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67 y/o with prostate CA who underwent a NM bone scan with 25 mCi of TC99m-MDP
Delayed whole body views

• How do you check for radiochemical impurity?
• How does free pertechnetate degrade images?
• What is the acceptable aluminum concentration?
• What is the acceptable level of Mo-99?

• How do you check for radiochemical impurity?
  Thin-layer chromatography
• How does free pertechnetate degrade images?
  Allowing increases uptake in the soft tissues, thyroid gland, salivary gland, and stomach
• What is the acceptable aluminum concentration?
  Acceptable levels are less than 10 micrograms per millimeters
• What is the acceptable level of Mo-99?
  Microcurie per milicurie of TC99m at the time of dosage administration

• Diagnosis: Free pertechnetate
• Technetium pertechnetate is produced by a Mo-99-Tc-99m generator. The decay is by isomeric transition. The half life is 6 hours, the energy is 140Kev. It is then labeled to a skeletal seeking agent (usually a diphosphonate). This achieved by reducing the technetium so it can form a chelate with the diphosphonate. In this case, there is poor labeling of the bone imaging agent. This may occur as a consequence of inadvertent introduction of air into the multidose vials which decreases the reducing capacity of the stannous ion.
• Free pertechnetate in a Tc-99m bone scan is an example of radiochemical impurity. Such radiochemical impurity can be detected by evaluating the radiopharmaceutical with thin-layer chromatography systems. Chemical purity is different from radiochemical purity. Chemical purity refers to the presence of unwanted ions in the solution. As the generator contains aluminum oxide packing material, aluminum concentration is generally checked for with routine purity evaluations. Acceptable levels are less than 10 micrograms per millimeters. Radionuclide purity refers to the presence of elevated levels of undesirable radionuclides. The nuclear regulatory commission limits the Mo-99 to less than 0.15 microcurie per milicurieof Tc-99m at the time of dosage administration. As in this case, free pertechnetate degrades images by allowing increased uptake in the soft tissues, thyroid gland, salivary gland, and stomach.