影像導引放射治療時各項攝影裝置之輻射劑量探討－頭頸部器官之吸收劑量－

The comparison of radiaiton dose on head and neck region during processing of image-guided radiotherapy among different imaging devices

陳曉韻(Hsiao-Yun Chen)

指導教授 ： 連熙隆

高雄醫學大學/健康科學院/醫學影像暨放射科學系碩士班/碩士(2010年)

摘要

影像導引放射治療（image-guided radiotherapy，簡稱 IGRT）結合了影像導引技術與強度調控放射治療（intensity-modulated radiotherapy，簡稱 IMRT），藉由每日的影像攝影完成每日定位之確認來達到更精準的治療，但其定位時接受之電腻斷層模擬定位與治療前接受之影像導引攝影亦導致接受放射治療病患的正常組織接受了過去所沒有的低劑量輻射線。
本研究利用熱發光劑量計（thermoluminescence dosimeter，簡稱 TLD） TLD-100 晶片置入擬人假體中，分別測量頭頸部癌症病患接受Tomotherapy Hi-Art system 之 MVCT（megavoltage computed tomography，簡稱 MVCT）、Varian LINAC IX 之 CBCT（Cone Beam Computed Tomography，簡稱 CBCT）與 OBI （On-Board Imager，簡稱 OBI）的影像導引放射治療時，其頭頸部器官所受各項影像導引裝置攝影之曝露劑量，並量測 Philips AcQSim 與 Philips Brilliance電腻斷層模擬定位機（computed tomography simulator，簡稱 CT-sim）之頭頸部各器官劑量。
Tomotherapy Hi-Art system 之頭頸部腫瘤病患影像導引攝影的頭頸部器官 MVCT單次劑量為 1.1至1.76 cGy，Varian LINAC IX 之 CBCT 單次劑量為 0.11 至0.40 cGy，OBI 單次劑量小於0.1 cGy。
治療計畫所需的電腻斷層模擬定位機頭頸部掃描單次劑量約為 2.98 至 5.42 cGy，劑量較單次影像導引裝置攝影高。但影像導引裝置曝露次數多，頭頸部治療分次35次之所累積之吸收劑量如下：使用 Tomotherapy 之 MVCT 為影像導引裝置將接受到 38.5-61.6 cGy 的劑量；使用CBCT為影像導引裝置時將接受到 3.85-14 cGy的劑量；使用OBI為影像導引裝置將接受到小於 3.5 cGy 的劑量。
影像導引放射治療是目前放射治療的趨勢，但病患在接受放射治療外又接受了額外的影像導引劑量，因此需瞭解與評估影像導引攝影所增加的劑量，並長期追蹤這些劑量對病患產生之生物效應。

關鍵字

影像導引放射治療 ； 熱發光劑量計 ； 吸收劑量

並列摘要

Image-guided radiotherapy (IGRT) is the combination of the image-guided technique and intensity-modulated radiotherapy (IMRT) with the daily image verification to make the treatment more precise. Patients may receive extra low dose radiation in the normal tissue during CT Simulation and the pre-treatment image-guided technique due to the process of IGRT protocol.
This study was designed to used the thermoluminescence dosimeter (TLD) TLD-100 chips to measure the dose of lens, eye balls, optical nerves, chiasm, nose tip, lip and thyroid glands in a humanoid phantom in which radiation was delivered from Tomotherapy Hi-Art system megavoltage computed tomography (MVCT), Varian LINAC IX cone beam CT (CBCT) and Varian LINAC IX on-bored imager (OBI) while processing the image-guided therapeutic protocol. The dose of CT scanning of Philips AcQSim and Brilliance CT-simulator were also measured in this study.
The single fractional doses of Tomotherapy Hi-Art system MVCT were 1.1 to 1.76 cGy, Varian LINAC IX CBCT were 0.11 to 0.40 cGy , less than 0.1 cGy in Varian LINAC IX OBI. The absorbed doses of CT-Sim were 2.98 to 5.42 cGy. Although the CT-Sim have more absorbed doses than that of IGRT devices, but when a patient was processing the IGRT technique, a whole course of radiotherapy will need more fractionation numbers when more IGRT processing is required than only process one CT-Sim scanning. The Image-guided devices may increase more radiation dose, the accumulation dose of a 35 process of fractional radiotherapy of head and neck cancer radiotherapy were calculated as follows: Tomotherapy Hi-Art system MVCT were 38.5 to 61.6 cGy, 3.85 to 14 cGy of Varian LINAC IX CBCT, less than 3.5 cGy of Varian LINAC IX OBI.
IGRT is an innovative technological improvement in radiation oncology, but the radiation absorbed doses of image-guided is indeed need more assessment and evaluation, and we need to concern the biologic effect of low dose radiation in the following year after complete the whole course of radiotherapy.

並列關鍵字

image-guided radiotherapy ； TLDs ； radiation dose

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