SU‐GG‐BRC‐09: CT Detection of Primary and Metastatic Lesions with a Nano‐Agent in Rabbits: Validation with FDG‐PET

Purpose: To evaluate the performance of a recently engineered nano‐sized liposome CT agent to detect primary and metastatic tumor lesions in a VX2‐sarcoma rabbit model as compared to FDG‐PET. Method and Materials: Nine New Zealand White rabbits bearing VX2‐sarcoma in their left lateral quadriceps received a single intravenous injection of 80 nm liposomes co‐encapsulating 185 ± 37 mg/kg iodine in the form of iohexol (Omnipaque®) and 7 ± 1 mg/kg gadolinium in the form of gadoteridol (Prohance®). The CT/PET (GE Discovery ST) imaging session took place twelve days after the tumor inoculation procedure, five days post liposome contrast administration and one hour post‐FDG injection (30.3 ± 5.1 MBq/kg). Following CT/PET imaging, the rabbits were sacrificed and the primary and metastatic lesions were examined by a pathologist. The measurement of tumor size was performed on the CT data set. The registration of the CT and PET images was performed using MIPAV. Results: Liposome‐CT demonstrated the same sensitivity and specificity as FDG‐PET for the detection of the 9 primary tumors (volumes = 25 – 7280 mm 3 , SUV max = 1.5 – 10.9, HU max = 173 – 596). In addition, liposome‐CT detected 13 metastatic muscle lesions (volumes = 14 – 2732 mm 3 , HU max = 254 – 493) that were histologically malignant, while FDG‐PET identified 7 (volumes = 54 – 1044 mm 3 , SUV max = 2.7 – 7.1). For the 16 lesions detected by both imaging modalities, there was a positive correlation between the PET SUV max and the CT HU max . Conclusion: In this investigation, increased contrast of primary and metastatic lesions in CT was achieved with the administration of the liposome nano‐agent. This demonstrates the feasibility of employing the liposome‐CT method for effective tumor detection and localization.