Spectrophotometric intracutaneous analysis: a novel imaging technique in the assessment of acute burn depth

The noncontact spectrophotometric intracutaneous analysis scope (SIAscope) is a novel portable imaging device that rapidly produces images of the blood and melanin content of large areas of skin. The estimation of burn depth is often difficult in the clinical setting, and this pilot study was conducted to assess the potential for the SIAscope in aiding burn assessment. Nine patients with a variety of burn injuries had images taken of their acute burns within 48 hours of injury, both with a noncontact SIAscope and a laser Doppler perfusion imaging system (LDPI). Results showed that superficial partial thickness burns had increased hemoglobin and loss of melanin on SIAgraphs, whereas deep partial thickness burns had more pronounced hemoglobin concentrations and apparent melanin increases, helping to differentiate these 2 burn types. The SIAscope, a relatively inexpensive, portable device, has the potential to be a highly useful clinical adjunct in the bedside estimation of acute burn depth.     

Near infrared spectroscopic assessment of hemodynamic changes in the early post-burn period

Near infrared reflectance spectroscopy and imaging was used to assess non-invasively the hemodynamic changes that occur in the early post-burn period in cutaneous burn injuries of varying depth. An acute porcine model was used to demonstrate the potential of near infrared spectroscopy and imaging to accurately determine the change in tissue oxygenation, blood volume and tissue water content following a thermal injury. Near infrared spectroscopy was used to monitor tissue at discrete locations, while spectroscopic imaging was able to survey large areas of tissue. Both methods were rapid and non-invasive. Tissue hemoglobin oxygen saturation, total hemoglobin and tissue water content were all affected by thermal injury and changed significantly over a 3 h post-burn monitoring period. Burns that ranged in severity between superficial and full thickness displayed a significantly different hemodynamic response. When the early post-burn profiles (1-3 h) of tissue hemoglobin oxygen saturation, total hemoglobin and tissue water content were considered jointly, injuries leading to superficial, intermediate partial thickness, deep partial thickness and full thickness burns could all be differentiated at high statistical significance. These results suggest that non-invasive hemodynamic monitoring in the early post-burn period using near infrared spectroscopy may be of value in the early assessment of burn injury.     

The progression of burn depth in experimental burns: a histological and methodological study

This study was designed to create a reproducible model for experimental burn wound research in pigs. Previously, the thicker paraspinal skin has been used. We used the more human-like ventral skin to create burns of different depths. Contact burns were created to 11 pigs using a brass plate heated to 100 degrees C in boiling water. Different contact times were used to create burns of different depths. In pigs 1-6, the follow-up time was 72 h and in pigs 7-11 24 h. Burn depth was determined by histology. Histologically, samples were classified into five anatomical layers: epidermis, upper one-third of the dermis, middle third of the dermis, deepest third of the dermis and subcutaneous fat. The location of both thromboses and burn marks were evaluated, respectively. The 1 s contact time lead to a superficial thermal injury, 3 s to a partial thickness and 9 s to a full thickness injury. A progression of burn depth was found until 48 h post-injury. The intra-observer correlation after repeated histological analyses of burn depths by the same histopathologist and the repeatability of burn depth creation yielded kappa coefficients 0.83 and 0.92, respectively. CONCLUSION: a reproducible burn model for further research purposes was obtained.     

