Mueck F G, Michael L, Deak Z, Scherr M K, Maxien D, Geyer L L, Reiser M, Wirth S
Institut für klinische Radiologie, Ludwig-Maximilian-University München, Nussbaumstraße 20, 80336 München, Germany.
Rofo. 2013 Jul;185(7):644-54. doi: 10.1055/s-0033-1335152. Epub 2013 May 21.
To compare the image quality in dose-reduced 64-row CT of the chest at different levels of adaptive statistical iterative reconstruction (ASIR) to full-dose baseline examinations reconstructed solely with filtered back projection (FBP) in a realistic upgrade scenario.
A waiver of consent was granted by the institutional review board (IRB). The noise index (NI) relates to the standard deviation of Hounsfield units in a water phantom. Baseline exams of the chest (NI = 29; LightSpeed VCT XT, GE Healthcare) were intra-individually compared to follow-up studies on a CT with ASIR after system upgrade (NI = 45; Discovery HD750, GE Healthcare), n = 46. Images were calculated in slice and volume mode with ASIR levels of 0 - 100 % in the standard and lung kernel. Three radiologists independently compared the image quality to the corresponding full-dose baseline examinations (-2: diagnostically inferior, -1: inferior, 0: equal, + 1: superior, + 2: diagnostically superior). Statistical analysis used Wilcoxon's test, Mann-Whitney U test and the intraclass correlation coefficient (ICC).
The mean CTDIvol decreased by 53 % from the FBP baseline to 8.0 ± 2.3 mGy for ASIR follow-ups; p < 0.001. The ICC was 0.70. Regarding the standard kernel, the image quality in dose-reduced studies was comparable to the baseline at ASIR 70 % in volume mode (-0.07 ± 0.29, p = 0.29). Concerning the lung kernel, every ASIR level outperformed the baseline image quality (p < 0.001), with ASIR 30 % rated best (slice: 0.70 ± 0.6, volume: 0.74 ± 0.61).
Vendors' recommendation of 50 % ASIR is fair. In detail, the ASIR 70 % in volume mode for the standard kernel and ASIR 30 % for the lung kernel performed best, allowing for a dose reduction of approximately 50 %.
在实际升级场景中，比较不同自适应统计迭代重建（ASIR）水平下胸部64排CT剂量降低后的图像质量与仅用滤波反投影（FBP）重建的全剂量基线检查的图像质量。
机构审查委员会（IRB）批准豁免知情同意。噪声指数（NI）与水模中亨氏单位的标准差相关。对胸部基线检查（NI = 29；GE医疗的LightSpeed VCT XT）与系统升级后使用ASIR的CT随访研究（NI = 45；GE医疗的Discovery HD750）进行个体内比较，n = 46。在标准内核和肺内核中，使用0 - 100%的ASIR水平以切片和容积模式计算图像。三名放射科医生独立将图像质量与相应的全剂量基线检查进行比较（-2：诊断性较差，-1：较差，0：相等，+1：较好，+2：诊断性较好）。统计分析采用威尔科克森检验、曼 - 惠特尼U检验和组内相关系数（ICC）。
平均容积CT剂量指数（CTDIvol）从FBP基线降低53%，ASIR随访时为8.0±2.3 mGy；p < 0.001。ICC为0.70。关于标准内核，在容积模式下，ASIR 70%时剂量降低研究中的图像质量与基线相当（-0.07±0.29，p = 0.29）。关于肺内核，每个ASIR水平的图像质量均优于基线（p < 0.001），ASIR 30%时评价最佳（切片：0.70±0.6，容积：0.74±0.61）。
供应商推荐的50% ASIR是合理的。具体而言，标准内核在容积模式下ASIR 70%以及肺内核ASIR 30%时表现最佳，可实现约50%的剂量降低。
