Week 4 Radiology Review

Front 1

If the primary coil of the high-voltage transformer is supplied by 220 V and has 200 turns, and the secondary coil has 100,000 turns, what is the voltage induced in the secondary coil?
A.
40 kV
B.
110 kV
C.
40 V
D.
110 V

Back 1

B.
110 kV

Front 2

Radiation safety requirements for fluoroscopic equipment include the following:
1. SSD at least 38 cm on stationary (fixed) equipment.
2. SSD at least 30 cm on mobile equipment.
3. high level/boost mode must have continuous audible signal.

Back 2

1, 2, and 3

Front 3

Which of the following types of radiation is (are) considered electromagnetic?
1. X-ray
2. Gamma
3. Beta

Back 3

1 and 2 only

Front 4

Which of the following cells are the most radiosensitive?
A.
Myelocytes
B.
Erythroblasts
C.
Megakaryocytes
D.
Myocytes

Back 4

B.
Erythroblasts

Front 5

The late effects of radiation are considered to
1. have no threshold dose.
2. be directly related to dose.
3. occur within hours of exposure.

Back 5

1 and 2 only
Exposure to high doses of radiation results in early effects. Examples of early effects are blood changes and erythema. If the exposed individual survives, then late or long-term effects must be considered. Individuals who receive small amounts of low-level radiation (such as those who are occupationally exposed) are concerned with the late effects of radiation exposure—those effects that can occur many years after the initial exposure. Late effects of radiation exposure, such as carcinogenesis, are considered to be related to the linear nonthreshold dose-response curve. That is, there is no safe dose; theoretically, even one x-ray photon can induce a later response.

Front 6

Which of the following equipment is mandatory for performance of a myelogram?
A.
Cine camera
B.
105-mm spot film
C.
Tilting x-ray table
D.
Tomography

Back 6

C.
Tilting x-ray table

Front 7

Which of the following combinations will present the greatest heat-loading capability?
A.
17° target angle, 1.2-mm actual focal spot
B.
10° target angle, 1.2-mm actual focal spot
C.
17° target angle, 0.6-mm actual focal spot
D.
10° target angle, 0.6-mm actual focal spot

Back 7

B. 10° target angle, 1.2-mm actual focal spot
The smaller the focal spot, the more limited the anode is with respect to the quantity of heat it can safely accept. As the target angle decreases, the actual focal spot can be increased while still maintaining a small effective focal spot. Therefore, group B offers the greatest heat-loading potential, with a steep target angle and a large actual focal spot. It must be remembered, however, that a steep target angle increases the heel effect, and film coverage may be compromised

Front 8

A dose of 25 rad to the fetus during the fourth or fifth week of pregnancy is more likely to cause which of the following:
A.
Spontaneous abortion
B.
skeletal anomalies
C.
neurologic anomalies
D.
organogenesis

Back 8

The answer is B.

EXPLANATION: During the first trimester, specifically the 2 to 8 weeks of pregnancy (during major organogenesis), if the radiation dose is at least 20 rad, fetal anomalies can be produced. Skeletal anomalies usually appear if irradiation occurs in the early part of this time period, and neurologic anomalies are formed in the latter part; mental retardation and childhood malignant diseases, such as cancers or leukemia, can also result from irradiation during the first trimester. Fetal irradiation during the second and third trimester is not likely to produce anomalies, but rather, with sufficient dose, some type of childhood malignant disease. Fetal irradiation during the first 2 weeks of gestation can result in spontaneous abortion.

Front 9

According to National Council on Radiation Protection and Measurements (NCRP) regulations, leakage radiation from the x-ray tube must not exceed
A.
10 mR/h.
B.
100 mR/h.
C.
10 mR/min
D.
100 mR/min

Back 9

B.
100 mR/h.

Front 10

Which of the following interactions between x-ray photons and matter involves a high-energy photon and the ejection of an outer shell electron?
A.
Photoelectric effect
B.
Coherent scatter
C.
Compton scatter
D.
Pair production

Back 10

The answer is C.

