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. 2021 Jun 22;300(3):626–632. doi: 10.1148/radiol.2021204500

Figure 4:

Metabolic imaging of calf muscle with exercise. A, Diagram shows how hyperpolarized (HP) carbon 13 (13C) MRI was performed in exercising muscle. ASL = arterial spin labeling, 1H = hydrogen 1. B, 1H T2-weighted (T2w) fast spin-echo (FSE) MRI scan of 8-cm axial section in study participant 6 (34-year-old man). Blue region in sagittal MRI scan indicates prescribed axial section for 13C MRI. Yellow arrows indicate arteries. A = anterior, I = inferior, P = posterior, S = superior. C, Time-averaged metabolite maps of hyperpolarized [1-13C]-pyruvate, [1-13C]-lactate, [1-13C]-alanine, and [13C]-bicarbonate. A = anterior, L = left, P = posterior, R = right. D, 13C metabolite maps, normalized with peak [1-13C]-pyruvate signal and overlaid on corresponding hydrogen 1 fast spin-echo image of section. E, Metabolite ratio maps of carbon 13 products—lactate-to-bicarbonate ratio, alanine-to-bicarbonate ratio, and lactate-to-alanine ratio.

Metabolic imaging of calf muscle with exercise. A, Diagram shows how hyperpolarized (HP) carbon 13 (13C) MRI was performed in exercising muscle. ASL = arterial spin labeling, 1H = hydrogen 1. B, 1H T2-weighted (T2w) fast spin-echo (FSE) MRI scan of 8-cm axial section in study participant 6 (34-year-old man). Blue region in sagittal MRI scan indicates prescribed axial section for 13C MRI. Yellow arrows indicate arteries. A = anterior, I = inferior, P = posterior, S = superior. C, Time-averaged metabolite maps of hyperpolarized [1-13C]-pyruvate, [1-13C]-lactate, [1-13C]-alanine, and [13C]-bicarbonate. A = anterior, L = left, P = posterior, R = right. D, 13C metabolite maps, normalized with peak [1-13C]-pyruvate signal and overlaid on corresponding hydrogen 1 fast spin-echo image of section. E, Metabolite ratio maps of carbon 13 products—lactate-to-bicarbonate ratio, alanine-to-bicarbonate ratio, and lactate-to-alanine ratio.