%0 Journal Article
%T Time-division multiplexing (TDM) sequence removes bias in T2 estimation and relaxation-diffusion measurements.
%A Liu Q
%A Gagoski B
%A Shaik IA
%A Westin CF
%A Wilde EA
%A Schneider W
%A Bilgic B
%A Grissom WA
%A Nielsen JF
%A Zaitsev M
%A Rathi Y
%A Ning L
%J Magn Reson Med
%V 0
%N 0
%D 2024 Aug 13
%M 39136245
%F 3.737
%R 10.1002/mrm.30246
%X <B>OBJECTIVE: </B>To 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.<BR><B>METHODS: </B>The ME, TDM, and the reference single-echo (SE) sequences with six TEs 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 RMS error (NRMSE). Shinnar-Le Roux (SLR) pulses were implemented for the SB-ME and SB-SE sequences to investigate the impact of slice profiles on ME sequences. 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).<BR><B>RESULTS: </B>TDM performance was similar to the gold standard SE acquisition, whereas ME showed greater biases (3-4× larger NRMSEs for phantom, 2× 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 <R2> map and on average 3.5× larger bias in the covariance between relaxation-diffusion coefficients.<BR><B>CONCLUSIONS: </B>Our analysis demonstrates that TDM provides a more accurate estimation of relaxation-diffusion measurements while accelerating the acquisitions by a factor of 2 to 3.