Accuracy of early burn depth assessment by laser Doppler imaging on different days post burn

Background

Accurate diagnosis of burn depth is essential in selecting the most appropriate treatment. Early assessment of burn depth by clinical means only has been shown to be inaccurate, resulting in unnecessary operations or delay of grafting procedures. Laser Doppler imaging (LDI) was reported as an objective technique to determine the depth of a burn wound, but the accuracy on very early days post burn has never been investigated yet.

Methods

In 40 patients with intermediate depth burns, we prospectively evaluated and compared the accuracy of the LDI measurements with the clinical assessments on days 0, 1, 3, 5, 8. Clinical evaluation of the depth of the burn was performed by two observers blinded to the LDI images. Accuracies were assessed by comparison with outcome: healing times longer than 21 days were considered to be equivalent to a biopsy finding of a deep dermal wound. Obviously superficial and full thickness wounds were excluded. LDI flux level was used for LDI prediction of outcome: less than 220 PU to predict non-healing at day 21.

Results

The accuracies of burn depth assessments on the day of burn and post burn days 0, 1, 3, 5 and 8 using LDI were 54%, 79.5%, 95%, 97% and 100% compared with clinical assessment accuracies of 40.6%, 61.5%, 52.5%, 71.4% and 100%, respectively. LDI accuracy was significantly higher than clinical accuracy on day 3 (p < 0.001) and day 5 (p = 0.005). Burn depth conversion was also considered. This is the first study to quantify the advantage of LDI scanning over clinical assessments during these important early after burn days.     

Prospective comparative evaluation study of Laser Doppler Imaging and thermal imaging in the assessment of burn depth

Introduction

The accurate assessment of burn depth is challenging but crucial for surgical excision and tissue preservation. Laser Doppler Imaging (LDI) has gained increasing acceptance as a tool to aid depth assessment but its adoption is hampered by high costs, long scan times and limited portability. Thermal imaging is touted as a suitable alternative however few comparison studies have been done.

Burn imaging with a whole field laser Doppler perfusion imager based on a CMOS imaging array

Laser Doppler perfusion imaging (LDPI) has been proven to be a useful tool in predicting the burn wound outcome in an early stage. A major disadvantage of scanning beam LDPI devices is their slow scanning speed, leading to patient discomfort and imaging artifacts. We have developed the Twente Optical Perfusion Camera (TOPCam), a whole field laser Doppler perfusion imager based on a CMOS imaging array, which is two orders of magnitude faster than scanning beam LDPI systems. In this paper the first clinical results of the TOPCam in the setting of a burn centre are presented. The paper shows perfusion images of burns of various degrees. While our system encounters problems caused by blisters, tissue necrosis, surface reflection and curvature in a manner similar to scanning beam imagers, it poses a clear advantage in terms of procedure time. Image quality in terms of dynamic range and resolution appears to be sufficient for burn diagnosis. Hence, we made important steps in overcoming the limitations of LDPI in burn diagnosis imposed by the measurement speed.     

Early depth assessment of local burns by videomicroscopy: a novel proposed classification

Purpose

Videomicroscopy is very useful for burn depth assessment in an early phase; however, there is no practical classification that includes complicated anatomic, pathologic, and morphologic findings of burn wounds.The aim of this study was to propose a novel classification to assess burn depth in its early phase easily and reliably by videomicroscopy.

Methods

Forty-four patients with 56 intermediate-depth burn wounds were included. Burn depth was divided into each grade according to our proposed classification, which is composed of five categories based on dermal capillary integrity patterns. The intrarater and interrater reliabilities of the assessment by the second and third authors were evaluated by Cohen's unweighted κ-value.

Results

The results of the measurements according to the proposed classification showed an accuracy of 92.9%, sensitivity of 81.8%, and specificity of 100.0%.The intrarater reliability of the second and third authors showed substantial agreement (κ = 0.719 and 0.729, respectively). The interrater reliability of the sum of each observer's variable also showed substantial agreement (κ = 0.636).

Conclusion

This pattern analysis system is easy to use even for inexperienced personnel, and is reliable with high accuracy and specificity. Intrarater and interrater statistics also support its reliability and reproducibility.     

