A new method of image processing for high-contrast medical infrared imaging of the horse

Abstract

Infrared (IR) imaging for medical diagnostics generally requires indication-specific and standardised imaging and image processing. Spatial resolution, thermal sensitivity, and image contrast require optimization. Improved contrast, in particular, and the optimum utilisation of thermodynamic variables greatly influence the diagnostic utility of the images. Medical IR imaging challenges arise mainly from external influences, such as: ambient temperature, humidity, examination room air flow, heat radiation received by the room, and certain types of illumination, all of which, if not controlled, may produce misleading results. Also of practical relevance are patien-trelated factors, such as: the body core temperature, blood flow (heart frequency, blood pressure, vascular tone) and, if applicable, the evaporative heat loss from sweat on the skin. All influence the temperature distribution pattern. In veterinary applications there is the added problem of the thermal insulation effect of the fur (fur length, fur density, fur type). The measurement of temperature differences or gradients is of primary diagnostic relevance, not the measurement of absolute temperature values of the skin or fur, because of the large physiological variation. Physiological variation results primarily from patient-specific parameters, such as: the heart beat frequency, vascular tone, metabolism and ambient temperature. A key part of our research was the development of a new relief image process for processing of medical infrared thermographic images in the wavelength range of 8 to 12 μm. For the diagnostic imaging of equine nasal passages, it shows a significantly improved image contrast compared to conventional IR images. Our process could, for example, facilitate the diagnosis of neoplastic as well as inflammatory processes on a horse's head. By exploiting physical conditions, the details of the nasal passages of the horse's head (the nasal septum, tubuli nasi, and probably diverticuli nasi) can thus be made visible by means of infrared imaging.