使用錐狀射束電腦斷層與多切面電腦斷層影像進行高解析度凝膠劑量分析

High-Resolution Gel Dosimetry Using Multi-detector Computed Tomography and Cone-Beam Compute Tomography

趙璽雅(His-Ya Chao) ； 曾玉華(Yuk-Wah Tsang) ； 張志嘉(Chih-Chia Chang) ； 江品儀(Pin-Yi Chiang) ； 謝栢滄(Bor-Tsung Hsieh)

《中華放射線技術學雜誌》 37卷4期 (2013/12) Pp. 215-221

摘要

具有三維（3D）劑量解析能力的輻射量測之需求與日俱增，其中聚合物凝膠劑量計為近年來非常熱門的研究議題之一。然而一般廣泛使用丙烯醯胺（acrylamide）單體具有神經毒性，不易在臨床上推廣與應用。本研究以異丙基丙烯醯胺（N-isopropyl-acrylamide）為單體，製作改良型NIPAM凝膠劑量計（n-NIPAM），n-NIPAM使用凝膠（5%）、單體（5%）、交聯劑（3%），並加入5mM THPC以排除氧氣，使其毒性低、靈敏度和再現性佳，是一種深具潛力的凝膠劑量。實驗利用直線加速器給予1Gy至14Gy的吸收劑量進行研究，將己照射的凝膠劑量計分別使用多列偵測器式電腦斷層（Multi-detector computed tomography：MDCT）與錐狀射束電腦斷層（Cone-beam computed tomography：CBCT）來當計讀的工具，並比較單管計讀與多管計讀、分次照射計讀之差異。n-NIPAM 平均敏感度是0.6875 CTN/Gy，單管計讀方式MDCT與CBCT的平均敏感度分別是0.68 CTN/Gy與0.98 CTN/Gy，多管計讀方式平均敏感度分別是0.59 CTN/Gy與0.48 CTN/Gy，表示其劑量敏感度反應CBCT優於MDCT，因此選用CBCT用來計讀凝膠劑量學的技術是可行的。分次照射凝膠劑量與單次照射差異最大可達25.10%，其結果可知凝膠劑量計應用於臨床病人的體腔數日時，凝膠劑量計劑量反應曲線需做修正。

關鍵字

聚合物凝膠 ； 多列偵測器式電腦斷層 ； 錐狀射束電腦斷層 ； 劑量敏感度

並列摘要

Radiotherapy attempts to deliver complex three-dimensional (3-D) dose distribution. The polymer gel dosimeter, which can measure the 3-D dose output, is suitable for clinical use. However, acrylamide with neurotoxicity can't be used in clinical area. This study developed an n-NIPAM gel dosimeter based on an N-isopropyl-acrylamide monomer, consisted of 5% gelatin, 5% monomer, and 3% cross-linker combined with 5mM tetrakis (hydroxymethyl) phosphonium chloride(THPC) for deoxygenation and in order to decrease the toxicity and improve the sensitivity and the reproducity. Dose responses of 1-14 Gy delivered by a linear accelerator were examined. In this study, single gel tube, multiple gel tubes and single gel tube with multiple exposured were scanned and read by multi-detector computed tomography (MDCT) and cone-beam computed tomography (CBCT) to analyze the difference of radiation doses in the gel tubes. The average radiation sensitivity of n-NIPAM gel was 0.6875 CTN/Gy, the sensitivity of single tubes mold read by MDCT and CBCT were 0.68 CTN/Gy and 0.98 CTN/Gy, and the multiple tubes mold read by MDCT and CBCT were 0.59 CTN/Gy and 0.48 CTN/Gy. The radiation sensitivity of CBCT was better than MDCT. The reading difference between single exposure and multiple exposure was 25.1%. That means the dose curve of n-NIPAM gel used in patient multiple treatment dose verification would be modified before used.

並列關鍵字

polymer gel ； multi-detector computed tomography ； cone-beam computed tomography ； dose sensitivity