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Question 1

maximum x-ray beam intensity when performing fluoroscopy

Answer 1

10 rads/min

Question 2

This component changes the magnification mode by changing the field of view (FOV).

Answer 2

Electrostatic lenses are located in the image intensifier and are used to focus electrons onto the output phosphor. These lenses are adjustable such that the higher the voltage applied across them the more focused the electron beam.

Question 3

The fraction of radiation available for image production in a detector element (DEL) is known as:

Answer 3

fill factor.

aka it describes the % of the detector element that is photosensitive

Typical fill factor (efficiency) of a DEL is 60-80% because some of the DEL area is taken up by readout electronics and data lines.

Question 4

This type of image receptor can use either direct or indirect methods to convert x-rays into an electrical charge

Answer 4

Flat panel detector

Direct detectors use a semiconductive material to convert x-rays -> electrical signal

Indirect detectors convert x-rays -> light photons -> electrical charge

Question 5

In digital imaging, adjusting the window level changes the:
a) Contrast
b) Pixel size
c) Matrix size
d) Pixel pitch

Answer 5

Contrast
Brighter images can be viewed by increasing the window level and darker images can be viewed by decreasing the window level.

Question 6

What is the minimum total filtration required in fluoroscopic equipment at normal operating voltage?

Answer 6

2.5 mm Al equivalent

Filters are used in fluoroscopic tubes to preferentially absorb less penetrating x-rays before they reach the patient. They are typically made of aluminum and must be at least 2.5 mm aluminum equivalent at normal operating voltage.

Question 7

According to California regulations, what is the minimum required total filtration that must be permanently fixed in the useful beam for fluoroscopy?

Answer 7

2.5 mm Al equivalent

Filters are used in fluoroscopic tubes to preferentially absorb less penetrating x-rays before they reach the patient. They are typically made of aluminum and must be at least 2.5 mm aluminum equivalent at normal operating voltage.

Question 8

How long does it take the human eye to recognize an image?

Answer 8

0.2 s

Question 9

How is resolution measured?

Answer 9

line pairs per millimeter (lp/mm)
The resolution of cesium iodide image tubes is approximately 4 lp/mm

Question 10

What is Quantum mottle

Answer 10

Grainy appearance in an image caused by 1) statistical fluctuation of absorbed x-ray photons. Additionally, when a 2) low number of photons are absorbed, any photons released as a result of 3) statistical fluctuations (mottle) will have a greater effect on image quality

Question 11

Which material(s) is suitable for use as a tabletop material in an X-ray or fluoroscopic system?
a) Lead
b) Carbon Fiber
c) Aluminum
d) Bakelite

Answer 11

B/C/D

Tabletop material must NOT attenuate the x-ray beam or else too few x-rays would pass through the table to obtain patient images.
Lead is the most common shielding material and is therefore a poor choice for a tabletop

Question 11

What is this formula is used to calculate?

ratio of the intensity of the output phosphor to the input exposure rate in millirads/second.

Answer 11

Conversion factor
=ratio of the OUTPUT phosphor intensity to the INPUT exposure rate.

Question 12

What exposure (Sv) must the State Department of Health be notified immediately if an occupational worker receives an exposure to the skin or extremities?

Answer 12

0.5 Sv

Question 13

Coordinating the video signal between the camera and monitor serves to:

Answer 13

Retrace an exact image - coordinating the video signal between the camera (synchronization) and monitor is necessary to avoid unnecessary flicker in the television picture

Question 13

What is the frequency with which an electrical image on the target of a vidicon tube is scanned?

Answer 13

30x/second

Question 13

If at one foot from the radiation source the intensity of exposure is 240 milliroentgens/hour and you remain at this location for 10 minutes, you will receive an exposure of 40 milliroentgens. What would be your exposure if you moved 2 feet away from the radiation source and remained there for 20 minutes?

a) 20 milliroentgens
b) 80 milliroentgens
c) 10 milliroentgens
d) 5 milliroentgens

Answer 13

The intensity of radiation varies inversely with the square of the distance

Doubling the distance from a radiation source reduces exposure by a factor of 4. The same duration of exposure would then lead to a dose of 40 divided by 4, or 10 mrads.

However, the exposure time in this question was also doubled. Exposure time is directly proportional to exposure dose and so doubling the time leads to double the dose, or 20 mrads

Question 13

This is the ratio of the intensity of the output phosphor to the input exposure rate in millirads/second.

Answer 13

Conversion factor

Question 14

What needs to be coordinated with the same frequency of X-ray pulses during cine film generation?
a) Camera shutters
b) Video signal
c) Electron gun

Answer 14

Camera shutters

Question 15

What is the purpose of the electron gun?

Answer 15

To produce a scanning electron beam

A vidicon camera is usually employed in fluoroscopic imaging as a way of converting an electron signal into a voltage. The most important parts of a vidicon camera are the target and the electron gun. The electron gun produces an electron beam in a vacuum and focuses it onto the photoconductive target to produce a television picture

Question 16

A diagnostic fluoroscopy exam usually uses around what dose rate?

Answer 16

1-5 rads/minute and should not exceed 5 rads/minute.
typically last 5-15min

Question 17

How do you get a reading from a pocket ionization chamber? (PIC)

Answer 17

self-read or it can be ready by a special device.

Question 18

What is the resolution of modern cesium iodide image intensifier tubes?

Answer 18

4 line pairs per millimeter (lp/mm)

In the past, zinc-cadmium was used, but this material limited resolution to 1-2 line pairs per millimeter.

Question 19

For routine fluoroscopy, what is the maximum tabletop x-ray exposure?

Answer 19

10 rads/minute, however, the recommendation is that it should not exceed 2.2 rads/minute for each mA of current at 80 kVp.

Question 20

Doubling the exposure AREA does what to the patient dose?

Answer 20

Patient and operator exposure is DIRECTLY proportional to the exposure area such that doubling the exposure area will double the patient and operator exposure

Question 21

How far the operator should be from the table

Answer 21

2 meters

Question 22

The safe distance that the fluoro table should be from the subject

Answer 22

12 inches = 30 cm

Question 23

What total filtration must be used in fluoroscopic tubes operating above 70 kVp?

Answer 23

2.5mm aluminum equivalent Filters are used in fluoroscopic tubes to preferentially absorb less penetrating x-rays before they reach the patient. They are typically made of aluminum and must be at least 2.5 mm aluminum equivalent at normal operating voltage

Question 24

What does increasing the kilovolt peak (kVp) and decreasing the milliamperage (mA) cause? a) Increased image contrast b) Increased quantum mottle c) Increased skin exposure d) Decreased skin exposure

Answer 24

Decreased skin exposure High kVp tend to reduce patient dose (dereased skin exposure) because the improved x-ray beam quality allows the use of lower x-ray tube current (mA).

Question 25

A non-threshold dose-effect relationship has a curve that: a) Is non-linear b) Is in the shape of an S c) Intersects the abscissa at the origin d) Does not intersect the abscissa at the origin

Answer 25

Intersects the abscissa at the origin @any dose, no matter how small, it will have some effect

Question 26

The f-number of the _____ denotes the speed of a camera. How does it affect light and patient exposure?

Answer 26

f-number = focal length/lens diameter A lower f-number is achieved by decreasing the focal length OR increasing the lens diameter. A lens with a shorter focal length will result in a smaller image with more concentrated light reaching the image plane. A lens with a larger diameter will allow more light to reach the image plane due to the larger area available for light to pass through Lower f-number = more light available to form an image = less exposure to the patient

Question 27

Which of the following are advantages of three-phase generators? (select all that apply) a) Close to constant potential b) High mA for very short exposures c) Higher effective kV d) Lower patient dose

Answer 27

A, B, and C Unfortunately, there is no improvement in patient dose with the use of these generators.

Question 28

This component converts an electrical signal into a visible image.

Answer 28

Monitor - The monitor contains the picture tube (aka Cathode-Ray-Tube), which takes the electrical signal from the camera control unit and converts it into a visible image.

Question 29

If the collimator is opened so that double the area is exposed, patient dose will:

Answer 29

double Patient and operator exposure is directly proportional to the exposure area such that doubling the exposure area will double the patient and operatore exposure.

Question 30

Increasing the kilovoltage peak (kVp) and decreasing the milliamperage (mA) causes: a) Decreased skin exposure b) Increased skin exposure c) Decreased internal organ exposure d) Increased image contrast

Answer 30

High kVp tend to reduce patient dose (decreased skin exposure) because the improved x-ray beam quality allows the use of lower x-ray tube current (mA).

Question 31

If the x-ray tube is fixed below the table in a system equipped with automatic brightness control, what effect will moving the image intensifier away from the patient have? (Select all) a) Decreases patient dose b) Increases patient dose c) Increases the number of X-rays intercepted by the image intensifier d) Decreases the number of X-rays intercepted by the image intensifier

Answer 31

increase the patient dose AND decreases the number of X-rays intercepted by the image intensifier Moving the image intensifier away from the patient will INCREASE the image size and INCREASE the patient dose and decrease the # of x-rays intercepted by the image intensifier. The image intensifier should be placed as close as possible to the patient to keep exposures low.

Question 32

Positioning sponges are ______ and positioning sandbags are _____. radiolucent vs radioopaque

Answer 32

Positioning sponges are radioLUCENT (looks clear) and positioning sandbags are radioOPAQUE (can be seen on Xray) example: lungs are radiolucent; bones are relatively radiopaque

Question 33

Doubling the exposure TIME increases the patient and operator dose by a factor of:

Answer 33

2 Patient and operator exposure is directly proportional to the exposure area such that doubling the exposure time will double the patient and operatore exposure

Question 34

What is the topic of the Biologic Effects of Ionizing Radiation (BEIR) report VII? a) Development of the linear, nonthreshold hypothesis b) Health effects of exposure to Radon c) Health effects of exposure to internally deposited alpha-emitters d) Health risks from exposure to low-level ionizing radiation

Answer 34

4) Health risks from exposure to LOW level ionizing radiation

Question 35

The ratio of the input phosphor diameter squared to the output phosphor diameter squared is the:

Answer 35

This is the definition of minification gain, which is the increase in brightness or intensity.

