Temperature measurement on tissue surface during laser irradiation

Tissue surface temperature distribution on the treatment site can serve as an indicator for the effectiveness of a photothermal therapy. In this study, both infrared thermography and theoretical simulation were used to determine the surface temperature distribution during laser irradiation of both gel phantom and animal tumors. Selective photothermal interaction was attempted by using intratumoral indocyanine green enhancement and irradiation via a near-infrared laser. An immunoadjuvant was also used to enhance immunological responses during tumor treatment. Monte Carlo method for tissue absorption of light and finite difference method for heat diffusion in tissue were used to simulate the temperature distribution during the selective laser photothermal interaction. An infrared camera was used to capture the thermal images during the laser treatment and the surface temperature was determined. Our findings show that the theoretical and experimental results are in good agreement and that the surface temperature of irradiated tissue can be controlled with appropriate dye and adjuvant enhancement. These results can be used to control the laser tumor treatment parameters and to optimize the treatment outcome. More importantly, when used with immunotherapy as a precursor of immunological responses, the selective photothermal treatment can be guided by the tissue temperature profiles both in the tumor and on the surface.     

An Evaluation of 3D-Printed Materials’ Structural Properties Using Active Infrared Thermography and Deep Neural Networks Trained on the Numerical Data

This article describes an approach to evaluating the structural properties of samples manufactured through 3D printing via active infrared thermography. The mentioned technique was used to test the PETG sample, using halogen lamps as an excitation source. First, a simplified, general numerical model of the phenomenon was prepared; then, the obtained data were used in a process of the deep neural network training. Finally, the network trained in this manner was used for the material evaluation on the basis of the original experimental data. The described methodology allows for the automated assessment of the structural state of 3D−printed materials. The usage of a generalized model is an innovative method that allows for greater product assessment flexibility.     

Inverse method for quantitative characterisation of breast tumours from surface temperature data

Purpose: We introduce a computational method to simultaneously estimate size, location and blood perfusion of the cancerous breast lesion from the surface temperature data.

Methods: A 2D computational phantom of axisymmetric tumorous breast with six tissue layers, epidermis, papillary dermis, reticular dermis, fat, gland, muscle layer and spherical tumour was used to generate surface temperature distribution and thereby estimate tumour characteristics iteratively using an inverse algorithm based on Levenberg–Marquardt method. In addition to the steady state temperature data, we modified and expanded the inverse algorithm to include transient data that can be captured by dynamic infra-red imaging. Several test cases were considered for the transient analysis, where the depth, radii and blood perfusion of tumour were varied from 11 to 30?mm, 7 to 11?mm and 0.003 to 0.01 1/s, respectively.

Results: Similar steady state temperature profile for different tumours makes it impossible to simultaneously estimate blood perfusion, size and location of tumour using steady state data alone. This becomes possible when transient data are used along with steady state data. For the cases discussed here, the estimates have errors below 1% for tumours with depths less than 20?mm, but for deeper tumours (25?mm) errors can be more than 10%.

Conclusions: Combination of transient data and steady state data makes it possible to simultaneously estimate tumour size, location and blood perfusion. Blood perfusion is an indicator of the growth rate of the tumour and therefore its evaluation can possibly lead to the assessment of tumour malignancy.     

Pilot study: Utility of long-wave infrared thermography as a correlate to transcutaneous oximetry for candidates of hyperbaric oxygen therapy

Hyperbaric oxygen (HBO₂) has been used as an adjunctive treatment for the care of advanced non-healing diabetic foot ulcers (DFUs). A patient's in-chamber transcutaneous oximetry measurement (TCOM) is currently the most effective predictor for response to HBO₂ therapy but still excludes close to one in four patients who would benefit out of treatment groups when used for patient selection. Improving selection tools and criteria could potentially help better demonstrate HBO₂ therapy's efficacy for such patients. We sought to identify if long-wave infrared thermography (LWIT) measurements held any correlation with a patient's TCOM measurements and if LWIT could be used in a response prediction role for adjunctive HBO₂ therapy. To investigate, 24 patients already receiving TCOM measurements were enrolled to simultaneously be imaged with LWIT. LWIT measurements were taken throughout each patient's therapeutic course whether they underwent only standard wound care or adjunctive HBO₂ treatments. A significant correlation was found between in-chamber TCOM and post-HBO₂ LWIT. There was also a significant difference in the post-HBO₂ LWIT measurement from 1st treatment to 6 weeks or the last treatment recorded. These initial findings are important as they indicate a possible clinical use for LWIT in the selection process for patients for HBO₂ therapy. Larger studies should be carried out to further articulate the clinical use of LWIT in this capacity.     

