Pulmonary CT angiography: optimization of contrast enhancement technique / 中华放射学杂志

ABSTRACT

ObjectiveTo derive and evaluate the formula of exactly calculating the contrast dosage used during pulmonary CT angiography ( CTPA ). Methods Time density curves in 27 patients who underwent CTPA were collected and analyzed,the formula for calculating contrast dosage during CTPA was derived.68 patients suspected of pulmonary embolism ( PE ) clinically but no PE on CTPA were divided randomly into group A,with bolus tracing technique ( n =26 ),and group B,with small dose injection contrast test (SDCT) (n =42).The CT values of the right main pulmonary artery (RMPA),right upper pulmonary vein ( RUPV),right posterior basal PA,right lower PV (RLPV) and the aorta were calculated.The total contrast dosage and the hard beam artifact in the SVC were compared between the two groups.Student's t test,Chi-square test and Mann-Whitney U test were used.ResultsThe ratio of the time from starting injection to enhancement peak of caudal end of SVC and the time to enhancement peak of the main pulmonary trunk was 0.65 ±0.09 (about 2/3),the formula for contrast dosage calculation was derived as (DTs/3 + STs/2) FR ml/s.The CT values of RMPA and RLPA between the two groups[ (301 ±117),(329 ± 122) and (283 ±95),(277 ±98) HU respectively] were not significantly different (t =1.060,P =0.292 ;t =2.056,P =0.044),but the differences of CT values in the paired PA and PV between the two groups (median were 22.5,58.0 and 170.5,166.5 HU respectively ) were significant (U =292,P =0.001 and U =325,P =0.005),contrast artifact of the SVC (grade 1-3) in group B ( n =34,7,1 respectively) was significantly less than in group A (n =11,10,5 respectively,x2 =10.714,P =0.002),the contrast dosage injected in group A was ( 87.6 ± 7.3 ) ml,and in group B was ( 40.0 ±5.4) ml (P ＜0.01 ).ConclusionCTPA with SDCT technique is superior to that with conventional bolus tracing technique regarding contrast dosage and contrast artifact in the SVC.