Anti Galectin 3 radiolabelled antibody: small animal imaging with High-resolution and Anger camera

High resolution camera (HRC) can be useful in small animal imaging. Our HRC shows 4inch2 FOV, CsI crystals are integrated with tungsten blade, square parallel hole collimator and coupled with a position sensitive photomultiplier (PSPMT). Its spatial resolution is 2mm. AIM: To verify if small animal imaging with HRC is more reliable than Anger camera imaging, Methods: We have labelled a rat monoclonal antibody anti-human galectin-3 with 99mTc and studied its targeting potential in n/n balbc mice xenografted with poorly differentiated ARO cell line. Twenty mice were transplanted with galectin-3 positive ARO cells and developed tumours of 0.5-1.0 cm diameter. The animals were injected i.v. with 37MBq (100?Ci) of 99mTc-labeled mAb (30 µg protein). Whole body images were acquired at 1, 3, 6, 9 and 24 hours, using Anger camera and HRC. Images were analyzed by drawing ROIs on the tumour. Hip muscle was taken as background. Uptake was expressed as target to background ratio (T/M). All mice were divided in 5 groups of 4 animals. One animal of each group was scarified at a planned time and tissue samples from blood, major organs and tumours were removed, weighted and counted. The ex vivo bio-distribution of radiolabelled galectin-3 mAb was expressed as % of injected dose per gram of tissue (%ID/g). Ex-vivo T/M ratios obtained from autopsy were compared with data from the two cameras. Results: Inhomogeneous radioactivity within xenografted tumours was identified only by HRC images. In the sites presenting low activity with HRC images, autopsy identified necrotic zones. T/M ratio is reported in table Conclusion. Parallel hole collimator HRC is very useful in small animal imaging. Actually, the trend of T/M ratio was consistent with ex vivo data, owing precise drawing of ROIs and linearity of device counting. In a future, the combination of HRC with highly specific radiopharmaceuticals, such as radiolabelled anti-G3 antibody, can be useful also on man.