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Radiotherapy is "the use of ionizing radiation to treat malignant neoplasms and some benign conditions."[1][2]


Radiotherapy can be classified by type of radiation, which includes:

  • Electromagnetic (photons)
  • Electrons. Electrons are used for superficial targets as the energy of electrons decreases during penetration of tissues
  • Protons. Initial research suggests that proton beams with conformal methods, can increase the accuracy of placement of the radiation. A randomized controlled trial of radiotherapy for prostate cancer found improved response of prostate specific antigen without increased local complications.[3] There is concern that particle accelerators for producing protons are proliferating in American health care prior to adequate study of the their role.[4]

Radiotherapy can be classified by the amount of energy associated with the radiation:

  • High-energy radiotherapy is "radiotherapy using high-energy (megavolt or higher) ionizing radiation. Types of radiation include gamma rays, produced by a radioisotope within a teletherapy unit; x-rays, electrons, protons, alpha particles (helium ions) and heavy charged ions, produced by particle acceleration; and neutrons and pi-mesons (pions), produced as secondary particles following bombardment of a target with a primary particle."[5]
  • Orthovoltage therapy is x-rays between 150 and 500 kV
  • Lower energy x-rays (50 to 150 kV) can be used for superficial therapy.

Radiotherapy can be classified by delivery methods:

  • External beam
  • Brachytherapy is "a collective term for interstitial, intracavity, and surface radiotherapy. It uses small sealed or partly-sealed sources that may be placed on or near the body surface or within a natural body cavity or implanted directly into the tissues."[6]
  • Radioimmunotherapy is "radiotherapy where cytotoxic radionuclides are linked to antibodies in order to deliver toxins directly to tumor targets. Therapy with targeted radiation rather than antibody-targeted toxins (immunotoxins) has the advantage that adjacent tumor cells, which lack the appropriate antigenic determinants, can be destroyed by radiation cross-fire. Radioimmunotherapy is sometimes called targeted radiotherapy, but this latter term can also refer to radionuclides linked to non-immune molecules."[7]

Radiotherapy can be classified by the target of the therapy:

  • Hemibody Irradiation
  • Whole-body Irradiation
  • Lymphatic Irradiation

Computer-assisted radiotherapy

Computer-assisted radiotherapy is the use of "computer systems or programs used in accurate computations for providing radiation dosage treatment to patients."[8] Methods of computer-assisted radiotherapy include:


  1. National Library of Medicine. Radiotherapy. Retrieved on 2007-12-26.
  2. Symonds RP (2001). "Recent advances: Radiotherapy". BMJ 323 (7321): 1107–10. PMID 11701579[e] Fulltext at PubMed Central
  3. Zietman AL, DeSilvio ML, Slater JD, et al (2005). "Comparison of conventional-dose vs high-dose conformal radiation therapy in clinically localized adenocarcinoma of the prostate: a randomized controlled trial". JAMA 294 (10): 1233–9. DOI:10.1001/jama.294.10.1233. PMID 16160131. Research Blogging.
  4. Pollack, Andrew (2007). Hospitals Look to Nuclear Tool to Fight Cancer - New York Times. New York Times. Retrieved on 2007-12-26.
  5. National Library of Medicine. High-Energy radiotherapy. Retrieved on 2007-12-26.
  6. National Library of Medicine. Brachytherapy. Retrieved on 2007-12-26.
  7. National Library of Medicine. Radioimmunotherapy. Retrieved on 2007-12-26.
  8. National Library of Medicine. Computer-assisted radiotherapy. Retrieved on 2007-12-26.