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MRI for the evaluation of regional myocardial perfusion in an experimental animal model
M Lombardi1, R A Jones, J Westby
1MR Center, Medical Section, University Hospital, Trondheim, Norway. lomass@po.ifc.pi.cnr.it
Abstract:
Myocardial perfusion was assessed in nine pigs using ultrafast gradient-echo MRI (.5 T, 15-mT/m gradients) at different levels of myocardial blood flow (range, .005-1.84 ml/min/g), generated either by adenosine infusion or by a mechanical occluder, and measured independently using radiolabeled microspheres. Sixty-four consecutive, ECG-triggered, diastolic, short axis images of the left ventricle were obtained during intravenous bolus injections (n = 30) of .05 mmol/kg of gadopentetate dimeglumine. Relative changes in peak intensity, time to peak intensity, washin slope, correlation coefficient, and cross-correlation coefficient were computed from the time-intensity curves obtained from four regions of interest, namely septal, anterior, lateral, and inferior walls. The values from the inferior wall acted as reference for evaluating relative changes in the other three regions. The cross-correlation coefficient (P < .001, rho = .60) and the peak intensity (P < .001, r = .72) showed the best correlation with myocardial blood flow. The washin slope showed a weak positive trend (P < .05), but the low value of r (r = .28) indicated that the use of this parameter to predict flow was invalid; the correlation coefficient and time to peak intensity were not correlated (P = ns). In conclusion, this study shows that it is possible to evaluate relative myocardial perfusion after the first pass of a an intravenously injected bolus of gadopentetate dimeglumine, using dynamic MRI on a conventional medium field MRI system. The cross-correlation coefficient and the peak intensity resulted in more efficient parameters to evaluate relative inhomogeneity of regional myocardial perfusion.
Insights
Dynamic MRI effectively assesses relative myocardial perfusion using gadopentetate dimeglumine. Cross-correlation coefficient and peak intensity are the most efficient parameters for evaluating regional differences in blood flow.
Area of Science:
- Cardiovascular Imaging
- Magnetic Resonance Imaging
- Physiology
Background:
- Assessing myocardial blood flow is crucial for diagnosing and managing cardiovascular diseases.
- Conventional methods for measuring myocardial perfusion can be invasive or time-consuming.
Purpose of the Study:
- To evaluate the efficacy of dynamic ultrafast gradient-echo MRI in assessing relative myocardial perfusion.
- To identify the most reliable MRI parameters for quantifying regional myocardial blood flow variations.
Main Methods:
- Nine pigs underwent MRI with gadopentetate dimeglumine injection to measure myocardial perfusion under varying flow conditions.
- ECG-triggered, diastolic, short-axis images were acquired, and time-intensity curves were analyzed.
- Parameters including peak intensity, time to peak, washin slope, and correlation coefficients were calculated for different myocardial regions.
Main Results:
- Cross-correlation coefficient and peak intensity demonstrated the strongest correlation with myocardial blood flow (rho = .60, r = .72).
- Washin slope showed a weak positive trend but was not a valid predictor of flow (r = .28).
- Correlation coefficient and time to peak intensity did not correlate with myocardial blood flow.
Conclusions:
- Dynamic MRI with a first-pass contrast agent bolus can accurately assess relative myocardial perfusion.
- Cross-correlation coefficient and peak intensity are superior parameters for evaluating regional heterogeneity in myocardial perfusion.
- This technique is feasible on conventional medium-field MRI systems.