(NaturalNews) The FDA has launched an investigation into how patients at several different hospitals were exposed to as much as eight times more radiation than they were supposed to receive while undergoing computed tomography (CT) scans of their brains.The scans, known as CT perfusion, already expose patients to more radiation than regular CT scans. Patients are injected with an iodine solution, then their heads are exposed to a rapid series of X-rays to create a picture of how blood flows through their brains. The scans are most often used to diagnose strokes, but can also be given in the chest as a way of examining blood flow through the heart.An estimated 150,000 of the brain scans are performed in the United States every year.The problem first emerged in August, when Cedars-Sinai Medical Center in Los Angeles discovered that more than 200 of its patients had been accidentally exposed to radiation levels eight times higher than were supposed to be used in the tests. It took 18 months after the first of the overdose scans was performed for the hospital to discover the problem, even though some of the patients had suffered from skin redness and hair loss as a result of the procedure.It is unknown exactly what the long-term effects of such radiation exposure will be, but it definitely raises the patients' risk of cancer and other chronic diseases. Because such problems can take decades to develop, however, the victims may never be able to directly link them to the botched CT scans The FDA responded to the Cedars-Sinai announcement by launching an investigation into every facility in L.A. County that offers CT perfusion scans. After several months, the agency announced that 50 more cases had been uncovered at Cedars Sinai, and that similar errors had also occurred at two other L.A. County locations.One case was also identified in Alabama, in which 59-year-old Becky Coudert received an even higher radiation dose than the Cedars-Sinai patients. Coudert was given a CT brain perfusion scan to determine if she had suffered from a stroke, and over the next few weeks lost all the hair above her ears.While the overdoses occurred with General Electric CT machines at three of the four institutions in question, the errors at Providence Saint Joseph Medical Center in California were made with a Toshiba machine. This decreases the likelihood that the problems were caused by an equipment malfunction, though it does not rule it out."Given the fact that we are dealing with two manufacturers and multiple institutions, we wouldn't be surprised" to find problems elsewhere, said Dr. Jeffrey Shuren, acting director of the FDA Center for Devices and Radiological Health.Shuren said the agency is still working to determine if the errors were mechanical or human in nature.At two of the facilities, the errors occurred after the hospitals switched over to a new set of computer instructions for the CT perfusion machines. A GE technician reprogrammed the machines at one hospital , but investigators have been unable to find out who made the changes at the other.The FDA has issued new guidelines to prevent such errors from occurring again. The recommended measures include a review of all CT perfusion scan protocols, and that hospital technicians be retrained to double-check the radiation dose to be delivered before beginning the test."While we do not know yet the full scope of the concern, facilities should take reasonable steps to double-check their approach to CT perfusion studies and take special care with these imaging tests," Shuren said.A number of the hospitals involved have either adopted the FDA guidelines or implemented similar policies of their own.Sources for this story include: www.reuters.com;