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Radiation treatment is the use of x-rays, electrons or gamma rays to treat cancer. Radiation can cure or control cancer by killing the cancer cells and/or inhibiting the cells from dividing or reproducing. Almost 60 percent of patients with cancer will require radiation at sometime during their lifetime. Radiation is a safe and effective form of treatment for patients of all ages.
About the Linear Accelerator
A linear accelerator is the device most commonly used for external beam radiation treatments for patients with cancer. The linear accelerator can also be used in stereotactic radiosurgery and stereotactic body Radiotherapy similar to that achieved using the gamma knife on targets within the brain and body. The linear accelerator is used to treat all parts/organs of the body.
[Shown: The Varian Linear Accelerator at CVMC's National Life Cancer Treatment Center.]
The linear accelerator uses microwave technology (similar to that used for radar) to accelerate electrons in a part of the accelerator called the "wave guide", then allows these electrons to collide with a heavy metal target. As a result of the collisions, high-energy x-rays are produced from the target. These high energy x-rays will be directed to the patient’s tumor and shaped as they exit the machine to conform to the shape of the patient’s tumor. The beam may be shaped either by blocks that are placed in the head of the machine or by a multileaf collimator that is incorporated into the head of the machine. The beam comes out of a part of the accelerator called a gantry, which rotates around the patient. The patient lies on a moveable treatment couch and lasers are used to make sure the patient is in the proper position. 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.
Types of Treatment
Various types of treatments exist and may be ordered by your radiation oncologist upon review of your particular cancer type ans stage. The treatments the National Life Cancer Treatment Center offer are as follows:
Volumetric Modulated Arc Therapy/SmartArc
VMAT is an advanced form of intensity-modulated radiation therapy (IMRT) in which the treatment machine rotates around the patient while the treatment beam is on. The basic promise of VMAT delivery is to significantly reduce treatment time per patient compared with traditional IMRT. VMAT can benefit the patient by offering shorter treatment times, increased accuracy and better sparing of healthy tissue. Reduced treatment time also results in decreased stress for patients.
Stereotactic Body Radiation Therapy
Stereotactic body radiation therapy (SBRT) is a treatment technique that uses special equipment to deliver highly accurate, precise, and focused beams of radiation. This targeting allows treatment of small- or moderate-sized tumors in either a single or limited number of dose fractions. With SBRT, higher doses of radiation can be delivered in fewer treatments; typically, treatments are delivered in one to five treatments instead of multiple weeks required with conventional radiation therapy.
Intensity Modulated Radiation Therapy
Intensity-modulated radiation therapy (IMRT) is an advanced mode of high-precision radiotherapy that utilizes computer-controlled linear accelerators to deliver precise radiation doses to a malignant tumor or specific areas within the tumor. IMRT allows for the radiation dose to conform more precisely to the three-dimensional shape of the tumor by modulating—or controlling—the intensity of the radiation beam in multiple small volumes. IMRT also allows higher radiation doses to be focused to regions within the tumor while minimizing the dose to surrounding normal critical structures.
Image Guided Radiation Therapy
Image Guided Radiation Therapy, or IGRT, is used to help better deliver radiation therapy to cancerous tumors. This is very useful since tumors can move between treatments due to differences in organ filling or movements while breathing. IGRT involves conformal radiation treatment guided by specialized imaging tests, such as X-rays, ultrasound or CT scans. These tests are done in the treatment room just before the patient is to receive their daily radiation therapy treatment.
3D Conformal Radiation Therapy
3D conformal radiation is a technique that sculpts radiation beams to the shape of a tumor. This is ideal for tumors that have irregular shapes or that lay close to healthy tissues and organs. Using this radiation technology, we’re first able to view a tumor in three dimensions with the help of image guidance. Based on these images, we then deliver radiation beams from several directions to the tumor. Matching the radiation dose to the exact dimensions of the tumor allows us to deliver a higher dose, while limiting radiation exposure to surrounding healthy tissues.