A lower BNR indicates:

• A. The higher the BN R, the more uniform the energy distribution
• B. The more uniform the energy distribution, the less risk of tissue damage
• C. The energy distribution does not affect tissue damage
• D. The greater the total energy, the higher the risk of tissue damage

Answer: (B)

Lower BNR means the beam’s energy is more evenly distributed across its cross-section. BNR, the ratio of the maximum intensity to the average intensity, drops when there are fewer or less pronounced peaks. That means energy is spread more uniformly, so there are fewer localized hot spots that can overheat or injure tissue. With high nonuniformity, those hot spots can cause greater tissue heating even if the average energy is the same, increasing the risk of damage. So, a more uniform energy distribution lowers the risk of tissue injury associated with the beam.