Spin‐lock imaging of early tissue pH changes in ischemic rat brain

Spin‐lock imaging of early tissue pH changes in ischemic rat brain We have previously reported that the dispersion of spin‐lattice relaxation rates in the rotating frame (R1ρ) of tissue water protons at high field can be dominated by chemical exchange contributions. Ischemia in brain causes changes in tissue pH, which in turn may affect proton exchange rates. Amide proton transfer (APT, a form of chemical exchange saturation transfer) has been shown to be sensitive to chemical exchange rates and able to detect pH changes non‐invasively following ischemic stroke. However, the specificity of APT to pH changes is decreased because of the influence of several other factors that affect magnetization transfer. R1ρ is less influenced by such confounding factors and thus may be more specific for detecting variations in pH. Here, we applied a spin‐locking sequence to detect ischemic stroke in animal models. Although R1ρ images acquired with a single spin‐locking amplitude (ω1) have previously been used to assess stroke, here we use ΔR1ρ, which is the difference in R1ρ values acquired with two different locking fields to emphasize selectively the contribution of chemical exchange effects. Numerical simulations with different exchange rates and measurements of tissue homogenates with different pH were performed to evaluate the specificity of ΔR1ρ to detect tissue acidosis. Spin‐lock and APT data were acquired on five rat brains after ischemic strokes induced via middle cerebral artery occlusions. Correlations between these data were analyzed at different time points after the onset of stroke. The results show that ΔR1ρ (but not R1ρ acquired with a single ω1) was significantly correlated with APT metrics consistent with ΔR1ρ varying with pH. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png NMR in Biomedicine (Electronic) Wiley

Spin‐lock imaging of early tissue pH changes in ischemic rat brain

Loading next page...
 
/lp/wiley/spin-lock-imaging-of-early-tissue-ph-changes-in-ischemic-rat-brain-C0hy0XC26K
Publisher
Wiley Subscription Services, Inc., A Wiley Company
Copyright
Copyright © 2018 John Wiley & Sons, Ltd.
ISSN
0952-3480
eISSN
1099-1492
D.O.I.
10.1002/nbm.3893
Publisher site
See Article on Publisher Site

Abstract

We have previously reported that the dispersion of spin‐lattice relaxation rates in the rotating frame (R1ρ) of tissue water protons at high field can be dominated by chemical exchange contributions. Ischemia in brain causes changes in tissue pH, which in turn may affect proton exchange rates. Amide proton transfer (APT, a form of chemical exchange saturation transfer) has been shown to be sensitive to chemical exchange rates and able to detect pH changes non‐invasively following ischemic stroke. However, the specificity of APT to pH changes is decreased because of the influence of several other factors that affect magnetization transfer. R1ρ is less influenced by such confounding factors and thus may be more specific for detecting variations in pH. Here, we applied a spin‐locking sequence to detect ischemic stroke in animal models. Although R1ρ images acquired with a single spin‐locking amplitude (ω1) have previously been used to assess stroke, here we use ΔR1ρ, which is the difference in R1ρ values acquired with two different locking fields to emphasize selectively the contribution of chemical exchange effects. Numerical simulations with different exchange rates and measurements of tissue homogenates with different pH were performed to evaluate the specificity of ΔR1ρ to detect tissue acidosis. Spin‐lock and APT data were acquired on five rat brains after ischemic strokes induced via middle cerebral artery occlusions. Correlations between these data were analyzed at different time points after the onset of stroke. The results show that ΔR1ρ (but not R1ρ acquired with a single ω1) was significantly correlated with APT metrics consistent with ΔR1ρ varying with pH.

Journal

NMR in Biomedicine (Electronic)Wiley

Published: Jan 1, 2018

Keywords: ; ; ;

References

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 12 million articles from more than
10,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Unlimited reading

Read as many articles as you need. Full articles with original layout, charts and figures. Read online, from anywhere.

Stay up to date

Keep up with your field with Personalized Recommendations and Follow Journals to get automatic updates.

Organize your research

It’s easy to organize your research with our built-in tools.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

Monthly Plan

  • Read unlimited articles
  • Personalized recommendations
  • No expiration
  • Print 20 pages per month
  • 20% off on PDF purchases
  • Organize your research
  • Get updates on your journals and topic searches

$49/month

Start Free Trial

14-day Free Trial

Best Deal — 39% off

Annual Plan

  • All the features of the Professional Plan, but for 39% off!
  • Billed annually
  • No expiration
  • For the normal price of 10 articles elsewhere, you get one full year of unlimited access to articles.

$588

$360/year

billed annually
Start Free Trial

14-day Free Trial