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MR imaging measurement of compartmental water diffusion in perfused heart slices
J R Forder1, J D Bui, D L Buckley
1Department of Neuroscience, University of Florida, Gainesville 32611, USA. jforder@uab.edu
Abstract:
Myocardial tissue slices were isolated from the left ventricular free wall (7 slices) and left ventricular papillary muscle (3 slices) of New Zealand White male rabbits (n = 4) and were subsequently superfused with a modified St. Thomas' Hospital cardioplegic solution at 19 degrees C. The diffusion-weighted images were obtained with a 600-MHz nuclear magnetic resonance spectrometer using diffusion gradient b-values that ranged from 166 to 6,408 s/mm(2); the apparent diffusion coefficient of water in the tissues were subsequently calculated. All of the tissue samples that were studied exhibited nonmonoexponential diffusion. Data from seven slices were mathematically fitted by a biexponential expression with a fast diffusion component of 0.72 +/- 0.07 x 10(-3) mm(2)/s, and a slow diffusion component of 0.060 +/- 0.033 x 10(-3) mm(2)/s. The fast component dominated the calculated apparent diffusion coefficient of the tissue, composed of 82 +/- 3% of the overall diffusion-dependent signal decay. Thus myocardial tissue exhibits characteristics consistent with multiple compartments of diffusion. This work has important implications for myocardial diffusion tensor imaging, as well as the changes in diffusion that have been reported following myocardial ischemia.
Insights
Myocardial tissue exhibits complex water diffusion, characterized by two distinct components. This finding is crucial for understanding diffusion tensor imaging and changes post-myocardial ischemia.
Area of Science:
- Cardiovascular Research
- Biophysics
- Medical Imaging
Background:
- Understanding water diffusion in myocardial tissue is essential for interpreting diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI).
- Previous studies suggest complex diffusion behaviors in biological tissues, but specific characterization in myocardial tissue requires further investigation.
Purpose of the Study:
- To characterize the diffusion properties of water within myocardial tissue using diffusion-weighted magnetic resonance imaging (DW-MRI).
- To investigate the multi-compartmental nature of water diffusion in myocardial tissue and its implications for imaging techniques.
Main Methods:
- Myocardial tissue slices from New Zealand White rabbits were analyzed using a 600-MHz nuclear magnetic resonance spectrometer.
- Diffusion-weighted images were acquired with varying b-values (166 to 6,408 s/mm(2)) to calculate the apparent diffusion coefficient (ADC) of water.
- Nonmonoexponential diffusion data were fitted using a biexponential model to identify diffusion components.
Main Results:
- All myocardial tissue samples exhibited nonmonoexponential water diffusion.
- A biexponential model revealed a fast diffusion component (0.72 ± 0.07 x 10(-3) mm(2)/s) and a slow component (0.060 ± 0.033 x 10(-3) mm(2)/s).
- The fast diffusion component accounted for the majority (82 ± 3%) of the diffusion-dependent signal decay, indicating multi-compartmental diffusion.
Conclusions:
- Myocardial tissue demonstrates characteristics consistent with multiple diffusion compartments for water.
- These findings have significant implications for the development and interpretation of myocardial diffusion tensor imaging.
- Understanding these diffusion characteristics is vital for assessing changes in myocardial tissue following ischemia.