Dynamic diffusion-weighted hyperpolarized 13 C imaging based on a slice-selective double spin echo sequence for measurements of cellular transport.

PURPOSE: To develop a pulse sequence to dynamically measure the ADC of hyperpolarized substrates during their perfusion, metabolic conversion, and transport.
METHODS: We proposed a slice-selective double spin echo sequence for dynamic hyperpolarized 13 C diffusion-weighted imaging. The proposed pulse sequence was optimized for a high field preclinical scanner through theoretical analysis and simulation. The performance of the method was compared to non-slice-selective double spin echo via in vivo studies. We also validated the sequence for dynamic ADC measurement in both phantom studies and transgenic mouse model of prostate cancer studies.
RESULTS: The optimized pulse sequence outperforms the traditional sequence with smaller saturation effects on the magnetization of hyperpolarized compounds that allowed more dynamic imaging frames covering a longer imaging time window. In pre-clinical studies (N = 8), the dynamic hyperpolarized lactate ADC maps of 6 studies in the prostate tumors showed an increase measured ADC over time, which might be related to lactate efflux from the tumor cells.
CONCLUSIONS: The proposed sequence was validated and shown to improve dynamic diffusion weighted imaging compared to the traditional double spin echo sequence, providing ADC maps of lactate through time.