Assalamu’alaikum may this reply helps people to the day of Judgement
the question can be answer with the following questions:
1. Do your CT has contrast enhancement to time evaluation software?
if you do, performing CTPA in my opinion, is best done by test bolus protocol. This is however, understanding the delay time, or time consumed by your machine mechanics correlated to the dynamicity in the pulmonary artery is crucial to gain the best quality image in CTPA.
inherent timing (scanning time is always ruled out from the setting) hence the contrast is actually utilizing the time, reaching the pulmonary arteries! therefore the vein contamination may occurred.
The setting to the examination is crucial to assure only pulmonary artery was enhanced for the entire examination. this will give confidence in reporting to locate accurately if the embolism is present.
test bolus protocol offer the specificity in enhancement by testing the time of contrast enhancement in the pulmonary arteries
by utilizing the evaluated time, pulmonary vein enhancement can be ruled out
this is however, limited to the heart condition of the patient, also, understanding the graph that denotes the actual timing can be initially confusing.
In my experience we have rectified the techniques several times before we achieve the best quality image in CTPA….and always most of the time.