We propose to perform periodic diagnostic TBS to improve Tg specificity, at least while neck thyroid activity is detected, even if Tg is negative.

Our objective was to determine the stability of stabilized 99m Tchexamethylpropylene amine oxime ( 99m Tc-D,L-HMPAO) dispensed by vial and syringe, with the storage time and labeling activity varied. Methods: 99m Tc-D,L-HMPAO was labeled according to the manufacturer's instructions, but with modification of the 99m TcO 4 Na activity. Two groups were prepared: 1,110 MBq (30 mCi) and 2,600-3,700 MBq (70.3-100 mCi). Five minutes after labeling, the radiochemical purity (RCP) of the vial content was determined. Afterward, the same activity was distributed into two 2-mL syringes and into the manufacturer's vial. In one of the syringes, the radiopharmaceutical stayed in contact with the needle for 4 h. At 2 and 4 h after labeling, the RCP of the vial and syringe content was checked and compared. Results: The mean RCP of stabilized 99m Tc-D,L-HMPAO labeled with 1,110 MBq (30 mCi) and stored in a vial decreased from 93.1% at 5 min to 92.1% at 2 h and to 91.1% at 4 h. With storage in a syringe, the RCP decreased from 89.8% at 2 h to 88.7% at 4 h. This diminution increased for labeling with higher activities (2,600-3,700 MBq [70.3-100 mCi]), ranging from 91.4% at 5 min, 89.0% at 2 h, and 85.3% at 4 h in a vial and from 85.9% at 2 h to 80.2% in a syringe. 99m TcO 2 and secondary 99m Tc-HMPAO were the main impurities at t 5 0. 99m TcO 4 2 was an impurity that increased with time in both vials and syringes but significantly so in syringes. All these impurities were higher with labeling activities in the range of 2,600-3,700 MBq (70.3-100 mCi). Contact of the needle with 99m Tc-D,L-HMPAO sharply decreased the RCP to 57.1% at 4 h. Conclusion: The RCP of stabilized 99m Tc-D,L-HMPAO decreases significantly in both vials and syringes with high labeling activities. The product is less stable when stored in a syringe than in a vial. The fraction of dose in contact with the needle affects the RCP results.

Radionuclide oesophageal transit time was evaluated in 70 individuals, divided into three groups: normal individuals, patients with non-organic dysphagia and patients with primary oesophageal motility disorders treated with per-endoscopic forced pneumatic dilatation. In all of them the oesophageal transit time of a bolus of water with 18.5 MBq (500 microCi) of 99Tmc sulphur colloid was assessed, as was the percentage of residual activity of the bolus in the oesophagus. There was a significant difference in these parameters between the control group and the group with non-organic dysphagia, the diagnostic capacity of this test being 93% sensitivity, 100% specificity, 100% positive predictive value and 90% negative predictive value, which suggests its inclusion in diagnostic protocols of dysphagias. In patients with primary oesophageal motility disorders, a significant decrease in values of residual activity has been observed after treatment with per-endoscopic forced pneumatic dilatation.