Aoyama Hideki, Azuma Yoshiharu, Goto Sachiko, Tahara Seiji, Uno Hirofumi, Inamura Keiji, Kadohisa Shigefumi, Nakagiri Yoshitada, Kanazawa Susumu, Sumimoto Tetsuhiro, Azuma Masami
Central Division of Radiology, Okayama University Hospital.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2004 Nov;60(11):1533-42. doi: 10.6009/jjrt.kj00003326577.
Radiochromic film (RC-film) is of great interest as a film-type dosimeter for radiation oncology applications. We present a two-dimensional image-based evaluation of the measurement accuracy of a commercial RC-film product (Gafchromic MD-55-2 film, ISP TECHNOLOGIES, Inc.) by using a commercial Laser Densitometer (Model 1710, Computerized Medical Systems, Inc.) as an optical density imaging system. The coefficient of variation of the density (pixel-value) in one sample was approximately 3% to 11% at 3 Gy or less, and 3% or less at 4 to 60 Gy. Although the coefficient of variation between three samples at the same dose was about 14% at 1 Gy, it decreased as the dose increased, reaching several percent. In 1 to 6 Gy samples, geometric imaging artifacts [interference (moire) patterns] were observed, and it was found that scan-sampling pitch influenced the accuracy of measurement of the density of the sample. To improve the accuracy of density measurement, sufficient knowledge about characteristic features of the density measuring system is essential.
放射变色胶片（RC 胶片）作为一种用于放射肿瘤学应用的胶片型剂量计，备受关注。我们通过使用商用激光密度计（型号 1710，计算机化医疗系统公司）作为光密度成像系统，对一种商用 RC 胶片产品（Gafchromic MD - 55 - 2 胶片，ISP 技术公司）的测量精度进行了基于二维图像的评估。在 3 Gy 及以下时，一个样本中密度（像素值）的变异系数约为 3%至 11%，在 4 至 60 Gy 时为 3%及以下。尽管在相同剂量下三个样本之间的变异系数在 1 Gy 时约为 14%，但随着剂量增加而降低，降至百分之几。在 1 至 6 Gy 的样本中，观察到几何成像伪影[干涉（莫尔）条纹]，并且发现扫描采样间距会影响样本密度测量的准确性。为提高密度测量的准确性，充分了解密度测量系统的特征至关重要。
