多模式螺旋斷層放射治療儀對鼻咽癌治療在照野外劑量之測量

Out-of-Field Dose Measurements of NasoPharyngeal Cancer using Helical TomoTherapy

謝震球(Chun-Kau Tse)

指導教授 ： 張寶樹

高雄醫學大學/健康科學院/醫學放射技術學研究所/碩士(2007年)

摘要

本文利用LiF熱發光劑量計測量以多模式螺旋斷層放射治療儀(Helical TomoTherapy)治療鼻咽癌之照野外劑量。多模式螺旋斷層放射治療儀的特點是其能利用螺旋式強度調控放射治療技術(Intensity Modulated Radiation Therapy，IMRT)及影像導引放射治療的技術(Image-Guided Radiation Therapy，IGRT)，以影像導引的功能，移除因器官位移(organ motion)、擺位誤差(set-up error)等因素。以多模式螺旋斷層放射治療儀治療鼻咽癌之過程中，機器所輸出的監控單位(monitor units，M.U.)約為8000監控單位(M.U.)，其為直線加速器強度調控治療的6-8倍之多。本文進而探討鼻咽癌治療的高單位輸出所產生散射劑量而導致可能誘發二次癌症(secondary malignancy)的機率。
結果顯示以多模式螺旋斷層放射治療儀治療鼻咽癌之整個放射治療療程中，計40個分次(fraction)共72 Gy的腫瘤劑量，眼睛水晶體劑量為3.91 Gy，小於誘發白內障的低限劑量(threshold dose)，而心臟及腎臟劑量分別是0.49及0.11 Gy，遠低於其耐受劑量(tolerance dose)。食道及肺尖的輻射危險度約為0.7~4.45%，視其靠近治療照野位置而定。其他器官的輻射危險度約為0.2~0.08%，全身有效劑量約為0.52 Sv，其致死癌病機率約為2.6%。

關鍵字

多模式螺旋斷層放射治療儀 ； 螺旋式強度調控放射治療技術 ； 影像導引放射治療的技術二次癌症

並列摘要

The purpose of this study is to measure out-of-fields radiation doses using TLD-100H(LiF) for nasopharyngeal cancer(NPC) treatment models by helical TomoTherapy. A feature of helical TomoTherapy has Intensity Modulated Radiation Therapy(IMRT) and Image-Guided RadioTherapy (IGRT) systems that becomes negligible organ motion and set-up error from the treatment procedures. But TomoTherapy deliver about 8000 monitor units more than 6-8 times of IMRT technique with Linear Accelerator(LINACS). This study was to evaluate the probability of secondary malignancy with scatter radiation which was depended on high MU output for helical TomoTherapy.
The results of NPC prescription doses were 72 Gy in 40 fractions by helical TomoTherapy. Len received 3.91 Gy, which was less than the threshold dose of lens induced cataract. Heart received 0.49 and 0.11Gy, which were far less than their maximal tolerance dose. Esophagus and lung apex had about 0.7~4.45% risks to decide that the treatment thickness, other organs about 0.2~0.08% risk. Whole doses had about 0.52 Sv, and the nominal fatal cancer probability rate was about 2.6%.

並列關鍵字

Helical TomoTherapy ； Intensity Modulated Radiation Therapy ； Image-Guided Radiation Therapy ； secondary malignancy

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