MOCK IMAGE PRODUCTION REVIEW

To calculate heat units the following formula must be used Heat Unit (HU) = kVp x mAs x factor What is the factor for a single-phase generator?

1

how much ripple does a high frequency generator have?

1 %

An increase in kVp with appropriate compensation of mAs will result in: 1. decrease in contrast 2. increase in exposure latitude 3. increase in density/IR exposure

1 and 2 only

Which of the following condition (s) require a decrease in technical factors? 1. atrophy 2. osteoporosis 3. atelectasis

1 and 2 only

If the grid ratio is increased with no other changes being made, the radiograph will demonstrate an increased amount of: 1. contrast (shorter scale) 2. distortion 3. density

1 only

Leakage radiation should not exceed

100mR/hr at 1 meter

What is the function of an image intensifer?

Converts x-ray beam into bright, visible light

True or False: Photoemission absorb light photons and emit heat

False: Absorbs light photons and emit electrons

True or False: The use of AEC eliminates the need to position accurately

False: Accurate and effective patient positioning and photo timer cell selection is critical. AEC provide diagnostic-quality exposures only for structures positioned directly above the ionization chambers

True or False: Magnification decreases spatial and contrast resolution

False: Better spatial and contrast resolution

In a transformer, there are 2 coils placed near one another. One coil supplied is induced. Which coil is this?

Secondary

What coats the output screen?

Silver-activated zinc cadmium sulfide phosphor

What are the two distortion types

Size & Shape

What kind of rings to alternating current generators use?

Slip rings

True of False: Focal spot size affects recorded detail

True

True or False: DR and CR are very sensitive to scatter

True

True or False: Magnification results in increased patient dose

True

True or False: The greater the mass or speed of the incident electron the greater the quality

True

True or False: The upper shutters of a collimator reduces off-focus (aka stem) radiation

True

True or False: Variable kVp systems enhance visibility of detail & increase perception of resolution

True

True or False: as SID increases, size distortion decreases

True

True or False: x-ray quantity is proportional to mAs

True

True or false: The greater the mass or speed of an incident electron, the greater the intensity or quantity

True

True or False: Contrast decreases proportionally as kVp increases

True (increased kVp = increased scatter and decreases the attenuating ability of tissue)

During fluoroscopy, the electrostatic lenses are used to accelerate and focus:

electrons

What causes shape distortion

elongation and foreshortening (caused by inaccurate CR alignment of the tube, anatomy, or IR)

mA settings determine the amount of current sent to the

filament (typically 4-6 amps)

Amorphous silicon and amorphous selenium are materials used in:

flat panel detectors

A shallow depression in the cathode assembly designed to house the filament is called the

focusing cup

mA selection determines the number of

free electrons

Electrons strike the output screen which is then converted into _______________ that exits the tube

green light photons

The maximum heat capacity of the anode of the tube is rated in terms of:

heat units

What kind of contrast does an image have when there are a very few shades of gray?

high contrast

X-rays have a _________ frequency and ___________ wavelength

high; short

A narrow (decreased) window width displays:

higher radiographic contrast (short gray scale)

This is generated by dividing a scanned area into pixels and determining the signal intensity for each pixel.

histogram

Where is the stator of the anode induction motor located?

outside the glass envelope

High voltage kVp is sent to the filament from the ___________________

step-up transformer

The line focus principle expresses the relationship between:

the actual and the effective focal spot

Back-up times cannot exceed the tube limit and should be set at __________ of the anticipated manual exposure time

150%

How many light photons can be produces from a single incident photon?

1500

Minimum response time should be

0.001 sec

An exposure was made using 400 mA and 12 msec. If the mA is changed to 100, what exposure times would MOST closely approximate the original radiographic density/IR exposure?

0.05 (mA x sec), convert milliseconds to seconds and multiply 400 mA x 0.012sec = 4.8 mAs 100mA x 0.05sec = 5.0 mAs

What is the mA range used during fluoroscopy?

0.5 to 5

QC: The central ray alignment/centering mark should be within

1%

If the SID is 72 inches and the SOD is 62 inches, what is the magnification factor?

1.16 (divide SID by SOD 72/62 = 1.16)

What is the magnification for an image viewed with an image intensification tube with an input screen diameter of 9" that is using a 5" diameter during magnification?

1.8 (9/5)

QC: kVp should be within

10%

How much ripple does a single full rectification have

100%

How much ripple does three phase generator (6 pulse)

13-25%

How many filaments are found in the x-ray tube?

