Hyperpolarized choline as an MR imaging molecular probe: Feasibility of in vivo imaging in a rat model

Purpose To assess the feasibility of choline MRI using a new choline molecular probe for dynamic nuclear polarization (DNP) hyperpolarized MRI. Materials and Methods Male Sprague-Dawley rats with an average weight of 400 ± 20 g (n = 5), were anesthetized and injection tubing was placed in the tail vein. [1,1,2,2-D₄, 1-¹³C]choline chloride (CMP1) was hyperpolarized by DNP and injected into rats at doses ranging from 12.6 to 50.0 mg/kg. Coronal projection ¹³C imaging was performed on a 3 Tesla clinical MRI scanner (bore size 60 cm) using a variable flip angle gradient echo sequence. Images were acquired 15 to 45 s after the start of bolus injection. Signal intensities in regions of interest were determined at each time point and compared. Results ¹³C MRI images of hyperpolarized CMP1 at a 50 mg/kg dose showed time-dependent organ distribution patterns. At 15 s, high intensities were observed in the inferior vena cava, heart, aorta, and kidneys. At 30 s, most of the signal intensity was localized to the kidneys. These distribution patterns were reproduced using 12.6 and 25 mg/kg doses. At 45 s, only signal in the kidneys was detected. Conclusion Hyperpolarized choline imaging with MRI is feasible using a stable-isotope labeled choline analog (CMP1). Nonradioactive imaging of choline accumulation may provide a new investigatory dimension for kidney physiology.