11

Components of Components of Image Quality Image Quality

& & Radiographic Radiographic

ArtifactsArtifacts

Radiologic Technology ARadiologic Technology A

SPRING 2012SPRING 2012

22

X-ray Exposure FactorsX-ray Exposure Factors

Radiographic Density & ContrastRadiographic Density & Contrast

Components of Components of Image Quality Image Quality

Radiographic ArtifactsRadiographic Artifacts

33

Review Review

Primary radiation exits the tubePrimary radiation exits the tube

Interacts with various densities in the body Interacts with various densities in the body

Photons may be absorbedPhotons may be absorbed

Scattered Scattered

Passed through without any interference Passed through without any interference to the cassette or image receptor (IR)to the cassette or image receptor (IR)

44

How well we can see something on the imageHow well we can see something on the image

55

Image detail Image detail is affected by:is affected by:

Photographic Photographic propertiesproperties

and and Geometric propertiesGeometric properties

66

Photographic Photographic PropertiesProperties

1.1.Contrast Contrast

2.2.DensityDensity

77

Factors Affecting Factors Affecting DensityDensity Primary control factorPrimary control factor

– mAmA– Time (seconds)Time (seconds)

Influencing factorsInfluencing factors– kVpkVp– GridsGrids– Beam restrictionBeam restriction– Body structures (size of pt, pathologyBody structures (size of pt, pathology– ProcessingProcessing– SID & OIDSID & OID– Film Screen combinations Film Screen combinations

88

Primary Controlling Primary Controlling Factor of DensityFactor of Density mAs mAs

mA = mA = AMOUNTAMOUNT of electrons sent of electrons sent across the tube combined with TIME across the tube combined with TIME (S) = mAs(S) = mAs

mAs controls mAs controls DENSITY DENSITY on radiographon radiograph primary function of mAs is DENSITYprimary function of mAs is DENSITY

99

Imagine this…Imagine this… If the mA station is changed from 200 to If the mA station is changed from 200 to

400 mA, twice as many electrons will 400 mA, twice as many electrons will flow from the cathode to the anode.flow from the cathode to the anode.

From 10 mA to 1000 mA = 100 x moreFrom 10 mA to 1000 mA = 100 x more

mA controls mA controls how manyhow many electrons are electrons are coming at the targetcoming at the target

mAs is a combination of mAs is a combination of how manyhow many and and for for how longhow long (seconds)(seconds)

1010

10 mA 1000 mA

1111

1212

Changing Mas – Changes DensityChanging Mas – Changes Density + 25 % + 50 % + 25 % + 50 % masmas

1313

Influencing Factor Influencing Factor on Density:on Density:

kVpkVp

1414

Change in kVpChange in kVp kVp controls the energy level of the kVp controls the energy level of the

electrons and subsequently the energy electrons and subsequently the energy of the x-ray photons.of the x-ray photons.

A change from 72 kVp will produceA change from 72 kVp will producex-rays with a lower energy than atx-rays with a lower energy than at82 kVp82 kVp

Difference between a ball traveling 72 Difference between a ball traveling 72 mph and 82 mph (how much energy did mph and 82 mph (how much energy did it take to throw the ball at the rates?)it take to throw the ball at the rates?)

1515

+ 15% kvp - 15% + 15% kvp - 15% kvpkvp

Increasing kVp = increase energy reaching the IR

This will also influence the density on the image

1616

Radiolucent vs. Radiolucent vs. RadiopaqueRadiopaque

RadiolucentRadiolucent materials materials allow x-ray photons to pass allow x-ray photons to pass through easily (soft tissue).through easily (soft tissue).