2

The transformer found in the filament circuit is designed to send voltage in the range of volts to the filament of the x-ray tube.

8-12

What is the peak voltage value for high frequency?

96 to 97%

What is the power rating for a 3 phase generator capable of delivering 120 kVp at 800 mA to the tube?

96,000 W or 96 kW (V x A = W) (120 kV x 800 mA = W120,000 V x .8 A = 96,000 W)

A line voltage compensator is designed to maintain ____________________________________ within the _______________

A constant volt/turn ratio within the autotransformer

Simplest type of transformer. Primary coil is supplied with AC. Secondary coil develops AC by mutual induction is

Air core

What are the two types of target interactions?

Bremsstrahlung and characteristic

True of False: When comparing high-frequency generators to 1-phase and 3-phase generators, high frequency generators produce x-rays more efficiently

False: 1-phase & 3-phase generators produce x-rays more efficiently

Half of the incoming alternating current is being converted to pulsating direct current, opposing half not utilized, this is called

Half-wave rectification

How do you decrease magnification?

Have short OID and long SID

Which flat panel detectors uses amorphous silicon

Indirect

Which type of flat panel detector uses cesium iodide or gadolinium oxysulfide?

Indirect

What are the components of an image intensifier

Input Screen Photocathode Electrostatic Lenses Anode Output screen

What is the formula for a parallel circuit current?

It = I1 + I2 + I3

What causes an increase of magnification

Long OID and short SID

The length of time necessary for the AEC to respond to the ionization and send a signal to terminate the exposure

Minimum Response Time (MRT)

The distance from the midpoint of one pixel to the midpoint of the adjacent pixel determines the spatial resolution of the image

Pixel pitch

The _____________ ____________ determines resolution

Pixel size (smaller pixels = better resolution)

Algorithms determine the histogram of an image while the raw image is processing in the computer

Pre-Processing

In a transformer, there are 2 coils placed near one another. One coil is supplied with current. Which coil is this?

Primary

What is the formula for series circuit resistance

Rt = R1 + R2 + R3

The focusing cup assures that the x-ray tube operates at a "________________________ " (maximum current level at a given tube current).

Saturation current

The charged-couple device require what type of material to produce light?

Scintillator

indirect DR detectors that use TFT's and CCD's employ the use of ________________ to change x-ray photons to light

Scintillator

Draw a rectification wave

Sine wave

The ability to distinguish between adjacent objects on the radiographic image is known as

Spatial resolution

The image intensifier's input phosphor is generally composed of:

cesium iodide

A measure of the sensitivity and accuracy by which the image receptor converts the incoming data to the output viewing device is______.

detective quantum efficiency (DQE)

Which part on a fluoroscopic device contains a photocathode and input phosphor within a vacuum glass envelope?

image intensifier

Magnification factor formula

input screen diameter/diameter of input screen used during magnification

Where is the rotor located?

inside the envelope

An atom with a differing numbers of protons & neutrons is called an

isotope

A wider (increased) window width displays:

lower radiographic contrast (long gray scale)

What causes size distortion?

magnification; affected by OID & SID

Brightness gain formula

minification gain x flux gain

Minification gain formula

minigication on gain = diameter of input phosphor squared / diameter of output phosphor squared

A wide histogram allows for ____________ contrast while a narrow histogram allows for ___________ contrast

more; less

flux gain formula

number of output light photons/number of input x-ray photons

What device collects electric charges as a matrix in individual pixel-sized squares called detector elements?

thin film transistors (TFT)

What is the purpose of the focusing cup

to narrow the thermionic cloud as it is driven toward the anode

A step-down transformer decreases

voltage

A step-up transformer increases

voltage

How much ripple does a 3 phase 12 pulse generator have

4 to 10 %

QC: Exposure linearity should be within

+/-10%

QC Exposure reproducibility should not vary more than

+/-5%

Tungsten alloy is the usual choice for the anode target material of radiographic equipment because it: 1. has a high atomic number 2. has a high melting point 3. can readily dissipate heat

1, 2, and 3

Step-up transformers consist of which of the following? 1. Primary coils 2. Secondary coils 3. Alternating current 4. Falling load generator

1,2,3

How does the CR plate reader work?

