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What is RapidArc?

RapidArc™ radiotherapy technology is a new form of image-guided, intensity-modulated radiation therapy (IMRT).  Image guidance improves tumor targeting, and IMRT shapes the radiation dose so that it conforms closely to the three-dimensional shape of the tumor.  This means more dose to the tumor, and less to surrounding healthy tissue.

RapidArc quickly delivers a complete IMRT treatment with a single rotation of the treatment machine around the patient. The entire tumor volume receives the radiation dose during this one revolution of the machine. 

RapidArc involves varying (or modulating) the intensity of the radiation (in this case, high-energy X-rays) being used as therapy for cancer.

To administer a RapidArc treatment, clinicians use computer-generated images to plan and then deliver tightly focused radiation beams to cancerous tumors.  Using RapidArc technology, clinicians can deliver a precise radiation dose that conforms to the shape of the tumor, while limiting the amount of radiation that reaches surrounding healthy tissues.

A significant benefit provided by RapidArc is the speed of a treatment. A RapidArc treatment is delivered with a single 360-degree rotation of the linear accelerator, which takes less than two minutes.

Why would I want to be treated with RapidArc?

RapidArc is an extremely fast and precise form of radiation therapy.  It allows clinicians to quickly and accurately deliver dose to cancer cells while keeping the dose to surrounding tissues as low as possible.  

Faster treatments are not only more comfortable, they may also be more accurate. Since a patient will spend less time holding still, it will be easier to avoid movements that could compromise the accuracy of the treatment. RapidArc delivers treatments two to eight times faster than earlier forms of radiotherapy. 

What kind of radiation is used in RapidArc?

Photons (X-rays) are used to deliver RapidArc. The radiation is generated by a machine called a medical linear accelerator. This machine stands approximately nine feet tall, is nearly 15 feet long and can be rotated around the patient with amazing precision. Operationally, microwave energy, similar to that used in satellite television transmission, is used to accelerate electrons to nearly the speed of light. As they reach maximum speed they collide with a tungsten target, which in turn releases photons, or X-rays. 

Very small beams with varying intensities can be aimed at a tumor from multiple angles to attack the target in a complete three-dimensional manner. In fact, RapidArc can be delivered with beams the size of 2.5 x 5-millimeter pixels—the size of a pencil tip—each with varying intensity.  The idea is to deliver the lowest dose possible to the surrounding healthy tissue, while still delivering the maximum dose to the tumor.

How does radiation therapy work?

Cancer cells grow and divide more rapidly than many of the normal cells around them. High doses of radiation can kill cells or keep them from growing and dividing, and they have proven to be particularly effective in killing cancer cells and shrinking tumors – cells that divide and grow quickly.  Although some normal cells are affected by radiation, most normal cells recover more fully from the effects of radiation than do cancer cells. 

Does radiation therapy expose people to radioactive substances?

Many people, when they hear the word “radiation,” think immediately of radioactive substances.  However, no radioactive substances are involved in the creation of X-rays or electrons by a medical linear accelerator. When a linear accelerator is switched “on,” radiation is produced and aimed directly at cancer cells.  Then, like a flashlight, when the machine is switched off, the radiation is gone – it no longer exists.

What happens when a person is treated with RapidArc?

RapidArc treatment involves three basic steps: diagnosis, treatment planning and delivery.  As part of diagnosis, the medical team generates three-dimensional diagnostic images (usually CT or MRI) of the patient’s anatomy and uses these images to specify the dose of radiation needed to treat the tumor. In some cases, treatment planning includes a simulation session to further localize the cancer and finalize the radiation treatment plan.

Patients receive RapidArc treatments according to various schedules, usually five days a week for six or seven weeks. During a RapidArc treatment, the linear accelerator rotates around the patient to deliver the radiation from nearly every angle. The radiation is shaped and reshaped as it is continuously delivered from virtually every angle in a 360-degree revolution around the patient. Treatment consisting of a 360-degree revolution takes less than two minutes.

What is Varian’s RapidArc radiation therapy?

The main advantages of Varian’s RapidArc are precision and speed.

RapidArc treatments focus the radiation on the tumor while protecting surrounding healthy tissues.  A computerized tool called a multileaf collimator (MLC) shapes the beam in accordance with the optimized treatment plan.  Varian offers the highest resolution MLC on the market today, one that can deliver unique doses to very small areas.

In addition, treatment with Varian's RapidArc is fast.  A daily treatment can be delivered in less than two minutes.

It is believed that faster treatments may also be more accurate. Since a patient will spend less time holding still, it will be easier to avoid movements that can compromise the accuracy of the treatment.

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