Hayashi N, Kato H, Yada R, Matsunaga T, Ehara I, Adachi Y
Faculty of Radiological Technology, School of Health Sciences, Fujita Health University, Toyoake, Aichi.
Department of Radiology, Seirei Hamamatsu General Hospital, Hamamatsu, Shizuoka.
Med Phys. 2012 Jun;39(6Part11):3732. doi: 10.1118/1.4735186.
Gafchromic film for quantitative analysis was renewed from EBT2 to EBT3 film in November 2011. The purpose of this study is to investigate the relevant characteristics of EBT3 film for its application in dosimetric verification for IMRT/VMAT or proton therapy.
We investigated the characteristics of EBT3 film with comparison of previous EBT2 film. The experiments in this study composed two categories. At first, the photo spectroscopy for the irradiated film was compared between EBT2 and EBT3. The film 1 day after the irradiation was analyzed by a photo spectrometer (SR520: JASCO Corporation, Japan). Secondly, we investigated several calibration curves which obtained by same batch. The films were calibrated by irradiation the films to 13 dose steps. The irradiated films were scanned by a flatbed scanner (ES-10000XL, Epson-Seiko Corporation, Japan). The difference on scan orientation was evaluated alternate portrait and landscape directions. The photon and proton beams were delivered from Clinac 21EX (Varian) and Mitsubishi machine, respectively.
The peak absorption wavelength of EBT3 film and its response at all active range were basically same with that of EBT2 film. The peak wavelength of photo absorption in EBT3 was observed at 585 and 634 nm. The fog optical density was increased due to the hazy matte polyester for active layer. However, there is no change the tendency of the calibration curve responding to megavoltage photon and proton beams. The scan orientation dependency of EBT3 film was observed with similar to EBT2 film. The optical density of portrait orientation was 10% higher than that of landscape orientation.
The dosimetric characteristics of EBT3 film were basically same with EBT2 film. With regard to the matte polyester, the creation of Newton's rings during scanning procedure was reduced. However, the suitable scan protocol should be used for accurate film dosimetry.
用于定量分析的放射变色薄膜于2011年11月从EBT2薄膜更新为EBT3薄膜。本研究的目的是探究EBT3薄膜在调强放射治疗/容积旋转调强放射治疗或质子治疗剂量验证中的相关特性。
我们通过与之前的EBT2薄膜对比来研究EBT3薄膜的特性。本研究中的实验分为两类。首先，比较EBT2和EBT3辐照后薄膜的光谱。辐照1天后的薄膜用光谱仪（SR520：日本JASCO公司）进行分析。其次，我们研究了同一批次获得的几条校准曲线。通过将薄膜辐照至13个剂量步长进行校准。辐照后的薄膜用平板扫描仪（ES - 10000XL，日本爱普生精工公司）进行扫描。交替以纵向和横向方向评估扫描方向的差异。光子束和质子束分别由Clinac 21EX（瓦里安公司）和三菱设备提供。
EBT3薄膜的峰值吸收波长及其在所有有效范围内的响应与EBT2薄膜基本相同。EBT3中光吸收的峰值波长在585和634纳米处被观测到。由于活性层使用了朦胧的磨砂聚酯，雾度光密度增加。然而，校准曲线对兆伏级光子束和质子束响应的趋势没有变化。观察到EBT3薄膜的扫描方向依赖性与EBT2薄膜相似。纵向方向的光密度比横向方向高10%。
EBT3薄膜的剂量学特性与EBT2薄膜基本相同。关于磨砂聚酯，在扫描过程中牛顿环的产生减少。然而，为了准确进行薄膜剂量测定，应使用合适的扫描方案。
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