1. A finely focused red laser beam (a helium-neon laser light) scans the plate, freeing the trapped electrons 2. The electrons into a state of photostimulated luminescence 3. Release blue-purple light in proportion to the absorbed radiation 4. Light is collected by the optical system and directs it to the photodetectors (commonly a photomultiplier tube or linear CCD array) 5. Photodetectors convert the visible light into an electronic signal and then to a digital signal 6. The electrical signal is digitized and the image is stored as a digital matrix with each pixel having a gray scale value determined by the amount of light emitted

What are the layers of a CR imaging plate? There are 5

1. Protective layer 2. Phosphor (active layer) 3. Support Layer(base) 4. Conductor Layer 5. Light-shielding layer

What is the function of the back-up timer?

1. Protects patient from excessive radiation exposure due to AEC malfunctions 2. Determines the maximum length of exposure time

How is an image produces on a fluoroscopic unit? (this is a long answer)

1. X-rays hit the input screen 2. The CsI phosphors absorb the x-ray photons and emit light 3. tbd

Fill in the blanks to obtain an image using CR 1. Begins with x-rays exposing the _____________ 2. This causes __________ of the imaging plate 3. Energy is stored in the plate, the stored energy is used to create the _________ 4. Some electrons are trapped in the____________________ structure which is stored as a latent image

1. imaging plate 2.flourescence 3. image 4. crystal phosphor

To calculate heat units the following formula must be used Heat Unit (HU) = kVp x mAs x factor What is the factor for a 3-phase generator?

1.35

To calculate heat units the following formula must be used Heat Unit (HU) = kVp x mAs x factor What is the factor for a high phase generator

1.4

What is the power rating for a single phase generator capable of delivering 80 kVp at 250 mA to the tube?

14,000 W or 14kW (V x A x 0.7) = W (80 kV x 250 mA x .07 = W80,000 V x .25 A x 0.7 = 14,000 W)

In an image intensification system, the size of the input phosphor is made smaller in order to accomplish which of the following? 1. decrease patient dose 2. magnify the image 3. increase the resolution

2 and 3 only

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

2 and 3 only

How many pulses per hertz (or per seconds) do single phase generators produce?

2 pulse/Hz (120 pulses/sec)

In general, a decrease of 15% in kilovoltage will necessitate how much of an increase in mAs to maintain density/IR exposure?

2 times (double mAs)

QC: Collimator light field should be within

2% of SID

Tube centering indicators must be accurate within:

2% of the SID

Making an exposure. Fill in the blanks 1. The radiographer presses the the rotor switch and exposure switch at the same time 2. The motor spins the anode and the ___________ gets hotter 3. The filament heats considerably, and boils off _____________ and creates an electron cloud (aka __________________) around the filament 4. At the same time, the alternating current and voltage activates the ___________ and are sent off to the primary coils of the ______________ where the voltages are boosted to kilovolts 5. After leaving the secondary coils of the step-up transformer, the voltage and alternating current are sent through the _______________ which changes the alternating current to a direct current 6. The kilovoltage greats a difference in charges in the x-ray circuit. Now the _____________ is less negative (relatively positive) and the cathode is highly _________________ 7. The difference in charges causes the ________________ to move from the cathode to the ___________________ 8. The collision of these electrons produces ________________________

2. filament 3. electrons; thermionic cloud 4. autotransformer; step-up transformer 5. rectifier 6. anode; negative 7. electrons; anode 8. heat and x-rays

If you imaged an abdomen using 80 kVp, 40 mAs on a single-phase, 2 pulse generator, what new mAs would you use on a triple-phase, high frequency generator?

20

What is the total brightness gain for an image intensification tube with a minification gain of 38 and a flux gain of 60?

2280 (38 x 60)

Exposure factors of 80 kVp and 8 mAs are used for a particular non-grid exposure. What would the new mAs be in an 8:1 grid is added with a grid conversion factor of 3?

24 mAs

Which of the following groups of exposure factors will produce the highest/shortest scale of radiographic contrast. A. 100 mA, 1/20 second, 84 kVp B. 400 mA, 1/80 second, 74 kVp C. 300 mA, 1/60 second, 95 kVp D. 200 mA, 1/40 second, 84 kVp

400 mA, 1/80 second, 74 kVp

QC: the effective focal spot size should be within

50%

The image intensifier is capable of increasing image brightness _______________ times

500-8000 times

What percentage of the incident beam is absorbed by the CsI phosphors in the input screen

66%

What will be the total resistance within a series circuit made up of the following: (2) 1.75 Ohms resistors, (3) 0.35 Ohms resistors and (1) 3.0 Ohm resistor?

7.55 Ohms

What is the peak voltage value for three-phase six-pulse power?

75 to 87%

What is an aperture diaphragm?

A simple beam limitation device; a flat piece of lead with a designated hole cut in the center.

