Specific absorption rate measures what?

• A. Rate of energy absorption per unit area tissue
• B. Temperature rise per minute
• C. Total energy delivered
• D. Power output of the device

Answer: (A)

Specific absorption rate describes how fast RF energy is taken up by tissue. It focuses on the rate of energy absorption rather than the total energy delivered or the device's power. The option that mirrors this idea by referring to energy absorbed per unit area of tissue captures the notion of a rate of absorption across the tissue surface. Temperature rise per minute depends on cooling and perfusion and isn’t the absorption rate itself; total energy delivered is the amount accumulated over time, not the rate; and the device’s power output is about what the source can emit, not what the tissue ends up absorbing. (In many contexts SAR is expressed in terms of energy absorbed per unit mass, but the core concept remains the rate at which energy is absorbed by tissue.)