Small-animal PET of reporter gene expression. (A) Coronal small-animal PET images through xenografts placed subcutaneously over shoulders are shown: nontransduced and transduced U87 xenografts, including dCK, dCKDM, HSV1-tk, and HSV1-R176Qsr39tk. 18F-FEAU and 18F-FHBG images at 2 h after radiotracer administration obtained on consecutive days are shown for same animal. All images were adjusted to same color scale. (B) Image-based measurements of 18F-FEAU and 18F-FHBG at 2 h after radiotracer administration in same animals, expressed as percentage injected dose per cubic centimeter of tissue (%ID/cm3). Values are mean ± SD, n = 5. N/T = nontransduced.