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Improving Health Through Medical Physics

AAPM Response to the FDA Alert on Radiation Overexposures from CT Brain Perfusion Scans.

October 20, 2009

The FDA Alert in regards to “radiation overexposures” from computed tomography (CT) perfusion imaging procedures for the evaluation of stroke at one facility in Los Angeles raises an important, if not obvious, issue – that medical practitioners who operate or request CT scans for diagnostic evaluation of patients need to know the risks and benefits of CT imaging.  This event also points to the need for a qualified medical physicist to actively participate in the development of CT imaging protocols, especially those involving lengthy and/or repeated scanning sessions (such as brain perfusion) which can lead to relatively high radiation doses to patients, so that radiation levels can be ascertained and minimized.

The facts surrounding the specific CT “radiation overexposure” incidents in Los Angeles have not been released in detail, and therefore it is premature at this point to comment in depth about this particular situation.  However, it should be noted that erythema (skin reddening) and epilation (hair loss) can and do result from radiation dose delivered during other procedures such as cardiac catheterization, and thus the caution surrounding the use of ionizing radiation in medical imaging should not be limited to computed tomography.  Medical imaging procedures are requested by physicians in the care of their patients, in very much the same way that prescription medicines are ordered.  Just as a physician should be aware of the consequences (side effects) of the drugs they order for their patients, all physicians who directly use or request the use of imaging procedures which can result in high radiation doses should be aware of their potential side effects.

Stroke is a serious illness with profound mortality and morbidity consequences, and usually strikes an older population. CT perfusion examinations for the evaluation of stroke and response to therapy is a standard of care procedure, and with the correct team of knowledgeable professionals, including the radiologist, neurosurgeon, medical physicist, and CT technologist, can provide potentially lifesaving diagnostic information at reasonable radiation dose levels.  When appropriately ordered and performed, the benefits to patients can far outweigh the risks.

AAPM Science Council