Improving the buildup and depth-dose characteristics of high energy photon beams by using electron filters. Academic Article uri icon

Overview

abstract

  • The attributes of high energy photon beams, i.e., low surface dose, large dmax and improved %DD, are compromised with increase in field size. This is due to the relative increase with field size of the electron component in the beam, as shown by recent experiments done here using a sweeeping magnet. The present study shows that the advantages can be partially regained with the use of foils to remove electrons. Various thicknesses of Al, Cu, Sn, and Pb were placed in a 25-MV linac x-ray beam at several sites in the treatment head. Buildup curves were measured with a "pancake" chamber for various SSD and field sizes. The magnitude of improvement achieved is dependent upon field size, SSD, the atomic number of the foil material, and foil thickness. Pb foil (0.55 gcm-2) provided the best overall improvement. Surface dose reduction of 10%-20% can be achieved along with significant increase in dmax and %DD. These findings suggest a new design feature for the next generation of high energy linacs.

publication date

  • July 1, 1979

Research

keywords

  • Electrons
  • Elementary Particles
  • Radiotherapy Dosage
  • Radiotherapy, High-Energy

Identity

Scopus Document Identifier

  • 0018758746

PubMed ID

  • 113657

Additional Document Info

volume

  • 6

issue

  • 4