Tumor uptake and biodistribution of various radiolabels

42K, 86Rb, 134Cs and 201Tl accumulated in viable tumor tissue and not in necrotic tumor tissue. 22Na, however, accumulated in necrotic tumor tissue. These elements existed almost as free ions in the tissues. The ions of 67Ga, 111In, 169Yb and 167Tm, which are hard acids, were predominant in connective tissue (especially inflammatory tissue) rather than in viable tumor tissue and were not seen in necrotic tumor tissue. These ions were bound to the acid mucopolysaccharide with a molecular weight of about 10,000 dalton in tumor and other soft tissues. The ions of 46Sc, 51Cr, 103Ru, 95Zr, 181Hf, 95Nb, 182Ta and 58Co, which have incomplete d-shells, were much more dominant in connective tissue (especially inflammatory tissue) than in viable and necrotic tumor tissue. They tended to accumulate into the lysosome of malignant tumor cells. They were bound to the acid mucopolysaccharides whose molecular weights exceed 40,000 dalton. The ions of 65Zn and 103Pd, which are soft acids, mainly accumulated in viable tumor tissue.