Levantamento de doses de radiação ocupacional em exames radiográficos dos boletos e falanges distais de equinos

Resumo

Veterinary medicine has increasingly used X-rays for the diagnosis of various diseases, especially osteoarticular diseases of the fetlocks and distal phalanges. These usually require additional radiographic exposures, resulting in significant radiation doses, which pose a risk to occupational health. This study evaluated radiation doses from primary and scattered radiation, with an emphasis on the ambient dose equivalent (H*(10)) and the personal dose equivalent. It used an X-ray machine typical of veterinary practices, an ionisation chamber, a ring-shaped thermoluminescent dosimeter, and an equine anatomical specimen. Cassettes measuring 18x24 and 35x43 cm were used. The X-ray beam collimations varied in dimensions of 18x24, 24x30, 30x40 and 35x43 cm, in addition to mAs at 5, 2.5 and 1.6. The kVp was kept constant at 70. A higher risk was demonstrated in the D45°L-PaMO oblique radiographic projection. Doses of 0.01882 mSv/exposure were measured in the hand of the IOE carrying the cassette and 0.00026 mSv/exposure for the IOE carrying the X-ray machine, resulting in that to reach the annual investigation level of 150 mSv, it would be necessary to participate in approximately 110 radiographic examinations (patients/month or ± 3 to 4 patients/day) and to reach the monthly investigation level of 20 mSv, approximately 1,063 doses or an average of 5 patients per day would be necessary. The benefit of collimation comparing H*(10) at 70 kVp and 1.6 mAs was demonstrated with collimation 35x43 cm: 0.001013 mSv and 18×24 cm: 0.000223 mSv. The dose is drastically reduced by decreasing the mAs. The dose ratio between the 5 mAs and 1.6 mAs techniques is approximately 5/1.6 ≈ 3.125.