In Vivo Hyperpolarized 13C Pyruvate Imaging

Tail vein catheterization was performed for administration of hyperpolarized [1–¹³C]pyruvate. Temperature, peripheral capillary oxygen saturation and respiration rate were monitored throughout the experiment. [1–¹³C]pyruvate was polarized in the Spinlab (GE Healthcare, Brøndby, Denmark). Polarization was performed as previously described^{5 (link)}. Each animal was injected with 1.5 ml (125 mM) hyperpolarized [1–¹³C]pyruvate. MR scans were performed in a 3 T clinical MR system (GE Healthcare, Brøndby, Denmark) equipped with a dual tuned ¹³C/¹H volume rat coil (GE Healthcare, Brøndby, Denmark). A slice-selective ¹³C IDEAL spiral sequence was used for hyperpolarized ¹³C-pyruvate imaging acquiring images every 5 second (sec). The sequence was initiated 20 sec. after the start of injection with the following parameters: flip angle = 10°, 11 IDEAL echoes and one initial spectrum per IDEAL encoding, TR/TE/ΔTE = 100 ms/0.9 ms/0.9 ms, FOV = 80 × 80 mm², 5 × 5 mm real resolution and an axial slice thickness of 15 mm covering both kidneys. Acquired ¹H and ¹³C images were converted to dicom files. Regions of interest (ROI’s) were placed around each kidney in Osirix. Hyperpolarized MR metabolic kinetic analysis was performed by ratiometric analysis according to previous reports^{28 (link)}.