9 March 2018 Quantitative image-based phosphorus-31 MR spectroscopy for evaluating age-based differences in skeletal muscle metabolites
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Purpose: To develop and validate a novel in-vivo phosphorus-31 magnetic resonance spectroscopy (31P-MRS) method to determine the absolute concentrations of phosphocreatine [PCr], inorganic phosphate [Pi], and adenosine triphosphate [ATP] in the vastus lateralis muscle. Materials and Methods: An external 6 mL plastic vial with 850 mM of methylenediphosphonic acid (MDP), fixed to the center of a commercial dual-tuned transmit/receive surface coil, was used to calibrate metabolite concentrations from spectral areas. A 15cm diameter, 4 L cylindrical phantom (35 mM H3PO4) was scanned on a custom coil holder using the same parameters. Reproducibility of the 31P-MRS measurements was determined in volunteers (2M/3F, age = 39.2±21.9 years) while accuracy was determined using phantoms of known concentrations. Eight young subjects (24.5+4.2 years; 4M/4F) and eight older subjects (59.6+4.5 years; 4M/4F) were scanned. Student’s t-test was used to compare older versus younger subjects. Results: The percent error between the calculated and known molarity of phantoms was 3.3±1.9%. The mean coefficient of variation for the measurements of [PCr] was 5.2±3.7 %. Phosphorus metabolite concentrations, including [PCr] (25.2±3.4 mM vs. 28.5±3.4 mM, p < 0.005), [ATP] (6.68±0.84 mM vs. 7.71±0.61 mM, p<0.05) and [Pi] (3.18±0.46 mM vs. 2.56±0.55 mM, p<0.05) were significantly lower in older versus younger subjects. A significant, negative correlation was found between [PCr] and BMI (r = -0.50, p < 0.05). Conclusion: Quantitative 31P-MRS measurements reveal previously unappreciated differences in skeletal muscle phosphorus metabolite concentrations between young and older subjects and may provide unique insights when combined with other metabolic tests.
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Shenweng Deng, Shenweng Deng, Erika M. Ripley, Erika M. Ripley, Juan A. Vasquez, Juan A. Vasquez, Devjit Tripathy, Devjit Tripathy, Ralph A. DeFronzo, Ralph A. DeFronzo, Geoffrey D. Clarke, Geoffrey D. Clarke, "Quantitative image-based phosphorus-31 MR spectroscopy for evaluating age-based differences in skeletal muscle metabolites", Proc. SPIE 10573, Medical Imaging 2018: Physics of Medical Imaging, 105732T (9 March 2018); doi: 10.1117/12.2294627; https://doi.org/10.1117/12.2294627

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