Preparation and evaluation of a hydrous tin(IV) oxide 82Sr/82Rb medical generator system for continuous elution

Hydrous tin(IV) dioxide in the Na+-form appears to be the most efficient inorganic exchanger for a reliable and versatile clinical 82Rb generator. Continuous elution with a commercial physiological NaCl solution yields 82Rb ranging between 10 and 40% at a flow rate as low as 3 to 10 mL/min respectively. At the same time the Sr breakthrough is less than 1.6 10(-6)%/mL. A clinical generator loaded with 100 mCi 82Sr (150 mCi 85Sr) and continuously eluted for 3 min at a typical flow rate of 5 mL/min yields 40 mCi of 82Rb, 8 nCi of 82Sr and 11 nCi of 85Sr. The total absorbed radiation dose for 40 mCi 82Rb administered is primarily due to 82Rb and has been estimated for the three principal target organs as 760 mrad for the kidneys, 520 mrad for the heartwalls and 276 mrad for the lungs. The 82,85Sr contribution to the dosimetry has been shown to be negligible. The absence of radiolysis with generators loaded with high level of 82Sr was demonstrated by the excellent reproductibility of continuous elution properties of the generator during its practical shelf-life estimated to 5-6 weeks of clinical use which would require more than 30 L of eluent.