Time-division multiplexing (TDM) sequence removes bias in T2 estimation and relaxation-diffusion measurements

Liu, Q.; Gagoski, B.; Shaik, I. A.; Westin, C.-F.; Wilde, E. A.; Schneider, W.; Bilgic, B.; Grissom, W.; Nielsen, J.-F.; Zaitsev, M.; Rathi, Y.; Ning, L.

doi:10.1101/2024.06.03.597138

bioRxiv · 10.1101/2024.06.03.597138

Time-division multiplexing (TDM) sequence removes bias in T2 estimation and relaxation-diffusion measurements

Liu, Q.·Gagoski, B.·Shaik, I. A.·Westin, C.-F.·Wilde, E. A.·Schneider, W.·Bilgic, B.·Grissom, W.·Nielsen, J.-F.·Zaitsev, M.·Rathi, Y.·Ning, L.

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Abstract

PurposeTo compare the performance of multi-echo (ME) and time-division multiplexing (TDM) sequences for accelerated relaxation-diffusion MRI (rdMRI) acquisition and to examine their reliability in estimating accurate rdMRI microstructure measures. MethodThe ME, TDM, and the reference single-echo (SE) sequences with six echo times (TE) were implemented using Pulseq with single-band (SB-) and multi-band 2 (MB2-) acceleration factors. On a diffusion phantom, the image intensities of the three sequences were compared, and the differences were quantified using the normalized root mean squared error (NRMSE). For the in-vivo brain scan, besides the image intensity comparison and T2-estimates, different methods were used to assess sequence-related effects on microstructure estimation, including the relaxation diffusion imaging moment (REDIM) and the maximum-entropy relaxation diffusion distribution (MaxEnt-RDD). ResultsTDM performance was similar to the gold standard SE acquisition, whereas ME showed greater biases (3-4x larger NRMSEs for phantom, 2x for in-vivo). T2 values obtained from TDM closely matched SE, whereas ME sequences underestimated the T2 relaxation time. TDM provided similar diffusion and relaxation parameters as SE using REDIM, whereas SB-ME exhibited a 60% larger bias in the map and on average 3.5x larger bias in the covariance between relaxation-diffusion coefficients. ConclusionOur analysis demonstrates that TDM provides a more accurate estimation of relaxation-diffusion measurements while accelerating the acquisitions by a factor of 2 to 3.

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Liu, Q., Gagoski, B., Shaik, I. A., Westin, C.-F., Wilde, E. A., Schneider, W., Bilgic, B., Grissom, W., Nielsen, J.-F., Zaitsev, M., Rathi, Y., Ning, L.. 2024-06-03. Time-division multiplexing (TDM) sequence removes bias in T2 estimation and relaxation-diffusion measurements. https://doi.org/10.1101/2024.06.03.597138

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