Pulmonary embolism CT


 * Associate Editors-in-Chief: Ujjwal Rastogi, MBBS [mailto:urastogi@perfuse.org]

Overview
Computed tomography with radiocontrast, effectively a pulmonary angiogram imaged by CT and also known as CT pulmonary angiography (CTPA), is increasingly used as the mainstay in diagnosis.

CT Pulmonary angiography
To read the main article on CT Pulmonary angiography, click here

Assessing the accuracy of CT pulmonary angiography is hindered by the rapid changes in the number of rows of detectors available in multidetector CT (MDCT) machines. A study with a mixture of 4 slice and 16 slice scanners reported a sensitivity of 83% and a specificity of 96%. This study noted that additional testing is necessary when the clinical probability is inconsistent with the imaging results. MDCT has progressed to be available with 64 slices, each 0.625 mm thick. These machines take 3-4 seconds to scan and may be gated to the heart beat.

Recent studies have supported the use of MDCT as the best diagnostic tool in the assessment of PE. A recent study has stated, that the diagnostic accuracy of MDCT for detecting right ventricular dysfunction, by using echocardiography as the reference, was 86% (95 CI 0.82-0.91).

Advantages

 * Clinical equivalence
 * Non-invasive nature
 * Greater availability to patients
 * Capability in picking up other lung disorders from the differential diagnosis in case there is no pulmonary embolism.

Limitations

 * Requires readers expertise.
 * Non-Portable and expensive
 * Need contrast bolus comparable to angiogram
 * Contraindicated in Renal insufficiency and contrast allergies patient.

CT findings in Acute PE

 * Thrombus is located centrally within the vascular lumen or occludes the vessel (vessel cut-off sign)
 * Commonly causes distention of the involved vessel.

CT findings in Chronic PE

 * Eccentric and contiguous changes of the vessel wall
 * Reduces the arterial diameter by more than 50%
 * Evidence of recanalization within the thrombus
 * An arterial web is present

CT Slides of patient with Shortness of Breath