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Early experience of translating pH-weighted MRI to image human subjects at 3 Tesla
Phillip Zhe Sun1, Thomas Benner, William A Copen
1Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Athinoula A Martinos Center for Biomedical Imaging, Charlestown, Mass 02129, USA. pzhesun@nmr.mgh.harvard.edu
Background And Purpose:
In acute stroke, mismatch between lesions seen on diffusion- (DWI) and perfusion-weighted (PWI) MRI has been used to identify ischemic tissue before irreversible damage. Nevertheless, the concept of PWI/DWI mismatch is oversimplified and the ischemic tissue metabolic status and outcome are often heterogeneous. Tissue pH, a well-regulated physiological index that alters on disrupted tissue metabolism, may provide a surrogate metabolic imaging marker that augments the DWI and PWI for penumbra imaging.
Methods:
pH-weighted MRI was obtained by probing the pH-dependent amide proton transfer between endogenous mobile proteins/peptides and tissue water. The technique was validated using animal stroke models, optimized for human use, and preliminarily tested for imaging healthy volunteers.
Results:
pH-weighted MRI is sensitive and specific to ischemic tissue acidosis. pH MRI can be optimized for clinical use, and a pilot human study showed it is feasible using a standard 3 Tesla MRI scanner.
Conclusions:
Ischemic acidosis can be imaged via an endogenous pH-weighted MRI technique, which complements conventional PWI and DWI for penumbra imaging. pH-weighted MRI has been optimized and appears feasible and practical in imaging human subjects. Additional study is necessary to elucidate the diagnostic use of pH MRI in stroke patients.
Insights
New pH-weighted MRI can detect ischemic acidosis, complementing diffusion-weighted (DWI) and perfusion-weighted (PWI) imaging for stroke. This technique shows promise for identifying penumbra tissue in acute stroke patients.
Area of Science:
- Biomedical Imaging
- Neuroimaging
- Stroke Research
Background:
- Diffusion-weighted (DWI) and perfusion-weighted (PWI) MRI mismatch aids in identifying ischemic tissue in acute stroke.
- The PWI/DWI mismatch concept is limited by heterogeneous metabolic status and outcomes in ischemic tissue.
- Tissue pH offers a potential surrogate metabolic marker for imaging the penumbra, augmenting DWI and PWI.
Purpose of the Study:
- To introduce and validate an endogenous pH-weighted MRI technique for stroke imaging.
- To assess the feasibility and clinical potential of pH-weighted MRI in human subjects.
- To explore pH-weighted MRI as a complementary tool for penumbra imaging in acute stroke.
Main Methods:
- pH-weighted MRI was developed by measuring amide proton transfer between proteins/peptides and water.
- The technique was validated in animal stroke models.
- The method was optimized for human use and preliminarily tested in healthy volunteers using a 3 Tesla MRI scanner.
Main Results:
- pH-weighted MRI demonstrated sensitivity and specificity for detecting ischemic tissue acidosis.
- The pH MRI technique was optimized for clinical application.
- A pilot study confirmed the feasibility of using pH-weighted MRI in human subjects with standard MRI equipment.
Conclusions:
- Endogenous pH-weighted MRI can image ischemic acidosis, complementing DWI and PWI for penumbra imaging.
- The developed pH-weighted MRI technique is optimized, feasible, and practical for human imaging.
- Further research is required to establish the diagnostic utility of pH-weighted MRI in stroke patients.
