Quantitative brain relaxation atlases for personalized detection and characterization of brain pathology

• Published in: Magnetic resonance in medicine Vol. 83; no. 1; pp. 337 - 351
• Main Authors: Piredda, Gian Franco, Hilbert, Tom, Granziera, Cristina, Bonnier, Guillaume, Meuli, Reto, Molinari, Filippo, Thiran, Jean‐Philippe, Kober, Tobias
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.01.2020
• Subjects: Adult; Algorithms; Brain; Brain - diagnostic imaging; Brain Diseases - diagnostic imaging; Brain Mapping; Corpus callosum; Female; Healthy Volunteers; Humans; Image Processing, Computer-Assisted - methods; Lesions; Magnetic Resonance Imaging; Male; Middle Aged; Multiple sclerosis; Multiple Sclerosis - diagnostic imaging; Normalizing; normative atlases; Norms; Physical properties; quantitative MRI; Reference Values; Relaxation time; Reproducibility of Results; single‐subject comparisons; Substantia alba; T1 and T2 mapping; Telemetry; Tissues; Variability; White Matter - diagnostic imaging; Young Adult; quantitative MRI; normative atlases; single-subject comparisons; T1 and T2 mapping
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.27927

Purpose To exploit the improved comparability and hardware independency of quantitative MRI, databases of MR physical parameters in healthy tissue are required, to which tissue properties of patients can be compared. In this work, normative values for longitudinal and transverse relaxation times in the brain were established and tested in single‐subject comparisons for detection of abnormal relaxation times. Methods Relaxometry maps of the brain were acquired from 52 healthy volunteers. After spatially normalizing the volumes into a common space, T1 and T2 inter‐subject variability within the healthy cohort was modeled voxel‐wise. A method for a single‐subject comparison against the atlases was developed by computing z‐scores with respect to the established healthy norms. The comparison was applied to two multiple sclerosis and one clinically isolated syndrome cases for a proof of concept. Results The established atlases exhibit a low variation in white matter structures (median RMSE of models equal to 32 ms for T1 and 4 ms for T2), indicating that relaxation times are in a narrow range for normal tissues. The proposed method for single‐subject comparison detected relaxation time deviations from healthy norms in the example patient data sets. Relaxation times were found to be increased in brain lesions (mean z‐scores >5). Moreover, subtle and confluent differences (z‐scores ~2–4) were observed in clinically plausible regions (between lesions, corpus callosum). Conclusions Brain T1 and T2 quantitative norms were derived voxel‐wise with low variability in healthy tissue. Example patient deviation maps demonstrated good sensitivity of the atlases for detecting relaxation time alterations.