Purpose: We sought to investigate the potential of D-maltose, D-sorbitol, and D-mannitol as T2 exchange magnetic resonance imaging (MRI) contrast agents. We also sought to compare the in vivo pharmacokinetics of D-maltose with D-glucose with dynamic contrast enhancement (DCE) MRI.
Methods: T1 and T2 relaxation time constants of the saccharides were measured using eight pH values and nine concentrations. The effect of echo spacing in a multiecho acquisition sequence used for the T2 measurement was evaluated for all samples. Finally, performances of D-maltose and D-glucose during T2-weighted DCE-MRI were compared in vivo.
Results: Estimated T2 relaxivities (r2) of D-glucose and D-maltose were highly and nonlinearly dependent on pH and echo spacing, reaching their maximum at pH=7.0 (~0.08mM−1 s−1). The r2 values of D-sorbitol and D-mannitol were estimated to be ~0.02mM−1 s−1 and were invariant to pH and echo spacing for pH ≤7.0. The change in T2 in tumor and muscle tissues remained constant after administration of D-maltose, whereas the change in T2 decreased in tumor and muscle after administration of D-glucose. Therefore, D-maltose has a longer time window for T2-weighted DCE-MRI in tumors.
Conclusion: We have demonstrated that D-maltose can be used as a T2 exchange MRI contrast agent. The larger, sustained T2-weighted contrast from D-maltose relative to D-glucose has practical advantages for tumor diagnoses during T2-weighted DCE-MRI.
Keywords: D-maltose; DCE-MRI; T2ex; tumor imaging.