Burn depth assessments by photoacoustic imaging and laser Doppler imaging

Diagnosis of burn depths is crucial to determine the treatment plan for severe burn patients. However, an objective method for burn depth assessment has yet to be established, although a commercial laser Doppler imaging (LDI) system is used limitedly. We previously proposed burn depth assessment based on photoacoustic imaging (PAI), in which thermoelastic waves originating from blood under the burned tissue are detected, and we showed the validity of the method by experiments using rat models with three different burn depths: superficial dermal burn, deep dermal burn and deep burn. On the basis of those results, we recently developed a real‐time PAI system for clinical burn diagnosis. Before starting a clinical trial, however, there is a need to reveal more detailed diagnostic characteristics, such as linearity and error, of the PAI system as well as to compare its characteristics with those of an LDI system. In this study, we prepared rat models with burns induced at six different temperatures from 70 to 98 °C, which showed a linear dependence of injury depth on the temperature. Using these models, we examined correlations of signals obtained by PAI and LDI with histologically determined injury depths and burn induction temperatures at 48 hours postburn. We found that the burn depths indicated by PAI were highly correlative with histologically determined injury depths (depths of viable vessels) as well as with burn induction temperatures. Perfusion values measured by LDI were less correlative with these parameters, especially for burns induced at higher temperatures, being attributable to the limited detectable depth for light involving a Doppler shift in tissue. In addition, the measurement errors in PAI were smaller than those in LDI. On the basis of these results, we will be able to start clinical studies using the present PAI system.     

Laser Doppler imaging prediction of burn wound outcome in children

The ability of laser Doppler imaging (LDI) to evaluate burn depth in children was investigated. Fifty-seven patients were prospectively studied over a 10-month period. Each patient was clinically assessed, photographed and independently scanned between 36 and 72 h of the burn. Patients were reviewed until wound healing had occurred within 12 days or skin grafting had been performed. The median age was 1 year and 10 months (range 5 months to 15 years and 8 months). The median body surface area burnt was 7.0% (range 0.5-30%). In 30 patients, the burn did not heal within 12 days, 17 of which were grafted. Clinical examination correctly determined 66% of deep partial or full thickness burns between 36 and 72 h of injury compared to 90% using LDI. The LDI was also more specific; correctly diagnosing 96% of superficial partial thickness burns as opposed to 71% on clinical examination. Moderate degrees of movement did not appear to limit the accuracy of the scan.     

Evaluation of hyperspectral imaging as a modern aid in clinical assessment of burn wounds of the upper extremity

The most common burn wound assessment continues to be the clinical inspection and the tactile examination, which are subjective and remain challenging even for experienced burn surgeons. Recently, hyperspectral imaging camera systems have been increasingly used to support the evaluation of burn wounds. The aim of our study was to determine if hyperspectral imaging analysis differentiates and objectifies the assessment of burn wounds in burns of the upper extremities.We included 97 superficial partial, deep partial dermal burns, and full thickness burns. Hyperspectral imaging analysis was performed for all burns using proprietary software. The software recorded parameters for tissue oxygenation (StO2), tissue hemoglobin index, and near-infrared perfusion. These values were compared with the recordings for healthy, non-burned skin.We found that hyperspectral imaging analysis effectively differentiates burn wounds and shows the ability to distinguish even superficial partial burns from deep partial burns in the near-infrared perfusion analysis feature. Although, it was not possible to differentiate burn wounds in all features.Currently, it is important to optimize the respective reference values of the individual burn degrees for an objectified assessment.     

Assessment of burn depth: a prospective, blinded comparison of laser Doppler imaging and videomicroscopy

INTRODUCTION AND AIMS: There is a need, both in clinical and research settings, for an affordable, objective method of assessing burn depth. This study compares burn depth assessment by videomicroscopy with laser Doppler imaging (LDI) in patients with dermal burns. The videomicroscope is inexpensive compared to LDI, and can visualise the dermal capillary structure, therefore potentially allowing objective assessment of dermal burn injuries. METHODS: Patients admitted <72 h post-injury were included in the trial. Blinded LDI and videomicroscopy assessments were carried out. The patients were then followed up to one of three end-points: primary healing without surgery; early surgery; delayed healing and subsequent split skin grafting. The incidence of infection was also noted. RESULTS: Twenty-seven burn wounds were examined. In superficial partial thickness injuries, the videomicroscope reliably demonstrated an intact or nearly intact dermal vascular structure, progressing through to large amounts of capillary destruction and haemoglobin deposition in deep partial thickness injuries and complete destruction in full thickness injuries. The videomicroscope findings correlated strongly with both those of the LDI (p<0.001) and with clinical outcome (p<0.001). DISCUSSION: The videomicroscope is capable of accurately and objectively assessing burn depth. The results correlated well with both the clinical outcome and the laser Doppler findings. In addition, videomicroscopy is significantly cheaper than LDI and avoids several of the disadvantages of LDI.     