RadiopaqueRadiopaque materials are materials are not easily penetrated by x-not easily penetrated by x-rays (bones)rays (bones)

1717

Creating the ImageCreating the Image

1.1. Transmission Transmission – no interactionno interaction– Responsible for Responsible for

dark areasdark areas2.2. ScatterScatter

1.1. (grays) – produces (grays) – produces no diagnostic infono diagnostic info

3.3. AbsorptionAbsorption1.1. (photoelectric (photoelectric

effect)effect)– Responsible for Responsible for

light areaslight areas

1818

ImagesImages

DENSITYDENSITY = THE AMOUNT OF = THE AMOUNT OF BLACKENING “DARKNESS” ON BLACKENING “DARKNESS” ON THE RADIOGRAPH (mAs)THE RADIOGRAPH (mAs)

CONTRASTCONTRAST – THE DIFFERENCES – THE DIFFERENCES BETWEEN THE BLACKS TO THE BETWEEN THE BLACKS TO THE WHITES (kVp)WHITES (kVp)

1919

Why you see what you Why you see what you see…see… The films or images have different levels of The films or images have different levels of

density – different shades of graydensity – different shades of gray

X-rays show different features of the body in X-rays show different features of the body in various shades of gray. various shades of gray.

The gray is darkest in those areas that do not The gray is darkest in those areas that do not absorb X-rays well – and allow it to pass absorb X-rays well – and allow it to pass throughthrough

The images are lighter in dense areas (like The images are lighter in dense areas (like bones) that absorb more of the X-rays.bones) that absorb more of the X-rays.

2020

Patient Body Size Patient Body Size and and

PathologyPathology

2121

3 Different Body Habitus3 Different Body HabitusHypersthenic Sthenic HyposthenicHypersthenic Sthenic Hyposthenic

Thank you to the 3 men in my life ! DCharman

Dr. Charman, Eric Guzman, Adam Guzman

2222

PATHOLOGY Pleural Effusion Excessive

fluid in lung

More dense than air

2323

PneumoniaPneumonia

2424

The right lung is almost completely collapsed;

vascular shadows can not be seen in this area (arrow).

Pneumothorax

Lung collapses

No tissue in space

Easy to penetrate with x-ray photons

2525

LungLungCancerCancer

2626

LUNG CANCERLUNG CANCER

2727

Density and ImagesDensity and Images

2828

Goal: Producing optimal radiographsGoal: Producing optimal radiographs

DENSITYDENSITY

Too dark Too light

2929

3030

Controlling Factor ofControlling Factor ofContrastContrast

3131

Controlling Factor of Controlling Factor of ContrastContrast

1.1. Kilovolts to anode side – kVpKilovolts to anode side – kVp

2.2. Kilovolts controls Kilovolts controls how fasthow fast the the electrons are sent across the tubeelectrons are sent across the tube

3.3. kVp – controls kVp – controls CONTRAST CONTRAST on on imagesimages

3232

Producing optimal radiographsContrast Scale

Long scale short scale

3333

3434

Scale of Contrast?Scale of Contrast? Which one is “better” Which one is “better” How does the kVp affect these How does the kVp affect these images?images?

3535

Beam Restriction Beam Restriction and and GridsGrids

3636

ScatterScatter

– Creates fogCreates fog– Lowers contrast (more grays)Lowers contrast (more grays)

Increases as Increases as – kV increaseskV increases– Field size increasesField size increases– Thickness of part increasesThickness of part increases

3737

Effects of collimation Effects of collimation (beam restriction) on (beam restriction) on scatterscatter

3838

Collimate to Collimate to area of interest area of interest -reduces -reduces scatter and scatter and radiation dose radiation dose to the patientto the patient

3939

GridsGrids

A device with lead strips that is A device with lead strips that is placed between the patient and placed between the patient and the cassettethe cassette

Used on larger body parts to Used on larger body parts to reduce the number of scattering reduce the number of scattering photons from reaching the imagephotons from reaching the image

4040

Basic Grid Basic Grid ConstructionConstruction

• Radiopaque lead stripsRadiopaque lead strips

• Separated by radiolucent interspace Separated by radiolucent interspace material - Typically aluminummaterial - Typically aluminum

Allow primary radiation to reach the Allow primary radiation to reach the image receptor (IR)image receptor (IR)

Absorb most scattered radiationAbsorb most scattered radiation

Primary disadvantage of grid use Primary disadvantage of grid use – Grid lines on filmGrid lines on film

4141

GRIDSGRIDS

4242

Grid is placedGrid is placedbetween patient (behind between patient (behind table or upright bucky) & table or upright bucky) & cassettecassette

4343

Grids absorb scatter –Grids absorb scatter –prevents it from reaching prevents it from reaching the imagethe image

