Radiographic ImageRadiographic Image

Obtaining the best diagnostic image Obtaining the best diagnostic image and good patient care are the two and good patient care are the two

ultimate goals of a technologistultimate goals of a technologist

IntroductionIntroduction

What is meant by an image that of What is meant by an image that of radiographic quality?radiographic quality?

Sharp edges imageSharp edges image Unsharp edges imageUnsharp edges image

Radiographs small bone with shot embedded in itRadiographs small bone with shot embedded in it

Motion blur (unsharpness)

Involuntary patient motion during radiography

Good VisibilityGood Visibility Poor VisibilityPoor Visibility

X-ray Sinuses

An image of An image of radiographicradiographic qualityquality is the one is the one that possesses :that possesses :

Sharpness &Sharpness & Visibility Visibility

Sharpness Sharpness

Ability to record individual lines that actually Ability to record individual lines that actually form the image keen, distinct and thin-form the image keen, distinct and thin-edged.edged.

SharpnessSharpness is geometric properties of is geometric properties of radiograph.radiograph.

It is measurable factor of radiographic It is measurable factor of radiographic quality.quality.

VisibilityVisibility

Ability to discrete distant objectAbility to discrete distant object

It is photographic propertiesIt is photographic properties

VisibilityVisibility is quality factor of radiographic image. is quality factor of radiographic image. To determine the visibility, you should examine the To determine the visibility, you should examine the

image for:image for: DensityDensity CCoonnttrraasstt

The quality of the manifest image is The quality of the manifest image is assessed forassessed for

Photographic Photographic propertiesproperties

VisibilityVisibility DensityDensity

ContrastContrast

Geometric propertiesGeometric properties SharpnessSharpness

Recorded detailRecorded detail distortiondistortion

Balance of sharpness and visibility Balance of sharpness and visibility for radiographic qualityfor radiographic quality

Radiographic QualityRadiographic Quality

Major Radiographic PropertiesMajor Radiographic Properties

Recorded detailRecorded detail DistortionDistortion DensityDensity contrastcontrast

Major ConsiderationsMajor Considerations

(1) Recorded detail: (1) Recorded detail: The actual formation of the The actual formation of the

structural lines of the image as recorded on structural lines of the image as recorded on the film.the film.

(2) Distortion:(2) Distortion: The mispresntation of actual size or The mispresntation of actual size or

shape of structures as recorded on the film, shape of structures as recorded on the film,

Major ConsiderationsMajor Considerations

(3)Density:(3)Density: The completeness of the recording of image The completeness of the recording of image

on the film, indicating that sufficient quantities of on the film, indicating that sufficient quantities of radiation passed through the body and reached radiation passed through the body and reached the film.the film.

(4)Contrast:(4)Contrast: The ability to distinguish each recorded The ability to distinguish each recorded

structure apart from adjacent structures, indicating structure apart from adjacent structures, indicating that proper penetration of the part was achieved.that proper penetration of the part was achieved.

Visual Acuity of Human EyeVisual Acuity of Human Eye

The human eye enables the viewer to The human eye enables the viewer to discriminate up to 5 lie pairs within the discriminate up to 5 lie pairs within the space of a millimeter. (a line pairs means a space of a millimeter. (a line pairs means a line and space.) line and space.)

Level of unsharpnessLevel of unsharpness Visibility = 5 line pairs/mmVisibility = 5 line pairs/mm >0.2 mm line pair width = intolerable level >0.2 mm line pair width = intolerable level

Factors Influence The Sharpness Factors Influence The Sharpness

Motion Motion

MaterialMaterial

} Measurable} Measurable Geometry Geometry

Motion UnsharpnessMotion Unsharpness

VoluntaryVoluntary referred to as motion that referred to as motion that under conscious control of the will.under conscious control of the will.

InvoluntaryInvoluntary motion attributed to the motion attributed to the physiological action of the of the bodyphysiological action of the of the body

Factors in Control of MotionFactors in Control of Motion

Explanation of the procedure to the patient.Explanation of the procedure to the patient.