Question 36

As detector element (DEL) size decreases a) Pitch increases b) Pitch decreases c) Spatial resolution increases d) Spatial resolution decreases

Answer 36

Spatial resolution is inversely related to DEL size. As DEL size decreases, spatial resolution increases. Pitch is the distance between two adjacent DELs. As DEL size decreases, pitch also decreases.

Question 37

Laboratory and clinical methods will generally not show injury until an exposure of ____ rads is reached.

Answer 37

25 In general, at 25 rads or less, ordinary laboratory or clinical exposure shows no indications of injury with regards to short-term effects.

Question 38

The estimated skin entrance exposure from an anteroposterior (AP) abdominal film is:

Answer 38

100-500 millirads

Question 39

The visibility of mottle in a system is determined by: a) Resolution b) Contrast c) Sensitivity d) All of the above

Answer 39

Quantum mottle is the grainy appearance in an image caused by statistical fluctuation of absorbed x-ray photons. Mottle is more visible in high contrast, high resolution systems. Additionally, changing the sensitivity will lead to a different number of x-ray photons released by statistical fluctuation.

Question 40

A photocathode gives off _____ in proportion to the intensity of fluorescent light.

Answer 40

Electrons After x-rays pass through a patient they strike the image intensifier's input phosphor. This layer absorbs x-rays and converts their energy into light photons proportional to the intensity of the x-ray beam. The light photons impact on the photocathode, causing electrons to be given off. The accelerating anode then speeds up these electrons, where they are focused by the electrostatic lens onto the output phosphor

Question 41

How many horizontal scan lines do television monitors have?

Answer 41

525

Question 42

Which of the following is directly proportional to the exposure delivered to the patient? a) Kilovolt peak (kVp) b) Thickness of the filter c) Target-to-panel or target-to-table top distance d) Milliamperage (mA)

Answer 42

mA Patient exposure is strongly dependent on milliamperage. Increasing the kilovolt peak will often reduce patient exposure by allowing a lower mA setting

Question 43

Which of the following terms refers to the value given to a pixel to signify the gray level? a) Pixel size b) Bit depth c) Field of view d) Pixel number

Answer 43

Bit depth A pixel is the smallest element of a digital image and is two dimensional. Pixels can be characterized by their location, size, and value. The matrix size describes the number of pixels. The size of a pixel is the smallest detail visible in an image. A pixel can be assigned a value, known as bit depth, to denote gray or color level. Bit depth is the number of bits used to encode pixel color or gray level. Images with greater bit depths will have greater contrast resolution.

Question 44

The bucky slot cover (which is directly in line with the fluoroscopist's gonads) must be covered with at least _____ lead equivalent material.

Answer 44

0.25

Question 44

Scattered radiation exposure at 3 feet from the patient could be as high as: a) 1 millirad (0.001 centigray) per hour b) 10 millirads (0.01 centigray) per hour c) 50 millirads (0.05 centigray) per hour d) 250 millirads (0.25 centigray) per hour e) 1,000 millirads (1 centigray) per hour

Answer 44

50 millirads (0.05 centigray) per hour

Question 45

In mobile (c-arm) fluoroscopy what is the minimum required source to skin distance (SSD)? a) 10 cm b) 15 cm c) 20 cm d) 25 cm e) 30 cm

Answer 45

30 cm

Question 46

The ability to differentiate small objects as separate images (line pairs per millimeter) is: a) Brightness b) Resolution c) Contrast d) Distortion

Answer 46

resolution

Question 47

Where must the Bucky tray be located during fluoroscopy? a) Does not matter b) At the foot of the exam table c) At the head of the exam table d) It depends on the exam

Answer 47

b) At the foot of the exam table

Question 48

This term refers to the ability of the human eye to perceive fine detail: a) Visual acuity b) Photopic vision c) Scotopic vision d) Integration time

Answer 48

Visual acuity

Question 49

What is the purpose of image intensified fluoroscopy? a) Dynamic viewing (angiography) b) Real time viewing (live fluoroscopy) c) Transient image viewing d) All of the above

Answer 49

Image intensified fluoroscopy, or modern fluoroscopy, was developed to allow real-time and dynamic viewing of x-rays as well as to quickly view transient images during exams

Question 50

What is an erg? a) A unit of energy used to denote work b) A type of x-ray machine c) A unit of absorbed dose d) A unit of exposed dose

Answer 50

A unit of energy used to denote work The rad was originally described as the dose necessary to cause 100 ergs of energy to be absorbed by 1 gram of tissue. If 3 grams of tissue absorbs 300 ergs, then each gram absorbs 100 ergs. Since 1 rad is equal to 100 ergs per gram of tissue, making the dose 1 rad. Syllabus pg 132.

Question 51

Which of the following is considered Primary Radiation? a) Leakage radiation b) Remnant radiation c) Useful x-ray beam d) Scattered radiation e) Stray radiation

Answer 51

Primary radiation is that which comes directily from the useful beam. Leakage and scatter radiation are considered secondary radiation.

Question 52

Increasing the filtration in an x-ray system will have what effect? (select all that apply) a) Increases the kVp of the x-ray beam b) Removes useless low-energy x-rays c) Decreases intensity of x-ray beam d) Increases patient dose

Answer 52

B + C Filtration is added to remove low energy x-rays from the beam (thereby decreasing the intensity of the x-ray beam), because these x-rays increase patient dose without significant improvement in image quality.

Question 53

A 0.50 mm lead equivalent apron will reduce 100 kVp radiation exposure by how much? a) 66% b) 75% c) 99% d) 99.9%

Answer 53

0.5 mm lead equivalent will reduce 100 kVp primary beam radiation exposure by 75%. @ 50 kVp it will reduce radiation exposure by 99.9%.

Question 54

Maximizing differential tissue absorption to produce high-quality fluoroscopic images is done by choosing the proper: a) Milliamperage (mA) b) Peak kilovoltage (kV) c) Exposure time d) Source to object distance

Answer 54

Peak kilovoltage (kV) Kilovoltage peak (kVp) determines the penetrating ability of x-rays and proper selection is important so that effective x-ray energy will result in maximum differential tissue absorption. High kVp tends to reduce patient dose and improve x-ray beam quality. Differential absorption in the patient, however, increases with lower kVp. Lowering the kVp has the downside of increasing patient dose and so selecting the ideal kVp for high quality images yet low patient dose is crucial.

Question 55

Quadrupling the exposure time increases the patient exposure by how much? a) 2 times b) 4 times c) 16 times d) It does not change the dose

Answer 55

Patient and operator exposure is directly proportional to the exposure area such that quadrupling the exposure time will quadruple the patient and operatore exposure.

Question 56

What material are thermoluminescent dosimeters (TLD) made from? a) Zinc sulfide b) Tungsten c) Calcium phosphate d) Lithium Fluoride

Answer 56

Lithium Fluoride

Question 57

The half-value layer (HVL) is a characteristic of an x-rays: a) Quantity b) Quality c) Resolution d) Brightness

Answer 57

Quality The concept of half-value layer is important in shielding, where it guides material choice to attenuate x-rays. The quality of x-rays is characterized by the half-value layer

Question 58

The following are components of a closed-circuit television system: (select all that apply) a) Vidicon camera b) Camera control unit c) Monitor d) Image intensifier

Answer 58

A closed-circuit television system consists of a camera, camera control unit and monitor. The image intensifier is part of the x-ray system

Question 59

What is the equation is used to calculate pixel size?

Answer 59

FOV / matrix As the "field of view" increases, the pixel size increases. Similarly, as the matrix size decreases, the pixel size increases

Question 60

At what height above the tabletop should an unexposed border on the fluoroscopic screen be visible when the collimators are fully open?

Answer 60

14" For automatic collimating devices, an exposed border should be visible at all heights above the tabletop

Question 61

Lower image quality at low radiation doses is a result of: a) X-ray generator b) Loss of signal in closed circuit wires c) X-ray's moving too slow through the patient d) Quantum mottle

Answer 61

Quantum mottle is the grainy appearance in an image caused by statistical FLUCTUATIONS of absorbed x-ray photons. A large decrease in the number of x-ray photons would cause a great deterioration in image quality. Mottle is also more visible in high contrast, high resolution systems. Additionally, changing the sensitivity will lead to a different number of x-ray photons released by statistical fluctuation

Question 62

Using a tighter collimation to reduce the field of view will have what effect on image brightness? a) The image brightness will be reduced. b) The image brightness will be increased. c) The image brightness will not change. d) The image will become brighter proportionally to the change in field of view.

