Study of rat skeletal muscle activation by PET/CT and [11C]acetate

Purpose: The purpose of the present study is to apply kinetic analysis to investigate exercise-related changes in the skeletal muscle of the rat hind limb by [<sup>11</sup>C]acetate PET/CT. Methods: One-leg contractions were induced in Wistar rats by electrostimulation of the VL muscle motor point. After 15 minutes of muscle contractions [<sup>11</sup>C]acetate was injected and PET/CT of the rat hind limbs was acquired. The resting leg was used as a control reference. The perfusion index F was calculated for the target muscles (exercised and control) and correlated to the corresponding SUVs. For both F and the SUV, the ratio of the value extracted for the active muscle to the one derived for the muscle at rest was computed (respectively, F<sub>E</sub>/F<sub>R</sub> and SUV<sub>E</sub>/SUV<sub>R</sub>). Results: For the experimental dataset, a strong correlation (R<sup>2</sup> = 0.97, P = 0.01) between F<sub>E</sub>/F<sub>R</sub> and SUV<sub>E</sub>/SUV<sub>R</sub> was observed. The ratio F<sub>E</sub>/F<sub>R</sub> resulted to be higher than the ratio SUV<sub>E</sub>/SUV<sub>R</sub> (average values: 2.1 ± 0.7 and 1.19 ± 0.08, respectively). Conclusion: Preliminary results indicate that both kinetic modeling and the SUV can detect changes in muscles between rest and exercise conditions, when associated to [<sup>11</sup>C]acetate PET/CT.

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