MRI‐based large deformation high dimensional mapping of the hippocampus in rats: Development and validation of the technique

Abstract

Purpose:To report the detection of structural and functional biological changes in living animals using small animal in vivo MRI that complements traditional ex vivo histological techniques. We report the development and validation of the application of large deformation high dimensional mapping (HDM-LD) segmentation for the hippocampus in the rat. Materials and Methods:High resolution volumetric T2 weighted MRI images were acquired at 4.7 Tesla from six male in-breed nonepileptic Wistar rats. Two HDM-LD segmentations of the hippocampus (automated 1 and automated 2) were compared with the manual segmentations of two investigators who independently segmented the hippocampi (manual 1 and manual 2). Results:The mean overlap for the hippocampi between automated 1 and automated 2 for the right hippocampi was 94.4% (SD 1.0) and for the left hippocampi was 94.3% (SD 2.5), while the mean overlap between automated 1 and manual 1 for the right hippocampi was 91.4% (SD 1.3) and for the left hippocampi was 91.9% (SD 1.4). Mean values for absolute differences for comparisons of all the segmentations were the following: automated 1 versus automated 2, 3.2% (SD 1.0); manual 1 versus manual 2 6.82% (SD 5.22); automated 1 versus manual 1 13.0% (SD 1.8).Conclusion: HDM-LD can be applied to obtain accurate and reproducible three-dimensional segmentations of the hippocampus from rat MR images. HDM-LD will be a useful tool for investigations of hippocampal structural changes in vivo in rat models of human disease.

Stent fracture associated with drug‐eluting stents: Clinical characteristics and implications

“…Our section (700 μm in thickness) induced a partial volume effect. By comparison, Wolf et al reported a hippocampal volume of about 100 mm 3 (section thickness 600 μm) (Wolf et al, 2002) and (Hogan et al, 2009) about 74 mm 3 (section thickness 500 μm), while we obtained about 117 mm 3 (700 μm). However, Kalisch et al (2006) and Driscoll et al (2006) reported a change in hippocampal volume using similar MRI parameters (section thickness 750 μm and 1 mm) in a rat model of anxiety and in aging rats, respectively.…”

Can structural or functional changes following traumatic brain injury in the rat predict epileptic outcome?

“…Although these subtle findings reached statistical significance, we interpret them cautiously given that no other measures in the study comparing the epileptic and nonepileptic groups identified differences. Nonetheless, the strength of HDM‐LD and multivariate logistic regression analyses is their ability to detect subtle findings (Csernansky et al., ; Hogan et al., ). Therefore, the differences reported herein may indicate hippocampal abnormalities that occur at various time points post‐TBI that are involved in PTE.…”

“…Large‐deformation high‐dimensional mapping (HDM‐LD) of hippocampal morphometry was also completed as described previously (Hogan et al., ; Liu et al., ). HDM‐LD utilizes computer‐assisted shape recognition to identify patterns within MRI data (Bouilleret et al., ; Hogan et al., ). Computational anatomic techniques produce three‐dimensional surface representations of the hippocampus with resolution at a subvoxel level, enabling visualization of details of hippocampal surface anatomy (Gardner & Hogan, ).…”

Progressive Metabolic and Structural Cerebral Perturbations After Traumatic Brain Injury: An In Vivo Imaging Study in the Rat

“…HDM-LD utilizes the power of computer-assisted shape recognition to identify patterns within image data (16,17). Computational anatomic techniques produce 3-dimensional surface representations of the hippocampus with resolution at a subvoxel level, enabling visualization of details of hippocampal surface anatomy (18).…”

“…Changes in morphology can be detected even when total hippocampal volume changes are not significantly different (19)(20)(21)(22), using either visual analysis of deformation surfaces or multivariate ANOVA on the coefficients from eigenvector fields (23). Originally developed for human studies, this method has been adapted and validated for the assessment of rat hippocampus (16,17). Methods for comparing groups were as previously described (16).…”