19F Magnetic resonance imaging of perfluorooctanoic acid encapsulated in liposome for biodistribution measurement

The tissue distribution of perfluorooctanoic acid (PFOA), which is known to show unique biological responses, has been visualized in female mice by 19F magnetic resonance imaging (MRI) incorporated with the recent advances in microimaging technique. The chemical shift selected fast spin-echo method was applied to acquire in vivo 19F MR images of PFOA. The in vivo T1 and T2 relaxation times of PFOA were proven to be extremely short, which were 140 (± 20) ms and 6.3 (± 2.2) ms, respectively. To acquire the in vivo 19F MR images of PFOA, it was necessary to optimize the parameters of signal selection and echo train length. The chemical shift selection was effectively performed by using the 19F NMR signal of CF3 group of PFOA without the signal overlapping because the chemical shift difference between the CF3 and neighbor signals reaches to 14kHz. The most optimal echo train length to obtain 19F images efficiently was determined so that the maximum echo time (TE) value in the fast spin-echo sequence was comparable to the in vivo T2 value. By optimizing these parameters, the in vivo 19F MR image of PFOA was enabled to obtain efficiently in 12 minutes. As a result, the time course of the accumulation of PFOA into the mouse liver was clearly pursued in the 19F MR images. Thus, it was concluded that the 19F MRI becomes the effective method toward the future pharmacological and toxicological studies of perfluorocarboxilic acids.