Figure 4.

MRI in vivo detection of ¹⁹F-labeled human NK cells in NSG mice bearing xenograft human tumors. (A–B) 10 × 10^{6 19}F-labeled (4 mg/mL PFPE for 24 h) human NK cells were injected intratumor into one NSG mouse bearing a human neuroblastoma (CHLA-20) on the right flank (T: Tumor). ¹⁹F intensity from NK cells or from the reference (Ref: Reference vial of ¹⁹F) vial is displayed on a “hot-iron” scale. Mouse was imaged for ¹H and ¹⁹F by MRI using a volumetric coil and anesthetized using ketamine and xylazine. (A) Composite ¹⁹F/¹H images at 0 or 2 d post NK cell injection are shown with 32 min and 42 min of scan time for each day respectively. (B) The number (black bars corresponds to left y-axis) and percentage (red line graph corresponds to the right y-axis) of NK detected in the tumor is denoted and was determined based on the efficiency of ¹⁹F uptake by NK cells from NMR analysis. (C–D) 7 × 10^{6 19}F-labeled (4 mg/mL PFPE for 24 h) NK cells were injected intratumor into one NSG mouse bearing a human mantle cell lymphoma (Z138) on the right flank. (C) Imaging for ¹H and ¹⁹F was established as described in (A) with scan time of 42 min for each time point. (D) Number (black bars corresponds to left y-axis) and percentage (red line graph corresponds to the right y-axis) of NK cells detected at the tumor site is denoted for each imaging time point. Values represent the mean ± SEM of one single experiment. The uncertainty in the ¹⁹F reference mean signal (${\displaystyle {\sigma }_{{\overline{S}}_R}}$) was estimated as the standard deviation of the ROI drawn on the reference (see methods for quantification of ¹⁹F signal).