Final answer:
If the AEC is positioned over the petrous ridges, the rest of the skull X-ray will likely be overexposed. This happens because the petrous ridges are very dense, leading the AEC to set a higher exposure than needed for the rest of the skull, which can diminish image quality.
Step-by-step explanation:
If the Automatic Exposure Control (AEC) is over the petrous ridges for a skull X-ray, the rest of the image will likely appear overexposed. This is because the petrous part of the temporal bone is one of the densest parts of the skull and if the AEC is positioned over it, it will likely result in a higher exposure setting than needed for the rest of the skull. This overexposure can lead to a reduced image quality and potentially lessen the diagnostic value of the X-ray. In medical imaging, a balance is needed to obtain the necessary diagnostic information while minimizing the exposure to X-rays, since overexposure to X-rays can increase the risk of cancer, though when used in controlled doses, X-rays are a vital tool for imaging internal body parts.