6 MV X-ray照射後綠豆生長的放射敏感度量化:修訂的標靶模式實驗

Quantification of the In Vitro Radiosensitivity of Mung Bean Sprout Elongation to 6 MeV X-ray: A Revised Target Model Study

王慈慧(TZU-HWEI WANG)

指導教授 ： 潘榕光

中臺科技大學/健康科學院/醫學影像暨放射科學系暨研究所/博士(2017年)

摘要

本論文主要是利用6-MeV直線加速器在不同劑量照射下，藉由綠豆發芽平均生長長度來量化輻射敏感度；以往探討輻射劑量與細胞存活曲線關係，多以線性平方模式為探討，即生長曲線與劑量一次方及兩次方相關。 而本論文則是提出以修訂的靶核理論成功的解釋存活率。修訂後的標靶模式是導入卜瓦松分配數學理論，驗算後發現理論估算與實際數值高度吻合。此種模式說明不同的有效靶體積將導致不同的輻射敏感度，並由6 MV X-ray在不同劑量 (1, 2, 5, 10, 20, 50, 100, 200 or 400 Gy) 照射下，綠豆發芽的情況得到證實。 在具體的實驗規劃下，5000個新鮮綠豆，隨機分佈入100盤培養皿，依照不同澆水時間點，距離照射時間兩個小時前開始澆水，每間隔兩個小時澆水(5ml)為一組，以此遞延共得十組。所有澆水後的培養皿放置室溫25℃內，各組在照射前不同的時間點澆水，得到不一樣的有效靶體積。經不同劑量的X射線照射後70小時量測各組平均發芽長度並紀錄，當作綠豆的輻射敏感度指引。結果顯示在照射前6或16小時澆水的組別，其發芽長度最短，顯示在這兩組的有效靶體積最大；實驗結果 綠豆照射後生長支持一次打擊 ”0 hit” 模式，若延伸到二次打擊模式 ”0+1 hit”，理論上體積應變大2.14倍才能得到相同的結果。

關鍵字

標靶模式 ； 發芽長度輻射敏感度 ； 輻射敏感度 ； X光

並列摘要

In this study, a revised target model for quantifying the in vitro radiosensitivity of mung bean sprout elongation to 6-MeV X-rays was developed. The revised target model, which incorporated the Poisson prediction for a low probability of success, provided theoretical estimation that were highly consistent with the actual data measured in this study. The revised target model correlated different in vitro radiosensitivities to various effective target volumes and was successfully confirmed by exposing mung beans in various elongation states to various doses of 6-MeV X-rays. For the experiment, 5000 fresh mung beans were randomly distributed into 100 petri dishes, which were randomly divided into ten groups. Each group received an initial watering at a different time point prior to X-ray exposure, resulting in different effective target volumes. The bean sprouts were measured 70 hr after X-ray exposure, and the average length of the bean sprouts in each group was recorded as an index of the mung bean in vitro radiosensitivity. Mung beans that received an initial watering either six or sixteen hours before X-ray exposure had the shortest sprout length, indicating that the maximum effective target volume was formed within that specific time period. The revised target model could be also expanded to interpret the “two-hit” model of target theory, although the experimental data supported the “one-hit” model. If the “two-hit” model was sustained, theoretically, the target size would be 2.14 times larger than its original size to produce the same results.

並列關鍵字

target model ； sprout elongation ； radio sensitivity ； X-ray

參考文獻

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