Active dynamic infrared thermal imaging in burn depth evaluation.

The aim of this study was to find the relationship between active dynamic thermography (ADT) with cold excitation and burn depth. This new modality of evaluation of burns seems to be an attractive proposal for quantitative classification, allowing proper choice of burn wound treatment: conservative or surgical, especially compared with static thermography. The work was an in vivo experiment on domestic pigs, and a small number of patients were also diagnosed as part of the study. Statistical analysis showed a high correlation between the ADT synthetic parameter--thermal time constant, τ--and the classification of burn wounds that were predicted to heal within 3 weeks and so were treated conservatively and those that were predicted to not heal within 3 weeks and so were surgically treated. The results of the study show an accuracy of 60.7% for clinical evaluation, 69.6% for static thermography, 83.0% for ADT, and 84.0% for histopathologic assessment. The authors have concluded that the ADT method with cold excitation is suitable for the qualitative and quantitative assessment of burn depth.

Monitoring of myocardium state during off-pump coronary artery by-pass grafting.

A measurement technique for evaluation of processes occurring in the myocardium during blood flow arrest is presented. The system is devoted to monitoring the myocardium state during off-pump coronary artery by-pass grafting, i.e. during a surgical operation performed on a beating heart. A substantial part of the system is a probe whose construction is similar to a mechanical stabilizer. Such a stabilizer is used for preventing the myocardium from moving, thus it enables stitching of the graft and artery. In comparison to the commercially available stabilizer the developed probe is enhanced with a set of electrodes. These electrodes enable simultaneous measurements of impedance and electrograms. Examples of recordings made during in vivo studies are also presented. Thus, the proposed method is applicable and potentially very useful in clinical practice.

Thermal monitoring of the myocardium under blood arrest preliminary study.

A method for monitoring the state of the myocardium during cardiosurgical interventions based on thermal IR imaging is presented. This method called Active Dynamic Thermography (ADT) uses an external excitation source to induce thermal transient processes in a tested object. Recording time series of thermograms allows to calculate parametric images - distribution of the thermal time constant at the visible surface of the myocardium - correlated to the physiology state of tested tissues. In the experiment performed the blood arrest in the left ventricle (causing in longer period heart infarct) was generated by clamping the left anterior descending artery (LAD). During LAD occlusion the ADT procedure was applied using cooling external excitation source. In summary, the calculated time constant images provide data of the tested structure and functional information of myocardium infarct. This allows to track changes in blood flow in the myocardium and inspection of the quality of the intervention during cardiosurgical procedures.

Thermal parametric imaging in the evaluation of skin burn depth.

The aim of this paper is to determine the extent to which infrared (IR) thermal imaging may be used for skin burn depth evaluation. The analysis can be made on the basis of the development of a thermal model of the burned skin. Different methods such as the traditional clinical visual approach and the IR imaging modalities of static IR thermal imaging, active IR thermal imaging and active-dynamic IR thermal imaging (ADT) are analyzed from the point of view of skin burn depth diagnostics. In ADT, a new approach is proposed on the basis of parametric image synthesis. Calculation software is implemented for single-node and distributed systems. The properties of all the methods are verified in experiments using phantoms and subsequently in vivo with animals with a reference histopathological examination. The results indicate that it is possible to distinguish objectively and quantitatively burns which will heal spontaneously within three weeks of infliction and which should be treated conservatively from those which need surgery because they will not heal within this period.

Burn depths evaluation based on active dynamic IR thermal imaging--a preliminary study.

Proper diagnostic assessment of burn wound depth is of the highest importance in selecting the mode of burn wound treatment. Several diagnostic methods--clinical and histopathological evaluation, as well as methods employing IR imaging--static thermography and active dynamic thermography (ADT)--are compared on the basis of in vivo experiments conducted on three domestic pigs (23 burn wounds). ADT is presented here as a new, reliable and quantitative method of assessing burn wound depth on the basis of discrimination of the thermal properties of burnt tissue. In the case of ADT registration of thermal images was performed following thermal pulse excitation. A series of captured infrared images was used as the basis for calculating the thermal time constant tau for each pixel. The parameter values were compared with histopathological and clinical assessments of burn depth. The mean value of tau was found for burns, which heal within 3 weeks (tau=12.08+/-1.94s) and for burns, which did not heal during this period (tau=9.07+/-0.68s), p<0.05. The accuracy, sensitivity and specificity of all the methods tested were compared, the best results coming from ADT. The ADT method is fast, non-invasive and relatively inexpensive, although it still requires further animal experimentation as well as clinical study to confirm the results.

Static thermography revisited--an adjunct method for determining the depth of the burn injury.

The aim of the study was to investigate the relationship between the static thermography figure of merit DeltaT (the difference in mean values of skin area temperature for the burn wound area and the unaffected reference skin area) and a means of burn classification which would be most suitable for the choice of treatment. The work was an in vivo animal experiment. Statistical analysis showed a high correlation between the DeltaT parameter and histopathological assessment. With regard to the choice of treatment, the most useful correlation was found to be that between DeltaT and the classification of burn wounds into those healed in 3 weeks and those unhealed. The results of this study have revealed a quantitative criterion DeltaT for burn classification. The study suggests that particular burn centres using static thermography use a DeltaT parameter based on their own values for burn classification so as to group burn wounds into those that healed in 3 weeks and those that did not heal. This criterion should be independent of and replace other classification systems. A criterion for the proper choice of burn treatment would then be made more readily available.

A six-ring probe for monitoring conductivity changes.

This paper presents the construction of a six-ring probe for monitoring immittance changes. The spatial sensitivity of the probe is defined. This is used to examine the uniqueness of the probe in terms of its application to monitoring conductivity changes. A spatial distribution of the sensitivity is presented for isotropic and anisotropic cases. The latter case is restricted only to anisotropy met when measuring muscles, i.e. diagonal anisotropy. Theoretical calculations performed using the finite element method were verified experimentally using a specially developed measuring system. An example of in vivo measurements is included.