Which anatomical structure should be positioned over the AEC chamber for optimal receptor exposure?

The optimal positioning of the anatomical structure over the AEC (Automatic Exposure Control) chamber is to place the structure of primary concern directly over it. The AEC system relies on sensing the amount of radiation reaching the receptor to determine when to terminate the exposure. Positioning the most critical structure ensures that the AEC effectively calculates the exposure time based on the specific density and attenuation of that structure.

For instance, if a critical area is being examined, the AEC will adjust the exposure to provide sufficient detail for that structure, thereby achieving ideal receptor exposure. This correlates with the principle that the area needing the most accurate representation should be prioritized in exposure calculations.

In contrast, focusing on structures of least concern, highest density, or lowest density could result in inadequate exposure for the primary area of interest, leading to either underexposure or overexposure of the critical region. Therefore, to achieve the best diagnostic image quality and ensure that the important anatomy is adequately visualized, the structure of primary concern must be positioned over the AEC chamber.