Temperaturmessung mittels Wärmebildkamera, als Refinement an der Nacktmaus
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Beschreibung
Temperature measurement with the Infrared camera in adult nude mice - Refinement
Established methods of measuring body temperature are typically invasive, and may cause mice discomfort and stress. The objective of the study was to compare a non-invasive qualitative thermography with the established invasive temperature measurement methods in nude mice.
In this study, the qualitative thermography of an individual and of group-housed nude mice, showed that this method is suitable for measuring the radiated thermal energy (thermal radiation), and for detecting select physiological conditions which result in a change of skin temperature, i.e. bodyweight. An accurate identification using thermal imagery in a grouphoused mouse, is not possible even if additional digital imagery is used for identifying individual animals.
Use of qualitative thermograms in group-housed mice is suitable for continuous or repeat visualisation of an individual mouse, as it enables clear differentiation of certain physiological conditions from other animals within that group. The radiated thermal energy of nude mice in the group can be visualised using a qualitative thermogram model infrared camera (IRC) FLIR E40.
Quantitative thermography is a practical method for the non-tactile and non-invasive
measurement of the temperature of nude mice within physiological ranges. The present study found that a temperature value from a minimum of 10 thermograms should be used for a quantitative measurement. Based on the findings of quantitative thermography, it can be assumed that thermographically measured skin temperatures are not an overestimate. The highest, maximum measured temperature value (irT-max) of all thermograms is the one that most accurately reflects the actual skin temperature. The study results clearly demonstrate that the highest irT-max ever recorded from all thermograms of one quantitative measurement should be used rather than the average of all temperatures recorded, or the average of irTmax of one individual thermogram.
The thermographic measurements of 4 female BALB/cAnN-Foxn1nu/nu/Rj mice with different body weights, the measurement of the 50 male Rj:NMRI-Foxn1nu/nu mice and the multiple measurements of the 20 BALB/cAnN-Foxn1nu/nu / Rj male mice over a prolonged period of time demonstrate practical and easy deployment of the thermal imaging.
The infrared camera FLIR E40 used for quantitative thermograms has a larger measuring spot size and a lower resolution and quality compared to other infrared cameras that we have evaluated. The high-quality thermal imaging camera FLIR T660 was used to compare the different temperature measurement methods. A smaller size of the measuring spot with infrared camera FLIR T660 made it possible to obtain higher quality irT results as compared to the infrared camera FLIR E40 model. However, automatic focusing is controversial in some areas of research due to the minimal differential between environmental and mouse temperature.
This study shows that the auto focus function of the infrared camera FLIR T660 model requires the use of a tripod to prevent vibrations caused by the user, and to ensure high-quality temperature results. Use of a tripod enables focus in a constant plane to generate accurate thermographic measurement in nude mice. The high recording frequency of infrared camera FLIR T660 model, enables radiometric autofocused video recordings, even when the mouse is moving.
Thermography is a non-invasive method compared to established temperature measurement methods. The thermal imaging camera is a stress-free measuring device, avoiding surgical intervention, or physical restraint and placement of a foreign object in mice.
In our study we have compared IRC with other more invasive methods, the intra-rectal temperature probe, subcutaneous temperature transponders and intra-peritoneal data loggers.
Intra-rectal temperature measurements with model 5885, Precision Digital Thermometer with PRT [platinum resistance thermometer] (H Tinsley, New Addington, United Kingdom) probe should be interpreted carefully, as the handling during insertion of the temperature probe tip may result in complications, or modulated response due to stress.
Subcutaneous temperature transponders using IPTT-100 (Bio Medic Data Systems, Seaford, DE) also enable individual identification and are useful for some experiments, but transponders must be temperature calibrated.
Intra-peritoneal data loggers we used should have the advantage of providing continuous temperature measurement, however with DST Nano–T Temperature Recorder (Starr Oddi, Gardabaer, Iceland) the results of software analysis can only be extracted at the end of experiment.
The comparative study results demonstrate that the thermal imager is as accurate as the intrarectal and subcutaneous temperature measurement methods in nude mice. The infrared skin temperature is a valid and accurate method, comparable to rectal and subcutaneous temperature measurements.
In summary, the highly efficient, non-invasive method of infra-red thermography is a refinement compared to other more invasive temperature measurement methods. The method can detect deficit in body condition, i.e. bodyweight of nude mice. Qualitative infrared thermography is a suitable refinement method which primary aim is the assessment of surface temperature through capture of thermal radiation emitted by nude mice, and secondarily, for qualitative assessment of overall health status and well-being of animals.
In addition, quantitative thermography application can measure reproducibly the temperatures of nude mice in physiological temperature ranges without contact and non-invasively. In nude mice, thermography is non-invasive compared to established temperature measurement methods (rectal, subcutaneous, and intraperitoneal) and with the same measurement accuracy. A substitute for the temperature detection commonly used in various studies by the non-invasive method should always be considered.
Temperature measurement using thermography, as a non-invasive method, is an improvement over established methods because it is not associated with physical restraint or the risk of physical damage and subsequent infection. In the context of our studies, this measurement method proved to be safe and accurate for temperature and well-being assessment in nude mice.
Autor*in
Kerstin Fiebig
Themen in »Temperaturmessung mittels Wärmebildkamera, als Refinement an der Nacktmaus«
Infrarot-Wärmebildtechnik Körpertemperatur Labortiere Mäuse Tierschutz Wärme-Infrarot-Bilder animal welfare body temperature diagnostic techniques diagnostische Verfahren laboratory animals mice thermal infrared imagery