EXPLANATION: Compton scattering occurs when a relatively high-energy incident photon uses part of its energy to eject an outer shell electron, and in doing so changes its direction (is scattered). The energy retained by the scattered photon depends on the angle formed by the ejected electron and the scattered photon: The greater the angle of deflection, the less the retained energy. Compton scatter is very energetic scatter. It emerges from the patient and is responsible for scatter radiation reaching the image in the form of fog. In the photoelectric effect, a relatively low energy photon uses all its energy to eject an inner shell electron, leaving a vacancy. An electron from the shell above drops down to fill the vacancy, and in doing so gives up a characteristic ray. This type of interaction contributes most to patient dose, as all the photon energy is transferred to tissue. In coherent scatter, no energy is absorbed by the part; it all emerges as scattered photons. Pair production occurs only at very high energy levels, at least 1.02 MeV

Front 11

The instrument that is frequently used in quality control programs to measure varying degrees of x-ray exposure is the
A.
aluminum step wedge.
B.
spinning top.
C.
densitometer.
D.
sensitometer.

Back 11

The answer is C.

EXPLANATION: Every radiographic image is composed of a number of different densities. These densities may be measured and given a numeric value with a device called a densitometer. A sensitometer is another device used in quality control programs; it is used to give a precise exposure to a film emulsion. An aluminum step wedge (penetrometer) may be used to show the effect of kVp on contrast. A spinning top is used to test the accuracy of the x-ray machine's timer or rectifiers.

Front 12

Which of the following is (are) included in whole-body dose equivalents?
1. Gonads
2. Lens
3. Extremities

Back 12

1 and 2 only
EXPLANATION: Whole-body dose is calculated to include all the especially radiosensitive organs. The gonads, the lens of the eye, and the blood-forming organs are particularly radiosensitive. The annual dose limit for the skin, hands, and feet (extremities) is 50 rem per year. (Bushong, 8th ed., p. 557)

Front 13

Using a multifield image intensifier tube, which of the following input phosphor diameters will require the highest patient dose?
A.
35 cm
B.
25 cm
C.
17 cm
D.
12 cm

Back 13

The answer is D.

EXPLANATION: Multifield image intensifier tubes are usually either dual-field or tri-field and are designed this way in order to permit magnification imaging. As voltage is applied to the electrostatic focusing lenses, the focal point moves back—closer to the input phosphor—and a smaller portion of the input phosphor is utilized. As a result, the FOV decreases and magnification increases, producing better spatial resolution. At the same time, brightness is decreased requiring an increase in mA (therefore increased patient dose). This increase in mA increases image quality. It can be likened to an increase in signal-to-noise ratio (SNR), with mA being the signal

Front 14

Which of the following cell types has the greatest radiosensitivity?
A.
Nerve cells
B.
Muscle cells
C.
Spermatids
D.
Lymphocytes

Back 14

The answer is D.

EXPLANATION: Lymphocytes, a type of white blood cell concerned with the immune system, have the greatest radiosensitivity of all body cells. Spermatids are also highly radiosensitive, though not to the same degree as lymphocytes. Muscle cells have a fairly low radiosensitivity, and nerve cells are the least radiosensitive in the body (in fetal life, however, nerve cells are highly radiosensitive).

Front 15

The input phosphor of the image intensifier tube functions to convert
A.
kinetic energy to light.
B.
x-rays to light.
C.
electrons to light.
D.
fluorescent light to electrons.

Back 15

The answer is B.

EXPLANATION: The image intensifier's input phosphor receives the remnant radiation emerging from the patient and converts it into a fluorescent light image. Very close to the input phosphor, separated by a thin transparent layer, is the photocathode. The photocathode is made of a photoemissive alloy, usually an antimony and cesium compound. The fluorescent light image strikes the photocathode and is converted to an electron image that is focused by the electrostatic lenses to the output phosphor.

Front 16

Which acute radiation syndrome requires the largest exposure before any effects become apparent?
A.
hematopoietic
B.
gastrointestinal
C.
CNS
D.
skeletal

Back 16

The answer is C.

EXPLANATION: Radiation effects that appear days or weeks following exposure (early effects) are in response to high radiation doses; this is called acute radiation syndrome. These effects should never occur in diagnostic radiology; they occur only in response to much greater doses. Sufficient exposure of the hematologic system to ionizing radiation can result in nausea, vomiting, diarrhea, decreased blood cells count, and infection. Very large exposure of the GI system (1000–5000 rad) causes severe damage to the (stem) cells lining the GI tract. This can result in nausea, vomiting, diarrhea, blood changes, and hemorrhage. Exposure greater than 5000 rad are required to affect the normally resilient CNS. (

Front 17

Circuit devices that will conduct electrons in only one direction are
1. resistors.
2. valve tubes.
3. solid-state diodes.

