A computer-resetting error led to radiation overdoses of 206 patients who underwent CT brain perfusion scans at Cedars-Sinai Medical Center in Los Angeles over the last 18 months, hospital officials said in a statement on Monday. This overexposure has led the FDA to commence a safety investigation into the procedure.

In August, a patient who had previously received a CT brain perfusion scan at Cedars-Sinai contacted the medical center after noticing temporary patchy hair loss. Since this is not a common side-effect from CT brain perfusion scans, the hospital began investigating the equipment involved and the protocols used for CT brain perfusion scans.

“No additional CT brain perfusion scans were done until the investigation was completed,” according to hospital officials.

The hospital said its investigation found that over the 18-month period, 206 patients at Cedars-Sinai received radiation doses that were approximately eight times higher than the expected level. “There was a misunderstanding about an embedded default setting applied by the machine,” according to the written statement. “As a result, the use of this protocol resulted in a higher than expected amount of radiation.”

GE Healthcare, the CT’s manufacturer, said it is cooperating with FDA officials to investigate the CT brain perfusion scan event. However, company representatives noted that “there were no malfunctions or defects in any of the GE Healthcare equipment involved in the incident.”

Although the temporary hair loss or skin-reddening would have occurred within six weeks of the CT brain perfusion scan, the hospital began contacting all 206 patients who had a CT brain perfusion scan between February 2008 and August of this year (the time period when the machine was delivering the higher dose).

Cedars-Sinai reported its findings to the California Department of Public Health, and continues to keep regulatory agencies informed. Due to its investigation, the medical center also said it has instituted additional double-checks in its operations of the scanner and additional equipment protocols to ensure that this does not happen again.