Density

1. Radiographic Quality

2. DENSITY (1)
•What exactly is meant by term radiographic
density?
•Radiographic density referred to as the overall
blackening of the film. Density is dependent
on amount of radiation received by the film.
•It is not the technologist’s purposes to
produce an overall black film.
•Technologist is concerned with what is termed
proper density.

3. DENSITY (2(
•A radiographic image that possesses proper
density provides suitable visualization of all of
the structures of interest.
•Any variance from this value of density is
detrimental to radiographic quality.
•Insufficient density, degrading image quality
as excessive density –in fact, perhaps more so.

4. Schematic drawing showing
differential
absorption of x–rays by the
tissues of the
body in conventional
radiography. From most to
least radiodense these are (1)
bone or calcium; (2) all soft
tissues and liquids (muscle,
blood, brain, heart, liver,
urine, etc.) except (3) fat; (4)
air or other gases.

6. DENSITY
Influencing factors?
Controlling factors?
I

7. FACTORS THAT INFLUENCE and CONTROL
VISIBLE RECORDED DETAIL• !
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Factors that influence visible recorded detail
What are they???
Patient factors
Tissue thickness
Physique
Age
Development
Pathology –additive and destructive
Tissue opacity (density(

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- - Technique (mA; s; kV; distanceTechnique (mA; s; kV; distance((

- - Receptor quantum efficiencyReceptor quantum efficiency

- - Image processingImage processing
--Anode heel effectAnode heel effect
--Orthopedic castsOrthopedic casts
--FiltrtionFiltrtion
Density control factorsDensity control factors

9. •A minimal change of 30% is A minimal change of 30% is
necessary to produce noticeable necessary to produce noticeable
difference in radiographic difference in radiographic
density.density.

To increase densityTo increase density
30%30% mAs increase requiredmAs increase required

10. •Density: Kvp/mAs Density: Kvp/mAs
15%15% rulerule
15%15% kv ↑ =50% mAskv ↑ =50% mAs ↓ ↓

KilovoltageKilovoltage

11. •Abdomen: Abdomen: old 200mAx0.5 s =100 mAsold 200mAx0.5 s =100 mAs
new 200 mAx0.6 s= 120 new 200 mAx0.6 s= 120 mAsmAs
• Elbow: Elbow: old 100mAx 0.1 s=10 mAs old 100mAx 0.1 s=10 mAs

new new 100mAx0.13.3 s= 13.3 mAs100mAx0.13.3 s= 13.3 mAs

A “step in time” A “step in time”

12. Distance - Inverse Square Law
•intensity of radiation falling on flat
surface from point source is
inversely proportional to square of
distance from point source
–if distance 2X, intensity drops by 4X
•Assumptions
–point source
–no attenuation
•Cause
–increase in exposure area with
distance
Intensity a 1/d
2
d

13. Intensification factor formulaIntensification factor formula
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Intensifying screenIntensifying screen
Screen intensification factorScreen intensification factor
intensification factorintensification factor = =
exposure without screensexposure without screens
Exposure with screensExposure with screens
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Screen intensification factor
•At 50 kv the intensification factor is 60
•At 60 kv the intensification factor is 80
•At 70 kv the intensification factor is 100

14. •???? ?
•???? ? Intensifying screen speeds and exposuresIntensifying screen speeds and exposures
Screen type Speed value Exposure value
Ultraslow speed (detail( 1/4 4 times par
Slow speed 1/2 2 times par
Par speed (standard( 1 1
High speed 2 ½ times par
Ultrahigh speed 3 1/3 times par
New phosphor material
and rare earth screens
peed*
4 t0 12 ¼ to 1/12 times par
* Screen speed depends upon the type phosphor used, and the type
and speed of the film it is used with

15. EExposure required to maintain radiographic densityxposure required to maintain radiographic density
With difference screen speeds (table top radiographyWith difference screen speeds (table top radiography))
using 60 kvp and having intensification factor of 80using 60 kvp and having intensification factor of 80
Screen type Speed value Exposure value
Nonscreen 400 mAs
Ultraslow speed ¼ 20 mAs
Slow speed ½ 10 mAs
Par speed 1 5 mAs
High speed 2 2.5 mAs
Ultrahigh speed 3 1.66 mAs
New phosphor material or rare
earth speed
4 to 12 1.25 to 0.415 mAs

16. •Manual processing →difficult Manual processing →difficult
to control quality.to control quality.
• Automatic processingAutomatic processing
enable the enable the
technologist to standardize film technologist to standardize film
processingprocessing..

Film processingFilm processing
→→

17. •Has an influence on uniformity Has an influence on uniformity
of overall density of the image.of overall density of the image.
•In specific application, you can In specific application, you can
employ this effect to advantage*employ this effect to advantage*

Anode heel effectAnode heel effect

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**you must place the thicker and/or more dense area toward the cathode end of the x-ray tubeyou must place the thicker and/or more dense area toward the cathode end of the x-ray tube

18. Anode heel effectAnode heel effect

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**you must place the thicker and/or more dense area toward the cathode end of the x-ray tubeyou must place the thicker and/or more dense area toward the cathode end of the x-ray tube

19. •Orthopedic casts adds both Orthopedic casts adds both
thickness and opacity to the partthickness and opacity to the part
•RememberRemember double the mAs for double the mAs for
increased part thickness; increased part thickness;
increased the kvp by 10 % for increased the kvp by 10 % for
increased part opacity.increased part opacity.
Orthopedic castsOrthopedic casts

20. •Added filtration above 2.5 mm Al Added filtration above 2.5 mm Al
increase exposure factors to increase exposure factors to
maintain density.maintain density.
•Remember; added filtration is Remember; added filtration is
used as a means of reducing used as a means of reducing
patient exposure to radiation.patient exposure to radiation.
Filters should not be removed Filters should not be removed
during routine examination. during routine examination.
FiltrationFiltration

21. Radiopacity and radiolucency are relative
terms. The central gray squares are all of
the same density.

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

23. Questions please