Laser speckle spatiotemporal variance analysis for noninvasive widefield measurements of blood pulsation and pulse rate on a camera‐phone. Issue 11 (23rd April 2015) - Remer, Itay
Abstract : Photoplethysmography is a well‐established technique for the noninvasive measurement of blood pulsation. However, photoplethysmographic devices typically need to be in contact with the surface of the tissue and provide data from a single contact point. Extensions of conventional photoplethysmography to measurements over a wide field‐of‐view exist, but require advanced signal processing due to the low signal‐to‐noise‐ratio of the photoplethysmograms. Here, we present a noncontact method based on temporal sampling of time‐integrated speckle using a camera‐phone for noninvasive, widefield measurements of physiological parameters across the human fingertip including blood pulsation and resting heart‐rate frequency. The results show that precise estimation of these parameters with high spatial resolution is enabled by measuring the local temporal variation of speckle patterns of backscattered light from subcutaneous skin, thereby opening up the possibility for accurate high resolution blood pulsation imaging on a camera‐phone.Camera‐phone laser speckle imager along with measured relative blood perfusion maps of a fingertip showing skin perfusion response to a pulse pressure applied to the upper arm. The figure is for illustration only; the imager was stabilized on a stand throughout the experiments. Abstract : Laser speckle imaging (LSI) is a well‐established noncontact technique for widefield, high spatial resolution imaging of tissue blood perfusion via temporal analysis of time‐integrated speckle. Here, precise, widefield estimation of blood pulsation and heart‐rate frequency is shown by measuring local temporal variations of speckle patterns of light backscattered from subcutaneous skin. The LSI instrument is realized using a camera‐phone, demonstrating the potential of LSI‐based functional imaging with a simple imager.