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Published on February 22, 2010

Best Practices Support CT Scans, Allow Physicians to See Images Differently

128-Slice CT Scan

The use of advanced imaging with lowest-dose equipment, such as the Siemens 128-slice CT scanner at MidMichigan, is not only in the best interest of the patient by minimizing their exposure to radiation, but allows MidMichigan physicians to see images differently.

Have you had a CT scan? Should you be concerned about an increased risk of cancer because of radiation exposure?

During the past several weeks media have reported studies demonstrating concerns about radiation exposure during CT scans. CT stands for computed tomography, also called a CAT scan. It is advanced X-ray technology that uses a computer to produce detailed, 3-D pictures of tissue, bone and blood vessels.

“Even experts disagree on the assumptions and conclusions of studies that are being quoted,” said Rod Zapolski, director of imaging at MidMichigan Medical Center - Midland. “But most people agree that there are good ways to minimize risk in conducting these tests. The Medical Center in Midland has such provisions in place and applies them rigorously.”

Zapolski said ways to minimize risk include having well-qualified staff, strict protocols that are followed to the letter, and equipment designed to minimize patient exposure.

For example, the use of advanced imaging with lowest-dose equipment, such as the Siemens 128-slice CT scanner at MidMichigan, is not only in the best interest of the patient, but allows MidMichigan physicians to see images differently. "The 128-slice CT scanner allows superior visualization of anatomic structures while reducing the dose of radiation to the patient,” said Radiologist Timothy Berka, M.D., of MidMichigan’s Radiology Department and Midland Radiology Associates.

Every technologist registered
Zapolski said there is no substitute for qualified people. “All of our CT technologists are trained in radiation exposure by an accredited college or university,” he said. “We also require all to complete registry in X-ray and computed tomography, which means they must pass written board exams given by the American Registry of Radiologic Technologists specific to using CT technology.”

Quality control
The Medical Center is also the only CT program in the region and one of few in Michigan accredited by the American College of Radiology (ACR). “In 2012, this accreditation will be a requirement,” said Zapolski. “Currently, it is not common. We are the only Medical Center in the area that can make this claim.”

Accreditation requires that medical physicists visit the site and check procedures used to conduct a CT scan, including changing CT scanner settings. Settings control radiation dose, energy of the radiation beam, length of scan time and overlap of the beam patterns.

At MidMichigan, equipment settings are not allowed to be changed without the supervision of CT Lead Technologist Cory Wheeler, R.T. (R) (CT), and the direction of an application specialist for the scanner’s manufacturer, Siemens. Rigidly tracking setting changes is one of the best ways to prevent exposure to more than the necessary amount of radiation.

“Our protocols are well set to minimize radiation dose, and we are very good at monitoring them and getting them as low as we possibly can,” said Wheeler. “When the ACR tested us for accreditation, overall our exposures were 27.6 percent less than their recommended guidelines.”

Calibration measures are checked daily using a standard called a ‘water phantom’ to make sure the exposures stay in the proper range for different types of human tissue. “Overexposure does not make an image any better. We want to use the least exposure required to get the best image,” said Wheeler. “If these tolerances are not normal, we call Siemens service and they come and correct the problem.”

Other quality control procedures are performed weekly, quarterly and annually. “Preventive maintenance and upgrades are a vital part of our quality control program. Reducing radiation exposure is difficult if your equipment is not functioning properly and that’s why we perform these measures, to ensure top performance from our Siemens scanners,” Wheeler said.

The Medical Center also earned the Image Gently(SM) accreditation from the Alliance for Radiation Safety in Pediatric Imaging. “Facilities with this designation have verified their ability to image pediatric patients with the proper radiation dose,” said Wheeler.

Lowest-dose equipment
The Medical Center selected Siemens technology for CT scanners. “Siemens scanners produce the least amount of radiation dose in the industry, using technologies built in to their machines,” said Wheeler.

Some kinds of tissue, such as air-filled lungs, need less radiation than others, such as a hip joint, to get a good quality image. One Siemens feature self-adjusts the scanner on-the-fly based on tissue density and can reduce the dose up to 60 percent. “Built-in detectors measure the X-ray energy on the opposite side of the patient,” said Wheeler, “and adjust the dose instantly if appropriate.”

Another feature, adaptive dose shielding, moves a mechanical shield of lead within the machine to limit radiation exposure up to 30 percent.

MidMichigan’s 128-slice CT scanner was purchased in 2007. “We continually look at updating existing equipment as new technology is made available,” said Zapolski. “A CT scanner is replaced every five to seven years, depending on improvements available in the marketplace.”
MidMichigan Medical Center - Gratiot, an affiliate of MidMichigan Health, also recently added the 128-slice CT scanner to its line of advanced imaging technology earlier this year.

Good sense
“It’s certainly good sense to limit exposure to radiation sources you can control,” said Radiation Physicist Larry Langrill, radiation safety officer for the Medical Center in Midland. “We also need some idea of the sizes of medical radiation exposures.”

According to Larry Crowley, radiation protection supervisor at MidMichigan Medical Center - Midland, we receive small amounts of radiation from natural sources every day. “This is called ‘background’ radiation, and includes sources such as cosmic radiation from space, radon pockets in the ground and trace amounts of natural radioactivity that exists in buildings, food and our bodies. Today’s chest X-ray, a very low-dose study, delivers about the same dose as five to 10 days of daily background radiation. The CT scan, a higher-dose study, delivers several hundred times the dose of a chest X-ray.” 

Langrill added, “The highest medical radiation doses are delivered in radiation therapy. These doses are equivalent to several thousand CT scans. Still, it’s reasonable to be aware of the number of CT scans you have had. At this point, we have no tracking system for a person’s total radiation dose from diagnostic imaging studies. Talk to your doctor about what benefits they expect from a CT scan, and if you’re concerned, ask about other choices. CT imaging is a valuable diagnostic tool, and the radiation risk is lower than the risk of foregoing the scan and missing the diagnosis.” 

“As someone who understands the technology, I know if I’m sick or my mom’s sick, and a CT scan can help the situation, I would want to have one. The best approach is to use good judgment and get the procedures done that need to be done,” concluded Wheeler.

Those who would like a physician referral may visit www.midmichigan.org/doctors or call MidMichigan Health Line at (989) 837-9090 in Midland or toll-free at (800) 999-3199.