front 1 Which of the following is most likely to occur as a result of using a 30-in. SID with a 14 × 17 in. IR to radiograph a fairly homogeneous structure? A Production of quantum mottle B Density variation between opposite ends of the IR C Production of scatter radiation fog D Excessively short-scale contrast | back 1
The Correct Answer is: B |
front 2 Which of the following affect(s) both the quantity and quality of the primary beam? Half-value layer (HVL) A | back 2 he Correct Answer is: C |
front 3 If exposure factors of 85 kVp, 400 mA, and 12 ms yield an output exposure of 150 mR, what is the milliroentgens per milliampere-seconds (mR/mAs)? A 0.32 B 3.1 C 17.6 D 31 | back 3 The Correct Answer is: D However, all the equipment being compared must be of the same type (e.g., all single-phase or all three-phase, six-pulse). If there is linearity among these machines, then identical technique charts can be used. In the example given, 400 mA and 12 ms were used, equaling 4.8 mAs. If the output for 4.8 mAs was 150 mR, then 1 mAs is equal to 31.25 mR (150 mR ÷ 4.8 mAs = 31.25 mR/mAs). (Bushong, 8th ed., pp. 248–249) |
front 4 To eject a K-shell electron from a tungsten atom, the incoming electron must have an energy of at least A 60 keV. B 70 keV. C 80 keV. D 90 keV. | back 4 The Correct Answer is: B First, if the high-speed electron is attracted by the nucleus of a tungsten atom and changes its course, as the electron is “braked,” energy is given up in the form of an x-ray photon This is called Bremsstrahlung (“braking”) radiation, and it is responsible for most of the x-ray photons produced at the conventional tungsten target. Second, a high-speed electron having an energy of at least 70 keV may eject a tungsten K-shell electron, leaving a vacancy in the shell. An electron from the next energy level, the L shell, drops down to fill the vacancy, emitting the difference in energy as a K-characteristic ray. Characteristic radiation makes up only about 15% of the primary beam. (Bushong, 8th ed., p. 176) |
front 5 If a high-voltage transformer has 100 primary turns and 35,000 secondary turns, and is supplied by 220 V and 75 A, what are the secondary voltage and current? A 200 A and 77 V B 200 mA and 77 kVp C 20 A and 77 V D 20 mA and 77 kVp | back 5 he high-voltage, or step-up, transformer functions to increase voltage to the necessary kilovoltage. It decreases the amperage to milliamperage. The amount of increase or decrease is dependent on the transformer ratio-the ratio of the number of turns in the primary coil to the number of turns in the secondary coil. The transformer law is as follows: To determine secondary V, To determine secondary I Substituting known factors, 35,000/100 = x/220 100x = 7,700,000 x = 77,000 V (77kVp) 35,000/100 = 75/x 35,000x = 7,500 x = 0.214 Amps (214 mA) (Selman, pp 84–85)
Vs/Vp=Ns/VP or ns/np=IP/Is |
front 6 An increase in the kilovoltage applied to the x-ray tube increases the
A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3 | back 6 he Correct Answer is: B As the kilovoltage is increased, a greater number of electrons are driven across to the anode with greater force. Therefore, as energy conversion takes place at the anode, more high-energy photons are produced. However, because they are higher-energy photons, there will be less patient absorption. (Fauber, 2nd ed., p. 58) |
front 7 Which of the following will serve to increase the effective energy of the x-ray beam?
