Comparison of 1H blood oxygen level–dependent (BOLD) and 19F MRI to investigate tumor oxygenation

Fluorine‐19 [¹⁹F] MRI oximetry and ¹H blood oxygen level–dependent (BOLD) MRI were used to investigate tumor oxygenation in rat breast 13762NF carcinomas, and correlations between the techniques were examined. A range of tissue oxygen partial pressure (pO₂) values was found in the nine tumors while the anesthetized rats breathed air, with individual tumor pO₂ ranging from a mean of 1 to 36 torr and hypoxic fraction (HF10) (<10 torr) ranging from 0% to 75%, indicating a large intra‐ and intertumor heterogeneity. Breathing oxygen produced significant increase in tumor pO₂ (mean ΔpO₂ = 50 torr) and decrease in HF₁₀ (P < 0.01). ¹H BOLD MRI observed using a spin echo‐planar imaging (EPI) sequence revealed a heterogeneous response and significant increase in mean tumor signal intensity (SI) (ΔSI = 7%, P < 0.01). R measured by multigradient‐echo (MGRE) MRI decreased significantly in response to oxygen (mean ΔR = ?4 s^?1; P < 0.05). A significant correlation was found between changes in mean tumor pO₂ and mean EPI BOLD ΔSI accompanying oxygen breathing (r² > 0.7, P < 0.001). Our results suggest that BOLD MRI provides information about tumor oxygenation and may be useful to predict pO₂ changes accompanying interventions. Significantly, the magnitude of the BOLD response appears to be predictive for residual tumor HFs. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.