Final answer:
At a fixed value of mAs and proper exposure, consistent image quality is maintained and patient radiation exposure is minimized. Shielding and fast films further reduce unnecessary exposure, while therapeutic radiation doses are carefully calculated to be within safe limits.
Step-by-step explanation:
At a fixed value of mAs and proper exposure on an average patient, the amount of radiation that reaches the tissues is maintained to ensure satisfactory image quality while minimizing the risk to the patient. This means the combination of milliamperes (mA) and the exposure time in seconds (s), which together make up the milliampere-seconds (mAs), is set to produce just enough X-ray photons to create an image that has the right density and contrast to display the necessary anatomical details without overexposing the patient to radiation.
Proper use of shielding, such as a lead apron and collimation of the radiation beam, is essential to protect areas of the body not being imaged. The use of fast films and advancements in digital imaging systems also contribute to reducing the necessary exposure time and, thus, the patient’s radiation dose. This approach to radiation safety in medical imaging is critical to ensure the benefits outweigh the potential risks associated with diagnostic X-rays.
For therapeutic doses, like the scenario with the y rays from a 5000-Ci Co transillumination unit, it's important to ensure the radiation dose is effective for the treatment but within safe limits. The calculation of the absorbed dose in rem would involve considering the percentage of gamma rays absorbed and their energy, alongside the mass of the tissue being treated.