Improved determination of spin density, T₁ and T₂ from a three-parameter fit to multiple-delay-multiple-echo (MDME) NMR images

A method is presented for simultaneously determining values of relative hydrogen spin density N_r, T₁ and T₂ from a single set of NMR image intensities acquired in a short imaging time. Present methods use separate acquisitions and data sets to determine all three parameters. In the method presented, multiple-echo data are collected at multiple delays in virtually the same imaging time used to obtain T₁ and a T₂-weighted N_r from a separate saturation recovery (SR) T₁ measurement. All three parameters are then determined by a three-parameter fit of a derived signal intensity equation to these multiple-delay-multiple-echo (MDME) data. This provides an inherent correction of N_r for T₁ and T₂ weighting without the use of sequences with T_D>5T₁, and without further data collection for a separate T₂ measurement. It also provides an effective reduction in the noise of the separate T₂ measurement. A three-parameter fit to MDME data appears to be superior to the separate T ₁ and T₂ measurements currently used to determine all three parameters. Calculations performed on CrCl₃ solutions produced T₁ values from 21 ms to 3.4 s, T₂ values from 6 to 714 ms, and standard errors as low as 0.33%, with a net imaging time of the order of that required for routine low-noise signal intensity imaging. The method could potentially be used in NMR spectroscopy to give similar benefits.