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Related Experiment Videos

Head-scatter factors in blocked photon fields

M Tatcher1, B E Bjärngard

  • 1Roger Williams Cancer Centre, Brown University, Providence, RI 02908.

Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology
|October 1, 1994
PubMed
Summary
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Shielding blocks in linear accelerator X-ray beams cause minimal head-scatter changes (<1%) in unwedged beams. Wedges slightly decrease head-scatter, with negligible contributions from trays and blocks.

Area of Science:

  • Medical Physics
  • Radiation Oncology

Background:

  • Accurate dosimetry in radiation therapy relies on understanding scatter factors.
  • Shielding blocks are used to shape radiation fields, potentially affecting scatter.

Purpose of the Study:

  • To quantify the head-scatter factor in shielded X-ray beams.
  • To investigate the impact of shielding blocks and wedges on head-scatter.

Main Methods:

  • Measured incident fluences using direct (in-air) and indirect (in-phantom) methods.
  • Utilized 6 and 25 MV X-ray beams from a Philips SL25 linear accelerator.
  • Investigated slit-shaped fields defined by shielding blocks.

Main Results:

  • Head-scatter perturbations were less than 1% in unwedged beams, even with 80% field shielding.

Related Experiment Videos

  • Results were independent of beam energy and slit orientation.
  • Wedges decreased head-scatter by a few percent, dependent on slit direction but not energy.
  • Contributions from block trays and shielding blocks were negligible.

    • Conclusions:

    • Shielding blocks have a minimal impact on head-scatter factors in linear accelerator beams.
    • Wedge insertion affects head-scatter, but this effect is energy-independent.
    • The findings are crucial for precise radiation dose calculations.