Measurement and verification of strength of monomodal high-dose rate (mHDR)¹⁹² Ir source supplied by the vendor is a major part of quality assurance program. Reference air kerma rate (RAKR) or air kerma strength (AKS) is the recommended quantity to specify the strength of gamma emitting brachytherapy sources. Physicist in our institution performed the source calibration as soon as each ¹⁹² Ir new source was loaded on the mHDR afterloading machine. The AKS accurately measured using a physikalisch technische werkstatten (PTW) re-entrant chamber-electrometer system in a scatter-free geometry was used to compute the air kerma rate (AKR) at one-meter distance in the air. To ensure accurate dose delivery to brachytherapy patients, measured AKS or RAKR should be entered correctly in both HDR treatment console station (TCS) as well as treatment planning system (TPS) associated with it. The clinical outcome mainly depends not only on the accuracy of the source strength measurement in the hospital but also on the correct source strength entered into both TCS and TPS software. A retrospective study on 22 mHDR V2 sources supplied by the vendor for the period of 10 years was taken up to access the accuracy of source strength supplied to the Radiotherapy department. The results are analyzed and reported. The accuracy in measured RAKR of all 22 sources supplied by vendor was well within the tolerance limits set by the national regulatory body and international recommendations. The deviations observed between measured RAKR versus manufacturer's quoted RAKR were in the range from −1.71% to +1.15%. In conclusion, the measured RAKR have good agreement with vendor quoted RAKR values.

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Human beings are continuously exposed to the radiations coming from terrestrial and extraterrestrial sources and inside their own bodies. This study presents the results of indoor and outdoor ambient gamma dose rates in and around granite regions of Shimoga District, and these measurements were carried out by using environmental radiation Dosimeter ER-709 which is a portable detector. By the measured average absorbed dose rates, annual effective dose (AED) has been calculated by a standard method. Results showed that the indoor and outdoor absorbed dose rates in air of Shimoga district ranged between 114.05 ± 2.11 to 332.6 ± 3.99 nGy/h and 87 ± 1.7 to 276.66 ± 4.76 nGy/h. The indoor and outdoor AED ranged between 0.559 to 1.631 mSv/year with an average value of 0.872 mSv/year and 0.106 to 0.339 mSv/year with an average value of 0.235 mSv/year, respectively. The calculated indoor and outdoor AEDs were found to be higher than the world average.

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In the synchrotron radiation source ring tunnel, various types of radiation such as bremsstrahlung photons, photo-neutrons, electrons and positrons are present due to the interaction of high energy electrons with structural material as well as gas molecules in a vacuum chamber and also due to cascade production. In this study, an attempt was made to quantify the bremsstrahlung photon dose inside the ring tunnel using direct reading dosimeters and thermoluminescent dosimeters.

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Various analytical functions proposed to express the full energy photopeak efficiency (FEPE) of gamma ray detectors have been investigated for their performance to fit the percentage FEPE of Amcrys-H made 2” × 2” NaI(Tl) scintillation detector. Initially, the experimental measurements on FEPEs of various gamma sources were used to validate the theoretical Monte Carlo (MC) simulations. The maximum deviation observed between the experimental efficiencies and MC simulations is -12.51%, which is observed for 356 keV of 133Ba. The percentage FEPEs obtained through validated MC simulations are then fitted against gamma energy in the range 122–1332 keV using the recommended efficiency functions to obtain the percentage FEPE as a smooth function of gamma energy for the source to detector distance of 5 cm. The analytical function recommended by McNelles, Campbell and Singh is identified as the most suitable for the detector type considered and this, in turn, is used to obtain fitting coefficients for all other source to detector distances. The fitted equations are found to provide the percentage FEPEs, which are well within ±6% deviation with respect to the theoretical MC simulations for most of the energies and distances. For the source to detector distances of 15 and 25 cm, the gamma energy of 500 keV is found to have the maximum deviations up to 7.6%.

