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Ferumoxytol-enhanced, dual contrast MRI readily identifies the presence and extent of lower extremity deep vein thrombosis (DVT), according to a report in the March issue of Radiology.

"Although current methodologies for diagnosis of deep venous thrombosis, such as duplex sonography, are cost-effective and reasonably accurate, newer technologies such as contrast-enhanced MRI using an iron oxide blood pool agent have the potential for still greater accuracy, and do not suffer from some of the limitations of current diagnostic methods," Dr. Wei Li from Evanston Northwestern Healthcare, Illinois, told Reuters Health.

Dr. Li and colleagues evaluated the use of a dual-contrast mechanism in conjunction with an iron oxide blood pool contrast agent, ferumoxytol, to depict deep vein thrombosis with MRI in nine patients in whom deep vein thrombosis was depicted with duplex ultrasound.

Image quality scores were consistently superior for ferumoxytol-enhanced MRI images than for precontrast 2D images, the authors report. Ferumoxytol-enhanced images also showed higher contrast-to-noise ratios for thrombus versus blood and for thrombus versus muscle.

Only one thrombus depicted by duplex ultrasound was missed by MRI, the report indicates, because the vessel was accidentally excluded from the imaging volume.

In contrast, MRI detected thrombi in two patients in whom only unilateral ultrasound had been performed, the researchers note.

Imaging after ferumoxytol administration provided detailed evaluation of the peripheral venous system without artifacts, the investigators say, unlike the assessment of thrombus extent with time-of-flight images that was limited by artifacts.

"On the basis of these preliminary results, we believe further evaluation in a larger patient cohort seems warranted to determine the relative accuracy of ferumoxytol-enhanced MR imaging and duplex ultrasound and to assess the potential clinical utility of this imaging approach."

"We anticipate quite a few potential applications in other vascular areas," Dr. Li said. "For instance, the technique should be highly reliable in identifying small intracardiac thrombi and pulmonary emboli."

"The pharmaceutical company that produces ferumoxytol has decided to focus its efforts entirely on obtaining a therapeutic, rather than diagnostic, indication for this agent," Dr. Li said. "Consequently, this particular contrast agent is no longer available to us for diagnostic clinical trials. However, similar iron oxide-based contrast agents are entering clinical trials in Europe, so we expect that our MR venography technique will first be applied overseas for routine clinical use."

"In the meanwhile," Dr. Li said, "we will continue our studies in animal models of venous thrombosis, including the study of potential applications in pulmonary embolism."

Radiology 2007;242:873-881