REGIONAL COMPARISON OF TUMOR VASCULARITY AND PERMEABILITY PARAMETERS MEASURED BY ALBUMIN-GD-DTPA AND GD-DTPA

Sequential albumin-Gd-DTPA and Gd-DTPA dynamic enhancement studies wer e performed in an animal tumor model for the comparison of regional va scularity and permeability parameters measured by these two different sizes of contrast agents, The early albumin-Gd-DTPA enhancement arises from the vascular compartment, and the averaged signal enhancement de rived from the first 3 to first 6 images postinjection can be reliably used to assess vascularity. The signal intensity in the images during the period of 5-10 min post-albumin-Gd-DTPA injection shows a steady linear variation, The intercept of the linear relationship is another indicator of the vascularity and the slope represents the tumor permea bility to albumin-Gd-DTPA, The Gd-DTPA enhancement study was analyzed by a two-compartmental pharmacokinetic model to calculate the regional vascularity and permeability, The permeability parameters measured fr om albumin-Gd-DTPA and Gd-DTPA show an excellent correlation, The vasc ularity parameters measured from albumin-Gd-DTPA show good linear corr elation with the low vascularity groups measured by Gd-DTPA, but show saturation for the high vascularity groups, The enhancement mechanisms for both contrast agents are discussed to relate the imaging paramete rs to the physiological variables.