Ehrlich: Patient Care in Radiography, 7th Edition

Chapter 1: Introduction to Radiography

Test Bank

MULTIPLE CHOICE

	1.	X-rays were discovered in 1895 by:
a.	Coolidge.	
b.	Crookes.	
c.	Roentgen.	
d.	Edison.	

ANS:	C
Rationale: X-rays were discovered by Wilhelm Conrad Roentgen on November 8, 1895.

REF:	pp. 2-3

	2.	Of the following types of electromagnetic energy, which has the shortest wavelength?
a.	Radio waves	
b.	X-rays	
c.	Visible light	
d.	Ultraviolet light	

ANS:	B
Rationale: Only gamma rays on the electromagnetic spectrum have a shorter wavelength than x-rays.

REF:	pp. 6-7, Fig. 1-8	

	3.	Which of the following is NOT an accurate statement regarding the characteristics of x-rays?
a.	They can penetrate matter that is impenetrable to light.	
b.	They cause certain crystals to fluoresce.	
c.	They can be refracted by a lens.	
d.	They cannot be detected by the human senses.	

ANS:	C
Rationale: X-rays can penetrate matter, cause crystals to fluoresce, and are undetectable by human senses. They cannot, however, be refracted by a lens.

REF:	p. 7

	4.	The current across the x-ray tube is measured in units of:
a.	milliamperes.	
b.	kilovolts.	
c.	rads.	
d.	roentgens.	

ANS:	A
Rationale: Amperes are the units used to measure the rate of current flow, indicating coulombs per second. Because the current across the tube is very small, it is measured in thousandths of amperes, called milliamperes.

REF:	p. 20

	5.	An electron cloud surrounding a hot cathode is referred to as a(n):
a.	focusing cup.	
b.	ampere.	
c.	space charge.	
d.	filament.	

ANS:	C
Rationale: “Space charge” is the correct term for the electron cloud that surrounds a hot filament in an x-ray tube.

REF:	p. 6

	6.	An x-ray exposure is made using the following factors: 200 mA, 0.04 second, 80 kVp, and 40 inches SID. In this case, which represents the value of the mAs?
a.	0.08	
b.	0.8	
c.	8	
d.	16,000	

ANS:	C
Rationale: mAs is the product of mA and time (200 mA ´ 0.04 sec = 8 mAs).

REF:	p. 20

	7.	The purpose of rotating the x-ray tube target is to:
a.	create a space charge.	
b.	remove long-wavelength photons from the x-ray beam.	
c.	focus the electron stream on a small target area.	
d.	increase the heat capacity of the anode.	

ANS:	D
Rationale: Rotating the target results in a larger surface area over which the electron stream impacts the anode, decreasing the amount of heat at any given point and thus increasing the anode’s heat capacity.

REF:	p. 10

	8.	An imaginary photon that is emitted from the center of the focal spot, perpendicular to the long axis of the x-ray tube, is called the:
a.	electron stream.	
b.	x-ray beam.	
c.	central ray.	
d.	radiation field.	

ANS:	C
Rationale: The term for a line that indicates the center and direction of the x-ray beam is “central ray.”

REF:	p. 8

	9.	A doubling of the mA with no change in exposure time will result in which of the following?

1.	Increased anode heat	
2.	Increased radiographic density	
3.	Increased number of photons in the x-ray beam	

a.	1 only	
b.	2 only	
c.	1 and 2	
d.	1, 2, and 3	

ANS:	D
Rationale: Because mA determines the rate at which x-rays are produced, the anode heat, radiographic density, and number of photons in the x-ray beam all are proportional to the mA setting and are therefore increased when the mA is doubled.

REF:	p. 20

	10.	When the source-image distance (SID) is doubled, the intensity of the radiation in the radiation field will be:
a.	doubled.	
b.	halved.	
c.	reduced by a factor of 4.	
d.	quadrupled.	

ANS:	C
Rationale: The radiation intensity is inversely proportional to the square of the SID. Therefore, if the SID is multiplied by 2, the radiation intensity is decreased by a factor of 22, or 4.

REF:	p. 22

	11.	An increase in object/image-receptor distance (OID) will result in which of the following?

1.	Increased magnification	
2.	Decreased image detail	
3.	Increased image detail	

a.	1 only	
b.	2 only	
c.	1 and 2	
d.	1 and 3	

ANS:	C
Rationale: The x-ray beam diverges as it travels from the subject to the imaging plane, creating an image that is larger that the subject. X-rays from different parts of the focal spot create slightly different images, resulting in a blurred edge to each part of the image, called a penumbra. Magnification of the penumbra decreases image detail.

REF:	p. 27

	12.	A device used to control the size of the radiation field is a:
a.	collimator.	
b.	tube housing.	
c.	detent.	
d.	filter.	

ANS:	A
Rationale: The term for the device attached to the tube housing to permit control of radiation field size is “collimator.”

