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Intensity Modulated Radiation Therapy (IMRT) in India

Radiotherapy

Radiotherapy is a treatment involving the use of high-energy radiation. It’s commonly used to treat cancer.

Almost half of all people with cancer have radiotherapy as part of their treatment plan.

Radiotherapy is also sometimes used to treat benign (non-cancerous) tumours and other conditions, such as thyroid disease and some blood disorders.

Radiotherapy can be used, alone or in combination with chemotherapy (chemoradiotherapy), to try to cure cancers.

For people with incurable cancers, radiotherapy is a very effective way of controlling symptoms.

Radiotherapy can also be used before surgery to shrink a tumour so it’s easier to remove (known as neoadjuvant treatment), or after surgery to destroy small amounts of tumour that may be left (known as adjuvant treatment).

The calculation of the amount and type of radiation is done carefully so as to destroy cancer or abnormal cells. This entire procedure properly divides these cells for destroying them and causes little or no damage to the surrounding healthy cells.

IMRT Radiation Therapy

Intensity modulated radiotherapy (IMRT) is a type of conformal radiotherapy. Conformal radiotherapy shapes the radiation beams to closely fit the area of the cancer. Each radiotherapy beam is divided into many small beamlets that can vary their intensity. This allows different doses of radiation to be given across the tumour.

IMRT can also create a U shaped (concave) area at the edge of the radiotherapy field. This avoids high radiation doses to structures that would otherwise be damaged by the radiotherapy. So IMRT can reduce the risk of long term side effects. It is very helpful in areas such as the head and neck, for example to avoid the spinal cord or salivary glands.

The intensity of the radiation in IMRT can be changed during treatment to spare more adjoining normal tissue than is spared during conventional radiation therapy. Because of this an increased dose of radiation can be delivered to the tumor using IMRT. Intensity modulated radiation therapy is a type of conformal radiation, which shapes radiation beams to closely approximate the shape of the tumor.

When IMRT is used?

It’s mainly used  to treat breast, head and neck, prostate, bladder and lung cancers.

Because IMRT can reduce the risk of damaging healthy tissue near the cancer, it’s sometimes used in situations where the tumour is very close to important organs or structures. For example,

Intensity-modulated radiotherapy (IMRT).when IMRT is used to treat pelvic tumours, it can reduce the risk of long-term bowel problems.

When it’s used for head and neck tumours, it can reduce damage to the salivary glands and the risk of permanent mouth dryness. It may also allow higher doses of radiotherapy to be given to the tumour

Types of Cancer Treated with IMRT

  • Spinal Cord Cancer
  • Bone Cancer
  • Prostate Cancer
  • Head and Neck Cancer
  • Gastrointestinal Cancer
  • Brain Tumors
  • Lung Cancer
  • Gynecologic Cancer
  • Breast Cancer

Procedure of IMRT

The key behind IMRT is the use of inverse planning. Unlike standard approaches, the target and normal tissues are first contoured on a planning computed tomography (CT) scan. Computerized optimization programs are used to generate the intensity profile of each radiation beam (typically 7-9 are used).

During this process, beams are divided into small “beamlets” and the intensity of each beamlet is individually optimized to satisfy pre-determined planning goals.

When cast into the patient, these modulated beams produce highly conformal treatment plans. Rapid dose gradients outside the target result in considerable sparing of nearby normal tissues.

Such plans are almost always superior to conventional plans, particularly in patients with complex-shaped targets.

Facilitating the delivery of IMRT is a device known as a Multi-Leaf Collimator (MLC). Positioning in the machine head, the MLC has leaves which move in and out of the beam’s path under computer control.

The longer the leaves are open, the higher the intensity; the longer they are closed, the lower the intensity.

Treatment sessions : The painless IMRT treatment sessions begins that takes 10-30 minutes to complete. The type of cancer determines the number of treatment sessions.

Benefits of IMRT

  • Improved target conformity, particularly for concave target volumes
  • Can produce intentional dose inhomogeneity—dose-painting
  • Increases normal tissue sparing
  • Enables dose escalation
  • Can compensate for missing tissue.