Say one's going to take an x-ray of the head or foot. Is it the common practice that the patient would wear some protective vest or barrier, leaving out only the part that needs to be photographed by x-rays? I was wondering if there wouldn't be some "optical"/wave effect leading to a sharper concentration at the edges of the vest/barrier, sort of a "funnel"* to some degree, which in turn would perhaps be worse than the same total radiation spread all over the body, or wherever it reaches nearby. Is there really such "optical" effect, when light/radiation go through a hole? * probably that's not the best analogy for the effect, if it really exists. I don't mean that all the x-rays somehow manage to get into the "funnel"/hole, but that perhaps they'd "concentrate" somewhat more at the edges, perhaps depending on the size of that barrier.