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.
An indirect method for in vivo T mapping of C-labeled metabolites using T and T * information of water protons obtained a priori is proposed. The T values of C metabolites are inferred using the relationship to T ' of coexisting H and the T * of C metabolites, which is measured using routine hyperpolarized C CSI data. The concept is verified with phantom studies. Simulations were performed to evaluate the extent of T estimation accuracy due to errors in the other measurements. Also, bias in the C T * estimation from the C CSI data was studied. In vivo experiments were performed from the brains of normal rats and a rat with C6 glioma. Simulation results indicate that the proposed method provides accurate and unbiased C T values within typical experimental settings. The in vivo studies found that the estimated T of [1- C] pyruvate using the indirect method was longer in tumor than in normal tissues and gave values similar to previous reports. This method can estimate localized T relaxation times from multiple voxels using conventional hyperpolarized C CSI and can potentially be used with time resolved fast CSI.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.