Dose reduction initiative gains strength among vendors

October 17, 2001

Prompted in equal parts by research, regulation, and public relations, medical imaging vendors are responding to concerns about radiation risk by patients and staff. Some companies have launched new exposure control products or incorporated lower dose

Prompted in equal parts by research, regulation, and public relations, medical imaging vendors are responding to concerns about radiation risk by patients and staff. Some companies have launched new exposure control products or incorporated lower dose capability into imaging devices. Others have embarked on education and marketing campaigns that emphase radiation safety.

“We have a responsibility to physicians and staff who are working long hours to take care of patients,” said Lynne Groves, surgery product manager at Siemens Medical Solutions. “Some people say that dose doesn’t matter, so long as a good image is the result. But you have to make sure you don’t compromise anybody.”

Dose reduction has become a hot topic for several reasons. The first is a highly publicized study this spring linking cancer mortality risk to radiation exposure in children undergoing CT exams. That revelation sparked debate about how to maximize the benefits of medical imaging while minimizing dose, particularly in pediatrics.

Then the FDA issued a warning that annual lung cancer screening with low-dose CT could result in unnecessary radiation. Coupled with the report on pediatric risk, the regulatory notice spurred vendors to act. Several manufacturers, including GE Medical Systems, have sponsored educational forums on pediatric CT dose reduction. Toshiba America Medical Systems has introduced Real EC, an automatic exposure control that reduces radiation dose by up to 40%.

Concerns about patient exposure to radiation cut across all segments of the industry, including the radiography and fluoroscopy markets. Engineers have long recognized the need to increase efficiency, according to Walter Schneider, president of Del Medical Imaging Systems in Franklin Park, IL.

“We’ve seen a swing toward high-frequency systems over the past five years, and it is continuing,” he said. “These are much more efficient than the older, single-phase systems.”

Siemens is marketing the lower dose capability of its new mobile C-arm device, the Iso-C 3-D. The company also markets Care Graph, a software package introduced in 1994 that generates a warning when patient dose reaches a critical threshold.

Digital radiography equipment has created a new thread in the debate, which revolves around the role of detective quantum efficiency (DQE) and dose. Most digital systems are measured by a combination of resolution, dynamic range, and DQE. The higher the DQE, the more flexibility when it comes to patient dose, said Robin Winsor, developer of charge-coupled device–based detector technology for Imaging Dynamic’s digital radiography systems.

Some vendors try to achieve the highest possible DQE. But this may come at the expense of other quality parameters, such as resolution and dynamic range. Other companies, like Imaging Dynamics, have opted to simply match the dose efficiency of plain film-a standard long established as a benchmark.

“There’s a big debate going on in digital radiography over whether we should be striving for better dose efficiency,” Winsor said. “Some folks will tell you that DQE is the critical image quality measure. But where you want that DQE to be after it matches and passes the DQE of film is an academic debate. No one is going to lower the dose so much that they compromise image quality.”

These compromises could technically be made, however. Digital radiography systems offer essentially linear controls that allow dose and image quality trade-offs to be dialed in. Operators can choose high, middle, or low dose prior to capturing images with no built-in safeguards to ensure minimum image quality.

“If you crank it down too far, as was the trend some years ago in film imaging, you’ll get a grainy, noisy digital image,” Winsor said. “It’s a matter of common sense.”

The RSNA hopes to impart or at least underscore some of that common sense through seven scientific sessions on safety-related topics to be conducted at its November meeting. How many vendors will jump aboard the dose reduction bandwagon with campaigns on the exhibit floor remains to be seen. But Groves at Siemens is convinced that vendors need to take responsibility for educating users about dose and radiation risks.

“Users should take regular steps for radiation protection, but it doesn’t always happen,” she said. “We’re being responsible in taking that step through equipment design.”