Institut de Génie Biomédical, Université de Montréal, Montréal, Québec H3C 3J7, Canada.
Med Phys. 2011 Sep;38(9):5119-29. doi: 10.1118/1.3622607.
The authors applied 2D reference dosimetry protocol for dose measurements using XR-QA radiochromic film model during diagnostic computed tomography (CT) examinations carried out on patients and humanoid Rando phantom.
Response of XR-QA model GAFCHROMIC™ film reference dosimetry system was calibrated in terms of Air-Kerma in air. Four most commonly used CT protocols were selected on their CT scanner (GE Lightspeed VCT 64), covering three anatomical sites (head, chest, and abdomen). For each protocol, 25 patients ongoing planned diagnostic CT examination were recruited. Surface dose was measured using four or eight film strips taped on patients' skin and on Rando phantom. Film pieces were scanned prior to and after irradiation using Epson Expression™ 10000XL document scanner. Optical reflectance of the unexposed film piece was subtracted from exposed one to obtain final net reflectance change, which is subsequently converted to dose using previously established calibration curves.
The authors' measurements show that body skin dose variation has a sinusoidal pattern along the scanning axis due to the helical movement of the x-ray tube, and a comb pattern for head dose measurements due to its axial movement. Results show that the mean skin dose at anterior position for patients is (51 ± 6) mGy, (29 ± 11) mGy, (45 ± 13) mGy and (38 ± 20) mGy for head, abdomen, angio Abdomen, and chest and abdomen protocol (UP position), respectively. The obtained experimental dose length products (DLP) show higher values than CT based DLP taken from the scanner console for body protocols, but lower values for the head protocol. Internal dose measurements inside the phantom's head indicate nonuniformity of dose distribution within scanned volume.
In this work, the authors applied an Air-Kerma in air based radiochromic film reference dosimetry protocol for in vivo skin dose measurements. In this work, they employed green channel extracted from the scanned RGB image for dose measurements in the range from 0 to 200 mGy. Measured skin doses and corresponding DLPs were higher than DLPs provided by the CT scanner manufacturer as they were measured on patients' skin.
作者应用二维参考剂量协议，使用 XR-QA 射线照相胶片模型在患者和人体模型 Rando 进行的诊断计算机断层扫描（CT）检查中进行剂量测量。
在空气比释动能的基础上，对 XR-QA 模型 GAFCHROMIC™胶片参考剂量系统的响应进行校准。在 CT 扫描仪（GE Lightspeed VCT 64）上选择了四种最常用的 CT 协议，涵盖了三个解剖部位（头部、胸部和腹部）。对于每个协议，招募了正在进行计划诊断 CT 检查的 25 名患者。使用贴在患者皮肤上和 Rando 人体模型上的四个或八个胶片条测量表面剂量。在照射前后，使用 Epson Expression™10000XL 文档扫描仪扫描胶片。从曝光后的胶片中减去未曝光的胶片的光反射率，以获得最终的净反射率变化，然后使用先前建立的校准曲线将其转换为剂量。
作者的测量结果表明，由于 X 射线管的螺旋运动，身体皮肤剂量的变化沿扫描轴呈正弦模式，而头部剂量的测量呈梳状模式，这是由于其轴向运动所致。结果表明，对于头部、腹部、血管腹部和胸部和腹部协议（UP 位置）的患者，前位皮肤平均剂量分别为（51±6）mGy、（29±11）mGy、（45±13）mGy 和（38±20）mGy。获得的实验剂量长度乘积（DLP）显示，对于体部方案，与从扫描仪控制台获得的基于 CT 的 DLP 相比，值较高，但对于头部方案，值较低。在人体模型头部内部的剂量测量表明，在扫描体积内的剂量分布不均匀。
在这项工作中，作者应用了基于空气比释动能的放射色胶片参考剂量协议，用于体内皮肤剂量测量。在这项工作中，他们使用从扫描的 RGB 图像中提取的绿色通道来测量 0 至 200 mGy 范围内的剂量。测量的皮肤剂量和相应的 DLP 高于 CT 扫描仪制造商提供的 DLP，因为它们是在患者的皮肤上测量的。
