Intensity-modulated radiotherapy is an advanced radiation technique for treating cancerous and benign tumours. IMRT uses photons and protons of different intensities to kill cancer. The radiation intensity and shape can be controlled, so it only destroys the targeted tissue and leaves the normal tissues unaffected.
Therefore, limiting the side effects of usual cancer radiation therapy, when compared to conventional radiation, IMRT requires somewhat longer daily treatment times as well as additional planning and safety tests before the patient may begin treatment.
When is Intensity-Modulated Radiation Therapy (IMRT) Needed?
How Does IMRT Work?
Intensity-modulated radiation therapy is a high-precision radiotherapy technique that uses computer-controlled devices to deliver specific radiation doses to a malignant tumour or particular locations inside the tumour. By modulating the intensity of the radiation beam in many tiny sections, IMRT allows the radiation dose to adapt more accurately to the three-dimensional (3-D) structure of the target tissue. IMRT also enables larger radiation doses to be directed at the tumour while minimising the dosage to normal healthy tissues around it.
Types of Intensity-Modulated Radiation Therapy (IMRT)
- Volumetric Arc Therapy: VMAT is also known as Rapid Arc. VMAT differs from traditional IMRT in that the radiotherapy machine spins around the patient while emitting an arc-shaped radiotherapy beam. As it goes around the body, the machine constantly reshapes and alters the intensity of the radiation beam. Giving radiotherapy in this manner improves accuracy, reduces treatment time, and uses a lower overall dosage of radiation. The treatment typically lasts 10 – 15 minutes, depending on the complexity of the scan.
- TomoTherapy: To receive treatment, you recline on a radiation couch moved by a doughnut-shaped machine. The machine's radiation source rotates in a spiral pattern around you. It is also known as helical tomotherapy/helical IMRT.
How to Prepare for Radiation Therapy?
A physical examination and medical history review is performed before treatment planning. Following that, there is a treatment simulation session that includes CT scans. A tiny mark or tattoo may be placed on the patient's skin to help position and target the equipment. This scan will be used by the radiation oncologist to create a personalised treatment plan.
If the patient has radiotherapy to their head or neck, they may need to wear a radiotherapy mask during the treatment. They may wear a mask called a shell or mould. Most masks are made of mesh material with lots of holes. Moulds are also used for other body parts, such as the breast or limbs. The mould keeps the treatment area completely still, so the treatment will be as accurate as possible.
Prior to the simulation and therapy, the patient may be instructed to follow a specific bowel and bladder preparation routine or to fast. During the CT scan, intravenous contrast material may be administered to help clarify the tumour.
Sometimes additional scanning procedures, such as positron emission tomography (PET) and magnetic resonance imaging (MRI), may be necessary for IMRT planning. These images can be combined with the planned CT to assist the radiation oncologist in pinpointing the exact position of the tumour target.
In other circumstances, radio-dense markers must be inserted into the target for a more exact location. IMRT treatments often begin a week or two after simulation.
Intensity-Modulated Radiation Therapy (IMRT) Treatment Procedure
To receive the treatment, the patient lies down on a radiation couch. The radiographers will assist them in getting into the proper position and putting on any necessary moulds. They might receive therapy with a LINAC machine or another radiation machine, such as a TomoTherapy machine.
The radiographers will leave the patient alone in the room after they are properly positioned. This is done to protect them from radiation. X-rays are frequently taken before therapy. This is known as image-guided radiation, ensuring you are in the correct posture (IGRT).
The radiographers keep an eye on the patient, either through a window or on a closed-circuit television screen (CCTV). They can communicate with them over an intercom. During the treatment, they may instruct them to hold their breath or take shallow breaths. When the patient is receiving radiation, you cannot feel it. It does not hurt. It could take anywhere from 15 to 30 minutes or more.
How Long Does IMRT Take?
The time it takes depends on the nature of the cancer and the treatment plan. Generally, an IMRT treatment takes about 10 to 30 minutes. The patient may be in the treatment room for up to an hour, but every cancer is different. It's a good idea to ask the doctor what to expect.
While each procedure is short, the patient needs more than one. Doctors usually prescribe IMRT 5 days a week for a couple of weeks. Exactly how many times they will go also depends on their particular cancer and treatment plan.
Possible Complications After IMRT
IMRT is not supposed to be painful. If a patient develops discomfort because of the treatment position or positioning devices, the machine can be turned off anytime. Some patients may have therapy-related side effects as their treatment advances. The nature of the side effects is determined by the healthy tissues irradiated near the tumour. The radiation oncologist and the nurse will review the potential side effects and how to manage them.
Radiation therapy can have unintended consequences. These issues could be caused by the treatment itself or by radiation damage to healthy cells in the treatment area.
Possible Early Side-Effects of Radiation Therapy
- Hair loss
- Trouble swallowing
- Nausea and vomiting
- Soreness of throat
- Hoarseness of voice
- Skin irritation
- A burning feeling when you pee
- Trouble peeing
Possible Long-Term Complications:
- Secondary cancer
- Changes in the mouth, kidneys, brain, spinal cord, joints, or other parts of your body
- Swelling is caused by a blockage in the lymph system
It is important to understand that side effects are mostly organ/site-specific. Usually, when treated by trained radiation oncologists, side effects are under control and manageable.
Taking Care of Yourself After Radiation Therapy
While undergoing IMRT, the patient must take care of themselves to feel as strong as possible and to minimise any adverse effects as much as possible. Throughout the treatment, eat a healthy, balanced diet, get plenty of rest, and care for the skin area exposed to radiation.
Wear loose garments made of soft fabrics such as cotton. Avoid scratching or rubbing the treated area. Do not apply anything hot or cold on the treated area, such as an ice pack or heating pad. When taking a shower or bath, only use lukewarm water.
Following therapy, the patient's doctor will probably want to see them frequently to see how well it worked. They will also monitor things and assist with any side effects. The patient should continue to see their doctor for follow-up appointments for the foreseeable future.
Reviewed & Updated On
Reviewed by Dr. Dodul Mondal, Associate Director - Radiation Oncology, Head & Neck Oncology, Musculoskeletal Oncology, Radiation Oncology, Neuro Oncology, Cancer Care / Oncology on 09-May-2023.
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