Infrared thermography as applied to the studies of cardiovascular system in rats

Abstract

Fig. 1. A special shielding box equipped with mechanical support for infrared camera and universal rotating table for small laboratory animals. The infrared camera (TKVr-IFP/SVIT) is shown in the off (horizontal) position.Interventional FPA-based infrared thermography (IRT) [1] is applied to the investigation of transient cardiovascular reactions and blood flow change emerging in response to external mechanical and/or thermal impacts in laboratory albino rats. Synchronously with the infrared camera TKVr-IFP/SVIT, the technique enabling measurements of cardiac R-R intervals and heart rate variability [2] was applied as an alternative control method accompanying thermal imaging. Electrocardiogram (ECG) recording was realized using hardware and software system "Veda Puls" manufactured by LLC Biokvant (Novosibirsk, Russia). Sampling frequency of the ECG was 500 Hz.Narcotized laboratory rats were placed into the special box (figure 1) designed for IRT-based investigation of small animals and described in [1]. The use of this box helped us to avoid many bothering artefacts typical of highprecision thermal studies. Photograph (figure 2) and thermograms (figure 3) provide an insight into the typical setting accompanying the study. They demonstrate a rat undergoing the interventional IRT-based examination. We proposed and successfully tested the use of thermoelectric (Peltier) cooler as a convenient tool appropriate for a lot of physiological applications where a local heating or cooling of outer parts of an animal or human body is necessary.Local and systemic cardiovascular manifestations in rats were investigated in details. Vascular reactions were monitored during and after local and/or whole body heating, local cooling, crossclamping of the main vessels of a paw and creating artificial ischemia in the rat tail.Owing to quantitative FPA-based IRT, we were fortunate to disclose several intriguing physiological phenomena in rats. First of all, it was revealed that, even in the rat's calm sleeping condition, its blood supply exhibits activity which is not always definitely explainable. Figure 4 demonstrates temporal alterations in the temperature of different parts of the