Background 99mTc-MAA (Pulmocis) is a compounded radiopharmaceutical indicated in lung scintigraphy. It can be used in infants and children, with dose adjustments made based on weight. The European Association of Nuclear Medicine (EANM) recommends reducing the number of administered particles depending on age in order to embolise no more than 0.1% of the total lung capillary vessels.
Therefore, removing an amount of particles before labelling it with 99mTc is needed. We used two different protocols: half of the MAA was removed for infants and children older than 1 month (P1) and four-fifths for infants younger than 1 month (P2).
Purpose This additional step in compounding the 99mTc-MAA was not included in the manufacturer’s instructions. Our goal was to validate the preparation protocols for paediatric use by controlling the quality of the preparations.
Material and methods Three different preparations were analysed for each protocol, and 3 samples were tested at T=0, T=0.5 h and every hour until T=8h, resulting in 30 samples for each preparation. Radiochemical purity (RCP), which assesses labelling efficiency, was determined with thin layer chromatography (17CHR paper, methylethylketone as the mobile phase, scanned with a radiochromatograph). The mean and SD of RCP obtained at each time point were calculated. A pH paper was used for pH determination. The preparation had to comply with a level of 95% RCP and pH levels between 5 and 7.
Results 180 samples were analysed: 100% had RCP >95% and pH between 5 and 7. Mean RCP for all samples was between 98.75 ± 0.10% and 99.15 ± 0.32% for P1 and between 98.60 ± 0.41% and 99.12 ± 0.24% for P2.
This study validated our 99mTc-MAA preparation protocols for paediatric use. The protocols did not follow the manufacturer’s instructions but fulfilled EANM guidelines. For some teams, however, questions remain about the need to adapt the number of injected MAA for children older than 2 years as studies have shown that lung maturation ends between the ages of 2 and 8 years.
Conclusion Removing a portion of MAA before adding 99mTc does not alter 99mTc-MAA labelling efficiency. These protocols can be used to put in practice current EANM guidelines.
No conflict of interest.
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