GRID

STOPS

SCATTER

4444

4545

Contrast changes with the use of a grid

Less scatter radiation – shorter scale = “better contrast”

With Grid No Grid

4646

GRIDS GRIDS CAN CAN

LEAVE LEAVE LINESLINES

ON THE ON THE IMAGE IMAGE

4747

GEOMETRIC PropertiesGEOMETRIC Properties1.1. Recorded DetailRecorded Detail

2.2. DISTORTIONDISTORTION1.1. Size Size distortion distortion

1.1. MagnificationMagnification

2.2. ShapeShape distortion distortion1.1. Elongation Elongation 2.2. ForeshorteningForeshortening

4848

RECORDED DETAILRECORDED DETAIL

4949

RECORDED DETAILRECORDED DETAILThe degree of sharpness The degree of sharpness in an object’s borders in an object’s borders and structural details.and structural details.

How “clear” the object How “clear” the object looks on the radiographlooks on the radiograph

5050

Recorded DetailRecorded Detail

The degree of sharpness in an object’s The degree of sharpness in an object’s borders and structural details.borders and structural details.

Other names:Other names:

-sharpness of detail-sharpness of detail

-definition-definition

-resolution-resolution

-degree of -degree of noisenoise

5151

RESOLUTION TEST

TOOLS

LINE PAIRS/ MM

Depicts how well you can see the differences in structures

More lines=more detail

5252

5353

Factors that affectFactors that affectRecorded DetailRecorded Detail Geometric unsharpnessGeometric unsharpness

OID SID SIZE SHAPEOID SID SIZE SHAPE Motion unsharpness (blurring)Motion unsharpness (blurring) Intensifying Screens Intensifying Screens Film Speed / CompositionFilm Speed / Composition Film – Screen contactFilm – Screen contact Kvp & Mas (density / visibility)Kvp & Mas (density / visibility)

5454

5555

MOTION MOTION

AKAAKA

BlurringBlurring

5656

MotionMotion Can be voluntary or involuntaryCan be voluntary or involuntary

Best controlled by short exposure Best controlled by short exposure timestimes

Use of careful instructions to the pt.Use of careful instructions to the pt.

Suspension of pt. respirationSuspension of pt. respiration

Immobilization devicesImmobilization devices

5757

5858

Decrease Motion Decrease Motion UnsharpnessUnsharpness

1.1. Instruct patient not to move or Instruct patient not to move or breathbreath

2.2. Use Immobilization devicesUse Immobilization devices

3.3. Use Short exposure timesUse Short exposure times

4.4. Lock equipment in placeLock equipment in place

5959

Blurring of image due to patient movement during exposure.

6060

6161

Object UnsharpnessObject Unsharpness

Main problem is trying to image a 3-D Main problem is trying to image a 3-D object on a 2-D film.object on a 2-D film.

Human body is not straight edges and Human body is not straight edges and sharp angles.sharp angles.

We must compensate for object We must compensate for object unsharpness with factors we can unsharpness with factors we can control: focal spot size, SID & OIDcontrol: focal spot size, SID & OID

6262

SID SID Source to Image DistanceSource to Image Distance

The greater the source X-ray tube) The greater the source X-ray tube) to image (cassette) distance, the to image (cassette) distance, the greater the image sharpness.greater the image sharpness.

Standard distance = 40 in. most Standard distance = 40 in. most examsexams

Exception = Chest radiography 72 Exception = Chest radiography 72 in.in.

6363

The SID will influence magnification. The farther away – the less magnified

↑SID ↓ MAGNIFICATION

6464

SIDSID Shine a flashlight on a 3-D object, Shine a flashlight on a 3-D object,

shadow borders will appear “fuzzy” shadow borders will appear “fuzzy” -On a radiograph called -On a radiograph called

PenumbraPenumbra

Penumbra (fuzziness) obscures Penumbra (fuzziness) obscures true border – true border – umbraumbra

Farther the flashlight from object = Farther the flashlight from object = sharper borders. Same with sharper borders. Same with radiography.radiography.

6565

6666

OIDOIDObject to Image DistanceObject to Image Distance The closer the object to the film, the The closer the object to the film, the

sharper the detail.sharper the detail.

