Department of Radiology, Massachusetts General Hospital, 25 New Chardon St, Suite 400B, Boston, MA 02114, USA.
Radiology. 2010 Nov;257(2):373-83. doi: 10.1148/radiol.10092212. Epub 2010 Sep 9.
To compare image quality and lesion conspicuity on abdominal computed tomographic (CT) images acquired with different x-ray tube current-time products (50-200 mAs) and reconstructed with adaptive statistical iterative reconstruction (ASIR) and filtered back projection (FBP) techniques.
Twenty-two patients (mean age, 60.1 years ± 7.3 [standard deviation]; age range, 52.8-67.4 years; mean weight, 78.9 kg ± 18.3; 12 men, 10 women) gave informed consent for this prospective institutional review board-approved and HIPAA-compliant study, which involved the acquisition of four additional image series at multidetector CT. Images were acquired at different tube current-time products (200, 150, 100, and 50 mAs) and encompassed an abdominal lesion over a 10-cm scan length. Images were reconstructed separately with FBP and with three levels of ASIR-FBP blending. Two radiologists reviewed FBP and ASIR images for image quality in a blinded and randomized manner. Volume CT dose index (CTDI(vol)), dose-length product, patient weight, objective noise, and CT numbers were recorded. Data were analyzed by using analysis of variance and the Wilcoxon signed rank test.
CTDI(vol) values were 16.8, 12.6, 8.4, and 4.2 mGy for 200, 150, 100, and 50 mAs, respectively (P < .001). Subjective noise was graded as below average at 150 mAs and average at 100 and 50 mAs for ASIR images, as compared with FBP images, on which noise was graded as average at 150 mAs, above average at 100 mAs, and unacceptable at 50 mAs. A substantial blotchy image appearance was noted in four of 22 image series acquired at 4.2 mGy with 70% ASIR. Lesion conspicuity was significantly better at 4.2 mGy on ASIR than on FBP images (observed P < .044), and overall diagnostic confidence changed from unacceptable on FBP to acceptable on ASIR images.
ASIR lowers noise and improves diagnostic confidence in and conspicuity of subtle abdominal lesions at 8.4 mGy when images are reconstructed with 30% ASIR blending and at 4.2 mGy in patients weighing 90 kg or less when images are reconstructed with 50% or 70% ASIR blending.
比较不同管电流-时间乘积（50-200 mAs）采集并采用自适应统计迭代重建（ASIR）和滤波反投影（FBP）技术重建的腹部 CT 图像的图像质量和病灶显示。
22 名患者（平均年龄 60.1 岁±7.3[标准差]；年龄范围 52.8-67.4 岁；平均体重 78.9 kg±18.3；12 名男性，10 名女性）自愿参与了这项前瞻性机构审查委员会批准和符合 HIPAA 规定的研究，该研究涉及在多排 CT 上额外采集四个图像序列。在不同的管电流-时间乘积（200、150、100 和 50 mAs）下采集图像，并涵盖 10cm 扫描长度的腹部病变。图像分别用 FBP 和三种 ASIR-FBP 混合水平进行重建。两名放射科医生以盲法和随机的方式对 FBP 和 ASIR 图像的图像质量进行了评估。记录容积 CT 剂量指数（CTDI（vol））、剂量长度乘积、患者体重、客观噪声和 CT 值。采用方差分析和 Wilcoxon 符号秩检验进行数据分析。
200、150、100 和 50 mAs 时的 CTDI（vol）值分别为 16.8、12.6、8.4 和 4.2 mGy（P<0.001）。与 FBP 图像相比，ASIR 图像的噪声在 150 mAs 时被评为低于平均水平，在 100 和 50 mAs 时被评为平均水平，而 FBP 图像在 150 mAs 时被评为平均水平，在 100 mAs 时被评为高于平均水平，在 50 mAs 时被评为不可接受水平。在 22 个图像序列中有 4 个在 4.2 mGy 时以 70%的 ASIR 采集，出现了明显的块状图像外观。在 4.2 mGy 时，ASIR 图像的病灶显示明显优于 FBP 图像（观察 P<0.044），整体诊断信心从 FBP 图像的不可接受变为 ASIR 图像的可接受。
当以 30%的 ASIR 混合重建图像时，在 8.4 mGy 时，ASIR 可降低噪声并提高腹部细微病变的诊断信心和显示；当以 50%或 70%的 ASIR 混合重建图像时，在体重 90kg 或以下的患者中，4.2 mGy 时可降低噪声并提高诊断信心和显示。
