Diagnostic thermography

Analysis of the density and distribution of entropy in biomedical infrared imaging for Diabetes Mellitus Type II

We report a methodology to analyze data extracted from infrared images. These pictures show the lower limbs of a cohort of individuals belonging to, (1) voluntary controls and (2) patients diagnosed with diabetes mellitus type II. The analysis is presented in terms of Cross Entropy and temperature distributions; both using the associated thermal histograms. The temperature analysis is placed in terms of comparing the extreme values ofdS/dQ, for controls and patients. In this analysis for the frontal view, the values of specificity and sensitivity calculated were 77.77% and 91.66%, respectively. For the back view, the specificity and sensitivity obtained were 88.8% and 83.3%, respectively. Instead of that, the cross-entropy analysis is placed in the modality of self-referencing. In this part of the study we obtained the coefficient of asymmetry and thermal response (ATR). The values of specificity and sensitivity for the ATR quotient in both cases were 83.3%. The results of both studies have a significant correlation with glucose (p< 0.01) and HbA1c (p< 0.01). It means that both approaches have statistical correspondence. By means of the Mann-Whitney U test, for independent samples, we get that the characteristic parameters we analyze can be differentiated among the populations of interest with a significance ofp< 0.05. This suggests that both studies show consistency with the clinical diagnosis; exhibiting clear differences between control and patient groups.

Novel methods of imaging and analysis for the thermoregulatory sweat test

The thermoregulatory sweat test (TST) can be central to the identification and management of disorders affecting sudomotor function and small sensory and autonomic nerve fibers, but the cumbersome nature of the standard testing protocol has prevented its widespread adoption. A high-resolution, quantitative, clean and simple assay of sweating could significantly improve identification and management of these disorders. Images from 89 clinical TSTs were analyzed retrospectively using two novel techniques. First, using the standard indicator powder, skin surface sweat distributions were determined algorithmically for each patient. Second, a fundamentally novel method using thermal imaging of forced evaporative cooling was evaluated through comparison with the standard technique. Correlation and receiver operating characteristic analyses were used to determine the degree of match between these methods, and the potential limits of thermal imaging were examined through cumulative analysis of all studied patients. Algorithmic encoding of sweating and nonsweating regions produces a more objective analysis for clinical decision-making. Additionally, results from the forced cooling method correspond well with those from indicator powder imaging, with a correlation across spatial regions of -0.78 (confidence interval: -0.84 to -0.71). The method works similarly across body regions, and frame-by-frame analysis suggests the ability to identify sweating regions within ~1 s of imaging. Although algorithmic encoding can enhance the standard sweat testing protocol, thermal imaging with forced evaporative cooling can dramatically improve the TST by making it less time consuming and more patient friendly than the current approach. NEW & NOTEWORTHY The thermoregulatory sweat test (TST) can be central to the identification and management of several common neurological disorders, but the cumbersome nature of the standard testing protocol has prevented its widespread adoption. In this study, images from 89 clinical TSTs were analyzed retrospectively using two novel techniques. Our results suggest that these improved methods could make sweat testing more reliable and acceptable for screening and management of a range of neurological disorders.

Thermography for skin temperature evaluation during dynamic exercise: a case study on an incremental maximal test in elite male cyclists

The use of thermal imaging in monitoring the dynamic of skin temperature during prolonged physical exercise is central to assess athletes' ability to dissipate heat from the skin surface to the environment. In this study, seven elite cyclists completed an incremental maximal cycling test to evaluate their skin temperature response under controlled-environment conditions. Thermal images have been analyzed using a method based on maxima detection (T_max). Data confirmed a reduction in skin temperature due to vasoconstriction during the exercise, followed by a temperature increment after exhaustion. A characteristic hot-spotted thermal pattern was found over the skin surface in all subjects. This research confirmed also the notable ability by highly trained cyclists to modify skin temperature during an incremental muscular effort. This study gives additional contributions for understanding the capability of the T_max method applied to the thermoregulatory physiological processes.

Assessment of Tissue Viability by Thermography after Experimentally Produced Frostbite of the Rabbit Ear

Since it is difficult and time-consuming to monitor the formation of a demarcation line in frostbite by visual inspection only, thermography was used to study experimental freezing injuries of the rabbit ear. In 8 rabbits, anesthetized with ketamine hydrochloride and xylazine hydrochloride, frostbite was induced by pressing the bottom of a glass bottle 2 cm in diameter, filled with liquid nitrogen against the shaved ear skin. Thermography was performed on both ears after 2, 24, and 48 hours, and one and 3 weeks. At 2 to 48 hours the frostbitten area was clearly warmer than the surroundings, after one week there were ill-defined diffuse cold spots in the injured area, and after 3 weeks a cold area had become clearly demarcated with a warm zone between the cold area and the surroundings. Thermography is an easy, noninvasive method for monitoring thermal changes after experimental frostbite, but its clinical value is as yet unresolved.

Usefulness of thermography techniques for evaluating the disease activity in Kimura's disease

Kimura's disease (KD) is a rare, chronic inflammatory disorder predominantly affecting the head and neck. A case of KD in a 30-year-old man is reported. Thermography was useful for evaluating the activity of the condition.

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.

Thermography in lower limb arterial disease

Skin temperature distributions are described which correspond to different levels of arterial obstruction in the lower limbs. These temperature distributions are conveniently observed using thermography. Thermography may be used to measure the change in skin temperature when the limb performs work. These skin temperature changes have been correlated with the impairment of blood flow to the lower limb.

A novel means of thermal imaging

A simple and inexpensive imaging device is described adaptable to ir, microwave, or ultrasound radiation. An image is projected on a heat-sensitive surface which expands in proportion to the intensity of the radiation. The resulting bas-relief is recorded by double exposure holography.