Temperature controlled burn generation system based on a CO2 laser and a silver halide fiber optic radiometer

BACKGROUND AND OBJECTIVES: Experimental animal study of burns is dependent on a reliable burn generation system. Most of the experimental systems used today are unable to produce precise partial thickness burns. This limits the ability to study minor changes associated with burn care. The aim of the study was to develop a method for generating burns with a fixed depth using a CO2 laser burn generation system. MATERIALS AND METHODS: The burn generation system was composed of two components: a burn generation device and a temperature sensing and control system. These components were designed to operate together in order to keep a constant, predetermined skin surface temperature during prolonged burn generation. One hundred thirty-eight spot burns were generated on the back of five shaved 450 g male Wistar rats. The rat skin was exposed to a 70 degrees C for 5-60 seconds. The burned areas were excised and underwent evaluation by hematoxylin-eosin-stained slide microscopy. RESULTS: A linear correlation was found between the duration of exposure and the average burn depth (r = 0.93). This correlation is represented by the equation: burn depth in millimeters = 0.012x (duration in seconds of skin exposure at 70 degrees C). CONCLUSIONS: The fiber-optic-controlled laser burn generation system studied is a reliable tool for creating partial thickness as well as full thickness skin burns in rats.     

Microdialysis for detection of dynamic changes in tissue histamine levels in experimental thermal injury

Histamine is an important mediator contributing to oedema formation after thermal injury. Tissue histamine concentrations have been previously determined by analyzing tissue biopsies. The microdialysis method enables continuous collection of samples from the extracellular tissue fluid. In this experimental burn study on pigs samples from the extracellular fluid for histamine analysis were collected from superficial, partial thickness and full thickness burn sites during a 24-h period. There was a burn depth-related increase in histamine concentrations during the first 2 h post injury. Deep burns induced a more profound initial increase in tissue histamine concentration than the partial thickness and superficial burns. Histamine concentrations at all burn sites declined until 12 h post injury. There was a second rise in tissue histamine concentrations between 12 and 24 h post injury without a rise in plasma histamine concentrations. Histamine concentrations at all burn sites were higher than at the non-burned control sites. The microdialysis technique is an easily applicable method of collecting on-line samples from burned tissue. This method provides a useful tool in investigating the effects of different treatment modalities on the secretion of substances into interstitial fluid within burned tissue.     

Cutaneous microcirculatory assessment of the burn wound is associated with depth of injury and predicts healing time

Rationale

Current trends for the treatment of deep partial thickness and full-thickness burns include early excision and skin grafting. In this study we retrospectively evaluated the ability of Laser Doppler Flowmetry (LDF), taken within 24 h of the burn to predict: (1) burn wound depth and (2) wounds which would heal in less than 21 days.

Method

The Laser Doppler Flowmeter (O2C, LEA Medizintechnik, Germany) was employed to non-invasively measure the cutaneous microcirculation of 173 selected areas on 28 patients who suffered burns.

Results

A distinct association between initial flow (<24 h after burn injury) and the clinical assessment of depth of burn wounds was observed. Wounds demonstrating an initial blood flow of >100 AU were, in 93.1% of cases, correctly (positively) predicted for spontaneous healing within 21 days. A blood flow of <100 AU (negatively) predicted in 88.2%, those wounds which would not go on to heal within 21 days. Sequential measurement analysis (<24 h, 3 days after injury and 6 days after injury) revealed no significant decrease in skin perfusion velocity or flow rate.

Conclusion

LDF can provide immediate results for early determination of burn wound depth and is useful in selecting patients for conservative treatment of their burn wounds.     

