- Oral presentation
- Open Access
Inter-centre reproducibility of cardiac diffusion tensor measures
© Tunnicliffe et al.; licensee BioMed Central Ltd. 2014
- Published: 16 January 2014
- Apparent Diffusion Coefficient
- Fractional Anisotropy
- Diffusion Tensor Imaging
- Royal Brompton Hospital
- Average Apparent Diffusion Coefficient
Diffusion tensor imaging is a technique which, by studying the small motions of water molecules in biological tissue, could provide new insights into the myoarchitecture of both healthy and diseased hearts. The apparent diffusion coefficient (ADC) and fractional anisotropy (FA) are values derived from the measured diffusion tensor and which have previously shown some sensitivity to disease. However, previously reported normal values of these parameters have varied widely. The aim of this work was to evaluate the reproducibility of the ADC and FA measured at two separate centres.
The stimulated-echo diffusion tensor sequence was as previously described1, with a 37.5% field-of-view in the phase-encode direction and fixed monopolar diffusion gradients. This gives b-values proportional to the RR-interval; at 60 bpm b = 15 (reference) and 350 s/mm2. These b-value calculations were verified by using the sequence to measure phantoms with known ADC. The sequence was independently implemented at the two centres, a 3T Skyra (Siemens, Erlangen, Germany) at centre A and a TIM Trio (Siemens) at centre B. Each centre implemented separate analysis software in Matlab (Mathworks, Natick, MA). Ten healthy volunteers were scanned at each centre, a maximum of 8 days apart. In each breathhold, one average of a reference image and six diffusion weighted images, with independent diffusion directions, was acquired. Eight averages of a single mid-ventricular short axis slice were acquired. The resulting diffusion images were analysed at both centres to produce ADC and FA maps. Regions of interest (ROIs) covering the left ventricle were manually drawn, and the average ADC and FA calculated, giving four measures per subject (ADC and FA in systole and diastole). Inspection of the data revealed that they were non-normally distributed, so Friedman's repeated measures test as implemented in the R agricolae package (R Foundation, Vienna, Austria) was used, with Holm-corrected Fisher's LSD for post hoc testing. The two centres were deemed the same if p > 0.1.
The median measures for data acquired and analysed at the same centre, with p-values for Friedman's test for differences between all acquisition and analysis combinations, showing that with identical ROIs, the differences between the two centres is statistically insignificant.
Median over all 10 subjects ± IQR
1.04 ± 0.03 × 10-3mm2/s
0.41 ± 0.05
1.17 ± 0.14 × 10-3mm2/s
0.54 ± 0.04
1.15 ± 0.13 × 10-3mm2/s
0.41 ± 0.05
1.26 ± 0.17 × 10-3mm2/s
0.55 ± 0.04
Friedman's test p-value
This work demonstrates that, when regions of interest are carefully defined, ADC and FA are reproducible cardiac diffusion measures across different centres, when using a well-matched sequence. However, it may be that interobserver variability is an important factor in the analysis of cardiac diffusion tensor imaging.
Parts of this research were funded by the National Institute for Health Research (NIHR) Oxford Biomedical Research Centre based at The Oxford University Hospitals Trust at the University of Oxford, and the NIHR Cardiovascular Biomedical Research Unit at the Royal Brompton Hospital and Imperial College, London. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health.
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.