Answer 62

The image brightness will not change. Collimation refers to the restriction of the useful x-ray beam to an area of interest. The radiation dose rate, however, is independent of the x-ray beam size and so the image brightness will not change by collimating the beam. A tighter collimation will reduce the patient x-ray exposure because a lower volume of radiation will be incident on the patient

Question 63

This area is defined as one in which an individual could receive a dose equivalent >1 mSv in 1 hour (or 0.1 rem in 1 hour) at 30 cm a) Exposure area b) Radiation area c) Ultra high radiation area d) High radiation area

Answer 63

High radiation area

Question 64

This area is defined as one in which an individual could receive a dose equivalent >0.05 mSv in 1 hour (or 0.005 rem in 1 hour) at 30 cm a) Exposure area b) Radiation area c) Ultra high radiation area d) High radiation area

Answer 64

Radiation area

Question 65

What is the function of automatic brightness control? a) Keep the light output of the image intensifier constant b) Conserve energy by reducing x-ray production c) Maintain a constant dose rate to the patient d) Keep the camera tube target voltage constant

Answer 65

keeps the light output of the image intensifier constant over variations of patient attenuation (different tissue density and thickness), preserve image contrast/minimize image noise, and keep patient dose within regulation requirement of 10 rads/min

Question 66

Which setting controls the penetrating ability of x-rays in a fluoroscopic system? a) Milliamperage (mA) b) Kilovoltage peak (kVp) c) Brightness d) Contrast

Answer 66

kVp is a measure of tube potential that determines the penetrating ability of x-rays. Producing high-quality fluoroscopic images depends on proper selection of kVp

Question 67

What type of radiation do secondary barriers protect against? (select all that apply a) Leakage radiation b) Scattered radiation c) Primary radiation d) Useful beam e) Stray radiation

Answer 67

A/B/E Secondary barriers protect against stray radiation, which includes leakage and scattered radiation

Question 68

How much does brightness gain deteriorate each year due to the "aging" of the input and output screen phosphors? a) 5% b) 10% c) 25% d) 50%

Answer 68

10%

Question 68

Increasing the filtration in an x-ray system will have what effect? (select all that apply) a) Increases the kVp of the x-ray beam b) Removes useless low-energy x-rays c) Decreases intensity of x-ray beam d) Increases patient dose

Answer 68

B/C Filtration is added to remove low energy x-rays from the beam, because these x-rays increase patient dose without significant improvement in image quality.

Question 69

An x-ray tube outputs 4 milliroentgens (mR) per one milliampere-second (mAs) at a distance of 40 inches. What will the radiation exposure be at 80 inches from the x-ray tube (in mR/mAs)? a) 1 b) 2 c) 8 d) 16

Answer 69

1 The intensity of an x-ray beam varies with the square of the distance from the x-ray source. To calculate the absorbed dose at a distance farther from the x-ray tube you multiply the original intensity (4 mR) by the ratio of the distances squared 4(40^2/80^2) = 4(1600/6400) = 4(1/4) = 1

Question 69

Arguably the most important action to reduce radiation exposure is the use of appropriate:

Answer 69

Collimation

Question 70

The conversion of light to electrons is done by: a) Output phosphor b) Photomultiplier tube c) Photocathode d) Input phosphor

Answer 70

Photocathode

Question 71

Total Brightness Gain is defined as: a) Intensity of output phospor divided by millirads/second b) Minification gain x flux gain c) The increase in light photons due to the conversion efficiency of the output screen d) Flux gain squared e) Input screen diameter divided by output screen diameter

Answer 71

Total Brightness Gain = minification gain and flux gain Total brightness gain is the product of minification gain and flux gain. Minification gain is increased by increasing the size of the input screen or decreasing the size of the output screen. Flux gain is increased by increasing the conversion of electrons to light at the output screen.

Question 72

Which matrix size should produce the best spatial resolution? a) 32 x 32 b) 64 x 64 c) 128 x 128 d) 256 x 256

Answer 72

D) 256 x 256 Spatial resolution increases as matrix size increases and pixel size decreases, if all other factors are held constant.

Question 73

What is the maximum exposure rate allowed for fluoroscopic equipment manufactured after August 1, 1974, with automatic exposure controls (AEC)? a) 10 rads/minute b) 7.5 rads/minute c) 1 rad/minute d) 2.2 rads/minute e) 5 rads/minute

Answer 73

The allowable exposure rate in equipment WITH automatic exposure control is 10 rads/minute

Question 74

The target-to-table top distance shall be at least: a) 10" b) 12" c) 18" d) 24"

Answer 74

12" (but should be 18" or more)

Question 75

Film badges are used because: (select all that apply) a) They allow immediate reading of exposure by the operator b) They provide a record of exposure c) They measure operator exposure d) They are the only way to measure radiation exposure e) They protect the operator from exposure

Answer 75

b) They provide a record of exposure c) They measure operator exposure

Question 76

This part of a fluoroscopic system keeps the light output of the image intensifier constant over variations of patient thickness and density. a) Camera control unit b) Control grid c) Automatic brightness stabilization d) Focusing coil

Answer 76

Automatic brightness stabilization (ABS) aka automatic brightness control (ABC) keeps the light output of the image intensifier constant over variations of patient attenuation (different tissue density and thickness).

Question 77

Which of the following is used to compare the spatial resolution of imaging systems? a) Detector element size b) Bit depth c) Modulation Transfer Function (MTF) d) Focal spot size

Answer 77

Modulation Transfer Function (MTF) MTF is a measurement of the resolution and contrast of an imaging system and is used as quality assurance to compare systems.

Question 78

A lower f-number means that more _____ is available to form an image. a) Contrast b) Resolution c) Time d) Light

Answer 78

Light f-number = focal length/lens diameter A lower f-number is achieved by decreasing the focal length OR increasing the lens diameter. A lens with a shorter focal length will result in a smaller image with more concentrated light reaching the image plane. A lens with a larger diameter will allow more light to reach the image plane due to the larger area available for light to pass through Lower f-number = more light available to form an image = less exposure to the patient

Question 79

What is the exposure dose if 500 ergs of x-rays are absorbed by 5 grams of tissue? a) 1 rad b) 3 rads c) 50 rads d) 5 rads

Answer 79

a) 1 rad An erg is a unit of energy used to denote work. The rad was originally described as the dose necessary to cause 100 ergs of energy to be absorbed by 1 gram of tissue; therefore 1 rad = 100 ergs per gram of tissue If 5 grams of tissue absorbs 500 ergs, then each gram absorbs 100 ergs. Thus, the exposure dose is 1 rad

Question 80

Which type of contrast is reduced by increasing the kilovolt peak (kVp)? a) Detector contrast b) Subject contrast c) Characteristic contrast d) Brightness contrast

Answer 80

Subject contrast Overall contrast is dependent on the subject contrast and the detector contrast. The subject contrast is reduced by increasing the kVp

Question 81

What film size in spot filming cameras results in the greatest dose to the patient? a) 25 mm b) 70 mm c) 90 mm d) 105 mm

Answer 81

d) 105mm As film size increases so the image quality, but also the radiation dose to the patient! So 105 mm film would result in the greatest dose to the patient

Question 82

During digital subtraction angiography (DSA), this technique is used to combine multiple frames of a sequence to allow all vessels to be visualized in one image. a) Image summation b) Temporal framing c) Edge enhancement d) Vessel calibration

Answer 82

Image summation combines multiple frames of a sequence to allow all vessels to be visualized in one image.

Question 83

This occurs when an incident x-ray photon is annihilated near the nucleus of an absorbing atom with the subsequent production of an electron and a positron. a) Compton scattering b) The photoelectric effect c) Pair production d) Inverse Compton scattering

Answer 83

Pair production There are three ways in which energy is lost during x-radiation. 1) photoelectric effect - collision occurs between an x-ray photon and an INNER orbital electron. 2) Compton scattering - interaction occurs between an x-ray photon and an OUTER orbital electron. 3) pair production - an incident x-ray photon is annihilated near the nucleus of an atom and an electron and positron pair are emitted

Question 84

The magnitude of the effect of radiation on a patient is primarily dependent on: a) The total area exposed b) Shielding c) The patient's age d) The tissue type

Answer 84

The extent of the effect of radiation exposure to patients is primarily dependent upon the total area exposed.

Question 85

What is electron intensification? a) process in the image intensifier where electrons are accelerated from the photocathode to the output phosphor b) process in the x-ray gun where electrons are accelerated from the photocathode to the output phosphor c) process in the x-ray gun where the tungsten filament is cooled and a very low voltage is applied between the cathode and anode d) process in the image intensifier where the tungsten filament is cooled and a very low voltage is applied between the cathode and anode

Answer 85

A Electrons given off by the photocathode are sped up by the accelerating anode as they travel to the output phosphor

Question 86

How often should the automatic brightness control (ABC) mode be monitored with a designated phantom? a) Weekly b) Monthly c) Yearly d) Never

Answer 86

Weekly

Question 87

How is the overall resolution of an imaging system expressed? a) Flux gain b) Modulation transfer function (MTF) c) Line pairs per millimeter (lp/mm) d) Line raster patterns

Answer 87

Resolution is expressed in terms of its modulation transfer function (MTF), with a perfect system having an MTF of 1. The overall MTF of a system is the product of the MTF of each of it's components, for example the image intensifier and TV camera.

Question 88

Film badge readings are recorded using what unit of measurement? a) Gray b) kVp c) Erg d) Sievert e) mA

Answer 88

Radiation dose equivalent is monitored using Sievert.

Question 89

Which of the following is not part of a c-arm (mobile) fluoroscopy system? a) Monitor b) X-ray generator c) Bucky slot cover d) Image intensifier

Answer 89

Bucky slot cover

Question 90

What total filtration must be used in fluoroscopic tubes operating above 70 kVp? a) 2.5mm aluminum equivalent b) 3.0 mm aluminum equivalent c) 1.0 mm aluminum equivalent d) 0.25 mm aluminum equivalent.

Answer 90

2.5mm Filters are used in fluoroscopic tubes to preferentially absorb less penetrating x-rays before they reach the patient. They are typically made of aluminum and must be at least 2.5 mm aluminum equivalent at normal operating voltage.

