Medical Radiology and Radiation Safety. 2017. Vol. 62. No. 5. P. 47-51

RADIATION PHYSICS, TECHNOLOGY AND DOSIMETRY

DOI: 10.12737/article_59f300494670a7.65219672

Reconstruction of Bremsstrahlung Spectrum of Medical Electron Linear Accelerators from Deep Dose Distributions in Water Phantom

V.A. Klimanov^1,2, J.J. Galjautdinova¹, N.N. Mogilenets², V.V. Smirnov²

1. A.I. Burnasyan Federal Medical Biophysical Center of the FMBA of Russia, Moscow, Russia, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it. ; 2. National Research Nuclear University MEPhI, Moscow, Russia

V.A. Klimanov – Leading Researcher, Dr. Sc. Phys.-Math., Prof., Member of AAPM; J.J. Galjautdinova – Head of Lab.; N.N. Mogilenets – Senior Lecturer; V.V. Smirnov – Leading Researcher, PhD Phys.-Math., Associated Prof.

Abstract

Purpose: Development of the bremsstrahlung spectrum reconstruction method of medical electron linear accelerators (ELA) with different field sizes, on the base of the deep dose distributions in a water phantom and determination of photon spectra for Varian Trilogy accelerator 6 MV.

Material and methods: The proposed methodology is based on the use of dose kernels algorithm of point monoenergetic monodirectional source (pencil beam (PB)) for the deep dose distribution calculation, created different cross-section beams in a water phantom, and experimental measurements of these distributions. For solving the inverse problem is applied Toolbox routines ‘ptimtool knowing mathematical package MATLAB to solve.

Results: Bremsstrahlung energy spectrum generated medical accelerator Varian Triology with different sizes of square fields from 3×3 up to 40×40 cm and average energy photons, depending on the size of the fields were received. Dose kernels for a set of defined energies PB were calculated. Depth dose distribution in a water phantom, calculated using the obtained spectra and dose kernels agree well with measurement dose distributions.

Conclusion: The proposed technique reconstruction of bremsstrahlung spectrum of electron linear accelerator is adequate. Average energy spectra of bremsstrahlung photons for Varian Trilogy Accelerator in regime 6 MV varies from 1.71 to 1.43 MeV depending on the field size.

Key words: radiation therapy, medical accelerators, bremsstrahlung, deep dose distributions, reconstruction of the photon spectrums

REFERENCES

1. Mohan R., Chui C., Lidofsky L. Energy and angular distributions of photons from medical linear accelerators. Med. Phys. 1985. Vol. 12. P. 592–597.
2. Ahnesjo A., Saxner M., Trepp A. A pencil beam model for photon dose calculation. Med. Phys. 1992. Vol. 19. No. 2. P. 263–273.
3. Ulmer W., Harder D. Application of a triple Gaussian photon pencil beam model for photon beam treatment planning. Z. Med. Phys. 1995. Vol. 5. P. 25–30.
4. Sheikh-Bagheria D., Rogers D. W. O. Monte Carlo calculation of nine megavoltage photon beam spectra using the BEAM code. Med. Phys. 2002. Vol. 29. No. 3. P. 391–402.
5. Ahnesjo A., Andreo P. Determination of effective bremsstrahlung spectra and electron contamination for photon dose calculations. Phys. Med. Biol. 1989. Vol. 34. No. 10. P. 1451–1464.
6. Rrimar M., Nicolic D., Krstonosic P. A simple method for bremsstrahlung spectra reconstruction from transmission measurements. Med. Phys. 2002. Vol. 29. No. 6. P. 932–938.
7. Klimanov V.A., Smirnov V.V., Jyrov V.U., Semenov U.V. Reconstrukciya effectivnogo spectra tormoznogo izluchenia po prostranstvennyim dozoviym profilyam I glubinnomu dozovomu raspredeleniu. Med. fisika. 2011. 2(50). P. 23–30. (In Russ.).
8. Klimanov V.A., Moiseev A.N., Mogilenec N.N. Analiticheskaya approximaciya dozovogo yadra tonkogo lucha fotonov co spectrum terapevticheskogo apparata ROKUS. Med. fisika. 2015. 2(66). P. 7–15. (In Russ.).
9. Kawrakow I. Accurate condensed history Monte Carlo simulation of electron transport. I. EGSnrc, the new EGS4 version. Med. Phys. 2000. Vol. 27. P. 485–498.
10. Rogers D. W. O., Faddegon B. A., Ding G. X. et al. BEAM: A Monte Carlo code to simulate radiotherapy treatment units. Med. Phys. 1995. Vol. 22. P. 503–524.

For citation: Klimanov VA, Galjautdinova JJ, Mogilenets NN, Smirnov VV. Reconstruction of Bremsstrahlung Spectrum of Medical Electron Linear Accelerators from Deep Dose Distributions in Water Phantom. Medical Radiology and Radiation Safety. 2017;62(5):47-51. Russian. DOI: 10.12737/article_59f300494670a7.65219672

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