31P NMR Relaxation Does Not Affect the Quantitation of Changes in Phosphocreatine, Inorganic Phosphate, and ATP Measured In Vivo During Complete Ischemia in Swine Brain |
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Authors: | Ronald J T Corbett Abbot R Laptook |
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Institution: | Mary Nell and Ralph Rogers Magnetic Resonance Center, Department of Radiology, U.S.A.;Department of Pediatrics, Southwestern Medical Center at Dallas, Dallas, Texas, U.S.A. |
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Abstract: | Abstract: Ischemia-induced changes in 31P NMR relaxation were examined in 16 piglets. NMR spectra were acquired under control conditions and during complete cerebral ischemia induced via cardiac arrest. Changes in T 1 were assessed directly in six animals during control conditions and after 30–45 min of complete ischemia when changes in brain P1 levels had reached a plateau. The T 1 for P1 did not change, i.e., 2.3 ± 0.5 s during control conditions versus 2.4 ± 1.0 s during ischemia. To evaluate phosphocreatine and ATP, two types of spectra, with a long (25-s) or short (1-s) interpulse delay time, were collected during the first 10 min of ischemia (n = 10). Both types of spectra showed the same time course of changes in phosphocreatine and ATP levels, implying that the T 1 relaxation times do not change during ischemia. There were no changes in the linewidths of phosphocreatine, ATP, or P1 during ischemia, implying that the T *2 values remain constant. Our results suggest that the 31P T 1 and T *2 for phosphocreatine, Pi, and ATP do not change during ischemia, and therefore changes in 31P NMR peak intensity accurately reflect changes in metabolite concentrations. |
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Keywords: | Brain Ischemia Phosphorus NMR Relaxation times Quantitation |
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