Dependence of brain‐tissue R 2 on MRI field strength

To quantify T relaxation in the brain at 3 T and 7 T to study its field dependence and correlation with iron content, and to investigate whether iron can be separated from other sources of T relaxation based on this field dependence. Nine subjects were scanned at both field strengths with the same a...

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Bibliographic Details
Published inMagnetic resonance in medicine Vol. 93; no. 5; pp. 2140 - 2152
Main Authors van Gelderen, Peter, Wang, Yicun, de Zwart, Jacco A., Duyn, Jeff H.
Format Journal Article
LanguageEnglish
Published United States 01.05.2025
Subjects
Adult
Algorithms
Brain - anatomy & histology
Brain - diagnostic imaging
Brain - metabolism
Female
Humans
Image Interpretation, Computer-Assisted - methods
Iron - analysis
Iron - metabolism
Magnetic Resonance Imaging - methods
Male
Reproducibility of Results
Sensitivity and Specificity
transverse relaxation
brain iron
T2
T2 field dependence
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Summary:To quantify T relaxation in the brain at 3 T and 7 T to study its field dependence and correlation with iron content, and to investigate whether iron can be separated from other sources of T relaxation based on this field dependence. Nine subjects were scanned at both field strengths with the same acquisition technique, which used multiple gradient-echo sampling of a spin echo. This allowed for separation of T relaxation from static dephasing by B field inhomogeneities and the effects of radiofrequency refocusing imperfections. The average relaxation rates (R  = 1/T ) in multiple regions of interest in the brain were fitted with a model linear in B and correlated with literature iron values. The relationship between the R values at the two field strengths appeared to be linear over all regions of interest. The R values (in s ) in the regions of interest for which both an iron and a lipid mass fraction have been documented in the literature were fitted as , where and indicate the putative mass fractions of iron and lipid. The R relaxation rate is well described by a constant plus a term linear in B , with both iron and lipid content contributing to the slope. This indicates that the contributions of lipid and iron to R cannot be separated based solely on the field dependence of R in the field range of 3-7 T.
ISSN:0740-3194
1522-2594
DOI:10.1002/mrm.30400