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6.2 Radiotherapy Techniques

​Updated: May 2003

The following types of radiation therapy may be recommended depending on the individual circumstances of the patient.

Interstitial radiotherapy (brachytherapy)

This technique is usually reserved for accessible, small tumours often in the mouth or oropharynx. Radioactive sources are placed in and/or around the tumour. The sources may be removed once the tumour has received the appropriate dose or they may remain in place potentially forever thereafter. In the latter case the sources lose their radioactivity in a matter of weeks and then present no risk to the patient or those around them. The initial part of the implant usually requires sedation or a general anesthetic and a short admission to hospital.

External beam radiotherapy

This is the most common form of radiotherapy. A beam, or combination of beams, of either X rays or electrons is directed at the tumour and/or surrounding tissues. Treatments are given once or twice daily (twice daily treatments are given approximately 6 hours apart), each treatment lasts for approximately 10 minutes. Most treatment courses last for between 4 and 7 weeks.

The volume of tissue treated may be confined to the tissues immediately adjacent to the tumour (such as for early cancers of the larynx) or may include both the primary tumour and the lymph nodes on both sides of the neck as in the treatment of most cancers of the nasopharynx.

Immobilisation

In order to give high doses of radiation to the target volume while at the same time limiting the dose to adjacent normal tissues, patient movement must be kept to a minimum. To achieve this, a custom made immobilisation mask is produced for most patients. The mask is worn for any treatment planning scans and for each radiation treatment.

3-D conformal and stereotactic radiotherapy

An external beam radiotherapy technique in which multiple beams are used to shape the high dose of radiation around the tumour. Stereotactic radiotherapy is a conformal technique in which multiple small fields are used to treat tumours that are very close to critical structures such as the optic chiasm. Special immobilisation devices are needed for stereotactic treatment.

Intensity modulated radiotherapy (IMRT)

An external beam radiotherapy technique in which the usual uniform intensity of the beam is changed so that the intensity varies across the beam. In certain circumstances this produces a better dose distribution around the tumour and greater sparing of the adjacent normal tissues than conformal radiotherapy.

SOURCE: 6.2 Radiotherapy Techniques ( )
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