具有角旋转的Gafchromic EBT2膜的Absorption spectrum
Absorption spectrum of Gafchromic EBT2 film with angular rotation
摘要：
吸收光谱的研究在胶片剂量学中具有重要意义，因为胶片的吸收光谱与胶片的总吸收剂量有关。我们研究了Gafchromic EBT 2薄膜在可见光波段的吸收光谱。用6 MV光子束和300 cGy的总剂量照射膜。在照射后24小时在不同旋转角度下拍摄吸收光谱，并且我们使用洛伦兹函数拟合光谱。在约586 nm（绿色）和634 nm（红色）处有两个主要吸收峰。测量的光谱分解为542 nm、558 nm、578 nm、586 nm、626 nm、634 nm和641 nm。红带吸收光谱的最大总面积在45°（225°），最小在90°（270°）。随着旋转角度的变化，蓝色和绿色峰的强度和积分面积也随着180°周期而变化，最小值在90°和270°，最大值在0°和180°，尽管总体吸光度非常低。对于所有角度，光谱峰值波长在2.4nm内保持恒定。薄膜的吸收光谱没有滞后现象;在0°和360°下拍摄的光谱基本相同，并且对于所有旋转角显示出相似的行为。吸光度随薄膜旋转角度的变化影响了薄膜的剂量学特性，导致了在红-绿-蓝各通道中薄膜剂量学的旋转变化。
英文摘要：
It is important to study absorption spectrum in film dosimetry because the spectral absorbance of the film relates to the film's total absorption dose. We investigated the absorption spectra of Gafchromic EBT2 film with various rotational angles in a visible wavelength band. The film was irradiated with 6 MV photon beams and a total dose of 300 cGy. Absorption spectra were taken under different rotational angles after 24 h after irradiation and we fitted the spectra using Lorentzian functions. There were two dominant absorption peaks at approximately 586 nm (green) and 634 nm (red). The measured spectrum was decomposed 542 nm, 558 nm, 578 nm, 586 nm, 626 nm, 634 nm, and 641 nm. The maximum total area of the red band absorption spectrum was at 45°(225°) and the minimum at 90°(270°). As the angle of rotation changed, the intensity and integrated area of the blue and green peaks also changed with 180° period, with minima at 90° and 270°, and maxima at 0° and 180°, although the overall absorbance is very low. The spectral peak wavelengths remained constant within 2.4 nm for all angles. There was no hysteresis of absorption spectrum of the film; spectra taken at 0° and 360°were substantially the same and showed similar behavior for all rotational angles. The change of absorbance with rotational angle of the film affected the dosimetric properties, resulting in rotationalvariations of film dosimetry in each red-green-blue channel.
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