Quantification of the Brain Iron Metabolism in the Cognitively Declined Adults Using 7T MRI

Abstract

AbstractBackgroundThe extracellular aggregation of beta‐amyloid (AB) plaques is one of the hallmark pathology of Alzheimer’s diseases (AD) that develops years prior to clinical symptoms. However, inconsistency in the rate of cognitive decline among subjects with AB pathology and ineffectiveness of anti‐amyloid therapeutics to mitigate cognitive impairment suggest that other parameters, such as patterns of brain iron, may impact the risk of cognitive decline. In this study we leveraged improved MRI signal at 7T to explore susceptibility changes in the iron‐enriched regions among individuals with AD/MCI and healthy controls (HCs) through quantitative susceptibility mapping (QSM) with unprecedented resolution.MethodIn vivo MRI experiment was performed in AD/MCI and age‐matched healthy subjects. Scanning was conducted on a 7T MRI scanner using 1Tx/32Rx Nova head coil. To calculate QSM, a 3D high‐resolution spoiled gradient echo (GRE) sequence was used (voxels size = 0.3×0.3×1.5 mm3). QSM was used to measure susceptibility in the major iron‐enriched structures (Fig. 1), including red nucleus (RN), substantia nigra (SN), globus pallidus (GP), Caudate nucleolus (CN), putamen (PT), and dentate nucleus (DN).ResultWe found a significantly higher magnetic susceptibility in GP and DN in patients with AD/MCI compared with HCs (Fig. 2). Overall mean susceptibility values for the RN, SN, CN, GP, PT, and DN in AD/MCI and HCs is summarized in Table 1. In AD/MCI the highest susceptibility values were found in the GP (233.5±12.7) and DN (214.7±10.4), verses 174.6±11.8 and 168.9±11.6 for GP and DN in the HCs, respectively. There were small differences in the susceptibility values between the other ROIs.ConclusionWe reported an initial result for QSM at 7T in the AD/MCI subjects and appropriate age matched HCs. The main aim of the study was to investigate whether susceptibility values measured using ultra‐high resolution QSM differ in the iron‐enriched regions between these two populations. A significant susceptibility value was reported in the AD/MCI compared with the HC in GP and DN regions. This observation clearly deserves further investigations in larger cohorts.