Department of Radiology, Skåne University Hospital, Lund University, Malmö, Södra Förstadsgatan 101, SE-205 02 Malmö, Sweden.
AJR Am J Roentgenol. 2013 Feb;200(2):383-8. doi: 10.2214/AJR.12.8534.
The purpose of this study was to evaluate an abdominal CT protocol in which radiation dose was reduced and i.v. contrast dose increased for young patients and radiation dose was increased and i.v. medium dose decreased for elderly patients. The hypothesis was that these adjustments would result in constant image quality and a reduction in age-specific risk.
Patients were divided into four age groups of 25 patients each: group 1, 16-25 years; group 2, 26-50 years; group 3, 51-75 years; and group 4, older than 75 years. The quality reference tube load ranged from 100 to 300 mAs, and the i.v. contrast dose ranged from 600 to 350 mg I/kg. Group 3 was the reference group. Signal-to-noise and contrast-to-noise ratios for a hypothetical hypovascular liver metastatic lesion were calculated. Subjective image quality was evaluated by visual grading characteristic analysis in which four readers assessed the reproduction of seven image-quality criteria.
Radiation dose was reduced 57% in the youngest group, and the i.v. contrast dose was reduced 18% in elderly patients. There were no statistically significant differences between the groups with respect to signal-to-noise and contrast-to-noise ratios. Subjective image quality was graded significantly lower for four criteria in group 1 compared with group 3. No significant difference was found in comparisons of groups 2 (except for one criterion) and 4 with group 3.
It is possible to balance radiation dose and contrast dose against each other and maintain signal-to-noise and contrast-to-noise ratios. Subjective image quality was affected by increased noise level on the images but was judged acceptable in all groups except the one with the lowest radiation dose.
本研究旨在评估一种腹部 CT 方案，该方案对年轻患者降低辐射剂量并增加静脉对比剂剂量，对老年患者增加辐射剂量并降低静脉中等剂量。假设这些调整将导致图像质量保持不变，并降低特定年龄的风险。
将患者分为四个年龄组，每组 25 例：第 1 组，16-25 岁；第 2 组，26-50 岁；第 3 组，51-75 岁；第 4 组，年龄大于 75 岁。质量参考管电流范围为 100-300mA，静脉对比剂剂量范围为 600-350mgI/kg。第 3 组为参考组。计算假设的乏血管性肝转移瘤的信噪比和对比噪声比。通过视觉分级特征分析评估主观图像质量，其中四位读者评估了七个图像质量标准的再现性。
在最年轻的组中，辐射剂量降低了 57%，而老年患者的静脉对比剂剂量降低了 18%。在信号噪声比和对比噪声比方面，各组之间没有统计学差异。与第 3 组相比，第 1 组的四个标准的主观图像质量评分显著降低。第 2 组（除一个标准外）和第 4 组与第 3 组之间的比较无显著差异。
可以平衡辐射剂量和对比剂量，同时保持信噪比和对比噪声比。由于图像噪声水平增加，主观图像质量受到影响，但在除辐射剂量最低的一组外，所有组都认为可接受。