Infrared thermography in the diagnosis of palmar hyperhidrosis: A diagnostic study

BackgroundPrimary hyperhidrosis is a common condition affecting 1–3% of the general population. Excessive sweating leads to reduced surface temperature due to evaporation that can be captured using a thermal camera. We performed this study to find the utility of thermography in the diagnosis of palmar hyperhidrosis.MethodsThis was a cross-sectional diagnostic study conducted in a tertiary care dermatology center during the study period Apr 20–Mar 21. Adult patients with palmar hyperhidrosis diagnosed by expert dermatologists were recruited. The severity was assessed using the hyperhidrosis disease severity scale (HDSS). The measurements were done using a FLIR™ thermal camera. A pilot study, including 30 patients and 30 controls were performed. The results of the pilot study were used for the calculation of sample size.ResultThe study included 55 patients and 110 controls. The mean age of the patients and controls was 22.4 (±3) years and 21.7 (±2.5) years, respectively. The mean temperature difference in the patient and control group was found to be 19.6 (±3.3)⁰ F and 5.8 (±2.9)⁰ F, respectively (p < 0.001). A receiver operating characteristics curve (ROC) to assess the discriminatory ability of mean temperature difference in diagnosis of hyperhidrosis found the area under the curve (AUC) to be 0.995 and a temperature difference of 11.5 °F provides sensitivity and specificity of 98.2% and 97.3% for the diagnosis of hyperhidrosis.ConclusionsThermal imaging is a simple, noninvasive, and objective tool for the diagnosis of hyperhidrosis. It has potential utility in monitoring the effect of the treatment.     

Smartphone-based infrared thermography to assess progress in thoracic surgical incision healing: A preliminary study

Immediate assessment of surgical incisions is an important component of wound management, and the development of relevant technologies has the potential to address these challenges. Smartphone-based handheld thermal imagers can collect infrared radiation from the skin to monitor local blood perfusion and metabolic levels in incisions. Here, we used this imaging technology for early assessment of healing progress and potential for predicting the healing status of thoracic surgical incisions. Thermal image acquisition and temperature extraction were performed on 40 patients for 7 consecutive days postoperatively, and visualised early warning information was observed, with temperature and temperature readings showing non-linear trajectory changes during the measurement period, and temperature readings on day 4 achieving high prediction of healing status at 1–2 months capability with sensitivities and specificities of 91.67% and 85.71%, respectively, suggesting a promising clinical application of portable thermography for assessing incision healing dynamics and providing a scientific basis for later artificial intelligence-driven decision algorithms.     

Does the skin heat up before it breaks down in diabetic foot ulceration?

Aims

Most diabetic foot ulcers are caused by tissue stress from being ambulatory in people without protective sensation. These ulcers are suggested to be preceded by local skin temperature increase due to inflammation of the underlying tissue, a so-called hotspot. Evidence to support this mechanism of ulcer development is meagre at best. We investigated if foot ulcers are preceded by increased skin temperature in people with diabetes and foot ulcer history.

Material and Methods

Participants measured temperature at 6–8 plantar foot locations each day for 18 months and identified a hotspot with a temperature difference >2.2°C between corresponding foot locations for two consecutive days.

Results

Twenty-nine of 151 participants developed a non-traumatic ulcer while adhering to temperature measurements. In the 2 months prior to ulceration, 8 (28%) had a true hotspot (i.e. at/adjacent to the ulcer location) and the hotspot was on average no longer present 9 days before ulceration. Seven (24%) participants had a false hotspot (i.e. at another location) and 14 (48%) had no hotspot.

Conclusions

The skin of the majority of the ulcers does not heat up before it breaks down or, when it does, not directly before breakdown, questioning the foot temperature increase—uslcer association.