光刺激發光劑量計應用於放射治療低劑量輻射度量之系統調測

Commissioning of Optically Stimulated Luminescence Dosimeters for Low Dose Radiation Measured in Radiotherapy

陳韋霖(Wei-Lin Chen) ； 梁雲(Wan Leung) ； 張寶樹(Pao-Shu Chang) ； 劉明祥(Ming-Hsiang Liou)

《南臺灣醫學雜誌》 14卷1期 (2018/06) Pp. 21-31

https://doi.org/10.6726/MJST.201806_14(1).0003

摘要

目的：使用醫用直線加速器之標稱射源，針對光刺激發光劑量計(Optical stimulated luminescence dosimeter,OSLD)之特性進行量測與校正，以供放射治療照野外正常組織之低劑量輻射度量並提高準確性。方法：評估一批光刺激發光劑量計(In Lightnano Dot^(TM))之批次特徵(batch characteristic)、再現性(reproducibility)、消光性(fading)、劑量率依存性(dose rate dependence)及訊號衰減(signal depletion per read)等特性，並同時建立劑量與計讀值之關係曲線(linearity)。結果：OSLDs於三次不同劑量範圍其平均值和標準差分別為8 0 . 9 4 ± 2 . 16 counts、57.40±1.20 counts及28.14±0.82 counts，準確度均在±3%之內，重複計讀再現性及輻射回應再現性C.V.值分別介於0.54%~2.33%和0.94%~2.95%，消光性穩定於2.1%以內，劑量率依存性於1.12%以內，訊號衰減僅0.25%。劑量回應關係曲線於劑量範圍2至40cGy間， 其關係式為y=2.7158x+1.3979，x為吸收劑量，y為計讀信號值。結論：OSLDs尺寸小、劑量線性、再現性佳、無劑量率依存性，可重複使用、重複計讀，操作便利穩定度佳，除了目前已知應用亦適合於放射治療低劑量度量。

關鍵字

光刺激發光劑量計 ； 放射治療劑量度量 ； 低劑量輻射

並列摘要

Objective: To commission and correction Optical Stimulated Luminescence Dosimeters (OSLDs) using the medical linear accelerator nominal source for out-of-field normal organs low dose radiation measurement in radiotherapy and improves the accuracy. Methods: Evaluate a number of OSLDs include batch characteristic, reproducibility, fading, dose rate dependence and signal depletion per read, then established the linearity between dose and counts. Results: The mean and standard deviation of OSLDs in three different dose ranges were 80.94 ±2.16 counts, 57.40±1.20 counts and 28.14±0.82 counts, respectively. The accuracy within±3%, reproducibility of repeat reading and radiation response C.V. were between 0.54%-2.33% and 0.94%- 2.95%, respectively. The fading was stable at 2.1%, dose rate dependence within 1.12%, and the signal depletion per read was only 0.25%. Dose response curve in the low dose range between 2 to 40cGy, the relationship formula is y=2.7158x+1.3979, x is the absorbed dose, y is the reading signal value. Conclusions: OSLDs are small size, dose response linearity, good repro- ducibility, dose rate independent, reusable, repeatable reading, convenient and stable operation not only for the currently applications but also appropriate for low dose measurement of radiotherapy.

並列關鍵字

OSLD ； radiotherapy dose measurement ； low dose radiation