The calibration of experimental self-developing Gafchromic® HXR film for the measurement of radiation dose in computed tomography
The calibration of experimental self-developing Gafchromic® HXR film for the measurement of radiation dose in computed tomography
复制标题
DOI：
10.1118/1.1862802
复制
发表时间：
2005-04-01
期刊：
影响因子：
3.8
通讯作者：
McCollough, CH
中科院分区：
文献类型：
--
作者：
Gorny, KR;Leitzen, SL;McCollough, CH
自行开发的原型Gafchromic（R）HXR胶片的灵敏度比用于介入放射应用的市售Gafchromic XR胶片高一个数量级。HXR胶片的较高灵敏度允许在低于10 R（87.7 mGy）的曝光水平的诊断范围内采集高分辨率校准剂量曲线。我们采用市售的光学平板扫描仪对胶片进行数字化，并使用图像分析软件确定HXR胶片对电离辐射的响应。确定了平板扫描仪的空间均匀性和时间重复性，并用于优化数字化方案。使用两个同时曝光的片材的多次扫描来确定HXR膜的曝光后密度增长和对环境光的灵敏度，其中一个片材储存在不透光条件下，另一个片材用白色光连续照射。通过使用射线照相X射线管同时照射胶片条的一部分和校准的电离室来获得HXR胶片的校准的阶梯楔，所述射线照相X射线管具有与典型的CT扫描仪（8mm Al HVL，120kVp）匹配的射束特性。校准胶片的重复数字化用于确定胶片响应测量的精度。的精度，作为衡量的标准偏差的多次测量，优于1%，在整个动态范围内的薄膜响应。使用0.5至12 R（4.4至105.3 mGy）范围内的暴露量测量该精度。该曝光范围与X射线计算机断层扫描高度相关。初步的辐射剂量分布证明了这种技术的实用性。(c)2005年美国医学物理学家协会。
A prototype, self-developing Gafchromic (R) HXR film has sensitivity an order of magnitude larger than that of the commercially available Gafchromic XR film used in interventional radiological applications. The higher sensitivity of the HXR film allows the possibility of acquisition of high-resolution calibrated dose profiles within the diagnostic range of exposure levels, below 10 R (87.7 mGy). We employed a commercially available, optical flatbed scanner for digitization of the film and image analysis software to determine the response of the HXR films to ionizing radiation. Spatial uniformity and temporal repeatability of the flatbed scanner were determined and used in optimization of the digitization protocol. The HXR film postexposure density growth and sensitivity to ambient light were determined using multiple scans of two simultaneously exposed sheets, one stored in light-tight conditions and the other continuously illuminated with white light. A calibrated step wedge of the HXR film was obtained by simultaneous irradiation of a portion of a film strip and a calibrated ionization chamber using a radiographic x-ray tube with beam characteristics matched to a typical CT scanner (8 mm Al HVL, 120 kVp). Repeated digitization of the calibration film was used to determine the precision of the film response measurements. The precision, as measured by the standard deviation of multiple measurements, was better than 1% over the full dynamic range of film response. This precision was measured using exposures ranging from 0.5 to 12 R (4.4 to 105.3 mGy). This exposure range is highly relevant to x-ray computed tomography. Preliminary radiation dose profiles demonstrate the utility of this technique. (c) 2005 American Association of Physicists in Medicine.