What percentage of incident photons emerges from the patient unaffected during X-ray procedures?

During X-ray procedures, a significant portion of the incident photons emitted by the X-ray tube interacts with the patient’s body. Most of these photons either get absorbed or scatter, potentially compromising image quality and posing a radiation dose to the patient. However, only a small percentage of the incident photons actually pass through the patient without any interaction, which contributes to forming an image on the radiographic detector.

Research and industry standards indicate that around 5% of incident photons typically emerge from the patient unaffected. This percentage reflects the balance between absorption and transmission of photons through various tissues—where denser tissues, such as bone, absorb more photons compared to less dense tissues, such as muscle or fat. The 5% figure provides a realistic understanding of how efficient the X-ray process is in producing diagnostic images while highlighting the need to minimize patient exposure to radiation by optimizing imaging techniques.