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T2 relaxation time bias in gagCEST at 3T and 7T : comparison of saturation schemes

Peterson, Pernilla LU ; Olsson, Emma LU and Svensson, Jonas LU (2019) In Magnetic Resonance in Medicine 81(2). p.1044-1051
Abstract

Purpose: To characterize the effects of water T2 relaxation time in the glycosaminoglycan chemical exchange saturation transfer method (gagCEST) and compare them between 3T and 7T as well as between various saturation schemes. Methods: Simulations and a phantom experiment were conducted at 3T and 7T in a range of water T2 values and GAG concentrations using various saturation schemes. For both simulations and MRI measurements, unsaturated signal as well as the saturated Z-spectrum were generated, and the magnetization transfer ratio asymmetry at 1 parts per million was used as a measure of the gagCEST effect size. Results: The simulations and phantom experiment results showed a clear GAG concentration and... (More)

Purpose: To characterize the effects of water T2 relaxation time in the glycosaminoglycan chemical exchange saturation transfer method (gagCEST) and compare them between 3T and 7T as well as between various saturation schemes. Methods: Simulations and a phantom experiment were conducted at 3T and 7T in a range of water T2 values and GAG concentrations using various saturation schemes. For both simulations and MRI measurements, unsaturated signal as well as the saturated Z-spectrum were generated, and the magnetization transfer ratio asymmetry at 1 parts per million was used as a measure of the gagCEST effect size. Results: The simulations and phantom experiment results showed a clear GAG concentration and T2 dependence of the gagCEST effect size. Whereas the gagCEST effect size was much larger at 7T, the impact of the T2 bias was more pronounced at 3T. The saturation train length, duty cycle, and average B1 all had clear impact on both the gagCEST effect size and T2 bias. Conclusion: The water T2 relaxation is important to consider in gagCEST, especially at 3T. The T2 differences can introduce a pronounced bias, which may obscure the gagCEST effect when using low duty cycles and long saturation trains.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
7T, cartilage, gagCEST, T2 relaxation
in
Magnetic Resonance in Medicine
volume
81
issue
2
pages
1044 - 1051
publisher
Wiley Online Library
external identifiers
  • scopus:85053511585
ISSN
0740-3194
DOI
10.1002/mrm.27465
language
English
LU publication?
yes
id
a9d5cfa6-f5bc-4709-b79f-995b64282377
date added to LUP
2018-10-22 10:46:44
date last changed
2019-01-14 13:26:36
@article{a9d5cfa6-f5bc-4709-b79f-995b64282377,
  abstract     = {<p>Purpose: To characterize the effects of water T<sub>2</sub> relaxation time in the glycosaminoglycan chemical exchange saturation transfer method (gagCEST) and compare them between 3T and 7T as well as between various saturation schemes. Methods: Simulations and a phantom experiment were conducted at 3T and 7T in a range of water T<sub>2</sub> values and GAG concentrations using various saturation schemes. For both simulations and MRI measurements, unsaturated signal as well as the saturated Z-spectrum were generated, and the magnetization transfer ratio asymmetry at 1 parts per million was used as a measure of the gagCEST effect size. Results: The simulations and phantom experiment results showed a clear GAG concentration and T<sub>2</sub> dependence of the gagCEST effect size. Whereas the gagCEST effect size was much larger at 7T, the impact of the T<sub>2</sub> bias was more pronounced at 3T. The saturation train length, duty cycle, and average B<sub>1</sub> all had clear impact on both the gagCEST effect size and T<sub>2</sub> bias. Conclusion: The water T<sub>2</sub> relaxation is important to consider in gagCEST, especially at 3T. The T<sub>2</sub> differences can introduce a pronounced bias, which may obscure the gagCEST effect when using low duty cycles and long saturation trains.</p>},
  author       = {Peterson, Pernilla and Olsson, Emma and Svensson, Jonas},
  issn         = {0740-3194},
  keyword      = {7T,cartilage,gagCEST,T2 relaxation},
  language     = {eng},
  number       = {2},
  pages        = {1044--1051},
  publisher    = {Wiley Online Library},
  series       = {Magnetic Resonance in Medicine},
  title        = {T<sub>2</sub> relaxation time bias in gagCEST at 3T and 7T : comparison of saturation schemes},
  url          = {http://dx.doi.org/10.1002/mrm.27465},
  volume       = {81},
  year         = {2019},
}