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A porcine burn model was used to demonstrate the potential of using the attenuation of the optical coherence tomography signal as an indicator of the degree of burn injury. A swept-source optical coherence tomography system amenable to operating in burn trauma centers and in surgeries was designed and built in-house. A special design feature of our optical coherence tomography system is its large stand-off distance (272 mm) between the data collecting lens terminating the sample arm and the sample surface. This feature eliminates potential contact between patient and instrument, and thereby decreases the potential for infection through remote contamination. Four contact burn types, histologically confirmed to produce superficial, superficial-intermediate, deeper-intermediate and full thickness injuries, were investigated. Burn types and matching control sites were randomly placed over a predetermined grid. The burn injuries were restricted to under 1% of the total body surface area in order to minimize systemic effects and eliminate cross-talk between the measurement sites on the grid. At each grid location, the data was acquired very fast, amounting to total acquisition times of less than 3 seconds per data set, speeds practical for use in the high-stress environment characterizing burn trauma units. We used attenuation coefficients of optical coherence tomography signal in tissue as a summary parameter for burn injury determination. This simple parameter can be computed in real-time during the OCT acquisition sequence across the burn wound providing the clinician a real-time assessment of the degree of injury. *Correspondence to: Dan P Popescu, National Research Council of Canada, Medical Devices Research Center, 435 Ellice Ave, Winnipeg MB, R3B 1Y6, Canada, E-mail: Dan.Popescu@nrc-cnrc.gc.ca Received: March 25, 2019; Accepted: April 04, 2019; Published: April 10, 2019 Introduction Burn injuries can be life threatening or, at their very least, life altering. Accurate and early assessment of burn injuries improves outcomes as well as the functional recovery of the patient. One of the key facts to be established is if healing will require just appropriate wound care or surgery. For burn specialists it is indeed very easy to differentiate between superficial (first degree) and full-thickness (third degree) burns. Meanwhile, diagnosis becomes more challenging for classification of intermediate thickness also known as partial-thickness cases. The accuracy of the diagnosis is further challenged when it is made early in the post-burn period as the wound responds to the insult. It is common knowledge that prognosis for burn injuries is critically dependent on the supply of blood to the wound. The burn depth also relates directly to its healing capacity. Superficial injuries, where the vascular supply to the dermis of the skin remains largely intact, generally heal with standard wound care. Meanwhile full thickness injuries, which destroy the vascular supply in the dermis, do not spontaneously heal and will require surgery. The question is what happens to the wounds between these two extremes? The outcomes of these partial thickness injuries are very difficult to predict, especially immediately postburn, and there are no objective methods to help in determining wound depth or healing potential of such injuries. Generally, a wait and see approach is adopted but this approach increases the infection risk, the chances for a thicker scar and also prolongs the pain associated with a healing wound. On the other hand, a hastened skin graft surgery could mean expensive over-treatment coming with a host of other potential complications. Therefore, a technology that can accurately predict the outcome of partial thickness burn wounds in the early post-burn period would dramatically improve the management of burn injuries by enabling prompt and appropriate treatment. One current standard practice for burn severity determination is subjective clinical assessment of the burn wound. Nevertheless, experienced clinicians have demonstrated inaccurate diagnosis between deep and superficial partial thickness wounds burns approximately 3550% of the time [1-3]. By convention, experts anatomically categorize the depth of a burn into four major groups: superficial (only the epidermis is injured), superficial partial thickness (papillary dermis), deep partial thickness burn (burn reaches the reticular dermis) and full thickness (injury affects the entire dermis and extends into the subcutaneous fat). Adding another degree of complexity is the fact that burns are generally heterogeneous, with appearance varying affected across the affected region. Additionally, burn wounds are dynamic injuries responding to the inflammatory cascade that the body mounts as a defense against the insult. Injuries, which can appear superficial at the outset can convert to non-viable full-thickness injuries within the first 72 h [3,4]. Thus, treatment decisions for any thermal injury depends upon the burn depth but inaccurate diagnosis translates into either treatment delays or unnecessary surgery. Providing a suitable treatment Popescu DP (2019) Pre-clinical demonstration of a rapid and non-contact method to quantify burn injury using attenuation of the optical coherence tomography signal Biol Eng Med, 2019 doi: 10.15761/BEM.1000168 Volume 4: 2-6 in real-time. From the video sequence, macroscopic maps of vascular circulation can be extracted. Its utility has been clearly demonstrated even in the presence of other microvascular pathologies, such as diabetes and heart failure [11]. The obvious drawback of ICG videoangiography is the need for intravascular dye injection, since sometimes ICG is associated with headache, pruritis, urticaria, diaphoresis, and the risk of life-threatening anaphylactic reaction [12]. Safety has not been wellestablished in pediatric, pregnant or lactating patients. Additionally, measurements obtained via ICG videoangiography are relative to normal skin controls, and anatomically equivalent regions of normal skin are not always available in burn subjects. Another burn diagnostic method based on the variations of reflectance and/or absorption spectra produced by different degrees of injury is near-infrared spectroscopy (NIRS). It was demonstrated that NIRS differentiate between superficial partial and deep partial burns with an accuracy of 87% in animal models [13]. Near-infrared light can penetrate further into tissue than visible light, and relays information on several biochemical constituents in the dermis. The most relevant constituent for burn assessment is hemoglobin. The NIRS ability to differentiate between oxygenated and deoxygenated blood confers an advantage to this modality. Thus, rather than measure a parameter related to blood flow, NIRS identifies blood oxygen presence or the lack thereof. Moreover, it has been reported that NIRS has the potential to identify collagen damaged due to burn wounds [14]. Therefore, a possible path to enhance the predictive reliability of this method would be by using an NIRS instrument that could simultaneously probe oxyhemoglobin and de-oxyhemoglobin [15]. On the downside, NIRS scans may take several minutes to complete. In some configurations, for example point source-to-point detector devices, scanning requires physical contact with the wound thus causing discomfort and enhancing contamination potential. It had been shown that NIRS reliably differentiates superficial from full thickness burns in human subjects but is not specific enough to diagnose superficial partial from deep partial [16]. Finally, although allowing for a great diversity of system designs and data algorithms, there is also a distinct lack of standardization in NIRS instrumentation to this day. To date, NIRS methods have not been clinically adopted in the assessment of burns. Various microscopy imaging methods, such as capillary videomicroscopy, orthogonal polarization spectral microscopy and reflection-mode confocal microscopy, can also be included amongst the methods used for burn diagnostics. All these microscopy imaging modalities share similar drawbacks: very small fields of view, timeconsuming, requirement of special training both on the clinical and technical side, as well as small distances between the objective lens and patient thus increasing the potential for wound contamination.

Pre-Clinical Demonstration of a Rapid and Non-Contact Method to Quantify Burn Injury Using Attenuation of the Optical Coherence Tomography Signal