MR VENOGRAPHY OF THE CALF - VALUE OF FLOW-ENHANCED TIME-OF-FLIGHT ECHOPLANAR IMAGING

OBJECTIVE. Release of a tourniquet on the thigh and termination of Val salva's maneuver result in a transient increase in venous blood flow i n the leg. The purpose of this study was to determine the value of tim e-of-flight echoplanar imaging performed with these flow-enhancing met hods to image the veins of the calf. SUBJECTS AND METHODS. Flow volume s in the femoral veins in eight volunteers were determined with a two- dimensional phase-contrast MR imaging technique before and immediately , 20, 40, and 60 sec after termination of Valsalva's maneuver and thig h vein occlusion, Subsequently, the calf veins of II healthy volunteer s were imaged with a two-dimensional four-shot echoplanar MR imaging t echnique. Forty-one 5-mm-thick sections were obtained over 10 sec imme diately after termination of venous occlusion. Visibility of the three venous bundles was analyzed in the proximal, middle, and distal porti ons of the calf on the basis of a four-point scale. Finally, the calf of a single patient with documented DVT was imaged by the same MR imag ing technique. RESULTS. Both Valsalva's maneuver and venous occlusion caused significant increases in venous flow (p<.05) only during the fi rst 20 sec after termination of the maneuver and the occlusion. Venous occlusion had a significantly greater effect than did Valsalva's mane uver (p<.05). Flow augmentation by venous occlusion of the thigh impro ved calf vein visualization with time-of-flight echoplanar MR imaging (p < .0001). Of the 99 calf vein segments examined, 93 were clearly se en, Thrombi were seen in the patient study. CONCLUSION. Multishot time -of-flight echoplanar imaging can exploit the short-lived effect of me chanical flow-enhancing measures, resulting in good visualization of c alf veins. The true diagnostic impact of this technique needs to be ev aluated in a patient study.