An audit of the use of laser Doppler imaging (LDI) in the assessment of burns of intermediate depth

This is the first report of an evaluation of the use of a laser Doppler imager (LDI) scanner in the assessment of burn depth in patients. It is based on a 6-month, prospective audit of 76 burns of intermediate depth. Clinical and LDI assessments of burn wound depth were recorded at 48-72 h post-injury. Histological confirmation of depth was obtained from those burns requiring surgery. A healing time of less than 21 days was taken as confirmation of the injury being an superficial dermal burn. The accuracy of LDI in the assessment of burn depth was 97%, compared with 60-80% for established clinical methods. This audit confirms that LDI is a very accurate measurement tool for the assessment of burn wound depth. We recommend that all burns of intermediate depth should be analysed in this way in order to ensure appropriate management of the burn, to avoid unnecessary surgery and to reduce hospital stay and costs.     

Hand burns in children under 5 years of age

In order to evaluate the epidemiology and functional results of hand burns in young children, 92 consecutive patients (126 hand burns) under age 5 years admitted to a Burn Center were reviewed. Scald burns (49 per cent) were most common, followed by flame (34 per cent), contact (14 per cent) and electrical burns (3 per cent). The child was left unattended by an adult in 53 per cent of cases and documented abuse was present in 6 per cent. The mean total body surface area (TBSA) burned was 17 per cent, and 77 patients (85 per cent) had additional burns in other areas (arms 34 per cent, legs 31 per cent, chest 29 per cent and face 27 per cent).

Palmar burns occurred in 24 hands (19 per cent), dorsal in 41 (33 per cent), while both surfaces were burned in 61 (48 per cent). Joints involved included the MP in 96 (76 per cent). PIP in 87 (69 per cent) and DIP in 80 (63 per cent). The depth was superficial partial thickness in 53 (47 per cent), deep partial in 55 (44 per cent), and full thickness in 18 hands (14 per cent); a total of 29 hands were grafted (15 deep partial and 14 full thickness). Escharotomies were required in 12 hands (9 per cent) (9 flame and 3 scald) and partial amputation of digits was required in 3 (2 per cent).

Follow-up was available in 46 hands from 7 to 120 months (mean 39 months). Partial thickness burns (34) healed with normal (32) or near-normal (2) hand function and developmental delay occurred in one patient. Hand function in 12 full thickness burns was normal in 9, decreased in 3 with developmental delay in 2 patients. The number of reoperations required per hand burned after hospital discharge varied with age (2 years and under 1.2 vs. over 2 years 0.6), depth (deep partial 0.4 vs. full thickness 1·6) and surface involved (palmar 1.3 vs. dorsal 0.1 vs. both 1.5), indicating that children under 2 years with full thickness palmar burns are at increased risk of developing burn scar deformities requiring surgical correction. Although 24 total reoperations were required in 25 deep partial and full thickness hand burns, residual burn scar deformities were present in only 2 hands at follow-up (1 boutonniere and I web space contacture).

It is concluded that the overall outcome of hand burns in this age-group is good and developmental delay is rare with proper acute management and prompt surgical correction of burn scar deformities.     

A pilot evaluation study of high resolution digital thermal imaging in the assessment of burn depth

Thermal imaging is a tool that can be used to determine burn depth. We have revisited the use of this technology in the assessment of burns and aim to establish if high resolution, real-time technology can be practically used in conjunction with clinical examination to determine burn depth. 11 patients with burns affecting upper and lower limbs and the anterior and posterior trunk were included in this study. Digital and thermal images were recorded at between 42 h and 5 days post burn. When compared to skin temperature, full thickness burns were significantly cooler (p < 0.001), as were deep partial thickness burns (p < 0.05). Superficial partial thickness burns were not significantly different in temperature than non-burnt skin (p > 0.05). Typically, full thickness burns were 2.3 °C cooler than non-burnt skin; deep partial thickness burns were 1.2 °C cooler than non-burnt skin; whilst superficial burns were only 0.1 °C cooler. Thermal imaging can correctly determine difference in burn depth. The thermal camera produces images of high resolution and is quick and easy to use.     

