Demonstration of magnetization transfer and relaxation normalized pH-specific pulse-amide proton transfer imaging in an animal model of acute stroke

• Type of Material: Article
• Authors: Phillip Zhe Sun, Emory University
• Language: English
• Date: 2020-02-20
• Publisher: WILEY
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2020 International Society for Magnetic Resonance in Medicine
• Final Published Version (URL): http://dx.doi.org/10.1002/mrm.28223
• Title of Journal or Parent Work: MAGNETIC RESONANCE IN MEDICINE
• Volume: 84
• Issue: 3
• Start Page: 1526
• End Page: 1533
• Keywords: EXCHANGE; acute stroke; SATURATION-TRANSFER MRI; acidosis; TIME; TRANSFER CEST MRI; OPTIMIZATION; TISSUE ACIDIFICATION; QUANTITATIVE DESCRIPTION; chemical exchange saturation transfer (CEST); PENUMBRA; amide proton transfer (APT); Life Sciences & Biomedicine; pulse-CEST MRI; Radiology, Nuclear Medicine & Medical Imaging; SIMULATION; Science & Technology; ISCHEMIC-STROKE

Abstract

Purpose: pH-weighted amide proton transfer (APT) MRI is promising to serve as a new surrogate metabolic imaging biomarker for refined ischemic tissue demarcation. APT MRI with pulse-RF irradiation (pulse-APT) is an alternative to the routine continuous wave (CW-) APT MRI that overcomes the RF duty cycle limit. Our study aimed to generalize the recently developed pH-specific magnetization transfer and relaxation-normalized APT (MRAPT) analysis to pulse-APT MRI in acute stroke imaging. Methods: Multiparametric MRI, including CW- and pulse-APT MRI scans, were performed following middle cerebral artery occlusion in rats. We calculated pH-sensitive MTRasym and pH-specific MRAPT contrast between the ipsilateral diffusion lesion and contralateral normal area. Results: An inversion pulse of 10 to 15 ms maximizes the pH-sensitive MRI contrast for pulse-APT MRI. The contrast-to-noise ratio of pH-specific MRAPT effect between the contralateral normal area and ischemic lesion from both methods are comparable (3.25 ± 0.65 vs. 3.59 ± 0.40, P >.05). pH determined from both methods were in good agreement, with their difference within 0.1. Conclusions: Pulse-APT MRI provides highly pH-specific mapping for acute stroke imaging.