Prostate Cancer Xenograft PET Imaging

All animal experiments were conducted under the protocol approved by the University of Texas Southwestern Institutional Animal Care and Use Committee. PET of athymic nu/nu mice (male; age, 4–5 wks) bearing human prostate cancer xenografts was performed using a Siemens Inveon PET/CT Multimodality System as described previously (16 (link),24 (link)). Briefly, a structural CT scan of tumor-bearing mice was acquired (80 kV, 500 µA) with a pixel size of approximately 0.1 mm to create an anatomic image that was subsequently used for attenuation correction of the PET emission data. After conclusion of the CT scan, mice were injected with the tracer ⁶⁴CuCl₂ (74 kBq or 2 µCi/g of body weight) intravenously via the tail vein. Static whole-body imaging was performed at 2 and 24 h after intravenous injection of the tracer, which consisted of 2 overlapping frames of 15 min for each frame. On completion of the PET/CT at 24 h after injection, a tissue radioactivity assay was performed, and tissue radioactivity was calculated and expressed as decay-corrected percentage injected dose per gram of tissue (%ID/g) as described previously (16 (link)). The size of the postmortem tumors was measured with a caliper, and tumor volumes were calculated using an ellipsoidal formula (1/2 × (length × width²)) modified from that described previously (25 (link)).