Controlled saturation magnetization transfer for reproducible multivendor variable flip angle T₁ and T₂ mapping

Abstract

Purpose The widespread clinical application of quantitative MRI has been hindered by a lack of reproducibility across sites and vendors. Previous work has attributed this to incorrect B1 mapping or insufficient spoiling conditions. We recently proposed the controlled saturation magnetization transfer (CSMT) framework and hypothesized that the lack of reproducibility can also be attributed to magnetization transfer effects. This work seeks to validate this hypothesis and demonstrate that reproducible multivendor single‐pool relaxometry can be achieved with the CSMT approach. Methods Three healthy volunteers were scanned on scanners from 3 vendors (GE Healthcare, Philips, Siemens). An extensive set of images necessary for joint T1 and T2 estimation were acquired with (1) each vendor default RF pulses and spoiling conditions; (2) harmonized RF spoiling; and (3) harmonized RF spoiling and CSMT pulses. Different subsets of images were used to generate 6 different T1 and T2 maps for each subject’s data from each vendor. Cross‐protocol, cross‐vendor, and test/retest variability were estimated. Results Harmonized RF spoiling conditions are insufficient to ensure good cross‐vendor reproducibility. Controlled saturation magnetization transfer allows cross‐protocol variability to be reduced from 18.3% to 4.0%. Whole‐brain variability using the same protocol was reduced from a maximum of 19% to 4.5% across sites. Both CSMT and native vendor RF conditions have a reported variability of less than 5% for repeat measures on the same vendor. Conclusion Magnetization transfer effects are a major contributor to intersite/intrasite variability of T1 and T2 estimation. Controlled saturation magnetization transfer stabilizes these effects, paving the way for the use of single‐pool T1 and T2 as a reliable source for clinical diagnosis across sites.

Quantitative T1 mapping using multi-slice multi-shot inversion recovery EPI

“…It has been suggested, however, that the assumption of mono-exponential signal recovery is itself incorrect. Some authors claim that magnetization transfer between free water protons and macromolecule-bound protons itself introduces a second exponential component ( Rioux et al., 2016 ; Rui et al., 2020 ) giving rise to the divergence of published T 1 values. The bi-exponential recovery of longitudinal magnetization observed in most tissue types, including WM and GM tissue ( Gochberg and Gore, 2007 ; Prantner et al., 2008 ) has been attributed to this effect, although the short and long T 1 components are hard to relate to the presumed free water and bound proton pools.…”

Determination of optimal parameters for 3D single‐point macromolecular proton fraction mapping at 7T in healthy and demyelinated mouse brain

“…The original SP‐MPF method requires providing both R 1 and information. Although attention was given to potential insufficient spoiling in the respective VFA‐SPGR and AFI‐SPGR protocols, both methods are known to be sensitive to MT effects, 48‐50 further biasing these priors. Mossahebi et al evidenced the bias of the qMT estimators between cases where R 1,f is provided as a prior (ie, computed while neglecting MT effects) and integrated in the qMT two‐pool model to account for MT effects in VFA‐SPGR protocols 51 .…”

Toward nonparametric diffusion‐ characterization of crossing fibers in the human brain

“…Saturation-recovery based T 1 mapping is also sensitive to magnetization-transfer effects, especially in the present setup comprising an additional refocusing pulse and a fat-saturation pulse. [100][101][102] These technical limitations should be mitigated upon developing a sequence that includes inversion preparation for enhanced T 1 sensitivity and slice shuffling for optimized time efficiency. 9,10 F I G U R E 4 Axial gray-scale maps of the fraction of non thin-bin components 1 − f thin with superimposed ODFs colored by (A) local orientation (with x, y and z corresponding to the "left-right," "anterior-posterior," and "superior-inferior" directions, respectively) and by (B) Ê [ ], respectively.…”