A recent series of radiation overdose incidents in CT brain perfusion exams were likely due to improper use of CT systems, according to the U.S. Food and Drug Administration (FDA). Earlier this week, the agency announced the results of its investigation into these incidents, noting that they were “most likely” caused by human error rather than by scanner malfunction. The investigation, which began in October 2009, also revealed that at least 385 patients had received excessive radiation from CT brain perfusion scans performed at five hospitals in California and one in Alabama to confirm the presence of stroke.
In making the announcement, the FDA revealed plans to hold follow-up discussions with manufacturers about how equipment and training might be altered to increase the safety of CT scans, specifically CT brain perfusion scans. These discussions will be part of its “Initiative to Reduce Unnecessary Radiation Exposure from Medical Imaging”, which covers x-ray fluoroscopy as well as CT.
The agency also sent a letter to the Medical Imaging and Technology Alliance (MITA), wherein it detailed both the results of its investigation and possible equipment modifications. Proposed changes encompass the addition of console notifications that would alert CT system operators should a patient receive a high radiation dose, as well as the provision of information on training and brain perfusion protocols to all facilities that receive base CT equipment, whether or not such facilities purchase additional software that enables quantitative analysis of cerebral hemodynamics.
Other potential alterations specified in the letter encompass the clarification of imaging parameters that affect dose, along with instructions on how to appropriately set them; and the organization of all dose-related information in either a single section of each CT scanner user manual, a dedicated dose manual, or fully indexed in a concordance covering all manuals.
Jeffrey Shuren, MD, director of FDA’s Center For Devices and Radiological Health, said the changes are intended to prevent the kind of errors the FDA believes have exposed hundreds of patients to toxic levels of radiation, and that the equipment enhancements described in the letter to MITA have significant potential to minimize the chance of radiation overdose . "Patients should not have to worry that a device designed to diagnose an illness exposes them to unnecessary risks," he asserted in a statement issued when the investigation results were released.
Meanwhile, MITA has clearly stated its intention to continue working with the FDA, as well as with its member manufacturers, users, and regulators, to reduce radiation levels. "The recommendations in the FDA's letter are issues we have been working on with the agency over the past year and include an important component of our CT Dose Check Initiative,” Dave Fisher, MITA’s executive director, asserted in an interview. "The reported incidents have not been attributed to CT scanner malfunction, but as part of our longstanding commitment to educating users and to developing technologies that reduce radiation levels, MITA looks forward to continuing our work with the FDA. In the end, the optimal solution will require action by all stakeholders, including, manufacturers, users and regulators."
The FDA initiated the investigation, which included the examination of CT perfusion systems from several manufacturers, following reports of a series of CT radiation overdoses at Cedars-Sinai Medical Center in Los Angeles. In addition to Cedars-Sinai, a number of other hospitals in the U.S. reported that patients had received radiation overdoses. In many cases, imaging facilities were unaware of the incidents until after patients who had already been discharged began experiencing side effects from radiation. In March 2010, the agency convened a series of hearings to discuss ways to make CT brain perfusion scans safer, in particular by requiring scanner manufacturers to incorporate design changes into their products that enable radiology professionals to see how much dose has been delivered during a procedure.