Smartphone imaging of subcutaneous veins

The identification of veins by medical personnel is a critical skill that is necessary to draw blood or administer intravenous fluids and medications. Because a normal consumer camera can act as a multispectral imaging apparatus, operating with three broadband detectors, we hypothesized that a standard smartphone camera might be employed for enhanced visualization of veins in human skin.

Video and images of subcutaneous veins were acquired using the rear-facing iSight camera from an iPhone 6, with a fixed aperture of f/2.2, and Sony Exmor RS back-illuminated CMOS image sensor with pixel generation of 1.5 microns. A custom program was written for the iOS operating system that performs a scaled matrix subtraction of different spectral channels and displays results as a grayscale image.

A scaled subtraction of green channel pixel values from red channel pixel values enabled greatly improved identification of subcutaneous veins. Wavelengths of light at which the green detector is most sensitive (520-580 nm) correspond to local absorption maxima of both oxyhemoglobin (542 and 576 nm) and deoxyhemoglobin (556 nm); consequently, the algorithm obtained images of light transport weighted toward deeper skin layers.

We identified and developed a simple algorithm by which a standard smartphone camera can be employed for enhanced video-rate visualization of veins in human skin. Lasers Surg. Med. 50:1034-1039, 2018. © 2018 Wiley Periodicals, Inc.