Reports of stroke patients who were accidentally exposed to eight times the normal radiation dose during diagnostic CT scans at Cedars-Sinai Medical Center in Los Angeles are prompting safety warnings and soul searching among radiologists nationwide.
Over an 18-month period, 206 patients at the center received 3 to 4 Gy to the head instead of the expected 0.5-Gy dose during perfusion CT imaging, according to an FDA investigation.
The problem reportedly resulted from an error made by the hospital in resetting the CT machine after it began using a new protocol for the procedure in Feb. 2008, but it wasn't detected until one of the patients reported patchy hair loss in August 2009.
"There was a misunderstanding about an embedded default setting applied by the machine," according to a statement from Cedars-Sinai.
The FDA warned imaging facilities to review their protocols and carefully monitor the volume CT dose index and dose-length product during and after each patient's scan.
"This situation may reflect more widespread problems with CT quality assurance programs and may not be isolated to this particular facility or this imaging procedure (CT brain perfusion)," the FDA said.
"If patient doses are higher than the expected level, but not high enough to produce obvious signs of radiation injury, the problem may go undetected and unreported, putting patients at increased risk for long-term radiation effects," the safety notification added.
The chairman of Cedars-Sinai's department of imaging, Barry Pressman, MD, said the amount of radiation received by the 206 patients was high, but similar to an exposure they might receive when undergoing a procedure such as angioplasty.
Others were less sanguine.
"To me, even as a professional, this is a fairly shocking story," commented James Slater, MD, of NYU Langone Medical Center in New York City.
The affected patients likely reached their maximum allowable radiation exposure for the entire year in that single test, Slater added.
"The fact that this error occurred and went undetected for 18 months at a well-regarded medical center is rather unbelievable," he said.
The dose the patients received could be expected to yield in the range of a 1% risk of radiation-induced cancer, but only relatively minor skin injury and likely no significant direct injury to the brain, said G. Donald Frey, PhD, of the Medical University of South Carolina in Charleston.
Still, Frey called the Cedars-Sinai situation a serious problem that should have been caught at a regular review of CT scan protocols involving radiologists, the medical physicist, and the technologist.
A statement from Cedars-Sinai said it has added double-checks to the process of changing scan protocols and has been advising other hospitals that have contacted it about the issue.
The California errors highlight an ongoing controversy over patients' increasing exposure to radiation, brought on by phenomenal growth in the number of CT procedures, said Jeff Brinker, MD, of Johns Hopkins.
"Still we have no real means of accounting for the total radiation, in particular medically related, a person receives," he said.
"Since patients go to different doctors and hospitals, no one knows for sure or even keeps account of the total radiation exposure for medically-indicated and research procedures."
This article was developed in collaboration with ABC News. 