T 1 and T 2 quantification from standard turbo spin echo images

Purpose To extract longitudinal and transverse (T 1 and T 2 ) relaxation maps from standard MRI methods. Methods Bloch simulations were used to model relative signal amplitudes from standard turbo spin‐echo sequences: proton density weighted, T 2 ‐weighted, and either T 2 ‐weighted fluid attenuated inversion recovery or T 1 ‐weighted images. Simulations over a range of expected parameter values yielded a look‐up table of relative signal intensities of these sequences. Weighted images and flip angle maps were acquired in 8 subjects at 3 T using both single and multislice acquisitions. The T 1 and T 2 maps were fit by comparing the weighted images to the look‐up table, given the measured flip angles. Results were compared with inversion recovery and multi‐echo spin‐echo experiments. Results A region analysis showed that relaxation maps computed from single‐slice proton density, T 2 and T 1 weighting provided a mean T 1 error of 4% in gray matter and 11% in white matter, and a mean T 2 error of 3% and 4%, respectively, in comparison to reference measurements. In multislice acquisitions that are optimized to reduce cross‐talk and incidental magnetization transfer, the mean T 1 error was 7% in gray matter and 1% in white matter, and the mean T 2 errors were 3% and 4%, respectively. The best T 1 results were achieved using proton density, T 2 and T 1 weighting rather than the fluid attenuated inversion recovery, although T 2 maps were largely unaffected by this choice. Incidental magnetization transfer reduced T 1 accuracy in standard interleaved multislice acquisitions. Conclusion Through exact sequence modeling and separate flip angle measurement, T 2 and T 1 may be quantified from a turbo spin‐echo brain protocol with proton density, T 2 , and T 1 weighting.