This document contains a series of images and text from a lab test on density, contrast, distortion, and detail in radiography. It demonstrates how various technical factors like kVp, mAs, filtration, grid use, and collimation can affect the density, contrast, and detail visible on the radiographic image. Specifically, it shows that density increases with higher mAs, decreases with more filtration or a grid, and is inversely related to SID, tissue thickness, and collimation. Contrast is maximized at an intermediate kVp and is highest with less collimation, no grid, and optimal kVp and mAs. Detail decreases with more motion, tissue thickness, focal spot size
2. Contrast and the 15% Rule
Objective: To
demonstrate the
influence of the 15%
rule on contrast
1st exposure at
recommended
technique
Used as control
3. Contrast and the 15% rule
Apply the 15% rule
twice and ↑ kVp ↓ mAs
accordingly
All other factors stay the
same
The math doesn’t quite
add up on this one, so I
think the images are from
2 different groups
4. Contrast and the 15% rule
Again, this image doesn’t
match my lab sheet, I
believe we lowered the kVp
15% and shot another on
just for S&G
At this point, we should
compare the 2 images to
determine which has the
longest scale of contrast
See next slide
5. Contrast and the 15% rule
Low kVp=High Contrast= Short scale High kVp=Low Contrast= Long scale
More B&W More Shades of Gray
6. Density- Control Image
Objective: To
demonstrate the effect
of select factors on
density
Control image of knee
phantom taken @
5mAs, 60kVp, & 40”
SID.
7. Density- Filter
With no change in tech
factors, a copper sheet
is taped to the face of
the collimator
Filters have an inverse
relationship on density
thus:
↑ Filtration ↓ Density
8. Density- Grid
Copper filter removed
No change in technical
factors
Grid is introduced to IR
Result: Adding a grid
decreases density this
is an inverse
relationship
(+) ↑ Grid ↓Density
9. Density- SID
Grid removed
No change in technical
factors
SID increased from 40”
to 60”
10. Density-Tissue Thickness
Grid is removed and hand
phantom is substituted for
knee
No change in technical
factors
Overall, the hand the tissue
thickness of the hand is
much less than that of the
knee
↑ tissue thickness ↓density
11. Density- Collimation-Control
Torso phantom is
substituted for hand
14x17 collimation
Use technique
recommended by
console + 20 mAs
This image will be
compared with the
highly collimated
image.
12. Density- Collimation
Collimation is
increased to a 4x4
square.
Repeat exposure of
torso with no change in
technical factors
↑collimation ↓density
13. Density- Anode Heel Effect
Use a foot phantom
and a 14x17 cassette
2 mAs, 60 kVp, 40” SID
Leave collimation open
lengthwise to 17”
Orient toes over the
anode side
14. Density- Anode Heel Effect
All technical factors remain the
same
Foot is moved to opposite end of
cassette to place toes on
cathode side
In practice, the thickest tissue
should be placed at the cathode
end of tube
In theory, placed thicker tissue at
anode end would effect density
A visible change in density would
only be appreciated with
film/screen
15. Size Distortion: Control
Objective: To
demonstrate the
various types of
distortion
Control image of hand
shot at 40” SID
Technique: Pre-
programmed
16. Size Distortion: 6” OID
2nd image
6” OID is created with
sponges
All other factors remain
the same
Compare with control
image to note distortion
(magnification)
17. Size Distortion: 12” OID
Image #3
OID is ↑ to 12”
Collimation is exactly the
same
No other factors have
been changed
Note magnified
appearance of hand
Such distortion can mask
pathology
18. Distortion: OID + SID
OID is ↓ to 6”
SID is ↓ to 20”
All remaining tech factors
are unchanged
Result: Size distortion
(magnification in this
case) can be caused by
OID, SID or both
19. Shape Distortion: Control
Control exposure of
knee phantom
w/recommended tech
factors
This image will be used
for comparison with
others
20. Shape Distortion: Angled Tube
2nd image of knee
phantom
Tube is angled
All tech factors remain
the same
21. Shape Distortion: Angled IR
3rd exposure of knee
phantom
IR is angled
All tech factors are
unchanged from
control
Note closed joint
spaces
22. Shape Distortion: Angled Anatomy
4th exposure of knee
phantom
All tech factors remain
constant except…
Phantom is angled
Result: Shape distortion
can be caused by the
angulation of tube, IR or
anatomy being imaged.
