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Image-guided Radiotherapy (IGRT)

Image-guided radiation therapy (IGRT) uses medical imaging to precisely locate the tumor and ensure accurate radiation treatment. In IGRT, a linear accelerator equipped with on board imaging (e.g. 4D CBCT) is used. In IGRT, imaging is used on regular basis to guide the treatment during the entire course of treatment. Your doctor will match these scans taken before delivery of radiation with the simulated reference images. This ensures precise delivery of radiation to the tumour, sparing of the normal healthy tissues and precise dose delivery.

 

For the purpose of radiation various types of scanning are used for planning radiotherapy. It includes computed tomography (CT), magnetic resonance imaging (MRI), PET-CT. Fiducial markers or electromagnetic transponders might be inserted into the tumor or close by during the surgery to help in locating the target particularly when it is a moving target.

 

Using fiducial markers, 4D gating, or adaptive approaches with high soft tissue resolution imaging, IGRT can be used for the treatment tumours that are prone to movement, such as the lungs, liver. Tumors close to vital organs and tissues are also treated by IGRT. Doctors may combine IGRT with proton therapy, stereotactic radiosurgery, intensity-modulated radiation treatment (IMRT), or stereotactic body radiotherapy (SBRT). Higher radiation doses may be delivered using IGRT, increasing the likelihood of tumor control.

 

Procedure:

 

Before you undergo this therapy, your doctors will conduct a thorough physical examination. Usually, pregnant women not taken for radiation. She may be taken for radiation only when the benefit exceeds the risk.

If required, the fiducial markers will be implanted by your doctor at least a week before CT simulation. To assist with the alignment help of laser beams will be taken along with other accessories available with the Linear Accelerator will be used for guidance. You may be given specific instructions to follow during simulation process e.g. breath holding, drinking a specified amount of water and voiding before scanning.

 

During the procedure:

 

The radiation therapists carefully place you on the treatment couch before each session. To assist you in maintaining the required posture, they may employ mould devices. You might need to hold your breath or follow the instructions given.

Every day of therapy, the therapist will start by gathering images to be examined and compared with the simulation images. Your therapists will begin the therapy after making any necessary modifications.  Each therapy session will take longer than conventional radiotherapy because of the required additional imaging guidance method.

 

Recovery:

 

Radiotherapy is usually well tolerated. However, like with other treatment modalities, it may also lead to some side effects.  The side effects of radiation will vary in nature and intensity depending upon the types of radiation, dosage, and area of body and the depth where the tumour is located. It will vary patient to patient and hence you should never compare these with other patients.  While on radiation treatment you should consult radiation oncologist as per the instruction and as and when required. Consult your physician or the nurse so they can assist you in managing them. You should also follow the advices of the radiation oncologist and the take the medications as per the instruction. 

 

The side effects include weariness and skin reactions. Skin that has been treated may become itchy, sensitive, red, or swollen. Further alterations include dryness, stinging sensation, peeling, and blistering. Radiation oncologist may prescribe medications to mitigate these side effects.

 

Other early side effects may depend on the location being treated and may

  • Hair loss in the treatment area
  • Mouth problems and difficulty swallowing
  • Eating and digestion problems
  • Diarrhoea
  • Nausea and vomiting
  • Headaches
  • Soreness and swelling in the treatment area
  • Urinary and bladder changes

There is a small risk of development of secondary cancers. Majority of these side effect settle by itself. However, in some cases these side effects may persist longer.

 

Conclusion:

 

Image-guided radiation therapy (IGRT) uses medical imaging to precisely locate the tumor, ensure accurate radiation dose delivery, and sparing normal healthy tissues while undergoing radiation therapy. In IGRT, commonly, a linear accelerator equipped with on board imaging (e.g. 4D CBCT) facility is used on a regular basis. Image guidance can be used with various radiotherapy techniques like IMRT. A higher dose delivery is possible with IGRT.

Medanta Medical Team
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