Objective. Although several studies have investigated the association between body mass index (BMI) and bone mineral density (BMD), the results are inconsistent. The aim of this study was to further investigate the relation between BMI, weight and BMD in an Iranian men population. Methods. A total of 230 men 50-79 years old were examined. All men underwent a standard BMD scans of hip (total hip, femoral neck, trochanter, and femoral shaft) and lumbar vertebrae (L2-L4) using a Dual-Energy X-ray Absorptiometry (DXA) scan and examination of body size. Participants were categorised in two BMI group: normal weight <25.0 kg/m2 and overweight and obese, BMI ≥ 25 kg/m2. Results. Compared to men with BMI ≥ 25, the age-adjusted odds ratio of osteopenia was 2.2 (95% CI 0.85, 5.93) and for osteoporosis was 4.4 (1.51, 12.87) for men with BMI < 25. It was noted that BMI and weight was associated with a high BMD, compatible with a diagnosis of osteoporosis. Conclusions. These data indicate that both BMI and weight are associated with BMD of hip and vertebrae and overweight and obesity decreased the risk for osteoporosis. The results of this study highlight the need for osteoporosis prevention strategies in elderly men as well as postmenopausal women.
This study aimed to determine the neutron dose equivalent to the thyroid gland and eye lens in brain tumor radiation therapy with 15- and 18-MV three-dimensional conformal methods (3D-CRT). A Monte Carlo simulation was performed using the Monte Carlo N-particle transport code to calculate neutron fluence and ambient dose equivalent (H*(10)). Afterward, these parameters were measured using a model NRD roentgen equivalent in man (REM) neutron detector (Thermo Electron Corporation, USA) equipped with Eberline’s ASP-2e rate meter. Finally, the organ neutron dose equivalent was obtained by applying depth corrections to the measured ambient dose equivalent at the distance of the organ center from the central beam axis. The ratio of the out-of-field photon dose equivalent, measured previously, to the neutron dose equivalent in the eye lens was high due to its proximity to the radiation field. In contrast, this ratio remained unexpectedly high in the thyroid gland that is far from the central beam axis (about 15 cm). The calculated neutron parameters agreed with the measurements. The present study findings indicate that external field photon dose is the main source of thyroid gland biological effects in radiotherapy of brain tumors. In addition, it is appropriate to apply the model NRD REM neutron detector for measuring neutron contamination from high-energy linear accelerators inside and outside the treatment field.
Investigating the out-of-field doses and estimating the risk of secondary thyroid cancer in high-grade gliomas radiation therapy with modulated intensity and 3D-conformal: a phantom study
INTRODUCTIONRadiation therapy is an adjuvant treatment for malignant gliomas that increases median survival in patients (1) . Any type of radiation therapy results in the out-of-field radiation of photons and treatment beams with energies above the threshold of reaction (photon, n) result in neutrons (2)(3)(4) . In the medical linear accelerator (LINAC), out-of-field photon radiation includes scattered photons of the collimator and the patient and the leakage of the LINAC head (5) . Around the field edge, radiation scattering from both the patient and the collimator is the main source of out-of-field photon radiation. At a distance away from the field edge, the collimator leakage remains as radiation outside the field (6) . Out-of-field doses in high-grade gliomas radiation therapy may induce side effects, mainly second cancers and eye abnormalities (7)(8)(9) . Thyroid cancer is one of the most prevalent malignancies caused by neck and head radiation therapy (10,11) . Therefore, it is necessary to determine the photon dose to out-of-field critical organs. However, the treatment planning system (TPS) cannot estimate out-of-field photon doses and in-vivo dosimetry should be prescribed for measuring
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