A 1 only B 2 only C 1 and 2 only D 1, 2, and 3 | back 7 he Correct Answer is: C As filtration is added to the x-ray beam, the lower-energy photons are removed, and the overall energy or wavelength of the beam is greater . As kilovoltage is increased, more high-energy photons are produced, and again, the overall, or average, energy of the beam is greater. An increase in milliamperage serves to increase the number of photons produced at the target but is unrelated to their energy. (Selman, 9th ed., p. 171) |
front 8 How many half-value layers will it take to reduce an x-ray beam whose intensity is 78 R/min to an intensity of less than 10 R/min? A 2 B 3 C 4 D 8 | back 8 he Correct Answer is: B |
front 9 Characteristics of the metallic element tungsten include
A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3 | back 9 he Correct Answer is: D Because tungsten has a high atomic number (74), it produces high-energy x-rays more efficiently. Since a great deal of heat is produced at the target, tungsten's high melting point (3,410°C) helps to avoid damage to the target surface. Heat produced at the target should be dissipated readily, and tungsten's conductivity is similar to that of copper. Therefore, as heat is applied to the focus, it can be conducted throughout the disk to equalize the temperature and thus avoid pitting, or localized melting, of the focal track. (Selman, 9th ed., p. 138) |
front 10 To be used more efficiently by the x-ray tube, alternating current is changed to unidirectional current by the A filament transformer. B autotransformer. C high-voltage transformer. D rectifiers. | back 10 The Correct Answer is: D They serve to change AC, which is needed in the low-voltage side of the x-ray circuit, to unidirectional current. Unidirectional current is necessary for the efficient operation of the x-ray tube. The rectification system is located between the secondary coil of the high-voltage transformer and the x-ray tube. The filament transformer functions to adjust the voltage and current going to heat the x-ray tube filament. The autotransformer varies the amount of voltage being sent to the primary coil of the high-voltage transformer so that the appropriate kVp can be obtained. The high-voltage transformer "steps up" the voltage to the required kilovoltage and steps down the amperage to milliamperage. (Carlton & Adler, p 78) |
front 11 The source of electrons within the x-ray tube is A electrolysis. B thermionic emission. C rectification. D induction. | back 11 The Correct Answer is: B . The x-ray tube filament is made of thoriated tungsten and is part of the cathode assembly. Its circuit provides current and voltage to heat it to incandescence, at which time it undergoes thermionic emission—the liberation of valence electrons from the filament atoms. Electrolysis describes the chemical ionization effects of an electric current. Rectification is the process of changing AC to unidirectional current. (Bushong, p 118) |
front 12 With three-phase equipment, the voltage across the x-ray tube
A 1 only B 2 only C 1 and 2 only D 2 and 3 only | back 12 he Correct Answer is: D |
front 13 The line-focus principle refers to the fact tha t A the actual focal spot is larger than the effective focal spot B the effective focal spot is larger than the actual focal spot C x-rays travel in straight lines D x-rays cannot be focused | back 13 The Correct Answer is: A The actual focal spot is the finite area on the tungsten target that is actually bombarded by electrons from the filament. The effective focal spot is the foreshortened size of the focus as it is projected down toward the image receptor. This is called line focusing or the line-focus principle. The quoted focal-spot size is the effective focal-spot size. (Carlton & Adler, 4th ed., pp. 112–114) |
front 14 The electron cloud within the x-ray tube is the product of a process called A electrolysis B thermionic emission C rectification D induction | back 14 The Correct Answer is: B |
front 15 Which of the following occurs during Bremsstrahlung (Brems) radiation production? A An electron makes a transition from an outer to an inner electron shell. B An electron approaching a positive nuclear charge changes direction and loses energy. C A high-energy photon ejects an outer-shell electron. D A low-energy photon ejects an inner-shell electron. | back 15 he Correct Answer is: B s radiation. (2) If the incident electron were to eject a K-shell electron, an L-shell electron would move in to fill the vacancy. It releases a photon (K-characteristic ray) whose energy equals the difference between the K- and L-shell energy levels. This is characteristic radiation; it is responsible for only a small portion of the primary beam. (Bushong, 8th ed., pp. 149–152) |
front 16 Which of the following terms describes the amount of electric charge flowing per second? A Voltage B Current C Resistance D Capacitance | back 16 The Correct Answer is: B Current is defined as the amount of electric charge flowing per second. Voltage is the potential difference existing between two points. Resistance is the property of a circuit that opposes current flow. Capacitance describes a quantity of stored electricity. (Selman, 9th ed., pp. 46–47) |
front 17 What is the relationship between kV and HVL? A As kV increases, the HVL increases. B As kV increases, HVL decreases C If the kV is doubled, the HVL doubles. D If the kV is doubled, the HVL is squared. | back 17 he Correct Answer is: A The HVL of a particular beam is defined as that thickness of a material that will reduce the exposure rate to one-half of its original value. The more energetic the beam (the higher the kilovoltage), the greater is the HVL thickness required to cut its intensity in half. Therefore, it may be stated that kilovoltage and HVL have a direct relationship: As kilovoltage increases, HVL increases. (Selman, 9th ed., pp. 122–123) |
front 18 Characteristics of x-ray photons include
A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3 | back 18 The Correct Answer is: B |
front 19 The effective energy of an x-ray beam is increased by increasing the
A 1 only B 2 only C 1 and 2 only D 1, 2, and 3 | back 19 The Correct Answer is: C As kilovoltage is increased, more high-energy photons are produced, and again, the overall or average energy of the beam is greater. An increase in milliamperage serves to increase the number of photons produced at the target but is unrelated to their energy. (Bushong, 8th ed., pp. 165, 166) Mark for Review Discussion Add to My Notes Performance Overall Time Spent 00:30:03 Performance in Last 10 Qs Hard Easy About this Question Question Difficulty Difficulty 71.77% (33691/46946) Students got it correct Study this topic • Pr |