What is the maximum number of heat units the tube can absorb, according to the illustration?

What is the maximum number of heat units the tube can absorb, according to the illustration?

• A. 120,000 HU
• B. 240,000 HU
• C. 360,000 HU
• D. 480,000 HU

Answer: (B)

Heat units measure how much energy the x‑ray tube’s anode can safely absorb as heat during an exposure. The tube has a finite heat capacity, so the exposure factors (kVp, mA, and time) must stay within that limit. The illustration shows the safe-load limit for a single exposure at 240,000 heat units. That means you can’t exceed 240,000 HU in one exposure without risking overheating the anode. The other values fall outside the depicted safe limit on the chart (either below or above the indicated capacity), so the correct maximum, as shown, is 240,000 HU. If you need more exposure, you’d need to break it into multiple exposures with cooling time in between.

Heat units measure how much energy the x‑ray tube’s anode can safely absorb as heat during an exposure. The tube has a finite heat capacity, so the exposure factors (kVp, mA, and time) must stay within that limit. The illustration shows the safe-load limit for a single exposure at 240,000 heat units. That means you can’t exceed 240,000 HU in one exposure without risking overheating the anode. The other values fall outside the depicted safe limit on the chart (either below or above the indicated capacity), so the correct maximum, as shown, is 240,000 HU. If you need more exposure, you’d need to break it into multiple exposures with cooling time in between.