Back 17

2 and 3 only

Front 18

Which type of articulation is evaluated in arthrography?
A.
Synarthrodial
B.
Diarthrodial
C.
Amphiarthrodial
D.
Cartilaginous

Back 18

The answer is B.

EXPLANATION: Diarthrodial joints are freely movable joints that distinctively contain a joint capsule. Contrast is injected into this joint capsule to demonstrate the menisci, articular cartilage, bursae, and ligaments of the joint under investigation. Synarthrodial joints are immovable joints, composed of either cartilage or fibrous connective tissue. Amphiarthrodial joints allow only slight movement. (

Front 19

Which of the following is an important consideration to avoid excessive metacarpophalangeal joint overlap in the oblique projection of the hand?
A.
Oblique the hand no more than 45°.
B.
Use a support sponge for the phalanges.
C.
Clench the fist to bring the carpals closer to the IR.
D.
Utilize ulnar flexion.

Back 19

Oblique the hand no more than 45°.

Front 20

In which type of monitoring device do photons release electrons by their interaction with air?
A.
Film badge
B.
Thermoluminescent dosimeter (TLD)
C.
Pocket dosimeter
D.
Optically stimulated luminescence (OSL) dosimeter

Back 20

The answer is C.

EXPLANATION: There are different types of monitoring devices available for the occupationally exposed. Ionization is the fundamental principle of operation of both the film badge and the pocket dosimeter. In the film badge, the film's silver halide emulsion is ionized by x-ray photons. The pocket dosimeter contains an ionization chamber (containing air), and the number of ions formed (of either sign) is equated to exposure dose. TLDs are personnel radiation monitors that use lithium fluoride crystals. Once exposed to ionizing radiation and then heated, these crystals give off light proportional to the amount of radiation received. OSL dosimeters are personnel radiation monitors that use aluminum oxide crystals. These crystals, once exposed to ionizing radiation and then subjected to a laser, give off luminescence proportional to the amount of radiation received

Front 21

Examples of synovial pivot articulations include the
1. atlantoaxial joint.
2. radioulnar joint.
3. temporomandibular joint.

Back 21

1, 2, and 3

Front 22

The sternoclavicular joints will be best demonstrated in which of the following positions?
A.
Apical lordotic
B.
Anterior oblique
C.
Lateral
D.
Weight-bearing

Back 22

The answer is B.

EXPLANATION: The (diarthrotic) sternoclavicular joints are formed by the medial (sternal) extremities of the clavicles and the clavicular notches of the manubrium (of the sternum). They can be demonstrated in the LAO and RAO positions. The LAO demonstrates the left sternoclavicular joint, while the RAO demonstrates the joint on the right. The patient is obliqued about 15° with the side of interest adjacent to the image recorder

Front 23

To demonstrate the glenoid fossa in profile, the patient is positioned
A.
45° oblique, affected side up.
B.
45° oblique, affected side down.
C.
25° oblique, affected side up.
D.
25° oblique, affected side down.

Back 23

The answer is B.

EXPLANATION: When viewing the glenoid fossa from the anterior, it is seen to angle posteriorly and laterally approximately 45°. To view it in profile, then, it must be placed so that its surface is perpendicular to the image recorder. The patient is positioned in a 45° oblique, affected side down, which places the glenoid fossa approximately perpendicular to the image recorder. The arm is abducted slightly, the elbow flexed, and the hand and forearm placed over the abdomen. The CR is directed perpendicular to the glenohumeral joint.

Front 24

An optically stimulated luminescence dosimeter contains which of the following detectors?
A.
Gadolinium
B.
Aluminum oxide
C.
Lithium fluoride
D.
Photographic film

Back 24

The answer is B.

EXPLANATION: There are different types of monitoring devices available for the occupationally exposed. The film badge has photographic film; the pocket dosimeter contains an ionization chamber; TLDs use lithium fluoride crystals. OSL dosimeters are personnel radiation monitors that use aluminum oxide crystals. These crystals, once exposed to ionizing radiation and then subjected to a laser, give off luminescence proportional to the amount of radiation received.