Ultrasound assessed thickness of burn scars in association with laser Doppler imaging determined depth of burns in paediatric patients

This study describes the ultrasound assessment of burn scars in paediatric patients and the association of these scar thickness with laser Doppler imaging (LDI) determined burn depth. A total of 60 ultrasound scar assessments were conducted on 33 scars from 21 paediatric burn patients at 3, 6 and 9 months after-burn. The mean of peak scar thickness was 0.39 ± 0.032 cm, with the thickest at 6 months (0.40 ± 0.036 cm). There were 17 scald burn scars (0.34 ± 0.045 cm), 4 contact burn scars (0.61 ± 0.092 cm), and 10 flame burn scars (0.42 ± 0.058 cm). Each group of scars followed normal distributions. Twenty-three scars had original burns successfully scanned by LDI and various depths of burns were presented by different colours according to blood perfusion units (PU), with dark blue <125, light blue 125–250, and green 250–440 PU. The thickness of these scars was significantly different between the predominant colours of burns, with the thinnest scars for green coloured burns and the thickest for dark blue coloured burns. Within light blue burns, grafted burns healed with significantly thinner scars than non-grafted burns. This study indicates that LDI can be used for predicting the risk of hypertrophic scarring and for guiding burn care. To our knowledge, this is the first study to correlate the thickness of burns scars by ultrasound scan with burn depth determined by LDI.     

Early depth assessment of local burns by videomicroscopy: 24 h after injury is a critical time point

Purpose

Videomicroscopy has simple and prompt operability, and useful in the burn depth assessment in its early phase. A burn wound is, however, a dynamic environment in the first few days and the critical time to assess a burn wound by videomicroscopy has not been investigated. The aim of this study is to investigate the critical time point to assess the burn depth by videomicroscopy.

Methods

Forty one patients with 44 intermediate depth burns admitted within 7 days after injury were included. Accuracies were assessed by comparison with clinical outcome: healing within 21 days after injury or not with conservative treatment. We prospectively evaluated and compared the accuracy of the videomicroscopy measurements with the clinical assessments. All findings were serialized in order of time after injury and divided into three groups, and we compared the appreciation of burn depth by videomicroscopy findings among groups.

Results

The videomicroscopy measurements is significantly accurate compared with clinical assessments (p = 0.001). The accuracy of videomicroscopy measurements was significantly lower in the post-injury <24 h group compared with post-injury ≥24 h group (p = 0.004).

Conclusion

Videomicroscopy is effective tool in assessment of early burn depth and the critical time point to assess the burn depth by videomicroscopy is 24 h after injury.     

Burn wound healing time assessed by laser Doppler imaging. Part 2: validation of a dedicated colour code for image interpretation

Introduction

Laser Doppler imaging (LDI) has been investigated and used since 1993 for the assessment of burn wounds. Here we describe tests that validate use of the dedicated colour palette, derived in Part 1, for a standardised interpretation of LDI images for prediction of healing time (<14 days, 14-21 days or >21 days). We also describe clinical and technical factors to be taken into account during LDI imaging and during image interpretation.

Methods

(1) A cohort of images, selected at random, were assessed, according to strict rules of interpretation, by 6 clinicians against photographs of healing, for accuracy of healing time prediction and clinical usefulness using five-point scales. (2) All images were assessed technically in a similar way for accuracy and the accuracy was further studied by analysing the data by ordinal logistic regression to predict the dependence of burn healing time on demographic variables (age, sex, race, %TBSA, burn cause and site). (3) Where average LDI blood flow could be determined, regression analysis was used to assess the potential accuracy of the technique.

Results

(1) Clinical accuracy was found to be 93% and usefulness was 89%; (2) technical accuracy was found to be 96%; (3) regression analysis found that a potential accuracy of 90.9% could be achieved using LDI results alone, increasing to 92% if gender was also considered; no other parameters had an influence on healing time prediction.

Conclusion

LDI can be used in a standardised way as a valid tool for improving on clinical assessment of burn wounds. This can enable earlier appropriate management.     

Relationship between healing time and mean perfusion units of laser Doppler imaging (LDI) in pediatric burns

Background

Laser Doppler imaging (LDI) is a noninvasive technique used to assess burn depth. However, there have been no studies regarding the use of LDI in predicting burn healing time.

Objectives

The aims of this study are to evaluate the relationship between healing time and the amount of perfusion seen on LDI and to determine a cut-off value for LDI that predicts if a burn will heal within 14 days.