OID OID , penumbra , penumbra , sharpness , sharpness OID OID , penumbra , penumbra , sharpness , sharpness

Structures located deep in the body, Structures located deep in the body, radiographer must know how to position radiographer must know how to position to get the object closest to the film.to get the object closest to the film.

6767

The position of the structure in the body will influence how magnified it will be seen on the image

The farther away – the more magnified

6868

6969

DistortionDistortion Misrepresentation of the true size Misrepresentation of the true size

or shape of an objector shape of an object

– MAGNIFICATIONMAGNIFICATION – size distortionsize distortion

– TRUE DISTORTION TRUE DISTORTION – shape distortionshape distortion

7070

MAGNIFICATIONMAGNIFICATION

TUBE CLOSE TO THE PART (SID)TUBE CLOSE TO THE PART (SID)

PART FAR FROM THE CASSETTE PART FAR FROM THE CASSETTE (OID)(OID)

7171

7272

http://http://www.coursewareobjects.com/www.coursewareobjects.com/objects/mroimaging_v1/mod04i/objects/mroimaging_v1/mod04i/0416a.htm0416a.htm

7373

Size Distortion & OIDSize Distortion & OID

If source is kept constant, OID will If source is kept constant, OID will affect magnificationaffect magnification

As OID As OID , magnification , magnification

The farther the object is from the The farther the object is from the film, the more magnification film, the more magnification

7474

7575

•In terms of recorded detail and magnification the best image is produced with a

•small OID & large SID

7676Minimal magnification small OID

Magnification - large OID

7777

Size Distortion & SIDSize Distortion & SID Major influences: SID & OIDMajor influences: SID & OID

As SID As SID , magnification , magnification

Standardized SID’s allow Standardized SID’s allow radiologist to assume certain amt. radiologist to assume certain amt. of magnification factors are of magnification factors are presentpresent

Must note deviations from Must note deviations from standard SIDstandard SID

7878

7979

8080

8181

40” SID VS 72” SID 40” SID VS 72” SID

8282

8383

SHAPE DISTORTIONSHAPE DISTORTION

ElongationElongation

and and

ForeshorteningForeshortening

8484

Shape DistortionShape Distortion

Misrepresentation of the shape of Misrepresentation of the shape of an objectan object

Controlled by alignment of the Controlled by alignment of the beam, part (object), & image beam, part (object), & image receptorreceptor

Influences: Central ray angulation Influences: Central ray angulation & body part rotation& body part rotation

8585

A = goodA = goodB & C = shape distortionB & C = shape distortion (elongation of part) (elongation of part)

8686

D & E = D & E = shape distortionshape distortion (foreshortening of part) (foreshortening of part)

8787

Image DistortionImage Distortion

When the part to be imaged – When the part to be imaged – does not lay parallel with the IR does not lay parallel with the IR (cassette)(cassette)

If the Central Ray is not If the Central Ray is not perpendicular to the part perpendicular to the part – CR should be at right angle with the CR should be at right angle with the

cassettecassette

8888

Central Ray AngulationCentral Ray Angulation Body parts are not always 90 Body parts are not always 90

degrees from one anotherdegrees from one another

Central ray angulation is used to Central ray angulation is used to demonstrate certain details that demonstrate certain details that can be hidden by superimposed can be hidden by superimposed body parts.body parts.

Body part rotation or obliquing the Body part rotation or obliquing the body can also help visualize body can also help visualize superimposed anatomy.superimposed anatomy.

8989

Central RayCentral Ray Radiation beam diverges from the tube Radiation beam diverges from the tube

in a pyramid shape.in a pyramid shape.

Photons in the center travel along a Photons in the center travel along a straight line – straight line – central raycentral ray

Photons along the beam’s periphery Photons along the beam’s periphery travel at an angletravel at an angle

When central ray in angled, image When central ray in angled, image shape is distorted.shape is distorted.

9090

9191

9292

9393

Elongation Foreshortened Elongation Foreshortened NormalNormal

9494

9595

Distortion (object & film not parallel)

Distortion (x-ray beam not centered over object & film)

9696

Distortion of multiple objects in same image (right) due to x-ray beam not being centered over objects.

