LASCA and PPG imaging for non-contact assessment of skin blood supply

Laser speckle contrast analysis (LASCA) offers a non-contact, full-field, and real-time mapping of capillary blood flow and can be considered as an alternative method to Laser Doppler perfusion imaging (LDPI). Photoplethysmography (PPG) is well known technique for assessment of skin blood pulsations that can be related to blood flow. In recent years several studies have been done on development of non-contact PPG imaging (PPGI). LASCA and PPGI techniques are simpler and cheaper compared with LDPI. LASCA technique has been implemented in several commercial instruments. However, these systems are still too expensive and bulky to be widely available. Several optical techniques have found new implementations as connection kits for mobile phones thus offering low cost screening device. In this work we demonstrate simple implementation of LASCA and PPG imaging technique for primary low-cost assessment of skin blood flow. Both devices comprise a widely available 1.3 mega pixel CMOS camera. Stabilized 650 nm laser diode module is used for LASCA illumination, and white LEDs are illuminators for PPG imaging device. An arterial occlusion test was performed to test LASCA and PPGI imaging devices. An example of scratch color image and corresponding blood flow map also was demonstrated. The results showed that both techniques can be used for fast monitoring and mapping of skin blood flow and implemented as connection kits for smartphone.