Pulmonary embolism: Low dose contrast MSCT pulmonary angiography with modified test bolus technique

•Test bolus technique increase the diagnostic quality score of the scans performed.•Provides better evaluation of the pulmonary arteries and its subsegmental branches.•Increase the main pulmonary artery average density, decrease average density of the aorta and pulmonary veins.•Increase the confidence and accuracy rate of diagnostic examinations.•Volume of IV contrast decreased by 40 % than in bolus tracking. This study aims to prove that the test bolus technique provides a better selective imaging study of the pulmonary arterial system in comparison to the automatic bolus-tracking technique. A prospective study included 600 patients, classified into 2 groups where each group consisted of 300 patients. In group A, we used the bolus tracking technique with 80−100 ml of contrast while in group B test bolus technique was used with 50 mL of contrast. It was clear that the Main PA average density was 260.5 HU in group A and increased to 320 HU in group B with P value < 0.002. The Ascending aorta average density decreased from 250 HU in group A to 130 HU in group B with P value