Teletherapy or external beam radiation therapy is a method which is used for delivering X-rays of high voltage to a cancer from a source of external radiation using a cobalt machine or a linear accelerator. A physician accurately targets the dosage of radiation to demolish the tumor cells without affecting the normal tissues within. The treatments are usually undergone once a day, for 5 days a week for around 2 to 9 weeks.
The therapy of external beam radiation does not include using sources of internal radiation or implanted radioactive plaques. Such therapy is effective in managing different kinds of cancers such as brain tumor, breast cancer, and lung and prostrate cancer.
Process adopted in external beam radiation therapy
In the process, X-rays of therapeutic intent are generated through accelerated electrons at high speeds. These electrons are available from radioactive isotopes like iridium-192 and cobalt-60.
As they move at a high speed, the electrons attack tungsten alloy, leading to fast deceleration for generating gamma rays which are monochromatic photon beams of high energy.
The level of energy varies according to the isotope used. This therapy takes place in 3 stages comprising planning, stimulation and treatment.
In stimulation, the best position of treatment for the patient is determined by obtaining CT or computerized axial tomography scans of the targeted organ having the patient in the said position. In external beam radiation therapy, pads and devices are created for keeping the patient in the place in each treatment. Marks are placed on the patient by therapists for guiding placement and inserting small marker seeds in the targeted organ or tumor.
Radiation physicists, dosimetrists and oncologists decide on the zones which are to be irradiated or avoided, calculate the volume of the tumor and correct the radiation dosage. Treatment commences once planning and simulation are complete.
In the beam radiation therapy, a patient is made to recline on the treatment couch in a position that is recommended. The radiation therapist places the patient according to the lasers and alignment marks. The position is verified through scans and X-rays, after which activation of the linear accelerator takes place. The duration of the treatment is usually from 10 to 30 minutes a day, with time being generally spent on attaining the appropriate alignment.
The accurate duration of the therapy depends on method of delivery and dosage. External beam radiotherapy is not painful. A humming sound is usually heard.
The ozone which is released by a linear accelerator can lead to electrical smells in the session. Some patients may occasionally notice colored lights, especially if they receive brain treatments. Before the first treatment is administered, you will meet a nurse or a doctor who will familiarize you with the procedure of the external beam radiation therapy and whether it has any side effects. In the physical examination, the doctor will speak to you about your medical history and overall health.
In the follow up meeting, small marks and tattoos are put on the skin of the patient for correct aiming of the radiation. During the therapy, the radiologist will speak to you via a speaker from another room and monitor your response to the therapy.