“Between 2% and 5% of strokes each year occur in people with no symptoms, so better and earlier detection of stroke risk is needed,” said lead study author Hsien-Li Kao (National Taiwan University Hospital, Taipei, Taiwan).
“This was an exciting ‘eureka’ moment for us,” Kao said. “Existing diagnostic methods—ultrasound, CT and MRI—require screening with specialised medical imaging equipment and personnel. Analysis of video recorded on a smartphone is non-invasive and easy to perform, so it may provide an opportunity to increase screening. Though more research and development are needed, the recordings and motion analysis may be able to be implemented remotely, or a downloadable app may even be feasible.”
This study, conducted between 2016 and 2019, used motion magnification and pixel analysis to detect the minute changes in pulse characteristics on the skin’s surface captured in a smartphone video recording.
A group of 202 Taiwanese adults (average age of 68 years; roughly 79% men) who received care at a single Taiwanese hospital participated in the study. Among the participants, 54% had significant carotid artery stenosis, meaning they had at least 50% blockage that was previously diagnosed by ultrasound, while 46% did not have significant stenosis. Recordings were captured with participants laying on their back, with their head tilted back in a custom-made box that minimised outside movement. An Apple iPhone 6, 64GB, was mounted to the box to capture a 30-second video recording of the person’s neck. The older generation phone was used as researchers believed it would be more common to the average user, Kao explained.
Researchers found that the video motion analysis algorithm had an 87% accuracy rate of detecting stenosis in the group known to have carotid artery stenosis. All study participants also had standard Doppler ultrasound testing to confirm narrowing in their arteries and to gauge and validate the estimates from the video motion analysis.
“More research is needed to determine whether video recorded on smartphones is a promising approach to help expedite and increase stroke screening,” Kao said. “Carotid artery stenosis is silent until a stroke happens. With this method, clinicians may be able to record a video of the patient’s neck with a smartphone, upload the videos for analysis and receive a report within five minutes. The early detection of carotid artery stenosis may improve patient outcomes.”
There were several limitations to the study including the small number of study participants, all of whom were considered at high risk for a cardiovascular event. In addition, neck length and neck angle were not analysed, which may affect the results of the video analysis. Skin colour is not likely to hinder applications to a broader population since a standard lighting method was used for this assessment, according to Kao.
The study was funded by the Ministry of Science and Technology in Taiwan.