Spin-lock imaging of 3-o-methyl-D glucose (3oMG) in brain tumors.

PURPOSE: To evaluate the ability of spin-lock imaging to detect the uptake of 3-o-methyl-D-glucose (3oMG) in normal brain and brain tumors in animals.

METHODS: Measurements of the longitudinal relaxation rate in the rotating frame (R1ρ ) were made over a range of spin-lock powers in rat brains bearing 9L tumors. The dispersion of R1ρ values was quantified by ΔR1ρ , the difference of R1ρ values acquired with low and high locking powers. The glucose analogue 3oMG was administered intravenously and the differences of ΔR1ρ values ( ΔR1ρdiff) before and as a function of time after administration were calculated to isolate the contribution of 3oMG to the dispersions, which at high fields primarily reflects chemical exchange effects. In addition, the ratio of image signals from low and high locking fields (the spin-lock ratio, SLR), which requires fewer acquisitions and varies directly with ΔR1ρ , was computed as an alternative measure of the variation with locking power, and changes in SLR (SLRdiff ) after 3oMG were evaluated.

RESULTS: Both ΔR1ρdiff and SLRdiff in tumors increased rapidly after injection, whereas intact brain showed a gradual increase up to 1 h. The ΔR1ρdiff and SLRdiff were significantly different between tumors and contralateral normal tissues.

CONCLUSION: Spin-lock methods can be used to detect 3oMG in vivo after injection, and appropriate analyses of MRI signals allow tumors to be distinguished from normal brain.