Front 25

Which of the following may be used as landmark(s) for an AP projection of the hip?
1. Two-inch medial to the anterior superior iliac spine (ASIS)
2. Prominence of the greater trochanter
3. Midway between the iliac crest and pubic symphysis

Back 25

1 and 2 only

Front 26

In the AP projection of an asthenic patient whose knee measures less than 19 cm from ASIS to tabletop, the central ray should be directed
A.
perpendicularly.
B.
5° medially.
C.
5° cephalad.
D.
5° caudad.

Back 26

The answer is D.

EXPLANATION: In the AP projection of the knee, the position of the joint space is significantly affected by the patient's overall body habitus and the distance between the ASIS and the tabletop. When the patient is of sthenic habitus with a distance of 19 to 24 cm between ASIS and tabletop, the central ray is directed perpendicularly. When the patient is of asthenic habitus with a distance of less than 19 cm between ASIS and tabletop, the central ray is directed 5° caudad. With a patient with a hypersthenic habitus and an ASIS-to-table measurement greater than 24 cm, the central ray is directed 5° cephalad

Front 27

With a patient in the PA position and the OML perpendicular to the table, a 15° to 20° caudal angulation would place the petrous ridges in the lower third of the orbit. To achieve the same result in a baby or a small child, it is necessary for the radiographer to modify the angulation to
A.
10° to 15° caudal.
B.
25° to 30° caudal.
C.
15° to 20° cephalic.
D.
3° to 5° caudal.

Back 27

A.
10° to 15° caudal.

Front 28

Which of the following combinations would deliver the least amount of heat to the anode of a 3-phase, 12- pulse x-ray unit?
A.
400 mA, 0.12 second, 90 kVp
B.
300 mA, 1/2 second, 70 kVp
C.
500 mA, 1/30 second, 85 kVp
D.
700 mA, 0.06 second, 120 kVp

Back 28

C. 500 mA, 1/30 second, 85 kVp

Front 29

Radiation output from a diagnostic x-ray tube is measured in which of the following units of measurement?
A.
rad
B.
rem
C.
roentgen
D.
becqueral

Back 29

C.
roentgen

Front 30

Which of the following personnel monitoring devices used in diagnostic radiography is considered to be the most sensitive and accurate?
A.
TLD
B.
Film badge
C.
OSL
D.
Pocket dosimeter

Back 30

The answer is C.

EXPLANATION: Ionization is the fundamental principle of operation of both the film badge and pocket dosimeter. In the film badge, the film's silver halide emulsion is ionized by x-ray photons. The pocket dosimeter contains an ionization chamber, and the number of ionizations taking place may be equated to exposure dose; it is accurate, but it is used only to detect larger amounts of radiation exposure. The TLD can measure exposures as low as 5 mrem, whereas film badges will measure a minimum exposure only as low as 10 mrem. TLDs contain lithium fluoride crystals that undergo characteristic changes upon irradiation. When the crystals are subsequently heated, they emit a quantity of visible (thermo)luminescence/light in proportion to the amount of radiation absorbed. The relatively new OSLs contain aluminum oxide crystals that also undergo characteristic changes upon irradiation. When the Al2O3 crystals are stimulated by a laser, they emit (optically stimulated) luminescence/light in proportion to the amount of radiation absorbed. OSLs can measure exposures as low as 1 mrem.

Front 31

Which of the following tissues is (are) considered to be particularly radiosensitive?
1. intestinal mucous membrane
2. epidermis of extremities
3. optic nerves

Back 31

1 only

Front 32

Which of the following x-ray circuit devices operate(s) on the principle of mutual induction?
1. High-voltage transformer
2. Filament transformer
3. Autotransformer

Back 32

1 and 2 only

Front 33

How does the use of rare earth intensifying screens contribute to lowering the patient dose?
1. It permits the use of lower mAs.
2. It permits the use of lower kVp.
3. It eliminates the need for patient shielding.

Back 33

1 only

Front 34

A backup timer for the AEC serves to
1. protect the patient from overexposure.
2. protect the x-ray tube from excessive heat.
3. increase or decrease master density.

Back 34

1 and 2 only

Front 35

Which of the following is a measurement of dose to biologic tissue?
A.
Roentgen (C/kg)
B.
Rad (Gy)
C.
Rem (Sv)
D.
RBE

Back 35

C.
Rem (Sv)

Front 36

Secondary radiation barriers usually require the following thickness of shielding:
A.
1/4-inch lead
B.
1/8-inch lead
C.
1/16-inch lead
D.
1/32-inch lead

Back 36

The answer is D.

