T(2) preparation method for measuring hyperemic myocardial O(2) consumption: in vivo validation by positron emission tomography.

Purpose: To validate a new T(2) -prepared method for the quantification of regional myocardial O(2) consumption during pharmacologic stress with positron emission tomography (PET).

Materials And Methods: A T(2) prepared gradient-echo sequence was modified to measure myocardial T(2) within a single breath-hold. Six beagle dogs were randomly selected for the induction of coronary artery stenosis. Magnetic resonance imaging (MRI) experiments were performed with the T(2) imaging and first-pass perfusion imaging at rest and during either dobutamine- or dipyridamole-induced hyperemia. Myocardial blood flow (MBF) was quantified using a previously developed model-free algorithm. Hyperemic myocardial O(2) extraction fraction (OEF) and consumption (MVO(2) ) were calculated using a two-compartment model developed previously. PET imaging using (11) C-acetate and (15) O-water was performed in the same day to validate OEF, MBF, and MVO(2) measurements.

Results: The T(2) -prepared mapping sequence measured regional myocardial T(2) with a repeatability of 2.3%. By myocardial segment-basis analysis, MBF measured by MRI is closely correlated with that measured by PET (R(2) = 0.85, n = 22). Similar correlation coefficients were observed for hyperemic OEF (R(2) = 0.90, n = 9, mean difference of PET - MRI = -2.4%) and MVO(2) (R(2) = 0.83, n = 7, mean difference = 4.2%).

Conclusion: The T(2) -prepared imaging method may allow quantitative estimation of regional myocardial oxygenation with relatively good accuracy. The precision of the method remains to be improved.