Source to Image Distance (SID) - Video Lesson

Welcome back. This lesson is the fourth in a series about the prime exposure factors. Here, we're going to be talking about distance. I'm sure you understand by now. There are four prime exposure factors, MA, exposure time, KVP and distance. We call these the prime exposure factors because they are the most basic variable influencing the intensity of the beam and the exposure to the image receptor, and distance definitely plays an important role. The relationship between distance and exposure is very simple. If we increase the distance between the x-ray source and the image receptor, This results in a decrease in beam intensity at the level of the receptor, and therefore a decrease in the receptor exposure. So here's why that happens. Remember that the X-ray beam is divergent. This means that