目的:未增强的腹部CT构成可疑尿石症的诊断标准。为了确定在这种频繁的成像任务中降低辐射剂量的潜力,本实验研究比较了光谱整形和管电压调制对图像质量的影响。
方法:使用第三代双源CT,在三种剂量水平(3mGy:标准;1mGy:低;0.5mGy:超低)下,使用不同的管电压设置和不使用锡过滤器(Sn150,Sn100,120,100和80kVp)扫描8个尸体标本。通过计算各种组织(脾脏,肾,骨小梁,脂肪),并由三位独立的放射科医师根据7分评定量表(7=优秀;1=非常差)主观。
结果:不考虑剂量水平,Sn100kVp导致所有管电压设置中的最高SNR。与Sn150kVp直接比较,确定脾脏(p≤0.004)和肾脏组织(p≤0.009)的SNR较好.在超低剂量扫描中,与120kVp(2;2-2)的常规成像相比,Sn100kVp的主观图像质量(中值评分3;四分位距3-3)更高,100kVp(1;1-2),和80kVp(1;1-1)(所有p<0.001)。由0.945的组内相关系数表示(95%置信区间:0.927-0.960),评分者间的可靠性非常好。
结论:在最大剂量减少的腹部CT中,在100kVp的锡预过滤允许优于Sn150kVp的图像质量和没有光谱整形的常规成像。
OBJECTIVE: Unenhanced abdominal CT constitutes the diagnostic standard of care in suspected urolithiasis. Aiming to identify potential for radiation dose reduction in this frequent imaging task, this experimental study compares the effect of spectral shaping and tube voltage modulation on image quality.
METHODS: Using a third-generation dual-source CT, eight cadaveric specimens were scanned with varying tube voltage settings with and without tin filter application (Sn 150, Sn 100, 120, 100, and 80 kVp) at three dose levels (3 mGy: standard; 1 mGy: low; 0.5 mGy: ultralow). Image quality was assessed quantitatively by calculation of signal-to-noise ratios (SNR) for various tissues (spleen, kidney, trabecular bone, fat) and subjectively by three independent radiologists based on a seven-point rating scale (7 = excellent; 1 = very poor).
RESULTS: Irrespective of dose level, Sn 100 kVp resulted in the highest SNR of all tube voltage settings. In direct comparison to Sn 150 kVp, superior SNR was ascertained for spleen (p ≤ 0.004) and kidney tissue (p ≤ 0.009). In ultralow-dose scans, subjective image quality of Sn 100 kVp (median score 3; interquartile range 3-3) was higher compared with conventional imaging at 120 kVp (2; 2-2), 100 kVp (1; 1-2), and 80 kVp (1; 1-1) (all p < 0.001). Indicated by an intraclass correlation coefficient of 0.945 (95% confidence interval: 0.927-0.960), interrater reliability was excellent.
CONCLUSIONS: In abdominal CT with maximised dose reduction, tin prefiltration at 100 kVp allows for superior image quality over Sn 150 kVp and conventional imaging without spectral shaping.