Quantitative assessment of burn injury in porcine skin with high-frequency ultrasonic imaging

Early excision and grafting of full thickness burns has been shown to decrease morbidity and mortality. Errors made in assessing acute burn depth are common and result in prolonged hospitalization in expectant healing of full-thickness burns and in unnecessary excision and grafting of potentially regenerative partial-thickness burns. High-frequency ultrasonic imaging may be a noninvasive, convenient means of quantitating burn depth. A depth analysis system for imaging burned skin was developed using a high-frequency 18.5 MHz (nominal 25 MHz) pulse-echo ultrasound system with a longitudinal resolution of 86 mu. Five adult mini-swine (15 kg) were burned with a temperature-(190 degrees C) and pressure-controlled (236 g/cm2) burning iron. A series of burn durations (1-45 seconds) was used to inflict partial- and full-thickness burns of various depths. Ultrasonic scans of the acutely excised burns were performed across the lateral margin of the burn, including adjacent normal skin to serve as control. Direct histologic comparison was made with each scan plane. Average burn and normal skin depth measurements were made by independent observers for 34 scans and corresponding histologic sections. A significant correlation was achieved between burn depth and percent burn (burn depth/adjacent normal skin depth) as measured by ultrasound and histology (R = 0.90, t = 11.2, P less than .001).