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  4. The Effects of High-Z Heterogeneities On the Dose Deposition of Energetic Electron Beam Therapy

The Effects of High-Z Heterogeneities On the Dose Deposition of Energetic Electron Beam Therapy

I Ali1*, N Alsbou2 , S Ahmad1 , (1) University of Oklahoma Health Sciences, Oklahoma City, OK, (2) Department of Engineering and Physics, University of Central Oklahoma, Edmond, OK,

Presentations

(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: To investigate quantitatively scattering and dose deposition effects of high energy electron beams on high-z heterogeneities and the dosimetric uncertainties that are not accounted for by the dose calculation algorithms in electron therapy.

Methods: Electron dose distributions were measured with a multiple-diode-array detector (MapCheck2) using different beam energies ranging from 6-20MeV. These electron beams were used to irradiate different phantoms with high-z heterogeneities including the Leeds phantom which was placed at different depths ranging from 0-4cm under solid water phantom. The different objects well-known in the Leeds phantom were used to investigate quantitatively the dose deposition and scatter of the electron beam. The dose from the interaction of energetic electrons with high-z heterogeneities were investigated quantitatively both by measurement and modeling.

Results: The measured dose distributions from the different electron beams showed strong interference patterns that depended on beam energy, density and depth of heterogeneity in phantom. The dose deposition in medium by energetic electron varied by 12% between the peaks and valleys of the dose interference patterns. The constructive and destructive interference patterns of the dose deposition were explained by considering the quantum effect associated with wave nature of the energetic electrons. Considering the primary beam as a plane wave that interfere with a spherical wave for the scattered electrons on the different objects predicts well the structures of the interference patterns and their dependence on the different physical parameters.

Conclusion: The wave nature of high energy electron beams and the density medium affected the dose distributions in electron therapy. The dose distributions showed patterns with high and low dose regions from constructive and destructive interferences. These dose deposition interference regions are not accounted in available dose calculation algorithms used in electron therapy which induces large dosimetric uncertainties for local regions in the tumor that includes high-z heterogeneities.

Keywords

Electron Therapy, Dosimetry

Taxonomy

Not Applicable / None Entered.

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