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Radiographic Image Qualities (Photographic (Visibility of Deatil…
Radiographic Image Qualities
Photographic
Visibility of Deatil
Density/Brightness
How dark is the film?
Change Density first
mAs is controlling factor
kVp is influencing factor
kVp is not predictable
changes 2 factors instead of 1
Density is directly related to mAs
density ^ = mAs ^
30% rule
Makes noticeable change in density
increase or decrease mAs by 30%
50% Rule
makes a significant change in density
1/2 or double the mAs
15% Rule
increase or decrease kVp by 15%
doubles or halves mAs density
Contrast
shades of black or grey
difference in adjacent densities
High Contrast= short scale
black to white---> big difference
low kVp
Low Contrast= long scale
many shades of grey
high kVp
Ex: chest xray
no contrast
all one color
types of contrast
Film Contrast
displayed after processing
not affected by patient, x-ray beam, or other factors
Grids
Increase contrast
1 more item...
Absorb scatter
1 more item...
Subject Contrast
contrast given by beam, patient,
and other factors
patient thickness
decrease thickness
w/ compensation= decrease contrast
secondary influencing factors
focal spot size
does not influence contrast
Anode Heel Effect
no effect on contrast
distance
SID
compensated mAs= no effect on contrast
uncompensated mAs= decrease in contrast
OID
^ OID= ^ Contrast
1 more item...
Beam Filtration
^ filtration= ^ effective
Photon energy= decrease contrast
Recorded Contrast
overall contrast of image
Contrast media
Barium
Injested
Small bowel
BA Swallow
Injected
BE
Double
1 more item...
Single
Gadalinium
MRI Contrast
Injected
Iodine
Gastrografin
Suspected or possible perforations
Injested
mAs is influencing factor
kVp is controlling factor
how well are anatomical structures seen?
Geometric
Sharpness
Recorded Detail
Resolution
How sharp is the image?
Umbra
Distinctive sharp edge
Penumbra
Blurring around edge
All images have some
Measured in units
of line pairs/mm
^ lp/mm = ^ resolution
Resolution grid 0.5-5.0 lp/mm
Max the human eye can see
Receptor unsharpness
Film screen contact
Screens
Phosphore size
Layer thickness
Films
Emulsion crystal size
Layer thickness
Distortion
Shape
Alignment
Central Ray
Tube angle
Anatomical part
Film placement
Angle
Central Ray
Tube angle
Film
Anatomical part
Depends on patient....
Build
Condition
Size
Magnification
SID
^ SID = decrease magnification
Increases detail
OID
^ OID = ^ magnification
How true is the shape?
Motion unsharpness
Equipment
Patient
Voluntary
Turning head
Involuntary
Heart pumping
Distance
SID
OID