AI-driven mobile health algorithm uses phone camera to detect blood vessel oxygen levels

June 8, 2023
A smartphone camera paired with an AI-driven algorithm can capture blood oxygen data faster and more efficiently than highly specialized equipment.

You may already use your smartphone for remote medical appointments. Why not use some of the onboard sensors to gather medical data? That’s the idea behind AI-driven technology developed at Purdue University that could use a smartphone camera to detect and diagnose medical conditions like anemia faster and more accurately than highly specialized medical equipment being developed for the task.

By pairing deep learning and statistical techniques with their knowledge of light-tissue interactions, Purdue researchers are able to reconstruct the full spectrum of visible light in each pixel of an ordinary smartphone camera image. The patent-pending approach, from a lab with expertise in mobile health, could improve access to healthcare.

As reported in PNAS Nexus, the team tested its method against commercially available hyperspectral imaging equipment when gathering information about the movement of blood oxygen in volunteers’ eyelids, in models meant to mimic human tissue, and in a chick embryo. Results show the smartphone camera produced hyperspectral information more quickly, more cheaply and just as accurately as those captured using specialized equipment. The smartphone approach can produce images in a single millisecond that would take conventional hyperspectral imaging three minutes to capture.

Lead researcher Young Kim said the work reported in PNAS Nexus focused on building the smartphone hyperspectral imaging algorithm rather than specific applications. But in other studies, the team has used its approach to measure blood hemoglobin for tissue oximetry and inflammation. Kim’s lab used a computational approach that the researchers have dubbed “hyperspectral learning.” 

The process begins with a smartphone camera on an ultra-slow-motion setting that produces video at about 1,000 frames per second. Each pixel in each frame contains information for red, green and blue color intensity. The information is fed through a machine learning algorithm that infers full-spectrum information for each pixel. That is used to produce the measurements of blood flow, particularly of the amount of oxygenated and deoxygenated hemoglobin in each pixel. These hemodynamic parameters can also be used to produce images and video that show oxygen saturation in their subjects over time. 

As with conventional machine learning, the team trains its algorithms on a data set, feeding it smartphone images and the corresponding hyperspectral images and fine-tuning the algorithm until it can predict the correct relationship between the two data sets. But by building the algorithms with equations derived from tissue optics – an approach sometimes called “informed learning” – the researchers require a far smaller training data set.

And whereas conventional hyperspectral imaging equipment must gather massive amounts of data, limiting either the spectral resolution or temporal resolution, the team’s approach begins with video files that are hundreds of times smaller than hyperspectral imaging files, allowing them to maintain a high standard on both fronts.

Purdue release