以多分子膠質體之輻射劑量測量技術建立貝它與伽瑪放射源於近接治療時三度空間劑量分佈之研究

The Study of Beta and Gamma Radioisotopes Brachytherapy 3-D Dose Distribution by Polymer Gel Dosimetry Technique

吳嘉明(Jia-Ming Wu) ； 葉世安(Shyh-An Yeh) ； 蕭光吟(Kuan-Yin Hsiao) ； 謝柏滄(Bor-Tsung Hsieh) ； 趙敏(Max M. Chao) ； 陳宗哲(Tzong-Jer Chen) ； 梁雲(S. W. Leung)

《台灣應用輻射與同位素雜誌》 4卷4期 (2008/12) Pp. 521-527

https://doi.org/10.29832/TJARI.200812.0001

摘要

心藏的冠狀動脈在經過血管支架治療後，一般在半年內會有40到60%的再狹窄的發生率；本研究便是利用多分子膠質體(polymer gel)劑量測量系統，對Re-188的貝它射源，做三度空間的劑量分佈技術建立與開發之研究(13-15)，以便將此放射源置入心藏的冠狀動脈內做有計劃性的破壞時對治療病灶在給予劑量上有充份的了解；特別在近距離1公分以內的劑量評估，。尤其是貝它射源一般能量均小於3MeV之情況下，其射程最多在1公分以內，因此近距離三度空間劑量系統的建立有其必要性。此處以謝柏滄博士所提供的Re-188的貝它射源，對多分子膠質體經此Re-188的貝它射源照射過後，以MRI之R2頻率先求出磁振造影的訊號分佈，之後再把此訊號分佈依訊號相對的劑量特性曲線進一步求出其劑量分佈，而將其立體化的劑量分佈呈現出來。同時，在測量過程中，會以底片計讀系統和多分子膠質體所做出來的劑量結果做點和面的比較及驗證。以期運用多分子膠質體建立Re-188的貝它射源在近距離內的劑量測量系統。

關鍵字

近接治療 ； 貝它射源 ； 伽瑪射源 ； 多分子膠質體 ； 劑量系統

並列摘要

Teletherapy and brachytherapy are two major trends in radiation therapy. In brachtherapy, minimizing the normal tissue dosage and giving the optima1 prescribed dose exactly to the lesions are the princip1e of this approach. Gamma radiation in brachtherapy for ma1ignancy has been used for many years. Ra-226 and Co-60 are the most often used radioisotopes in the past two decades. Currently, Cs-137 and Ir-192 have played them major role in this treatment. Furthermore, the technique of cardiovascular radiation therapy has been developed for preventing restenosis in Western countries. Re-188, Sr-90 and P-32 radioisotopes have been used as beta emitter for this purpose. The most importance and difficult in brachtherapy are the establishment of the dosimetry system. Usually, thermal 1uminance dosimetry (TLD), ion chambers or film dosimetry are used for measurement in brachytherapy. However, the dose distribution cannot be proper display in 3-dimensionally. Especial1y, the dose distribution in the nearest distance to the source is hard to evaluation. In this study, we utilize polymer gel dosimetry system to estab1ish and develop the 3-dimensional dose distribution for Ir-192 and Re-188 radioisotopes as gamma and beta emitters respectively in brachytherapy. The dose distribution within 1 cm from source is the range of interest for patients in brachtherapy. Especial1y, the energy of beta emitter is usually less than 3 MeV, the emitted range is about 1 cm, the 3-D dosimetry system is necessary for dose evaluation. Technically, polymer gel expose in radiation, the relaxation time (R2) of MRI will be used to analyze the absorbed dose of the gel. The dose distribution can be showed in stereotactically. Meanwhile, the film dosimetry measurement will also be performed for comparing and verifying. The development of polymer gel dosimetry will help us to understand the real prescribed dose for disease in clinical application.

並列關鍵字

brachytherapy ； gamma and beta emitters ； polymer gel dosimetry