23. Density & mAs
Objective is to
demonstrate the effects
of overexposure &
underexposure on CR
images
First image is made @
60kVp, 10mAs w/40”
SID
24. Density & mAs 2
mAs is ↑ 50
All other technical factors
remain the same
LGM#’s of all images will be
compared with control
LGM represents the # of
photons reaching IR to form
the latent image
LGM is proportional to mAs
25. Density & mAs 3
↑ to 100 mAs
No other technical
factors are changed
At this stage, LGM#’s
appear to be ↑ as mAs is
↑ (a direct relationship).
26. Density & mAs 4
↑ to 200 mAs
Remaining tech factors
unchanged
LGM#’s increase with
each increase in mAs
mAs is THE controlling
factor of density
27. Detail and Distortion: Motion
Objective: To demonstrate
the effect of motion on
detail
Technical factors: The
programmed technique for
a foot but ↓ mA
Decrease in mA is necessary
to ↑ exposure time
(applicable in next image)
1st image of top taken on
10x12 w/no motion
28. Detail and Distortion: Motion
2nd image- top is
spinning while
exposure is taken
Technical factors are
unchanged
The lower mA ↑
exposure time, allowing
the motion to be caught
on film
29. Detail and Distortion: Motion
Additional image of this
experiment
Compared to the 1st image
(stationary), the lead letter
attached to top is blurred.
Result: Increased motion
decreases detail
Motion↑↓ Detail
Although motion is generally a
detriment to good films, it can be
used to the RT’s advantage
Ex: Using breathing technique to
blur ribs
30. Quantum Mottle
Definition: a lack of
sufficient incoming data
to process an image;
AKA quantum noise
No idea what this
image has to do with
anything, but that’s
how it was labeled
That would be a cool
name for a band
though
31. Contrast- Control Image
Objective: To
demonstrate how
selected factors effect
contrast
66kVp, 10 mAs, 40”
SID on table top
32. Contrast 66kv
Skull phantom is
replaced w/step wedge
Exposure taken with no
changes in technical
factors
Compare this image
w/second exposure
using a higher
technique
33. Contrast: ↑kVp ↓mAs
↑ to 86kVp
Compensate by ↓mAs to
¼ of its original value
All other factors remain
the same
34. Contrast- 86kv
Again, step wedge
takes the place of skull
phantom
No change in technical
factors
Compare shades of
gray in adjacent
densities
36. Contrast: +Grid
3rd image of skull
Grid is introduced
mAs ↑ 4x to
compensate
All remaining factors
unchanged
37. Contrast: Scatter
4th image of skull
Collimation open wide
to expose IR to scatter
All remaining factors
unchanged
Compare this series of
images to note
differences in adjacent
densities
38. Contrast Collimation
Skull is now positioned
laterally
This exposure will use
bucky instead of table
top
100 kVp @ 20mAs
39. Contrast: Collimation
Repeat exposure of
lateral skull
Collimated to 3”x3”
area
All remaining factors
are unchanged
40. Short vs Long Scale Contrast: kVp
Objective: To
demonstrate short &
long scale contrast
Elbow phantom @
46kVp & 5mAs
41. Stepwedge 2 Contrast ????
I think this is supposed
to be part of a contrast
lab but I couldn’t match
it up with anything
Also, it was posted
twice in the images
file…so there’s nothing
to compare it to as far
as I can tell
42. Short vs Long Scale Contrast; kVp
2nd image of elbow
phantom
↑ to 70kVp
↓to 3mAs
43. Density Chart
Variables Effects Density Relationship
↑↓ ↓↑
Filtration Inverse
↑↓ ↓↑
Grid Inverse
↑↓ ↓↑
Tissue Thickness Inverse
↑↓ ↓↑
SID Inverse
↑↓ ↓↑
Collimation Inverse
Cathode: ↑
Anode Heel Effect *In theory the N/A unless film
Anode: ↓ anode heel effect screen technology
does cause a is involved
change in density
but this is not
evident in digital
imaging
44. Contrast Chart
Variable Effect Contrast Relationship
↑↓ ↓↑
kVp inverse
Ø Ø
mAs none
Ø Ø
SID none
↑↓ ↑↓
OID direct
↑↓ ↓↑
Filtration inverse
↑↓ ↑↓
Collimation direct
↑↓ ↓↑
Tissue Thickness inverse
↑
Contrast Media + direct
↑↓ ↑↓
Grid ratio direct
Ø Ø
Focal spot size none
↓ Always ↓ contrast
Film Processing *+/- developing
time and temp
beyond optimal