{'fraction_non_alphanumeric': 0.03990610328638498, 'fraction_numerical': 0.022887323943661973, 'mean_word_length': 5.338289962825279, 'pattern_counts': {'":': 0, '<': 3, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
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) 1H 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 (R2 ≥ 0.6, P < 0.0001). However, when the data were analyzed separately for each individual tumor, some showed a weak correlation (R2 < 0.4), particularly for DCE, and the nature (slope) varied between separate tumors. Generally, there was a weak correlation (N = 7, R2 < 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. Magn Reson Med 51:953–960, 2004. © 2004 Wiley‐Liss, Inc.