Question 91

This type of body habitus includes an athletic build and is the most common in the general population. a) Hyposthenic b) Asthenic c) Hypersthenic d) Sthenic

Answer 91

Body habitus types used in radiography include sthenic, hypersthenic, asthenic, and hyposthenic. Sthenic - athletic build; 50% Hypersthenic - large and heavy, have high lungs and heart, a transverse stomach; 5% Asthenic - slender with a bony framework, long narrow thorax, low long stomach; 10% Hyposthenic - slightly less robust than sthenic, have a stomach that sits higher in the abdomen, 35%

Question 92

A television monitor consists of: (select all that apply) a) A cathode ray tube b) A contrast control function c) A brightness control function d) A picture tube

Answer 92

A television monitor consists of a cathode ray tube (aka picture tube), as well as control functions for contrast and brightness

Question 93

What is the definition of air kerma? a) The radiation dose absorbed by the skin where the x-ray beam enters. b) The amount of energy transferred from x-rays to charged particles per unit mass of air c) The amount of energy reflected from a patient after x-ray exposure d) The amount of energy transferred from x-rays to charged particles per unit mass of tissue

Answer 93

b) The amount of energy transferred from x-rays to charged particles per unit mass of air; measured in grey Kerma (kinetic energy released in matter) is the amount of energy transferred from incident x-rays to charged particles per unit mass. Air kerma is where the unit of mass is air.

Question 94

What are the specified parameters to measure fluoroscopy exposure rates using a phantom? a) Maximum 5 rads/minute, 15 cm from the image intensifier, using a phantom 9 inches of water b) Maximum 3 rads/minute, 30 cm from the image intensifier, using a phantom 9 inches of water c) Maximum 3 rads/minute, 15 cm from the image intensifier, using a phantom 9 inches of water d) Maximum 5 rads/minute, 30 cm from the image intensifier, using a phantom 9 inches of water

Answer 94

d) Maximum 5 rads/minute, 30 cm from the image intensifier, using a phantom 9 inches of water Fluoroscopic exposure rates should not exceed 5 rads/minute (5 centigray/minute) as measured at 30 cm from the input surface of the image intensifier. For an exposure rate measurement a phantom of 9 inches of water or 7.9 inches of Lucite should be used to simulate a patient.

Question 95

Which frame per second (f/s) rates are possible with cinefluorography? a) 30, 60, & 90 b) 30, 90, & 120 c) 7.5, 15, & 30 d) All of the above

Answer 95

d) all of the above Cine cameras can be operated at many different speeds, but are most commonly operated at 30 frames per second. Possible frequencies are divisions of 60

Question 96

Roentgen is a unit of: a) Absorbed dose b) Exposure c) Dose equivalent d) Energy e) Dose rate f) Emitted dose

Answer 96

b) exposure Roentgen is a unit of exposure that describes the ionization of atoms by x-rays. The roentgen only tells us how many ion pairs are formed, but does not tell us how much radiation is absorbed. Absorbed dose is used to express the amount of radiation absorbed by tissue. Units of absorbed dose include Gray and Rad. Dose equivalent was devised due to the fact that the same absorbed dose in rads delivered by different kinds of radiation does not produce the same degree of biological effects. Units of dose equivalent include Sievert and Rem

Question 97

A "dead-man" fluoroscopic switch: (select all that apply) a) Stops exposure when pressure is applied b) Stops exposure when pressure is released c) Can be a foot pedal

Answer 97

B + C A dead-man switch is one which is always off UNLESS it is pressed. Switches in conventional fluoroscopic systems can include foot pedals

Question 98

Which of the following is/are characteristics of contrast media? (select all that apply) a) Low toxicity b) High toxicity c) Low atomic number d) High atomic number

Answer 98

Contrast media are liquid substances with relatively low toxicity (such as barium or iodine) + possess high atomic numbers and so can DECREASE the transmission of x-rays

Question 99

Mottle of an image can be adjusted by changing the: (select all that apply) a) Kilovolt peak (kVp) b) Milliamperage (mA) c) Exposure factors d) Number of available X-ray photons

Answer 99

All of the above. Quantum mottle is the grainy appearance in an image caused by statistical fluctuation of absorbed x-ray photons. Mottle can be adjusted by changing exposure factors (kVp and mA). Increasing exposure (increasing the number of x-ray photons) will DECREASE mottle

Question 100

What must be done to the video signal when the electron beam produces a voltage that is sent to the television camera? (select all that apply) a) It must be synchronized b) Nothing c) It must be narrowed d) It must be amplified

Answer 100

A+D The output phosphor of an image intensifier tube is typically coupled to a television camera, which converts the electron signal into a video signal. This signal is transmitted through a cable to the camera control unit, where it is amplified and forwarded to the television monitor. The camera control unit also focuses and synchronizes the video signal

Question 101

This occurs when image intensity is greater at the center of an image. a) Quantum mottle b) Lag c) Vignetting d) Flux gain

Answer 101

A fall off in brightness at the periphery of an image is called vignetting.

Question 102

What is the typical milliampere (mA) usage during spot filming? a) 0.5-1 b) 1-5 c) 10-50 d) Over 100

Answer 102

Spot films are images taken during an examination using much higher mA setting, typically over 100.

Question 103

Roentgen is a measure of: a) Absorbed dose b) Exposure c) Energy d) Dose equivalent e) Dose rate

Answer 103

b) exposure Roentgen is a unit of exposure that describes the ionization of atoms by x-rays. The roentgen only tells us how many ion pairs are formed, but does not tell us how much radiation is absorbed. Absorbed dose is used to express the amount of radiation absorbed by tissue. Units of absorbed dose include Gray and Rad. Dose equivalent was devised due to the fact that the same absorbed dose in rads delivered by different kinds of radiation does not produce the same degree of biological effects. Units of dose equivalent include Sievert and Rem

Question 104

What is the limit for leakage radiation from a fluoroscopic x-ray tube housing? a) 50 mR at 1 meter b) 100 mR at 1 meter c) 1,000 mR at 1 meter d) 2.2 rad at 1 meter

Answer 104

100 mR at 1 meter

Question 105

During mobile (c-arm) fluoroscopy, decreasing the source to skin distance (SSD) does what to the entrance skin exposure (ESE)? a) Does not change it b) Increases it c) Decreases it d) Has no effect

Answer 105

Decreasing the source to skin distance (SSD) places the x-ray source closer to the patient and increases patient radiation exposure

Question 106

This term refers to the frequency range of a video signal: a) Contrast b) Bandpass c) Lowpass d) Highpass

Answer 106

Bandpass A television image is an exact representation of the electrical image coming from the target of the vidicon tube, and is scanned 30 times/second. bandpass/bandwidth also refers to the total # of cycles per second available for display by the television camera

Question 107

Which of the following are advantages of three-phase generators? (select all that apply) a) Close to constant potential b) High mA for very short exposures c) Higher effective kV d) Lower patient dose

Answer 107

a/b/c Three-phase generators and high frequency generators are advantageous because they provide a near constant potential, a higher mA (which is useful in angiography and spot filming), and a higher effective kV. Unfortunately, there is no improvement in patient dose with the use of these generators

Question 108

What is the normal viewing distance for binocular vision? a) 1 to 5 inches b) 4 to 8 inches c) 12 to 15 inches d) 16 to 24 inches

Answer 108

C The normal viewing distance of an image is 12 to 15 inches and the time required for the recognition of an image is 0.2 seconds

Question 109

Mobile C-arm fluoroscopy systems require all of the following EXCEPT: a) A primary protective barrier b) A dead-man switch c) Protective curtains d) A locking system between the tube and image intensifier

Answer 109

Basic regulations of mobile C-arm fluoroscopy systems include: - a locked system where the x-ray tube is always aimed at the image intensifier - a collimator - a dead-man switch - a source to skin distance of at least 12 inches.

Question 110

In digital imaging, if the field of view (FOV) is held constant and the matrix size decreases, which of the following occurs? (select all that apply) a) Pixel size decreases (chosen) b) Pixel size increases c) Spatial resolution increases (chosen) d) Spatial resolution decreases

Answer 110

Pixel size increases + Spatial resolution decreases Pixel size = FOV/matrix As the matrix size increases or the FOV decreases, the pixel size decreases. This leads to an increase in spatial resolution. FOV and matrix, however, are independent of one another.

Question 111

What is the maximum kilovoltage peak (kVp) that is typically used during fluoroscopy? a) 50 kVp b) 100 kVp c) 150 kVp d) 200 kVp

Answer 111

150 kVp

Question 112

A grainy or blotchy appearance of a fluoroscopic image is a result of: (select all that apply) a) Statistical fluctuations b) Quantum mottle c) Poor contrast d) Low number of absorbed photons

Answer 112

A+B+D

Question 114

Around what acute dose of radiation do cataracts form? a) 5 rads b) 50 rads c) 200 rads d) 1000 rads

Answer 114

c) 200 rads The dose necessary to form cataracts in humans is thought to be on the order of several hundred rads of acute x-rays.

Question 115

The following are true regarding image "lag": (select all that apply) a) Inherent problem of vidicon television cameras (chosen) b) Occurs from rapid movement of the TV camera during fluoroscopy (chosen) c) Is a result of the finite amount of time need for an image to build up and decay d) Is a result of the longer time necessary for brightness to appear in an image

Answer 115

A+B+C Lag is an undesirable property of most vidicon tubes that results when the fluoroscopic tower is moved rapidly. Lag occurs because it takes a certain amount of time for the image to build up and decay on the vidicon target

Question 116

Which of the following is a licentiate? a) Radiographer b) Radiologic Technologist c) Physician d) Anyone with a fluoroscopy license

Answer 116

Physician Licentiate refers to physicians who may use and supervise the use of fluoroscopic and ancillary equipment

Question 117

Electrons are focused by the: a) Input phosphor b) Output phosphor c) Electrostatic lens d) Accelerating anode

Answer 117

Electrostatic lens After x-rays pass through a patient they strike the image intensifier's input phosphor. This layer absorbs x-rays and converts their energy into light photons proportional to the intensity of the x-ray beam. The light photons impact on the photocathode, causing electrons to be given off. The accelerating anode then speeds up these electrons, where they are focused by the electrostatic lens onto the output phosphor.

