Department of Imaging Physics, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
AJR Am J Roentgenol. 2010 Jun;194(6):1539-46. doi: 10.2214/AJR.09.3268.
The National Lung Screening Trial includes 33 participating institutions that performed 75,133 lung cancer screening CT examinations for 26,724 subjects during 2002-2007. For trial quality assurance reasons, CT radiation dose measurement data were collected from all MDCT scanners used in the trial.
A total of 247 measurements on 96 MDCT scanners were collected using a standard CT dose index (CTDI) measurement protocol. The scan parameters used in the measurements (tube voltage, milliampere-seconds [mAs], and detector-channel configuration) were set according to trial protocol for average size subjects. The normalized weighted CT dose index (CTDI(w)) (computed as CTDI(w)/mAs) obtained from each trial-participating scanner was tabulated.
We found a statistically significant difference in normalized CT dose index among CT scanner manufacturers, likely as a result of design differences, such as filtration, bow-tie design, and geometry. Our findings also indicated a statistically significant difference in normalized CT dose index among CT scanner models from the same manufacturer (e.g., GE Healthcare, Siemens Healthcare, and Philips Healthcare). We also found a statistically significant difference in normalized CT dose index among all models and all manufacturers; furthermore, we found a statistically significant difference in normalized CT dose index among CT scanners from all manufacturers when we compared scanners with four or eight data channels to those with 16, 32, or 64 channels, suggesting that more complex scanners have improved dose efficiency.
Average normalized CT dose index values varied by a factor of almost two for all scanners from all manufacturers. This study was focused on machine-specific normalized CT dose index; patient dose and image quality were not addressed.
国家肺癌筛查试验（National Lung Screening Trial）包括 33 个参与机构，在 2002 年至 2007 年间对 26724 名受试者进行了 75133 次肺癌筛查 CT 检查。出于试验质量保证的原因，从试验中使用的所有 MDCT 扫描仪收集了 CT 辐射剂量测量数据。
使用标准 CT 剂量指数（CTDI）测量协议共对 96 台 MDCT 扫描仪进行了 247 次测量。在测量中使用的扫描参数（管电压、毫安秒 [mAs]和探测器通道配置）根据试验方案设置为平均大小的受试者。从每个参与试验的扫描仪获得的归一化加权 CT 剂量指数（CTDI(w))（通过 CTDI(w)/mAs 计算）被制表。
我们发现 CT 扫描仪制造商之间的归一化 CT 剂量指数存在统计学上的显著差异，这可能是由于设计差异所致，例如过滤、蝴蝶结设计和几何形状。我们的研究结果还表明，同一制造商的 CT 扫描仪型号之间的归一化 CT 剂量指数存在统计学上的显著差异（例如，通用电气医疗保健公司、西门子医疗保健公司和飞利浦医疗保健公司）。我们还发现所有制造商的所有型号之间的归一化 CT 剂量指数存在统计学上的显著差异；此外，当我们将具有四或八个数据通道的 CT 扫描仪与具有 16、32 或 64 个通道的扫描仪进行比较时，我们发现所有制造商的 CT 扫描仪之间的归一化 CT 剂量指数存在统计学上的显著差异，这表明更复杂的扫描仪具有更高的剂量效率。
所有制造商的所有扫描仪的平均归一化 CT 剂量指数值相差近两倍。本研究侧重于特定于机器的归一化 CT 剂量指数；未涉及患者剂量和图像质量。
