ABSTRACT
Background and aim: Nowadays, thyroid exposure is a major concern in skull radiological imaging. The aim of this study was to evaluate thyroid exposure in brain CT-scan and skull X-ray, using different levels of Kvp [Kilovoltd peak] and mA, with and without thyroid shield
Methods: In this descriptive- analytic study, 350 outpatients were selected randomly. Two TLD-100 chips [Thermo Luminescence Dosimeter] were placed on the thyroid of each patient. Three levels of mA were applied in brain CT-scan [210 patients] and two levels of Kvp were used in routine skull X-rays [140 patients]. The experiments were performed with and without thyroid shield. The TLDs were read and the statistical analysis was performed using student-t test
Results: During brain CT-scan, decreasing current intensity from 150 to 125 mA, significantly decreased the thyroid exposure from 101+/-9.38 to 82.2+/-8.04 mili rem [P<0.01]. Using a thyroid shield extremely reduced the thyroid exposure to 29+/-5.83 mili rem [P<0.01]. In routine skull x-rays, increasing voltage from 60 to70 Kvp, significantly decreased the thyroid exposure from 72.6+/-7.74 to 67+/-8.41 mili rem [P<0.05]. Moreover, using the thyroid shield remarkably reduced the thyroid exposure to 19.6+/-1.82 mili rem [P<0.05]
Conclusions: Using lower levels of mA in brain CT-scans and higher levels of Kvp in skull X-rays, decrease thyroid exposure. Furthermore, using thyroid shield during X-ray examinations of the skull remarkably reduces thyroid exposure
ABSTRACT
To evaluate the effects of hyperthermia [HT] on the frequency of chromosomal aberrations induced by a low dose of neutron or gamma-rays in human peripheral blood lymphocytes. Blood samples were exposed to HT [41.5°C for 30 and 60min, 43°C for 15 and 30min], 10 cGy neutron or gamma-rays, HT + neutron/gamma, and neutron/gamma + HT. After standard cell culture, harvesting, fixation and staining, the chromosomal damages were scored in metaphase plates. HT alone at 41.5°C did not induce chromatid or chromosome aberrations, however, the frequency of damages was significantly higher at 43°C [P<0.05]. Furthermore, the chromosomal damages was significantly different when cells were irradiated with neutron or gamma-rays alone [P<0.01]. HT 1 hr post neutron/gamma irradiation significantly induced higher chromosome damages in comparison to HT 1 hr before irradiation [P<0.05]. The chromosomal damages were remarkably higher when cells were irradiated with neutron then heated at 43°C for 30 min. Since increasing frequency of chromosome damages increases probability of cell death, application of HT after neutron irradiation [instead of X-or gamma-rays] might be considered as a procedure for cells killing in radiotherapy