CT dose reduction techniques address pulmonary embolism, DVT

Although CT pulmonary angiography and CT venography can diagnose pulmonary embolism and deep venous thrombosis in one study, clinicians are concerned about increased radiation exposure. Multidetector-row CT adjustments can help lower the dose, according to German researchers.

In a prospective study, investigators compared four-row CT scanning and Doppler sonography for detection of DVT of the pelvis and thighs in 41 patients with suspected pulmonary embolism.

Validating previous findings, the German team found that indirect MDCT venography was accurate and quick to assess the deep venous system after CT angiography of the pulmonary arteries within the same examination. Increased collimation and table speeds significantly reduced radiation dose.

By increasing collimation from 2.5 mm to 5 mm and table speed from 12.5 mm to 25 mm, imagers could attain a statistically significant reduction of cumulative effective and effective gonadal doses of up to 12.26% and 13.55%, respectively.

Investigators performed dose estimation using commercially available software. They published their results in the June issue of the Journal of Computer Assisted Tomography.

The current diagnostic standard for DVT - ascending contrast-enhanced venography - is invasive. MRI and ultrasound, on the other hand, have shown good results, but they are limited by cost, availability, and operator-dependent effectiveness.

Indirect MDCT venography allows a quick and safe evaluation in conjunction with CTA in the same study, without the need for additional volumes of contrast media, said principal investigator Dr. Philipp G.C. Begemann, an interventional radiologist from the University Hospital Hamburg-Eppendorf.

Indications for MDCT venography should be considered very carefully, however. The technique seems preferable if the patient is clinically unstable and requires an immediate diagnosis and treatment, Begemann said.

For more information from the Diagnostic Imaging archives:

MRI gains favor for early, accurate DVT diagnosis
http://www.dimag.com/db_area/onlinenews/2003/2003071001.shtml

CT gains favor for imaging pulmonary embolism
http://www.dimag.com/db_area/archives/2003/0303.overread4.di.shtml