# Quantification of the Area of the Highest Temperature in
## 1 Introduction
The main advantage of infrared thermography (IRT) is that it is contactless for the patient, enabling its use even in wildlife [1; 2; 20; 21]. In equine medicine, IRT can be used as a diagnostic tool to detect inflammatory areas, e.g., on the back [3; 22] or limbs [3; 23; 24; 25] and during pregnancy [26]. Measurements of surface temperatures can also be used to improve the welfare of leisure and sport horses [21; 27; 28], as well as enhance athletic performance by evaluating the adaptation of training methods to individuals [3; 29; 30]. Importantly, this diagnostic tool allows for multiple examinations as IRT is relatively easy to conduct and completely harmless for imaged animals [2; 3; 24]. Unfortunately, besides these advantages, there are limitations on the use of IRT in equine medicine. Achieving reliable results for both infrared image acquisition and image processing may prove difficult. The quality of hardware, user experience and knowledge, proper animal preparation, and environmental conditions affect image acquisition [21; 24; 21]. As there are multiple thermographic cameras on the market, it is not certain that all will provide similar quality results. Cheaper, more available cameras can have a larger margin of error and lower image resolution [24]. Human-dependent factors can also play a role in imaging domestic animals; for the highest quality infrared images, animals should be properly prepared by cleaning, grooming, and brushing [4; 24; 31; 32]. The major challenge of image processing is to apply regions of interest (ROIs) on infrared images, which is crucial for numerical data extraction (ROI quantification) and comparisons between regions on both sides of an animal [1; 2; 20; 33; 34]. Most commercial software allows for an application of ROIs, which are circular, rectangular, or linear; however, undoubtedly, they are not adequate for all body regions or groups of muscles, as a horse's surface demonstrates a complex, irregular shape. Recently developed software enables the quantification of irregular shapes. Yet, still, infrared image segmentation [35] and the development of a new quantification method [21; 22; 33; 34; 36] have been the object of recent research to achieve a particular aim, which is extracting more data from IRT to human [35] and veterinary [21; 22; 33; 34; 36] diagnostics than that currently available [3; 21; 24; 26; 31]. Several studies regarding veterinary medicine applications have focused on measurements of the area with the highest temperature (Area of Tmax) [26; 31]. Such an approach may enable the evaluation of a horse's health and condition in a more comprehensive manner. The activation of brown adipose tissue, important in thermogenesis, can be informative for wild equids housed in activity, free-range horses, or foals, in which many processes are not fully developed yet. General thermogenesis efficiency can be assessed using infrared images [1; 28; 37; 38]. It is important to assess whether peripheral body areas are set to emit more heat, or to decrease emissions by the constriction of peripheral vessels, as both processes require energy and can decrease animal welfare [27; 28]. The Area of Tmax can be also used in assessing changes in thermogenesis associated with age, development of the process in foals, but also gradual decreases in thermoregulation effectiveness in older horses [10; 17; 39; 40; 41]. The Area of Tmax was proposed as a feature helpful in pregnancy diagnosis in late gestation; however, this was only applicable in a range of 3 \({}^{\circ}\)C [2]. As previous results were promising, an adaptation of and improvement in the Area of Tmax-dependent method are proposed here in order to improve its usage in equine medicine. Especially regarding the evaluation of individual nutritional requirements, there is a need to develop an easy and repeatable method for a thermoregulation expenses assessment. Thus, the goal is to facilitate thermography to increase the applicability, repeatability, and specificity of the Area of Tmax method, as well as thermography itself.