1 Department of Radiology, Division of Abdominal Imaging and Intervention, Massachusetts General Hospital, Harvard Medical School, 55 Fruit St, White 270, Boston, MA 02114-2696.
AJR Am J Roentgenol. 2015 May;204(5):1055-63. doi: 10.2214/AJR.14.13038.
The objective of our study was to evaluate three commercially available iterative reconstruction (IR) algorithms-ASiR, iDOSE, and SAFIRE-and conventional filtered back projection (FBP) on image quality and radiation dose in kidney stone CT examinations.
During the 6-month study period, 684 unenhanced kidney stone CT examinations of consecutive adults were performed on 17 CT scanners (GE Healthcare [vendor 1], n = 12 scanners; Philips Healthcare [vendor 2], n = 2; Siemens Health-care [vendor 3], n = 3); these examinations were retrieved using dose-monitoring software (eXposure). A total of 347 kidney stone CT examinations were reconstructed using FBP, and 337 examinations were processed using IR (ASiR, n = 248; iDOSE, n = 50; SAFIRE, n = 39). The standard-dose scanning parameters for FBP scanners included a tube potential of 120 kVp, a tube current of 75-450 mA for vendor 1 and a Quality Reference mAs of 160-180 for vendor 3, and a slice thickness of 2.5 or 5 mm. The dose-modified protocol for the IR scanners included a higher noise index (1.4 times higher than the standard-dose FBP protocol) for vendor 1, a lower reference tube current-exposure time product for vendor 2 (150 reference mAs), and a lower Quality Reference mAs for vendor 3 (120 Quality Reference mAs). Three radiologists independently reviewed 60 randomly sampled kidney stone CT examinations for image quality, noise, and artifacts. Objective noise and attenuation were also determined. Size-specific dose estimates (SSDEs) were compared using ANOVA.
Significantly higher subjective and objective measurements of image noise were found in FBP examinations compared with dose-modified IR examinations (p < 0.05). The radiation dose was substantially lower for the dose-modified IR examinations than the standard-dose FBP examinations (mean SSDE ± SD: 8.1 ± 3.8 vs 11.6 ± 3.6 mGy, respectively) (p < 0.0001), but the radiation dose was comparable among the three IR techniques (ASiR, 7.8 ± 3.1 mGy; iDOSE, 7.5 ± 1.9 mGy; SAFIRE, 7.6 ± 3.2 mGy) (p > 0.05).
The three IRs enable 20-33% radiation dose reduction in kidney stone CT examinations compared with the FBP technique without any image quality concerns. The radiation dose and image quality were comparable among these three IR algorithms.
我们的研究目的是评估三种市售的迭代重建（IR）算法-ASiR、iDOSE 和 SAFIRE-以及传统滤波反投影（FBP）在肾结石 CT 检查中的图像质量和辐射剂量。
在 6 个月的研究期间，对 17 台 CT 扫描仪（通用电气医疗系统[供应商 1]，n = 12 台；飞利浦医疗系统[供应商 2]，n = 2 台；西门子医疗系统[供应商 3]，n = 3 台）上的 684 例成人未增强肾结石 CT 检查进行了检索，这些检查使用剂量监测软件（eXposure）进行检索。共有 347 例肾结石 CT 检查使用 FBP 进行重建，337 例使用 IR（ASiR，n = 248；iDOSE，n = 50；SAFIRE，n = 39）进行处理。FBP 扫描仪的标准剂量扫描参数包括管电压为 120 kVp，管电流为 75-450 mA（供应商 1）和质量参考 mAs 为 160-180（供应商 3），以及层厚为 2.5 或 5 mm。IR 扫描仪的剂量修正方案包括管电流-曝光时间乘积较高（比标准剂量 FBP 方案高 1.4 倍）（供应商 1）、管电流-曝光时间乘积较低（供应商 2 为 150 参考 mAs）和质量参考 mAs 较低（供应商 3 为 120 质量参考 mAs）。三位放射科医生独立对 60 例随机抽取的肾结石 CT 检查进行了图像质量、噪声和伪影的评估。还测定了客观噪声和衰减。使用方差分析比较了大小特异性剂量估计值（SSDE）。
与剂量修正的 IR 检查相比，FBP 检查的主观和客观图像噪声测量值显著更高（p < 0.05）。与标准剂量 FBP 检查相比，剂量修正的 IR 检查的辐射剂量显著降低（平均 SSDE ± SD：8.1 ± 3.8 与 11.6 ± 3.6 mGy，分别）（p < 0.0001），但三种 IR 技术的辐射剂量相当（ASiR，7.8 ± 3.1 mGy；iDOSE，7.5 ± 1.9 mGy；SAFIRE，7.6 ± 3.2 mGy）（p > 0.05）。
与 FBP 技术相比，三种 IR 技术可使肾结石 CT 检查的辐射剂量降低 20-33%，而不会对图像质量产生任何影响。这些三种 IR 算法的辐射剂量和图像质量相当。
