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1.ICRU-35, ICRU Report 35: Radiation Dosimetry: Electron Beams with Energies Between 1 and 50 MeV (ICRU, Bethesda, MD, 1984).
2.P. Andreo, D. T. Burns, K. Hohlfeld, M. S. Huq, T. Kanai, F. Laitano, V. Smyth, and S. Vynckier, Absorbed Dose Determination in External Beam Radiotherapy: An International Code of Practice for Dosimetry Based on Standards of Absorbed Dose to Water (International Atomic Energy Agency, Vienna, Technical Report series No. 398, 2000).
3.P. R. Almond, P. J. Biggs, B. M. Coursey, W. F. Hanson, M. S. Huq, R. Nath, and D. W. Rogers, “AAPM’s TG-51 protocol for clinical reference dosimetry of high-energy photon and electron beams,” Med. Phys. 26(9), 18471870 (1999).
4.D. I. Thwaites, A. R. DuSautoy, T. Jordan, M. R. McEwen, A. Nisbet, A. E. Nahum, W. G. Pitchford, and I. P. E. M. Working Party, “The IPEM code of practice for electron dosimetry for radiotherapy beams of initial energy from 4 to 25 Mev based on an absorbed dose to water calibration,” Phys. Med. Biol. 48(18), 29292970 (2003).
5.DIN 6800-2 (2008), “Procedures of dosimetry with probe-type detectors for photon and electron radiation - Part 2: Ionization chamber dosimetry of high energy photon and electron radiation” (Normenausschuss Radiologie (NAR) im DIN, Deutsches Institut für Normung, Berlin, Germany, 2008).
6.H. Svensson and A. Brahme, “Fundamentals of electron beam dosimetry,” in Proceedings of the Symposium on Electron Beam Therapy, edited by F. C. H. Chu and J. S. Laughlin (Memorial Sloan-Kettering Cancer Center, New York, NY, 1981), p. 17.
7.D. Harder, “The effect of multiple electron scattering on ionization in gas-filled cavities,” Biophysik 5(2), 157164 (1968).
8.K. A. Johansson, L. O. Mattsson, L. Lindborg, and H. Svensson, “Absorbed-dose determination with ionization chambers in electron and photon beams having energies between 1 and 50 MeV,” in National and International Standardization of Radiation Dosimetry, IAEA Proceedings Series, Vienna (IAEA, Vienna, Austria, 1978), Vol. 2, pp. 243270.
9.A. Van der Plaetsen, J. Seuntjens, H. Thierens, and S. Vynckier, “Verification of absorbed doses determined with thimble and parallel-plate ionization chambers in clinical electron beams using ferrous sulphate dosimetry,” Med. Phys. 21(1), 3744 (1994).
10.L. L. W. Wang and D. W. O. Rogers, “Replacement correction factors for plane-parallel ion chambers in electron beams,” Med. Phys. 37(2), 461465 (2010).
11.K. Zink and J. Wulff, “Beam quality corrections for parallel-plate ion chambers in electron reference dosimetry,” Phys. Med. Biol. 57(7), 18311854 (2012).
12.IAEA, The Use of Plane Parallel Ionization Chambers in High Energy Electron and Photon Beams: An International Code of Practice for Dosimetry, IAEA technical report series 381 (International Atomic Energy Agency, Vienna, Technical Report 1997).
13.M. Roos, K. Derikum, and A. Kraus, “Deviation of the effective point of measurement of the markus chamber from the front surface of its air cavity in electron beams,” The Use of Plane Parallel Ionization Chambers in High Energy Electron and Photon Beams (IAEA, Vienna, Austria, Review of data and methods recommended in the international code of practice for dosimetry, IAEA TECDOC 1173, IAEA Technical Reports Series No. 381 2000).
14.K. Zink and J. Wulff, “Positioning of a plane-parallel ionization chamber in clinical electron beams and the impact on perturbation factors,” Phys. Med. Biol. 54(8), 24212435 (2009).
15.K. Zink and J. Wulff, “On the wall perturbation correction for a parallel-plate NACP-02 chamber in clinical electron beams,” Med. Phys. 38(2), 10451054 (2011).
16.I. Kawrakow, “Accurate condensed history Monte Carlo simulation of electron transport. II. Application to ion chamber response simulations,” Med. Phys. 27(3), 499513 (2000).
17.I. Kawrakow, E. Mainegra-Hing, D. W. O. Rogers, F. Tessier, and B. R. B. Walters, “The EGSnrc code system: Monte Carlo simulation of electron and photon transport” (National Research Council of Canada, Ottawa, Canada, Report PIRS-701 2013).
18.J. Wulff, K. Zink, and I. Kawrakow, “Efficiency improvements for ion chamber calculations in high energy photon beams,” Med. Phys. 35(4), 13281336 (2008).
19.I. Kawrakow, E. Mainegra-Hing, F. Tessier, and B. R. B. Walter, “The EGSnrc c++ class library” (NRC Report PIRS-898 (Rev. A), Ottawa, Canada, 2009).
20.L. L. W. Wang and D. W. O. Rogers, “Calculation of the replacement correction factors for ion chambers im megavoltage beams by Monte Carlo simulation,” Med. Phys. 35(5), 17471755 (2008).
21.G. X. Ding, D. W. O. Rogers, and T. R. Mackie, “Calculation of stopping-power ratios using realistic clinical electron beams,” Med. Phys. 22(5), 489501 (1995).
22.L. L. W. Wang and D. W. O. Rogers, “Replacement correction factors for cylindrical ion chambers in electron beams,” Med. Phys. 36(10), 46004608 (2009).
23.H. K. Looe, D. Harder, and B. Poppe, “Experimental determination of the effective point of measurement for various detectors used in photon and electron beam dosimetry,” Phys. Med. Biol. 56(14), 42674290 (2011).
24.W. U. Laub, T. W. Kaulich, and F. Nüsslin, “A diamond detector in the dosimetry of high-energy electron and photon beams,” Phys. Med. Biol. 44(9), 21832192 (1999).
25.M. Lauterbach, “The multiple scattering of high-energy electrons into gas-filled cavities (in German),” Ph.D. thesis, University of Göttingen, 1999.
26.L. Eyges, “Multiple scattering with energy loss,” Phys. Rev. 74, 15341535 (1948).

