Hippocampal subfield volume in relation to cerebrospinal fluid Amyloidβ1‐42 in early Alzheimer’s disease: A 7T MRI study

Abstract

AbstractBackground7T MRI can provide high contrast and spatial resolution images for studying the volume of hippocampal subfields which can be used in conjunction with Amyloidβ1‐42 and tau measures in the cerebrospinal fluid (CSF) to provide a non‐invasive alternative marker for Alzheimer’s disease (AD).Method41 participants (20 AD and 21 healthy age‐ and gender‐matched controls) were recruited [aged 40 ‐ 76 years; 64% female). The protocol for the analysis of the CSF for the Amyloidβ1‐42 (reference range: 627‐1322 pg/ml), total tau (reference range: 146‐595 pg/ml), Thr181‐phosphorylated tau (reference range <68 pg/ml) have been previously published (Hosseini et al, 2022) and the measures were used for the ATN classification of Alzheimer’s disease. Imaging was carried out on a Philips Achieva 7T scanner using a Nova Medical (Wilmington MA, USA) single‐channel transmit, 32‐channel receive (1Tx32Rx) head coil. Images acquired are PSIR (TE/TR = 3.1/6.9ms; FA = 6o, isotropic 0.55 mm resolution) and T2‐weighted FSE (TE/TR = 119/59001ms, FA = 90o, 0.38×0.39×1.50 mm3 resolution).ResultFig 1 show the T2‐weighted image and the segmentation of the hippocampus obtained using ASHS (Yushkevich et al., 2015b)There was a significant decrease in the volume of each hippocampal subfield (Fig2) in AD patients compared to controls. The change in volume was not significant for the whole brain showing that the hippocampal volume loss was not simply part of general brain atrophy.There was an approximately linear relationship between the CSF Amyloidβ1‐42 and volume of the hippocampus for the AD participants (Fig 3). A positive linear relationship was observed in all the subfields of the hippocampus but a statistically significant relation was only achieved in the Entorhinal Cortex (ERC) [p<0.022, r = 0.508].The ERC is known to represent perception of time, memory and navigation (Tsao et al., 2018)(Du et al., 2001), and AD pathology may start from the ERC before migrating along the hippocampus (Braak & Braak, 1997). Further, the ERC volume loss on 1.5 T MRI has been reported greater in AD as compared with Mild Cognitive Impairment(Du et al., 2001).ConclusionThe association of the volume of ERC and CSF Amyloidβ1‐42 suggests the potential for using 7T MRI as a biomarker for an early identification of AD.