Believed to have been coined by William Shakespeare, the phrase “in the pink of health” refers to the rosy glow of the cheeks—commonly perceived as a mark of a healthy disposition. Interestingly, today’s science backs up this age-old notion: functional changes to the tiny blood vessels just beneath the surface of the skin have been linked to serious conditions such as vascular and inflammatory skin diseases.
These findings have spurred the development of diagnostic technologies that use skin as a barometer for health. For example, pulse oximeters clipped on to the fingertip (used extensively during the pandemic) gauge a person’s blood oxygen levels. Accurate measurements of the skin microcirculation could also be used to alert to conditions from infections and inflammation to diabetes and heart disease.
However, most existing methods for measuring the microcirculation remain unreliable and expensive, a problem that Malini Olivo, Director of Biophotonics at A*STAR’s Institute of Bioengineering and Bioimaging (IBB), hopes to change by “listening” to the skin.
“When exposed to a pulsing laser light, human tissues heat up slightly, emitting faint acoustic waves. Through the detection of these waves, we can interrogate deeper into tissues as compared with using conventional methods that detect light signals,” explained Olivo, referring to a technique known as optoacoustic imaging, or OAI.
The team employed a specialised technique known as multispectral raster-scanning optoacoustic mesoscopy (ms-RSOM)—a first-of-its-kind OAI that takes high-resolution images at millimetre depths beneath the surface of the skin. The researchers then validated the technology on a cohort of six healthy participants, through collaborations with the National Skin Centre.
Using a blood pressure cuff to simulate blood flow changes caused by various illnesses, the researchers captured images before, during and after cuff compression. The team found that ms-RSOM accurately captured even subtle physiological changes in the microcirculation across different stages of occlusion.
This is the first demonstration that ms-RSOM can accurately track disruptions to the flow of oxygenated and deoxygenated blood within the vessels, which Olivo describes as a “window of opportunity” for clinicians to non-invasively diagnose and monitor conditions associated with vascular remodelling.
Still, the current ms-RSOM iteration is not without its limitations. “Currently, the system can only image up to two millimetres below the skin and image quality is often affected by skin pigmentation,” said Olivo, whose team has their sights set on a next-generation system with brighter lights and more sensitive acoustic signal collection to improve the quality of data collected.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Bioengineering and Bioimaging (IBB).