Boosting 19 F MRI—SNR efficient detection of paramagnetic contrast agents using ultrafast sequences

19 F MRI offers high specificity but usually low sensitivity. Here, paramagnetic relaxation enhancement is assessed as a method to improve SNR efficiency in 19 F MRI. Compounds with short relaxation times are used that combine fluorine and a paramagnetic ion within the same molecule. Different molecular designs provide T 1 values in the range of 1.4–15 ms and T 2 * / T 1 ratios from 0.3 to 1. Gradient echo, as well as ultrafast radial MR sequences, is optimized to achieve highest SNR efficiency. Compared to nonparamagnetic compounds, ultrafast sequences can yield a gain of up to a factor 27 in sensitivity, whereas the gain with gradient echo is only factor 11. Comparison among the paramagnetic compounds shows that T 2 * / T 1 close to unity is a prerequisite for highest SNR efficiency gain and that best results are obtained for compounds with T 1 in the range of 1–5 ms. Magn Reson Med 69:1056–1062, 2013. © 2012 Wiley Periodicals, Inc.