![]() Pair production is an interaction that occurs only at energies of 1.02 MeV, and therefore, it does not occur in diagnostic radiography. In pair production, the x-ray photon disappears, and is replaced by two oppositely charged electrons. Lead aprons are used to protect us from exposure to scattered radiation during these procedures. In classic scatter, a low-energy photon interacts with an atom but causes no ionization the incident photon disappears in the atom and then immediately reappears and is released as a photon of identical energy but with changed direction. It can, however, contribute to and pose a radiation hazard to personnel (as in fluoroscopic procedures). Because the scattered photon exits the body, it does not pose a radiation hazard to the patient. Scattered radiation adds unwanted, degrading densities to the radiographic image. With respect to the radiographic image, it is responsible for the scattered radiation that reaches the film/image receptor. This scattered ray will either contribute to image fog or pose a radiation hazard to radiologic personnel depending on its direction of exit, especially in fluoroscopy and mobile radiography thus, Compton scatter contributes the most to occupational exposure. The outer-shell electron leaves the atom and is called a recoil electron. In doing so, the incident photon is deflected with reduced energy (modified scatter), but it retains most of its original energy and exits the body as an energetic scattered photon. In Compton scatter, a high-energy-incident photon (high kVp) uses some of its energy to eject an outer-shell electron. This interaction contributes to patient dose and produces short-scale contrast. When photon ceases to exist, it means it has used all its energy to ionize the atom. This type of interaction contributes most to patient dose because all the x-ray photon energy is being transferred to tissue. The photoelectric effect occurs with high-atomic-number (Z) absorbers such as bone and with positive contrast media. An electron (L-shell) from the shell beyond drops down to fill the vacancy (K-shell) and in so doing emits a characteristic ray whose energy equals the difference in binding energies for the K and L shells. In the photoelectric effect, the low-energy incident photon is absorbed by the tissues being radiographed and uses all its energy to eject an inner-shell electron from the target atom, leaving a vacancy in that shell, for example, the K-shell. Attenuation is principally attributable to the two predominant interactions between x-ray photons and matter in diagnostic x-ray: Compton scatter and the photoelectric effect. The gradual decrease in exposure rate as ionizing radiation passes through tissues is called attenuation. Different types of ionization processes can take place depending on the photon energy and the type of material being irradiated. These radiations are called ionizing because they have the energetic potential to break apart electrically neutral atoms, resulting in the production of negative and/or positive ions. Some radiations are energetic enough to rearrange atoms in materials through which they pass, and they can therefore be hazardous to living tissue. ![]() Personnel present in the x-ray room during fluoroscopic examinations wear lead aprons to protect them primarily from Lead aprons are worn during fluoroscopy to protect the radiographer from exposure to radiation from The x-ray interaction with matter that is responsible for the majority of scattered radiation reaching the image receptor (IR) is Which of the following contributes most to occupational exposure? Which interaction between x-ray photons and matter involves partial transfer of the incident photon energy to the involved atom? The photoelectric effect is more likely to occur with The photoelectric effect is an interaction between an x-ray photon and Which of the following interactions between x-ray photons and matter is most responsible (contributes most) for patient dose? Which interaction between x-ray photons and matter results in total absorption of the incident photon?
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