James E. Carlton

A new method for labeling microspheres with 68Ga.

We have developed a simple, highly efficient, and rapid technique for labeling a commercially available human serum albumin microsphere preparation with 68Ga for use in positron tomography. An isotonic acetate buffer system is used. Maximum 68Ga labeling is obtained at pH 4.8 (∼97%) but deviations from that pH (e.g., 0.5 of a pH unit) produce only minor decreases in binding efficiency. The preparation is stable on standing over a period of 4 h, and in vivo studies in the rat and dog show it to be specific for the lungs. Little change occurs in the tissue distribution of 68Ga over a period of approximately 1 h.