肾动脉CTA最佳成像时间点分析:CT灌注成像与CTA对比

目的采用全肾CT灌注成像(CTP)数据提取最佳CTA期相,并与自动触发扫描获得的CTA图像进行对比。方法回顾性分析因怀疑肾脏或上中腹部疾病行肾脏CT增强及灌注扫描的连续患者(n=21)以及同时期进行全腹CTA成像的患者(n=19)。灌注扫描患者先进行肾脏平扫,然后进行灌注扫描;CTA成像患者使用自动触发技术扫描。灌注图像采用CT Perfusion 4D肾脏灌注软件进行分析,根据左肾动脉和左肾静脉的时间-密度曲线(TDC)选择两个肾动脉CTA的期相,分别为A组和B组。CTA扫描数据使用Viewer功能进行测量,为C组。记录左肾动脉、左肾静脉CT值以及皮下脂肪的CT值和SD值。计算左肾动脉与左肾静脉的CT值差值、CNR及SNR,并进行对比。将CTA数据进行肾动脉血管重建,进行主观评分并进行分析。结果 3组的左肾动脉CT值、左肾静脉CT值、动静脉CT值差值、皮下脂肪CT值、皮下脂肪SD值、CNR、SNR间差异均有统计学意义(P均0.001)。除A组与C组肾动脉CT值、A组与B组和B组与C组动静脉CT值差值、A组与B组皮下脂肪CT值和SD值、CNR、SNR差异无统计学意义外(P均0.05),余两两比较差异均有统计学意义(P均0.05)。结论利用肾脏CTP数据,可获得肾动脉CTA数据;肾动脉与肾静脉CT值差值最大且满足肾动脉CT值超过300HU的期相为最佳肾动脉CTA成像期相。

Analysis of optimal imaging time for renal CTA: Comparision of CT perfusion

Objective To select the optimal imaging phase for renal CTA extracted from the renal CT perfusion (CTP) data, and to compare its image quality with the conventional CTA triggered using an automatic bolus tracking technique. Methods The images of 21 consecutive renal CTP (n=21) patients and 19 renal CTA (n=19) patients were analyzed retrospectively. The CTP was performed followed by noncontrast CT. The CTA was performed using an automatic bolus tracking technique. The CTP data was postprocessed on CT Perfusion 4D kidney software. The renal artery CTA images in the CTP imaging were extracted at the scan phases based on the time-density curve (TDC) of the left renal artery (group A) and left renal vein (group B). CTA images (group C) were analyzed using the Viewer function. The CT values of left renal artery and left renal vein, CT values and SD values of subcutaneous fat in the three groups were recorded. The difference of CT value between left renal artery and left renal vein, CNR and SNR of the left renal artery were recorded and compared. The subjective scoring of CTA images was performed and compared. Results There were significant differences on CT values of left renal artery and left renal vein, differences of CT value between left renal artery and vein, CT value of subcutaneous fat, SD of subcutaneous fat, CNR and SNR of left renal artery among the three groups (all P<0.001). Except the CT values of renal artery in group A and group C, differences of CT value between artery and vein in group A and group B, group B and group C, CT value and SD value of subcutaneous fat, CNR, SNR in group A and group B, there were significant differences in all comparisons between any two groups (all P>0.05). Conclusion The renal CTA images can be extracted from CTP scans. The optimal phase is when the differences of CT value between the left renal artery and vein at the maximum, combined with the CT value of the left renal artery is more than 300 HU. CTA image generated at the optimal phase is much better than that of the CTA obtained with the automatic bolus tracking technique.