Question 118

The contrast on the television monitor should be set so that: a) The darkest object is just below the black level b) The brightest object is just below the black level c) To maximize the visibility of the object, even if there is a large increase in noise d) The bright objects are just below the white level e) The bright objects white out details of the image

Answer 118

a) The darkest object is just below the black level Television monitor contrast is set based on the darkest object on the screen. This allows the remaining objects to also be visible on the screen.

Question 119

lowering kVP does what to the patient dose

Answer 119

increases Kilovoltage peak (kVp) determines the penetrating abillity of x-rays and proper selection is important so that effective x-ray energy will result in maximum differential tissue absorption. High kVp tends to reduce patient dose and improve x-ray beam quality. Lowering the kVp has the downside of increasing patient dose b/c it results in differential absorption in the patient

Question 120

Doubling the exposure time increases the patient and operator dose by a factor of: a) 2 b) 4 c) 8 d) 16 e) It does not change the dose

Answer 120

2 Patient and operator exposure is directly proportional to the exposure area such that doubling the exposure time will double the patient and operatore exposure

Question 121

A filter is: a) A material that absorbs less penetrating x-rays from the useful beam b) A spacer to help set the target-to-film distance c) A device used to reduce the amount of high penetrating radiation d) A device used to reduce scattered radiation

Answer 121

a) A material that absorbs less penetrating x-rays from the useful beam

Question 122

At what height above the tabletop should an unexposed border on the fluoroscopic screen be visible when automatic collimating devices are used? a) 1 inch b) 6 inches c) 14 inches d) All heights

Answer 122

D - all heights An unexposed border must be visible when the screen carriage is positioned 14 inches above the tabletop and collimators are fully opened and at all heights when automatic collimating devices are used

Question 123

How do you adjust the luminescence of a TV image? (select all that apply) a) Adjusting the contrast on the TV b) Cannot be adjusted c) Increasing the room lighting d) Adjusting the brightness on the TV

Answer 123

a/d) Adjusting the CONTRAST + BRIGHTNESS on the TV Luminescence refers to the emission of light from an object. To increase the luminescence on a TV image you can change the contrast to make light structures lighter, or increase the brightness on the monitor. Adjusting the room lighting will make the image easier to see, however, this does not change anything on the TV image.

Question 124

Increasing the voltage in an image intensifier tube: (select all that apply) a) Compresses the electron beam b) Reduces the available input surface c) Changes the image from mag to standard mode d) Moves the crossover point to further away from the output phosphor

Answer 124

A/B/D

Question 125

In digital imaging, adjusting the window level changes the: a) Contrast b) Pixel size c) Matrix size d) Pixel pitch

Answer 125

a) Contrast Adjusting the window level in digital imaging changes the contrast. Brighter images can be viewed by increasing the window level and darker images can be viewed by decreasing the window level.

Question 126

What does increasing the kilovolt peak (kVp) and decreasing the milliamperage (mA) cause? a) Increased image contrast b) Increased quantum mottle c) Increased skin exposure d) Decreased skin exposure

Answer 126

d) Decreased skin exposure High kVp tend to reduce patient dose (decreased skin exposure) because the improved x-ray beam quality allows the use of lower x-ray tube current (mA).

Question 127

What components make up the target assembly of a television camera tube? (select all that apply) a) Detecting coil b) Target c) Signal plate d) Glass face plate e) Focusing coil

Answer 127

B/C/D The target assembly consists of a glass face plate, a signal plate, and a target

Question 128

Which camera type has the greatest lag? a) Plumbicon camera b) Vidicon camera c) Charge-Coupled Device (CCD)

Answer 128

b) Vidicon camera Vidicon camera tubes have the greatest lag because it takes time for the image to build up and decay on the vidicon target

Question 129

At what height above the tabletop should an unexposed border on the fluoroscopic screen be visible when the collimators are fully open? a) 1 inch b) 6 inches c) 14 inches d) All heights

Answer 129

c) 14 inches

Question 130

Pincushion distortion is a result of: a) Poor tissue penetration b) Projecting an image formed on a curved input phosphor to a flat output phosphor c) Unequal illumination d) Light scatter e) Positioning the patient too close to the xray tube

Answer 130

Pincushion distortion results from projecting the image formed on a curved input phosphor onto a flat output phosphor. This results in a slightly higher magnification of the input image towards the edge of the screen

Question 131

The purpose of the Radiation Control for Health and Safety Act of 1968 was to: (select all that apply) a) Minimize operator exposure (chosen) b) Minimize patient exposure (chosen) c) State the laws regarding x-ray use with patients (chosen) d) Protect radiographers from lawsuits

Answer 131

a) Minimize operator exposure (chosen) b) Minimize patient exposure (chosen) without sacrificing diagnostic diagnostic information

Question 132

All of the following are financial benefits of PACS except: a) Paper supply costs b) Decreased storage space required c) Processor maintenance d) Cheaper equipment

Answer 132

d) Cheaper equipment Benefits of picture archive and communication systems (PACS) have drastically changed health care. They require less storage space and maintenance than conventional film, however, digital imaging equipment is more expensive up front.

Question 133

How likely is it that an individual will receive acute injurious effects during a routine diagnostic x-ray? a) Impossible b) very unlikely c) likely d) very likely

Answer 133

This is very unlikely. Diagnostic x-rays would not be performed if there was likely to be injury as a result.

Question 134

Magnification mode increases resolution from about: a) 1 lp/mm to 3 lp/mm b) 4 lp/mm to 6 lp/mm c) 4 lp/mm to 8 lp/mm d) 4 lp/mm to 10 lp/mm

Answer 134

b) 4 lp/mm to 6 lp/mm Standard resolution of cesium iodide image tubes is 4 lp/mm and electrons are emitted from a 9" diameter circle. In magnification mode, only electrons emitted from a smaller diameter circle (6") are focused on the output phosphor. The resulting resolution is 1.5 times greater 4 lp/mm x (9/6) = 6 lp/mm.

Question 135

Loss of image brightness at the periphery of an image is a result of: (select all that apply) a) Mottle b) Pincushion distortion (chosen) c) Lower brightness gain at the periphery (chosen) d) Periphery of the image is displayed over a larger area than the center (chosen)

Answer 135

c) Lower brightness gain at the periphery (chosen) d) Periphery of the image is displayed over a larger area than the center (chosen) A fall off in brightness at the periphery of an image is called vignetting. Vignetting occurs because the peripheral image is displayed over a larger area of the output screen and so it's brightness gain is less than in the center.

Question 136

Which of the following factors contribute to the final resolution in a fluoroscopic image? a) Video system b) Source to object distance (SOD) c) Focal spot size d) All of the above

Answer 136

d) All of the above The final resolution in a fluoroscopic image is dependent on the video system, the image intensifier, source to object distance (SOD), the x-ray tube focal spot size, and patient motion.

Question 137

Which direction from the primary (useful) beam is most scattered radiation during fluoroscopy? a) 30 degrees b) 60 degrees c) 90 degrees d) 135 degrees e) 180 degrees

Answer 137

d) 135 degrees Most scatter is reflected back towards the emitter at 135 and 120 degrees

Question 138

Advantages of digital fluoroscopy include all of the following EXCEPT: a) Less expensive than conventional b) Edge enhancement c) Gray-scale processing d) Last-image hold

Answer 138

a) Less expensive than conventional Digital fluoroscopy allows image quality enhancement through a variety of means. Last-image hold, gray-scale processing, temporal frame averaging and edge enhancement are all capabilities of digital fluoroscopy systems.

Question 139

This occurs when the diameter of the image from the optical system is smaller than the shortest dimension of the film. a) Exact framing b) Total overframing c) Overframing d) Underframing

Answer 139

d) Underframing Exact framing is when the diameter of the image at the output phosphor and the smallest dimension of the cine frame are equal. With overframing the image is larger than the film and with underframing the image is smaller than the film.

Question 140

The smallest element of a digital image is known as a: a) Matrix b) Pixel c) Decimal d) Binary

Answer 140

b) Pixel The smallest element of a digital image is a pixel. A two-dimensional array of pixels is known as a matrix. Binary is a way of encoding values using only 0 and 1, whereas decimals use 0 through 9.

Question 141

Which of the following are high bone marrow dose examinations? (select all that apply) a) Femur x-rays (chosen) b) Barium enema (chosen) c) Upper GI series (chosen) d) Abdominal angiography (chosen)

Answer 141

B/C/D The bone marrow dose is a reasonable indicator of doses to other internal organs which are sensitive to cancer. Abdominal imaging in general exposes the patient to a high bone marrow dose. Femur x-rays are far enough away from vital organs to cause insignificant bone marrow doses.

Question 142

What are the specified parameters to measure fluoroscopy exposure rates using a phantom? a) Maximum 5 rads/minute, 15 cm from the image intensifier, using a phantom 9 inches of water b) Maximum 3 rads/minute, 30 cm from the image intensifier, using a phantom 9 inches of water c) Maximum 3 rads/minute, 15 cm from the image intensifier, using a phantom 9 inches of water d) Maximum 5 rads/minute, 30 cm from the image intensifier, using a phantom 9 inches of water

Answer 142

Fluoroscopic exposure rates should not exceed 5 rads/minute (5 centigray/minute) as measured at 30 cm from the input surface of the image intensifier. For an exposure rate measurement a phantom of 9 inches of water or 7.9 inches of Lucite should be used to simulate a patient

Question 143

What is the purpose of the electron gun? a) To produce a video signal b) To produce a scanning electron beam c) To compress the electron beam d) To create a voltage

Answer 143

A vidicon camera is usually employed in fluoroscopic imaging as a way of converting an electron signal into a voltage. The most important parts of a vidicon camera are the target and the electron gun. The electron gun produces an electron beam in a vacuum and focuses it onto the photoconductive target to produce a television picture.

