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Radiographic Artifacts

NOT ESPECIALLY

OLD ORVALUABLE

Chris Ober, DVM,PhD, DACVR

14 February 2011

Artifacts Defined

Any opacity on the radiograph that does

not correspond to an actual anatomicstructure

Any misrepresentation of an actual

anatomic structure

Anything decreasing radiographic quality

Quick CR primer

Cassette exposed by x-

rays; storage phosphors

excited

Quick CR primer

Cassette exposed by x-

rays; storage phosphors

excited

Cassette put into reader

Quick CR primer

Laser shines onto

detectors

Quick CR primer

Laser shines onto

detectors

Excited phosphors give

off light photons

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Quick CR primer

Laser shines onto

detectors


off light photons

Light photons travel

through light guide

Quick CR primer

Laser shines onto

detectors


off light photons

Light photons travel

through light guide

Image produced by

computer

Quick DR primer

Panel exposed by x-

rays, detectors

excited

Data sent directly to

computer via cord

Image created

Sequence: Film-Screen

Film storage &

handling

Positioning

Exposure

Film handling

Film processing

Manual

Automatic

Image archiving

Sequence: CR (With Cassette)

Cassette storage

Positioning

Exposure Postexposure

Cassette reading

Workstation

Sequence: DR (No Cassette)

Panel storage

Positioning

Exposure Image reading &

transfer

Workstation

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Another Classification System

Color

Black White

Distribution

Focal

Regional or Global

Storage & Pre-Exposure Handling

Artifacts

Screen-Film

Pressure Abrasions & Scratches

Fingerprints

Static electricity

Material in cassette

Fog

Light leak

CR & DR

Storage scatter (CR)

Pressure Artifacts

Film Crease Crescents (SF)

Black & focal

Cause: rough

handling

Pressure from crease

causes activation of

crystals

NOT caused by

fingernail (usually)

Pressure Artifacts

Film Crease Crescents (SF)

Abrasions & Scratches (SF)

Black or white, focal

Cause: rough handling

Black: pressure from

abrasion activatescrystals

White: emulsion has

been removed (scratch)

Can feel texture in

emulsion

Fingerprints (SF)

Focal

White: most common

Oil on fingertips blocksdeveloper

OR

Fixer on fingertips

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Fingerprints (SF)

Focal

White: most common

Oil on fingertips blocks

developer

OR

Fixer on fingertips

Fingerprints (SF)

Black: less common

Developer onfingertips

Prevent:

Keep fingers dry and

clean

Touch only film edges

Hogge JP, et al.

RadioGraphics 1999.

Static Electricity (SF)

Black & focal

Two patterns

Branching

Smudge / Spot

Cause: electrical

discharge


Prevent:

Moderate humidity

Avoid friction while

handling film

Antistatic cassette

cleaners


Hogge JP, et al.

RadioGraphics 1999.

Material in Cassette /

Dirty Screen (SF) White & focal

Sharp margins (close

to film no

penumbra) Cause: Visible light

photons from screen

cant reach and

expose film emulsion

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Material in Cassette /

Dirty Screen (SF) THUS radiolucent

material can stillcause this artifact

Common causes

Hair

Dust

Fog (SF)

Increased blackness,

usually regional orglobal

Definition: any

unwanted film

exposure /

development

Decreased image

contrast and detail

Fog (SF)

Causes:

Light exposure

Heat

(store at < 68 F)

Humidity

(keep at 30-50%)

Radiation (including

scatter)

Chemicals

Old film

Fog (SF)

Hogge JP, et al.

RadioGraphics 1999.

Light Leak (SF)

Black, focal to global

A form of fog

Sources:

Storage bin (along 1edge)

Cassette not closed (1

edge or corner)

Overhead light

Safelight filter crack

Storage Scatter (CR)

Black & global

Like fog unwanted

exposure of CR plate

Causes: Background radiation

Scatter from imaging

procedure

Jimnez DA, et al.

Vet Radiol Ultrasound 2008.

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Positioning Artifacts

Screen-Film

Magnification Foreshortening /

distortion

Patient rotation

Upside-down cassette

Grid cutoff

CR & DR

Magnification Foreshortening /

distortion

Patient rotation

Upside-down cassette

(CR) or panel (DR)

Grid cutoff

Magnification

Object closer to film:

Closer to normal size Sharper margins

Object farther from

film:

Magnified

Less distinct margins

Foreshortening / Distortion

X-ray beam does not

pass perpendicular to

long axis of structure

Differential

magnification of

structure

Foreshortening / Distortion

Patient Rotation

A form of distortion

Lesions may bemasked by atypical

superimposition onnormal anatomy

Unusual projection ofnormal anatomy maybe incorrectlydiagnosed asabnormal

Upside-down Cassette (SF)

White & focal

Springs & latches onback of cassette block

x-ray beam

Global lightness

Lead backing absorbssome x-ray photons(film appearsunderexposed)

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Upside-down Cassette (SF) Upside-down Cassette (SF)

Upside-down Cassette (CR)

