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Linear Accelerator

Linear Accelerator or LINAC is advanced technology equipment that customizes x-rays of high energy to conform to the shape of a tumor and then destroy the cancerous cells, without causing any damage to the surrounding healthy tissues. It is usually used during radiation therapy to ensure absolute safety during treatment.It can be used along with any conventional technique such as IMRT (Intensity-Modulated Radiation Therapy), IGRT (Image Guided Radiation Therapy), SRS (Stereotactic Radiosurgery) and SBRT (Stereotactic Body Radio Therapy). The radiation treatment given using the LINAC is often known as the external beam radiation therapy.

How it works
  • Using microwave technology the linear accelerator accelerates electrons within a part of it known as the wave guide.
  • These electrons then collide with a heavy metal target and generate high-energy x-rays
  • As these high energy x-rays exit the machine they are shaped according to the shape of the tumor
  • The patient lies down on a treatment couch that is movable. Using lasers, the patient is made to lie down in a proper position. The couch can be moved in any direction such as up, down, left, right, in or out.
  • The part of the accelerator that emits the beam is known as the gantry. It can be rotated easily around the patient. This gantry makes it possible for radiation to be delivered from any angle.
LINAC controls the dosage that needs to be delivered, thus making the radiation therapy extremely safe and effective. By using a linear accelerator, cancerous cells can be destroyed from any part of the body, without causing any damage to the normal tissues that surround the tumor. 
Side Effects & Risks
Linear accelerator delivers high-energy x-rays directly to the cancerous cells and tissues. Although it ensures not to cause any damage to the surrounding healthy tissues, there are certain side effects that cannot be avoided. These include:
  • Problems with balance
  • Dizziness
  • Nausea 
  • Vomiting
  • Headache
  • Problems with vision
  • Seizures
  • Swelling of the brain 
Nevertheless, these side effects should start disappearing within a few days from the day of the treatment.
Preparing for External Beam Radiation Therapy
The radiation oncologist will first review your medical tests such as your MRI scans, CT scans and PET scans. Then he will come up with a treatment plan in collaboration with the physicist and the radiation dosimetrist. Based on this plan the radiation oncologist will write a prescription that gives full details about the amount of radiation therapy you will receive and the parts of your body that are to be treated.
Quality-control procedures will be put in place and the plan would be double-checked thoroughly prior to the treatment. 
A couple of things need to be checked in order to make sure the radiation treatment is safely delivered. These include:
  • Checking the machine through the tracker every morning, to ensure uniform delivery of the radiation intensity
  • Detailed weekly as well as monthly checks of LINAC
  • Making sure all the prescribed treatment requirements are met before the machine is turned on
  • Observing the patient continuously through a closed-circuit TV monitor
  • Checking imaging tools such as port films and cone beam CT regularly, so as to ensure the beam position is as per the original plan
  • Making sure the LINAC is positioned in a room made out of lead and concrete walls that will shield the high-energy x-rays, making sure none of the staff is exposed to the x-rays. 
What to Expect after External Beam Radiation therapy?
Being a non-invasive treatment, you won’t feel any pain during the treatment. The process is very similar to taking an X-ray. It is an outpatient treatment, which doesn’t involve any recuperation period. The treatment sessions would be scheduled 5 days a week for anywhere between 1 to 10 weeks depending upon the type of cancer you have, the size and location of your tumor, the purpose of your treatment and your overall health.
At times the sessions may be interrupted for a day or two. This usually happens when you happen to develop side effects. The missed sessions however add up to your treatment sessions at the end. Each session may take anywhere between ten to forty minutes. It is advisable to follow your treatment schedule as instructed by the radiation oncologist.
The radiation doses may be changed with time. You may be asked to go for x-rays and blood tests to make sure you are responding well to the treatment. If need be the radiation oncologist might even change the treatment.
Your radiation oncologist may meet with the other team members to review your case on a weekly basis. This is to ensure things go as planned. Your progress and concerns will be reviewed during these sessions.
Results of External Beam Radiation Therapy
You may need a lot of rest after external beam radiation therapy. You will have to eat a balanced diet and limit your activities until your strength resumes. There may be some life style changes you may have to adopt. If things go well, you could even go back to work and lead a normal life.