Hippocampal profiling: Localized magnetic resonance imaging volumetry and T2 relaxometry for hippocampal sclerosis

Abstract

Objective Hippocampal sclerosis (HS) is the most common cause of drug‐resistant temporal lobe epilepsy, and its accurate detection is important to guide epilepsy surgery. Radiological features of HS include hippocampal volume loss and increased T2 signal, which can both be quantified to help improve detection. In this work, we extend these quantitative methods to generate cross‐sectional area and T2 profiles along the hippocampal long axis to improve the localization of hippocampal abnormalities. Methods T1‐weighted and T2 relaxometry data from 69 HS patients (32 left, 32 right, 5 bilateral) and 111 healthy controls were acquired on a 3‐T magnetic resonance imaging (MRI) scanner. Automated hippocampal segmentation and T2 relaxometry were performed and used to calculate whole‐hippocampal volumes and to estimate quantitative T2 (qT2) values. By generating a group template from the controls, and aligning this so that the hippocampal long axes were along the anterior‐posterior axis, we were able to calculate hippocampal cross‐sectional area and qT2 by a slicewise method to localize any volume loss or T2 hyperintensity. Individual patient profiles were compared with normative data generated from the healthy controls. Results Profiling of hippocampal volumetric and qT2 data could be performed automatically and reproducibly. HS patients commonly showed widespread decreases in volume and increases in T2 along the length of the affected hippocampus, and focal changes may also be identified. Patterns of atrophy and T2 increase in the left hippocampus were similar between left, right, and bilateral HS. These profiles have potential to distinguish between sclerosis affecting volume and qT2 in the whole or parts of the hippocampus, and may aid the radiological diagnosis in uncertain cases or cases with subtle or focal abnormalities where standard whole‐hippocampal measurements yield normal values. Significance Hippocampal profiling of volumetry and qT2 values can help spatially localize hippocampal MRI abnormalities and work toward improved sensitivity of subtle focal lesions.

Cortical Changes in Epilepsy Patients With Focal Cortical Dysplasia: New Insights With T2 Mapping

“…In addition, qMRI data can help to distinguish between patients with TLE and healthy subjects 15,16 . Furthermore, hippocampal profiling using volumetry and T 2 values aids to spatially localize hippocampal MRI abnormalities 17 . Reeves et al 18 described T 1 and T 2 * differences between the FCD region of interest in white matter (WM) and normal‐appearing WM and magnetization transfer ratio changes in cortical GM inside FCDs, indicating microstructural abnormalities; however, the normal‐appearing cortex was not investigated for abnormalities.…”

Clinical evaluation of automated quantitative MRI reports for assessment of hippocampal sclerosis

“…A normative dataset of 111 healthy controls (age 40.0 ± 12.8, range 17.0-66.6 years; 52 men) was created from subjects on the same scanner and same protocol, as detailed in Vos et al, [17].…”

“…Implementation within a quality management framework is ongoing Step 6-in-use evaluation -Future work includes clinical and health economic impact normative reference ranges for total hippocampal volume, qT2 and left:right total hippocampal volume, and T2 ratios. Additionally, we have created novel hippocampal profiles [17] by producing group templates for the control population, aligning them to the long axis of the hippocampus and calculating cross-sectional area and qT2 for each subject, contextualised with normative reference data. The quantitative report (QReport) displays non-identifying demographics (age, gender, scan date, scanner type, hospital), quality control measures, global volume of each hippocampus as well as hippocampus volume, and qT2 values along its long axis.…”

“…We developed and technically validated an automated pipeline, combining the two algorithms for the quantification of both hippocampal volume and T2 (qT2) [15,16]. We encoded the pipeline's output into a quantitative report (step 3), which includes novel representations of measures or 'profiles' along the anterior-posterior longitudinal axis of the hippocampus [17].…”

MR relaxometry-based analysis of brain hemorrhages: an experimental study on a rabbit model

“…In human medicine, the MRR role has been thoroughly investigated, for example in brain neoplasia, where this technique improved the lesion identification, especially when monitoring the chemotherapy response [5][6][7][8][9]. Many reports are also available on the application of this technique on epileptic patients, with the result of optimizing and enhancing lesion depiction [10,11,[11][12][13][14][15]. In the case of neurodegenerative disorders, MRR resulted useful to improve the detection of early degeneration areas [16][17][18].…”