nanoDot型光激發光劑量計評估電腦斷層劑量輸出量測不確定度研究

Measurement uncertainty assessment of nanoDot optically stimulated luminescence dosimeter in computerized tomography output

蕭文田(Wen-Tien Hsiao) ； 陳思宇(Sih-Yu Chen) ； 陳家睿(Jia-Rui Chen) ； 蔡世詠(Shih-Yung Tsai) ； 曾柏欽(Bo-Qin Zeng) ； 賴律翰(Lu-Han Lai)

《加馬》 51期 (2020/12) Pp. 43-52

摘要

氧化鋁（aluminum oxide）材料光激發光劑量計（optically stimulated luminescent dosimeters, OSLD）被認為是用於測量電腦斷層攝影劑量的一種新型劑量計，特別是用於測量病患劑量。儘管這種劑量計的使用日漸普及，但文獻中尚未建立適當的劑量計校正技術。劑量計廠商提供了校正程序，但不確定度相對較大。本研究目的為評估兩種應用於電腦斷層攝影之劑量計校正的臨床方法，並使用這些技術測量相關的不確定度。使用美國Landauer光激發光劑量計和microSTAR計讀儀，並利用三種獨立的校正程序來計算一系列電腦斷層攝影條件下的劑量。（a）使用廠商提供的方法進行校正；（b）空氣中相對於120 kVp電腦斷層攝影光譜進行校正以及（c）百萬伏特電壓射束（^(60)Co）進行校正。上述每種方法測得的劑量與Farmer‐Type游離腔測得劑量進行比較並計算量測不確定度。對於電腦斷層攝影和百萬伏特電壓校正方法，各種不同的CT掃描參數80～140 kVp，光激發光劑量計測量的劑量與游離腔誤差6％以內。使用廠商提供的程序進行校正時，光激發光劑量計測得的劑量平均比游離腔劑量低14.9％。本研究評估兩種技術以替代廠商提供的校正方法，為光激發光劑量的測量提供了高精確度參考。

關鍵字

校正 ； 電腦斷層掃描儀 ； 輻射劑量 ； 光激發光劑量計

並列摘要

Aluminum oxide based optically stimulated luminescent dosimeters (OSLD) have been recognized as a useful dosimeter for measuring CT dose, particularly for patient dose measurements. The aim of this study was to evaluate two clinical approaches for calibrating these dosimeters for CT applications. Three unique calibration procedures were used to calculate dose for a range of CT conditions using a commercially available OSLD and reader. The three calibration procedures included calibration (a) using the vendor‐provided method, (b) relative to a 120 kVp CT spectrum in air, and (c) relative to a megavoltage beam (^(60)Co). The dose measured using each of these approaches was compared to dose measured using a calibrated farmer‐type ion chamber. The uncertainty in the dose measured using each approach was determined. For the CT and megavoltage calibration methods, the dose measured using the OSLD nanoDot was within 6% of the dose measured using an ion chamber for a wide range of different CT scan parameters (80-140 kVp, and with measurements at a range of positions). When calibrated using the vendor‐recommended protocol, the OSLD measured doses were on average 14.9% lower than ion chamber doses. This research provides high precision for OSLD‐based measurements in Computed Tomography.

並列關鍵字

calibration ； computerized tomography ； dosimetry ； optically stimulated luminescent dosimeters