Question 144

In Compton scattering what two components are interacting? (select all that apply) a) An x-ray photon (chosen) b) An outer orbital electron c) An inner orbital electron (chosen) d) An atoms nucleus

Answer 144

a) An x-ray photon (chosen) b) An outer orbital electron Compton scattering is the interaction between an x-ray photon and an outer orbital electron, which produces an x-ray photon of less energy. This lesser energy x-ray photon is the scattered radiation that is seen by the operator during a fluoroscopic exam

Question 145

With optical coupling between an image intensifier, and viewing and recording systems, how much light is sent to the viewing system (vidicon)?Difficulty a) 90% b) 50% c) 10% d) 5%

Answer 145

10% With optical coupling typically 10% is sent to the viewing system and 90% is sent to the recording system.

Question 146

Digital fluoroscopy systems are commonly used to record images of: a) Legs b) Gastrointestinal tract c) Vessels d) Arms

Answer 146

Digital fluoroscopy systems are commonly used to record images of rapidly changing objects, such as contrast passing through vessels.

Question 147

What is the primary cause of shape distortion? a) Object to image distance b) Focal distance c) Minification d) Geometric factors

Answer 147

D) geometric factors Shape distortion is another name for pincushion distortion. Shape distortion results from projecting the image formed on a curved input phosphor onto a flat output phosphor (geometric factors). This results in a slightly higher magnification of the input image towards the edge of the screen

Question 148

A CINE exam using 35 mm film at 30 frames/second causes _____ skin exposure rate as compared to fluoroscopy? a) A slightly lower b) A much lower c) A greater d) The same

Answer 148

c) A greater Patient exposure in cinefluorography is significantly higher than with other types of image recording systems and can deliver approximately 10 times more dose than fluoroscopy.

Question 149

What must be done to the video signal when the electron beam produces a voltage that is sent to the television camera? a) It must be synchronized b) Nothing c) It must be narrowed d) It must be amplified

Answer 149

It must be synchronized + amplified The output phosphor of an image intensifier tube is typically coupled to a television camera, which converts the electron signal into a video signal. This signal is transmitted through a cable to the camera control unit, where it is amplified and forwarded to the television monitor. The camera control unit also focuses and synchronizes the video signal

Question 150

Decreasing exposure: a) Decreases statistical fluctuation b) Increases the available x-ray photons c) Decreases the grainy appearance d) Decreases the number of absorbed photons

Answer 150

d) Decreases the number of absorbed photons Decreasing exposure reduces the number of X-rays that pass through a patient. A decrease in x-rays will result in fewer photons generated at the input phosphor and fewer electrons emitted from the photocathode

Question 151

What is image contrast? a) Excessive heating of the X-ray tube b) The statistical fluctuation of absorbed X-ray photons c) Decreased light intensity at the edge of an image d) The ratio of brightness between two areas (typically between the peripheral and center areas) of the output screen

Answer 151

d) The ratio of brightness between two areas (typically between the peripheral and center areas) of the output screen

Question 152

This term refers to the random probability of an effect occurring: Safety Medium Difficulty a) Deterministic effect b) Stochastic effect c) Nonstochastic effect d) Damaging effect

Answer 152

b) Stochastic effect Stochastic effects refer to the probability of an effect occurring, not the severity. They are a function of radiation dose without a threshold.

Question 153

The following term(s) refer to radiation with a threshold, where the severity of effect varies with dose: a) Stochastic effects b) Non-stochastic effects c) Deterministic effects

Answer 153

b) Non-stochastic effects c) Deterministic effects Nonstochastic effects are those for which the severity varies with radiation dose and for which there may be a threshold. Deterministic is synonymous with nonstochastic

Question 154

What is the maximum tabletop dose rate when imaging with high level (boost) fluoroscopy? a) 2.2 rads (2.2 centigray) per minute b) 5 rads (5 centigray) per minute c) 20 rads (20 centigray) per minute d) 30 rads (30 centigray) per minute

Answer 154

20 rads (20 centigray) per minute High level fluoroscopy provides significantly higher x-ray tube currents, with corresponding increases in patient dose rates. The maximum allowed tabletop dose rate is 20 rads (20 centigray) per minute

Question 155

The resolution of a fluoroscopic system is mostly determined by the: a) Video monitor b) TV camera c) Output phosphor d) Input phosphor

Answer 155

a) Video monitor The resolution of an imaging system is mostly determined by the resolution of the video monitor. Monitor image quantity is also limited by quantum mottle, which is statistical fluctuations in radiation.

Question 156

If the Bucky tray is moved to the end of the examination table, leaving an opening at the gonadal level, this must be automatically covered with at least: a) 0.10 mm lead equivalent b) 0.25 mm lead equivalent c) 0.50 mm lead equivalent d) 0.75 mm lead equivalent

Answer 156

0.25 mm lead equivalent This opening must be covered by at least 0.25 mm lead equivalent

Question 157

If the collimator is opened so that double the area is exposed, patient dose will: a) Decrease by 50% b) Increase by 50% c) Double d) Quadruple e) Remain unchanged

Answer 157

Patient and operator exposure is directly proportional to the exposure area such that doubling the exposure area will double the patient and operatore exposure.

Question 158

Why is synchronization used in cinefluorography? a) To match the motion of the organ being imaged b) So that the camera shutters open at the same frequency as x-ray pulses c) To shorten the x-ray tube life d) To operate the x-ray pulses at the same time as the patient breathing

Answer 158

b) So that the camera shutters open at the same frequency as x-ray pulses It's purpose is to make sure each image lines up on the correct portion of the film.

Question 159

Which of the following milliamperages (mA) would be used during spot filming? a) 100 mA b) 1 mA c) 25 mA d) 5 mA e) 10 mA

Answer 159

a) 100 mA Spot films use high x-ray currents (>100mA) and short exposure times to generate useful images

Question 160

What unit is used to measure the input intensity of an x-ray tube? a) Ergs b) Millirads c) Rads d) Milliamperes

Answer 160

d) Milliamperes The input intensity of an x-ray tube is measured in milliamperes (mA). Fluoroscopic tubes are generally operated at 5mA or less

Question 161

Which factors are directly proportional to milliamperage (mA)? a) X-ray output b) Exposure time c) Radiation dose to patient d) Source to object distance

Answer 161

a) X-ray output c) Radiation dose to patient Milliamperage is a measure of x-ray tube current and is directly proportional to the intensity of the x-ray beam. The radiation dose to the patient is also directly proportional to the mA because a higher mA will result in a higher intensity x-ray beam and so more radiation exposure to the patient. Exposure time and source to object distance are independent of mA

Question 162

Sievert is a measure of: a) Absorbed dose b) Absorbed dose equivalent c) Exposure dose d) Energy equivalent dose e) Dose rate f) Emitted dose

Answer 162

b) Absorbed dose equivalent Commonly used radiation metrics include the absorbed dose and the dose equivalent. Absorbed dose is used to express the amount of radiation absorbed by tissue. Units of absorbed dose include Gray and Rad. Dose equivalent was devised due to the fact that the same absorbed dose in rads delivered by different kinds of radiation does not produce the same degree of biological effects. Units of dose equivalent include Sievert and Rem

Question 163

In digital fluoroscopy, this technique reduces image noise by averaging multiple image frames. a) Gray-scale processing b) Last-image hold c) Temporal frame averaging d) Edge enhancement

Answer 163

c) Temporal frame averaging Digital fluoroscopy allows image quality enhancement through a variety of means. Last-image hold, gray-scale processing, temporal frame averaging and edge enhancement are all capabilities of digital fluoroscopy systems. Temporal frame average is the only answer choice that reduces image noise by averaging multiple image frames. Last-image hold provides an image of a frame of a video for viewing. Gray-scale processing refers to adjusting image brightness and contrast. Edge enhancement is performed by subtracting a blurry version of an image from the original and adding this new image back to the original.

Question 164

According to the Law of Bergonie and Tribondeau, radiosensitivity depends on: a) The number of undifferentiated cells b) All of the above c) The degree of mitotic activity of the cells d) The life cycle of the exposed cell

Answer 164

The law of Bergonie and Tribondeau states, "The radiosensitivity of tissues depends on the number of undifferentiated cells which the tissue contains, the degree of mitotic activity in the tissue, and the length of time the cells of the tissue stay in active proliferation."

Question 165

The effective focal spot size may be smaller than the actual focal spot, this is due to: a) Beam size b) Cathode angle c) Anode angle d) Field coverage

Answer 165

c) Anode angle The effective focal spot size may not be the same as the focal spot size due to the anode angle, which is typically 7-20 degrees. The effective focal spot size is the area projected from the anode perpendicularly onto the image receptor (see figure 3 in reference).

Question 166

Which camera type has the greatest lag? a) Plumbicon camera b) Vidicon camera c) Charge-Coupled Device (CCD)

Answer 166

b) Vidicon camera Vidicon camera tubes have the greatest lag because it takes time for the image to build up and decay on the vidicon target

Question 167

Which of the following is not an example of an image processing task used in digital imaging? a) Edge enhancement b) Road mapping c) RIS d) Temporal frame averaging

Answer 167

c) RIS Edge enhancement, road mapping, and temporal frame averaging are all examples of digital image processing. Radiology information system (RIS) is the software used to manage patient data in an imaging department.

