PROCEEDINGS OF THE 7 INTERNATIONAL ... - Fizika

More documents

Recommendations

Info

Y. Dekhtyar et al. / Medical Physics in the Baltic States 7 (2009) 69 - 71 vinyltriethoxysilane containing copolymers, Department of Chemistry, Faculty of Art and Science, Gazi University, Hacettepe University, Ankara, Turkey, 1999. p. 225-229. 6. Lican Lu, Nianfa Yang, Yuanli Cai, Wellcontrolled reversible addition–fragmentation chain transfer radical polymerisation under ultraviolet radiation at ambient temperature. College of Chemistry, Xiangtan University, Xiangtan, Hunan, China, 2005. p. 5287-5288. 7. Kaariainen T.O., Cameron D.C., Improving the adhesion of sputtered coatings on PMMA using 71 ALD interlayers, Advanced Surface Technology Research laboratory, Lapeenrata University of Technology, Mikkeli, Finland, 23, 2009. 8. Akmene R.J., Balodis,A. Dekhtyar J.D., Markelova G.N., Matvejev J.V., Polyaka N., Rozenfeld L.B., Sagalovich G.L., Samrnov J.S., Tolkaaov A.A., Upmiņsh A.I. Exoelectron emission specrometer complete set of surface local investigation. Surface. Physics, mechanics, chemistry. N 8, 1993. p. 125 - 128.
MEDICAL PHYSICS IN <strong>THE</strong> BALTIC STATES 7 (2009) Proceedings of International Conference “Medical Physics 2009” 8 - 10 October 2009, Kaunas, Lithuania TOTAL AND SCATTER DOSE MODELLING IN PHOTON IRRADIATED Si SAMPLES, COVERED BY PROTECTIVE COATINGS Inga CIBULSKAITĖ*, Diana ADLIENĖ* *Kaunas University of Technology Abstract: Total and scatter doses due 25-32 keV X-ray beam irradiation of Si samples, covered by different materials protective coatings, calculated by Monte Carlo based modelling code EGSnrc are presented in this paper. Keywords: dose, scatter, modelling, Monte Carlo 1. Introduction Through low energy (25-32) keV X-ray photon interactions (the photoelectric effect, the Compton effect) with material, the photon radiation transfers energy to it. This transfer is considered as a dose. The energy transport during the X-ray photons interaction with different materials, that are used for radiation registration, processes could be analysed in detail experimentally or by modelling. In constructions of up-to-date detectors new perspective composite materials (crystal, polycrystalline) are used, the active volume of the most detectors is protected by protective coating (polymers, amorphous materials), defending it from mechanical, aggressive atmospheric and ionising radiation damage. It is difficult to test each construction practically, so the results obtained by mathematical modelling of the photon interaction process could be used for this purposes. and after this, by choosing the most perspective constructions – examine their characteristic practically. The scattered radiation, that is due to X-ray interaction with material, could reach the active volume again and that negatively influence on the registration of the useful signal. By varying detector‘s geometry, construction and materials composition according to selected criterion it is possible to find the optimal version for detector with less influence of scatter to the signal recorded by detector. The selection of such criterion let us prognosticate new constructions, to compare its characteristic to characteristics of detectors used in praxis. As the criterion for the scatter process estimation in radiation sensitive material could be calculated according to lower scatter dose to total dose ratio. By application of this criterion it is possible to compare indirectly the efficiency of the registration of all configurations detectors also those that are under construction. 72 Si is one of the materials sensitive to ionising radiation and applied in many solid state detectors. Not considering the detective properties of this material, the calculation of the total and scatter dose by Monte Carlo based code in Si samples, was done to investigate the influence of the different protective coatings applied to Si samples, for the doses results. 