Evaluation of common structural brain changes in aging and Alzheimer disease with the use of an MRI-based brain atrophy and lesion index: a comparison between T1WI and T2WI at 1.5T and 3T.

Abstract

The Brain Atrophy and Lesion Index combines several common, aging-related structural brain changes and has been validated for high-field MR imaging. In this study, we evaluated measurement properties of the Brain Atrophy and Lesion Index by use of T1WI and T2WI at 1.5T and 3T MR imaging to comprehensively assess the usefulness of the lower field-strength testing. Data were obtained from the Alzheimer's Disease Neuroimaging Initiative. Images of subjects (n = 127) who had T1WI and T2WI at both 3T and 1.5T on the same day were evaluated, applying the Brain Atrophy and Lesion Index rating. Criterion and construct validity and interrater agreement were tested for each field strength and image type. Regarding reliability, the intraclass correlation coefficients for the Brain Atrophy and Lesion Index score were consistently high (>0.81) across image type and field strength. Regarding construct validity, the Brain Atrophy and Lesion Index score differed among diagnostic groups, being lowest in people without cognitive impairment and highest in those with Alzheimer disease (F > 5.14; P < .007). Brain Atrophy and Lesion Index scores correlated with age (r > 0.37, P < .001) and cognitive performance (r > 0.38, P < .001) and were associated with positive amyloid-β test (F > 3.96, P < .050). The T1WI and T2WI Brain Atrophy and Lesion Index scores were correlated (r > 0.93, P < .001), with the T2WI scores slightly greater than the T1WI scores (F > 4.25, P < .041). Regarding criterion validation of the 1.5T images, the 1.5T scores were highly correlated with the 3T Brain Atrophy and Lesion Index scores (r > 0.93, P < .001). The higher field and T2WI more sensitively detect subtle changes in the deep white matter and perivascular spaces in particular. Even so, 1.5T Brain Atrophy and Lesion Index scores are similar to those obtained by use of 3T images. The Brain Atrophy and Lesion Index may have use in quantifying the impact of dementia on brain structures.