Burn depth and its histological measurement

This paper describes a new technique for burn depth measurement, based on the histological assessment of dermal microvascular occlusion in burn biopsies. The technique was validated in a preliminary study of acute progressive microvascular damage in five adults with partial thickness burns. Burn depth was calculated at three time points post burn from the mean histological measurement of the most superficial patent and the deepest blocked vessels in five separate sections from each biopsy. The results were expressed as a percentage of the total dermal thickness and correlated well with the laser Doppler measurement of dermal blood flow and clinical estimation of burn depth. The reproducibility of the technique was tested by the repeated blind analysis of five randomly chosen biopsies on a separate occasion. Altman-Bland plot analysis demonstrated a median variation of 0.1% (95% confidence interval -1 to 2%). A second independent observer (MPHT), who carried out a blind analysis of the same randomly chosen biopsies, tested the precision of the technique. The median variation was 2% (95% confidence interval -5 to 8.5%).     

Short‐wave infrared light imaging measures tissue moisture and distinguishes superficial from deep burns

Existing clinical approaches and tools to measure burn tissue destruction are limited resulting in misdiagnosis of injury depth in over 40% of cases. Thus, our objective in this study was to characterize the ability of short‐wave infrared (SWIR) imaging to detect moisture levels as a surrogate for tissue viability with resolution to differentiate between burns of various depths. To accomplish our aim, we constructed an imaging system consisting of a broad‐band Tungsten light source; 1,200‐, 1,650‐, 1,940‐, and 2,250‐nm wavelength filters; and a specialized SWIR camera. We initially used agar slabs to provide a baseline spectrum for SWIR light imaging and demonstrated the differential absorbance at the multiple wavelengths, with 1,940 nm being the highest absorbed wavelength. These spectral bands were then demonstrated to detect levels of moisture in inorganic and in vivo mice models. The multiwavelength SWIR imaging approach was used to diagnose depth of burns using an in vivo porcine burn model. Healthy and injured skin regions were imaged 72 hours after short (20 seconds) and long (60 seconds) burn application, and biopsies were extracted from those regions for histologic analysis. Burn depth analysis based on collagen coagulation histology confirmed the formation of superficial and deep burns. SWIR multispectral reflectance imaging showed enhanced intensity levels in long burned regions, which correlated with histology and distinguished between superficial and deep burns. This SWIR imaging method represents a novel, real‐time method to objectively distinguishing superficial from deep burns.     

Differentiation of superficial-partial vs. deep-partial thickness burn injuries in vivo by confocal-laser-scanning microscopy

Objective

The current determination of burn depth is based both on a visual and clinical assessment. Confocal-laser-scanning microscopy (CLSM) enables in vivo histomorphological images. We hypothesized that CLSM can differentiate superficial-partial vs. deep-partial thickness burns on a histomorphological level.

Methods

Thirty-eight burn wounds in 14 patients were clinically divided in three groups from superficial (group 1), superficial-partial (group 2) to deep-partial (group 3) thickness burns. CLSM was performed with the Vivascope1500 (Lucid Inc., Rochester, NY, USA) 24 h after burn. The following parameters were assessed: cell size of the granular-layer, thickness of the basal-layer, minimal thickness of the epidermis and number of perfused dermal papillae.

Results

Superficial burns resulted in a significant increase of the cell size of the granular-layer and a higher increase of the minimal thickness of the epidermis as in superficial-partial thickness burns. The granular-layer in partial thickness burns was destroyed. Superficial burns had an increased thickness of the basal-layer; in superficial-partial thickness burns the basal-layer was partly destroyed with complete destruction in deep-partial thickness burns. In superficial burns the perfused dermal papillae were increased significantly, while decreased in superficial-partial thickness, and completely destroyed in deep-partial thickness burns up to a depth of 350 μm.

Conclusions

In vivo confocal-laser-scanning microscopy can differentiate superficial-partial vs. deep-partial thickness burns on a histomorphological level.     

The boiled potato peel as a burn wound dressing: a preliminary report

This paper discusses the suitability of potato peel as a burn wound dressing in developing countries. Clinical trials have demonstrated that epithelial growth occurs under the potato peel dressing in superficial partial thickness skin loss burns. In deep partial, full skin thickness burns and in the late granulating burn wound the results are not so favourable. More experience is required.     

