New Clinically Feasible 3T MRI Protocol to Discriminate Internal Brain Stem Anatomy

Abstract

Two new 3-T MRI contrast methods, track density imaging and echo modulation curve T2 mapping were combined with simultaneous multislice acquisition to reveal exquisite anatomical detail at 7 canonical levels of the brainstem. Compared to conventional MRI contrasts, many individual brainstem tracts and nuclear groups were directly visualized for the first time at 3-T. This new approach is clinically practical and feasible (total scan time = 20 min) allowing better brainstem anatomical localization and characterization.

Super-Resolution Track Density Imaging: Anatomic Detail versus Quantification

“…The results of the study by Hoch et al, 1 demonstrating the synergy of TDI with other MR imaging parameters to achieve enhanced anatomic delineation are consistent with the findings from previous studies, such as the combination of super-resolution TDI and ultra-high-field T1-weighted images to delineate the substructures of the thalamus at 7T MR imaging.…”

“…14 Given these limitations, it could be argued that the power of super-resolution TDI is not as a quantitative tool but rather in the high anatomic contrast and detail it provides (as illustrated by the results from Hoch et al, 1 and other related studies 3,4,15,16 ). Quantification is therefore better performed on the basis of, for example, other complementary track-based parameters, such as track-weighted apparent diffusion coefficient (TW-ADC), trackweighted fractional anisotropy (TW-FA), and track-weighted fiber-orientation distribution (TW-FOD), 12,17 or even on the basis of other properties of the streamlines themselves (such as their lengths in the average pathlength map [APM] method) 13 or on measures of the voxelwise fiber-orientation distribution (such as those related to the apparent fiber density [AFD] method).…”

“…have read with great interest the article by Hoch et al, 1 in this issue of the American Journal of Neuroradiology describing an MR imaging protocol to discriminate the internal anatomy of the human brain stem. Their study provides a very nice illustration of one of the key strengths of MR imaging, in which multiple MR imaging contrast mechanisms/parameters can complement each other and provide an enhanced visualization of brain structures.…”

“…A related issue, also briefly mentioned in the article by Hoch et al, 1 is that of quantification. While T2 is a well-studied parameter and one that has been used quantitatively for clinical applications in the past (eg, in epilepsy, 5 Friedreich ataxia, 6 and multiple sclerosis, 7 among others), quantification of TDI has been the subject of recent controversy, with some studies reporting successful clinical applications 8-10 and others emphasizing its potential limitations for quantitative studies.…”

Diagnosis of multiple system atrophy

“…Routine MR imaging has very low specificity to distinguish MSA from other atypical parkinsonian syndromes (Schrag et al, 2000; Yekhlef et al, 2003). Increasing use of 7-Telsa MR imaging, and better sequences to discriminate the brainstem anatomy, should enable the development of more sensitive and specific diagnostic algorithms (Hoch et al, 2016; Kim et al, 2016). …”