MEASUREMENT OF TUMOR VASCULAR VOLUME AND MEAN MICROVASCULAR RANDOM FLOW VELOCITY MAGNITUDE BY DYNAMIC GD-DTPA-ALBUMIN ENHANCED AND DIFFUSION-WEIGHTED MRI

Tumor vascular volume fraction and the magnitude of the mean microvasc ular random flow velocity were measured in an animal tumor model by co mbining dynamic Gd-DTPA-albumin enhanced MRI and diffusion-weighted MR I in conjunction with a compartmental modeling analysis. The vascular volume fraction maps were obtained from the dynamic Gd-DTPA-albumin en hanced MRI measurement. It was found that the vascular volume fraction for Walker 256 tumor was higher within the outgrowing rim and decreas ed towards the central region, The average value obtained from five an imals was 0.062 +/- 0.009 ml/g, By using the vascular volume fraction from the Gd-DTPA-albumin enhanced MRI measurement, maps of the magnitu de of the mean microvascular random flow velocity were obtained from t he diffusion-weighted MRI measurements with the compartmental modeling analysis, The relative extravascular and intravascular contributions to the diffusion-weighted MRI signal were determined for three tissue groups with different Gd-DTPA-albumin enhancement characteristics, and the flow and molecular diffusion-induced attenuation factors for the intravascular compartment were also compared. The mean microvascular r andom flow velocity magnitude maps were obtained with an average value of 0.67 +/- 0.06 mm/s.