Metabolite-selective hyperpolarized ¹³C imaging using extended chemical shift displacement at 9.4 T

Purpose: To develop a technique for frequency-selective hyperpolarized ¹³C metabolic imaging in ultra-high field strength which exploits the broad spatial chemical shift displacement in providing spectral and spatial selectivity. Methods: The spatial chemical shift displacement caused by the slice-selection gradient was utilized in acquiring metabolite-selective images. Interleaved images of different metabolites were acquired by reversing the polarity of the slice-selection gradient at every repetition time, while using a low-bandwidth radio-frequency excitation pulse to alternatingly shift the displaced excitation bands outside the imaging subject. Demonstration of this technique is presented using ¹H phantom and in vivo mouse renal hyperpolarized ¹³C imaging experiments with conventional chemical shift imaging and fast low-angle shot sequences. Results: From phantom and in vivo mouse studies, the spectral selectivity of the proposed method is readily demonstrated using results of chemical shift spectroscopic imaging, which displayed clearly delineated images of different metabolites. Imaging results using the proposed method without spectral encoding also showed effective separation while also providing high spatial resolution. Conclusion: This method provides a way to acquire spectrally selective hyperpolarized ¹³C metabolic images in a simple implementation, and with potential ability to support combination with more elaborate readout methods for faster imaging.