Dataset Information

Choice of reference measurements affects quantification of long diffusion time behaviour using stimulated echoes.

ABSTRACT:

Purpose

To demonstrate how reference data affect the quantification of the apparent diffusion coefficient (ADC) in long diffusion time measurements with diffusion-weighted stimulated echo acquisition mode (DW-STEAM) measurements, and to present a modification to avoid contribution from crusher gradients in DW-STEAM.

Methods

For DW-STEAM, reference measurements at long diffusion times have significant b₀ value, because b?=?0 cannot be achieved in practice as a result of the need for signal spoiling. Two strategies for acquiring reference data over a range of diffusion times were considered: constant diffusion weighting (fixed-b₀ ) and constant gradient area (fixed-q₀ ). Fixed-b₀ and fixed-q₀ were compared using signal calculations for systems with one and two diffusion coefficients, and experimentally using data from postmortem human corpus callosum samples.

Results

Calculations of biexponential diffusion decay show that the ADC is underestimated for reference images with b?>?0, which can induce an apparent time-dependence for fixed-q₀ . Restricted systems were also found to be affected. Experimentally, the exaggeration of the diffusion time-dependent effect under fixed-q₀ versus fixed-b₀ was in a range predicted theoretically, accounting for 62% (longitudinal) and 35% (radial) of the time dependence observed in white matter.

Conclusions

Variation in the b-value of reference measurements in DW-STEAM can induce artificial diffusion time dependence in ADC, even in the absence of restriction. Magn Reson Med 79:952-959, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

SUBMITTER: Kleinnijenhuis M

PROVIDER: S-EPMC5811793 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Publications

Choice of reference measurements affects quantification of long diffusion time behaviour using stimulated echoes.

Kleinnijenhuis Michiel M Mollink Jeroen J Lam Wilfred W WW Kinchesh Paul P Khrapitchev Alexandre A AA Smart Sean C SC Jbabdi Saad S Miller Karla L KL

Magnetic resonance in medicine 20170503 2

<h4>Purpose</h4>To demonstrate how reference data affect the quantification of the apparent diffusion coefficient (ADC) in long diffusion time measurements with diffusion-weighted stimulated echo acquisition mode (DW-STEAM) measurements, and to present a modification to avoid contribution from crusher gradients in DW-STEAM.<h4>Methods</h4>For DW-STEAM, reference measurements at long diffusion times have significant b<sub>0</sub> value, because b = 0 cannot be achieved in practice as a result of ...[more]

PMID: 28470858

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Project description:PurposeTo determine the optimal respiratory navigator gating configuration for the quantification of left ventricular strain using spiral cine displacement encoding with stimulated echoes (DENSE) MRI.Materials and methodsTwo-dimensional spiral cine DENSE was performed on a 3 Tesla MRI using two single-navigator configurations (retrospective, prospective) and a combined "dual-navigator" configuration in 10 healthy adults and 20 healthy children. The adults also underwent breathhold DENSE as a reference standard for comparisons. Peak left ventricular strains, signal-to-noise ratio (SNR), and navigator efficiency were compared. Subjects also underwent dual-navigator gating with and without visual feedback to determine the effect on navigator efficiency.ResultsThere were no differences in circumferential, radial, and longitudinal strains between navigator-gated and breathhold DENSE (P = 0.09-0.95) (as confidence intervals, retrospective: [-1.0%-1.1%], [-7.4%-2.0%], [-1.0%-1.2%]; prospective: [-0.6%-2.7%], [-2.8%-8.3%], [-0.3%-2.9%]; dual: [-1.6%-0.5%], [-8.3%-3.2%], [-0.8%-1.9%], respectively). The dual configuration maintained SNR compared with breathhold acquisitions (16 versus 18, P = 0.06). SNR for the prospective configuration was lower than for the dual navigator in adults (P = 0.004) and children (P < 0.001). Navigator efficiency was higher (P < 0.001) for both retrospective (54%) and prospective (56%) configurations compared with the dual configuration (35%). Visual feedback improved the dual configuration navigator efficiency to 55% (P < 0.001).ConclusionWhen quantifying left ventricular strains using spiral cine DENSE MRI, a dual navigator configuration results in the highest SNR in adults and children. In adults, a retrospective configuration has good navigator efficiency without a substantial drop in SNR. Prospective gating should be avoided because it has the lowest SNR. Visual feedback represents an effective option to maintain navigator efficiency while using a dual navigator configuration.Level of evidence2 J. Magn. Reson. Imaging 2017;45:786-794.

Dataset Information

Choice of reference measurements affects quantification of long diffusion time behaviour using stimulated echoes.

Purpose

Methods

Results

Conclusions

Publications

Choice of reference measurements affects quantification of long diffusion time behaviour using stimulated echoes.

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