A Fast Way of Determination of ~202Tl impurity in ~201Tl Radiopharmaceutical

摘要

Introduction: In production of ~201Tl by cyclotron, the long-lived ~202Tl and short- lived ~200Tl are usually present as impurity. In routine radionuclidic quality control, a sample containing 20-100 mul of thallium-201 solution in the final step of chemistry process is diluted and then detected by high pure germanium (HPGe) detector. This process takes about 1 hour and leads to significant absorption dose for technician who does this job.Material and Method: Detection of ~202Tl in a lead container has introduced by Bonardi (2001). We have developed the Bonardi's method, for detection of ~201Tl and ~202Tl using a HPGe detector with the 3 to 7 mm lead shields for the both aspects of quantity and quality.At first ~201Tl purity was determined by usual method, later on we repeated measurement by using different thicknesses of lead shields.Results and Discussion: Comparing the results of two (new and routine) methods, correction coefficients for determination of real ~201Tl and ~202Tl impurity in the case of using lead shields were obtained. Errors related to dead-time, Compton continuum and X-ray fluorescence background were very efficiently avoided and omitted. This rapid and simple method allows determination of ~202Tl in ~201Tl with sufficient accuracy in short time. In this method not only, radiation exposure to the technicians reduced but also time of quality control process reduced to about 10 minutes in comparison with 1 hour for routine procedure.