White Matter Hyperintensities on 1.5 and 3 Tesla Brain MRI in Healthy Individuals

Abstract

Background : White matter hyperintensities (WMH) on T2-weighted magnetic resonance imaging (MRI) are frequent incidental findings in brains of asymptomatic healthy individuals (HI). The morphological and spatial distribution of these WMH between standard 1.5T scanners and increasingly available 3T scanners in a large population of HI in clinical routine settings has not been investigated. Objectives: To investigate the effect of changing from a 1.5T to a 3T MRI scanner on the number, volume and spatial distribution of WMH on brain MRI in a population of clinically HI. Materials and Methods: Fifty-three (53) HI were examined using T2 weighted sequences on both 1.5T and 3T within one week in a random order. The WMH were outlined semi-automatically by two blinded operators. Number and volume of WMH were calculated. Spatial lesion distribution was assessed using WMH probability maps (WMHPM). Paired-wise analysis examined the proportion of WMH not found on 1.5T and/or 3T. A posteriori unblinded analysis was conducted to examine the non-overlapping identifications of WMH between the 1.5T and 3T. Results : For paired-wise WMH analysis, 3T showed significantly higher WMH number and individual volume compared to 1.5 T ( p <0.001). Logistic regression analysis showed that likelihood of missing WMH on 1.5T was significantly higher for smaller WMH. WMHPM revealed spatial WMH differences on 3T compared to 1.5T, with WMH more pronounced in the occipital regions with higher field strength. Conclusion: This study showed that use of higher magnetic field strength identified more WMH in healthy subjects with respect to both morphological and spatial characteristics. These WMH do not necessarily represent pathology; however, these findings should be taken into account in lesion segmentation on a 3T MRI and might suggest the use of universally accepted guidelines for lesions’ segmentation on higher magnetic field, especially when it is executed by different operators and/or centers.