CT Perfusion Dose – What is all the Hue and Cry About?

Last year a New York Times investigation uncovered more than 200 radiation overdose cases at Cedars-Sinai Medical Center. According to a New York Times follow-up published on July 31 this year, 200 additional cases were revealed at other hospitals leading to more than 400 cases nationwide. The radiation overdose delivered to patients in these overdose cases was between 4 to 13 times higher than a typical dose for the performed scans. These overdoses led patients to experience hair loss, headaches, confusion, and may increase their long-term risk of cancer and possible eye and brain damage. The patients had received CT brain perfusion exams, which help to identify strokes through a number of blood flow images.

Why did these overdoses happen?  This could be due to equipment malfunction, the need for “prettier” clinical images (requiring high radiation dose), or a serious lack of operator knowledge in setting up the CT imaging protocols for this type of exam. CT brain perfusion is a high-dose exam but can be performed safely if the technologists, physicists and radiologists work diligently together to ensure that the CT imaging protocols are set up optimally to follow the As Low As Reasonably Achievable (ALARA) principle. The dose delivered by this exam should also be monitored on a regular basis to ensure it remains at minimal levels and no equipment malfunction or dose creep has occurred.  Physicians should also be aware of the potential side effects, as discussed above, which can be triggered by such high-dose exams.

Following 2009’s overdose discoveries, the FDA launched a collaborative Initiative to Reduce Unnecessary Radiation Exposure from Medical Imaging, to promote the safe use of medical imaging devices, support informed clinical decision making, increase patient awareness, and optimize patient exposure to radiation.

At the recent American Association of Physicists in Medicine (AAPM) annual meeting, the patient safety symposium focused on these overdose cases and the AAPM CT dose summit’s recent efforts to ensure CT scan parameter optimization and patient safety.  The AAPM also produces reports on quality and safety in medical imaging and radiotherapy, along with letter-writing and policy campaigns targeted at the government and public.

Researchers at Mayo Clinic are also investigating the use of new image-processing algorithms to reduce the dose for CT perfusion exams up to 95 percent and maintain the same image quality as a high-dose perfusion exam.

If appropriate steps are taken to ensure patient safety and dose optimization, the benefits from a CT brain perfusion scan far outweigh the risks associated with it.

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