Mixing intensity modulated electron and photon beams: combining a steep dose fall-off at depth with sharp and depth-independent penumbras and fiat beam profiles

EW Korevaar*, BJM Heijmen, E Woudstra, H Huizenga, A Brahme

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

20 Citations (Scopus)

Abstract

For application in radiotherapy, intensity modulated high-energy electron and photon beams were mixed to create dose distributions that feature: (a) a steep dose fall-off at larger depths, similar to pure electron beams, (b) hat beam profiles and sharp and depth-independent beam penumbras, as in photon beams, and (c) a selectable skin dose that is lower than for pure electron beams.

To determine the required electron and photon beam fluence profiles, an inverse treatment planning algorithm was used. Mixed beams were realized at a MM50 racetrack microtron (Scanditronix Medical AB, Sweden), and evaluated by the dose distributions measured in a water phantom. The multileaf collimator of the MM50 was used in a static mode to shape overlapping electron beam segments, and the dynamic multileaf collimation mode was used to realize the intensity modulated photon beam profiles.

Examples of mixed beams were generated at electron energies of up to 40 MeV. The intensity modulated electron beam component consists of two overlapping concentric fields with optimized field sizes, yielding broad, fairly depth-independent overall beam penumbras. The matched intensity modulated photon beam component has high fluence peaks at the field edges to sharpen this penumbra. The combination of the electron and the photon beams yields dose distributions with the characteristics (a)-(c) mentioned above.

Original languageEnglish
Pages (from-to)2171-2181
Number of pages11
JournalPhysics in Medicine and Biology
Volume44
Issue number9
DOIs
Publication statusPublished - Sep-1999
Externally publishedYes

Keywords

  • DYNAMIC MULTILEAF COLLIMATION
  • HIGH-ENERGY
  • NUMERICAL-CALCULATION
  • RADIATION-THERAPY
  • RACETRACK MICROTRON
  • OPTIMIZATION
  • DEPOSITION
  • ALGORITHM
  • FLUENCE
  • RADIOTHERAPY

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