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. J. Magn. Reson. Imaging 2011;33:320–327. © 2011 Wiley‐Liss, Inc.