Quality and pratical determinants in [^99mTc]Tc-tetrofosmin preparation: hygrometry, syringe sorption & maximal...

Tetrofosmin, labelled with technetium-99m ([^99mTc]Tc-tetrofosmin), is a widely used radiopharmaceutical for myocardial perfusion imaging. Despite its routine use, several practical aspects of its preparation remain insufficiently characterized. This study addressed three operational issues: (i) the potential impact of environmental hygrometry on radiochemical purity assessment using ITLC-SA, as current guidelines provide no recommendations for humidity during quality control; (ii) the extent of sorption in medical syringes, comparing two-part and lubricated three-part syringes due to the lipophilic nature of tetrofosmin; and (iii) the radiochemical conformity of preparations performed with activities exceeding the 12-GBq limit stated in the manufacturer's instructions.

Hygrometry > 60% brings 99.7% nonconformities with ITLC-SA test strip of the [^99mTc]Tc-tetrofosmin quality control. Measures show significant superiority of 3P syringe mean sorptions over 2P syringes, with successive rinses and two different infusion time points. However, all measured sorption was under 10%, considered as clinically acceptable. Median activity was 17.31 GBq over a 1-year period, while the product instructions allow for a maximum 12 GBq per kit. All quality controls were conforms, demonstrating possibility to overcharge kits and improve maximal activity.

Hygrometry is clearly a major parameter and should be not only monitored but controlled like pressure or temperature. There is a significant superiority about [^99mTc]Tc-tetrofosmin sorption in 3P syringes compared to 2P syringes. However, less than 10% sorption difference cannot be considered as clinically significant. 3P syringes are probably not as problematic as it seems for [^99mTc]Tc-tetrofosmin preparations. The increase of maximal activity per tetrofosmin kit doesn't shows nonconformities about [^99mTc]Tc-tetrofosmin preaparation and conserve safety of use for professionals and patients.