Intensity Modulated Radiation Therapy
Rajiv Gandhi Cancer Institute & Research Centre boasts of being the first cancer centre in the country to put IMRT into clinical practice.
Intensity Modulated Radiation Therapy (IMRT) is an approach to radiation therapy that delivers a high, conformal dose to the tumor while restricting the exposure to surrounding normal tissue.
The benefits of IMRT include:
- IMRT delivers higher doses of radiation for destroying the tumor, regardless of size, shape or location, thus enabling a higher chance of cure.
- IMRT uses computer-generated images to plan and delivers tightly focused radiation beams, thereby sparing surrounding healthy tissue. Hence side effects are minimized.
- IMRT may make re-treatment with radiation possible, since healthy tissue initially received less radiation than with conventional therapy. The radiation beams are planned to avoid critical structures.
- IMRT brings the advantages of radiation therapy to a wider range of cancer patients, including patients with difficult-to-reach tumors or tumors located close to vital organs.
IMRT uses multiple small radiation beam lets of varying intensities to precisely conform to a tumor. The radiation intensity of each beam is controlled, and the beam shape changes throughout each treatment using multi leaf collimators, allowing a relatively uniform dose to the tumor and a sharp fall-off of the dose to surrounding normal organs.
IMRT treatment planning and delivery flow chart
- Patient is immobilized to deliver the treatment.
- After the immobilization, the patient is simulated on the radiotherapy simulator
- CT scan is taken in the treatment position with immobilization mask and the entire area is scanned at 3 – 5 mm intervals.
- CT Scan slices are used for the target (tumor area) and other surrounding normal organ planes and dose volume, histograms are generated.
- Digitally reconstructed radiographs are used for verifying the treatment position.
- This is followed by transfer of the treatment parameters to treatment machine.
- Online portal imaging is used to verify, that treatment is delivered exactly as planned.