The microstructural correlates of T1 in white matter

• Published in: Magnetic resonance in medicine Vol. 75; no. 3; pp. 1341 - 1345
• Main Authors: Harkins, Kevin D., Xu, Junzhong, Dula, Adrienne N., Li, Ke, Valentine, William M., Gochberg, Daniel F., Gore, John C., Does, Mark D.
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.03.2016; Wiley Subscription Services, Inc
• Subjects: Animals; Attention deficit hyperactivity disorder; axon size; Axons - ultrastructure; Brain; Correlation analysis; Female; Humans; Image Processing, Computer-Assisted - methods; In vivo methods and tests; Magnetic Resonance Imaging - methods; Male; Measurement methods; Microstructure; MRI; Myelin; Myelination; Porous media; rat; Rats; Rats, Sprague-Dawley; Size effects; Spinal cord; Spinal Cord - diagnostic imaging; Substantia alba; White Matter - anatomy & histology; White Matter - cytology; White Matter - diagnostic imaging; White Matter - ultrastructure; microstructure; spinal cord; rat; MRI; T1; axon size
• ISSN: 0740-3194; 1522-2594; 1522-2594
• DOI: 10.1002/mrm.25709

Purpose Several studies have shown strong correlations between myelin content and T1 within the brain, and have even suggested that T1 can be used to estimate myelin content. However, other micro‐anatomical features such as compartment size are known to affect longitudinal relaxation rates, similar to compartment size effects in porous media. Methods T1 measurements were compared with measured or otherwise published axon size measurements in white matter tracts of the rat spinal cord, rat brain, and human brain. Results In both ex vivo and in vivo studies, correlations were present between the relaxation rate 1/T1 and axon size across regions of rat spinal cord with nearly equal myelin content. Conclusion While myelination is likely the dominant determinant of T1 in white matter, variations in white matter microstructure, independent of myelin volume fraction, may also be reflected in T1 differences between regions or subjects. Magn Reson Med 75:1341–1345, 2016. © 2015 Wiley Periodicals, Inc.