What happens to the skin dose when the TPD is shorter?

When the target-to-skin distance (TPD) is shorter, the skin dose increases due to the inverse square law, which states that the intensity of radiation delivered to a surface is inversely proportional to the square of the distance from the radiation source to that surface. In practical terms, when the source of radiation is closer to the skin, the radiation has less space to spread out, which means that the intensity delivered to the skin is higher.

As a result, with a shorter TPD, more radiation reaches the skin, leading to an increased skin dose. This is particularly important in fluoroscopy and radiographic practices, as operators must be aware of the relationship between distance and dose to minimize patient exposure while ensuring effective imaging. Understanding this principle is essential for making informed decisions about equipment placement, positioning, and overall radiation safety practices in medical imaging.