PMID: 16532940Mar 15, 2006Paper

Reconstruction of electron spectra from depth doses with adaptive regularization

Medical Physics
Jikun WeiAlexei V Chvetsov

Abstract

Electron spectral reconstruction of medical accelerators from measured depth doses is a practical method for providing the input initial phase space distribution at the patient surface that is required by Monte Carlo treatment planning systems. The posed inverse problem of spectral reconstruction is ill conditioned and this may lead to nonphysical oscillations in the reconstructed spectra. Use of a variational method of solution with a regularization technique removes the oscillations but tends to smooth the sharp (deltalike) energy peak that is a common feature in electron spectra generated by medical accelerators. Because the sharp peak contains a large percentage of the electrons in the spectrum, an accurate estimate of the peak width, height and position is critical to the success of the technique for spectrum reconstruction with regularization. We propose use of an adaptive regularization term as a special form of the general Tichonov regularization function. The variational method with the adaptive regularization term is applied to reconstruct electron spectra for the 6, 9, and 18 MeV electron beams of a Varian Clinac 2100C accelerator and proves to be a very simple, effective and accurate approach. Results using this var...Continue Reading

References

May 1, 1995·Medical Physics·D W RogersT R Mackie
May 1, 1996·Medical Physics·J O DeasyM T McEllistrem
Apr 11, 2000·Medical Physics·B A Faddegon, I Blevis
Mar 7, 2001·Physics in Medicine and Biology·J J JanssenH Huizenga
May 7, 2002·Medical Physics·Alexei V Chvetsov, George A Sandison
Aug 30, 2003·Medical Physics·Alexei V Chvetsov, George A Sandison

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Citations

Dec 28, 2007·Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology·Jose M de la VegaAntonio M Lallena
Oct 21, 2015·Physics in Medicine and Biology·Alevei V ChvetsovRamesh Rengan

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