Harvesting backscatter electrons for radiation therapy

Indra J. Das, Lawrence R. Coia, Tatsuo Tabata

Research output: Contribution to journalArticle

5 Scopus citations


Purpose: An innovative technique is used to harvest backscatter electrons for the treatment of superficial small lesions of skin, oral cavity, and rectum where a significant dose gradient and maximum surface dose is desired. Methods and materials: Backscatter electrons are harvested out of the primary electron beams from the linear accelerators. The design consists of a short cylindrical cone that fits snugly over a long cylindrical electron cone. The shore cylindrical cone has a thick circular palte of high atomic number medium (Pb) attached to the distal end, and a lateral slit of variable length and width. The width of the slit could be closed as desired by rotating the two cones and the length can be increased by lowering the short cylindrical cone. Primary electrons strike the Pb plate perpendicularly and produce backscatter electrons that pass through the laterla slit for treatment. Using film and a parallel palte ion chamber, backscattered electron dose characteristics are studied. Results: Teh depth dose characteristics of the backscatter electron is very similar to that of the 0.2 mm Al half-value layer x-ray beam that is commonly used for the intracavitary and superficial lesions. The backscatter electron energy is nearly constant and effectively ≤ 1 MeV from the clinical megavoltage beams. The backscatter electron dose rate of 0.32-0.8 Gy/min could be achieved frommodern accelerators without any modification. The beam flatness is dependent on the slit size and the depth of treatment, but is satisfactory to treat small lesions. Conclusion: The measured data for backscatter electron energy, fluence, depth dose, flatness, dose rate, and absolute dose indicates that the harvested backscaterred electrons are suitable for clinical use.

Original languageEnglish (US)
Pages (from-to)695-703
Number of pages9
JournalInternational journal of radiation oncology, biology, physics
Issue number3
StatePublished - Oct 15 1995


  • Electron backscattering
  • Electron cone
  • High Z interface
  • Intracavitary treatment
  • Superficial treatment

ASJC Scopus subject areas

  • Radiation
  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Cancer Research

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