TUMOR AFFINITY OF PB-203-CHLORIDE - COMPARISON WITH GA-67-CITRATE ANDTL-201-CHLORIDE

The radionuclide Pb-203 Pb decays completely by electron capture to st able Tl-203 with a half-life of 52 h. The primary radiation from the d ecay is gamma-ray radiation 280 keV (80%). Pb-203 is produced easily f rom the natural metal thallium by the method described below. Pb-203-c hloride is a promising imaging agent for tumour scanning because of th e large retention value for tumour tissue and the small value for norm al organs, but the large value for the kidney and bone is a shortcomin g when considering it as an imaging agent. The retention value of Pb-2 03 in tumour tissue is larger than that of Tl-201 and smaller than tha t of Ga-67. The tumour/inflammatory lesion retention ratio for Pb-203 is very large in comparison with those for Ga-67 and Tl-201. Pb-203 ac cumulates to a large extent in viable tumour tissue, and less in necro tic tumour tissue and in inflammatory lesion. Therefore, Pb-203-chlori de is far better for visualization of viable tumour tissue than Ga-67 and Tl-201 if the large retention values for the kidney and bone were reduced.