T1D -weighted ihMT imaging - Part I. Isolation of long- and short-T1D components by T1D -filtering

Magn Reson Med. 2022 May;87(5):2313-2328. doi: 10.1002/mrm.29139. Epub 2022 Jan 17.

Abstract

Purpose: To identify T1D -filtering methods, which can specifically isolate various ranges of T1D components as they may be sensitive to different microstructural properties.

Methods: Modified Bloch-Provotorov equations describing a bi-T1D component biophysical model were used to simulate the inhomogeneous magnetization transfer (ihMT) signal from ihMTRAGE sequences at high RF power and low duty-cycle with different switching time values for the dual saturation experiment: Δt = 0.0, 0.8, 1.6, and 3.2 ms. Simulations were compared with experimental signals on the brain gray and white matter tissues of healthy mice at 7T.

Results: The lengthening of Δt created ihMT high-pass T1D -filters, which efficiently eliminated the signal from T1D components shorter than 1 ms, while partially attenuating that of longer components (≥ 1 ms). Subtraction of ihMTR images obtained with Δt = 0.0 ms and Δt = 0.8 ms generated a new ihMT band-pass T1D -filter isolating short-T1D components in the 100-µs to 1-ms range. Simulated ihMTR values in central nervous system tissues were confirmed experimentally.

Conclusion: Long- and short-T1D components were successfully isolated with high RF power and low duty-cycle ihMT filters in the healthy mouse brain. Future studies should investigate the various T1D -range microstructural correlations in in vivo tissues.

Keywords: band-pass T1D-filter; bi-T1D model; high-pass T1D-filter; ihMT T1D-filtering; low duty-cycle.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain / diagnostic imaging
  • Image Processing, Computer-Assisted* / methods
  • Magnetic Resonance Imaging / methods
  • Mice
  • Myelin Sheath / chemistry
  • White Matter* / diagnostic imaging