Final answer:
Requesting prior mammograms serves as an aid to radiologists by allowing them to compare changes over time, which can help in early detection of breast cancer and improve the accuracy of the examination.
Step-by-step explanation:
The purpose of requesting prior mammograms before starting the mammogram examination is primarily C. to provide the radiologist with an additional aid. Previous mammograms are extremely valuable when conducting a current breast imaging study as they allow the radiologist to compare any changes that may have occurred in the breast tissue over time. This comparison can help in detecting subtle differences or emerging patterns that may indicate the early stages of breast cancer development or other breast conditions. Also, having past images for reference can improve the accuracy of the examination and reduce the likelihood of false positives, providing a more detailed and accurate assessment for the patient's healthcare team.