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  1. Letters to Health Care Providers

Intended Use of Imaging Software for Intracranial Large Vessel Occlusion - Letter to Health Care Providers

April 11, 2022

The U.S. Food and Drug Administration (FDA) is reminding health care providers about the intended use of radiological computer-aided triage and notification (CADt) devices for intracranial large vessel occlusion (LVO). LVO is an obstruction of one of the large arteries in the brain and is a common cause of acute ischemic strokes. LVO CADt devices are software devices intended to aid in prioritization and triage of time-sensitive suspected findings of LVO based on the analysis of radiological exams of the brain. LVO CADt devices do not provide diagnostic information or remove any cases from the imaging physician’s reading queue. Information from real-world use suggests that providers may not be aware of the intended use of these devices. If LVO CADt devices are not used as intended, there is the potential for misdiagnosis resulting in patient injury or death. The FDA is bringing this information to your attention as a reminder and to ensure that providers are aware of the intended use of the software as a triage and prioritization tool.

Recommendations

The FDA recommends that health care providers:  

  • Be aware that LVO CADt devices only flag radiological exams with suspected findings and should never be used as a replacement for informed interpretation by an imaging physician.
  • Recognize that LVO CADt devices cannot rule out the presence of an LVO. If a radiological exam is not flagged by a LVO CADt device, an LVO may still be present.
  • Recognize that when the device is used as intended (as a prioritization and triage tool and not a diagnostic device), it can improve workflow by prioritizing suspected cases. 
  • Recognize that the device does not remove any radiological exams from the queue for interpretation by an imaging physician. When used as intended, exams that are not flagged by the device are still interpreted by an imaging physician according to the standard of care.
  • Be aware of the design of LVO CADt devices. This includes an understanding of the vessels (arteries) for which the device was designed and tested to detect LVO. LVO CADt devices may not be designed and tested to evaluate all intracranial vessels. If you have questions about which vessels the LVO CADt device is designed to evaluate, or are unsure, review the most recent product labeling or contact the device manufacturer for further information or questions on device performance.

Background

Acute ischemic stroke caused by LVO contributes to stroke-related disability and death. Timely intervention may improve health outcomes. Many CADt devices are based on artificial intelligence and machine learning (AI/ML) technology. LVO CADt devices are classified under 21 CFR 892.2080 Radiological computer-assisted triage and notification software (eCFR :: 21 CFR 892.2080 -- Radiological computer aided triage and notification software). 

Health care providers may not be fully aware that LVO CADt devices are intended for prioritization and triage only. These devices should not be relied on when making any diagnostic decisions. In addition, health care providers should ensure that they understand which vessels the device was designed and tested to evaluate. If the device is used for diagnostic decisions or to evaluate vessels for which it was not designed, delayed or missed diagnoses may occur and result in worsened outcomes for patients. When used as intended, CADt devices can improve the workflow by prioritizing suspected exams. The device does not remove any radiological exams from the queue for interpretation by an imaging physician. When used as intended, exams that are not flagged by the device are still interpreted by an imaging physician according to the standard of care. 

FDA Actions

The FDA is working with LVO CADt device manufacturers to ensure that health care providers are informed about the intended use and design of these devices. More generally, because postmarket performance in clinical practice may not match the premarket data, the FDA is also engaged in continuing efforts to evaluate the real-world performance of AI/ML imaging devices, including CADt devices. The FDA will continue to keep health care providers and the public informed if new or additional information becomes available. 

Reporting Problems to the FDA

The FDA encourages health care providers to report any adverse events or suspected adverse events experienced with imaging software for LVO. 

Prompt reporting of adverse events can help the FDA identify and better understand the risks associated with medical devices.

Contact Information

If you have questions about this letter, contact the Division of Industry and Consumer Education (DICE):

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