Figure 3.

These images show an example of imaging cardiac gene expression using adenoviral-mediated mutant thymidine kinase (HSV1-sr39tk) as a PET reporter gene expressed in the target cells and [18F]-FHBG as a PET reporter imaging probe. Trapping of tracer occurs only in cells expressing the reporter gene. A, At day 4, whole-body micro-PET image of a rat shows focal cardiac [18F]-FHBG activity at the site of intramyocardial Ad-CMV-HSV1-sr39tk injection. Liver [18F]-FHBG activity is also seen because of systemic adenoviral leakage with transduction of hepatocytes. Control rat injected with Ad-CMV-Fluc shows no [18F]-FHBG activity in either the cardiac of hepatic regions. Significant gut and bladder activities are seen for study and control rats because of route of [18F]-FHBG clearance. B, Tomographic views of cardiac microPET images. The [13N]-NH3 (gray scale) images of perfusion are superimposed on [18F]-FHBG images (color scale), demonstrating HSV1-sr39tk reporter gene expression. [18F]-FHBG activity is seen in the anterolateral wall for experimental rat compared with background signal in control rat. Perpendicular lines represent the axis for vertical and horizontal cuts. Color scale is expressed as % ID/g. (Figure reproduced with permission from Wu et al. Circulation. 2002;106:180–183.)