EXPLANATION: Examples of primary barriers are the lead walls and doors of a radiographic room, that is, any surface that could be struck by the useful beam. Primary protective barriers of typical installations generally consist of walls with 1/16 inch (1.5 mm) lead thickness and 7 feet high.

Front 37

Which unit of exposure is described as 100 ergs of energy per gram of irradiated absorber?
A.
roentgen
B.
rad
C.
rem
D.
curie

Back 37

B.
rad

Front 38

Which of the following formulas would the radiographer use to determine the total number of HU produced with a given exposure using three-phase, six-pulse equipment?
A.
mA x time x kVp
B.
mA x time x kVp x 3.0
C.
mA x time x kVp x 1.35
D.
mA x time x kVp x 1.41

Back 38

C.
mA x time x kVp x 1.35

Front 39

What is the minimum requirement for lead aprons, according to CFR 20?
A.
0.05 mm Pb
B.
0.50 mm Pb
C.
0.25 mm Pb
D.
1.0 mm Pb

Back 39

C. 0.25 mm Pb
Lead aprons are secondary radiation barriers and must contain at least 0.25 (1/4) mm Pb equivalent, usually in the form of lead-impregnated vinyl (according to CFR 20). Many radiology departments routinely use lead aprons containing 0.5 mm Pb (the NCRP recommends 0.5 mm Pb equiv. minimum). These aprons are heavier, but they attenuate a higher percentage of scattered radiation

Front 40

Early symptoms of acute radiation syndrome include
1. leukopenia.
2. nausea and vomiting.
3. Cataracts.

Back 40

1 and 2 only

Front 41

Types of secondary radiation barriers include
1. the control booth.
2. lead aprons.
3. the x-ray tube housing.

Back 41

1, 2, and 3
Secondary radiation includes leakage and scattered radiation. The control booth wall is a secondary barrier; therefore, the primary beam must never be directed toward it. The x-ray tube housing must reduce leakage radiation to less than 100 mR/hour at a distance of 1 m from the housing. Lead aprons, lead gloves, portable x-ray barriers, and so on are also designed to protect the user from exposure to scattered radiation and will not protect her or him from the primary beam.

Front 42

The operation of personal radiation monitoring can be based on stimulated luminescence. Which of the following personal radiation monitors

function(s) in that manner?
1. OSL
2. TLD
3. Pocket dosimeter

Back 42

1 and 2 only

Front 43

Which of the following statements is/are true with respect to radiation safety in fluoroscopy?
1. Tabletop radiation intensity must not exceed 2.1 R/min/mA.
2. Tabletop radiation intensity must not exceed 10 R/min.
3. In high-level fluoroscopy, tabletop intensity up to 20 R/min is permitted.

Back 43

1, 2, and 3

Front 44

Lead aprons are worn during fluoroscopy to protect the radiographer from exposure to radiation from
A.
the photoelectric effect.
B.
Compton scatter.
C.
classical scatter.
D.
pair production.

Back 44

B. Compton scatter. In the photoelectric effect, a relatively low-energy photon uses all its energy to eject an inner-shell electron, leaving a vacancy. An electron from the shell above drops down to fill the vacancy and in doing so gives up a characteristic ray. This type of interaction is most harmful to the patient, as all the photon energy is transferred to tissue. In Compton scatter, a high-energy incident photon ejects an outer-shell electron. The incident photon is deflected with reduced energy, but it usually retains most of its energy and exits the body as an energetic scattered ray. This scattered ray will either contribute to image fog or pose a radiation hazard to personnel, depending on its direction of exit. In classical scatter, a low-energy photon interacts with an atom but causes no ionization; the incident photon disappears into the atom, and is then immediately released as a photon of identical energy but changed direction. Pair production is an interaction that occurs only at energies of 1.02 MeV, and therefore it does not occur in diagnostic radiography.

Front 45

What is used to account for the differences in ionizing characteristics of various radiations, when determining their effect on biologic material?
1. Radiation weighting factors (Wr)

2. Tissue weighting factors (Wt)

3. Absorbed dose

Back 45

1 only The Tissue Weighting Factor (Wt) represents the relative tissue radiosensitivity of irradiated material (eg, muscle vs intestinal epithelium vs bone, etc). The Radiation Weighting Factor (Wr) is a number assigned to different types of ionizing radiations in order to better determine their effect on tissue (eg, x-ray vs alpha particles). The Wr of different ionizing radiations is dependent on the LET of that particular radiation. The following formula is used to determine Effective Dose (E):

Effective Dose (E) = Radiation Weighting Factor (Wr ) x Tissue Weighting Factor (Wt ) x Absorbed Dose

Front 46

Protective devices such as lead aprons function to protect the user from
1. scattered radiation.
2. the primary beam.
3. remnant radiation.

