At what power level may patients with normal thermal regulation suffer tissue damage?

The correct choice, which reflects the power level at which patients with normal thermal regulation may begin to suffer tissue damage, is based on established safety limits in Magnetic Resonance Imaging (MRI). When looking at these power levels, 240 W-min/kg (14440 J/kg) indicates a threshold of energy deposition that, when exceeded, can lead to damaging thermal effects in body tissues, especially under prolonged exposure.

The potential for thermal injury arises because, at this energy level, the body’s standard mechanisms for dissipating heat might not be sufficient to counteract the additional heat generated within tissues by the MRI system. Normal thermal regulation typically refers to the body's ability to maintain a stable temperature, and when the energy deposition exceeds the biological tolerances, it can lead to overheating and subsequent tissue damage.

The other options represent lower energy deposition thresholds, which are understood to be below the critical limit where significant tissue damage could occur. Thus, they do not pose the same level of risk as the correct choice, which indicates a recognized point where thermal safety concerns must be actively monitored in clinical settings.