In vivo sodium chemical shift imaging

Area of Science:

• Magnetic Resonance Imaging
• Nuclear Magnetic Resonance Spectroscopy
• Medical Imaging

Background:

• Sodium chemical shift imaging (NaCSI) requires effective shift reagents to enhance spectral resolution.
• Thulium(III) 1,4,7,10-tetraazacyclododecane N,N",N",N"'-tetramethylenephosphonate (TmDOTP5-) and dysprosium(III)triethylenetetramine-hexaacetate (DyTTHA3-) are potential shift reagents for NaCSI.

Purpose of the Study:

• To compare the efficacy of TmDOTP5- and DyTTHA3- as shift reagents for 23Na chemical shift imaging (NaCSI).
• To evaluate the contributions of bulk magnetic susceptibility (BMS) effects and hyperfine shifts for these reagents.
• To assess the performance of TmDOTP5- under physiological conditions and in vivo.

Main Methods:

• Phantom experiments were conducted to evaluate the relative contributions of BMS effects and hyperfine shifts.
• The dependence of the 23Na NMR frequency shift induced by TmDOTP5- on pH and free Ca2+ concentration was assessed.
• In vivo NaCSI experiments were performed using TmDOTP5- in rabbit eyes.

Main Results:

• Ratios of BMS effects to hyperfine shifts indicate TmDOTP5- is more effective than DyTTHA3- for 23Na NMR spectroscopy and NaCSI.
• TmDOTP5- demonstrates good spectral resolution under physiological conditions.
• In vivo studies successfully utilized TmDOTP5- for studying diffusion and fluid clearance in rabbit eyes.

Conclusions:

• TmDOTP5- is a superior shift reagent compared to DyTTHA3- for NaCSI and 23Na NMR spectroscopy.
• TmDOTP5- is effective for in vivo NaCSI applications, offering good spectral resolution under physiological conditions.
• NaCSI technique with TmDOTP5- shows promise for in vivo studies of ocular fluid dynamics.