Radiation overdoses linked to scanner error

Los Angeles: Scores of radiation overdoses at Cedars-Sinai Medical Centre have been traced to a single cause: a mistake the hospital made resetting a CT scanner.

Hospital officials said on Monday that the error occurred in February 2008, when the radiology department began using a new protocol for a specialised type of scan used to diagnose strokes. Doctors believed it would provide more useful data to analyse disruptions in the flow of blood to brain tissue.

That meant resetting the machine to override the instructions that came with the scanner when it was installed.

"There was a misunderstanding about an embedded default setting applied by the machine ... ," hospital officials said in a statement that provided no other details about how the error occurred.

"As a result, the use of this protocol resulted in a higher than expected amount of radiation."

The dose of radiation was eight times what it should have been.

Reset error

Once the scanner was programmed with the new instructions, the higher dose was essentially locked in. Each patient who underwent the procedure — known as a CT brain perfusion scan — was subjected to the overdose. The machine was used for other types of scans but the reset error affected only the potential stroke patients, said Richard Elbaum, a hospital spokesman.

The error went unnoticed for the next 18 months, until a stroke patient informed the hospital he had begun losing his hair after a scan.

When the hospital reviewed its records, it found — and contacted — 206 people who had received the overdoses to inform them of the mistake. Only then, Elbaum said, did the hospital learn that about 40 per cent of them had suffered patchy hair loss. Many also experienced reddening of the skin.

A CT scan uses a series of X-rays to create a highly detailed image. Possible stroke victims are injected with an iodine solution, which appears in the scans and is used to track blood flow in the brain.

Even under normal circumstances, the procedure requires more radiation than most other types of CT scans, said David Brenner, the director of radiological research at Columbia University Medical Center in New York.

Excess radiation would be difficult to detect from looking at the scan results, he said. More radiation simply produces a clearer image.

Radiation exposure increases the likelihood of cancer, although the risk is lower in older patients because they are likely to die of other causes first. The median age of the patients who received the overdose is 70, said Elbaum, the Cedars-Sinai spokesman.

The discovery of the problem prompted the Food and Drug Administration to issue an alert last week warning hospitals to check their CT protocols.

The statement from Cedars-Sinai said the hospital had received calls from other "advanced hospitals" that were reviewing their own safety procedures.

General Electric, the manufacturer of the scanner, said in a statement that there were "no malfunctions of defects" of the machine.

It said that any new scanning protocol should be evaluated "against the validated protocols that are provided on the scanners during installation."