Neuroimaging and verbal memory assessment in healthy aging adults using a portable low-field MRI scanner and a web-based platform: results from a proof-of-concept population-based cross-section study

Abstract

Consumer wearables and health monitors, internet-based health and cognitive assessments, and at-home biosample (e.g., saliva and capillary blood) collection kits are increasingly used by public health researchers for large population-based studies without requiring intensive in-person visits. Alongside reduced participant time burden, remote and virtual data collection allows the participation of individuals who live long distances from hospital or university research centers, or who lack access to transportation. Unfortunately, studies that include magnetic resonance neuroimaging are challenging to perform remotely given the infrastructure requirements of MRI scanners, and, as a result, they often omit socially, economically, and educationally disadvantaged individuals. Lower field strength systems (< 100 mT) offer the potential to perform neuroimaging at a participant's home, enabling more accessible and equitable research. Here we report the first use of a low-field MRI "scan van" with an online assessment of paired-associate learning (PAL) to examine associations between brain morphometry and verbal memory performance. In a sample of 67 individuals, 18-93 years of age, imaged at or near their home, we show expected white and gray matter volume trends with age and find significant (p < 0.05 FWE) associations between PAL performance and hippocampus, amygdala, caudate, and thalamic volumes. High-quality data were acquired in 93% of individuals, and at-home scanning was preferred by all individuals with prior MRI at a hospital or research setting. Results demonstrate the feasibility of remote neuroimaging and cognitive data collection, with important implications for engaging traditionally under-represented communities in neuroimaging research.

Keywords: Brain MRI; Dementia; Diversity in health research; Low-field MRI; Remote data collection, aging; Web-based cognitive assessment.

Fig. 1

Example photos of the Scan-Van at participant homes. Participants enter the van from the rear doors. The side door can be opened to reduce claustrophobia, allow extra cooling, or just improve the general participant experience

Fig. 2

Example comparison of standard T₁-weighted IR-FSE and T₂-weighted FSE images acquired in three volunteers from across the lifespan. Overall, we have found the T2-FSE images provide improved and more consistent image quality

Fig. 3

Developed study template and regional tissue and sub-cortical structural masks. A custom study template was created using 26 study participants chosen uniformly cross the age range from 20 to 94 years of age and evenly split by male and female. White matter (green), Gray matter (blue) and CSF (red) masks were developed using the MNI structural atlas as priors and refined using ANTS Atropos. Subcortical deep brain masks were also constructed using the Oxford-Harvard subcortical atlas with Thalamus (yellow with red outline), Putamen (light blue), Globus Pallidus (dark blue), Caudate nucleus (purple with blue outline), Hippocampus (green) and Amygdala (white with pink outline)

Fig. 4

Example data collected from a 25 and 78 year-old participant, including aligned tissue and deep brain structure masks

Fig. 5

The number of correct word pairs as a function of participant age with and without adjusting for education level. The dotted lines correspond to the 95% confidence interval

Fig. 6

Representative plots of percent white and gray matter volume as a function of individual age with and without adjusting for education level. The dotted lines correspond to the 95% confidence interval

Fig. 7

Exploratory voxel-based morphometry analysis examining associations between gray matter density and PAL score, controlling for subject age, biological sex, and education attainment. Highlighted regions denote significant associations (corrected for multiple comparisons using threshold-free cluster enhancement)

Fig. 8

Results of the regional volume analysis. For each region, we plot the measured PAL scored vs. age as well as the predicted PAL score calculated from the estimated regression model

Fig. 9

Results of the regional volume analysis. For each region, we plot the measured PAL scored vs. the predicted PAL score calculated from the estimated regression model

Fig. 10

Blad-Altman plots showing the differences in whole-brain white and regional left-hemisphere putamen, amygdala, and hippocampus volumes measured from T₂-weighted low-field data and conventional T₁-weighted 3 T data in 15 adult individuals. No significant non-zero bias is observed between the sets of measures