2. Instruments and methods Interactions of low energy (25-32) keV polyenergetic X-ray photons with matter were simulated using simulation code based on Monte Carlo method (EGSnrc Code system) [1] Investigation of interaction effects in Si samples was performed using adapted the real exposure conditions, representing mammography examinations of patients. Assuming that Si sample without and with coating was placed at a central position on the top of 45 mm polymethylmethacrylate PMMA phantom, representing “standard” compressed female breast that was used instead of patient for the simulation of the real irradiation conditions, Monte Carlo simulations were performed within cylindrical geometry, virtually dividing the X-ray exposed space between compression paddle and breast support table into zones, corresponding to the different densities and compositions of presented materials. Individual photon histories were simulated and the history of each photon was followed until either all of its energy was transferred to electrons or it was absorbed locally due to the scattering events in material. It was assumed that 10 8 or 10 9 photons having in 1 keV increments increasing energy from the range of 1 keV to 35 keV interact with samples. Considering small sample size (mm range) as compared to exposure area (12 x 18) cm, it was assumed that X-ray photons beam is parallel to Z-axis in the central zone of interaction and there was no X-ray beam distortion. Total and scattering doses in uncoated and coated samples were calculated using modified user code
Page 1 and 2:
2009 PROCEEDINGS OF THE 7 th INTERN
Page 3 and 4:
Executive editor: D.Adlienė CONFER
Page 5 and 6:
11.15-11.30 Daiva Leščiute, Valda
Page 7 and 8:
MEDICAL PHYSICS IN THE BALTIC STATE
Page 9 and 10:
S. Mattsson / Medical Physics in th
Page 11 and 12:
S. Mattsson / Medical Physics in th
Page 13 and 14:
L. Bumbure et al. / Medical Physics
Page 15 and 16:
Average brightness Brightness range
Page 17 and 18:
Page 19 and 20:
D. Lesciute et al. / Medical Physic
Page 21 and 22: MEDICAL PHYSICS IN THE BALTIC STATE
Page 23 and 24: D. Kaskelyte et al. / Medical Physi
Page 27 and 28: V. Poderys et al. / Medical Physics
Page 29 and 30: E D A B C V. Poderys et al. / Medic
Page 33 and 34: A. Kulbickas / Medical Physics in t
Page 37 and 38: M. Franckevicius / Medical Physics
Page 39 and 40: M. Franckevicius / Medical Physics
Page 41 and 42: J. Puiso et al. / Medical Physics i
Page 43 and 44: J. Puiso et al. / Medical Physics i
Page 45 and 46: T. Landberg et al. / Medical Physic
Page 55 and 56: S. Plaude et al. / Medical Physics
Page 59 and 60: Table 1. Optimization of number of
Page 63 and 64: C.-M. Nilsson / Medical Physics in
Page 67 and 68: S. Bernhardsson et al. / Medical Ph
Page 69 and 70: S. Bernhardsson et al. / Medical Ph
Page 71: 2.3. Biological test. Y. Dekhtyar e
Page 75 and 76: Scatter dose ( Gy /mA s) 1.55E-12 1
Page 79 and 80: N. Kazuchits et al. / Medical Physi
Page 81 and 82: V. Minialga et al. / Medical Physic
Page 83 and 84: Temperature, o C 36 35 34 33 32 31
Page 85 and 86: O. Klepalov et al. / Medical Physic
Page 89 and 90: G. Adlys / Medical Physics in the B
Page 91 and 92: G. Adlys / Medical Physics in the B
Page 93 and 94: D. Mikšys / Medical Physics in the
Page 95 and 96: L. Krynke et al.. / Medical Physics
Page 99 and 100: M. Pučetaitė et al. / Medical Phy
Page 105 and 106: D. Bernatavičius et al. / Medical
Page 109 and 110: N. Vaiciunaite / Medical Physics in
Page 111 and 112: D. Adlienė et al. / Medical Physic
Page 113 and 114: MP Competences Generic Competences
Page 117 and 118: S. Tabakov et al. / Medical Physics
Page 119 and 120: J. Laurikaitienė et al. / Medical
Page 121 and 122: R, % 100,0 99,5 99,0 98,5 98,0 97,5
Page 123 and 124:
S. Mockevičienė et al. / Medical
Page 125 and 126:
show all

PROCEEDINGS OF THE 7 INTERNATIONAL ... - Fizika

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?