The experimental measurements of the effects of field size and shadow tray on the relative surface doses for C0-60 and 10 MV X-ray beams

1981 ◽  
Vol 17 (3) ◽  
pp. 555
Author(s):  
I W Choo ◽  
C I Park ◽  
M C Han
Keyword(s):  
Field Size ◽  
Experimental Measurements ◽  
X Ray

scholarly journals Photoconductivity of the Single Crystals Pb4Ga4GeS12 and Pb4Ga4GeSe12

Proceedings ◽  
2020 ◽  
Vol 62 (1) ◽  
pp. 4
Author(s):  
Hadj Bellagra ◽  
Oksana Nyhmatullina ◽  
Yuri Kogut ◽  
Halyna Myronchuk ◽  
Lyudmyla Piskach
Keyword(s):  
Ternary Systems ◽  
Semiconductor Materials ◽  
Tetragonal Symmetry ◽  
Bandgap Energy ◽  
Experimental Measurements ◽  
X Ray Diffraction ◽  
X Ray ◽  
Vertical Bridgman ◽  
Symmetry Space ◽  
Symmetry Space Group

Quaternary semiconductor materials of the Pb4Ga4GeS(Se)12 composition have attracted the attention of researchers due to their possible use as active elements of optoelectronics and nonlinear optics. The Pb4Ga4GeS(Se)12 phases belong to the solid solution ranges of the Pb3Ga2GeS(Se)8 compounds which form in the quasi-ternary systems PbS(Se)−Ga2S(Se)3−GeS(Se)2 at the cross of the PbGa2S(Se)4−Pb2GeS(Se)4 and PbS(Se)−PbGa2GeS(Se)6 sections. The quaternary sulfide melts congruently at 943 K. The crystallization of the Pb4Ga4GeSe12 phase is associated with the ternary peritectic process Lp + PbSe ↔ PbGa2S4 + Pb3Ga2GeSe8 at 868 K. For the single crystal studies, Pb4Ga4GeS(Se)12 were pre-synthesized by co-melting high-purity elements. The X-ray diffraction results confirm that these compounds possess non-centrosymmetric crystal structure (tetragonal symmetry, space group P–421c). The crystals were grown by the vertical Bridgman method in a two-zone furnace. The starting composition was stoichiometric for Pb4Ga4GeS12, and the solution-melt method was used for the selenide Pb4Ga4GeSe12. The obtained value of the bandgap energy for the Pb4Ga4GeS12 and Pb4Ga4GeSe12 crystals is 1.86 and 2.28 eV, respectively. Experimental measurements of the spectral distribution of photoconductivity for the Pb4Ga4GeS12 and Pb4Ga4GeSe12 crystals exhibit the presence of two spectral maxima. The first lies in the region of 570 (2.17 eV) and 680 nm (1.82 eV), respectively, and matches the optical bandgap estimates well. The locations of the admixture maxima at about 1030 (1.20 eV) and 1340 nm (0.92 eV), respectively, agree satisfactorily with the calculated energy positions of the defects vs. and VSe.

scholarly journals Estimation of dose and cancer risk to newborn from chest X-ray in South-South Nigeria: a call for protocol optimization

2021 ◽  
Vol 52 (1) ◽  
Author(s):  
Akintayo Daniel Omojola ◽  
Michael Onoriode Akpochafor ◽  
Samuel Olaolu Adeneye ◽  
Isiaka Olusola Akala ◽  
Azuka Anthonio Agboje
Keyword(s):  
Cancer Risk ◽  
Age Groups ◽  
Field Size ◽  
Radiological Protection ◽  
International Studies ◽  
X Ray ◽  
Thermoluminescent Dosimeters ◽  
Chest X Ray ◽  
Neonatal Patient ◽  
The Mean

Abstract Background The use of X-ray as a diagnostic tool for complication and anomaly in the neonatal patient has been helpful, but the effect of radiation on newborn stands to increase their cancer risk. This study aims to determine the mean, 50th percentile (quartile 2 (Q2)), and 75th percentile (quartile 3 (Q3)) entrance surface dose (ESD) from anteroposterior (AP) chest X-ray and to compare our findings with other relevant studies. The study used calibrated thermoluminescent dosimeters (TLDs), which was positioned on the central axis of the patient. The encapsulated TLD chips were held to the patients’ body using paper tape. The mean kilovoltage peak (kVp) and milliampere seconds (mAs) used was 56.63(52–60) and 5.7 (5–6.3). The mean background TLD counts were subtracted from the exposed TLD counts and a calibration factor was applied to determine ESD. Results The mean ESDs of the newborn between 1 and 7, 8 and 14, 15 and 21, and 22 and 28 days were 1.09 ± 0.43, 1.15 ± 0.50, 1.19 ± 0.45, and 1.32 ± 0.47 mGy respectively. A one-way ANOVA test shows that there were no differences in the mean doses for the 4 age groups (P = 0.597). The 50th percentile for the 4 age groups was 1.07, 1.26, 1.09, and 1.29 mGy respectively, and 75th percentile were 1.41, 1.55, 1.55, and 1.69 mGy respectively. The mean effective dose (ED) in this study was 0.74 mSv, and the estimated cancer risk was 20.7 × 10−6. Conclusion ESD was primarily affected by the film-focus distance (FFD) and the patient field size. The ESD at 75th percentile and ED in this study was higher compared to other national and international studies. The estimated cancer risk to a newborn was below the International Commission on Radiological Protection (ICRP) limit for fatal childhood cancer (2.8 × 10−2Sv−1).