Back 46

1 only

Front 47

Which of the following most effectively minimizes radiation exposure to the patient?
A.
Small focal spot
B.
Low-ratio grids
C.
Long source-image distance
D.
High-speed intensifying screens

Back 47

D.
High-speed intensifying screens

Front 48

A spinning top device can be used to evaluate
1. timer accuracy.
2. rectifier failure.
3. the effect of kVp on contrast.

Back 48

1 and 2 only

Front 49

Isotopes are atoms that have the same
A.
mass number but a different atomic number.
B.
atomic number but a different mass number.
C.
atomic number but a different electron number.
D.
atomic number and mass number.

Back 49

B.
atomic number but a different mass number.

Front 50

Which of the following is an acceptable approximate entrance skin exposure (ESE) for a PA chest radiograph?
A.
6 mR
B.
20 mR
C.
38 mR
D.
0.6 R

Back 50

B.
20 mR

Front 51

Late or long-term effects of radiation exposure are generally represented by which of the following dose-response curves?
A.
Linear threshold
B.
Linear nonthreshold
C.
Nonlinear threshold
D.
Nonlinear nonthreshold

Back 51

B.
Linear nonthreshold

Front 52

An increase in the kilovoltage applied to the x-ray tube increases the
1. percentage of high-energy photons produced.
2. exposure rate.
3. patient absorption.

Back 52

1 and 2 only

Front 53

The x-ray interaction with matter that is responsible for the majority of scattered radiation reaching the IR is
A.
the photoelectric effect.
B.
Compton scatter.
C.
classical scatter.
D.
Thompson scatter.

Back 53

B.
Compton scatter.

Front 54

Which type of dose–response relationship expresses radiation-induced leukemia?
A.
Nonlinear, nonthreshold
B.
Nonlinear, threshold
C.
Linear, nonthreshold
D.
Linear, threshold

Back 54

C.
Linear, nonthreshold

Front 55

Which of the following circuit devices operate(s) on the principle of self-induction?
1. Autotransformer
2. Choke coil
3. High-voltage transformer

A.
1 only
B.
1 and 2 only
C.
2 and 3 only
D.
1, 2, and 3

Back 55

1 and 2 only

Front 56

Immature cells are referred to as
1. undifferentiated cells.
2. stem cells.
3. genetic cells.

Back 56

1 and 2 only

Front 57

If the exposure rate at 3 feet from the fluoroscopic table is 40 mR/hr, what will be the exposure rate for 30 minutes at a distance of 5 feet from the table?
A.
7 mR
B.
12 mR
C.
14 mR
D.
24 mR

Back 57

The answer is A.

EXPLANATION: The intensity/exposure rate of radiation at a given distance from a point source is inversely proportional to the square of the distance. This is the inverse square law of radiation, and it is expressed in the following equation:

Front 58

Which of the following formulas would the radiographer use to determine the total number of heat units (HU) produced with a given exposure using 3-phase, 12-pulse equipment?
A.
mA x time x kVp
B.
mA x time x kVp x 3.0
C.
mA x time x kVp x 1.35
D.
mA x time x kVp x 1.41

Back 58

D.
mA x time x kVp x 1.41

Front 59

Which of the following is (are) associated with Compton scattering?
1. High-energy incident photons
2. Outer-shell electrons
3. Characteristic radiation

Back 59

1 and 2 only
Compton scattering occurs when a relatively high-energy incident photon uses part of its energy to eject an outer-shell electron, and in doing so changes its direction (is scattered). The energy retained by the scattered photon depends on the angle formed by the ejected electron and the scattered photon: The greater the angle of deflection, the less the retained energy. Compton scatter is very energetic scatter. It emerges from the patient and is responsible for scattered radiation reaching the image in the form of fog. Characteristic radiation is associated with the photoelectric effect.

