In Vivo 7T MRI of the Non-Human Primate Brainstem

Abstract

Structural brain imaging provides a critical framework for performing stereotactic and intraoperative MRI-guided surgical procedures, with procedural efficacy often dependent upon visualization of the target with which to operate. Here, we describe tools for in vivo, subject-specific visualization and demarcation of regions within the brainstem. High-field 7T susceptibility-weighted imaging and diffusion-weighted imaging of the brain were collected using a customized head coil from eight rhesus macaques. Fiber tracts including the superior cerebellar peduncle, medial lemniscus, and lateral lemniscus were identified using high-resolution probabilistic diffusion tractography, which resulted in three-dimensional fiber tract reconstructions that were comparable to those extracted from sequential application of a two-dimensional nonlinear brain atlas warping algorithm. In the susceptibility-weighted imaging, white matter tracts within the brainstem were also identified as hypointense regions, and the degree of hypointensity was age-dependent. This combination of imaging modalities also enabled identifying the location and extent of several brainstem nuclei, including the periaqueductal gray, pedunculopontine nucleus, and inferior colliculus. These clinically-relevant high-field imaging approaches have potential to enable more accurate and comprehensive subject-specific visualization of the brainstem and to ultimately improve patient-specific neurosurgical targeting procedures, including deep brain stimulation lead implantation.

Depth‐dependence of visual signals in the human superior colliculus at 9.4 T

“…Other groups used surface based 3D mapping of the superior colliculi to derive depth definitions and information [Katyal and Ress, 2014]. We believe that high-field magnetic resonance imaging and quantitative MRI approaches [Deistung et al 2013;Lorio et al, 2016;Zitella et al, 2015] represent important tools to reach this goal. Obviously, a direct anatomical definition of intracollicular regions or layers based on the microstructure of the superior colliculi [Naidich et al, 2009] would be desirable.…”

“…Obviously, a direct anatomical definition of intracollicular regions or layers based on the microstructure of the superior colliculi [Naidich et al, 2009] would be desirable. We believe that high-field magnetic resonance imaging and quantitative MRI approaches [Deistung et al 2013;Lorio et al, 2016;Zitella et al, 2015] represent important tools to reach this goal.…”

Identification of the pedunculopontine nucleus and surrounding white matter tracts on 7T diffusion tensor imaging, combined with histological validation

“…In a recent study, a multi-modal imaging approach using 7T MRI enables accurate identification of the PPN by combining DTI and susceptibility weighted imaging (SWI) in non-human primate brainstems. However, to the authors’ knowledge, no other studies have used SWI solely to identify the PPN in the brainstem [30]. This is relevant as subcortical gray matter is known to have paramagnetic, diamagnetic and/or ferromagnetic properties, which all interact with the local magnetic field of the MRI.…”

Multimodal 7T Imaging of Thalamic Nuclei for Preclinical Deep Brain Stimulation Applications

“…First, the data set included six females and only one young male rhesus macaque. These subjects were selected in part because their cranial musculature was minimal allowing for the receiver coils to be placed closer to the brain (Zitella et al, 2015 ). Another limitation is the use of an atlas that is particular to one NHP, along with its own nomenclature and criteria of demarcation (Macchi and Jones, 1997 ).…”