How far inward should the superior and inferior margins be from the film margin in the collimation?

In radiographic practice, proper collimation is essential for achieving high-quality images while minimizing patient exposure to radiation. The correct inward margin from the film edge is typically set at 1 inch for both the superior and inferior margins. This standard reduces the excess exposure of surrounding tissues that are not of diagnostic interest, ensuring that only the area of interest is clearly imaged.

This guideline is based on established protocols in radiography, which aim to balance image quality with patient safety. A 1-inch margin allows for enough overlap of exposure to capture the necessary anatomical details without including unnecessary areas that could distort the image quality or increase radiation exposure.

Additionally, setting the margins too wide, such as 1.5 inches or more, may lead to increased scatter radiation and unnecessary exposure, while also producing images that might not be optimized for interpretation. Thus, the standard of 1 inch provides an effective compromise between sufficient coverage of the area of interest and minimizing radiation exposure.