Which of these transformer types is the simplest, with 2 coils of wire in proximity and has the least magnetic field strength? A. Air core B. Open-core C. Closed core D. Shell-type

A. Air core

Which of the following is used to regulate the duration of the x-ray exposure? A. Timer B. Prereading voltmeter C. Variable transformer

A. Timer

Which of the following is an indication that the tungsten filament is vaporizing causing tungsten to deposit on the inner surface of the window? A. decreased intensity of the beam leading to tube failure B. increased intensity of the beam leading to overheating C. a cracking of the glass envelope D. a rattling sound during the exposure

A. decreased intensity of the beam leading to tube failure

The size of the focal spot will affect which of the following? A. recorded detail B. density/IR exposure C. contrast D. magnification

A. recorded detail

Which of the following have an inverse relationship? A. recorded detail and magnification B. OID and magnification C. mA and density/IR exposure D. kVp and density/IR exposure

A. recorded detail and magnification

In the line focus principle, the ________________focal spot is the larger in size focal spot measured on the surface of the anode.

Actual

The _______________ works on the principle of self-induction. It is used to vary the incoming line voltage to an appropriate level for the high voltage step-up transformer. Located within the primary or low voltage circuit. Also known as a variable transformer.

Autotransformer

Which of these transformer types have a primary and secondary filled with an iron core? A. Air core B. Open-core C. Closed core D. Shell-type

B. Open-Core

Each of the following factors, when increased, will decrease density/IR exposure EXCEPT: A. distance B. filtration C. kVp D. beam restriction

B. filtration

Window level relates to _________________ of an image

Brightness

How are latent images removed from a CR plate?

By exposing them to light

Which of these transformer types have windings wrapped around a square core? A. Air core B. Open-core C. Closed core D. Shell-type

C. Closed Core

Which of the following will NOT affect radiographic density/IR exposure? A. filtration B. kilovoltage C. focal spot size D. milliamperage

C. focal spot size

Which of the following statements about signal-to-noise (S/N) ratio is FALSE? A. a high S/N indicates little noise in the image B. noise is either electronic system noise or quantum mottle noise C. increased noise increases contrast

C. increased noise increases contrast

Which IR uses a photostimulable store phosphor (PSP)

CR

What produces the thermionic cloud?

Changes in the filament current termed milliamperes (mA) produce changes in the filament temperature which causes a change in the number of projectile electrons boiled off the filament (thermionic emission)

What kind of rings to direct current generators use?

Commutator rings

What is the function of a transformer?

Convert incoming low voltage into high voltage

Identify the basic principle of operation of the "Autotransformer" found within the x-ray circuit. A Direct square principle B Electromagnetic mutual induction C Ohm's law principle D Electromagnetic self induction

D

Which of the following formulas is used with a parallel electrical circuit? • A V1 + V2 + V3 = Vt B R1 + R2 + R3 = Rt C 1/R1 + 1/R2 + 1/R3 = 1/Rt D I1 = I2 = I3 = It

D

Which of the following is located on the secondary side of the step up transformer of a typical radiographic unit? A kVp meter B mA selector C Autotransformer D Rectifier

D

Which of these transformer types is most commonly used? It has 2 closed cores and has the most magnetic field strength. A. Air core B. Open-core C. Closed core D. Shell-type

D. Shell-type

To permit longer AEC time, mA should be

Decreased

line focus principle

Describes the relationship between the actual and effective focal spots in the x-ray tube. A smaller target angle produces a smaller effective focal spot.

What is the function of the line voltage compensator?

Designed to maintain a constant volt/turns ratio within the autotransformer in the presence of incoming line voltage changes

Compares entrance dose to the detector to a reference industry-standard target dose

Deviation Index (DI)

Rectification use semiconductors called

Diodes

Which type of flat panel detectors uses amorphous selenium?

Direct

What kind of current dose the x-ray tube require in order to operate properly?

Direct current

How is voltage and the turns ratio related?

Directly related. The greater the turns ratio the higher the resulting voltage (or kilvoltage)

In the line focus principle, the ________________________focal spot is the smaller in size focal spot directed toward the image receptor.