REF:	p. 8

	13.	The primary purpose of intensifying screens is to:
a.	protect the film from light and damage during radiography.	
b.	improve the definition on the radiograph.	
c.	reduce the quantity of radiation required to produce a satisfactory image.	
d.	reduce the possibility of artifacts on the film.	

ANS:	C
Rationale: Intensifying screens absorb the energy of the x-ray beam and release it in the form of light, which has a greater effect on the photographic emulsion of x-ray film than does x-ray energy; thus, less x-ray energy is needed to produce an image when intensifying screens are used.

REF:	p. 22

	14.	The function of an x-ray grid is to:
a.	decrease patient radiation dose.	
b.	increase radiographic resolution.	
c.	increase radiographic contrast by reducing scatter radiation fog.	
d.	increase radiographic density.	

ANS:	C
Rationale: A grid is a device designed to absorb scatter radiation so that it will not expose the image receptor. Because the fog caused by scatter radiation exposure reduces radiographic contrast, a reduction of scatter increases contrast.

REF:	p. 14

	15.	Which of the following statements best describes the current knowledge regarding the effects of exposure to low doses (<20 rad) of ionizing radiation?
a.	It causes cancer after a certain amount of radiation has been received.	
b.	Depression of the white blood cell count is followed by acute gastrointestinal distress.	
c.	Birth defects will occur if the patient is pregnant.	
d.	There is increased risk of cancer, leukemia, birth defects, and cataracts.	

ANS:	D
Rationale: The key word here is risk, because at low doses the effects are random and not predictable. Thus, though statements A and C may sometimes be true, they are only slight possibilities, not predictable occurrences, and cannot be stated as facts. B describes somatic effects from much higher doses.

REF:	pp. 31-32 | p. 37	

	16.	The effective dose limit for whole-body radiation in 1 year for a nonpregnant radiation worker over the age of 18 is:
a.	5 millirem.	
b.	0.5 rem.	
c.	5 rem.	
d.	50 rem.	

ANS:	C
Rationale: The annual effective dose limit for nonpregnant workers over the age of 18 is 5 rem (50 mSv), according to the National Council on Radiation Protection and Measurements.

REF:	p. 35

	17.	Which of the following devices is NOT employed to reduce the hazards of radiation exposure to the patient?
a.	Gonad shield	
b.	Bucky	
c.	Intensifying screen	
d.	Collimator	

ANS:	B
Rationale: Because the patient is positioned between the x-ray tube and the bucky, the bucky protects the image receptor from scatter radiation exposure but has no effect on patient safety.

REF:	p. 14

	18.	Which of the following will result in the lowest patient dose?
a.	Low kVp and high mAs	
b.	High kVp and low mAs	
c.	How kVp and long exposure time	
d.	Long exposure time and short SID	

ANS:	B
Rationale: mAs is the principal factor affecting patient dose. Because high kVp makes it possible to get an acceptable image with less mAs, high kVp with low mAs is considered to be a “low dose” exposure.

REF:	p. 35

	19.	What is a rad?
a.	A radiation unit that is determined by measuring ionization of air	
b.	A factor that quantifies the relative health risks of various types of radiation	
c.	A radiation unit used to measure patient dose	
d.	A radiation unit used to measure dose equivalents for occupational exposure	

ANS:	C
Rationale: Rad stands for radiation absorbed dose and is the unit in the British system for measuring patient dose.

REF:	p. 28

	20.	What is a rem?
a.	A radiation unit that is determined by measuring ionization of air	
b.	A device containing a crystal that absorbs radiation energy and discharges it in the form of light when heated	
c.	A factor that quantifies the relative health risks of various types of radiation	
d.	A radiation unit used to measure dose equivalents for occupational exposure	

ANS:	D
Rationale: Rem stands for roentgen equivalent in man. It is the unit in the British system for dose equivalent measurement.

REF:	p. 29

	21.	What is meant by R?
a.	A radiation unit that is determined by measuring ionization of air	
b.	A device containing a crystal that absorbs radiation energy and discharges it in the form of light when heated	
c.	A factor that quantifies the relative health risks of various types of radiation	
d.	A radiation unit used to measure patient dose	

ANS:	A
Rationale: The roentgen (R) is the unit of exposure in the British system. It is determined by measuring the electrical current generated when radiation ionizes a quantity of dry air.

REF:	p. 28

	22.	What is meant by WF?
a.	A device containing a crystal that absorbs radiation energy and discharges it in the form of light when heated	
b.	A factor that quantifies the relative health risks of various types of radiation	
c.	A radiation unit used to measure patient dose	
d.	A radiation unit used to measure dose equivalents for occupational exposure	

ANS:	B
Rationale: The weighting factor (WF), formerly called quality factor (QF), is the number assigned to various types of radiation based on their relative biologic effect compared to that of x-rays.

