A Comparison Between the Heating Process of the Therapeutic Ultrasound and Infrared Radiation Applied in Physical Therapy Using PVCP Phantoms

This paper aims to compare the so-called superficial heating methods used in Physical Therapy by comparing the therapeutic ultrasound and the infrared radiation, both considered superficial thermotherapeutic equipment. Thermotherapy is a therapeutic modality that promotes several health benefits. However, there are gaps in scientific knowledge regarding these techniques when applied to physical therapy and its clinical use. So, a Polyvinylchloride plastisol phantom was used to mimic the acoustic properties of soft tissues. The experimental setup was composed of a 3-MHz ultrasound equipment, and an infrared lamp. In the ultrasound protocol the nominal intensity of 1.0 W/cm², continuous mode was applied during one minute (n = 10). In the infrared protocol, the phantom was positioned 30 cm apart from the infrared lamp during 15 min (n = 10). The infrared camera remained fixed in both protocols. After comparing the heating protocols, it was observed that the infrared radiation predominantly heated the upper surface of the phantom as it was directly irradiated by the lamp. The heat was probably transferred to the deeper and adjacent layers by conduction. The ultrasound radiation at 3 MHz, heated deeper sites of the phantom than the infrared radiation and had a predominantly heating pattern along the propagation axis of the ultrasonic beam, (i.e. in the central region of the phantom). The heating pattern contributes to understand the difference between both methods, and this work proposes a new approach to superficial heating studies related to physiotherapy equipment, an area that deserves more attention of the physical principles used in the clinic.