Oxygen and Glucose as Stimulation Agents for BOLD Functional MR Imaging of Rabbit Liver: A Feasibility Study.

PURPOSE: To assess the feasibility of using oxygen and glucose as stimulating agents in blood-oxygen-level-dependent (BOLD) Functional Magnetic Resonance Imaging (fMRI) of rabbit liver and analyze the impacts by blood flow.

METHODS: Pure oxygen inhalation, intravenous injection and oral administration of glucose were given to 11 New Zealand white rabbits to compare the differences of liver T2 *, aortic flow (AF), portal vein flow (PVF), aortic area (AA) and portal vein area (PVA) before and at 5 min, 10 min, 20 min, 30 min after administrations. AF and PVF were acquired by two dimensional (2D) Phase Contrast MR (2D-PCMR). The impacts of AF and PVF upon BOLD fMRI were analyzed.

RESULTS: AF and PVF declined at 5 min after oxygen inhalation and were significantly different from baseline, then reverted to baseline. No significant difference was observed in liver T2 *, AA and PVA before and after oxygen inhalation. AF, PVF, AA and PVA showed no significant difference before and after glucose intravenous injection, while liver T2 * increased gradually with significant difference. AF and liver T2 * were significantly different before and after glucose oral administration and increased gradually, AA was significantly different before and after glucose administration at 10 min and 20 min. PVF and PVA started to be different from baseline at 10 min. Greatest variation of T2 * (19.6%) was induced by glucose oral administration after 30 min.

CONCLUSION: Rabbit liver T2 * increasing by glucose intravenous injection is possibly associated with glycogen synthesis, provides the possibility to evaluate liver function. Glucose oral administration demonstrated an optimal comparative effect of raising T2 *, however, resulted from the superposition of increased glycogen synthesis and blood flow. Inhalation of pure oxygen didn't alter the rabbit liver T2 *, which may possibly result from an offset between the increased concentration of oxyhemoglobin and decreased blood flow.