Which modality is most likely used to heat deep tissues?

• A. Short wave diathermy
• B. Infrared
• C. Ultraviolet
• D. Cold lasers

Answer: (C)

Deep-tissue heating depends on how far energy can penetrate into tissue. Short wave diathermy uses radiofrequency energy that penetrates several centimeters and is converted to heat inside muscles and other deep structures, making it the modality best suited for heating deep tissues. Infrared energy is mainly absorbed near the surface, so its heating is superficial rather than deep. Ultraviolet interacts primarily with the skin and drives photochemical effects rather than heating deep tissues. Cold lasers deliver light for photobiomodulation with minimal heating, not for heating deep tissues. So, for heating deep tissues, short wave diathermy is the most appropriate choice.