钙化积分扫描缩短冠脉CTA扫描范围及降低辐射量的作用

Effect of calcium scoring scan in reducing scan range and radiation dose in retrospectively ECG-gated CT coronary angiography

目的:探讨使用钙化积分扫描缩短增强扫描范围以降低后门控冠状动脉CTA检查辐射量的临床应用价值。方法:40例患者行冠脉钙化积分及冠脉CTA检查,其增强扫描的实际扫描范围根据钙化积分扫描图像来决定,即冠状动脉树上缘1cm至心尖部心包影即将消失的层面。并按常规方法在定位像上测量增强扫描的预计扫描范围,即气管隆突下1cm至心脏下缘2cm。比较两种扫描范围及相应的辐射剂量的差异。结果:实际扫描范围比预计扫描范围平均缩短(2.09±0.76)cm(t=17.31,P<0.01),冠状动脉CTA各序列总剂量较常规方法平均减少(1.51±0.87)mSv,差异有极显著性意义(t=10.92,P<0.01),相当于各序列平均剂量总和的9.20%。结论:使用钙化积分扫描图像能有效缩短增强扫描的范围,从而明显降低冠状动脉CT血管成像的辐射量。

Objective：To find out a way of reducing scan range in retrospectively ECG-gated CT coronary angiography in order to reduce the radiation dose.Methods：Forty consecutive patients were analyzed retrospectively.The scan range of CT coronary angiography derived respectively from the scout view and from the axial images of calcium scoring were compared.The former was assumed to be determined from 1cm under the trachea carina to 2cm under the inferior margin of the heart.The latter was performed by identifying the left anterior descending coronary artery and posterior descending coronary artery and adding 1cm cranially and caudally.Effective radiation doses were calculated for CT coronary angiography using both scout view-derived and calcium scoring-derived scan range.Results：The calcium scoring-derived range was（10.40±0.60）cm;while the scout view-derived range was（12.5±0.94）cm which was significantly larger than that of using the calcium scoring-derived scan（t=17.31,P0.01）.The average difference between them was（2.09±0.76）cm,corresponding to a radiation dose reduction of（1.67±0.72）mSv.After offsetting the dose given for the calcium scoring scan,the savings in radiation exposure when using a calcium scoring-derived instead of a scout view-derived scan range for CT coronary angiography-including the radiation dose of the calcium scoring scan and the test bolus scan-was（1.25±0.72）mSv（t=10.92,P0.01）,which accounted for a dose reduction of 9.20%.Conclusion：Using the images from cal-cium scoring instead of the scout view to determine the scan range of contrast-unenhanced CT coronary angiography can effectively decrease the scan range and reduce the radiation dose significantly.