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PURPOSE: Investigation of surface dose rate variation with respect to the source configuration of 106Ru/106Rh eye plaque. To explore an alternate way to determine activity of brachytherapy plaques. METHODS: The surface dose rates of 106Ru/106Rh plaque developed indigenously were measured by extrapolation chamber. To rule out possibility of any error in the activity distribution and quantity, same source was used in two different configurations namely planar and curved. EBT3 Gafchromic film was used for determination of uniformity in activity. Monte Carlo-based Codes EGSnrc and FLUKA were used to calculate dose rate in tissue, percentage depth dose and for determination of activity. Parameters and correction factors were estimated using simulations. RESULTS: The measured reference absorbed dose rates for planar and curved 106Ru/106Rh eye plaques are found to be 589 ± 29 mGy/h and 560 ± 28 mGy/h, respectively. The difference in the reference absorbed dose rate of curved eye plaque is about ~5% as compared to planar configuration. The FLUKA-calculated dose values are almost independent of cavity length of the extrapolation chamber for both eye plaques. The FLUKA-based dose rates per µCi 106Ru/106Rh are about 17.28 ± 0.08 mGy/h and 16.48 ± 0.06 mGy/h, respectively for planar and curved eye plaques which match well with the measurements. The calculated activities for planar and curved eye plaques are 34.08 µCi and 33.98 µCi, respectively. CONCLUSIONS: Surface dose rates for a prototype 106Ru/106Rh eye plaque with different configurations were estimated using simulations and measured experimentally. An alternate way to determine activity of beta-gamma brachytherapy plaque has been proposed.

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This paper describes the evaluation of dosimetry characteristics of an in-house developed 177Lu skin patch source for treatment of non-melanoma skin cancer. A 177Lu skin patch source based on Nafion-115 membrane backbone containing 3.46 ± 0.01 mCi of activity was used. Activity measurement of the patch source was based on gamma ray spectrometry using a HPGe detector. The efficiencies of the HPGe detector were fitted using an orthogonal polynomial function. The absorbed dose rate to water at 5 µm depth in water was determined using an extrapolation chamber, EBT3 Gafchromic film and compared with Monte Carlo methods. The correction factors such as Bragg-Gray stopping power ratio of water-to-air and chamber wall material being different from water, needed to be applied on measurements for establishing the dose rate at 5 µm depth, were calculated using the Monte Carlo method. Absorbed dose rate at 5 µm depth in water (surface dose rate) measured using an extrapolation chamber and EBT3 Gafchromic film were 9.9 ± 0.7 and 8.2 ± 0.1 Gy h-1 mCi-1 respectively for the source activity of 3.46 ± 0.01 mCi. The surface dose rate calculated using the Monte Carlo method was 8.7 ± 0.2 Gy h-1 mCi-1, which agrees reasonably well with measurement. The measured dose rate per mCi offers scope for ascertaining treatment time required to deliver the dose for propitious therapeutic outcome. Additionally, on-axis depth dose and lateral dose profiles at 5 µm and 1 mm depth in water phantom were also calculated using the Monte Carlo method.

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AIM: To assess the effect of combining 0.2% chlorhexidine (CHX) mouthwash with xylitol (XYL) chewing gum on Streptococcus mutans and biofilm levels among 8- to 12-year-old children. MATERIALS AND METHODS: Sixty children aged 8 to 12 years were selected with moderate and high salivary S. mutans levels. They were divided into three groups of 20 children each: (1) XYL group where the subjects chewed XYL twice daily; (2) CHX where rinsing was done twice daily; and (3) combination of XYL and CHX group (XYL+CHX) where both the agents were used once daily. The S. mutans colony-forming units (CFUs) were counted by using the mitis salivarius agar plate at the beginning of the study and at 15 days, 1, 2, and 6 months from the start of the study. RESULTS: The XYL+CHX group showed the maximum reduction in both the biofilm and S. mutans scores throughout the study period. CONCLUSION: The XYL+CHX combination reduced both the biofilm and S. mutans score significantly better than either XYL chewing gums or CHX mouthwash used alone. HOW TO CITE THIS ARTICLE: Syed M, Chopra R, Shrivastava V, Sachdev V. Comparative evaluation of 0.2% Chlorhexidine Mouthwash, Xylitol Chewing Gum, and Combination of 0.2% Chlorhexidine Mouthwash and Xylitol Chewing Gum on Salivary Streptococcus mutans and Biofilm Levels in 8- to 12-Year-Old Children. Int J Clin Pediatr Dent 2016;9(4):313-319.

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Absorbed dose rate to water at 0.2 cm and 1 cm due to a point isotropic photon source as a function of photon energy is calculated using the EDKnrc user-code of the EGSnrc Monte Carlo system. This code system utilized widely used XCOM photon cross-section dataset for the calculation of absorbed dose to water. Using the above dose rates, dose rate constants are calculated. Air-kerma strength Sk needed for deriving dose rate constant is based on the mass-energy absorption coefficient compilations of Hubbell and Seltzer published in the year 1995. A comparison of absorbed dose rates in water at the above distances to the published values reflects the differences in photon cross-section dataset in the low-energy region (difference is up to 2% in dose rate values at 1 cm in the energy range 30-50 keV and up to 4% at 0.2 cm at 30 keV). A maximum difference of about 8% is observed in the dose rate value at 0.2 cm at 1.75 MeV when compared to the published value. Sk calculations based on the compilation of Hubbell and Seltzer show a difference of up to 2.5% in the low-energy region (20-50 keV) when compared to the published values. The deviations observed in the values of dose rate and Sk affect the values of dose rate constants up to 3%.