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The electron fluence inside a parallel-plate ionization chamber positioned in a water phantom and exposed to a clinical electron beam deviates from the unperturbed fluence in water in absence of the chamber. One reason for the fluence perturbation is the well-known “inscattering effect,” whose physical cause is the lack of electron scattering in the gas-filled cavity. Correction factors determined to correct for this effect have long been recommended. However, more recent Monte Carlo calculations have led to some doubt about the range of validity of these corrections. Therefore, the aim of the present study is to reanalyze the development of the fluence perturbation with depth and to review the function of the guard rings.

Spatially resolved Monte Carlo simulations of the dose profiles within gas-filled cavities with various radii in clinical electron beams have been performed in order to determine the radial variation of the fluence perturbation in a coin-shaped cavity, to study the influences of the radius of the collecting electrode and of the width of the guard ring upon the indicated value of the ionization chamber formed by the cavity, and to investigate the development of the perturbation as a function of the depth in an electron-irradiated phantom. The simulations were performed for a primary electron energy of 6 MeV.

The Monte Carlo simulations clearly demonstrated a surprisingly large in- and outward electron transport across the lateral cavity boundary. This results in a strong influence of the depth-dependent development of the electron field in the surrounding medium upon the chamber reading. In the buildup region of the depth-dose curve, the in–out balance of the electron fluence is positive and shows the well-known dose oscillation near the cavity/water boundary. At the depth of the dose maximum the in–out balance is equilibrated, and in the falling part of the depth-dose curve it is negative, as shown here the first time. The influences of both the collecting electrode radius and the width of the guard ring are reflecting the deep radial penetration of the electron transport processes into the gas-filled cavities and the need for appropriate corrections of the chamber reading. New values for these corrections have been established in two forms, one converting the indicated value into the absorbed dose to water in the front plane of the chamber, the other converting it into the absorbed dose to water at the depth of the effective point of measurement of the chamber. In the Appendix, the in–out imbalance of electron transport across the lateral cavity boundary is demonstrated in the approximation of classical small-angle multiple scattering theory.

The in–out electron transport imbalance at the lateral boundaries of parallel-plate chambers in electron beams has been studied with Monte Carlo simulation over a range of depth in water, and new correction factors, covering all depths and implementing the effective point of measurement concept, have been developed.


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