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CHAPTER 8

Hyperthermia and ablation

8.1 Thermotherapy methods
Thermal therapy medical procedures rely on either raising or lowering the local tem-
perature in tissues with healing aims. In the hyperthermia group, the emerging radio-
frequency (RF) and microwave (MW) hyperthermic procedures are used in breast
cancer detection and the angioplasty, in the ablation of the liver and heart, benign
prostate hypertrophy (Westermark, 1989; Rosen and Rosen, 1995; Rosen et al.,
2002), and the enumeration may continue (Dahl et al., 1995; Habash et al., 2006).
Current researches on the thermal therapy-related biological effects (Michaelson and
Lin, 1987) are concerned with the viability of the tumor cells decreases when exposed
to even lukewarm elevated temperatures, which yields them sensitive to radiation and
chemotherapy (Horsman and Overgaard, 2007; Poulou et al., 2015; Ryu et al., 2004).
External applicators are positioned either near or around the region of interest (ROI),
inserted through the skin or just below its surface, and power is focused on the tumor
to increase or decrease its temperature, and either heating or cooling of the targeted
area, such as a tumor, is produced using various methods. Different types of power
sources may be used, of which electromagnetic field (EMF) sources, ultrasound sources
(US), and cryogenic sinks (CS) are most common. Medical thermal applications based
on EMF power sources (Rosen and Rosen, 1995; Strezer, 2002; Vander Vorst et al.,
2006) concern a wide range of therapeutic effects, with some existing variability in
thermal therapy methodology (Stauffer and Goldberg, 2004). The dosage of the para-
meters (exposure time, intensity) distinguishes between hyperthermia therapy and
ablation (surgery). The heating of tissue depends on the properties of the EMF source,
its frequency, the heat transfer properties of the tissues, and their vascularization.

Hyperthermia
General hyperthermia methods are nonfocused and thus have limited ability to deliver a uni-
form, sufficient thermal dose to metastases, which limits its clinical efficacy. However, they
are particularly successful as an antineoplastic agent used in the treatment for intraperito-
neal metastases from ovarian tumors, increasing the efficacy of certain chemotherapeutics
(Ryu et al., 2004; Wust et al., 2003). According to the National Cancer Institute classifica-
tion (NIH), in hyperthermia (or thermal therapy or thermotherapy) body tissue is exposed
to temperatures high enough (up to 45 C or 113 F) to damage the proteins and the

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DOI: https://doi.org/10.1016/B978-0-12-817897-3.00008-7 All rights reserved. 249