High spatiotemporal resolution bSSFP imaging of hyperpolarized [1-13 C]pyruvate and [1-13 C]lactate with spectral suppression of alanine and pyruvate-hydrate.

Abstract

PurposeThe balanced steady‐state free precession (bSSFP) acquisition enables high spatiotemporal resolution for hyperpolarized 13C MRI at 3T but is limited by spectral contamination from adjacent resonances. The purpose of this study was to develop a framework for in vivo dynamic high resolution imaging of hyperpolarized [1‐13C]pyruvate and [1‐13C]lactate generated in vivo at 3T by simplifying the spectrum through the use of selective suppression pulses.MethodsSpectral suppression pulses were incorporated into the bSSFP sequence for suppression of [1‐13C]alanine and [1‐13C]pyruvate‐hydrate signals, leaving only the pyruvate and lactate resonances. Subsequently, the bSSFP pulse width, time‐bandwidth, and repetition time were optimized for imaging these dual resonances.ResultsThe spectral suppression reduced both the alanine and pyruvate‐hydrate signals by 85.5 ± 4.9% and had no significant effect on quantitation of pyruvate to lactate conversion (liver: P = 0.400, kidney: P = 0.499). High resolution (2 × 2 mm2 and 3 × 3 mm2) subsecond 2D coronal projections and 3D 2.5 mm isotropic images were obtained in rats and tumor‐bearing mice with 1.8–5 s temporal resolution, allowing for calculation of lactate‐to‐pyruvate ratios and kPL.ConclusionThe developed framework presented here shows the capability for dynamic high resolution volumetric hyperpolarized bSSFP imaging of pyruvate‐to‐lactate conversion on a clinical 3T MR scanner.