Radiography 2 Flashcards
To make a visible change in density, one must increase or decrease mAs by ____%.
30%
Is mAs directly or indecently proportional to patient dose?
Directly
KVp is the main controlling factor of _______.
Contrast
KVp also affects density mainly because it also controls ______.
Scatter
Inverse Square Law:
If you double the distance, you cover ____ the area with ____ the intensity
4x
1/4
15% Rule involves _____.
KVp
30% Rule involves ____.
mAs
15% Rule
Below 90 kVp:
+10 kV =
-10kV =
Cut mAs in 1/2
Double mAs
15% Rule
Above 90 kVp:
+15 kV =
-15 kV =
Cut mAs in 1/2
Double mAs
Inverse Square Law:
If you cut distance in 1/2, you cover ____ the area with _____ the intensity.
1/4
4x
Increased OID = _______ density
Due to Air Gap & scatter bypassing IR
Decreased
Increased speed screen = ________ mAs, pt dose, and detail
Decreased
Decreased speed screen = ______ mAs, pt dose, and detail
Increased
Increased collimation (smaller field size) = ______ density
Decreased
Decreased collimation (larger field size) = ______ density
Increased
ARRT calls density __________ or “RE”
Receptor Exposure
As part density increases, IR density _________.
Decreases
As part density decreases, IR density (RE) ________.
Increases
Degrees of differences in density
Contrast
High KV: \_\_\_\_\_\_ scale \_\_\_\_\_\_ contrast \_\_\_\_\_\_ colors \_\_\_\_\_\_ latitude \_\_\_\_\_\_ pt dose \_\_\_\_\_\_ scatter \_\_\_\_\_\_ penetration
Long Low Many Wide Decreased Increased More
Low KV: \_\_\_\_\_\_ scale \_\_\_\_\_\_ contrast \_\_\_\_\_\_ colors \_\_\_\_\_\_ latitude \_\_\_\_\_\_ pt dose \_\_\_\_\_\_ scatter \_\_\_\_\_\_ penetration
Short High Few Narrow Increased Decreased Less
TBMFG
Teeth Bone Muscle Fat Gas
Increased grid ratio = _______ contrast (less scatter)
Increased
Decreased grid ratio = _______ contrast (more scatter)
Decreased
Increased collimation = ________ contrast
Increased
Decreased collimation = ________ contrast
Decreased
Additive Pathology requires a/an _______ in technique
Increase
Destructive Pathology requires a/an _______ in technique
Decrease
3 geometric factors that control recorded detail:
Focal Spot (small) OID (short) SID (long)
Additive Pathology ex: (2)
Pneumonia
CHF
Destructive Pathology ex: (3)
Emphysema
COPD
Osteoporosis
As focal spot size increases, unsharpness (penumbra) _________ and recorded detail (umbra) _______.
Increases
Decreases
As focal spot size decreases, unsharpness (penumbra) _________ and recorded detail (umbra) _______.
Decreases
Increases
Penumbra
Unsharpness
Umbra
Recorded Detail
As SID increases, unsharpness (penumbra) ______ and recorded detail (umbra) _______.
Decreases
Increases
As SID decreases, unsharpness ______ and recorded detail ________.
Increases
Decreases
As OID decreases, unsharpness ______ and recorded detail ________.
Decreases
Increases
As OID increases, unsharpness ______ and recorded detail ________.
Increases
Decreases
Greatest enemy of detail is _______.
