False positive pulmonary embolus - CTPA

Case contributed by Dr Chris O'Donnell


Sudden hypotension at time of prostatic biopsy, no bleeding. Pulmonary hypertension on echocardiogram

Patient Data

Age: 75
Gender: Male

Routine CTPA


Inadequate technique missing the contrast bolus ie contrast predominately in the left side of the circulation missing the pulmonary circulation

Repeat CTPA


CT examination repeated on same day with earlier initiation of the image acquisition. 

Once the contrast bolus is "caught" in the pulmonary circulation, the examination is normal ie no PE

Case Discussion

IN CTPA, the mean HU density of contrast must be > 250 in the pulmonary outflow tract in order to avoid the possibility of flow-related artefacts in the pulmonary artery branches

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