X-RAY PHYSICS
Midterm
February 15, 1990
Dr. Guebert
CHOOSE THE SINGLE BEST ANSWER UNLESS OTHERWISE INSTRUCTED.
1.
An electron is a fundamental particle of the atom and carries an electrical charge of:
a. 0
b. +1
c. –1
d. +2
e. –2
2.
The strength of attachment of an electron to the nucleus is called the:
a. linear transfer energy
b. electron binding energy
c. electromagnetic energy
d. kinetic energy
3.
How many half-lives are required before a quantity of radioactive material has decayed to less than 1%
of its original value?
a. 1
b. 3
c. 5
d. 7
e. 9
4.
T/F X-rays are considered a type of particulate ionizing radiation.
5.
X-rays are usually identified by their energy, measured in:
a. units of optical density
b. curies
c. ion pairs
d. electron volts
6.
Structures that absorb x-rays are called:
a. radiopaque
b. transparent
c. radiolucent
d. attenuating
7.
T/F Thick, muscular patients require lower KVP for better penetration.
8.
When performing an AP thoracic view, one should:
a. place the anode facing caudally
b. place the anode facing cranially
c. place the anode facing laterally
d. use a long focal film distance.
e. None of the above
9.
T/F The use of non bucky holders takes additional time to utilize and since the radiation dose to the
patient is also greater their routine use is not justified.
10. Because of the unavoidably large object/film distance encountered when performing a lateral or
oblique cervical spine radiograph, magnification will be most reduced by using a focal film distance
of:
a. 36 inches
b. 40 inches
c. 60 inches
d. 72 inches
11. T/F In order to improve visualization of the intervertebral disc spaces of the lumbar spine, with the
patient in the supine (recumbant) position, you should ask the patient to flex his knees and place his
feet flat on the table top.
12. What is the convention in accommodating tube tilts?
a. You don’t use tube tilts often enough to worry about it
b. It is the annual “Accommodation Convention” held every year at the Cervantes Convention Center
c. One foot for every five inches of tilt
d. You only have to accommodate for tilts greater than 45 degrees
e. None of the above
13. Due to the significant thickness of the abdomen in its lateral dimension, a lateral x-ray projection of the
lumbar spine requires:
a. a moving or stationery grid
b. the small focal spot
c. an upright patient position
d. par speed screens
e. non bucky holders
14. Grids are positioned between the:
a. cathode and anode
b. collimator and tube
c. patient and the tube
d. patient and the film
15. Regarding full spine radiography, due to the inherent non-uniformity of part thickness, the best
solution to create a more uniformly exposed x-ray would require the use of:
a. split screens
b. sectional filtration
c. gradient screens
d. focused grids
e. sight developing
16. What is the safest time to x-rya a female who is capable of child bearing?
a. Through the 10th day after the onset of menses.
b. The first Tuesday of every month.
c. For the three weeks after menstruation has ceased.
d. At any time.
17. As a general rule, a film would remain in the fixing solution _________ as long as in the developer.
a. 25%
b. 30%
c. 50%
d. 100%
e. 200%
18. Grid are made up of alternating strips of:
a. lead and radiolucent material
b. copper and plastic
c. copper and lead
d. plastic and aluminum
19. What are heat units?
a. The room temperature in the x-ray room.
b. The temperature of the processing chemicals.
c. The amount of heat necessary to cause thermionic emission at the filament.
d. KVP x mA x seconds.
20. The heel effect is:
a. an artifact caused by x-raying a patient’s foot with the shoe on.
b. particularly important on x-rays of the thoracic spine.
c. a physical phenomenon but not of practical importance.
d. particularly important on x-rays of the lumbar spine.
21. What material is generally used for added filtration to meet National Commission for Radiation
Protection (NCRP) recommendations?
a. lead
b. tungsten
c. aluminum
d. iron
e. plastic
22. Using which of the following intensifying screens for routine radiography would result in the least xray exposure to the patient (with all other factors being equal)?
a. par
b. high speed
c. high plus
d. rare earth
23. Which of the following factors would yield the most radiation protection for the patient being
exposed?
a. utilizing a high ratio grid
b. using a high KVP, low mAs technique
c. decreased focal film distance (FFD)
d. using the small focal point
24. The primary purpose of added filtration at the x-ray tube is to:
a. reduce penumbra
b. increase film contrast
c. decrease average beam energy
d. reduce skin dosage
e. scatter the low energy x-rays before striking the patient
25. Magnification can be reduced by:
a. increasing the object/film distance.