Motion
3 ways to overcome motion
Short exposure time
Clear concise instructions
Immobilization
Size distortion
Magnification
To overcome dose distortion (magnification)
Use short OID and long SID
Shape distortion
True distortion
Shape distortion is caused by
Mal-alignment of tube, part, and/or IR
2 types of shape (true) distortion
Elongation
Foreshortening
Increased collimation =
______ scatter, density and patient dose
______ contrast
Decreased
Increased
Decreased collimation =
______ scatter, density and patient dose
______ contrast
Increased
Decreased
Piece of lead that is not a type of variable collimator
Aperture Diaphragm
Form a round pattern on the IR
Cones and cylinders
A VARIABLE collimator
Box-type collimator
Automatic Collimator aka
Positive Beam Limitation (PBL)
Automatic Collimator / PBL can only be used in the _______
Bucky
Organic grid interspacers
Cardboard
Balsa wood
Inorganic grid interspacer
Aluminum
Focused grid (does / does not) have a required focusing distance
Does
Peripheral Grid Cut-off
Acceptable density in the middle, too light on the edges
If you use SID or if you use it upside down, you will get:
Peripheral grid cut off
Grid that does not have a required focusing distance
Parallel / non-focused
You cannot angle with a ________ grid
Crossed / Cross Hatch
With regular grids you never angle _____________ - only caudal or cephalic
Across grid lines
Cross hatch is most _________.
Restrictive
______ and ______ are stationary, whereas Bucky grids are moving
Portable
Tabletop
The higher the grid ratio, the more _____ it is to use
Restrictive
If a part measures ______ or more, use a grid
10 cm
Grid Ratio
Height of BP strips / distance between pb strips
Amount of blackness on image after processing
Density
Types of grid cut off errors: (3)
Off level
Off center
Off focus
Air-gap technique uses _______ OID to allow scatter to by-pass the IR and act as a grid
Increased
Most common ex of air gap technique is _____________.
Later C-Spine
6” air gap = _____ grid
6:1
________ Radiography uses an Imaging Plate (IP).
Computed
_______ has a phosphor layer made of Barium Fluorohalide Crystals doped with Eurpoium, called a Photostimulable Phosphor (PSP) where the latent image is formed
CR
Exposed IP then put in reader where a __________ scans over PSP to release stored energy as ________.
Neon laser
Visible light
A ___________ tube (PMT) collects light and converts it into an electronic signal and sends it to an __________ Converter (ADC) for viewing.
Photomultiplier
Analog-to-Digital
An _____________ passes over PSP to remove any remaining energy
Intense white light
__________ Radiography uses Flat Panel Detectors that have a Thin-Film Transitor (TFT)
Direct Digital (DR)
Flat Panel Detectors have a TFT layer divided into ____________.
Detector Elements (DELs)
_______ DR involves a 2 step process of converting X-ray first into visible light then into electric charges during image acquisition
Indirect
_______ DR is typically made of Cesium Iodine or Amorphous Silicon (a-Si)
Indirect
______ DR uses Amorphous Selenium (a-Se) to convert exit radiation directly into electrical charges
Direct
CR and DR have a much _____ dynamic range than analog (film-screen) imaging
Wider
Increasing the Signal To Noise Ratio (SNR) _____ visibility of an atomic details
Increases
Film has emulsion on both sides
Duplitized
Duplitized films are used in ______ cassettes.
Regular
_______ cassettes use single emulsion films.
Extremity
Matching screen color to film sensitivity
Spectral matching
Intensifying screen converts X-rays into _____.
Light
Calcium Tungstate gives off _____ light
Blue
Rare Earth gives off _____ light
Green
Emission of light from screen when stimulated by radiation
Luminescence
Giving off light only while being exposed
Fluorescence
Phosphorescence
Screen lag / glowing too long
Factors affecting screen speed: (6)
Phosphor size Thickness of active layer Type of phosphor Reflective layer Light absorbing layer KVp
Graininess of image due to fast screen system
Quantum Mottle or “Noise”
To control Quantum Mottle or “Noise” …
Increase mAs and decrease kVp
_____ imaging plates use Barium Fluorhalide doped with Europium as the Photostimulable Phosphor
CR
Indirect Conversion System uses Cesium Iodine which creates light that interacts with amorphous silicon (a-Si) to create electric charge
DR
______ conversion system uses amorphous selenium (a-Se) to produce electric charge
Direct
