Comparison of BOLD contrast and Gd-DTPA dynamic contrast-enhanced imaging in rat prostate tumor

The microcirculation and oxygenation of a tumor play important roles in its responsiveness to cytotoxic treatment, and noninvasive assessments of its vascular properties may have prognostic value. Dynamic contrast-enhanced (DCE) (1)H MRI based on infusion of Gd-DTPA, and blood oxygen level-dependent (BOLD) contrast based on altering inhaled gas are both sensitive to vascular characteristics. This study compares the effects observed in eight Dunning prostate R3327-AT1 rat tumors imaged sequentially at 4.7 Tesla by echo-planar imaging (EPI). Both interventions generated a significant response, and each revealed significant differences between the center and periphery of the tumors. On a voxel-by-voxel basis across the whole tumor population, there was a close correlation between the maximum rate of signal response and the magnitude of response to each intervention (R(2) >or= 0.6, P < 0.0001). However, when the data were analyzed separately for each individual tumor, some showed a weak correlation (R(2) < 0.4), particularly for DCE, and the nature (slope) varied between separate tumors. Generally, there was a weak correlation (N = 7, R(2) < 0.5) between responses to the two interventions on a tumor-by-tumor basis, which emphasizes that the techniques are not equivalent. Both techniques revealed intra- and intertumor heterogeneity, but the BOLD response was more rapidly reversible than the DCE response. This suggests that the BOLD technique may be a useful tool for investigating interventions (such as drugs) that cause vascular disruption.