A crossover study comparing the effect of particle size on the distribution of radiocolloid in patients.

Two radiocolloid preparations, differing in particle size by a factor of 5 to 20, were compared in each of 15 patients. The smaller colloid, measuring less than 80 nm, showed a relative decrease in the calculated target to background ratios for the liver and spleen and an increase for the bone marrow. The increased uptake of the smaller particle in the bone marrow, as measured by the bone marrow to soft-tissue background ratio, was about 50% higher than that of the larger colloidal particles. Comparable marrow images can be obtained in a half to a third of the time with the smaller particle size for a given administered dose.