Effective

True or False: The bottom shutters of a collimator reduces off-focus (aka stem) radiation

FALSE: Bottom shutters reduce penumbra along the periphery

True or false: Filtration removes low energy beams and helps increase the quality & penetrability of the beam

False: Filtration increases the quality of the beam but NOT the penetrability

True or False: Image contrast will increase as filtration increases

False: Image contrast decreases with increased filtration

True or False: increased mAs increases x-ray quality and penetrability

False: Increasing kVp increases the quality & penetrability (also increases the speed and energy of electrons)

True or False: In DR, the larger the pixel size, the greater the exposure factors used

False: Pixel size has no effect on exposure factors

True or False: Variable kVp systems produce lower contrast images than other systems

False: Produce higher contrast images than other systems

True or False: The anode is a negative electrode

False: The anode is a positive electrode

True or False: the filament is negatively charged and the focusing cup is positively charged

False: both the filament and focusing cup are negative

True or False: There are 2 types of flat panel detectors, but only 1 uses thin film transistors

False: both use TFT's (the two types are Indirect and Direct acquisition

True/False: The focusing cup is positively charged

False: it's negatively charged

True or False: The input screen on an II is convex to help with input screen distortion

False: the input screen is concave

The overall size of the image matrix selected for the examination depending on the dimensions of the anatomy to be imaged is known as:

Field of view (FOV)

What are the 2 types of image receptors used with DR?

Flat panel detectors and Charged couple devices

Converts the opposing half of the incoming alternating current to pulsating direct current (4 rectifiers), this is called

Full-wave rectification

Rectification that has 6 or 12 diodes

Full-wave rectification (3 phase generator)

Rectification that has four diodes

Full-wave rectification (single phase generator)

What is the grid conversion formula?

GCF = mAs with grid / mAs without grid

How do you calculate grid ratios?

GR = h/D (h = lead strip height D = interspaces width)

What is the formula for a series circuit current?

It = I1 = I2 = I3

Where would the autotransformer be located in the main x-ray circuit?

On the primary or low voltage circuit

Where is the line voltage compensator located?

On the primary side of the autotransformer

What component of the II accelerates and focuses the electron stream?

The electrostatic lenses

What is electromagnetic induction?

The generation of an EMF by moving a conductor through a magnetic field

The greater of pixels per mm =

The greater the resolution

Grayscale bit depth

The number of shades of gray; ranges from 8 bits to 32 bits

Useful beam or primary beam are x-ray that exit the

The tube

The number of turns of the wire in the primary coil compared with the number of turns of the wire in the secondary coil the called

The turns ratio

What two things determine digital spatial resolution?

Thickness of phosphorous layer and the number of pixels

What is the transformer law?

V - potential difference in volts N - number of turns of wire in the coil P - Primary coil S - Secondary coil

Ohm's law equation

V=IR

What is the function of a variable transformer?

Varies the incoming-line voltage to an appropriate level for the high-voltage step-up transformer

If a transformer is supplied with 200 volts to the primary coil, has 100 turns of wire on the primary coil and 10,000 turns of wire on the secondary coil, what will the voltage be in the secondary coil?

Vs = 20000 V (20 kilovolts)

What is the formula for series circuit voltage

Vt= V1 + V2 + V3

Do single phase generators use full-wave rectification?

Yes

When using an AEC, if the primary beam is collimated from an activated chamber, the result would be:

a dark image

Grossly overexposed digital images will demonstrate:

a loss of image contrast

The adoption of a DICOM standard in the medical imaging industry was designed to:

allow various vendors to share digital data without proprietary software constraints

Transformers operate on the principle of electromagnetic induction and require (alternating current or direct current)

alternating current

Indirect DR uses ____________ as the detector material.

amorphous silicon

The stator portion of the induction motor is located on the _____ side of the tube _____ the glass envelope

anode/outside of

The purpose of a LUT is to:

apply a predetermined scale of contrast to the digital data set

Positive Beam Limitation (PBL)

automatically collimates to IR size

What is a cone/cylinder beam-restricting device

circular aperture diaphragms with metal extensions

To change from a short-scale contrast to a long-scale contrast one must do two things:

decrease mAs and increase kVp

If a radiograph exposed using an AEC is overexposed because an exposure shorter than the minimum response time was required, the radiographer generally should:

decrease the mA

window width determines

image contrast (gray-scale presentation)

There are 3 materials used for the photocathode, these are:

photoemissive metals, cesium, and antimony compounds

The individual matrix box (aka individual element) is the

pixel

Alternating currents are changed to pulsating direct current through a process called

rectification

The process by which alternating current is converted into pulsating direct current is termed:

rectification

If an exposure of an image is outside of the range when compared to a reference histogram and the computer corrects the image to the correct histogram, this is known as:

rescaling

What is the input screen of an II made of?

sodium cesium iodide phosphors (CsI)