Immobilization of the part.Immobilization of the part.Whole body immobilizersWhole body immobilizers

Selected part immobilizationSelected part immobilization

Reduction of exposure time.Reduction of exposure time.

Immobilization aidsImmobilization aids

Immobilization of the part to avoid motional blurring.Immobilization of the part to avoid motional blurring.

Reduction of Exposure TimeReduction of Exposure Time

1- Milliamperage/Time Relationship1- Milliamperage/Time Relationship

If the original techniqye required 100 mAs:If the original techniqye required 100 mAs:

100 mA x 1sec =100 mAs100 mA x 1sec =100 mAs

Change to :Change to :

400 mA x 0.25 sec = 100 mAs400 mA x 0.25 sec = 100 mAs

Reduction of Exposure TimeReduction of Exposure Time

2- Intensifying Screen Speeds:2- Intensifying Screen Speeds: The radiographic density can be maintained with The radiographic density can be maintained with

an increase in the in the speed of intensifying an increase in the in the speed of intensifying screens and an appropriate reduction in the screens and an appropriate reduction in the overall mAs . For example:overall mAs . For example:

If the original technique required 100 mAs:If the original technique required 100 mAs: 400 mAs x 0.25 sec =100 mAs400 mAs x 0.25 sec =100 mAs Change to:Change to: 400 mAs x 0.125 sec = 50mAs with high speed screen.400 mAs x 0.125 sec = 50mAs with high speed screen.

A demonstrates quantum mottle B demonstrates recorded details .A demonstrates quantum mottle B demonstrates recorded details .

Material UnsharpnessMaterial Unsharpness

Three factors influence material Three factors influence material unsharpness:unsharpness:

FilmFilm

Intensifying screen.Intensifying screen.

Film-screen contact Film-screen contact

The three major factors influencing material unsharpnessThe three major factors influencing material unsharpness

Radiographic FilmRadiographic Film

Non screen Film:Non screen Film:

Has thicker emulsion.Has thicker emulsion. Two to six times faster compared with Two to six times faster compared with

screen-type film used with direct exposure.screen-type film used with direct exposure. Not recommended for use with intensifying Not recommended for use with intensifying

screen. screen.

Parallax Parallax

Radiographic FilmRadiographic Film

Screen -Type FilmScreen -Type Film

Has thinner emulsion.Has thinner emulsion. Slow in speed when used with direct Slow in speed when used with direct

exposure.exposure. There is a significant increase in speed There is a significant increase in speed

when used with intensifying screen. when used with intensifying screen.

Comparison of typical exposure factors in an Comparison of typical exposure factors in an AP projection of the knee(12:1moving grid)AP projection of the knee(12:1moving grid)

– Type of radiography exposure factorsType of radiography exposure factors– ------------------------------------------------------------------------------------------------------------------------------– Ultrahigh speed screens 20mAs(100mAx0.2 sec at 60kvp)Ultrahigh speed screens 20mAs(100mAx0.2 sec at 60kvp)

– High speed screens 30mAs(100mAx0.3 sec at 60kvp)High speed screens 30mAs(100mAx0.3 sec at 60kvp)

– Par speed screens 60mAs(100mAx0.6 sec at 60kvp)Par speed screens 60mAs(100mAx0.6 sec at 60kvp)

– Slow speed screen 120mAs(100mAx1.2 sec at 60kvp)Slow speed screen 120mAs(100mAx1.2 sec at 60kvp)

– Direct exposure 4800mAs(100mAx12 sec at 60kvp)Direct exposure 4800mAs(100mAx12 sec at 60kvp)

Quantum MottleQuantum Mottle

Radiographic noise produced by the random Radiographic noise produced by the random interaction of x-rays with an intensifying interaction of x-rays with an intensifying screen. This effect is more noticeable when screen. This effect is more noticeable when very high rare-earth systems are used at very high rare-earth systems are used at high kvp. high kvp.

