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Comparing different analysis methods for quantifying the MRI amide proton transfer (APT) effect in hyperacute stroke patients

Tee, Y. K.; Harston, G. W. J.; Blockley, N.; Okell, Thomas W.; Levman, J.; Sheerin, F.; Cellerini, M.; Jezzard, P.; Kennedy, J.; Payne, S. J.; Chappell, M. A.

Comparing different analysis methods for quantifying the MRI amide proton transfer (APT) effect in hyperacute stroke patients Thumbnail


Y. K. Tee

G. W. J. Harston

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Assistant Professor

Thomas W. Okell

J. Levman

F. Sheerin

M. Cellerini

P. Jezzard

J. Kennedy

S. J. Payne

M. A. Chappell


Amide proton transfer (APT) imaging is a pH mapping method based on the chemical exchange saturation transfer phenomenon that has potential for penumbra identification following stroke. The majority of the literature thus far has focused on generating pH‐weighted contrast using magnetization transfer ratio asymmetry analysis instead of quantitative pH mapping. In this study, the widely used asymmetry analysis and a model‐based analysis were both assessed on APT data collected from healthy subjects (n = 2) and hyperacute stroke patients (n = 6, median imaging time after onset = 2 hours 59 minutes). It was found that the model‐based approach was able to quantify the APT effect with the lowest variation in grey and white matter (≤ 13.8 %) and the smallest average contrast between these two tissue types (3.48 %) in the healthy volunteers. The model‐based approach also performed quantitatively better than the other measures in the hyperacute stroke patient APT data, where the quantified APT effect in the infarct core was consistently lower than in the contralateral normal appearing tissue for all the patients recruited, with the group average of the quantified APT effect being 1.5 ± 0.3 % (infarct core) and 1.9 ± 0.4 % (contralateral). Based on the fitted parameters from the model‐based analysis and a previously published pH and amide proton exchange rate relationship, quantitative pH maps for hyperacute stroke patients were generated, for the first time, using APT imaging.

Journal Article Type Article
Acceptance Date May 7, 2014
Online Publication Date Jun 10, 2014
Publication Date 2014-09
Deposit Date Dec 10, 2018
Publicly Available Date Apr 3, 2019
Journal NMR in Biomedicine
Print ISSN 0952-3480
Electronic ISSN 1099-1492
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 27
Issue 9
Pages 1019-1029
Keywords Amide proton transfer (APT) imaging; chemical exchange saturation transfer (CEST) imaging; magnetization transfer (MT) imaging; pH; MRI; stroke
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