Preparation and use of standards for a comparison exercise among users of (131)I capsules in South Africa.

(131)I is widely used as a diagnostic radiopharmaceutical and for radiotherapy in the treatment of thyroid cancer and hyperthyroidism. Radionuclide/Dose calibrators are used to measure activities for administering to patients. To check the accuracy of calibrators operated by South African nuclear medicine facilities, comparison exercises were conducted among users of (131)I capsules. An (131)I solution was standardized by liquid scintillation counting using the absolute 4pibeta-gamma coincidence extrapolation technique. The standardization was transferred to the nml ionization chamber for the geometry of 3.6 ml of solution in a 5 ml glass ampoule. Using this calibration, an ionization chamber calibration factor was determined for (131)I capsules. Two comparison exercises were conducted, one year apart. For each one, four (131)I capsules were calibrated using the previously determined calibration factor. These capsule standards were sent to different provinces in South Africa where they were measured by all participating facilities. The results indicated that more than 90% of the participants showed deviations from the certified value of less than 10%.

Macroscopic and microscopic analysis of the palato-gingival groove.

With the objective of correlating the anatomical aspects of the palato-gingival groove with its etiology, diagnosis, and alternative treatments, 13 permanent maxillary incisors with palato-gingival grooves were selected from a large sample and subjected to macroscopic and microscopic analysis of groove morphology. The palato-gingival groove occurred most frequently on the lingual aspect of the lateral incisor (11 of 13), and its coronal and radicular extensions were on the disto-lingual surface of the incisors (7 of 13 and 6 of 13, respectively). Deformation of the contour of the pulp cavity was noted subjacent to the groove (9 of 13), along with diminished enamel and dentin thickness (11 of 13 and 13 of 13, respectively) and an increase in cement (12 of 13). The groove was observed extending to the apical third in nine specimens, and a direct communication between the pulp and periodontium was observed in only one case. From these examinations it is concluded that the palato-gingival groove can be clinically diagnosed, preventing subsequent problems; however microscopic analysis of the affected tooth is necessary to allow precise evaluation of the groove's extension and damage to the dental structure.