Quantum Mottle (image noise) Quantum Mottle (image noise)

Occurs more often when fast screens and high Occurs more often when fast screens and high kvp techniques are used.kvp techniques are used.

Screen speed increased because of:Screen speed increased because of: 1- High absorb percentage of x-ray this is called 1- High absorb percentage of x-ray this is called

detective quantum efficiency (DQE).detective quantum efficiency (DQE). 2- The amount of light emitted for each x-ray 2- The amount of light emitted for each x-ray

absorbed is also high. This is called conversion absorbed is also high. This is called conversion efficiency (CE)efficiency (CE)

Quantum increases with higher CE Quantum increases with higher CE but not with higher DQE. but not with higher DQE.

(A) demonstrates (A) demonstrates quantum mottle quantum mottle

(B)(B)

demonstrates demonstrates recorded detailsrecorded details

Diffusion of light decrease image Diffusion of light decrease image sharpnesssharpness

Advantages Using Nonscreen FilmAdvantages Using Nonscreen Film

Improved Recorded details, Sharpness Improved Recorded details, Sharpness Resolution.Resolution.

Production of longer scale contrast.Production of longer scale contrast. Increase exposure latitude.Increase exposure latitude. Lack of artifacts associated with dirty Lack of artifacts associated with dirty

screen.screen.

However ,with increased of radiation dose. However ,with increased of radiation dose.

Comparison screen speed to image Comparison screen speed to image detailsdetails

Poor film screen contactPoor film screen contact

Poor film-screen contactPoor film-screen contact

Good film-screen contactGood film-screen contact

DENSITYDENSITY

CONTROLLING FACTORS?CONTROLLING FACTORS?

INFLUENCING FACTORS?INFLUENCING FACTORS?

CONTRASTCONTRAST

Subject ContrastSubject Contrast Film (IR) ContrastFilm (IR) Contrast

CONTRASTCONTRAST

CONTROLLING FACTORS?CONTROLLING FACTORS?

INFLUENCING FACTORS?INFLUENCING FACTORS?

FACTORS THAT CONTROL AND FACTORS THAT CONTROL AND INFLUENCE VISIBLE RECORDED DETAILINFLUENCE VISIBLE RECORDED DETAIL

What are they???What are they???

Modifying patient exposureModifying patient exposure– PediatricsPediatrics– Projections/positionsProjections/positions– Casts/splintsCasts/splints– Body habitusBody habitus– Pathology –additive and destructivePathology –additive and destructive– Soft tissueSoft tissue

- - Subject (tissue thickness and density)Subject (tissue thickness and density) - Technique (mA; s; kV; distance)- Technique (mA; s; kV; distance) - Receptor quantum efficiency- Receptor quantum efficiency - Image processing- Image processing

Density factorsDensity factors

Improved Quantum Efficiency

% Relative Dose

1919 1925 1941 1955 1981 1991 1999

0

20

40

60

80

100

Contrast Resolution vs. DoseContrast Resolution vs. Dose ( cm bone, 40 kV)( cm bone, 40 kV)

Signal Contrast Ratio, S

X,

mR

- m

m2

`

0.0001 0.001 0.01 0.1 1

10 -4

10 -2

10 -0

10 +2

10 +4

10 +6

not detectable

visible withoutcontrast enhancement

visible with contrast

enhancement

40 KeV X-Rays

10 -10

10 -8

10 -6

10 -4

10 -2

X, C

/kg

- m

m2

S = 0.025

Derived from: Motz JW, Danos M. Image information content and patient exposure. Med Phys 1978; 5: 8-22.

Subject Subject Signal Signal Exposure energy Exposure energy Receptor Receptor ProcessingProcessing

Contrast sourcesContrast sources

Radiopacity and radiolucency are relativeterms. The central gray squares are all ofthe same density.

The left triangle seems lighter than the right one. This is only an illusion - they are equal in density.

Kanisza triangle: optical illusions can occur when interpreting black and white images.