等渗低浓度对比剂联合能谱CT在优化颈动脉CTA成像中的应用研究

Clinical application of energy monochromatic CT angiography combined with ASiR in carotid artery under isotonic and low concentration isotoniccontrast agent

目的评价等渗低浓度对比剂下能谱单能量联合自适应统计迭代重建(ASiR)算法在优化颈动脉能谱单能量CTA成像中的应用价值,以寻求等渗低浓度对比剂下图像质量最佳的单能量和ASiR比组合,优化颈部血管显示。方法共30例使用等渗低浓度对比剂并经能谱颈动脉CTA扫描的患者入组。一次能谱成像获得11组单能量图像(40~140 keV,间隔10 keV),同时每一组单能量图像分别进行不同ASiR比例(0%,20%,40%,60%,80%和100%)重组。分别对各组单能量图像进行感兴趣区域的SNR值、CNR值及噪声值测定,并由两位高年资影像诊断医生依据血管清晰度行4分法盲法评分。结果 60 keV时CNR和SNR值最高;噪声值随着ASiR比例升高而下降,ASiR 100%时噪声降至最低;图像质量主观评分显示60 keV联合ASiR 60%重建时的评分最高;最后,综合主观及客观评价指标,确定60 keV+ASiR 60%重建参数组合时颈动脉CTA图像质量最佳。结论应用等渗低浓度对比剂行颈动脉能谱CTA扫描,60 keV单能量图像联合ASiR 60%重建时可以明显降低噪声,提高图像质量,最优化显示颈部血管。

Objective To determine the optimal combination of monochromatic energy and adaptive statistical iterative reconstruction(ASiR)for carotid CT angiography(CTA)with spectral CT imaging under the isotonic and low concentration isotoniccontrast agent.Methods 60 patients(38 males and 22 females)underwent carotid CTA using isotonic and low concentration isotoniccontrast agent were enrolled in this study.Monochromatic images from 40 to 140 keV(in 10~keV increments)were reconstructed with six ASiR percentages:0%,20%,40%,60%,80%,and 100%.In all sets of monochromatic images,signal-to-noise ratios(SNR),contrast-to-noise ratio(CNR)and imagenoise within the regions of interest were measured by two experienced radiologists blinded to the to clinical and pathological data.A 4-point scale was used to assess the image quality subjectively.Results The optimal SNR and CNR for carotid CTA was achieved at 60 keV.The image noise decreased with the increase of the ratio of keV and ASiR,and the linear downward trend between 40 and 60 keV was the most obvious,and the noise was the lowest when ASiR was 100%.In 66 monochromatic images sets,the optimal image quality was obtained in the 60 keV+60%ASiR.Conclusion Combined use of monochromatic imaging and ASiR can decrease the image noise and improved the image quality in CTA of cartoid.The optimal energy level and ASiR for carotid CTA was 60 keV and 60%,respectively.