Which of the following exams would produce the least amount of heat units and require the shortest anode cooling time?

The correct answer is based on the principle that different radiographic exams produce varying amounts of heat units depending on the number of images taken and the radiation exposure required for each view.

The posteroanterior (PA) hand exam for a bone age study typically involves only one standard view. This limited amount of exposure results in fewer heat units generated by the x-ray tube. Since the procedure requires a single radiograph, the anode has to dissipate significantly less heat compared to exams that involve multiple views, like a 3-view lumbar spine series or an adult bone survey, which includes several different images of various body parts.

The other options involve multiple x-ray views or larger anatomy that requires higher exposure levels, leading to an increase in heat generated during those procedures. Consequently, these exams necessitate longer cooling times for the anode due to the greater heat buildup.

Therefore, the single posteroanterior hand x-ray requires the least heat units and, by extension, the shortest anode cooling time, making it the most efficient option among those presented.