Reports have reached the FDA (Food and Drug Administration) of CT brain perfusion scans which exposed patients to excessive levels of radiation. After checking the equipment, the FDA reports they were working fine, without any excessive radiation risk for the patients “when properly used”. The agency is convinced patients were exposed to radiation overdose because the devices were not being used correctly. It says it has identified a series of steps which would make sure CT scans are performed safely. These steps would reduce the risk of radiation overdosing even if the scanners were improperly used.
A CT scan or Computed Tomography scan, is also known as a CAT (Computer Axial Tomography) scan. Tomography generates a two-dimensional image of a section through a 3-dimensional object (tomogram). The machine is called a CTG scanner; it is a large device which uses X-rays. The scanner’s 3-D image is made after several 2-dimensional X-ray images are taken around a single axis of rotation.
Put simply, the device takes many pictures of the same area from different angles, and then places them together to produce a 3-dimensional image.
The FDA has written to several radiological imaging device organizations, including the Medical Imaging Technology Alliance, explaining the findings of its investigation as well as suggesting enhancements which could better ensure safety for the patient. The FDA adds that follow-up discussions on this matter are currently being planned.
The FDA has put forward the following steps to improve safety:
- A notification in the console reminding the operator of high radiation dosages.
- The provision of specific information and training on brain-perfusion procedures for all places that use these devices, regardless of whether the facilities bought the related software enabling quantitative analysis of cerebral hemodynamics.
- Clear explanation on dosage parameters, including clear and comprehensible instructions on how to set those parameters properly.
- User manuals should have all information related to dosage in one section, in a dedicated dose manual, or indexed comprehensively in a concordance covering all manuals.
A CT brain perfusion scan allows the doctor to look at blood flow in the brain in detail. Physicians may order this type of scan to confirm a diagnosis of stroke, for example.
The FDA discussed its findings today from an investigation into radiation overdoses among individuals receiving CT brain perfusion scans in Alabama and California hospitals. The probe started in 2009, and includes data on radiation overdoses from October 2008 to 2010. CT scanner equipment manufacturers were also inspected.
The investigation concluded that when used correctly, these devices did not pose a radiation overdose risk for patients. The investigators did, however, uncover potential improvements to CT devices that could significantly lower overdose risk if the equipment is used incorrectly.
Jeffrey Shuren, M.D., director of FDA’s Center for Devices and Radiological Health, said:
Improving patient safety is part of our public health mission. Patients should not have to worry that a device designed to diagnose an illness exposes them to unnecessary risks.
The FDA says it knows about 385 cases of patients receiving excessive amounts of radiation from CT brain perfusions scans in six hospitals, five in California and one in Alabama.
The FDA stresses that the benefits provided by CT scans far outweigh the risks.
In a communiqué, the Medical Imaging Technology Alliance (MITA) wrote:
MITA is pleased that the FDA investigation found no violations of FDA laws and regulations by manufacturers and that the when the scanners were used according to the manufacturers’ specifications, they did not result in overexposure. Also, MITA agrees with the FDA that manufacturer-defined protocols provide “reasonable and appropriate image quality and dose.
MITA supports the FDA’s advocacy for two principles of radiation protection: appropriate justification for ordering each procedure, and careful optimization of the radiation dose used during each procedure. As part of our commitment to patient safety, MITA and its members are committed to working with the FDA on MITA’s Dose Check Initiative and the FDA’s recommendations. We agree wholeheartedly with the FDA that each patient should get the right imaging exam, at the right time, with the right radiation dose.
FDA
Written by Christian Nordqvist