Purpose: Metabolic magnetic resonance imaging (MRI) using hyperpolarized [1-13C]-pyruvate offers unprecedented new insight into disease and response to therapy. 13C-enriched reference standards are required to enable fast and accurate calibration for 13C studies, but care must be taken to ensure that the reference is compatible with both 13C and 1H acquisitions. The goal of this study was to optimize the composition of a 13C-urea reference for a dual-tuned 13C/1H endorectal coil and minimize imaging artifacts in metabolic and multiparametric MRI studies involving hyperpolarized [1-13C]-pyruvate. Methods: Due to a high amount of Gd doping for the purpose of reducing the spin-lattice relaxation time (T1) of urea, the 1H signal produced by a reference of 13C-urea in normal water was rapidly relaxed, resulting in severe artifacts in heavily T1-weighted images. Hyperintense ringing artifacts in 1H images were mitigated by reducing the 1H concentration in a 13C-urea reference via deuteration and lyophilization. Several references were fabricated and their SNR was compared using 1H and 13C imaging sequences on a 3T MRI scanner. Finally, 1H prostate phantom imaging was conducted to compare image quality and 1H signal intensity of normal and deuterated urea references. Results: The deuterated 13C-urea reference provides strong 13C signal for calibration and an attenuated 1H signal that does not interfere with heavily T1-weighted scans. Deuteration and lyophilization were fundamental to the reduction in 1H signal and hyperintense ringing artifacts. There was a 25-fold reduction in signal intensity when comparing the nondeuterated reference to the deuterated reference, while the 13C signal was unaffected. Conclusion: A deuterated reference reduced hyperintense ringing artifacts in 1H images by reducing the 1H signal produced from the 13C-urea in the reference. The deuterated reference can be used to improve anatomical image quality in future clinical 1H and hyperpolarized [1-13C]-pyruvate MRI prostate imaging studies.
- hyperpolarized pyruvate
- metabolic imaging
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging