Tissue characterization using R dispersion imaging at low locking fields.

Fatemeh Adelnia, Zhongliang Zu, John T Spear, Feng Wang, Kevin D Harkins, John C Gore

Journal: Magnetic resonance imaging 2022;84():1-11

PMID: 34052306

Full Text on Elsevier Science View on PubMed

Abstract

Measurements of the variations of spin-locking relaxation rates (R) with locking field amplitude allow the derivation of quantitative parameters that describe different dynamic processes, such as slow molecular motions, chemical exchange and diffusion. In some samples, changes in R values between locking frequency 0 and 200 Hz may be dominated mainly by diffusion of water in intrinsic field gradients, while those at higher locking fields are due to exchange processes. The exchange and diffusion effects act independently of each other, as confirmed by simulation and experimentally. In tissues, the relevant intrinsic field gradients may arise from the magnetic inhomogeneities caused by microvascular blood so that R dispersion over weak locking field amplitudes (≤ 200 Hz) is affected by changes in capillary density and geometry. Here we first review the theoretical and experimental background to the interpretation of R dispersions caused by intrinsic magnetic susceptibility variations within the tissue. We then provide new empirical results of R dispersion imaging of the human brain and skeletal muscle at low locking field amplitudes for the first time and identify potential applications of R dispersion imaging in clinical studies.

Address: Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA.; Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA.; Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA.; Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA; Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA. Electronic address: [email protected].

DOI: 10.1016/j.mri.2021.05.006

Link outs

Free resources

Medical:

https://medlineplus.gov/mriscans.html

Other Literature Sources:

Subscription / membership required

Full Text Sources:

MeSH Terms: Computer Simulation, Diffusion, Humans, Image Enhancement, Magnetic Resonance Imaging, Water