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Oral squamous cell carcinoma is the sixth most common cancer reported globally, with an annual incidence of over 300,000 cases, of which 62% arise in developing countries. Radiation therapy is a treatment modality that uses ionizing radiation as a therapeutic agent. It is widely employed in the treatment of head and neck cancer, as a primary therapy coupled with surgical procedure and chemotherapy or as a palliative treatment for advanced tumors. However, radiotherapy can cause a series of complications such as xerostomia, mucositis, osteoradionecrosis, and radiation caries. Composite circular disc containing different ratios of acrylic and barium sulfate (BaSO₄) were made in-house. The purpose of this study was to evaluate the percentage attenuation from these composite shields in ⁶⁰ Co gamma rays. A maximum of 8% radiation attenuation was achieved using 1:4 ratio of acrylic-BaSO₄ composite shields. The study proposes BaSO₄ as one of the compounds in combination with acrylic resin or any other thermoplastic substances for making biocompatible radiation attenuating devices.

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To analyze the dose absorption patterns of 6 Megavoltage (MV) photon beam using computed tomography (CT) slices of thorax of patient, slab phantom, and slab–kailwood–slab phantom. Single beam of 6 MV with field size of 10 × 10 cm ² was put on CT images of chest wall, slab phantom, and slab–kailwood–slab phantom perpendicular to the surface. Dose was calculated using anisotropic analytical algorithm. Densities of each medium were calculated by Hounsfield units measured from CT images of each medium. The depths of isodose curves of 100%, 95%, 90%, 85%, 80%, 70%, 60%, and 50% were measured in all the three mediums. The densities measured for chest wall, lung, Soft tissue behind lung, slab phantom, and slab–kailwood-slab phantom were 0.89, 0.301, 1.002, 0.998, and 0.379 g/cc, respectively. The isodose depth (100%, 95%, 90%, 85%, 80%, and 50%) for patient (1.5, 2.76, 3.97, 5.33, 7.01, and 20.01 cm), slab phantom (1.5, 2.74, 3.92, 5.06, 6.32, and 15.18 cm), and slab–kailwood–slab phantom (1.5, 2.65, 3.86, 4.98, 5.95, and 20 cm) is approximately same for 100%, 95%, 90%, and 85% isodose curves. The isodose depth pattern in the chest is equivalent to that in slab–kailwood–slab phantom. The radiation properties of the slab–kailwood–slab phantom are equivalent to that of chest wall, lung, and soft tissue in actual human. The chest phantom mimicking the actual thoracic region of human can be manufactured using polystyrene and the kailwood.

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The effects of gamma irradiation of various levels on the current-voltage characteristics for the (In₂O₃)_0.1 (TeO₂)_0.9 thin films, prepared by thermal evaporation in vacuum, have been studied in detail. The current increases linearly with the gamma radiation dose up to certain dose and decreases thereafter. The sensitivity of these thin films, at different applied voltages in the range 0–4.8 V, has been found to be in the range 35–190 mA/cm ²/Gy. Correspondingly, the minimum measurable dose has been found to be in the range 0.05–0.26 mGy. The values of the sensitivity are reasonably high in comparison to the commercially available gamma radiation dosimeters, revealing high scope for further developments.

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International Commission for Radiological Protection (ICRP), issued a statement on Tissue Reaction, lowering the equivalent dose limit for eye lens for occupational exposure to 20 mSv per year. With a view to determine presence of any relationship between the cumulative low-level occupational radiation dose to the eye lens and occurrence of cataract, departmental records of the annual medical examination of employees of Narora Atomic Power Plant were examined along with the NAPS eye camps and surgical records of the employees. Analysis of the data showed no demonstrable definite relationship between the two. The analysis of the data and the observations are discussed in this paper.

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ICRP now recommends an equivalent dose limit for the lens of the eye of 20 mSv in a year, averaged over defined periods of 5 years, with no single year exceeding 50 mSv. In December 2013, IAEA brought out a TECDOC-1731, entitled “Implications for occupational radiation protection of the new dose limit for the lens of the eye,” providing interim guidance for application of the limit in operational settings of planned exposure situations. This brief review article is an attempt to bring out salient features of document for the benefit of the readers and operational radiation protection personnel.

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