Beam's eye view
Encyclopedia
Beam's Eye View is an imaging technique used in radiation therapy
Radiation therapy
Radiation therapy , radiation oncology, or radiotherapy , sometimes abbreviated to XRT or DXT, is the medical use of ionizing radiation, generally as part of cancer treatment to control malignant cells.Radiation therapy is commonly applied to the cancerous tumor because of its ability to control...

 for the quality assurance and planning of External Beam Radiation Therapy treatments. These are primarily used to ensure that the relative orientation of the patient and the treatment machine are correct. The BEV image will typically contain the images of the patient's anatomy and the beam modifiers (such as jaws or Multi-Leaf Collimators (or MLCs)).

Generation of Beam's Eye Views

  • Physical Construction:
    • BEV's can be generated by exposing a high energy film (similar to photographic film
      Photographic film
      Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film...

      ) or an Electronic Portal Imaging Device (EPID) with the treatment beam itself after it passes through the patient and any beam modifiers (such as blocks). Although this type of image is an excellent indication of the basic quality of the treatment plan, the quality of film images can be poor.
    • A BEV can be created using a radiation therapy simulator which mimics the treatment geometry (couch angle, gantry angle, etc.) using an X-ray
      X-ray
      X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...

       source instead of the higher energy treatment source. The jaws and blocks can be imaged on the same film as the patient's landmarks.
  • Artificial Reconstruction: The BEV can be created using a Digitally Reconstructed Radiograph (or DRR) that is created from a computed tomography (or CT) data set. This image would contain the same treatment plan information, but the patient image is reconstructed from the CT image data using a physics model.
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