Study design

Consecutive patients younger than 15 years old with partial-thickness burns were recruited from May to November 2006 for this prospective observational study. The mean number of perfusion units (PU) as determined by LDI (Periscan PIM 3 system) was obtained within 2–3 days following injury. Healing time was estimated clinically by two physicians and marked by the observation of reepithelization. The mean PU was compared between the early (healed with 14 days) and late healing groups (healed later than 14 days). The usefulness of the mean PU in predicting healing time within 14 days was estimated by receiver operating characteristic curve analysis.

Results

A total of 103 patients with 181 partial-thickness burn wounds were enrolled in this study. The mean PU from LDI was higher in the early healing group compared to the late healing group (380.2 ± 157.8 vs. 185.8 ± 115.8, p < 0.001). When using 250 PUs as a cut-off value to predict early healing, the sensitivity and specificity were 80.6% and 76.9%, respectively. The area under the ROC curve was 0.844 (p < 0.001, 95% CI = 0.780–0.908).

Conclusions

This study suggests the mean PU as determined by LDI can be used as a valuable tool in predicting the healing time of burn wounds.     

Assessment of burn depth and burn wound healing potential

The depth of a burn wound and/or its healing potential are the most important determinants of the therapeutic management and of the residual morbidity or scarring. Traditionally, burn surgeons divide burns into superficial which heal by rapid re-epithelialization with minimal scarring and deep burns requiring surgical therapy. Clinical assessment remains the most frequent technique to measure the depth of a burn wound although this has been shown to be accurate in only 60-75% of the cases, even when carried out by an experienced burn surgeon. In this article we review all current modalities useful to provide an objective assessment of the burn wound depth, from simple clinical evaluation to biopsy and histology and to various perfusion measurement techniques such as thermography, vital dyes, video angiography, video microscopy, and laser Doppler techniques. The different needs according to the different diagnostic situations are considered. It is concluded that for the initial emergency assessment, the use of telemetry and simple burn photographs are the best option, that for research purposes a wide range of different techniques can be used but that, most importantly, for the actual treatment decisions, laser Doppler imaging is the only technique that has been shown to accurately predict wound outcome with a large weight of evidence. Moreover this technique has been approved for burn depth assessment by regulatory bodies including the FDA.     

Laser Doppler imaging of paediatric burns: burn wound outcome can be predicted independent of clinical examination

This study sought to assess the validity of independent, blinded reporting of Laser Doppler Imaging (LDI) prediction of burn wound outcome in children. Two experienced paediatric burn consultants were invited to report on LDI scans performed routinely within 3 days of burn. They were provided with the LDI flux image, a low-resolution colour digital photograph of the burnt area and a basic history. Report predictions were correlated with outcome. Reports were compiled on 50 scans performed on 31 patients at a mean of 54h post burn. Of the 100 reports generated, mean correlation with outcome was 97%. If the LDI predicted a deep burn, it was always correct. Non-correlations were due to a number of factors including inadequate scanning of the affected area, excessive movement and residual wound debris. Accurate prediction of burn wound outcome could be made via the standard information generated by LDI and appeared more reliable than clinical prediction. The correlation improved with increasing experience with LDI.     

Real-time burn depth assessment using artificial networks: a large-scale,multicentre study

IntroductionEarly judgment of the depth of burns is very important for the accurate formulation of treatment plans. In medical imaging the application of Artificial Intelligence has the potential for serving as a very experienced assistant to improve early clinical diagnosis. Due to lack of large volume of a particular feature, there has been almost no progress in burn field.Methods484 early wound images are collected on patients who discharged home after a burn injury in 48 h, from five different levels of hospitals in Hunan Province China. According to actual healing time, all images are manually annotated by five professional burn surgeons and divided into three sets which are shallow(0–10 days), moderate(11–20 days) and deep(more than 21 days or skin graft healing). These ROIs were further divided into 5637 patches sizes 224 × 224 pixels, of which 1733 shallow, 1804 moderate, and 2100 deep. We used transfer learning suing a Pre-trained ResNet50 model and the ratio of all images is 7:1.5:1.5 for training:validation:test.ResultsA novel artificial burn depth recognition model based on convolutional neural network was established and the diagnostic accuracy of the three types of burns is about 80%.DiscussionThe actual healing time can be used to deduce the depth of burn involvement. The artificial burn depth recognition model can accurately infer healing time and burn depth of the patient, which is expected to be used for auxiliary diagnosis improvement.     

