銥－192射源插種治療攝護腺癌之劑量分佈

Dose Distribution of 192Ir High-dose-rate Brachytherapy of Prostate Cancer

葉恬綺(Tien-Chi Yeh) ； 許世明(Shih-Ming Hsu) ； 葉健一(Chien-Yi Yeh) ； 洪志宏(Ji-Hong Hong) ； 季匡華(Kwan-Hwa Chi) ； 陳爲立(Wei-Li Chen)

《中華放射線醫學雜誌》 32卷3期 (2007/09) Pp. 131-140

摘要

臨床上使用銥－192射源高劑量率近接治療攝護腺癌之程序十分複雜，故選擇適合量測近接治療之劑量驗證系統是一項重要議題；本實驗利用假體模擬量測銥－192射源近接治療攝護腺癌之劑量分佈情形。
本研究以自製攝護腺水箱假體模擬銥－192射源插種治療攝護腺癌之治療程序，使用玻璃劑量計(glass dosimeter，GD)及熱發光劑量計(thermoluminescence dosimeter，TLD)進行量測，評估劑量測量值與治療計畫系統計算值之誤差範圍。
玻璃劑量計間靈敏度之平均變異係數為2.05%，個體再現性平均變異係數為1.58%，計讀值與給予劑量間呈現線性關係，重複計讀值之再現性變異係數為0.67%，且於35日內可視為無消光效應，且200keV以上之光子能量可視為無能量依存性表現。假體量測部分，依所在位置分析量測值與電腦治療計畫計算值之一致性，在射源停留單點位置時，玻璃劑量計與熱發光劑量計之平均一致性分別為1.00±0.03(0.97~1.04)及1.01±03(0.96~1.05)；在射源停留多點位置的情況下，玻璃劑量計之平均一致性則為0.98±03(0.93~1.02)。
劑量計之校正結果得知，玻璃劑量計為適合使用量測臨床治療劑量之驗證系統。由假體內模擬近接治療攝護腺癌程序下之量測結果顯示，電腦治療計畫計算值與劑量計之量測值平均差異性小於±5%。

並列摘要

The clinical procedure of Ir-192 high-dose-rate (HDR) brachytherapy for the treatment of prostate cancer is quite complicated. It is an important issue to choose a suitable dosimetry system for HDR brachytherapy. In this study, in-phantom measurements simulating the 192Ir HDR brachytherapy for the treatment of prostate cancer were performed.
In this study, in-phantom measurement simulating the Ir-192 HDR brachytherapy for the treatment of prostate cancer was performed. The innovative glass dosimeters (GDs) and thermoluminescence dosimeters (TLDs) were calibrated and used for inphantom measurement. The discrepancy between measurements and doses calculated by treatment planning system (TPS) was analyzed.
The signal uniformity of the batch RPLGD is within 2.05% (coefficient of variation). The reproducibility of each GD was 1.58%, and the dose corresponded to the delivered dose showed a good linear dependence. The reproducibility of readout value from each GD was 0.67%, and showed no fading effect within 35 days. The GD also showed energy independence with the photon energy greater than 200keV. For in-phantom study, the compatibility (measured dose/calculated dose by TPS) was analyzed according to the location inside the phantom. For GDs and TLDs, the mean compatibility was 1.001±0.03 (range, 0.97 to 1.04) and 1.01±0.03 (range: 0.96 to 1.05), respectively, with single source dwell position. In multiple source dwell positions, the mean compatibility was 0.981±0.03 (range: 0.93 to 1.02) for GDs. These results showed that the differences between the experimental and TPS calculated values were within ±5%.
Results from the calibration of the dosimeters showed that GD was a suitable system for dosimetric measurement in radiation therapy.