能谱CT结合ASIR和低浓度对比剂腹部动脉成像质量及辐射剂量研究

Spectral CT with ASiR in low radiation and contrast medium dose in abdominal artery imaging

目的与常规CT血管成像对比,评价能谱CT结合自适应迭代统计(ASIR)技术和低浓度对比剂在腹部动脉成像质量及辐射剂量。方法将61例行腹部CTA检查的患者随机分成A、B两组。A组:31例,进行能谱CTA扫描,螺距1.375,运用能谱(GSI)扫描,结合50%ASIR重建优化血管成像。B组:30例,进行常规CTA扫描(120k Vp),噪声指数12,螺距1.375。A组用270碘克沙醇对比剂(浓度270mgl/ml),B组用350碘普罗胺对比剂(浓度350mgl/ml),两组对比剂总量都为1ml/kg,注射速度为5ml/s。兴趣区分别放在腹腔干水平的腹主动脉和左侧深层椎旁肌。测量A、B两组腹主动脉CT值及图像噪声,计算出血管信噪比和对比噪声比。利用统计学比较这两组的辐射计量,对比剂计量和反映图像质量的信噪比和对比噪声比等。结果两组BMI值没有差异性(P>0.05),A组DLP是(245.59±32.96)m Gy.cm,B组是(380.42±104.54)m Gy.cm,两组具有差异性(P<0.05)。辐射计量和对比剂剂量在A组分别降低了35.4%和22.9%。A组图像的腹主动脉的信号强度显著高于B组(432.0±74.8)HU vs(340.7±65.3)HU,(P<0.05)。A组图像腹主动脉的对比噪声比和信噪比也是显著高于B组(分别是40.63±2.75 vs.30.45±1.94和48.76±3.23 vs.38.75±2.52,P<0.05)。结论与常规CTA模式相比,运用低浓度对比剂结合50%ASIR能谱模式的腹部CTA提供良好的血管成像同时显著的降低辐射计量和对比剂剂量。

Objective To evaluate image quality and dose performance of spectral CT with adaptive statistical iterative reconstruction（ ASiR） in low radiation and contrast medium dose abdominal artery imaging in comparison with a standard 120 k Vp scan protocol. Methods 31 patients（ group A） referred to abdominal CT angiography（ CTA） underwent spectral CTA with pitch of1. 375 and GSI assist technique and 50% ASiR to optimize dose performance. Another 30 patients（ group B） underwent standard120 k Vp CTA with Noise Index of 12,pitch of 1. 375. Group A used Iodixanol 270（ concentration 270 mg I/ml） while group B used Iopromide 350（ concentration 350 mg I/ml） contrast medium,both with total volume of 1 ml/kg and injection rate of 5 ml/s. Spectral CT images at 60 ke V were used for comparison. Regions-of-interest（ ROIs） were placed in abdominal aorta and muscle to measure CT number and image noise（ SD）. Signal-to-noise ratio（ SNR） and contrast-to-noise ratio（ CNR） of vessels were calculated. Radiation dose,contrast medium dose and quantitative measurements reflecting image quality for the two groups were statistically compared. Results BMI was comparable between two groups（ P〈0. 05）. DLP was（ 245. 59 ± 32. 96） m Gy. cm for the spectral CT group and（ 380. 42 ± 104. 54） m Gy. cm for 120 k Vp group（ P〈0. 05）. Radiation dose and contrast medium dose in the low dose spectral CTA group was reduced by 35. 4% and 22. 9%,respectively. Signal intensity of the abdominal aorta was significantly higher in the spectral image at 60 ke V than those of 120 k Vp（ 432. 0 ± 74. 8） HU vs.（ 340. 7 ± 65. 3） HU（ P〈0. 05）. The CNR and SNR values of aorta were also significantly higher than those of 120 k Vp（ 40. 63 ± 2. 75 vs. 30. 45 ±1. 94 and 48. 76 ± 3. 23 vs. 38. 75 ± 2. 52,respectively,all P〈0. 05）. Conclusion Abdominal CTA using spectral imaging mode coupled with 50% ASiR provides excellent vascular images in arterial phase,while,significantly reduces radiation dose and contrast media dose compared with the standard 120 k Vp scans.