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18 August, 2010 | Linear Accelerators

A linear accelerator is the device used for high-energy x-radiation treatments to patients diagnosed with cancer.  It is very large and heavy apparatus, with highly sophisticated technologies driven by dedicated software.

The linear accelerator is located in a room with lead and concrete walls, so that the high-energy x-rays are shielded. The accelerator only gives off radiation when it is actually turned on; therefore the risk of accidental exposure is extremely low. The linear accelerator is used to treat all parts and organs of the body. It delivers a uniform dose of high-energy x-ray to the region of the patient’s tumor. These x-rays can destroy the cancer cells, while sparing the surrounding normal tissue.  The linear accelerator uses microwave technology to accelerate electrons which collide with a target, and as a result of the collisions, high-energy x-rays are produced and directed to the patient’s tumor. The x-rays are shaped by a multileaf collimator [think of a camera iris] that is incorporated into the head of the machine as they exit the machine to conform to the shape of the patient’s tumor.  The beam exits the accelerator through the accelerator “head” which is supported by a movable vertical arm. This assembly is called a gantry, which rotates around the patient. The rotation allows the radiation to enter the patient‘s body through a continuously changing area of skin. The skin is more sensitive to radiation than the inner structures of the body. The patient lies on a moveable treatment couch and lasers are used to make sure the patient is correctly positioned. The treatment couch can move in many directions including: up, down, right, left, in and out. Radiation can be delivered to the tumor from any angle, by rotating the gantry and moving the treatment couch.

A radiation oncologist prescribes the appropriate treatment.  Imaging is done to insure the beam position doesn’t vary from the treatment plan. A medical radiation physicist and the medical dosimetrist determine how to deliver the prescribed dose and calculate the amount of time it will take the accelerator to deliver that dose.

Each morning before any patients are treated, the radiation therapist performs checks on the machine to ensure that it is working properly, using a piece of equipment called a “tracker” to make sure that the radiation intensity is uniform across the beam. In addition, the radiation physicist makes more detailed weekly and monthly checks of the linear accelerator. Radiation therapists operate the linear accelerator and give patients their daily radiation treatments.  Internal checking systems prevent the machine from turning on until all the prescribed treatment requirements are perfect.  During treatment the radiation therapist continuously watches the patient through a closed-circuit television monitor. The patient can speak to the therapist, if needed, by microphone.

Manufacturers are continuously designing improvements to the hardware and software with the goal of higher dosages to the tumor, while shielding the adjacent tissue.

Radiation treatments incorporating the newest technologies continue to extend the lives of thousands of cancer survivors.

You can contact David at:

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this article was contributed By Global Medical Equipment Analysis Expert David Tortorich  – CEO International Radiographic Inc.