Introduction to Physical Agents for Physical Therapist Assistant (PTA) Practice Test

Heat transfer by radiation moves energy through electromagnetic waves, so direct contact with the tissue isn’t needed. The rate at which tissue temperature rises depends on how much energy the device delivers (intensity) and how far the tissue is from the energy source. Higher intensity delivers more energy and heats faster; greater distance means the energy reaching the tissue is reduced, so heating is slower. This is why clinicians adjust distance and duration to control warming and protect surrounding tissues. Radiation can be targeted to different depths and areas with the right applicator, so it isn’t limited to heating only large body regions. It’s also a controllable modality, not an uncontrolled one.