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Magn Reson Med. 2017 May;77(5):1853-1865. doi: 10.1002/mrm.26264. Epub 2016 May 12.

Insight into the quantitative metrics of chemical exchange saturation transfer (CEST) imaging.

Author information

1
Divison of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.
2
F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.
3
Department of Radiology, Beijing Hospital, Beijing, China.

Abstract

PURPOSE:

To evaluate the reliability of four CEST imaging metrics for brain tumors, at varied saturation power levels and magnetic field strengths (3-9.4 Tesla (T)).

METHODS:

A five-pool proton exchange model (free water, semisolid, amide, amine, and NOE-related protons) was used for the simulations. For the in vivo study, eight glioma-bearing rats were scanned at 4.7 T. The CEST ratio (CESTR), CESTR normalized with the reference value (CESTRnr ), inverse Z-spectrum-based (MTRRex ), and apparent exchange-related relaxation (AREX) were compared.

RESULTS:

The simulated CEST signal intensities using MTRRex and AREX were substantially increased at relatively high radiofrequency (RF) saturation powers at 3 T and 4.7 T, whereas CESTR and CESTRnr metrics remained relatively stable. There were tremendously high MTRRex and AREX signals around the water frequency at all field strengths because of the small denominators. In the rat tumor study at 4.7 T, both CESTR and CESTRnr showed clear contrasts in the tumor with respect to the normal tissue across all saturation power levels (0.5-3 μT), whereas the AREX showed negligible to negative insignificant contrasts.

CONCLUSIONS:

CEST metrics must be carefully selected based on the different experimental settings. CESTR and CESTRnr are more reliable at 3 T (a clinical field strength) and 4.7 T. Magn Reson Med 77:1853-1865, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

KEYWORDS:

APT; CEST; MTR; NOE; brain tumor

PMID:
27170222
PMCID:
PMC5107181
DOI:
10.1002/mrm.26264
[Indexed for MEDLINE]
Free PMC Article

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