Static laser speckle contrast analysis for noninvasive burn diagnosis using a camera-phone imager

Abstract

Abstract. Laser speckle contrast analysis (LASCA) is an established optical technique for accurate widefield visualization of relative blood perfusion when no or minimal scattering from static tissue elements is present, as demonstrated, for example, in LASCA imaging of the exposed cortex. However, when LASCA is applied to diagnosis of burn wounds, light is backscattered from both moving blood and static burn scatterers, and thus the spatial speckle contrast includes both perfusion and nonperfusion components and cannot be straightforwardly associated to blood flow. We extract from speckle contrast images of burn wounds the nonperfusion (static) component and discover that it conveys useful information on the ratio of static-to-dynamic scattering composition of the wound, enabling identification of burns of different depth in a porcine model in vivo within the first 48 h postburn. Our findings suggest that relative changes in the static-to-dynamic scattering composition of burns can dominate relative changes in blood flow for burns of different severity. Unlike conventional LASCA systems that employ scientific or industrial-grade cameras, our LASCA system is realized here using a camera phone, showing the potential to enable LASCA-based burn diagnosis with a simple imager. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

In vivo burn diagnosis by camera-phone diffuse reflectance laser speckle detection

“…The experiment was in compliance with protocols approved by the National Animal Care and Use Committee (#IL-13-05-098) and was conducted in agreement with the Guide for the Care and Use of Laboratory Animals at the Lahav C.R.O research unit (Kibbutz Lahav, Israel). Full details of the experiment are described in our previous publication [11]. In short, one female pig (~2 months old, body weight of 33 kg) was individually acclimated to housing facilities for 5 days before use.…”

“…Four groups of 12 burns were inflicted, each with a different probe-skin contact time of 10, 20, 30, and 40 s, resulting in a total of 48 burn sites (see Fig. 2(a) in [11]). Temperature was monitored using a thermocouple threaded into the bottom of the block.…”

“…In particular, we implement a spatiotemporal fluctuation analysis scheme based on the processing scheme proposed by Sadhwani et al [15] to extract the diameter of the speckle spot, and show that the retrieved diameter agrees well with the thickness of porcine burns of graded severity, enabling not only early discrimination of partial-thickness burns (within the first 24 hpb), but also longitudinal monitoring of the burn healing process (over 104 hpb). Unlike the system devised by Sadhwani et al and other instruments for diffuse reflectance laser speckle detection using scientific-or industrial-grade cameras [15][16][17][18], our apparatus takes advantage of advancements of miniature-camera technology in biomedical sciences [11,13,14,19,20] and employs a camera-phone for diffuse reflectance speckle detection. While the basic setup used here is similar to that of oblique incidence reflectometry (OIR) [21,22], we analyze spatial intensity variations in diffuse reflectance laser speckle patterns rather than OIR distances between the diffusion center and illumination entry point.…”

“…From this image, a color-coded map that conveys information on burn severity is rapidly generated over a large field-of-view without any scanning by calculating the speckle contrast as the ratio of the standard deviation to the mean speckle intensity over a local sliding window [12]. Recently, LASCA has been shown to provide early assessment of burn severity in a porcine burn model in vivo using a scientific-grade camera [10] and a simple imager comprising a camera-phone [11]. It is worth mentioning that cameraphone-based LASCA imaging has also been demonstrated useful for noninvasive widefield measurements of skin perfusion, blood pulsation and pulse rate [13,14].…”

“…LDI is considered to be a valid measure of burn depth and exhibits high correlation with burn wound histology; yet, current commercially-available laser Doppler imagers are relatively large, require a prolong scanning time, and are not promoted for early diagnosis during the first 48 hours postburn (hpb) [4,7,8]. Laser speckle contrast analysis (LASCA) is another optical technique, related to LDI, which has been used for noninvasive scan-free assessment of burn severity [4,[9][10][11]. In LASCA, a wide-area laser beam illuminates the burn wound to produce speckle from backscatter off the irradiated tissue volume.…”