Purpose: This study was aimed at assessing the performance of a liposome-based computed tomography (CT) contrast agent to detect tumor and inflammatory lesions in a rabbit model relative to (18)F-fluorodeoxyglucose- positron emission tomography (FDG-PET).
Materials and methods: Nine New Zealand White rabbits were inoculated with a cell suspension obtained from the tumor tissue of a donor rabbit bearing VX2 carcinoma. Spontaneously formed inflammatory lesions were identified in the skeletal muscles of six of the nine animals. The CT liposome agent (185 +/- 37 mg/kg of iodine) was administered intravenously 7 days following tumor inoculation. The PET/CT imaging session took place five days post-liposome contrast administration and 1 h post (18)F-FDG injection (30.3 +/- 5.1 MBq/kg). Approximately 20 h post-imaging, the tumor and inflammatory lesions were excised for histo-pathology assessment.
Results: Liposome-CT identified the same number of primary tumors as FDG-PET (nine lesions, volumes = 0.07-7.01 cm(3), SUV(max) = 1.5-10.9, HU(mean) = 103.0-140.6). It also detected 25 inflammatory lesions (volumes = 0.01-2.73 cm(3), HU(mean) = 114.5-268.6), while FDG-PET identified seven (volumes = 0.05-1.04 cm(3), SUV(max) = 2.7-7.1). Differences in the mean CT signal (HU(mean)) between the tumor and inflammatory lesions were statistically significant (p < 0.0001). Partial volume adjusted SUV(max) values for the two lesion types calculated from the FDG-PET data set did not yield a significant difference (p > 0.15).
Conclusion: These results demonstrate that liposome-CT can be considered for effective screening of neoplastic and inflammatory diseases, as well as subsequent image-guided biopsy. Moreover, the differential accumulation of the liposomal agent at tumor and inflammatory sites highlights its potential role in increasing the specificity of image-based diagnosis.