Detection of 3D Cardiac metabolism after injection of hyperpolarized [1-13C]pyruvate

Methods Three healthy male mini-pigs (38±2 kg) were maintained under deep sedation; a dose of 20 mL of 230 mM [1-13C]pyruvate was administered over about 10 s by manual injection. Animal experiments were performed on a 3T GE Signa HDx scanner with a 13C quadrature birdcage coil. [1-13C]pyruvate was polarized using a HyperSense DNP polariser with subsequent dissolution. The final injection solution contained 230 mM sodium [1-13C] pyruvate, 100 mM TRIS buffer, 0.27 mM Na2EDTA and 20 μM Dotarem with T≈37°C and pH ≈ 7.6. Anatomical reference images were acquired in the axial plane with standard FIESTA sequence (body coil FOV=30x30 cm, FA=20°, TE/TR=3.8ms/7.52ms, matrix 224x160, slice thickness 5 mm, 20 slices). Metabolic information covering the heart were obtained using a 3D IDEAL spiral CSI prescribed on the same region imaged by the reference anatomical sequence (FOV= 30x30 cm, slab thickness=100mm) starting 20 seconds after the beginning of the hyperpolarized [1C]-pyruvate injection. The IDEAL spiral CSI concept was implemented into a multi-slice, pulse-and-acquire sequence with a 2D spiral readout and phase encoding along the third dimension. A constant echo time shift of TE=0.9ms, 11 encoding steps and FA=7° were used to optimize the study for the considered frequencies. The data was reconstructed using spectrally-preconditioned, minimum-norm CS inversion followed by gridding reconstruction implemented in Matlab. The reconstruction on cardiac short axis (SA) and image fusion was performed by PMOD software.