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Quantifying 19F-Labeled Human Natural Killer Cell-Trafficking with MRI

K Ludwig

KD Ludwig1*, MN Bouchlaka2, JW Gordon3, BP Bednarz1,4,5, CM Capitini2, SB Fain1,4,5, (1) Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, (2) Pediatrics and Carbone Cancer Center, University of Wisconsin-Madison, Madison, Wisconsin, (3) Radiology and Biomedical Imaging, University of California-San Fransisco, San Francisco, California, (4) Radiology, University of Wisconsin-Madison, Madison, Wisconsin, (5) Biomedical Engineering, University of Wisconsin, Madison, Wisconsin


MO-A-BRD-3 Monday 7:30AM - 9:30AM Room: Ballroom D

Purpose: To determine 19F-labeling efficiency in ex vivo MRI of cultured human Natural Killer (hNK) cells and to quantify 19F-labeled NK cell trafficking in vivo in naive mice and in mice bearing pediatric cancers with MRI.

Methods: One immunodeficient and one neuroblastoma tumor-bearing mouse were anesthetized with ketamine and xylazine. The hNK and mouse NK cells isolated from healthy donor peripheral blood mononuclear cells or spleens were expanded and incubated for 24 hours in a commercially available perfluoropolyether (PFPE) tracer. NMR was performed on a 9.4T spectrometer to verify successful uptake of PFPE agent into NK cells. Imaging was performed on a 4.7T small animal MRI system using a 19F volume quadrature coil. 19F images were acquired using a spin-echo sequence (1.1x1.1x2.0mm3 resolution, ~42 minutes scan time). A 19F reference vial was placed contralateral to the tumor/injection site for in vivo quantification.

Results: A dose-dependent response of 19F signal was shown in mouse NK cells labeled with increasing concentrations of PFPE. NMR spectra of the separated cells and supernatant confirmed that 19F signal originated from within the hNK cells. In vitro signal from 19F-labeled hNK cells was quantified as a function of cell concentration. About 1.6x106 hNK cells was determined to be the minimum cell concentration detectabilty for a 1.1x1.1x2.0mm3 voxel at the 42 minute scan time. 19F-labeled hNK cells were injected into the flank or tumor directly. 19F signal stayed localized in flank or within the neuroblastoma tumor for at least 48 hours.

Conclusion: 19F-labeling of NK cells has been confirmed in vitro, both with imaging and spectroscopic analysis. hNK injection into a neuroblastoma tumor-bearing mouse showed that hNK cells can be successfully detected and tracked longitudinally in vivo. Improving sensitivity for quantification of trafficking patterns within the tumor is ongoing.

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