Clinical utilization of near-infrared spectroscopy devices for burn depth assessment

The diagnosis of burn depth is based on a visual assessment and can be subjective. Near-infrared (NIR) spectroscopic devices were used preclinically with positive results. The purpose of this study was to test the devices in a clinical setting using easily identifiable burn wounds. Adult patients with acute superficial and full-thickness burns were enrolled. NIR point spectroscopy and imaging devices were used to collect hemodynamic data from the burn site and an adjacent unburned control site. Oxy-hemoglobin and deoxy-hemoglobin concentrations were extracted from spectroscopic data and reported as oxygen saturation and total hemoglobin. Sixteen patients (n=16) were included in the study with equal numbers in both burn wound groups. Point spectroscopy data showed an increase in oxygen saturation (p<0.0095) and total hemoglobin (<0.0001) in comparison with the respective control areas for superficial burn wounds. The opposite was true for full-thickness burns, which showed a decrease in oxygenation (p<0.0001) and total hemoglobin (p<0.0147) in comparison with control areas. NIR imaging technology provides an estimate of hemodynamic parameters and could easily distinguish superficial and full-thickness burn wounds. These results confirm that NIR devices can successfully distinguish superficial and full-thickness burn injuries.     

Discordance between histologic and visual assessment of tissue viability in excised burn wound tissue

The regenerative capacity of burn wounds, and the need for surgical intervention, depends on wound depth. Clinical visual assessment is considered the gold standard for burn depth assessment but it remains a subjective and inaccurate method for tissue evaluation. The purpose of this study was to compare visual assessment with microscopic and molecular techniques for human burn depth determination, and illustrate differences in the evaluation of tissue for potential regenerative capacity. Using intraoperative visual assessment, patients were identified as having deep partial thickness or full thickness burn wounds. Tangential excisions of burn tissue were processed with hematoxylin and eosin to visualize tissue morphology, lactate dehydrogenase assay to ascertain cellular viability, and Keratin‐15 and Ki67 to identify epidermal progenitor cells and proliferative capacity, respectively. RNA from deep partial and full thickness burn tissue as well as normal tissue controls were submitted for RNA sequencing. Lactate dehydrogenase, Keratin‐15, and Ki67 were found throughout the excised burn wound tissue in both deep partial thickness burn tissues and in the second tangential excision of full thickness burn tissues. RNA sequencing demonstrated regenerative capacity in both deep partial and full thickness burn tissue, however a greater capacity for regeneration was present in deep partial thickness compared with full thickness burn tissues. In this study, we highlight the discordance that exists between the intraoperative clinical identification of burn injury depth, and microscopic and molecular determination of viability and regenerative capacity. Current methods utilizing visual assessment for depth of injury are imprecise, and can lead to removal of viable tissue. Additionally, hematoxylin and eosin microscopic analysis should not be used as the sole method in research or clinical determination of depth, as there are no differences in staining between viable and nonviable tissue.     

Red blood cell and tissue water content in experimental thermal injury

Oedema formation and changes in local blood flow are known phenomena in burns. The relationship between these two is not clearly described. The aim of this study was firstly to examine both the contents of red blood cells and tissue water in skin and subcutaneous fat after experimental burns of different depths in pigs, and secondly, to confirm our recent findings of the increased dielectric constant of skin and subcutaneous fat reflecting considerable oedema formation, especially in fat after thermal injury.

Methods

Superficial, partial and full thickness contact burns were created to pigs and followed for 24 h. Radioactive Cr-51 labelling of red cells was used to estimate the number of red cells in tissue, and the absolute amount of water was determined by lyophilisation.

Results

A decreased number of labelled red cells in skin and an increase in tissue water in subcutaneous fat were found regardless of burn depth. The highest water amount in fat was found in the partial thickness burns.

Conclusion

All burn depths resulted in a diminished number of labelled red blood cells in skin and a significant increase in the absolute water amount in subcutaneous fat at 24 h post injury. The findings in fat support our recent findings of highly elevated dielectric constants measured by the new in vivo method of dielectric measurements.