A comparison of exogenous and endogenous CEST MRI methods for evaluating in vivo pH

Leila R. Lindeman; Edward A. Randtke; Rachel A. High; Kyle M. Jones; Christine M. Howison; Mark D. Pagel

doi:10.1002/mrm.26924

A comparison of exogenous and endogenous CEST MRI methods for evaluating in vivo pH

Leila R. Lindeman, Edward A. Randtke, Rachel A. High, Kyle M. Jones, Christine M. Howison, Mark D. Pagel

Research output: Contribution to journal › Article › peer-review

48 Scopus citations

Abstract

Purpose: Extracellular pH (pHe) is an important biomarker for cancer cell metabolism. Acido-chemical exchange saturation transfer (CEST) MRI uses the contrast agent iopamidol to create spatial maps of pHe. Measurements of amide proton transfer exchange rates (k_ex) from endogenous CEST MRI were compared to pHe measurements by exogenous acido-CEST MRI to determine whether endogenous k_ex could be used as a proxy for pHe measurements. Methods: Spatial maps of pHe and k_ex were obtained using exogenous acidoCEST MRI and an endogenous CEST MRI analyzed with the omega plot method, respectively, to evaluate mouse kidney, a flank tumor model, and a spontaneous lung tumor model. The pHe and k_ex results were evaluated using pixelwise comparisons. Results: The k_ex values obtained from endogenous CEST measurements did not correlate with the pHe results from exogenous CEST measurements. The k_ex measurements were limited to fewer pixels and had a limited dynamic range relative to pHe measurements. Conclusion: Measurements of k_ex with endogenous CEST MRI cannot substitute for pHe measurements with acidoCEST MRI. Whereas endogenous CEST MRI may still have good utility for evaluating some specific pathologies, exogenous acido-CEST MRI is more appropriate when evaluating pathologies based on pHe values. Magn Reson Med 79:2766–2772, 2018.

Original language	English (US)
Pages (from-to)	2766-2772
Number of pages	7
Journal	Magnetic resonance in medicine
Volume	79
Issue number	5
DOIs	https://doi.org/10.1002/mrm.26924
State	Published - May 2018
Externally published	Yes

Keywords

CEST MRI
lung imaging
tumor acidosis

ASJC Scopus subject areas

Radiology Nuclear Medicine and imaging

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10.1002/mrm.26924

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title = "A comparison of exogenous and endogenous CEST MRI methods for evaluating in vivo pH",

abstract = "Purpose: Extracellular pH (pHe) is an important biomarker for cancer cell metabolism. Acido-chemical exchange saturation transfer (CEST) MRI uses the contrast agent iopamidol to create spatial maps of pHe. Measurements of amide proton transfer exchange rates (kex) from endogenous CEST MRI were compared to pHe measurements by exogenous acido-CEST MRI to determine whether endogenous kex could be used as a proxy for pHe measurements. Methods: Spatial maps of pHe and kex were obtained using exogenous acidoCEST MRI and an endogenous CEST MRI analyzed with the omega plot method, respectively, to evaluate mouse kidney, a flank tumor model, and a spontaneous lung tumor model. The pHe and kex results were evaluated using pixelwise comparisons. Results: The kex values obtained from endogenous CEST measurements did not correlate with the pHe results from exogenous CEST measurements. The kex measurements were limited to fewer pixels and had a limited dynamic range relative to pHe measurements. Conclusion: Measurements of kex with endogenous CEST MRI cannot substitute for pHe measurements with acidoCEST MRI. Whereas endogenous CEST MRI may still have good utility for evaluating some specific pathologies, exogenous acido-CEST MRI is more appropriate when evaluating pathologies based on pHe values. Magn Reson Med 79:2766–2772, 2018.",

keywords = "CEST MRI, lung imaging, tumor acidosis",

author = "Lindeman, {Leila R.} and Randtke, {Edward A.} and High, {Rachel A.} and Jones, {Kyle M.} and Howison, {Christine M.} and Pagel, {Mark D.}",

note = "Publisher Copyright: {\textcopyright} 2017 International Society for Magnetic Resonance in Medicine",

year = "2018",

month = may,

doi = "10.1002/mrm.26924",

language = "English (US)",

volume = "79",

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AU - Lindeman, Leila R.

AU - Randtke, Edward A.

AU - High, Rachel A.

AU - Jones, Kyle M.

AU - Howison, Christine M.

AU - Pagel, Mark D.

PY - 2018/5

Y1 - 2018/5

N2 - Purpose: Extracellular pH (pHe) is an important biomarker for cancer cell metabolism. Acido-chemical exchange saturation transfer (CEST) MRI uses the contrast agent iopamidol to create spatial maps of pHe. Measurements of amide proton transfer exchange rates (kex) from endogenous CEST MRI were compared to pHe measurements by exogenous acido-CEST MRI to determine whether endogenous kex could be used as a proxy for pHe measurements. Methods: Spatial maps of pHe and kex were obtained using exogenous acidoCEST MRI and an endogenous CEST MRI analyzed with the omega plot method, respectively, to evaluate mouse kidney, a flank tumor model, and a spontaneous lung tumor model. The pHe and kex results were evaluated using pixelwise comparisons. Results: The kex values obtained from endogenous CEST measurements did not correlate with the pHe results from exogenous CEST measurements. The kex measurements were limited to fewer pixels and had a limited dynamic range relative to pHe measurements. Conclusion: Measurements of kex with endogenous CEST MRI cannot substitute for pHe measurements with acidoCEST MRI. Whereas endogenous CEST MRI may still have good utility for evaluating some specific pathologies, exogenous acido-CEST MRI is more appropriate when evaluating pathologies based on pHe values. Magn Reson Med 79:2766–2772, 2018.

AB - Purpose: Extracellular pH (pHe) is an important biomarker for cancer cell metabolism. Acido-chemical exchange saturation transfer (CEST) MRI uses the contrast agent iopamidol to create spatial maps of pHe. Measurements of amide proton transfer exchange rates (kex) from endogenous CEST MRI were compared to pHe measurements by exogenous acido-CEST MRI to determine whether endogenous kex could be used as a proxy for pHe measurements. Methods: Spatial maps of pHe and kex were obtained using exogenous acidoCEST MRI and an endogenous CEST MRI analyzed with the omega plot method, respectively, to evaluate mouse kidney, a flank tumor model, and a spontaneous lung tumor model. The pHe and kex results were evaluated using pixelwise comparisons. Results: The kex values obtained from endogenous CEST measurements did not correlate with the pHe results from exogenous CEST measurements. The kex measurements were limited to fewer pixels and had a limited dynamic range relative to pHe measurements. Conclusion: Measurements of kex with endogenous CEST MRI cannot substitute for pHe measurements with acidoCEST MRI. Whereas endogenous CEST MRI may still have good utility for evaluating some specific pathologies, exogenous acido-CEST MRI is more appropriate when evaluating pathologies based on pHe values. Magn Reson Med 79:2766–2772, 2018.

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KW - tumor acidosis

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A comparison of exogenous and endogenous CEST MRI methods for evaluating in vivo pH

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