REF:	p. 29

	23.	What is an Sv?
a.	A radiation unit that is determined by measuring ionization of air	
b.	A device containing a crystal that absorbs radiation energy and discharges it in the form of light when heated	
c.	A radiation unit used to measure patient dose	
d.	A radiation unit used to measure dose equivalents for occupational exposure	

ANS:	D
Rationale: The Sievert (Sv) is the international unit for measuring dose equivalents as used to measure occupational exposure .

REF:	p. 29

	24.	What is a Gy?
a.	A radiation unit that is determined by measuring ionization of air	
b.	A factor that quantifies the relative health risks of various types of radiation	
c.	A radiation unit used to measure patient dose	
d.	A radiation unit used to measure dose equivalents for occupational exposure	

ANS:	C
Rationale: The Gray (Gy) is the international unit used to measure patient dose, the absorbed dose in specific tissue.

REF:	p. 28

	25.	What is a TLD?
a.	A radiation unit that is determined by measuring ionization of air	
b.	A device containing a crystal that absorbs radiation energy and discharges it in the form of light when heated	
c.	A factor that quantifies the relative health risks of various types of radiation	
d.	A radiation unit used to measure patient dose	

ANS:	B
Rationale: A thermoluminescent dosimeter (TLD) is a type of personal occupational dose monitoring device that contains one or more lithium fluoride crystals that absorb radiation energy and discharge it in the form of light when heated.

REF:	p. 34

	26.	The majority of radiography education programs today are based in:
a.	proprietary schools.	
b.	hospitals.	
c.	clinics.	
d.	colleges.	

ANS:	D
Rationale: Since the 1970s, the majority of approved educational programs in radiography in the United States have been based in colleges, primarily community colleges.

REF:	p. 4

	27.	The container for the vacuum of the x-ray tube is made of:
a.	glass.	
b.	aluminum.	
c.	tungsten.	
d.	carbon.	

ANS:	A
Rationale: Pyrex glass is used to form the outer, envelope portion of the x-ray tube.

REF:	p. 5

	28.	X-rays are a type of:
a.	electricity.	
b.	microwave.	
c.	kinetic energy.	
d.	electromagnetic energy.	

ANS:	D
Rationale: Microwaves and x-rays are different types of electromagnetic energy. Electricity and kinetic energy are types of energy that are not electromagnetic.

REF:	p. 6

	29.	The frequency of an electromagnetic sine wave is defined as:
a.	the distance from trough to crest.	
b.	the distance from one crest to the next.	
c.	the number of times per second that a crest passes a given point.	
d.	the velocity at which the wave travels through space.	

ANS:	C
Rationale: The frequency of a sine wave is the number of times per second that the crest of the wave passes a given point.

REF:	p. 6

	30.	Which of the following formulas represents the relationship between the wavelength, frequency, and velocity of an electromagnetic wave?
a.		
b.		
c.		
d.		

ANS:	B
Rationale: Because the velocity is constant , and the wavelength and frequency are inversely proportional to each other, the velocity is equal to the frequency multiplied by the wavelength.

REF:	p. 6

	31.	Which of the following substances is most readily penetrated by x-rays?
a.	Water	
b.	Air	
c.	Bone	
d.	Fat	

ANS:	B
Rationale: Differential penetration of x-rays is determined by the mass density of the subject and its thickness. Air has the lowest mass density of the substances listed.

REF:	p. 7

	32.	Grids or buckys are generally used for body parts that measure greater than:
a.	2 to 4 cm.	
b.	10 to 12 cm.	
c.	18 to 20 cm.	
d.	30 cm.	

ANS:	B
Rationale: Body parts that measure more than 10 to 12 cm in thickness produce enough scatter radiation during an exposure to fog the image, reducing contrast and compromising the quality of the radiograph.

REF:	p. 16

	33.	The access point for the radiographer to determine the exposure factors and to initiate the exposure is called the:
a.	transformer.	
b.	image receptor unit.	
c.	control console.	
d.	stationary grid.	

ANS:	C
Rationale: The control console, located in the control booth, is the place where the radiographer sets the exposure factors and initiates the exposure.

REF:	pp. 16-17

	34.	An x-ray machine designed for direct viewing of the x-ray image is called a(n):
a.	image receptor.	
b.	transformer.	
c.	control console.	
d.	fluoroscope.	

ANS:	D
Rationale: A fluoroscope is the term for a machine that permits direct viewing of x-ray images in real time.

REF:	p. 17

	35.	In order to increase the penetration of the x-ray beam, which of the following factors should be increased?
a.	Kilovoltage	
b.	Milliamperage	
c.	mAs	
d.	Exposure time	

ANS:	A
Rationale: Kilovoltage is a measure of the potential difference across the x-ray tube and determines the speed of the electrons in the electron stream. This determines the amount of kinetic energy each electron has when it collides with the target and thus determines the amount of energy in the resulting x-ray beam. This energy is expressed by the wavelength of the photons. X-ray photons with shorter wavelengths have more energy and are more penetrating than those with longer wavelengths. For this reason, an increase in kVp results in a more penetrating x-ray beam.

REF:	p. 21