IMAGE OF THE WEEK 2013
WEEK 15
PULMONARY EMBOLUS
Pulmonary embolism is a common pathology and is now imaged almost exclusively with a CTPA (CT pulmonary angiogram).
With the use of a pump injector high speeds of intravenous contrast can be injected through a peripheral vein, with bolus track software on the CT management console, allowing image triggering when contrast illustrates the pulmonary venous system.
The concept is straightforward. Fill the pulmonary vasculature with dense iodinated contrast, and if an embolus is present it will show as a filling defect within (Figure 1). Multi-slice scanners enable excellent visualisation down to the sub-segmental vessels.
Emboli may be single or multiple (Figure 2). Large volume embolic disease and central emboli, such as the so called ‘saddle embolus’, may result in right heart strain. This may be identified on ECHO or on the CTPA itself as straightening of the intra-ventricular septum.
When an embolus is observed in the axial plane of a vessel (the vessel representing a circle) a rim of contrast may remain around the embolus – the ‘polo mint’ sign (Figure 3).
In a small proportion of cases, the distal lung may infarct – a triangular shaped area of consolidation is evident (Figure 2).
Images and text contributed by
Dr Ian Bickle, Department of Radiology,RIPAS Hospital
All images are copyrighted and property of RIPAS Hospital.