For the past three years, in response to an RFA, we have been studying the use of magnetic resonance imaging to diagnose deep venous thrombosis completely noninvasively and without toxicity or ionizing radiation. Deep venous thrombosis remains a major clinical problem involving a wide class of patients. Many of these patients have gone through surgical procedures or have been immobile for periods of time. During the course of the research we came up with a superb candidate for venous imaging. Our technique is completely insensitive to flow in that it images blood based solely on its material properties. This behavior is essential for the imaging of veins, which may be totally occluded by thrombus. Although other methods, such as gradient echo imaging, are successful with relatively slow flows, they cannot deal with complete or almost complete occlusions. This method provides a reliable and robust approach toward the imaging of the entire venous system, independent of pathology. In addition, a variety of methods of separating veins and arteries have been studied and implemented. In the course of this research we have become involved with a number of significant related studies. These include clot characterization in which the magnetic resonance parameters are used to determine significant clot characteristics such as age. Also, we have studied a complementary venous imaging approach we call "slab scan," which exploits wash-in effects in a sequence of image sections. By making each slab relatively narrow the system becomes responsive to extremely slow flows, although not to a complete occlusion. The desirable properties of this approach include robust vein-artery separation and relative immunity to flow artifacts.
NIH ExPorter
NIH ExPorter