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Tumor blood volume assays using contrast-enhanced magnetic resonance imaging: regional heterogeneity and postmortem artifacts.

Tumor blood volume (BV), subject to both morphologic and physiologic influences, can be measured using contrast-enhanced magnetic resonance imaging (MRI). The aims of this study were to determine whether MRI enhanced with a macromolecular contrast medium (MMCM) could resolve differences in BV between different tumor types, between different regions within tumors, and within the same tumor in life and after death. Tumor BV estimates were based on the MRI signal intensity responses in the tumors and in reference venous blood following enhancement with a blood pool MMCM using two mammary adenocarcinoma models. Estimates of BV were made before and immediately following death. An in vitro measurement of tumor gadolinium concentration following death was correlated with MRI enhancement. Statistically significant differences (P < 0.05) were observed in MRI-estimated tumor BV between tumor subtypes, between in vivo and postmortem measurements, and between the tumor periphery and tumor centers. MRI assays enhanced with a macromolecular contrast agent can resolve blood volume differences between tumor types, between regions within the same tumor, and between vital and postmortem states.