Curved multiplanar reformatting provides improved visualization of hippocampal anatomy

Abstract

There is a growing body of literature studying changes in hippocampal subfields in a variety of different neurological conditions, but this work has mainly focused on the hippocampal body given challenges in visualization of hippocampal anatomy in the head and tail when sectioned in the typical coronal image plane. Curved multiplanar reformatting (CMPR) is an image reconstruction method that can improve visualization of complex three‐dimensional structures. The objective of this study was to determine whether CMPR could facilitate visualization of the human hippocampal anatomy along the entire caudal–rostral axis. CMPR was applied to high‐resolution magnetic resonance imaging acquired ex vivo on four cadaveric hippocampal specimens at 4.7 T (T2‐weighted, 0.2 × 0.2 × 0.5 mm3). CMPR provided clear visualization of the classic “interlocking C” appearance of the dentate gyrus and cornu ammonis along the entire caudal–rostral axis including the head and tail, which otherwise show complex anatomy on the standard coronal slices. CMPR facilitated visualization of hippocampal anatomy providing the impetus to develop simplified approaches to delineate subfields along the entire hippocampus including the usually neglected head and tail.

Automated hippocampal unfolding for morphometry and subfield segmentation with HippUnfold

“…The axis we define as PD, which follows along the SLM in a coronal slice, is also a landmark relied upon in many manual segmentation protocols for the hippocampal subfields, including a histologically validated protocol that defines subfield boundaries by the proportional distance along the SLM ( Steve et al, 2017 ). The head and tail are areas where these heuristics have conventionally been very difficult to apply, since the slice angulation optimal for the body is not optimal for the curved head and tail, and work using multiplanar reformatting provides one alternative for curved regions of the hippocampus ( Gross et al, 2020 ). Our unfolding approach is conceptually analogous to these approaches, however, the added strength of our approach is that we apply the same conceptual rule (proportional distance along the SLM) while considering the entire 3D structure of the hippocampus.…”

Surface-based hippocampal subfield segmentation

“…medially, and the hippocampal head (anterior) curves medially, posteriorly, and then superiorly, where it terminates on the amygdala. The contiguity of the subfields in each of these regions has been highlighted in recent anatomical work using multiplanar rather than coronal sampling [14], which we illustrate in Figure 1C and in the supplemental video (see the Supplemental information online) showing all slices. Digitationssmaller-scale folds in hippocampal tissue that resemble neocortical gyrificationsare sometimes seen approximately perpendicular to this curvature.…”

Automated hippocampal unfolding for morphometry and subfield segmentation with HippUnfold

“…The axis we define as proximal-distal (PD), which follows along the SLM in a coronal slice, is also a landmark relied upon in many manual segmentation protocols for the hippocampal subfields, including a histologically-validated protocol that defines subfield boundaries by the proportional distance along the SLM [43]. The head and tail are areas where these heuristics have conventionally been very difficult to apply, since the slice angulation optimal for the body is not optimal for the curved head and tail, and work using multiplanar reformatting provides one alternative for curved regions of the hippocampus [44]. Our unfolding approach is conceptually analogous to these approaches, however, the added strength of our approach is that we apply the same conceptual rule (proportional distance along the SLM) while considering the entire 3D structure of the hippocampus.…”