^<31>P Chemical Shift Imaging for Quantitative Measurements of Cardiac High-Energy Phosphate

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The aims of this study were to determine whether or not quantitative measurements of cardiac high-energy phosphate by ^<31>P chemical shift imaging (CSI) are useful in assessing myocardial viability and to clarify which CSI technique is the most suitable. The one-dimensional CSI study group was composed of 41 patients with stenosis of the left anterior descending coronary artery (>50%) and 11 healthy control subjects (C). The patients were divided into two groups on the basis of exercise ^<201>Tl scintigraphy : a reversible ^<201>Tl defect group (RD [+] , N=29) and a fixed ^<201>Tl defect group (RD [-] , n=12). Cardiac ^<31>P magnetic resonance spectra were obtained by slice-selected one-dimensional CSI.For metabolite quantification a standard was placed at the center of the surface coil. ANOVA revealed significant differences among the three groups with respect to mean (<plus-minus>SD) phosphocreatine at rest (C,12.14<plus-minus>4.25>RD [+] , 7.64<plus-minus>3.00>RD [-] , 3.94<plus-mi … More nus>2.21 mumol/g wet heart tissue, p<0.05) as well as a significant decrease in ATP in the RD [-] group (C,7.72<plus-minus>2.97 ; RD [+] , 6.35<plus-minus>3.17>RD [-] , 4.35<plus-minus>1.52 mumol/g wet heart tissue, p<0.05). When a two-dimensional phase encoding technique with slice-selective excitation in the axial direction was used to measure the concentration of inorganic phosphate in the phantom, it yielded very accurate results. When the same technique, however, was applied to human heart, each voxel (2.5x2.5x2.5-cm^3) was often not totally filled with myocardium. This led to difficulties in estimating the myocardial weight in the voxel. It was impossible to place a standard within the sensitive volume of the surface coil when employing a two-dimensional phase encoding technique with slice-selective excitation in the coronal direction. Thus, one-dimensional CSI with sagittal slice-selective excitation is the most suitable CSI technique for cardiac metabolite measurements and is useful for the evaluation of myocardial viability. Less