Sciences Unit 1 Flashcards by Brooke Staley

Radiographic quality=

balance between the photographic and geometric characteristics of our image

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2 Geometric properties of an image

Detail

Distortion

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Detail

degree of accuracy of the structural lines actually recorded on the image

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Distortion

Misrepresentation of the size or shape of the structures

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What properties control geometric detail

recorded detail

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What properties control photographic properties

Visibility of detail

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Recorded Detail def

accuracy of structural lines actually recorded

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Recorded Detail AKA

Sharpness
geometric sharpness
definition
spatial resolution
umbra

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Umbra def

Distinctly sharp area of a shadow

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Penumbra def

imperfect

unsharp shadow

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Term used for measuring detail with film screen

resolution

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How is resolution measured

Line pairs per mm, resolution tool

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3 Factors affecting detail

Geometry
Image Receptor
Motion

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3 Things we have control over to “fix” detail

eliminate motion
reduce OID
reduce FSS

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What 2 factors affect detail

Distance(OID/SID)

FSS

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Why does FSS cause geo unsharpness

beam diverges as they leave the target

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How does distance affect geo unsharpness

^distance = ^divergence

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Geometric blur

area where beam diverges

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Which distace issue is most important to fix if you have to choose 1

OID

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Geometric blur/OID relationship

Direct

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Geo blur/SID relationship

inverse

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What distance options will give you the highest resolution

decreased OID and increased SID

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FSS is controlled by

the line-focus principle

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SFS= _______ geo blur

less

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LFS=________ geo blur

What controls penumbra

FSS

Where does penumbra come from

fact that photons do not come from a point source

FSS/Penumbra relationship

direct

Typical SFS mm

.6mm

Typical LFS mm

1.2 mm

To min geo unsharpness use what focal spot

smalles

to min geo unsharpness use what SID

greatest practical

To min geo unsharpness use what OID

lowest

What shape would produce a perf sharp image

trapezoidal

unsharpness/detail relationship

inverse

GUS formula

FSSxOID / SOD

F/S Image Receptor faster combo = ____ resolution

less

slow combo f/s image receptors

increased resolution and dose

What do you use to test cassette quality

wire mesh

Matrix

the whole picture/all pixels combined

^matrix size=___ resolution

increase

smaller pixel pitch=______ resolution

higher

What IR size should be used for greater detail

smallest IR positive

Monitor quality test used

Monitor quality assurance | used to see that all four corners look alike

What is printer resolution determined by

dpi, dots per inch

Higher dpi=___ resolution

higher

#1 Cause of image unsharpness

Motion

3 Types of motion

Voluntary Involuntary Equipment

Best way to reduce motion

Communication

2 other ways to reduce motion

Exposure time reduction | Immobilization

List of immobilizers in order

1. Male relatives 2. Female relatives 3. non-tech staff 4. techs 5. students

Distortion

Misrepresentation of size and/or the shape of the object being imaged

2 Types of distortion

1. Size distortion | 2. Shape distortion

What is seen with size distortion

Magnification

What 2 things is size distortion affected by

SID | OID

2 things seen with shape distortion

elongation | foreshortening

What is elongation affected by

CR/IR Misalignment

what is foreshortening affected by

part being misaligned

Elongation makes objects appear (2)

longer and thinner

Foreshortening makes objects appear (2)

shorter and wider

size distortion/OID relationship

directly proportional

size distortion/ SID relationship

inversely

Magnification formula

Image width/ object with or | SID/OID

Define macroradiography

When we mag intentionally for very small anatomy

What is Macroradiography AKA?

Magnification

What does macro use to image

microfocus tubes

What benefit does a fractional FSS have?

helps gain back some of the detail lost by the magnification

What is a risk of fractional FSS?

Increased OID increases pt skin dose

What is size distortion referred to

"true distortion"

What causes elongation

tube | IR alignment

What causes Foreshortening

Part not aligned

What is size distortion dependent on

CR/part/image receptor relationship

What should always be perpendicular to the part

What should always be // to the part

What is foreshortening most often caused by

the part not being parellel with iR

What may distortion lead to diagnostically

incorrect dx, not seen or make a fx seem worse

2 bones are superimposed, what will get thrown the furthest when a tube is angled?

The furthest one from the IR, or closest to the tube

2 reasons why we intentionally distort

trying to "undistort" anatomy that may not be parallel to the IR To prevent superimposition of one anatomical structure over another

What is intentional distorment AKA

Displacement

Sciences Unit 1 Flashcards

(79 cards)