[Absorbed dose evaluation of thyroid during nasopharynx and breast carcinoma irradiation by in vivo dosimetry].
OBJECTIVE
The thyroid dysfunction after radiotherapy has led to evaluate the dose received by thyroid during nasopharynx and breast carcinoma irradiation. This evaluation was facilitated by in vivo dosimetry. The aims of this work were to evaluate the thyroid dose and to compare released dose at the reference point in the two localizations.


METHODS
A total of 30 patients were evaluated: 18 patients with nasopharynx carcinoma and 12 patients with breast carcinoma were included in the final analysis. In the first group, the total thyroid but the isthmus was irradiated. On the other hand, in the second group, only one thyroid lobe was included into the target volume. All patients have been treated by gamma rays of cobalt 60 and the thyroid absorbed dose was measured by semiconductor dosimeters (Scanditronix DPD6). These dosimeters were calibrated in the same geometric conditions of the irradiation.


RESULTS
The measured absorbed dose of the thyroid parenchyma was equal to the calculated absorbed dose at the target that has been specified at a depth of -3 cm. Under the block, the isthmus received 5.1 +/- 0.9 Gy (9.9 +/- 1.8%) in nasopharynx carcinoma irradiation. However, in breast carcinoma irradiation, the distal thyroid lobe and the isthmus received 2.9 +/- 0.7 Gy (6.55 +/- 1.56%) and 3.69 +/- 0.77 (8.39 +/- 1.76%), respectively.


CONCLUSIONS
This study shows that the thyroid received a dose equal to the prescribed dose in both nasopharynx and breast cancer patients. It is recommended to follow the function of the thyroid gland in these patients.
Besbes
M
M
Service de radiothérapie carcinologique, institut Salah-Azaiz, boulevard du 9-avril-Bab-Saadoun, 1006 Tunis, Tunisie.
Siala
W
W
Daoud
J
J
D000328:Adult; D001943:Breast Neoplasms / Q000532:radiotherapy*; D002277:Carcinoma / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008297:Male; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy*; D011832:Radiation Injuries; D011874:Radiometry; D013959:Thyroid Diseases / Q000209:etiology; D013961:Thyroid Gland / Q000528:radiation effects