White & multifocal

Construction of

cassette back

absorbs x-rays

Pattern depends on

manufacturer

Upside-down Cassette (CR)

Upside-down Panel (DR)

White & multifocal

Electronics in the

back of the panel

absorb x-rays

Grid Cutoff (SF, CR, DR)

White, regional to

global

Orientation of lead

strips in grid requiresappropriate geometry

relative to x-ray beam

Wrong geometry

lead strips attenuate

more x-rays

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Laterally Decentered

Focused Grid

Result: Too white across

entire image

Off-Level Focused Grid

Result: Too white across

entire image

Upside-Down Focused Grid

Result: OK in the center,Severely too white at periphery

Distance Decentered

Focused Grid Similar to upside-

down grid

OK in the center,

Markedly too white at

periphery

Often not as severe

as upside-down grid

Combined Lateral and Distance

Decentering of Grid

Result: OK on one side,

Gradually whiter toward

other side

Exposure Artifacts

Screen-Film

Motion

Double exposure

Overexposure

Underexposure

Material obstructing x-ray

beam

CR & DR

Motion

Double exposure (CR)

Overexposure(Saturation)

Underexposure

Material obstructing x-ray

beam

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Motion (SF, CR, DR)

Blurring of moving

parts Exposure does have

a finite interval

Reduce with:

Better restraint

Sedation

Decreased exposure

time

Motion (SF, CR, DR)

Double Exposure (SF, CR)

Appearance of 2

summated images

Cause: Cassette

inadvertently exposed

more than once

Press exposure trigger

twice

Forget to change

cassette after first view

Double Exposure (SF, CR)

SF: Black, global

2 exposures =

overexposure artifact

CR: Normal grayscale

Wide latitude can

usually accommodate

the overexposure

DR: Cant happen

Image is transferred to

computer immediately

Double Exposure (SF, CR) Overexposure (SF)

Black & global

Patient info label

normal

Cause: Too muchactivation of emulsion

crystals

High mAs or kVp

Line surge

Double exposure, Fog

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Saturation (CR, DR)

Black, may only beapparent in parts ofimage

Just like SFoverexposure

High exposure maxesout sensitivity rangeof detector

Anatomy (esp. thinnerparts) may be burnedthrough

Saturation (CR, DR)

Black, may only beapparent in parts ofimage

Just like SFoverexposure

High exposure maxesout sensitivity rangeof detector

Anatomy (esp. thinnerparts) may be burnedthrough

Paradoxical Overexposure,

Saturation, & Planking (DR)

Paradoxical Overexposure,

Saturation, & Planking (DR)

Underexposure (SF)

White & global

Patient info label

normal

Cause: Too littleactivation of emulsion

crystals

Low mAs or kVp

General x-ray

obstruction

X-ray tube troubles

Underexposure:

Quantum Mottle (CR, DR) Noisy & global

Computer algorithms

adjust image to

remain gray Low signal level

causes grainy

appearance and poor

contrast & sharpness

Cause: As with SF

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Underexposure:

Quantum Mottle (CR, DR)Material Obstructing

X-Ray Beam (SF, CR, DR)

White, focal

Cause: Anyradiopaque structure

in the path of the x-

ray beam

On patient

In patient

On table

On cassette

Material Obstructing


OMG!

Its a fracture fragment!



or gravel on the table.





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Insufficient Mixing (SF) Inadequate Fixation (SF)

Initially film is cloudy

and milky Over time appears

yellow/brown

Dichroic stain

Incomplete Washing / Rinsing (SF)

Fixer remains

Cloudy, sticky residue

Yellow-brown stain

Sulfur smell

Kissing Defects (SF)

Dirty Light Guide (CR)

White & focal

Sharp white line

Cause:

Light emitted fromplate reaches lightguide

Dirt blocks path for anentire line of data

No light along that line= assumption thatthere was no exposure


White & focal

Sharp white line

Cause:




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White & focal

Sharp white line Cause:




Cassette Debris (CR)

White & focal

Sharp margins Essentially the same

as FS dirty cassette

EXCEPT

Cassette Debris (CR)

Problem is that

photons emitted from

plate during reading

dont reach

photomultiplier tube

(Contrast with FS,

where light photons

from screen dont

reach film)

Workstation Artifacts

Screen-Film

Not Applicable

CR & DR

Faulty Transfer (DR)

Clipping

Planking

Uberschwinger

Faulty Transfer (CR, DR)

Appearance: Anything

goes, generally

distorted anatomy

Cause: Problems indata transfer to

workstation

Memory problems

Communication errors

(e.g. loose cables)

Power fluctuation

Faulty Transfer (DR)

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Uberschwinger (CR, DR)

Black & focal

Black lines occuraround dense

structures

Can be mistaken for

loosening or infection

of implants

Cause: Certain

processing algorithms

(edge-enhancement)

Uberschwinger (CR, DR)

What Have We Learned?

People can manage to screw up any stage

of the radiographic process.

Recognizing artifacts and when they occur

is the only way to make good radiographs.

Look up Mr. Yuk on Wikipedia for a video

that scarred my childhood.

04 - artifacts 2011

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