MR angiography and flow evaluation of the hemodialysis AV-fistulas of forearms. Using phase contrast MR imaging

MR angiography (MRA) and flow rates of the hemodialysis A-V fistulas of forearms were evaluated by phase contrast (PC) MR imaging. In a model of fluid movement, analysis of a suitable protocol for MRA and velocity image to calculate flow velocity have shown that the optimal flip angle of both was 20 degrees and the optimal velocity encoding value of both was 2 times that of the actual velocity. In the clinical investigation of 23 subjects, examinations could be performed with the patients lying in a comfortable position using a plate-type surface coil. Compared with digital subtraction angiography (DSA), the feeding arteries and draining veins were clearly demonstrated by MRA when velocity encoding value was 2 times that of the calculated venous velocity. The anastomoses and venous stenoses could be visualized when velocity encoding value was 7 times that of the calculated venous velocity. The venous flow rates in the well-functioning A-V fistulas (mean, 636.7±225.3 ml/min) were significantly greater than those in the insufficient A-V fistulas (mean, 187.5±105.2 ml/min). In 8 patients, venous flow rates determined by PC velocity images and Doppler ultrasonography showed good correlation. The combination of MRA and measurement of the venous flow rates using PC MR imaging is a useful noninvasive method to assess the status of the hemodialysis A-V fistulas. (author)