Question 168

Which factors affect the image brightness at the output phosphor (screen)? (select all that apply) a) Field of view (FOV) (chosen) b) Brightness gain c) Minification gain d) Flux gain (chosen)

Answer 168

b) Brightness gain c) Minification gain d) Flux gain The ability of the image intensifier tube to increase the illumination of the image is called the brightness gain, and is a product of the minification gain and the flux gain.

Question 169

Which type of contrast is reduced by increasing the kilovolt peak (kVp)? a) Detector contrast b) Subject contrast c) Characteristic contrast d) Brightness contrast

Answer 169

b) subject contrast Overall contrast is dependent on the subject contrast and the detector contrast. The subject contrast is reduced by increasing the kVp.

Question 170

The half-value layer (HVL) is a characteristic of an x-rays: a) Quantity b) Quality c) Resolution d) Brightness

Answer 170

b) Quality The concept of half-value layer is important in shielding, where it guides material choice to attenuate x-rays. The quality of x-rays is characterized by the half-value layer

Question 171

Which of the following is NOT a component of the detector elements (DEL) in a flat panel detector? a) Cesium Iodide b) Photodiode c) Output phosphor d) Scintillation layer

Answer 171

c) Output phosphor The detector elements (DEL) of a flat panel detector are responsible for converting x-ray energy into an electronic signal. Each DEL is composed of a scintillation layer made of Cesium Iodide (CsI), which attenuates x-rays and produces light. The light is then directed toward a photodiode below, which converts the signal into electricity that can be used to generate an electronic image. The output phosphor is a component of an image intensifier

Question 172

What is the relative increase in exposure when using magnification mode, where the center 6 inches of the input screen is now visualized over the entire 9 inch window? a) No change b) 2/3 c) 2 d) 2.25 e) 3

Answer 172

The increase in exposure is calculated by the ratio the original diameter squared to the magnification mode diameter squared. (9x9/6x6)=81/36=2.25.

Question 173

When can the exposure rate at the tabletop exceed 10 rads/min? a) When using automatic brightness control on large patients b) When the operator is in a hurry c) There are no exceptions

Answer 173

When using automatic brightness control on large patients For routine fluoroscopy the dose at the tabletop should not exceed 10 rads/min. This limit does not apply during magnification procedures or for recording of fluoroscopic images where higher exposure rates are required. Large patients may require larger doses of radiation due to the increased attenuation of the primary x-ray beam through the patient's skin and soft tissue.

Question 174

What term refers to the standardized method of evaluating the brightness of an image intensifier? a) Deterioration b) Total Brightness Gain c) Conversion factor d) Flux Gain

Answer 174

c) Conversion factor Brightness gain can deteriorate as much as 10% per year. Because of this, periodic checks of brightness can be made by measuring the conversion factor. The conversion factor is the ratio of the intensity of the output phosphor to the input exposure rate to the input phosphor (intensity divided by millirads/second).

Question 175

Loss of image brightness at the periphery of an image is a result of: (select all that apply) a) Mottle b) Pincushion distortion c) Lower brightness gain at the periphery (chosen) d) Periphery of the image is displayed over a larger area than the center (chosen)

Answer 175

c) Lower brightness gain at the periphery d) Periphery of the image is displayed over a larger area than the center A fall off in brightness at the periphery of an image is called vignetting. Vignetting occurs because the peripheral image is displayed over a larger area of the output screen and so it's brightness gain is less than in the center.

Question 176

Lower image quality at low radiation doses is a result of: a) X-ray generator b) Loss of signal in closed circuit wires c) X-ray's moving too slow through the patient d) Quantum mottle

Answer 176

Quantum mottle is the grainy appearance in an image caused by statistical fluctuation of absorbed x-ray photons. A large decrease in the number of x-ray photons would cause a great deterioration in image quality. Mottle is also more visible in high contrast, high resolution systems. Additionally, changing the sensitivity will lead to a different number of x-ray photons released by statistical fluctuation

Question 177

What is the point called where the dose-effect curve intersects the abscissa? a) The dose response b) The threshold dose c) The non-threshold dose d) The Y coordinate

Answer 177

b) The threshold dose The abscissa is the x-coordinate on an x-y graph. The point where the curve intersects the abscissa is considered the threshold. Under the non-threshold hypothesis this value is "0".

Question 178

An x-ray tube outputs 4 milliroentgens (mR) per one milliampere-second (mAs) at a distance of 40 inches. What will the radiation exposure be at 80 inches from the x-ray tube (in mR/mAs)? a) 1 b) 2 c) 8 d) 16

Answer 178

The intensity of an x-ray beam varies with the square of the distance from the x-ray source. To calculate the absorbed dose at a distance farther from the x-ray tube you multiply the original intensity (4 mR) by the ratio of the distances squared 4(40^2/80^2) = 4(1600/6400) = 4(1/4) = 1

Question 179

What unit of measurement is used for air kerma? a) Gray (Gy) b) Rem c) kVp d) mA

Answer 179

a) Gray (Gy) Kerma (kinetic energy released in matter) is the amount of energy transferred from incident x-rays to charged particles per unit mass. Air kerma is where the unit of mass is air and is measured in gray (or milligray).

Question 180

The input phosphor: a) Absorbs X-rays b) Absorbs electrons c) Converts photons into energy d) Is not fluorescent

Answer 180

a) Absorbs X-rays After x-rays pass through a patient they strike the image intensifier's input phosphor. This layer absorbs x-rays and converts their energy into light photons proportional to the intensity of the x-ray beam. The light photons impact on the photocathode, causing electrons to be given off. The accelerating anode then speeds up these electrons, where they are focused by the electrostatic lens onto the output phosphor

Question 181

The output phosphor converts photoelectrons into: a) X-rays b) Hydrogen atoms c) Heat d) Light photons

Answer 181

d) light photons The output phosphor is a fluorescent layer of material. When electrons strike the output phosphor their energy is turned into light photons, which are sent to the television camera

Question 182

Which of the following is NOT required on mobile fluoroscopic equipment? a) A way to prevent operation when the collimating cone or diaphragm is not in place b) Device to prevent operation when the X-ray beam is not entirely intercepted by the image receptor c) Automatic Brightness Control (ABC) d) An inherent system preventing operation at a source to skin distance (SSD) less than 30 cm (12 in)

Answer 182

c) Automatic Brightness Control (ABC) Automatic brightness control is not required on mobile fluoroscopic equipment

Question 183

Which of the following are advantages of three-phase generators? (select all that apply) a) Close to constant potential b) High mA for very short exposures c) Higher effective kV (chosen) d) Lower patient dose (chosen)

Answer 183

a/b/c Three-phase generators and high frequency generators are advantageous because they provide a near constant potential, a higher mA (which is useful in angiography and spot filming), and a higher effective kV. Unfortunately, there is no improvement in patient dose with the use of these generators

Question 184

What does automatic brightness control do? a) Keep the light output of the image intensifier constant b) Conserve energy by reducing x-ray production c) Maintain a constant dose rate to the patient d) Keep the camera tube target voltage constant

Answer 184

A) Keep the light output of the image intensifier constant Automatic brightness control keeps the light output of the image intensifier constant over variations of patient attenuation (different tissue density and thickness).

Question 185

The following are true during High Level (Boost) fluoroscopy: I. Increase in tube currents II. A special key and interlock is required with an additional person III. Increase in entrance dose rate to the patient IV. Audible signal must be heard a) I & III b) II & IV c) I, II, & III d) All of the above

Answer 185

d) All of the above High level (Boost) fluoroscopy refers to a special activation capability of a fluoroscopic system to provide significantly higher tube currents and therefore significantly higher dose rates to the patient. Boost fluoroscopy is typically used for interventional angiography or cardiography, where it is needed to visualize small guidewires and catheters. Key points are that a special activation with key and interlock is required, an audible signal must be heard, and the tabletop dose rate is limited to 20 rads/minute

Question 186

In digital fluoroscopy, this technique reduces image noise by averaging multiple image frames. Image Production Medium Difficulty a) Gray-scale processing b) Last-image hold c) Temporal frame averaging d) Edge enhancement

Answer 186

c) Temporal frame averaging Digital fluoroscopy allows image quality enhancement through a variety of means. Last-image hold, gray-scale processing, temporal frame averaging and edge enhancement are all capabilities of digital fluoroscopy systems. Temporal frame average is the only answer choice that reduces image noise by averaging multiple image frames. Last-image hold provides an image of a frame of a video for viewing. Gray-scale processing refers to adjusting image brightness and contrast. Edge enhancement is performed by subtracting a blurry version of an image from the original and adding this new image back to the original.

Question 187

How do you adjust the luminescence of a TV image? (select all that apply) a) Adjusting the contrast on the TV b) Cannot be adjusted c) Increasing the room lighting d) Adjusting the brightness on the TV

Answer 187

a/d Luminescence refers to the emission of light from an object. To increase the luminescence on a TV image you can change the contrast to make light structures lighter, or increase the brightness on the monitor. Adjusting the room lighting will make the image easier to see, however, this does not change anything on the TV image.

Question 188

Which of the following terms correctly describes a pixel? (select all that apply) a) The smallest element of a digital image (chosen) b) Three dimensional c) Pixels make up a square matrix (chosen) d) Characterized by location, size, and value (chosen)

Answer 188

a/c/d A pixel is the smallest element of a digital image and is two dimensional. Pixels can be characterized by their location, size, and value. The matrix size describes the number of pixels. The size of a pixel is the smallest detail visible in an image. A pixel can be assigned a value to denote gray or color level.

