Use of T1‐weighted/T2‐weighted magnetic resonance ratio images to elucidate changes in the schizophrenic brain

Abstract

IntroductionOne leading hypothesis suggests that schizophrenia (SZ) is a neurodevelopmental disorder caused by genetic defects in association with environmental risk factors that affect synapse and myelin formation. Recent magnetic resonance imaging (MRI) studies of SZ brain showed both gray matter (GM) reduction and white matter (WM) fractional anisotropy reduction. In this study, we used T1‐weighted (T1w)/T2‐weighted (T2w) MRI ratio images, which increase myelin‐related signal contrast and reduce receiver‐coil bias.MethodsWe measured T1w/T2w ratio image signal intensity in 29 patients with SZ and 33 healthy controls (HCs), and then compared them against bias‐corrected T1w images.ResultsMean T1w/T2w ratio signal intensity values across all SZ GM and WM voxels were significantly lower than those for the HC values (analysis of covariance with age, gender, handedness, and premorbid intelligence quotient as nuisance covariates). SZ mean WM T1w/T2w ratio values were related to Global Assessment of Functioning (GAF) scores and were inversely related to the positive psychotic symptoms of the Positive and Negative Syndrome Scale. Voxel‐based analysis revealed significantly lower T1w/T2w ratio image signal intensity values in the right ventral putamen in SZ GM. T1w image intensities did not differ between the SZ and HC groups.ConclusionsT1‐weighted/T2‐weighted ratio imaging increased the detectability of SZ pathological changes. Reduced SZ brain signal intensity is likely due to diminished myelin content; therefore, mapping myelin‐related SZ brain changes using T1w/T2w ratio images may be useful for studies of SZ brain abnormalities.

Gray matter T1‐w/T2‐w ratios are higher in Alzheimer's disease

“…Disorders with a strong demyelinating component such as MS, have consistently showed lower T1‐w/T2‐w values in pathologically vulnerable regions (Beer et al, ; Nakamura et al, ; Righart et al, ). Additionally, lowered T1‐w/T2‐w ratios in several brain regions in schizophrenia (Ganzetti et al, ; Iwatani et al, ) and bipolar disorder patients (Ishida et al, ) have been identified. Recent transcriptomic studies have further observed correlations of the T1‐w/T2‐w intensity in the cortex with expression of genes associated with cortical microcircuit specialization and myelin (Burt et al, ; Ritchie, Pantazatos, & French, ).…”

Regionally specific changes in the hippocampal circuitry accompany progression of cerebrospinal fluid biomarkers in preclinical Alzheimer's disease

“…In addition to hippocampal morphology, we evaluated the T1w/FLAIR signal intensity ratio to probe differences in extra‐hippocampal white matter microstructure. A similar contrast (T1w/T2w) has been recently used to map the myelin content of the cerebral cortex (Glasser and Van Essen, ), and study the effects of ageing (Grydeland, Walhovd, Tamnes, Westlye, & Fjell, ) and disease (Ganzetti, Wenderoth, & Mantini, ; Iwatani et al, ). T1‐weighted and FLAIR images include spatial biases that vary between subjects due to imperfections in the image acquisition techniques, which confound the analysis of T1‐weighted and FLAIR signal intensities.…”

Can T1w/T2w ratio be used as a myelin‐specific measure in subcortical structures? Comparisons between FSE‐based T1w/T2w ratios, GRASE‐based T1w/T2w ratios and multi‐echo GRASE‐based myelin water fractions

“…Conversely, methods such as T 1 w/ T 2 w ratio mapping, derived by dividing T 1 w by T 2 w images after basic preprocessing and signal calibration, are technically straightforward, generally have adequate SNR and are highly stable/reliable . Nonetheless, despite the apparent sensitivity to WM microstructural changes, initial claims that this method could be used to assess myelin content have been challenged in more recent studies, suggesting that the T 1 w/ T 2 w ratio more likely represents a general measure of WM microstructure, including myelination, inflammation and other factors …”