On the spectral characterization of radiochromic films irradiated with clinical proton beams
On the spectral characterization of radiochromic films irradiated with clinical proton beams
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DOI：
10.1088/1361-6560/ab23cd
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发表时间：
2019-07-01
影响因子：
3.5
通讯作者：
Khan, Rao
中科院分区：
文献类型：
--
作者：
Darafsheh, Arash;Leon-Marroquin, Elsa Y.;Khan, Rao
放射致色膜在常规外束放射治疗中的临床剂量学应用已得到广泛的研究。随着质子治疗实践的增加，这种膜被方便地使用；然而，他们的光谱表征这种模式是缺乏的。本文研究了EBT3放射变色膜在Mevion S250 （TM）临床质子束照射下的反应。研究了膜的剂量、剂量率、批次间、灵敏度和线性能量转移（LET）依赖关系。利用展开布拉格峰质子束辐照不同批次的放射性变色膜，辐照剂量在0.1-15 Gy之间。在400 ~ 800 nm波长范围内测量吸收光谱，分辨率为2.5 nm。为了比较，使用平板扫描仪测量了薄膜的光密度。净吸收光谱显示出以636 nm和585 nm为中心的两个特征吸收带。然而，在三个不同的薄膜批次中，当剂量超过一定的批次依赖水平（如4-10 Gy）时，在636 nm波段观察到饱和效应，表现为加宽/分裂外观。光谱形状的差异导致了不同灵敏度的剂量-响应曲线。在0.1 ~ 6 Gy范围内，三批膜均具有较高的光谱灵敏度。对于给定剂量，随着剂量率的变化，光谱没有明显变化。在本研究中，质子束辐照的EBT3薄膜的平均LET值在1.14-6.50 keV μ m（-1）之间，对LET没有明显的依赖性。然而，在给定的剂量下，用质子照射的薄膜的光谱响应比用光子照射的薄膜低5%。
Radiochromic films have been widely studied for clinical dosimetry in conventional external beam radiation therapy. With an increase in practice of proton therapy, such films are being conveniently used; however, their spectroscopic characterization for this modality is lacking. This work investigated the response of the EBT3 radiochromic films irradiated in a Mevion S250 (TM) clinical proton beam. Dose, dose rate, inter-batch, sensitivity, and linear energy transfer (LET) dependencies of the films were studied. Pieces of the radiochromic films from different batches were irradiated using a spread-out Bragg peak (SOBP) proton beam at dose levels between 0.1-15 Gy. Absorption spectra were measured in the wavelength range of 400-800 nm with 2.5 nm resolution. For comparison, the optical density of the films was measured using a flatbed scanner.The net absorbance spectra showed two characteristic absorption bands centered at 636 nm and 585 nm. However, a saturation effect, manifested as broadening/splitting appearance, was observed in the 636 nm band for doses beyond a certain batch-dependent level similar to 4-10 Gy, in the three different film batches studied. The differences in the spectral shape led to dose-response curves with variable sensitivity. In general a high spectral sensitivity was observed in 0.1-6 Gy range for the three film batches. For a given dose, no significant change in the spectra was observed with change in the dose rate. No significant dependency on the LET was observed for the EBT3 films irradiated with proton beams with dose-averaged LETs ranging from 1.14-6.50 keV mu m(-1) studied in this work. However, at a given dose, similar to 5% lower spectral response was observed in the films irradiated with protons compared to their counterparts irradiated with photon beams.