In:
Magnetic Resonance in Medicine, Wiley, Vol. 80, No. 2 ( 2018-08), p. 538-547
Abstract:
UTE sequences with a minimal nominal TE of 8 µs have shown promise for direct imaging of myelin protons (T 2 , 〈 1 ms). However, there is still debate about the efficiency of 2D slice‐selective UTE sequences in exciting myelin protons because the half excitation pulses used in these sequences have a relatively long duration (e.g., 0.3–0.6 ms). Here, we compared UTE and inversion‐recovery (IR) UTE sequences used with either hard or half excitation pulses (durations 32 µs or 472 µs, respectively) for imaging myelin in native and deuterated ovine brain at 3T. Methods Freshly frozen ovine brains were dissected into ∼2 mm‐thick pure white matter and ∼3 to 8 mm‐thick cerebral hemisphere specimens, which were imaged before and/or after different immersion time in deuterium oxide. Results Bicomponent analysis of UTE signals obtained with hard excitation pulses detected an ultrashort T 2 component (STC) fraction ( f S ) of 0% to 10% in native specimens, and up to ∼86% in heavily deuterated specimens. f S values were significantly affected by the TIs used in IR‐UTE sequences with either hard or half excitation pulses in native specimens but not in heavily deuterated specimens. The STC was in the range of 150 to 400 µs in all UTE and IR‐UTE measurements obtained with either hard or half excitation pulses. Conclusion Our results further support myelin protons as the major source of the ultrashort signals seen on IR‐UTE images and demonstrate the potential of IR‐UTE sequences with half excitation pulses for directly imaging myelin using clinical scanners. Magn Reson Med 80:538–547, 2017. © 2017 International Society for Magnetic Resonance in Medicine.
Type of Medium:
Online Resource
ISSN:
0740-3194
,
1522-2594
Language:
English
Publisher:
Wiley
Publication Date:
2018
detail.hit.zdb_id:
1493786-4
