1 Introduction

Tissue heating by water-filtered infrared A radiation (wIRA) is based on interactions between radiation and tissues. wIRA-hyperthermia (wIRA-HT) requires an interdisciplinary approach involving photobiological principles and laws, (patho-)physiological tissue responses, and the needs of proper dosimetry. Thus, an exact terminology is crucial to prevent interdisciplinary misunderstanding and to be consistent with the International System of Units (SI). Science-based terms are also the key for traceability and comparability of measured data published by different authors and to prevent misconceptions and confusion of readers/users due to imprecise vocabulary or different denominations of identical parameters. Therefore, a glossary of basic physical terms and of SI-based radiometry units is proposed for consistent use in wIRA-HT. Also provided are terms defined by the European Society of Hyperthermic Oncology (ESHO) which are currently recommended for quality proof of superficial hyperthermia in oncology, and empirical, basic data for wIRA skin exposures in radiation oncology and in physical therapy (Tables 1.1, 1.2, 1.3, 1.4, 1.5, 1.7 and Figs. 1.1, and 1.2).

2 Recommended Terms

Table 1.1 Terms and tools to characterize the spectrum of infrared radiation [1,2,3]
Table 1.2 Terms and parameters to characterize wIRA emitted by a device and incident on the surface of the exposed object [2,3,4,5,6,7]
Table 1.3 Terms quantifying interactions of wIRA with tissues [2,3,4,5,6,7]
Table 1.4 Terms quantifying propagation of wIRA within tissues [2,3,4,5,6,7]
Table 1.5 Terms quantifying optical and thermal properties and thermal response of tissues

3 Occasionally Used, Obsolete, and Non-Recommended Terms

Table 1.6 Examples

4 Empirical and Basic Data for wIRA Skin Exposures in Radiation Oncology and in Physical Therapy [8, 10,11,12,13]

4.1 Main Characteristics

Table 1.7 Performance of effective wIRA-hyperthermia (wIRA-HT) in the clinical setting

4.2 Heating-up Times Necessary to Reach Thermal Steady-State Temperatures During wIRA-Hyperthermia in Normal Tissues [13]

Fig. 1.1
figure 1

Mean values and standard deviations of heating-up times necessary to reach steady-state temperatures in the abdominal wall and lumbar region as a function of tissue depth. wIRA skin-exposure using an incident irradiance of 135 mW cm−2 (IR-A) [13]

4.3 Mean Steady-State Temperatures During wIRA-Hyperthermia in Normal Tissues and Human Cancers [11,12,13]

Fig. 1.2
figure 2

Mean steady-state tissue temperatures during wIRA-HT as a function of tissue depth. Irradiances used for heating of different human tissues: 110–135 mW cm−2. Data assessed in recurrent breast cancer (dots [11]), in various human tumors (triangles [12]), and in abdominal wall and lumbar region (squares [13]). Broken line: extrapolation of the best-fit line (solid). HT levels ≥39 °C: local increase in perfusion, tissue oxygenation, and vascular permeability; stimulation of antitumor immune responses, and fostering of abscopal immune responses (local effects within tissue depths of 0 mm to approx. 26 mm, green border). HT levels ≥40 °C: optimal temperature levels for thermo-chemotherapy with little additional increase of sensitization >42 °C (within tissue depths of 0 mm to about 17 mm, blue border). HT levels ≥41 °C: tissue temperatures necessary to inhibit DNA repair (double-strand breaks, within tissue depths of 0 mm to about 8 mm, red border). Tissue temperatures ≥43 °C for longer treatment times are mandatory for direct cytotoxicity