Abstract 19147: Fast, Free-breathing, Heart-rate Independent Quantitative Myocardial Oxygenation MRI at 3T for Detecting Ischemic Heart Disease Without Contrast Agents With Simultaneous 13N-Ammonia PET Validation

Abstract

Introduction: Myocardial BOLD MRI is an emerging non-contrast approach for the assessment of ischemic heart disease. Current BOLD MR methods are limited in part by poor spatial coverage, heart rate dependency and image artifacts, particularly at 3T. To address these limitations, we developed a heart-rate independent, free-breathing 3D T2 mapping technique at 3T that utilizes near perfect imaging efficiency, which can be completed within 3 minutes. We tested our approach in a canine model and validated our findings with simultaneously acquired 13N-ammonia PET perfusion data in a clinical hybrid PET-MR system. Methods: Healthy dogs (n=8) were studied with a state of the art PET-MR system (Siemens Healthcare). For validation, dynamic 13N-ammonia PET scans were simultaneously acquired with BOLD MR data. PET images were analyzed using qPET (Cedars-Sinai Medical Center). T2 values were measured from basal, mid and apical slices at rest and adenosine stress in BOLD images. Myocardial BOLD reserve (T2(stress):T2(rest)) and perfusion reserve (Q(stress):Q(rest)) were computed on a slice basis and regressed. Results: A representative set of BOLD and PET images acquired at rest and adenosine stress are shown in Fig. 2. T2 measures at stress were significantly greater than at rest (T2: 39.5±2.5 ms (rest) vs. 44.0±3.3 ms (stress), p<0.05)); similar results were observed for Q (Q: 0.8±0.1 ml/mg/min (rest) vs. 2.0±0.9 ml/mg/min (stress); p<0.05). Linear regression of BOLD and perfusion reserves showed high correlation (R2=0.6, p<0.05). Conclusions: This is the first study to examine myocardial BOLD MRI with simultaneously acquired PET perfusion data. Our findings showed that BOLD response is highly correlated with PET perfusion suggesting that the proposed BOLD MR method is a viable non-contrast approach for imaging myocardial perfusion. Further studies are required to examine its utility in the setting of ischemic heart disease.