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Improved calculation of the equilibrium magnetization of arterial blood in arterial spin labeling

Ahlgren, André LU ; Wirestam, Ronnie LU ; Knutsson, Linda LU and Petersen, Esben Thade (2018) In Magnetic Resonance in Medicine 80(5). p.2223-2231
Abstract

PURPOSE: To propose and assess an improved method for calculating the equilibrium magnetization of arterial blood ( M0a), used for calibration of perfusion estimates in arterial spin labeling.

METHODS: Whereas standard M0a calculation is based on dividing a proton density-weighted image by an average brain-blood partition coefficient, the proposed method exploits partial-volume data to adjust this ratio. The nominator is redefined as the magnetization of perfused tissue, and the denominator is redefined as a weighted sum of tissue-specific partition coefficients. Perfusion data were acquired with a pseudo-continuous arterial spin labeling sequence, and partial-volume data were acquired using a rapid saturation recovery sequence... (More)

PURPOSE: To propose and assess an improved method for calculating the equilibrium magnetization of arterial blood ( M0a), used for calibration of perfusion estimates in arterial spin labeling.

METHODS: Whereas standard M0a calculation is based on dividing a proton density-weighted image by an average brain-blood partition coefficient, the proposed method exploits partial-volume data to adjust this ratio. The nominator is redefined as the magnetization of perfused tissue, and the denominator is redefined as a weighted sum of tissue-specific partition coefficients. Perfusion data were acquired with a pseudo-continuous arterial spin labeling sequence, and partial-volume data were acquired using a rapid saturation recovery sequence with the same readout module. Results from 7 healthy volunteers were analyzed and compared with the conventional method.

RESULTS: The proposed method produced improved M0a homogeneity throughout the brain in all subjects. The mean gray matter perfusion was significantly higher with the proposed method compared with the conventional method: 61.2 versus 56.3 mL/100 g/minute (+8.7%). Although to a lesser degree, the corresponding white matter values were also significantly different: 20.8 versus 22.0 mL/100 g/minute (-5.4%). The spatial and quantitative differences between the 2 methods were similar in all subjects.

CONCLUSION: Compared with the conventional approach, the proposed method produced more homogenous M0a maps, corresponding to a more accurate calibration. The proposed method also yielded significantly different perfusion values across the whole brain, and performed consistently in all subjects. The new M0a method improves quantitative perfusion estimation with arterial spin labeling, and can therefore be of considerable value in perfusion imaging applications.

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Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
in
Magnetic Resonance in Medicine
volume
80
issue
5
pages
9 pages
publisher
Wiley Online Library
external identifiers
  • scopus:85044347927
ISSN
1522-2594
DOI
10.1002/mrm.27193
language
English
LU publication?
yes
id
0e78c7bc-6545-416b-a543-640e47045423
date added to LUP
2018-09-07 11:25:03
date last changed
2018-09-16 04:57:00
@article{0e78c7bc-6545-416b-a543-640e47045423,
  abstract     = {<p>PURPOSE: To propose and assess an improved method for calculating the equilibrium magnetization of arterial blood ( M0a), used for calibration of perfusion estimates in arterial spin labeling.</p><p>METHODS: Whereas standard M0a calculation is based on dividing a proton density-weighted image by an average brain-blood partition coefficient, the proposed method exploits partial-volume data to adjust this ratio. The nominator is redefined as the magnetization of perfused tissue, and the denominator is redefined as a weighted sum of tissue-specific partition coefficients. Perfusion data were acquired with a pseudo-continuous arterial spin labeling sequence, and partial-volume data were acquired using a rapid saturation recovery sequence with the same readout module. Results from 7 healthy volunteers were analyzed and compared with the conventional method.</p><p>RESULTS: The proposed method produced improved M0a homogeneity throughout the brain in all subjects. The mean gray matter perfusion was significantly higher with the proposed method compared with the conventional method: 61.2 versus 56.3 mL/100 g/minute (+8.7%). Although to a lesser degree, the corresponding white matter values were also significantly different: 20.8 versus 22.0 mL/100 g/minute (-5.4%). The spatial and quantitative differences between the 2 methods were similar in all subjects.</p><p>CONCLUSION: Compared with the conventional approach, the proposed method produced more homogenous M0a maps, corresponding to a more accurate calibration. The proposed method also yielded significantly different perfusion values across the whole brain, and performed consistently in all subjects. The new M0a method improves quantitative perfusion estimation with arterial spin labeling, and can therefore be of considerable value in perfusion imaging applications.</p>},
  author       = {Ahlgren, André and Wirestam, Ronnie and Knutsson, Linda and Petersen, Esben Thade},
  issn         = {1522-2594},
  language     = {eng},
  number       = {5},
  pages        = {2223--2231},
  publisher    = {Wiley Online Library},
  series       = {Magnetic Resonance in Medicine},
  title        = {Improved calculation of the equilibrium magnetization of arterial blood in arterial spin labeling},
  url          = {http://dx.doi.org/10.1002/mrm.27193},
  volume       = {80},
  year         = {2018},
}