In human heart failure due to DCM, both PCr and ATP are significantly reduced. Ratios of PCr to ATP underestimate changes of high-energy phosphate levels.

Human cardiac 31 P nuclear magnetic resonance (NMR) spectra are usually quantified in relative terms, i.e., the ratio of metabolite signals is calculated. If 31 P NMR spectroscopy of the heart is to emerge as a clinically relevant diagnostic modality, reliable quantification of absolute concentrations of 31 P metabolites is required. We applied spectral localization with optimal point spread function (SLOOP) 31 P NMR spectroscopy to measure absolute concentrations of phosphocreatine (PCr) and adenosine triphosphate (ATP) in human myocardium. The accuracy of the quantification was first validated in a phantom study. Seven healthy volunteers (aged 19-29 years) were then examined at 1.5 T using a nominal spatial resolution of 25 mL. SLOOP allowed us to obtain localized spectra from compartments anatomically matched to the left ventricular wall. The a priori knowledge of the anatomical structure was obtained from 1 H images. The spatially varying effects of saturation, off-resonance, and sensitivity were considered during the reconstruction process. Metabolites were quantified with reference to an external 31 P standard. Concentrations of 9.0 ؎ 1.2 and 5.3 ؎ 1.2 mmol/kg wet wt (mean ؎ SD, n ‫؍‬ 9) were determined for PCr and ATP in normal heart, respectively. The influence of nuclear Overhauser enhancement on metabolite quantification is dis-

Purpose:To show the application of auto-sensitivity encoding (SENSE)-a self-calibrating parallel imaging technique-to first pass perfusion imaging of the whole human heart. Materials and Methods:The self-calibrating parallel imaging method auto-SENSE was implemented for a saturation recovery turbo-fast low-angle shot (FLASH) sequence on a 1.5-T scanner using a standard four-element body phased array coil. By reducing the acquisition time per slice by a factor of two compared to conventional turbo FLASH imaging, the number of imaged slices could be doubled to six to ten with an unchanged temporal resolution of one image per heartbeat. This technique has been tested in eight healthy volunteers for contrast-enhanced heart perfusion imaging.Results: Auto-SENSE heart perfusion imaging with improved coverage of the human heart could be performed successfully in all volunteers. A first quantitative comparison of perfusion values between the auto-SENSE and the non-SENSE techniques shows good agreement. Conclusion:Auto-SENSE allows perfusion imaging of the whole human heart without gaps.

The aim of this study was to apply 31 P magnetic resonance spectroscopy (MRS) using spatial localization with optimal point spread function (SLOOP) to investigate possible age and gender dependencies of the energy metabolite concentrations in the human heart. Thirty healthy volunteers (18 males and 12 females, 21-67 years old, mean ‫؍‬ 40.7 years) were examined with the use of 31 P-MRS on a 1.5 T scanner. Intra-and interobserver variability measures (determined in eight of the volunteers) were both 3.8% for phosphocreatine (PCr), and 4.7% and 8.3%, respectively, for adenosine triphosphate (ATP). High-energy phosphate (HEP) concentrations in mmol/kg wet weight were 9.7 ؎ 2.4 (age < 40 years, N ‫؍‬ 16) and 7.7 ؎ 2.5 (age ≥ 40 years, N ‫؍‬ 14) for PCr, and 5.1 ؎ 1.0 (age < 40 years) and 4.1 ؎ 0.8 (age ≥ 40 years) for ATP, respectively. Separated by gender, PCr concentrations of 9.2 ؎ 2.4 (men, N ‫؍‬ 18) and 8.0 ؎ 2.8 (women, N ‫؍‬ 12) and ATP concentrations of 4.9 ؎ 1.0 (men) and 4.2 ؎ 0.9 (women) were measured. A significant decrease of PCr and ATP was found for volunteers older than 40 years (P < 0.05), but the differences in metabolic concentrations between both sexes were not significant. In conclusion, age has a minor but still significant impact on cardiac energy metabolism, and no significant gender differences were detected. Key words: myocardium; aging; cardiac energy metabolism; 31 P MR spectroscopy; gender difference 31 P MR spectroscopy (MRS) is the only noninvasive means of studying myocardial energy metabolism in humans. The analysis and understanding of myocardial energetics can provide valuable information on the pathophysiology of various heart diseases and guide therapeutic approaches (1). In addition to metabolite ratios (e.g., the phosphocreatine (PCr)/adenosine triphosphate (ATP) ratio), absolute concentrations of high-energy phosphate (HEP) metabolites can be measured using different spectroscopic techniques (2-6). Using spatial localization with optimal point spread function (SLOOP) (7), Meininger et al. (6) presented a technique to measure absolute concentrations of human cardiac HEP with minimal contamination from neighboring tissue, which was subsequently applied to different patient studies (8). Thus, a subtle impairment in the myocardial HEP metabolism in a subclinical state could be detected (9). Advancing age is one of the major independent risk factors for coronary heart disease (10). Therefore, changes in the heart with increasing age have been systematically studied. Animal studies demonstrated a loss of myocytes (11) and subsequent replacement with fibrosis (11,12). Changes in metabolism were shown in rats by Finelli et al. (13), who detected a decrease of ATP in the myocardium with increasing age. Age-dependent morphological changes in humans, have been demonstrated in a number of echocardiographic and functional MR studies. A recent 31 P-MRS study reported a decrease of the myocardial HEP ratios with age (14). To date, however, only one study has investigated the influence of age...

The reduction in cardiac high-energy phosphates in some patients with MS points to a subclinical involvement of the heart. This may be important for treatment with potentially cardiotoxic drugs. Longitudinal studies are need to understand the clinical relevance of our findings.