scholarly journals Advanced Small Animal Conformal Radiation Therapy Device

2016 ◽  
Vol 16 (1) ◽  
pp. 45-56 ◽  
Author(s):  
Sunil Sharma ◽  
Ganesh Narayanasamy ◽  
Beata Przybyla ◽  
Jessica Webber ◽  
Marjan Boerma ◽  
...  
Keyword(s):  
Radiation Therapy ◽  
Small Animal ◽  
Therapeutic Benefit ◽  
Integrated System ◽  
Field Size ◽  
National Council ◽  
Conformal Radiation Therapy ◽  
X Ray ◽  
Custom Made

We have developed a small animal conformal radiation therapy device that provides a degree of geometrical/anatomical targeting comparable to what is achievable in a commercial animal irradiator. small animal conformal radiation therapy device is capable of producing precise and accurate conformal delivery of radiation to target as well as for imaging small animals. The small animal conformal radiation therapy device uses an X-ray tube, a robotic animal position system, and a digital imager. The system is in a steel enclosure with adequate lead shielding following National Council on Radiation Protection and Measurements 49 guidelines and verified with Geiger-Mueller survey meter. The X-ray source is calibrated following AAPM TG-61 specifications and mounted at 101.6 cm from the floor, which is a primary barrier. The X-ray tube is mounted on a custom-made “gantry” and has a special collimating assembly system that allows field size between 0.5 mm and 20 cm at isocenter. Three-dimensional imaging can be performed to aid target localization using the same X-ray source at custom settings and an in-house reconstruction software. The small animal conformal radiation therapy device thus provides an excellent integrated system to promote translational research in radiation oncology in an academic laboratory. The purpose of this article is to review shielding and dosimetric measurement and highlight a few successful studies that have been performed to date with our system. In addition, an example of new data from an in vivo rat model of breast cancer is presented in which spatially fractionated radiation alone and in combination with thermal ablation was applied and the therapeutic benefit examined.

scholarly journals Fiber Formation during Melt Blowing

2003 ◽  
Vol os-12 (2) ◽  
pp. 1558925003os-12 ◽  
Author(s):  
Randall R. Bresee ◽  
Wen-Chien Ko
Keyword(s):  
Fiber Diameter ◽  
Fiber Formation ◽  
Experimental Measurements ◽  
Wide Angle ◽  
X Ray Diffraction ◽  
Air Velocity ◽  
Melt Blowing ◽  
X Ray ◽  
X Ray Scattering ◽  
Insight Into

Experimental measurements are presented to provide phenomenological insight into the commercial melt blowing process. In particular, we discuss the following experimental measurements obtained at various die-collector locations: fiber diameter, fiber velocity, air velocity, fiber acceleration, fiber entanglement, fiber temperature, birefringence, wide-angle x-ray diffraction and small-angle x-ray scattering. Our discussion focuses on how these measurements provide insight into fiber formation during melt blowing.

Phase Transformation Studies in Silver and Thallium Chromates

1974 ◽  
Vol 52 (5) ◽  
pp. 712-717 ◽  
Author(s):  
Mahadeva Natarajan ◽  
Etalo A. Secco
Keyword(s):  
Thermal Analysis ◽  
Lattice Distortion ◽  
Experimental Measurements ◽  
Temperature Structure ◽  
Conductivity Measurements ◽  
Thermal Transformations ◽  
X Ray Diffraction ◽  
Subtle Difference ◽  
X Ray ◽  
Temperature Variable

The existence of thermal transformations in silver and thallium chromate has been confirmed by differential thermal analysis, temperature-variable X-ray diffraction, and electrical conductivity measurements. The disputed transition ∼330 °C in Tl2CrO4 has been shown to be due to lattice distortion. The subtle difference in behavior of the pre-annealed and un-sintered samples is brought out by a variety of experimental measurements. The high temperature structure of these chromates is hexagonal. The presence of small amounts of Tl in Ag2CrO4 affects the transition temperature, enthalpy, and the order of the transformation.

Conversion Factors between Energy Imparted to the Patient and Air Collision Kerma Integrated over Beam Area in Pediatric Radiology

1993 ◽  
Vol 34 (1) ◽  
pp. 92-98 ◽  
Author(s):  
J. Persliden ◽  
M. Sandborg
Keyword(s):  
Monte Carlo ◽  
Soft Tissue ◽  
Conversion Factor ◽  
Field Size ◽  
Conversion Factors ◽  
X Ray ◽  
Monte Carlo Calculations ◽  
Tissue Phantoms ◽  
Tube Potential ◽  
Pediatric Radiography

Conversion factors between the energy imparted to the patient in pediatric radiography and air collision kerma integrated over beam area are presented. The values have been derived from Monte Carlo calculations in soft tissue phantoms and extend results published earlier to cover children from early infancy to the age of 15 years. Variations related to phantom size as well as to focus-phantom distance, radiation field size, orientation of view (a.p., lateral), tube potential, and beam filtration are given. We show that the conversion factor increases with increasing half-value layer of the X-ray beam and the anterioposterior width of the simulated child. Increasing the focus-phantom distance increases the conversion factor, while increasing the field size decreases the factors due to more scattered radiation escaping laterally from the phantom.

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