Contact-free temperature determination is based on the measurements of electromagnetic radiation. The corresponding physical laws are related to the properties of black bodies. This background allows for the development of thermometric and thermographic systems for remote temperature measurements. Precise absolute temperature data, required in hyperthermia, do not only depend on the technical quality of the systems (hardware and software) and their calibration, but also depend on accurate determination of the emissivity of human skin. Pyrometers are restricted to temperature measurements within a small area (measurement spot), while thermographic cameras allow measurements across a relatively large region on the target area in real time. The subdivision of the IR image into spatially separated pixels allows access to temperature data of small areas on the skin and thus combines thermometry and thermography. Quality assurance standards of the European Society of Hyperthermic Oncology for water-filtered IR-A-hyperthermia (wIRA-HT) are met, except for the accuracy of the absolute temperature. Since the relation between the temperatures at the skin surface and in deeper tissue layers, considering irradiation and heating time, in wIRA-HT can be assessed, the temperature needed for efficient thermal treatment of superficial tumors within superficial tissue layers can therefore be achieved in a controlled manner.
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