WHAT IS THE TOMOTHERAPY HI·ART SYSTEM®?
The TomoTherapy Hi·Art SystemÃ† is a new way to deliver radiation treatment for cancer. It delivers a very sophisticated form of IMRT, or intensity modulated radiotherapy, and integrates treatment planning, patient positioning, and treatment delivery in one system.
In order to understand what all this means for cancer treatment, it might be helpful first to get some background information on radiotherapy.
TREATING CANCER WITH RADIATION
Radiation is one of the most effective cancer treatments available. It works by damaging the cells it strikes: when the cancer cells are damaged enough, they will die. But what happens to healthy cells that are struck by the radiation beam? The key factor for radiotherapy is that healthy cells can repair themselves better than cancer cells. That’s why radiotherapy treatments are divided into many treatments, or fractions, over several weeks. Delivering a little radiation to the tumor area every day gives healthy cells time to recover between each session, while causing irreparable damage to more and more cancer cells.
Radiation treatment is also usually directed at the tumor from several different directions, so that more radiation is targeted on the tumor, but a lesser dose is spread over the surrounding healthy tissue.
Even though normal tissue can recover from exposure to radiation, there are often side effects, and of course too much radiation can damage normal tissue beyond repair. Until recently, it was very difficult for doctors to deliver enough radiation to kill a tumor without causing painful or debilitating side effects. Some side effects might go away once the treatment is complete, but others could continue to affect quality of life for years.
Of course, one of the goals of any radiation therapy is to avoid healthy tissue as much as possible, but some healthy cells will be damaged by the radiation treatment. So doctors and scientists have begun to look for better ways to deliver enough radiation to the tumor, while sparing normal tissue as much as possible. One of the most promising methods is IMRT, or intensity modulated radiotherapy.
HOW DOES THE TOMOTHERAPY HI·ART SYSTEM® WORK?
The TomoTherapy Hi·Art SystemÃ† combines treatment planning, patient positioning, and treatment delivery into one system, in order to deliver precise treatment doses without increasing the radiation deposited on healthy tissue.
Before beginning a TomoTherapy Hi·Art treatment, the doctor uses 3D images (for example, from CT) and special software to establish the precise contours for each region of interest (tumor) and any regions at risk (sensitive organs or structures). The doctor decides how much radiation the tumor should receive, as well as acceptable levels for surrounding structures. Then the TomoTherapy Hi·Art System calculates the appropriate pattern, position, and intensity of the radiation beam to be delivered, to match the doctor’s prescription as closely as possible.
The TomoTherapy Hi·Art System will allow doctors to take a special CT scan just before each treatment, so they can verify the position of the tumor, and adjust the patient’s position if necessary to make sure the radiation is directed right where it should be.
HELICAL TREATMENT DELIVERY
The TomoTherapy Hi·Art System combines IMRT with a helical (or spiral) delivery pattern to deliver the radiation treatment. Photon radiation is produced by a linear accelerator (or linac for short), which travels in multiple circles all the way around the gantry ring. The linac moves in unison with a device called a multileaf collimator, or MLC. The computer-controlled MLC has two sets of interlaced leaves that move in and out very quickly to constantly modulate the radiation beam as it leaves the accelerator. Meanwhile, the couch is also moving, guiding the patient slowly through the center of the ring, so each time the linac comes around, it’s directing the beam at a slightly different plane.
The TomoTherapy Hi·Art System has been designed to advance the goals of more accurate treatment with fewer side effects. How does the Tomo (tm) Process help accomplish this?
The TomoTherapy Hi·Art System uses a treatment planning optimizer, which is easier to use than conventional treatment planning systems.
The TomoTherapy Hi·Art System uses special verification CT to confirm the position of the patient’s tumor before each treatment fraction, so the clinician can adjust the plan on the spot to make sure the radiation is directed right where it should be.
While conventional radiotherapy delivers a wide beam of radiation from just two or three directions, the TomoTherapy Hi·Art System combines sophisticated IMRT with spiral delivery. So the desired radiation gets concentrated on the tumor, and less radiation gets deposited on surrounding healthy tissue.
The TomoTherapy Hi·Art System is an all-in-one system that eliminates the need for a simulator, separate treatment planning computers, block cutting and compensator molding facility, and portal imaging systems.