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Radiolabelling with 99mTc & Calculation of Doses

Radiolabelling is the stage at which the radiopharmaceutical is prepared by mixing the radioactive eluate (99mTc in the chemical form of pertechnetate in a 0.9% NaCl solution; see Eluting the generator) with the selected labelling kit (see Selection of labelling kit).

In order to have sufficient activity to prepare the necessary patient doses of 99mTc-MDP, the volume of 99mTc to be withdrawn from the eluate vial must be calculated (see radioactive calculations for information).

Once the required volume of eluate has been calculated, labelling with 99mTc can be performed. The preparation of 99mTc-MDP requires that the calculated volume of eluate is withdrawn from the eluate vial and diluted to an appropriate volume (to be dispensed into doses more easily) with sterile saline solution (a solution containing 9 g/l of sodium chloride). This diluted solution of 99mTc in the form of pertechnetate is then added to an MDP labelling kit.

You can view these steps in more detail and test your understanding of the procedures, in consideration of Good Radiopharmacy Practice, in the following slideshows (withdrawing 1.9 ml of the eluate from the eluate vial, as in the example calculation):

Part 1: Review of materials required for the preparation of 99mTc-MDP
Part 2: Disinfection of labelling vial and eluate vial and uncapping of saline vial
Part 3: Preparation of syringe with needle and lead glass syringe shield
Part 4: Withdrawal of the dose in a syringe
Part 5: Dilution of the solution in the syringe to the required volume
Part 6: Addition of the activity to the labelling kit and incubation
Part 7: Control of the radioactivity in the preparation and completion of the label

Find out about the chemical processes that occur during the incubation stage when radiolabelling with 99mTc.

Find out how the final radiopharmaceutical may contain radiochemical impurities.