Concentrations of human cardiac phosphorus metabolites determined by SLOOP 31P NMR spectroscopy

Abstract

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-

Age and gender dependence of human cardiac phosphorus metabolites determined by SLOOP 31P MR spectroscopy

“…The determined absolute values for the PCr and ATP concentrations for the different groups in this study are at the lower end of published values (2-6), but they closely match previous results obtained with the same technique (i.e., SLOOP evaluation of CSI with NOE and external standard (6)). Additional studies are necessary to determine whether a systematic underestimation of HEP concentrations occurs when SLOOP is used to quantify examinations using NOE signal enhancement.…”

“…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)(3)(4)(5)(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).…”

MR spectroscopy in heart failure—clinical and experimental findings

“…Therefore, localization techniques are required, which results in further signal loss. However, a new localization method termed SLOOP (spectral localization with optimum pointspread function) [9] allows selection of voxel sizes of not only rectangular, but any shape; this should improve signal to noise by improved matching of voxel and heart shape. For most spectroscopic techniques, scout images are first obtained with MRI, which are used to select the spectroscopic volume(s).…”

Noninvasive measurements of cardiac high-energy phosphate metabolites in dilated cardiomyopathy by using 31P spectroscopic chemical shift imaging

“…To improve clinical acceptance, new sequences were developed to include signal improvements by the nuclear overhauser effect (NOE) [12] and spatial localisation with optimal pointspread function (SLOOP) techniques [13,14]. SLOOP is a new technique which is able to match the size and the shape of the sensitive volumes to the anatomical structures to minimize partial volume effects [13].…”