October 10, 2009 — The US Food and Drug Administration (FDA) is reporting cases of radiation overexposures during brain perfusion computed tomography (CT) imaging. The overexposures took place at a single institution but may reflect a more widespread problem regarding CT quality assurance programs.
During an 18-month period, the agency found that 206 patients received radiation doses that were approximately 8 times the expected level.
According to an alert sent yesterday from MedWatch, the FDA's safety information and adverse event reporting program, "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."
Patients received 3 to 4 Gy instead of the expected 0.5 Gy (maximum) to the head, the FDA notes. "In some cases, this excessive dose resulted in hair loss and erythema."
The FDA is encouraging facilities that use CT imaging to monitor the dose indices displayed on the control panel, including the volume computed tomography dose index (in units of mGy) and the dose-length product (in units of mGy-cm). Values displayed should be within the range normally used with the protocol. Values should be confirmed again after the patient has undergone the procedure.
Clinicians suspecting reportable adverse events associated with CT devices should follow the reporting procedure established by their facility.
The FDA is collecting more data on this issue and will provide this information as it becomes available.
More information is available on the FDA's MedWatch Web site.
Suspected radiation overexposure after CT should be communicated to the FDA's MedWatch reporting program by telephone at 1-800-FDA-1088, by fax at 1-800-FDA-0178, online at http://www.fda.gov/medwatch, or by mail to 5600 Fishers Lane, Rockville, Maryland 20852-9787.
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