Front 60

The National Council on Radiation Protection and Measurements (NCRP) has recommended what total equivalent dose limit to the embryo/fetus?
A.
0.05 rem
B.
0.5 rem
C.
50 mrem
D.
5000 mrem

Back 60

B.
0.5 rem

Front 61

Which of the following combinations would pose the most hazard to a particular anode?
A.
0.6 mm focal spot, 75 kVp, 30 mAs
B.
0.6 mm focal spot, 85 kVp, 15 mAs
C.
1.2 mm focal spot, 75 kVp, 30 mAs
D.
1.2 mm focal spot, 85 kVp, 15 mAs

Back 61

A.
0.6 mm focal spot, 75 kVp, 30 mAs

Front 62

Which of the following contributes most to patient dose?
A.
The photoelectric effect
B.
Compton scatter
C.
Classical scatter
D.
Thompson scatter

Back 62

A. The photoelectric effect
In the photoelectric effect, a relatively low-energy photon uses all its energy to eject an inner-shell electron, leaving a vacancy. An electron from the shell above drops down to fill the vacancy, and in doing so emits a characteristic ray. This type of interaction is most harmful to the patient, as all the photon energy is transferred to tissue. In Compton scatter, a high-energy incident photon uses some of its energy to eject an outer-shell electron. In doing so, the incident photon is deflected with reduced energy, but usually retains most of its energy and exits the body as an energetic scattered ray. The scattered radiation will either contribute to image fog or pose a radiation hazard to personnel, depending on its direction of exit. In classical scatter, a low-energy photon interacts with an atom but causes no ionization; the incident photon disappears in the atom, then immediately reappears and is released as a photon of identical energy but changed direction. Thompson scatter is another name for classical scatter.

Front 63

Reducing the number of repeat images is an important way to decrease patient exposure and can be accomplished by
1. good patient communication.
2. accurate positioning skills.
3. using AEC.

Back 63

1, 2, and 3

Front 64

What is the approximate entrance skin exposure (ESE) for the average AP supine lumbar spine radiograph?
A.
350 rad
B.
350 mrad
C.
35 rad
D.
35 mrad

Back 64

B.
350 mrad

Front 65

The effective energy of the x-ray beam is increased by increasing the
1. added filtration.
2. kilovoltage.
3. milliamperage.

Back 65

1 and 2 only

Front 66

An increase in total filtration of the x-ray beam will increase
A.
patient skin dose.
B.
beam HVL.
C.
image contrast.
D.
mR output.

Back 66

beam HVL.

Front 67

What is the intensity of scattered radiation perpendicular to and 1 m from the patient, compared to the useful beam at the patient's surface?
A.
0.01%
B.
0.1%
C.
1.0%
D.
10.0%

Back 67

B. 0.1%
patient is the most important radiation scatterer during both radiography and fluoroscopy. In general, at 1 m from the patient, the intensity is reduced by a factor of 1000, to about 0.1% of the original intensity. Successive scatterings can render the intensity to unimportant levels.

Front 68

Which of the following cells is the least radiosensitive?
A.
Myelocytes
B.
Myocytes
C.
Megakaryocytes
D.
Erythroblasts

Back 68

B. Myocytes

Front 69

Which of the following causes pitting, or many small surface melts, of the anode's focal track?
A.
Vaporized tungsten on the glass envelope
B.
Loss of anode rotation
C.
A large amount of heat to a cold anode
D.
Repeated, frequent overloading

Back 69

D.
Repeated, frequent overloading

Front 70

Classify the following tissues in order of increasing radiosensitivity.
1. Liver cells
2. Intestinal crypt cells
3. Muscle cells

Back 70

3, 1, 2

Front 71

The device used to change alternating current (AC) to unidirectional current is
A.
a capacitor.
B.
a solid-state diode.
C.
a transformer.
D.
a generator.

Back 71

The answer is B.

EXPLANATION: Some x-ray circuit devices, such as the transformer and autotransformer, will operate only on AC. The efficient operation of the x-ray tube, however, requires the use of unidirectional current, so current must be rectified before it gets to the x-ray tube. The process of full-wave rectification changes the negative half cycle to a useful positive half cycle. An x-ray circuit rectification system is located between the secondary coil of the high-voltage transformer and the x-ray tube. Rectifiers are solid-state diodes made of semiconductive materials such as silicon, selenium, or germanium that conduct electricity in only one direction. Thus a series of rectifiers placed between the transformer and x-ray tube functions to change AC to a more useful unidirectional current. (