Advanced Cardiovascular Imaging Laboratory, Cardiovascular and Pulmonary Branch, National Heart Lung and Blood Institute, National Institutes of Health, Department of Health and Human Services, 10 Center Dr, Building 10, Room B1D416, Bethesda, MD 20892-1061, USA.
Radiology. 2013 Apr;267(1):76-85. doi: 10.1148/radiol.13122621. Epub 2013 Jan 22.
To (a) use a new second-generation wide-volume 320-detector row computed tomographic (CT) scanner to explore optimization of radiation exposure in coronary CT angiography in an unselected and consecutive cohort of patients referred for clinical purposes and (b) compare estimated radiation exposure and image quality with that from a cohort of similar patients who underwent imaging with a previous first-generation CT system.
The study was approved by the institutional review board, and all subjects provided written consent. Coronary CT angiography was performed in 107 consecutive patients with a new second-generation 320-detector row unit. Estimated radiation exposure and image quality were compared with those from 100 consecutive patients who underwent imaging with a previous first-generation scanner. Effective radiation dose was estimated by multiplying the dose-length product by an effective dose conversion factor of 0.014 mSv/mGy ⋅ cm and reported with size-specific dose estimates (SSDEs). Image quality was evaluated by two independent readers.
The mean age of the 107 patients was 55.4 years ± 12.0 (standard deviation); 57 patients (53.3%) were men. The median body mass index was 27.3 kg/m(2) (range, 18.1-47.2 kg/m(2)); however, 71 patients (66.4%) were overweight, obese, or morbidly obese. A tube potential of 100 kV was used in 97 patients (90.6%), single-volume acquisition was used in 104 (97.2%), and prospective electrocardiographic gating was used in 106 (99.1%). The mean heart rate was 57.1 beats per minute ± 11.2 (range, 34-96 beats per minute), which enabled single-heartbeat scans in 100 patients (93.4%). The median radiation dose was 0.93 mSv (interquartile range [IQR], 0.58-1.74 mSv) with the second-generation unit and 2.67 mSv (IQR, 1.68-4.00 mSv) with the first-generation unit (P < .0001). The median SSDE was 6.0 mGy (IQR, 4.1-10.0 mGy) with the second-generation unit and 13.2 mGy (IQR, 10.2-18.6 mGy) with the first-generation unit (P < .0001). Overall, the radiation dose was less than 0.5 mSv for 23 of the 107 CT angiography examinations (21.5%), less than 1 mSv for 58 (54.2%), and less than 4 mSv for 103 (96.3%). All studies were of diagnostic quality, with most having excellent image quality. Three of four image quality indexes were significantly better with the second-generation unit compared with the first-generation unit.
The combination of a gantry rotation time of 275 msec, wide volume coverage, iterative reconstruction, automated exposure control, and larger x-ray power generator of the second-generation CT scanner provides excellent image quality over a wide range of body sizes and heart rates at low radiation doses.
http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13122621/-/DC1.
（a）使用新型第二代宽容积 320 排探测器 CT 扫描仪，在未经选择且连续的临床就诊患者队列中探索冠状动脉 CT 血管造影中辐射暴露的优化，以及（b）比较来自接受类似成像患者队列的估计辐射暴露和图像质量，这些患者使用第一代 CT 系统进行了成像。
本研究获得了机构审查委员会的批准，所有受试者均提供了书面同意书。对 107 例连续患者使用新型第二代 320 排 CT 机进行了冠状动脉 CT 血管造影。比较了与 100 例使用第一代扫描仪进行成像的连续患者的估计辐射暴露和图像质量。有效剂量通过将剂量长度乘积乘以有效剂量转换系数 0.014 mSv/mGy ⋅ cm 来估算，并通过大小特异性剂量估计（SSDE）进行报告。由两位独立的读者评估图像质量。
107 例患者的平均年龄为 55.4 岁±12.0（标准差）；57 例（53.3%）为男性。中位体重指数为 27.3 kg/m2（范围，18.1-47.2 kg/m2）；然而，71 例（66.4%）超重、肥胖或病态肥胖。97 例（90.6%）患者使用 100 kV 管电压，104 例（97.2%）使用单次容积采集，106 例（99.1%）使用前瞻性心电图门控。平均心率为 57.1 次/分钟±11.2（范围，34-96 次/分钟），100 例（93.4%）患者可进行单次心跳扫描。第二代单位的中位数辐射剂量为 0.93 mSv（四分位间距 [IQR]，0.58-1.74 mSv），第一代单位为 2.67 mSv（IQR，1.68-4.00 mSv）（P<.0001）。第二代单位的中位数 SSDE 为 6.0 mGy（IQR，4.1-10.0 mGy），第一代单位为 13.2 mGy（IQR，10.2-18.6 mGy）（P<.0001）。总体而言，23 次 CT 血管造影检查（21.5%）的辐射剂量小于 0.5 mSv，58 次（54.2%）小于 1 mSv，103 次（96.3%）小于 4 mSv。所有研究均具有诊断质量，大多数研究具有极好的图像质量。与第一代设备相比，第二代设备的四个图像质量指标中的三个有显著改善。
第二代 CT 扫描仪的机架旋转时间为 275 msec、宽容积覆盖、迭代重建、自动曝光控制和更大的 X 射线功率发生器的组合，在广泛的体型和心率范围内以低辐射剂量提供出色的图像质量。
http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13122621/-/DC1.