Question 189

Which of the following is a licentiate? a) Radiographer b) Radiologic Technologist c) Physician d) Anyone with a fluoroscopy license

Answer 189

Licentiate refers to physicians who may use and supervise the use of fluoroscopic and ancillary equipment.

Question 190

Loss of image brightness at the periphery of an image is a result of: (select all that apply) a) Mottle b) Pincushion distortion (chosen) c) Lower brightness gain at the periphery (chosen) d) Periphery of the image is displayed over a larger area than the center

Answer 190

c) Lower brightness gain at the periphery (chosen) d) Periphery of the image is displayed over a larger area than the center A fall off in brightness at the periphery of an image is called vignetting. Vignetting occurs because the peripheral image is displayed over a larger area of the output screen and so it's brightness gain is less than in the center

Question 191

Which of the following is not thought to affect patient exposure? a) High frequency generator b) Target-to-panel distance c) Exposure time d) Room lighting

Answer 191

a) High Frequency Generator

Question 192

A "radiation area" is an area in which individuals could receive a dose equivalent greater than ____ in one hour. a) 0.05 mSv b) 0.01 mSv c) 0.25 mSv d) 50 mSv

Answer 192

a) 0.05 mSv A "radiation area" is one in which there exists radiation levels that could result in an individual receiving a dose equivalent in excess of 0.05 mSv in 1 hour at 30 cm from the radiation source

Question 193

Secondary radiation (scattered or leakage) has lower energy than the primary beam a) TRUE b) FALSE

Answer 193

a) TRUE Scattered radiation is directly proportional to the radiation incident on the patient in the primary beam. Scattered radiation will always be of lower energy than the primary beam because some energy is absorbed by the patient

Question 194

What is the minification gain in an image intensifier with a 10 inch input phosphor and a 1 inch output phosphor. a) 0.1 b) 10 c) 20 d) 100

Answer 194

d) 100 Minification gain is the ratio of the input phosphor diameter squared to the output phosphor diameter squared. In this case it is (10x10)/(1x1)=100/1=100.

Question 195

If you double the diameter of the input phosphor and keep the output phosphor the same size, how much does the minification gain increase? a) 10 times b) 4 times c) 2 times d) Stays the same

Answer 195

b) 4 times Minification gain is the ratio of the input phosphor diameter squared to the output phosphor diameter squared. Doubling the input phosphor diameter will increase the minification gain by 4. As an example, going from a 5 inch to 10 inch input phosphor: (5x5)/(1x1)=25/1=25, (10x10)/(1x1)=100/1=100

Question 196

What is a virtual image? a) An image created by the intersection of light rays b) The image on film c) A television image d) An image that is only for computational purposes where the light rays do not actually intersect

Answer 196

d) An image that is only for computational purposes where the light rays do not actually intersect A virtual image is one in which the light rays do not actually intersect. Television and cine film images are real.

Question 197

What is the approximate exposure a patient would receive during 5 minutes of fluoroscopy? a) 1-3 rads b) 10-30 rads c) 40-60 rads d) over 60 rads

Answer 197

b) 10-30 rads Typical fluoroscopic exams range from 1-5 rads/minute. They typically last from 5-15 minutes.

Question 198

A radiation dose produces less damage if ____ . (select all that apply) a) It is acute b) It is given at one time c) It is spread out over a long period of time d) It is protracted over a long period of time

Answer 198

c) It is spread out over a long period of time d) It is protracted over a long period of time Animal experimentation is our chief source of information about the genetic effects of radiation. These studies have shown us that the degree of damage from radiation exposure seems to be dose-rate dependent. This means that a dose is less able to produce damage if it is broken up (spread out or protracted) over a long period of time

Question 199

This type of contrast is mainly determined by the x-ray beam energy. a) Characteristic contrast b) Subject contrast c) Brightness contrast

Answer 199

Subject contrast is dependent on the kilovolt peak (kVp) and is thus dependent on x-ray beam energy

Question 200

The type of contrast that is determined by the characteristics of equipment is: a) Detector contrast b) Characteristic contrast c) Subject contrast d) Brightness contrast

Answer 200

a) Detector contrast Overall contrast is dependent on the subject contrast and the detector contrast. The detector contrast is an inherent characteristic of the x-ray equipment

Question 201

This sends light from the image intensifier to viewing and recording systems. a) Monitor b) Vidicon camera c) Camera control unit d) Optical coupling device

Answer 201

d) Optical coupling device Optical coupling devices distribute light between the viewing and recording systems. With optical coupling typically 10% is sent to the viewing system and 90% is sent to the recording system.

Question 202

Which of the following is NOT a component of the detector elements (DEL) in a flat panel detector? a) Cesium Iodide b) Photodiode c) Output phosphor d) Scintillation layer

Answer 202

c) Output phosphor The detector elements (DEL) of a flat panel detector converts x-ray -> electronic signal. Each DEL is composed of a scintillation layer made of Cesium Iodide (CsI), which attenuates x-rays and produces light. The light is then directed toward a photodiode below, which converts the signal into electricity that can be used to generate an electronic image. The output phosphor is a component of an image intensifier.

Question 203

Which of the following is(are) used to adjust contrast resolution? (select all that apply) a) Window level b) Matrix size c) Window width d) Pixel size

Answer 203

a) Window level c) Window width Contrast resolution is effected by the number of gray levels a pixel has, also known as bit depth. The higher the bit depth the higher the contrast resolution. The contrast resolution is adjusted using the window level and window width, known as gray-scale processing.

Question 204

How can you reduce patient radiation exposure during fluoroscopy? (select all that apply) a) Moving the source further away (increasing target-to-panel distance) b) Increasing the mA c) Moving the source closer (decreasing target-to-panel distance) d) Increasing the exposure time e) Using collimation

Answer 204

a) Moving the source further away (increasing target-to-panel distance) e) Using collimation Increasing exposure time, increasing mA, and decreasing target-to-panel distance all INCREASE patient exposure.

Question 205

What is the target material of an x-ray tube usually made of? a) Tungsten b) Lead c) Aluminum d) Glass

Answer 205

a) Tungsten (TARGET = TUNGSTEN) The x-ray tube consists of two important parts, a cathode, which is the source of electrons, and an anode, which is the target that produces x-rays. The anode is made of tungsten because it it has a high melting point and a high anatomic number, which makes it more efficient at producing x-rays.

Question 206

What term refers to the standardized method of evaluating the brightness of an image intensifier? a) Deterioration b) Total Brightness Gain c) Conversion factor d) Flux Gain

Answer 206

c) Conversion factor Brightness gain can deteriorate as much as 10% per year. Because of this, periodic checks of brightness can be made by measuring the conversion factor. The conversion factor is the ratio of the intensity of the output phosphor to the input exposure rate to the input phosphor (intensity divided by millirads/second).

Question 207

This component controls the radiation exposure incident at the input phosphor in cine film imaging. a) Input Phosphor b) Output Phosphor c) Aperture d) Electrostatic lens

Answer 207

c) Aperture The aperture controls the radiation exposure at the input phosphor during cine or photospot film imaging. The size of the aperture is defined by the f-number: the larger the f-number the smaller the size of the aperture.

Question 208

The focal spot size of a fluoroscopic x-ray tube is _____ than the focal spot size of a radiographic x-ray tube. a) Often smaller b) Often larger c) No different d) Sometimes larger and sometimes smaller

Answer 208

a) Often smaller Fluoroscopic x-ray tubes are similar to traditional x-ray tubes except that fluoroscopic tubes are designed with smaller focal spots and typically operate for a longer time and at much lower mA

Question 209

The resolution of a fluoroscopic system is mostly determined by the: a) Video monitor b) TV camera c) Output phosphor d) Input phosphor

Answer 209

a) Video monitor The resolution of an imaging system is mostly determined by the resolution of the video monitor. Monitor image quantity is also limited by quantum mottle, which is statistical fluctuations in radiation

Question 210

What potential difference (kVp) is required in an image intensifier to speed up electrons by the accelerating anode? a) 1 kVp b) 10 kVp c) 25 kVp d) 50 kVp

Answer 210

c) 25 kVp Electrons are sped up by the accelerating anode in an image intensifier tube. This requires approximately 25,000 volts (25 kVp).

Question 211

Increasing the voltage in an image intensifier tube: (select all that apply) a) Compresses the electron beam b) Reduces the available input surface c) Changes the image from mag to standard mode d) Moves the crossover point to further away from the output phosphor

Answer 211

a) Compresses the electron beam b) Reduces the available input surface d) Moves the crossover point to further away from the output phosphor

Question 212

What does a photoconductive target do? a) Conducts electrons to a target b) Creates a video signal c) Allows an electron charge to be generated d) Creates an electrical current to signal a video image

Answer 212

d) Creates an electrical current to signal a video image A vidicon camera is usually employed in fluoroscopic imaging as a way of converting an electron signal into a voltage. The most important parts of a vidicon camera are the target and the electron gun. The electron gun produces an electron beam in a vacuum and focuses it onto the photoconductive target to produce a television picture.

Question 213

What is the dose equivalent limit to an embryo/fetus during the entire pregnancy for an occupational exposure of a pregnant woman? a) 0.5 mSv b) 5 mSv c) 50 mSv d) 500 mSv

Answer 213

b) 5 mSv The dose to an embryo/fetus during the entire pregnancy should not exceed 5 mSv.

Question 214

Calculate the total brightness gain for an image intensifier with the following specifications: Input phosphor diameter: 9 inches Output phosphor diameter: 1 inch Flux gain: 50 a) 9 b) 45 c) 81 d) 450 e) 4050

Answer 214

B.G = minification gain x flux gain). Minification gain =input screen diameter squared/output screen diameter squared). Brightness gain in this example is 9x9/1x1 x 50 = 81 x 50 = 4050