A doctor looks at a screen and sees two images of the same part of the body. One shows where blood is rich in oxygen, the other shows how fast it rushes through the finest vessels. Previously, these images were made by different devices, and combining them was difficult. Now engineers have built a device that takes both images simultaneously.
Inside the device is a flat plate with many tiny ultrasound transducers, like a honeycomb of microphones. It sends out inaudible sound waves and catches their reflections. One mode makes blood 'sound' under a beam of light and calculates oxygen from that sound. The other mode tracks marker bubbles in the blood and maps the flow based on their movement.
The device was tested on glass tubes with artificial blood and then on live mice. It measured oxygen saturation from sixty to ninety-five percent with an error of only five percent. And it needed just five flashes of light of different colors, not dozens as before.
For now, the method has a weakness: because the transducer is flat, some vessels remain in shadow, like an object behind a flashlight. But even with this shadow, the device already helps study how blood delivers oxygen to the brain, kidneys, and tumors. The next step is to reduce the shadow and apply the device to humans.
The ultrasound that the device hears is a hundred times higher in frequency than a mosquito's buzz. The human ear cannot perceive it, but the sensor can detect blood movement in a vessel thinner than a hair.