ARRT Registry Review covering for Image Production content area
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| What is the Moiré effect? | Also known as Aliasing artifact, it has the appearance of somewhat wavy linear lines and can occur in computed radiography when using stationary grids.
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| What is the relationship between OID and magnification? | Inversely related. OID +, magnification -
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| How is the anode heel effect more prominent? | Using short SIDs, large IRs, small anode angles, and imaging parts having uneven tissue densities.
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| What is the function of the back up timer? | Protect the patient from overexposure and the x-ray tube from excessive heat load.
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| Technical factor that regulates receptor exposure: | mAs
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| How can SID compensate OID? | An increase of 7 inch SID compensates for every inch of OID
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| How are lp/mm and LSP measure? | Line pairs per millimeter (lp/mm) measure using a resolution test pattern. Line-spread function (LSP) measure using 10mm x-ray beam
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| MTF | Modulation transfer function: measures the amount of information lost between the object and the IR
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| Loss of signal at the lateral edges can mean : | SID is above or below the recommend focusing distance, the useful beam will not coincide with the angled lead strips at the lateral edges. Grid cutoff.
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| kVp adjustments for increase in patient thickness | for each centimeter of increase in thickness, 2 kV is added to the exposure
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| Additive pathologies | Ascites
Rheumatoid arthritis
Paget's disease
Pneumonia
Atelectasis
Congestive heart failure
Edematous tissue
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| Destructive Pathologies | Osteoporosis
Osteomalacia
Pneumoperitoneum
Emphysema
Degenerative arthritis
Atrophic and necrotic conditions
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| PSP Layers | Protective layer
Phosphor layer
Electroconductive/conductor
Support layer
Light shield/Reflective layer
Protective (Backing) layer
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| Bit depth | the number of bits required to describe the gray level that each pixel can take on
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| As matrix size increases (fixed FOV) | pixel size is smaller and better image resolution results
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| As FOV increases (fixed matrix size) | the size of each pixel increases and spatial resolution decreases
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| What produces the most receptor exposure? | The combination of highest milliampere seconds value and shortest SID
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| How is image resolution improved? | Small DEL size and large fill factor
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| Window level | associated with image brightness changes
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| Window width | changes in image contrast
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| Reproducibility | consistency in exposure output during repeated exposures at a particular setting
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| Linearity | Quality assurance term use to describe consistency in exposure at adjacent mA station
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| When increasing SID | The effect of excessive OID decreases. However, increased SID usually requires a significant increase in exposure factors.
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| Types of grids | Parallel/non-focused grids
Angled/focused grids
Moving grids
Stationary grids
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| Types of grid error (grid cutoff) | Upside-down focused grid
Off-focus grid
Off level/angulation error
Off center/lateral decentering
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| Parallel/Non-focused grid | Lead strips in the grid are parallel
Used in fluoro and mobile radiography
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| Angled/focused grid | lead strips in the grid are angled to match the divergence of the x-ray beam
allows more photons to pass through
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| Moving grids | Vibrate during the exposure to blur the grid lines.
Requires a connection to the imaging equipment and source of electricity.
Used only in table or wall mounted Bucky's.
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| Stationary grids | Used in tabletop or mobile radiography where there is no connection of the IR to the system.
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| Upside-down focused grid error | Occurs with focused grids only.
Grid lines are opposite of the beam's divergence.
Results in a loss of exposure along edges of image.
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| Off-focus/focus-grid distance decentering error grid | Occurs when using an SID that is outside the manufacturers range for a focused grid.
Loss of exposure on the outside or one side of the image.
Also called focus-grid decentering.
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| Off level/Angulation error | Result of the beam being angled against the gridlines.
Caused by the tube or the IR not being aligned to each other.
Occurs with focused or non-focused grids.
Results in loss of exposure across entire image.
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| Off center/Lateral decentering grid error | Beam is not aligned to the center of the focused grid.
Beam divergence doesn't match the angle of the lead strips.
Results in overall loss of exposure.
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| Preprocessing (Acquisition processing) functions | flat-field corrections, correction for noise reduction as a result of DEL dropout, rescaling, exposure field recognition, segmentation recognition, and histogram analysis
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| Equalization (dynamic range control) | DRC - postprocessing function
compresses the contrast scale, remove densities that obscure image details
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| HVL | the amount of material necessary to decrease the intensity of the beam to one-half its original value, thereby effecting a change in both beam quality and quantity.
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| Absorption | when an x-ray photon interacts with matter and disappears (photelectric effect)
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| Scattering | when there is partial transfer of energy to matter (Compton effect)
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| Attenuation | the reduction in the intensity of an x-ray beam as it passes through matter (in the form of absorption and scattering)
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| Scatter absorption is improved by having | High grid ratio, low grid frequency (the number of lead strips per inch)
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| How do we produce short scale image contrast? | The lower the kilovoltage, the less penetration, and shorter the scale contrast.
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| X-ray beam off-center and off-off focus below the focusing distance | the image below the focus will show increased receptor exposure
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| X-ray beam off-center and off-focus above the focusing distance | the image below will show decreased receptor exposure
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| Reciprocity Law | A particular milliampere seconds value, regardless of the combination of milliamperes and time, will reproduce the same receptor exposure.
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| Nyquist theorem | the sampling frequency must be greater than twice the frequency of the input signal so that the reconstruction of the original image can be close to the original signal
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| Maximal spatial resolution in digital imaging | is equal to the Nyquist frequency, 1/2 x pixel pitch (mm)
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| Histogram | graphic representation of pixel value distribution
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| Factors that affect histogram | Positioning, centering, collimation, selection of the correct processing algorithm, changes in scatter, SID, OID
(anything that affects scatter or dose)
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| Exposure latitude | The range of exposure diagnostic image values the image detector is able to produce.
Dependent on image detector = +dynamic range of detector, +values are detected
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| LUT | look-up table
used as a reference to evaluate the raw information and correct the luminance values.
a characteristic curve that best matches the anatomic part being imaged.
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| Attenuation: the higher the kilovoltage | the less is the attenuation
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| Attenuation: the greater the effective atomic number of the tissues | the greater the beam attenuation
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| Attenuation: the greater the volume tissue (subject density and thickness) | the greater beam attenuation
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| Primary or Low-Voltage Circuit Devices | AC supply (main power supply)
main power switch
Circuit braker
Autotransformer
fuses
line voltage compensator
line voltage meter
kV selector
exposure switch
exposure timer
primary side of step-up transformer (V)
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| Secondary Circuit | Secondary side step-up transformer (kV)-secondary coil of high voltage transformer
mA meter
rectifiers
x-ray tube
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| Filament Circuit | Rheostat/mA selector
step down transformer
cathode filament
focal spot selector
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| Primary Circuit is | Low Voltage (V)
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| Secondary Circuit is | High Voltage (kV)
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| Filament circuit is | High Amperage (mA)
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| References | Saia, D.A. (2022). Image Production. In S. Barnes, C. M. Thomas (Eds.), Lange Q & A: Radiography Examination (12th ed., pp. 189-211,). Chicago, IL: McGraw-Hill Education.
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| References | Schmuck, H. (2023). RADT465 Unit 2 Image Production Worksheet (Unpublished course reference). University of Southern Indiana, Evansville, IN.
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