Factors affecting the Factors affecting the radiographicradiographic

image and film faults image and film faults

..

Image qualityImage quality

I. ContrastI. Contrast

II. Image geometryII. Image geometry

III. Characteristics of the X-ray beamIII. Characteristics of the X-ray beam

I. ContrastI. Contrast

Subject contrastSubject contrast

Film contrastFilm contrast

Fog and scatterFog and scatter

Subject contrastSubject contrast

Differences in tissue thicknessDifferences in tissue thickness

Differences in tissue densityDifferences in tissue density

kV or penetrating power of the kV or penetrating power of the

radiation beam radiation beam

Film contrastFilm contrast

The characteristic curve of the filmThe characteristic curve of the film

Optical density Optical density

Type of film- direct or indirect actionType of film- direct or indirect action

ProcessingProcessing

Fog and scatterFog and scatter

Fogged filmFogged film

Scatter radiation from within the Scatter radiation from within the patient’spatient’s

tissues tissues

Perception of the radiographic Perception of the radiographic imageimage

Partial images-we all Partial images-we all seesee the same the same partial images but we don’t partial images but we don’t necessarily necessarily perceive perceive the same objectthe same object

ContrastContrast

ContextContext

Effect of partial imageEffect of partial image

The effect of contrastThe effect of contrast

The effect of contextThe effect of context

Image geometryImage geometry

Positioning of the film, object and x-ray Positioning of the film, object and x-ray beambeam

Focal spot size and principle of line focusFocal spot size and principle of line focus

Focal spot-object distance (FSOD), Focal spot-object distance (FSOD), object-object-

to film-distance (OFD)to film-distance (OFD)

Ideal image geometry Ideal image geometry requirementsrequirements

Focal spot size, heat Focal spot size, heat distribution and image distribution and image

sharpnesssharpness Focal spot 1mmFocal spot 1mm

Heat needs to be distributed over as Heat needs to be distributed over as largelarge

as possible areaas possible area

Principle of line focus Principle of line focus

Focal spot-to film-Focal spot-to film-distance(FSFD)distance(FSFD)

FSFDFSFD

Increasing the distance between the Increasing the distance between the focalfocal

spot and the object results in an spot and the object results in an imageimage

with increased sharpness and less with increased sharpness and less

magnification of the objectmagnification of the object

Object-to film- distance Object-to film- distance (OFD)(OFD)

Decreasing the distance between theDecreasing the distance between the

object and the film increases theobject and the film increases the

sharpness and result in less sharpness and result in less magnificationmagnification

of the objectof the object

Image shape distortionImage shape distortion

Cont’dCont’d

Practical factors Practical factors influencing image qualityinfluencing image quality

The X-ray equipmentThe X-ray equipment The image receptor/screen The image receptor/screen

combinationcombination ProcessingProcessing The patientThe patient The operator and radiographic The operator and radiographic

techniquetechnique

Typical film faultsTypical film faults

I.I. Film too darkFilm too dark OverexposureOverexposure

OverdevelopmentOverdevelopment

FoggingFogging

Thin patients tissuesThin patients tissues

Films with inadequate Films with inadequate contrastcontrast

Processing errorsProcessing errors

Exposure errorsExposure errors

Image unsharp and Image unsharp and blurredblurred

Movement of the patient during Movement of the patient during the exposurethe exposure

Excessive bending of the film Excessive bending of the film during the exposureduring the exposure

Poor film/screen contact within Poor film/screen contact within the cassettethe cassette

Film markedFilm marked

Film packet bent by the operatorFilm packet bent by the operator Careless handling of the film in the Careless handling of the film in the

darkroom :darkroom :- Finger printsFinger prints- Finger nailsFinger nails- BendingBending- Static electricityStatic electricity

Operator positioning faultsOperator positioning faults

1.Incorrect placement of the film packet1.Incorrect placement of the film packet Back to front, image of the lead foil Back to front, image of the lead foil

evidentevident ( film also too pale)( film also too pale) Inadvertently used twice, double Inadvertently used twice, double

exposureexposure (films also too dark)(films also too dark) Not covering the area of interestNot covering the area of interest