Burn depth assessment using hyperspectral imaging in a prospective single center study

BackgroundThe assessment of thermal burn depth remains challenging. Over the last decades, several optical systems were developed to determine burn depth. So far, only laser doppler imaging (LDI) has been shown to be reliable while others such as infrared thermography or spectrophotometric intracutaneous analysis have been less accurate. The aim of our study is to evaluate hyperspectral imaging (HSI) as a new optical device.MethodsPatients suffering thermal trauma treated in a burn unit in Germany between November 2019 and September 2020 were included. Inclusion criteria were age ≥18 years, 2^nd or 3^rd degree thermal burns, written informed consent and presentation within 24 h after injury. Clinical assessment and hyperspectral imaging were performed 24, 48 and 72 h after the injury. Patients in whom secondary wound closure was complete within 21 days (group A) were compared to patients in whom secondary wound closure took more than 21 days or where skin grafting was indicated (group B). Demographic data and the primary parameters generated by HSI were documented. A Mann Whitney-U test was performed to compare the groups. A p-value below 0.05 was considered to be statistically significant. The data generated using HSI were combined to create the HSI burn index (BI). Using a logistic regression and receiver operating characteristics curve (ROC) sensitivity and specificity of the BI were calculated. The trial was officially registered on DRKS (registration number: DRKS00022843).ResultsOverall, 59 patients with burn wounds were eligible for inclusion. Ten patients were excluded because of a poor data quality. Group A comprised 36 patients with a mean age of 41.5 years and a mean burnt body surface area of 2.7%. In comparison, 13 patients were allocated to group B because of the need for a skin graft (n = 10) or protracted secondary wound closure lasting more than 21 days. The mean age of these patients was 46.8 years. They had a mean affected body surface area of 4.0%. 24, 48, and 72 h after trauma the BI was 1.0 ± 0.28, 1.2 ± 0.29 and 1.55 ± 0.27 in group A and 0.78 ± 0.14, 1.05 ± 0.23 and 1.23 ± 0.27 in group B. At every time point significant differences were demonstrated between the groups. At 24 h, ROC analysis demonstrated BI threshold of 0.95 (sensitivity 0.61/specificity 1.0), on the second day of 1.17 (sensitivity 0.51/specificity 0.81) and on the third day of 1.27 (sensitivity 0.92/specificity 0.71).ConclusionChanges in microcirculation within the first 72 h after thermal trauma were reflected by an increasing BI in both groups. After 72 h, the BI is able to predict the need for a skin graft with a sensitivity of 92% and a specificity of 71%.     

Reflection-optical multispectral imaging method for objective determination of burn depth

We present a noninvasive imaging method for objective determination of the depth of burn wounds. The method is easy to use and enables even the nonspecialized physician to determine the burn depth at a very early time and to make available an objective documentation for quality management.     

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.     

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.     

A comparison of laser Doppler imaging with other measurement techniques to assess burn depth

Evaluation of burn depth is crucial in supporting treatment decisions, yet none of the commonly used methods offer clinicians the desired level of accuracy. This article reviews the literature to determine the advantages of laser Doppler imaging.     

Review of methodological developments in laser Doppler flowmetry

Laser Doppler flowmetry is a non-invasive method of measuring microcirculatory blood flow in tissue. In this review the technique is discussed in detail. The theoretical and experimental developments to improve the technique are reviewed. The limitations of the method are elaborated upon, and the research done so far to overcome these limitations is critically assessed.

Evaluation of microcirculation and wound-closing tension after undermining the skin. A study in a porcine model using laser Doppler perfusion imaging

Undermining the skin can reduce wound tension when closing skin defects and thereby can provide a potentially better microcirculation. On the other hand, undermining causes damage to blood vessels. In this study the relationship between wound tension and microcirculation in undermined wounds was evaluated. A porcine model was used and in three pigs six undermined excisions and six control excisions were done. The tension needed to close the wound was noted and the postoperative microcirculation was measured with a laser Doppler perfusion imager. Undermining the skin gave significantly reduced (p<0.05) wound-closing tension with a mean decrease of 25% (95% CI: 17–33%). The postoperative microcirculation in the undermined wound was significantly reduced (p<0.05) with a mean of 28% (95% CI: 8–46%). Undermining the skin reduced the wound-closing tension. In our model the positive effect on the microcirculation by reducing the wound-closing tension was less than the negative effect of cutting the perforating blood vessels to the skin with a net decrease in blood flow.