b. decreasing the object/film distance
c. increasing the mAs
d. decreasing the KVP
e. using a shorter source/image distance
26. Poor film/screen contact results in:
a. increased film density
b. decreased film density
c. increased sharpness due to increased penumbra
d. increased sharpness due to decreased penumbra
e. a locally fuzzy image
27. X-rays travel:
a. in parallel paths
b. at the speed of sound
c. at a speed directly proportional to the mAs
d. at a speed inversely proportional to the kVp
e. at the speed of light
28. The intensity of the x-ray beam is:
a. uniform from top to bottom
b. uniform from side to side
c. greater on the side of the cathode
d. greater on the side of the anode
e. strongest at the central ray
29. An x-ray machine converts what approximate percentage of the available energy into x-rays?
a. 1%
b. 25%
c. 50%
d. 75%
e. 99%
30. Of the following, which is the single greatest source of exposure of the human population to man-made
radiation?
a. nuclear reactors that create electric power
b. radiation used for diagnostic purposes
c. nuclear reactors that power the ships and planes
d. radioactive materials used in testing pipe welds
e. storage of spent nuclear reactor fuels near populated areas
31. X-rays are a form of electromagnetic radiation similar to visible light but of _________ wavelength.
a. shorter
b. longer
c. less frequent
d. more frequent
32. X-rays travel at _____ miles per second.
a. 125,000
b. 186,000
c. 210,000
d. 300,000
33. X-rays act as small separate packets of energy called:
a. atoms
b. protons
c. electrons
d. photons
34. X-rays are produced when fast moving _________ collide with matter.
a. atoms
b. protons
c. electrons
d. photons
35. The ________ of the filament controls the quantity of electrons emitted.
a. length
b. diameter
c. resistance
d. temperature
36. When a very high electrical potential (kVp) is applied across the x-ray tube, then electrons are ______
___ the anode.
a. repelled by
b. attracted to
c. magnetized by
d. vaporized by
37. Higher kVp settings result in x-rays that have _______ penetrating power.
a. less
b. variable
c. greater
d. unknown
38. Kilovoltage controls the ________ of the electrons flowing from the cathode to the anode.
a. number
b. direction
c. speed
d. focusing
39. Rectifiers control the _______ of the current flow.
a. number of electrons
b. direction
c. speed
d. deceleration
40. X-rays radiate from their anode source in straight lines:
a. toward magnetic North
b. toward the patient
c. toward the radiation worker
d. in all directions
41. Which material would absorb the greatest number of x-rays?
a. Copper
b. Tungsten
c. Aluminum
d. Lead
42. When an aluminum filter is inserted in the x-ray beam, it is considered the __________ filtration.
a.Minimum
b.Excessive
c.Total
d.Added
43. In special instances like mammography, molybdenum is used as a target material instead of tungsten
because it:
a.produces a higher percentage of low energy photons
b.is less costly to manufacture into anodes
c.yields a greater number of x-ray photons per incident electron
d.has better heat conduction characteristics compared to tungsten
44. If a 10 inch air gap will be utilized when performing a PA chest radiograph, what would be the
expected focal film distance?
a. 6’
b. 8’
c. 10’
d. 12’
45. A spinning top is used on single phase x-ray machines to check:
a. KVP accuracy
b. mA accuracy
c. timer accuracy
d. for heat unit capacity
46. Higher KVP exposure values result in:
a. more Compton scatter x-rays
b. radiographs with more contrast
c. faster x-ray photons
d. a greater proportion of photoelectric interactions
47. T/F An increase in milliamperage results in a decrease in amplitude of the emission spectrum and a
shift in the peak to the right.
48. An increase in the KVP value by 15% must be compensated by a _______% ______ in mAs to
maintain the density of the original film.
a. 15% decrease
b. 15% increase
c. 50% decrease
d. 50% increase
e. 400% increase
49. To image small differences in soft tissue one must use ______ technique.
a. high mAs
b. low mAs
c. high KVP
d. low KVP
50. Proper collimation of the x-ray beam has the primary effect of reducing patient dose by:
a. decreasing the volume of tissue irradiated
b. focusing the beam into a smaller area
c. eliminating the lower energy Bremsstrahlung radiation
d. shifting the emission spectrum’s average energy to the right.
Answers
* these answers have not been verified and may not be correct
1.C 2.B 3.D 4.F 5.D 6.A 7.F 8.B 9.F 10.D 11.T 12.E 13.A 14.D 15.B 16.A 17.E 18.A 19.D
20.B 21.C 22.D 23. 24.E 25.B 26.E 27.E 28.C 29.A 30.? 31.? 32.B 33.D 34.C 36.B 37.C 38.C
39.B 40.D 41.D 42.D 43.A 44.A 45.C 46.A 47.F 48.C 49.D 50.A