Figure 5.

PET images of contrast agent-labeled stem cell. Panel (a) is the schematic of the indirect labeling using HSV1-TK and radioisotopes. Cells are transfected with HSV1-tk via vectors. ¹⁸F-FHBG is phosphorylated by the enzyme which is encoded in the gene of the cell, and the reporter is consequently entrapped in the cell. Reproduced courtesy of Springer Publisher Group [95]. Panel (b) is a PET-CT image of MSCs that were labeled with a mutant HSV1-tk reporter gene. The cells were implanted into a swine and subsequently administrated with [¹⁸F] FHBG. The PET-CT image provides both anatomical information (gray scale from CT) and the contrast of the implanted cells (color from PET data). Reproduced courtesy of Radiological Society of North America [96].