80 kVp联合像素闪烁算法在直接法下肢静脉CT血管成像中的应用

Application of pixel shine algorithm at 80 kVp in direct CT venography of the lower extremities

摘要:

目的：评价80kVp联合像素闪烁（pixel shine，PS）算法在直接法下肢静脉CT血管成像的辐射剂量和图像质量。方法：采用直接法下肢静脉CT血管成像，将41例临床诊断为下肢静脉曲张患者随机分为实验组（80 kV）和对照组（100 kV），对照组采用滤波反投影（filtered back projection，FBP）算法重建，实验组采用PS算法重建。比较2种成像技术的容积CT剂量指数（CTDIvol）和剂量面积乘积（DLP）。分别选取腰5锥体层面图像、股骨头层面图像和腘窝层面图像，由2名放射科医师对以上图像的图像质量和噪声做主观评分，并测量、计算静脉血管CT值、图像噪声、信噪比（signal-to-noise ratio，SNR）和对比噪声比（contrast-to-noise ratio，CNR）。结果：实验组的CTDIvol和DLP明显低于对照组（t=-89.95，P＜0.01；t=-35.83，P＜0.01）；2名医师的主观图像质量评价的一致性较好（?资=0.78，P＜0.01），2组图像主观质量评分在下腔静脉、股静脉和腘静脉的差异均无统计学意义（P=0.17，P=0.92，P=0.75）；2组患者在图像噪声方面无统计学差异，但在血管CT值、SNR和CNR上，实验组明显高于对照组（均P＜0.01）。结论：80 kVp联合像素闪烁算法可以常规在直接法下肢静脉CT血管成像中使用，降低辐射剂量，提高血管增强CT值、SNR和CNR。

Abstract:

Objective：To evaluate the radiation dose and image quality of pixel shine（PS） algorithm at 80 kVp in direct computed to－mography（CT） venography of the lower extremities. Methods：Forty-one patients who were clinically diagnosed with lower extremity varices and underwent direct CT venography of the lower extremities were randomly assigned to experimental group（80 kV） and con－trol group（100 kV）. Filtered back projection（FBP） and PS algorithm were used for reconstruction in the control group and the exper－imental group，respectively. The volume CT dose index（CTDIvol） and the dose-length product（DLP） were compared between the two imaging techniques. The images of the fifth lumbar vertebra，the femoral head，and the popliteal fossa were selected. Two radiologists gave subjective scores for quality and noise of the above images. Venous vessel CT value，image noise，signal-to-noise ratio（SNR），and contrast-to-noise ratio（CNR） were measured and calculated. Results：The experimental group had significantly lower CTDIvol and DLP than the control group（t=-89.95，P<0.01；t=-35.83，P<0.01）. The two radiologists achieved a high consistency in subjective evaluation of image quality（?资=0.78，P<0.01）. There were no significant differences in the subjective scores for image quality of the infe－rior vena cava，the femoral vein，or the popliteal vein between the two groups（P=0.17，P=0.92，and P=0.75）. There was no difference in image noise between the two groups. However，the experimental group had significantly higher vessel CT value，SNR，and CNR than the control group（all P<0.01）. Conclusion：PS algorithm at 80 kVp can be routinely used in direct CT venography of the lower extremities to reduce radiation dose and improve vessel CT value，SNR，and CNR.