Comparison of thermoluminescent dosimeter calibration irradiated in gamma knife and 60Co instruments.

AIM: By necessity of dosimeters calibration for evaluating delivered dose accuracy to organs out of the radiation field in patients undergoing gamma knife radiosurgery, we calibrated thermoluminescence dosimeters in gamma knife and 60Co instruments, and then, compared both results to investigate when one of these devices was out of reach, can we use one of this instruments instead of the ther. MATERIALS AND METHODS: To individual calibration by 60Co, thermoluminescent dosimeters (TLDs) were placed in a Perspex sheet with conditions of source-skin distance = 80 cm, field size = 10 cm × 10 cm, and dose = 100 cGy. For individual calibration by Gamma knife, TLDs placed in flat Perspex were located in a special sphere and were exposed with conditions of source to axis distance = 40 cm, field size = 18 mm, and dose = 100 cGy, and for group calibration, TLDs were divided into six groups and were exposed with doses of 0-1000 cGy in both devices. RESULTS: According to Fisher's exact test, calculated P = 0.27, so the difference is not significant. CONCLUSIONS: The result showed despite differences in calibration conditions, 60Co unit can be used to calibrate TLD dosimeter for estimating the accuracy of measurement of delivered dose to organs of patients undergoing Gamma Knife 4C radiosurgery treatment.

Radio-Protective Effects of Melatonin on Subventricular Zone in Irradiated Rat: Decrease in Apoptosis and Upregulation of Nestin.

Neural stem cells are self-renewing, multipotent cells that can be found in subventricular (SVZ) and subgranular (SGZ) zones of the brain. These zones are susceptible to irradiation-induced apoptosis and oxidative stress. Melatonin (MLT) is a natural protector of neural cells against toxicity. The aim of this study was to evaluate the effects of MLT as a radio-protective material effective in reducing tissue lesions in the SVZ of the brain and changing local apoptotic potential in rats. Twenty-five Gray irradiation was applied on adult rat brain for this study. One hour before irradiation, 100 mg/kg/IP MLT was injected, and 6 h later, the animals were sacrificed. The antioxidant enzymes and MDA activity levels were measured post-sacrifice. Also, the expression level of Nestin and caspase 3 were studied by immunohistochemistry. Spectrophotometric analysis showed significant increases in the amount of malondialdehyde (MDA) levels in the irradiation-exposed (RAD) group compared to that of the control (Co) group (P < 0.05). Pre-treatment with MLT (100 mg/kg) ameliorates the harmful effects of the aforementioned 25 Gy irradiation by increasing antioxidant enzyme activity and decreasing MDA levels. A significant reduction in apoptotic cells was observed in rats treated with MLT 1 h before exposure (P < 0.001). Nestin-positive cells were also reduced in the RAD group (P < 0.001). Our results confirm the anti-apoptotic and antioxidant role of MLT. The MLT concentration used may serve as a threshold for significant protection against 25 Gy gamma irradiations on neural stem cells in SVZ.

Dental treatment needs of permanent first molars in mashhad schoolchildren.

BACKGROUND AND AIMS: In spite of their enormous importance, permanent first molars might be affected by caries in children in developing countries. The aim of this study was to evaluate the treatment needs of first permanent molars in a group of schoolchildren in Mashhad. MATERIALS AND METHODS: This cross-sectional descriptive study was carried out on 700, 7-9 year-old students in primary schools in Mashhad. The schools were randomly selected from each district. Treatment needs and DMFT of first perma-nent molars were calculated. Data was analyzed using ANOVA, Chi-Square and t-test. RESULTS: A total of 95.3% of the children required dental treatment. Fissure sealant application and filling were the treat-ments most required in all age groups. The mean DMFT of first permanent molars was 1.31±1.4. It was significantly higher in girls than boys (P=0.040). CONCLUSION: Great treatment needs and caries prevalence in permanent first molars in Mashhad schoolchildren show that dental caries is still a serious problem in the children of our society; therefore, education of parents and teachers is necessary for promoting children's oral health.