R1ρ sensitivity to pH and other compounds at clinically accessible spin-lock fields in the presence of proteins

Nana Owusu; Casey P Johnson; William Kearney; Dan Thedens; John Wemmie; Vincent A Magnotta

doi:10.1002/nbm.4217

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Journal article

R1ρ sensitivity to pH and other compounds at clinically accessible spin-lock fields in the presence of proteins

Nana Owusu, Casey P Johnson, William Kearney, Dan Thedens, John Wemmie and Vincent A Magnotta

NMR in biomedicine, Vol.33(2), pp.e4217-n/a

02/2020

DOI: 10.1002/nbm.4217

PMCID: PMC7043777

PMID: 31742802

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https://www.ncbi.nlm.nih.gov/pmc/articles/7043777View

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Abstract

Numerous human diseases involve abnormal metabolism, and proton exchange is an effective source of magnetic resonance imaging (MRI) contrast for assessing metabolism. One MRI technique that capitalizes on proton exchange is R relaxation in the rotating frame (R ). Here, we investigated the sensitivity of R to various proton-exchange mechanisms at spin-lock pulses within Food and Drug Administration (FDA) safety guidelines for radiofrequency-induced heating. We systematically varied pH known to change the rate of proton exchange as well as the glucose and lysine concentrations, thus changing the number of amide, hydroxyl and amine exchangeable sites in a series of egg-white albumin phantoms. The resulting effects on quantitative relaxation time measurements of R , R and R were observed at 3 T. Using spin-lock amplitudes available for human imaging (less than 23.5 μT) at near physiologic temperatures, we found R was more sensitive to physiologic changes in pH than to changes in glucose and lysine concentrations. In addition, R was more sensitive to pH changes than R and R . Models of proton exchange fitted to the relaxation measurements suggest that amide groups were the primary source of pH sensitivity. Together, these experiments suggest an optimal spin-lock amplitude for measuring pH changes while not exceeding FDA-subject heating limitations.

Magnetic Resonance Imaging

Animals

Albumins - metabolism

Models, Biological

Chickens

Glucose - metabolism

Lysine - metabolism

Spin Labels

Egg White

Phantoms, Imaging

Circular Dichroism

Hydrogen-Ion Concentration

Details

Title: Subtitle: R1ρ sensitivity to pH and other compounds at clinically accessible spin-lock fields in the presence of proteins
Creators: Nana Owusu - Department of Biomedical Engineering, University of Iowa, Iowa City, Iowa, USA
Casey P Johnson - Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA
William Kearney - Department of Radiology, University of Iowa, Iowa City, Iowa, USA
Dan Thedens - Department of Radiology, University of Iowa, Iowa City, Iowa, USA
John Wemmie - Department of Psychiatry, University of Iowa, Iowa City, Iowa, USA
Vincent A Magnotta - Department of Psychiatry, University of Iowa, Iowa City, Iowa, USA
Resource Type: Journal article
Publication Details: NMR in biomedicine, Vol.33(2), pp.e4217-n/a
DOI: 10.1002/nbm.4217
PMID: 31742802
PMCID: PMC7043777
NLM abbreviation: NMR Biomed
ISSN: 0952-3480
eISSN: 1099-1492
Publisher: England
Grant note: I01 BX004440 / BLRD VA R01 EB022019 / NIBIB NIH HHS R01 MH111578 / NIMH NIH HHS
Language: English
Date published: 02/2020
Academic Unit: Roy J. Carver Department of Biomedical Engineering; Radiology; Electrical and Computer Engineering; Molecular Physiology and Biophysics; Psychiatry; Iowa Neuroscience Institute; Neurosurgery
Record Identifier: 9984066136902771

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