Imaging Institute, Cleveland Clinic, OH 44195, USA.
AJR Am J Roentgenol. 2010 Jul;195(1):89-100. doi: 10.2214/ajr.09.3611.
The purpose of our study was to determine whether the MDCT enterography dose can be reduced by changing automatic exposure control (AEC) setting and quality reference milliampere-seconds (mAs) without altering subjective image quality or efficacy in active inflammatory Crohn's disease.
This is a prospective study of 2,310 MDCT enterography procedures performed using 16- and 64-MDCT in three cohorts (original, intermediate, and final dose levels). For 16-MDCT, the original and intermediate dose level quality reference mAs was 200, and weight-based (1 pound [0.45 kg] = 1 mAs) for the final dose level. For 64-MDCT, the original dose level quality reference mAs was 260; the mAs was 220 for intermediate and weight-based for the final dose level. For the intermediate and final dose levels, AEC was changed from strong to weak increase for obese and weak to strong decrease for slim patients. Demographic data and volume CT dose index (CTDI(vol)) were analyzed. Three readers evaluated the cases for image quality and efficacy differentiating normal from active inflammatory Crohn's disease.
For 16-MDCT, CTDI(vol) decreased from 12.82 to 10.14 mGy and 10.14 to 8.7 mGy between original to intermediate and intermediate to final dose levels. For 64-MDCT, the CTDI(vol) decreased from 15.72 to 11.42 mGy and 11.42 to 9.25 mGy between original to intermediate and intermediate to final dose levels. Images were rated suboptimal or nondiagnostic more often in the intermediate dose level (p < 0.05) but not in the final. There was no reduction in diagnostic efficacy as measured by area under the ROC curve (p > 0.1443 except for one comparison with one reader).
Substantial dose reduction can be achieved using weight-based quality reference mAs and altering AEC settings without affecting diagnostic efficacy in active inflammatory Crohn's disease of the terminal ileum. However, subjective image quality can be compromised at these dose settings, depending on radiologist preference.
本研究旨在确定在不改变主观图像质量或对活动性炎症性克罗恩病的疗效的情况下，通过改变自动曝光控制（AEC）设置和质量参考毫安秒（mAs）是否可以降低 MDCT 肠造影的剂量。
这是一项前瞻性研究，共纳入了 2310 例使用 16 层和 64 层 MDCT 进行的 MDCT 肠造影检查，分为三组（原始组、中间组和最终剂量组）。对于 16 层 MDCT，原始组和中间组的质量参考 mAs 为 200，最终剂量组的质量参考 mAs 为体重相关（1 磅[0.45kg]=1mAs）。对于 64 层 MDCT，原始剂量组的质量参考 mAs 为 260；中间剂量组的 mAs 为 220，最终剂量组的 mAs 为体重相关。对于中间和最终剂量组，AEC 从肥胖患者的强增加变为弱减少，从瘦弱患者的弱减少变为强减少。分析了患者的人口统计学数据和容积 CT 剂量指数（CTDI（vol））。三位读者评估了病例的图像质量和区分正常与活动性炎症性克罗恩病的疗效。
对于 16 层 MDCT，CTDI（vol）从原始组到中间组和中间组到最终剂量组分别降低了 12.82 至 10.14mGy 和 10.14 至 8.7mGy。对于 64 层 MDCT，CTDI（vol）从原始组到中间组和中间组到最终剂量组分别降低了 15.72 至 11.42mGy 和 11.42 至 9.25mGy。在中间剂量组，图像被评为次优或不可诊断的频率更高（p<0.05），但在最终剂量组则没有。通过 ROC 曲线下面积（AUC）测量，诊断效能没有降低（除了与一位读者的一次比较外，p>0.1443）。
在不影响活动性炎症性克罗恩病末段回肠的诊断效能的情况下，使用体重相关的质量参考 mAs 和改变 AEC 设置可以实现显著的剂量降低。然而，在这些剂量设置下，主观图像质量可能会受到影响，这取决于放射科医生的偏好。
