Image-Guided Radiotherapy (IGRT)

Physicians at the North Mississippi Medical Center Cancer Center have begun using a new image-guided radiotherapy (IGRT) treatment for cancer patients using an advanced imaging system to more precisely locate tumors at the moment of treatment.

The new technology from Varian Medical Systems combines imaging and treatment on one machine, providing fast and accurate adaptive radiotherapy treatments that deliver high doses of radiation directly to cancer cells while minimizing the dose to surrounding healthy tissues. Until now, radiation oncologists have had to deal with variations in patient position and target motion by including a margin of healthy tissue around the tumor to account for variation in daily positioning.

“Our new image-guidance technology gives us the capability to image the patient before we begin treatment,” said radiation oncologist Bert Duncan, M.D. “This allows us to more effectively target the tumor and reduce the exposure of surrounding normal tissues, as well as keep the tumor in the center of the radiation field.”

 Dr. Duncan said the new technology should lead to better outcomes with fewer side effects and complications for patients. IGRT is used to treat tumors virtually anywhere in the body, including those in the brain, head and neck, lung, liver, prostate and other areas.

“IGRT is a major step forward in radiation oncology,” Dr. Duncan said. “This will become the new standard of care for cancer treatment. By providing IGRT to its patients, NMMC shows its continued commitment to provide patients with the most up-to-date care available.”

 

Intensity Modulated Radiation Therapy (IMRT)
 
The most precise treatment option available for radiation oncology patients is now available at North Mississippi Medical Center’s Cancer Center.

This radiotherapy system, which includes two new linear accelerators, is capable of delivering IMRT (Intensity Modulated Radiation Therapy). “The new equipment treats cancer with precisely placed beams that can be focused to carefully target tumor cells without harming surrounding tissue,” said radiation oncologist W. Ray Reed Jr., M.D. “NMMC is among the first hospitals in the nation to offer this leading-edge technology.”

NMMC’s clinicians will use the new SmartBeam® IMRT system from Varian Medical System of Palo Alto, Calif., to treat patients with certain types of cancer with precisely placed beams that can be focused to carefully target tumor cells.

Varian, the equipment’s manufacturer, has designated NMMC’s Cancer Center as a national reference site. Representatives from other programs will visit the center to emulate its services. “This new technology is comparable to that used at some of the nation’s leading cancer programs, including Mayo Clinic, M.D. Anderson, and university hospitals such as UAB, Emory, Vanderbilt and Duke,” Dr. Reed said.

Radiation oncologist Bert Duncan, M.D., said, “This new equipment enables us to treat cancer with laser-like precision. We now have the potential to substantially improve both patient comfort and cure rates by protecting healthy tissue while delivering more powerful doses to the tumor.”

The enhanced doses increase the likelihood that a tumor will be completely eradicated. Also, the new technology enables clinicians to use radiation to treat areas that would have been considered too risky just a few years ago.

“This technology is ideal for prostate cancer patients because the preciseness available with this equipment spares healthy tissue more than ever before,” Dr. Duncan said. “This lessens the chance for damage to the bladder and rectum. The same holds true for cancer of the head and neck. The enhancements mean there is less chance that the radiation will damage the optic nerve or salivary glands.”

Each of the new linear accelerators stand approximately nine feet tall by nearly 15 feet long and weigh about 18,700 pounds. The units generate high energy X-rays by using microwave energy to accelerate electrons to nearly the speed of light. As the electrons reach maximum speed, they collide with a metal target to release photos (or X-rays). The accelerator rotates around the patient to deliver the radiation treatments from nearly any angle. The equipment is housed in treatment rooms with lead-lined walls.

An important component of the linear accelerator is the multi-leaf collimator. The device’s 120 computer-controlled mechanical “leaves” or “fingers” are used to shape the beam of radiation so that it conforms to the three-dimensional shape of the tumor.

“These leaves do much more than shield healthy tissue,” Dr. Reed said. “The tiny leaves are constantly moving and rearranging the radiation beam so it hits the target while avoiding healthy surrounding tissue.”

“Another improvement is patients spend less time receiving treatment,” Dr. Reed said. “In the past, custom treatment blocks were developed for each patient. If more than one area was treated, the blocks would be removed and the other set put in place. Now with all treatment plans computerized, treatment isn’t stopped to reposition the patient and treatment blocks.”

The technology compliments NMMC’s 3-D computer software that clinicians use to plan, simulate and deliver IMRT and other kinds of ultra-precise cancer care.

Dr. Duncan compares the new enhancements to going to the tailor and having a suit custom made. “We can tailor the radiation beams to conform to the tumor from basically any direction, like a perfectly fitting suit,” he said. “We simulate the radiation treatment before the patient even gets on the table. Using mathematical models and visualization software, we mimic the radiation beams and emulate the patient. Then, we enable the computer to determine how the radiation will affect different parts of the body, depending on how the radiation fields are organized.”

On average, radiation therapy treatment regimes average five days per week for approximately six weeks. Once the patient is on the table, a treatment typically takes about five to 10 minutes.