120 Terahertz Spectral Imaging for Burn Depth Determination in an in Vivo Porcine Scald Model

Abstract

Abstract Introduction Clinical evaluation of burns results in about 50–70% accuracy in predicting the final burn progression and healing outcome in partial thickness burns. Early and accurate assessment of burn wounds is critical for determining the course of clinical management. Terahertz (THz) spectral imaging is a promising biomedical imaging modality that has been used to quantitatively determine burn severity in acute rodent models. Here, we hypothesized that the new THz modality can determine burn depth and predict the wound healing outcome of injuries using a standardized porcine model. We developed a handheld THz instrument to obtain diagnostic images from large animal burns with varying severities. The results showed that the THz imaging can differentiate between different burn groups defined by injury depth on days 1–5 post-burn, and predict their ultimate outcome defined by reepithelialization during a 28-day study period (1-way ANOVA, p< 0.05). Methods Multiple 1 inch diameter standardized cutaneous burns were created (n = 20–24 per pig) in 3 anesthetized female domestic pigs (~32kg) using a circulating heated water in replicates. The temperatures were controlled and kept constant at 95 C degrees using thermosensors, while the duration of exposure was varied between 5, 15, or 25 seconds. Burns were covered with a topical antibiotic ointment and frequent dressing changes were performed for 4 weeks. Daily THz scans were obtained from each burn during the first week, corresponding to the peak of the anti-inflammatory response of the burns. After the initial 5 days, weekly scans were obtained until the ultimate healing outcome was determined by an experienced surgeon and a blinded histopathologist. Periodic punch biopsies were taken to determine burn depth, percentage burns reepithelialized within 21 days, and depth of scar at 28 days. Results Attached figures show representative daily visual and THz images of burns with the associated ROI. Bar plots show mean and standard deviation of spectral amplitude (SA) and spectral slope (SS). Low severity burns showed decreasing SA and increasing SS over time, whereas SS from 25 second burns remained negative and SA increased by day 4. Variation in SS suggests changes in density of skin structure as a result of scattering and changes in SA suggests variations in water content. Detailed statistical analysis is in attached table. Conclusions Using the novel handheld THz scanner, analysis of the spectral slopes signal showed the ability of the new Terahertz imaging modality in differentiating between different burn severities (p < 0.05) and evaluating burn progression. Applicability of Research to Practice THz modality can result in improvement in the accuracy of burn triage, which in turn can lead to better wound healing outcomes, reduction in length of hospital stay and improvement in overall recovery of the patients.