Figure 3.

In vivo imaging of transgene activity. ¹⁹FMRS images of FNuc (red arrows) and associated parametric maps of regional CD-UPRT levels and activity within CD-UPRT⁺ xenografts are shown. The inset cartoon indicates the slice orientation of the acquired images. ¹⁹FMRS enabled images demonstrating homogeneous enzyme activity (a) to be distinguished from xenografts exhibiting regional heterogeneities in CD-UPRT activity (b). An area of deficient CD-UPRT activity is evident within voxel IV and is underscored by the presence of unmetaboilized 5FU (yellow arrow). ¹⁹FMRSI was also able to discern CD-UPRT enzyme levels and activity in mixed xenografts grown from equal parts CD-UPRT⁺ and CD-UPRT^- cells (c). Homogeneous CD-UPRT activity was seen; however, this activity is reduced in comparison to CD-UPRT⁺ tumors (a).