Optimal time for pulmonary arterial and venous imaging by a wide-area detector：a feasibility study

Abstract:

Objective：To explore the practical value of the optimal time for pulmonary arterial and venous imaging by a wide-area de－tector using perfusion scanning mode by comparing the image quality and radiation dose of multi-phase computed tomography an－giography（CTA） and conventional single-phase CTA. Methods：Contrast-enhanced computed tomography（CT） of the lung was per－formed in 108 patients scheduled for right upper lung lobe resection due to ground-glass opacity（GGO）. According to the examination results of the Revolution CT，the patients were divided into 2 groups（54 cases in each group）：group A（using perfusion scanning） and group B（using automatic bolus tracking triggered by contrast enhancement）. Patients in group A underwent multi-mode CT examination using perfusion scanning，including plain CT scan and CT perfusion（CTP） of the lung. After contrast agent injection，axial CT scan was performed on the 160 mm layer in a region of interest with a phase interval of 2 seconds until the end of pulmonary venous phase. Patients in group B underwent conventional CT using automatic bolus tracking triggered by contrast enhancement. The pulmonary trunk，right pulmonary artery，right upper lobe pulmonary artery，right apical pulmonary artery，aorta，and their accompanying veins were selected to be measured on the scanning images taken during the pulmonary arterial and venous phases for all the patients；the CT values and noise standard deviation（SD） were obtained from the measurement，and the differences in CT values between the four groups were calculated；meanwhile，an integral method was used for evaluation of visualization of grade 5 or 6 pulmonary arteries and veins. Results：There were no significant differences between the two groups in the CT values of grade 1-4 pulmonary arteries and veins，except grade 3 and 4 pul－monary arteries（P=0.010 and 0.003），on computed tomography pulmonary angiography（CTPA）（P>0.05）. Compared with group B，group A had significantly larger CT value differences between pulmonary arteries and their accompanying veins on CTPA and between pulmonary veins and their accompanying arteries on computed tomography pulmonary venography（CTPV）（all P<0.05）. In the evaluation of visualization of grade 5 or 6 pulmonary arteries and their accompanying veins by the integral method，the results showed that both groups had a score of 3 in the visualization of pulmonary arteries，but had significantly different scores in the visualization of small pulmonary venous branches（group A：3.00[3.00，3.00]，group B：2.00[1.75，3.00]，Z=2.814，P=0.005）. Meanwhile，there were no significant differences between the two groups in the SD values of pulmonary trunk（group A：28.45±3.47，group B：29.47±3.80，t=0.627，P=0.539） or right upper pulmonary vein（group A：27.27±7.56，group B：27.76±6.44，t=0.156，P=0.878）. Conclusion：The perfusion-like method used by a wide-area detector can not only meet the requirements for CT values of the pulmonary arteries and veins，but it can also effectively separate the pulmonary arteries from the veins，which is especially helpful for thoracoscopic pulmonary segmental resection due to GGO in clinical practice；therefore，it holds promise for clinical application.