Click on image to view larger version.

Figure 3 Positron emission tomography (PET)–computed tomographic (CT) imaging of morphology and biology. Representative short-axis tomographic images are shown. (A) Study animal (animal 1; Table 1) after regional injection of adenovirus carrying HSV1-sr39tk reporter gene together with VEGF₁₂₁ gene (Ad_Tk-VEGF, top row), or HSV1-sr39tk reporter gene only (Ad_sr39tk, bottom row). (B) Another study animal (animal 3; Table 1) after regional injection of Ad_Tk-VEGF (top row). This time, virus expressing VEGF₁₂₁ only was used as internal control (Ad_VEGF, bottom row). (C) Control animal (animal 9; Table 1) after regional injection of saline at both sites. Columns from left to right: on the left, a schematic display of individual location and orientation of short-axis slices, along with injection sites (yellow) is shown; next, contrast-enhanced multislice CT depicts location of titanium clip markings (yellow arrows), along with circumferential wall thickness; next, PET-CT fusion of morphologic CT with PET images of the reporter probe [¹⁸F]fluoro-hydroxymethylbutyl-guanine (FHBG) show significant accumulation of FHBG, colocalizing with clip markings in areas expressing the HSV1-sr39tk reporter gene (animal A, both rows; animal B, top row); on the right, PET perfusion images at rest and during adenosine-induced vasodilation show significantly elevated [¹³N]ammonia uptake at sites where VEGF₁₂₁ is overexpressed (animal A, top row; animal B, both rows), whereas it is regionally homogeneous after Ad_sr39tk injection (animal A, bottom row) or saline injection (animal C).