9797

Focal Spot SizeFocal Spot Size

Smaller x-ray beam width will produce a Smaller x-ray beam width will produce a sharper image.sharper image.

Fine detail = small focal spot (i.e. small Fine detail = small focal spot (i.e. small bones)bones)

General radiography uses large focal General radiography uses large focal spotspot

Beam from penlight size flashlight vs. Beam from penlight size flashlight vs. flood light beamflood light beam

9898

ANODE

ANODE

9999

THE SMALLER THE BEAM TOWARDS THE PATIENT - THE BETTER THE DETAIL OF THE IMAGE PRODUCED

100100

FOCAL SPOT ANGLEFOCAL SPOT ANGLE

SMALLER ANGLE – SMALLER BEAM AT PATIENT

101101

ARTIFACTS:ARTIFACTS:AN UNWANTED DENSITYAN UNWANTED DENSITYON THE FILMON THE FILM

http://www.xray2000.co.uk/

102102

Artifacts - TypesArtifacts - Types

Processing ArtifactsProcessing Artifacts

Exposure ArtifactsExposure Artifacts

Handling & Storage Handling & Storage ArtifactsArtifacts

103103

Processing ArtifactsProcessing Artifacts

Emulsion pickoffEmulsion pickoff Chemical fogChemical fog Guide-shoe marksGuide-shoe marks Water marksWater marks Chemical spotsChemical spots Guide-shoe & roller scratchesGuide-shoe & roller scratches

104104

Developer Spots

105105Water spot

106106

Discolored film due to hypo (fixer) retention.

Chemicals not washed off – over time will turn

film brown

107107

Scratch marks from rollers in automatic processor.

108108

Exposure ArtifactsExposure Artifacts

MotionMotion Improper patient positionImproper patient position Wrong screen-film matchWrong screen-film match Poor film/screen contactPoor film/screen contact Double exposureDouble exposure Warped cassetteWarped cassette Improper grid positionImproper grid position

109109

ArtifactArtifact

110110

111111

Blurred image due to patient motion

112112

PATIENT ARTIFACT - PATIENT ARTIFACT - JEWERLYJEWERLY

113113

Handling & Storage Handling & Storage ArtifactsArtifacts Light fogLight fog Radiation fogRadiation fog StaticStatic Kink marksKink marks ScratchesScratches Dirty cassettesDirty cassettes

114114

Crimping /cresent Crimping /cresent markmark

115115

Double Exposure

2 exposures made on top of each other –

from poor handling of cassettes

116116

117117

Static electricity

118118

Dirt on screen mimicking a foreign object.

119119

Scratch marks from improper handling.

120120

Light fog

121121

Kink mark or nail pressure mark

122122

castcast

123123

POOR SCREEN POOR SCREEN CONTACTCONTACT

124124

Patient motionPatient motion

125125

motionmotion

126126

Double Double exposureexposure

ChildChild

127127

PoorPoorscreen screen contactcontact

128128

Double exposureDouble exposure

129129

??

130130

??

131131

132132

Pt clothing

133133

Hip replacement

134134

2 chest tubes in the patient

135135Patient swallowed batteriesWhat size are they?

136136

137137

PATHOLOGY NOT PATHOLOGY NOT ARTIFACTARTIFACT

138138

Name &Name & cause causeof this?of this?

139139

scratches

140140

Digital image

Mis-

Registration

error

141141

Roller marks from film stuck –

then pulled from processor

142142

Hardware

In cervical

spine

143143

Dust in imaging plate can Dust in imaging plate can cause white marks on cause white marks on image image

Both in film/screen and Both in film/screen and computed radiographycomputed radiography

144144

E E G MONITOR

145145

What do you

See?

2 exposures

146146

147147

148148

Evaluating ImagesEvaluating Images

What do you think?What do you think?

149149

See anythingSee anythingwrong wrong

with with this this

image?image?

150150

Contrast? What influences this? (kVp in Contrast? What influences this? (kVp in f/s)f/s)

151151

Collimation – reducing the size of beamCollimation – reducing the size of beamhelps to improve the image, and reduce the helps to improve the image, and reduce the dose to the patientdose to the patient

152152

?