Thimble ionization chambers in medium-energy x-ray beams and the role of constructive details of the central electrode: Monte Carlo simulations and measurements

Physics in Medicine and Biology
F UbrichK Zink

Abstract

This paper presents investigations of thimble ionization chamber response in medium-energy kilovoltage x-ray beams (70-280 kVp, 0.09-3.40 mm Cu HVL). Two thimble ionization chambers (PTW30015 and PTW30016) were investigated, regarding the influence of the central electrode dimensions made of aluminum. Measurements were carried out in photon fields of different beam quality. Corresponding Monte Carlo simulations employing the EGSnrc Monte Carlo code system were performed. The simulations included the modelling of the x-ray tube and measurement setup for generation of x-ray spectra. These spectra were subsequently used to calculate the absorbed energy in the air cavity of the two thimble ionization chamber models and the air kerma at the reference point of the chambers. Measurements and simulations revealed an optimal diameter of the central electrode, concerning an almost energy-independent response of the ionizaton chamber. The Monte Carlo simulations are in good agreement with the measured values, expressed in beam quality correction factors k(Q). The agreement was generally within 0.6% but could only be achieved with an accurate model of the central electrode including its exact shape. Otherwise, deviations up to 8.5% resulte...Continue Reading

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Citations

Sep 12, 2013·Zeitschrift für medizinische Physik·Frank UbrichKlemens Zink
Jun 30, 2015·Zeitschrift für medizinische Physik·Petar PenchevKlemens Zink
Dec 24, 2016·Journal of Synchrotron Radiation·Andrew W StevensonJessica E Lye
May 16, 2018·Physics in Medicine and Biology·Stefan PojtingerDaniela Thorwarth
Mar 4, 2014·Physics in Medicine and Biology·Robin HillClive Baldock
Dec 3, 2015·Physics in Medicine and Biology·Pedro AndreoÅsa Carlsson-Tedgren
Dec 10, 2020·Sensors·Alexey BuzmakovIgor Schelokov

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