Routine application of fractionated HMPAO stored at -70 degrees C for WBC scintigraphy.

The radiochemical purity of 99mTc-HMPAO prepared from fractions of reconstituted HMPAO stored at -70 degrees C and its application in the radiolabeling of human granulocytes was investigated. Upon reconstitution of a vial of HMPAO with 1 ml of saline and subsequent freezing at -70 degrees C, small fractions were obtained on each of four consecutive days with the vial being refrozen after each dispensing. Following radiolabeling of the HMPAO fractions with pertechnetate, mean radiochemical purity results met or exceeded manufacturers' specifications for the radiopharmaceutical on each of the four days. Imaging with radiolabeled granulocytes using 99mTc-HMPAO prepared by this technique resulted in high quality clinical studies. These results demonstrate that a vial of HMPAO can be fractionated, after storage at -70 degrees C with no loss of clinical utility for radiolabeling granulocytes and considerable cost savings.