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Chapter 11
Equipment design for radiation protection
Question | Answer |
---|---|
1. Why is a diagnostic-type protective tube housing required? | To safeguard the patient and imaging personnel from off-focus, or leakage, radiation by restricting the emission of x-rays to the area of the useful, or primary, beam |
2. The housing enclosing the x-ray tube must be constructed with _______ to reduce leakage radiation. | lead lining |
3. Leakage radiation is measured at a distance of ___ from the x-ray source and must not exceed an air kerma rate of ___________ or exposure rate of ______________ when the tube is operated at its highest voltage at the highest current that allows continu | 1.1 meter__, 2. 0.88 mGy/hr 3..100 mR/hr_ |
4. Define control panel or console | Place where technical exposure factors such as mA, kVp, and exposure duration (mS) are selected and visually displayed. |
5. Where must the control panel or console be located? | Behind a properly shielded barrier that also has a radiation-absorbent window, which permits continuous observation of the patient during any procedure |
6. True or False: It is required that the exposure hand control be mechanically affixed to the console such that it cannot be activated while the operator is in an unshielded location. | True |
7. The radiographic examination table must be strong enough to support weight up to and in excess of _______ pounds. | _400__ |
8. What type of material is commonly used in the tabletop to meet the thickness and radiolucency requirement? | Carbon fiber |
9. How can radiographic equipment meet the SID indicator needs? | Radiographic equipment comes with an indicator that will perform the function of maintaining a required SID. Previously, a simple device such as a tape measure was attached to the collimator or tube housing so that the radiographer could manually measure |
10. Distance and centering indicators must be accurate within ___ and ___ of the SID respectively. | 2% __ 1% |
11. Define the function of the light-localizing variable-aperture rectangular collimator. | Provides the unit with the ability to automatically or manually adjust the x-ray beam to a specific size and shape (either rectangular or square). Serves as the x-ray beam limitation device that approximates the size of the anatomical area or part to be i |
13. To minimize skin exposure to electrons produced by photon interaction with the collimator, the patient’s skin surface should be at least _____ cm below the collimator for fixed radiographic equipment. | 15 |
14. Portable or mobile radiographic units are required to maintain a SSD of at least ______ cm. | 30 |
15. The standard of acceptance is that the sum of the cross-table and along-the-table alignment differences between the x-ray and light beams must not exceed _______ of the SID. | 2% |
16. The two coincidence requirements between the radiographic beam and the localizing light beam are known as: | Alignment and congruence |
17. According to state requirements, both in alignment and congruence, of a positive beam limitation (PBL) system’s setting with the actual dimensions of the radiographic beam vary from ______ of the SID. | 2%__ to __3% |
18. Define filtration. | Absorption of most of the lower-energy photons (long wavelength) from the heterogeneous beam. Filtration icreases quality thus hardening the beam |
19. List the two types of filtration. | inherent and added |
20. What comprises inherent filtration? | Glass envelope encasing the x-ray tube, insulating oil surrounding the tube, and the glass window in the tube housing |
21. What comprises added filtration? | Thin sheets of aluminum (or the equivalent) of a millimeter to submillimeter thickness |
22. What is the regulatory standard requirement for total filtration for fixed x-ray units operating above 70 kVp? | 2.5 mm Al equivalent |
23. What is the most widely used filter material in diagnostic radiology? Why? | Aluminum. Removes very low energy x rays from a poly energetic beam. with out decreasing x ray intensity. light weight, sturdy, inexpensive, readily available |
Define HVL | A material such as aluminum, lead-acrylic, or other suitable material inserted between the x-ray source and the patient to modify the quality of the beam across the FOV. Examples include a wedge or trough/bilateral wedge filter. |
25. Define compensating filters and provide examples. | A material such as aluminum, lead-acrylic, or other suitable material inserted between the x-ray source and the patient to modify the quality of the beam across the FOV. Examples include a wedge or trough/bilateral wedge filter. |