500 cGy的直腸體積也由5-38%減少到2-17%,但是使用分段照野技術的腫瘤劑量均勻性較差。此外,兩種計畫的膀胱與股骨劑量皆無差異太大。 分段照野支術是於原照野內外加一個小照野,並不會增加計畫的複雜性,且劑量曲線也能順著攝護腺腫瘤部份,減少直腸接受到高劑量的危險,因此以此模式治療,可提高攝護腺腫瘤治療劑量,而不增加直腸的副作用。

並列摘要


Using the concept of intensity modulation, we used a segmental technique of the “field-within-a-field” in order that the isodose distributions of the planning be more conformed along the prostate, and minimize the doses to the rectum. Six patients, previously treated using radiotherapy for adenocarcinoma of the prostate, were studied. Each patient was treated using immobilization and preplanning computed tomography (CT) scans (3-mm slice spacing). Two techniques were planned: the 6-field conformal technique using bilateral anterior and posterior oblique fields and bilateral fields, and the segmental technique which added small fields sparing the rectum at bilateral posterior oblique angles. Finally, we compared the isodose distributions and dose-volume histograms of the prostate tumors, rectum, bladder and femoral head using the three-dimensional (3D) conformal and segmental techniques. Compared with the 3D conformal technique, the use of the segmental technique resulted in bad dose uniformity of the tumors and a lower dose of 50% to the rectum volume. When we treated the prostate using 7000 cGy, the volume of the rectum received 6500 cGy using segmental plans which were 2-17% lower than the 5-38% when using 3D conformal plans. In addition, the differences between the doses found in the bladder and the femoral head were not significant. This technique is a “field-within-a-field” technique without increasing the complexity of the planning process. It not only increases the dose to the prostate cancer, but also minimizes doses to the rectum to reduce complications.

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