Calculation of individual patient doses
In our example, five patients are scheduled, each of them to be injected with 750 MBq of the preparation at 8.00 a.m., 8.30 a.m., 9.00 a.m., 9.30 a.m. and 10.00 a.m., respectively. The radioactivity of these doses at 7.15 a.m. (the time of reconstitution of the 99mTc-MDP preparation) was calculated to be 818 MBq, 866 MBq, 918 MBq, 972 MBq and 1030 MBq, respectively.
At 7.15 a.m. (the time of reconstitution) the 99mTc-MDP preparation was calculated to contain 5064 MBq of technetium-99m in a volume of 10 ml, which can be interpreted as 506 MBq per ml.
In order to calculate the volume of the preparation that has to be withdrawn from the 99mTc-MDP preparation for the respective individual patient doses, the radioactivity for each dose (in MBq) should be divided by the radioactive concentration of the preparation (in MBq per ml).
Thus, the volumes to be withdrawn for each patient are calculated as follows:
- Dose for patient at 8.00 a.m. = 818 MBq / 506 MBq/ml
= 1.62 ml
- Dose for patient at 8.30 a.m. = 866 MBq / 506 MBq/ml
= 1.71 ml
- Dose for patient at 9.00 a.m. = 918 MBq / 506 MBq/ml
= 1.81 ml
- Dose for patient at 9.30 a.m. = 972 MBq / 506 MBq/ml
= 1.92 ml
- Dose for patient at 10.00 a.m. = 1030 MBq / 506 MBq/ml
= 2.0 ml
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