Intensity-modulated radiation therapy (IMRT)

Specialty of Clinical oncology

What is intensity-modulated radiation therapy (IMRT)?

Intensity modulated radiotherapy (IMRT) is an advanced type of high-precision radiation therapy. It uses advanced technology to control proton and photon beams of radiation to administer precise doses of radiation to malignant tumours in the patient.

Each radiotherapy beam is divided into smaller beams and the intensity of each small beam can be modulated, allowing the operator to deliver high-intensity radiotherapy to certain areas of the cancer, while delivering lower doses in areas close to healthy cells, reducing unnecessary exposure of non-cancerous cells to radiation. The machine is able to move around the patient, fitting the beam around the area being treated and, using MRI and PET scans, delivers the radiotherapy with high precision to the three-dimensional shape of the tumour.

Why is IMRT done?

Intensity-modulated radiation therapy is used to treat a number of different types of cancer, including prostate, head and neck, central nervous system, breast, thyroid and lung cancer.

Radiotherapy targets and kills cancer cells, shrinking the tumour and hopefully destroying it altogether.

Preparation for intensity-modulated radiation therapy

Before intensity-modulated radiation therapy, a physical examination of the patient should be done and their medical history reviewed. The patient will undergo a CT scan and may also have an MRI and/or PET scan to allow the treatment team to visualise the exact shape and size of the tumour and carefully plan the procedure, including the dose strength pattern. It can take up to two weeks after the scan to plan the treatment.

What does intensity-modulated radiation therapy (IMRT) consist of?

IMRT usually requires several treatment sessions, depending on the type, location and size of the tumour as well as the patient's health.

At the beginning of the session the patient lies on a table. Once they are in position, the doctor leaves the room. The patient should keep still during the procedure, which is often guided by scanners. The sessions will last approximately between 15 and 30 minutes.

During the treatment itself, there is usually no pain although there may be discomfort due to the position the lie in.

Care after the intervention

Some patients may experience certain side effects related to the treatment, which will depend on the type of radiation and the dosage received as well as the area treated. Early side effects usually occur during or immediately after the treatment and disappear after a few weeks, including tiredness or fatigue and even skin problems (most sensitive areas).

Late side effects can occur months or years after radiation therapy, and are often permanent. These include changes in the brain, spinal cord, lungs, kidneys, colon and rectum, infertility and even cancer, among others. Depending on the side effects and when they occur, the doctor will advise treatment and follow-up.

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