Mastering that Darn Chart Flashcards
mAs effects:
Receptor Exposure
The amount of radiation striking the image receptor
Receptor Exposure
If you are using a Fugi machine the exposure number is called:
The S number
(the higher the number the less exposed the image is, the lower the number the less exposed it is)
The EI for Fugi:
200
The Kodak EI number is:
2000
(the higher the number the more exposed it is, the less the number is less exposed it is)
Deviation Index
2.5
The differences between adjacent brightnesses.
Contrast
The function of contrast is to:
make the details visible
If you have an image and its high contrast with black and white and there is a tumor that is gray. Would you be able to see that tumor?
No, go up in technique
120 kVp do you have the right contrast for a rib study?
No, burning through
The sum of the inherent filtration plus the added filtration=
Total Filtration
Receptor contrast plus subject contrast=
total contrast
The receptor contrast plus the subject contrast=
Contrast
The fixed characteristic of the receptor
Receptor contrast
The magnitude of the signal in the remnant beam as a result of different absorption characteristics in the tissues and structures that make up that part
Subject Contrast
Mathematical codes by the software to provide the desired physical appearance
Processing algorithm
The LUT controls the:
contrast and the brightness
How does the kVp effect spatial resoltion?
NO EFFECT
How does kVp effect focal spot size?
NO EFFECT
Where is the focal spot?
The area on the target that is being bombarded by electrons
How do you control involuntary motion?
Short Exposure Time
How do you control voluntary motion?
Communicate with the patient
When something does not have good spatial resolution it is:
Blurry
Misrepresentation of size and shape
Distortion
A 4 inch round tumor 8 inch:
Size distortion
If you are x-raying a tumor and make it oval:
Shape distortion
Size distortion effects:
OID and SID
For the least amount of magnification what kind of OID do you want?
short
For the least amount of magnification do you want a short SID or long SID?
Long
For the least amount of magnification what is better 40 inch or 72 inches?
180 cm or 72 inches
If you made it at 40 inches to 80 inches SID how much more radiation would you have to use?
4xs more radiation
Shape distortion:
IR, placement of IR, and body part being perpendicular
The one thing that causes foreshortening is the:
If the body part is not parallel to the IR
Angling the tube causes
elongation
Angling the tube would cause:
elongation
Photographic properties of the radiograph:
receptor exposure and contrast
Geometric Properties of the radiograph:
Spatial resolution and distortion
Image Quality
The balance of the photographic and image quallities
When mAs is increased:
receptor exposure increases only
Double the mAs:
Double the receptor exposure
Increasing kVp:
increases receptor exposure
decreases contrast (more the k’s the more the grays)
If the OID is increased to have an air gap
decreases receptor exposure
(functioning like a grid)
If OID is increases for an air gap, what happens to contrast?
increases contrast
When OID increases spatial resolution:
decreases
When OID increases:
distortion increases
SID increases
receptor exposure decreases
Increase SID, contrast
No effect
As SID increases, spatial resolution
increases
As SID increases, distortion
decreases
Focal Spot Size effects:
spatial resolution
motion effects
spatial resolution
100 mA small focal spot, 100 mA large focal spot:
Increase Spatial resolution only
If small focal spot provides better spatial resolution than why do we not use small focal spot on everything?
Will not fit on the area of the focal spot with high mA
APR does:
whether you can use small or large focal spot
The grid ratio:
5:1 BF: 2
10:1
12:1
16:1
If you go to table top to a 5:1 grid:
the receptor exposure decreases
As grid ratio increases the contrast:
increases
As tube filtration increases what happens to receptor exposure?
Decreases
Increase tube filtration:
Decreases contrast
If you are exposing a 14 x 17 area and you drop down to a 10 x 17 what happens to receptor exposure?
decreases
If you increase beam restriction what happens to contrast?
increases
As a result of angling the anode there is an uneven distribution of radiation as it leaves the tube
Anode Heel Effect
Increase Anode Heel Effect
increase receptor exposure
Which has a low contrast?
Does A have more contrast or less contrast?
Which has a shorter scale of contrast?
Which has high kVp?
Which has a short wavelength?
B. high kVp, more grays, less contrast
A. more contrast, low kVp,
Which has a low contrast? B
A has more contrast
Which has a shorter scale? A
Which has more kVp? B
Which has a short wavelength? B
Which one is high contrast?
C
A
Low contrast
Long-scale
Something with high contrast:
the whites are whiter
the blacks are blacker
Which side is less and which side is more?
Left side less
right side more
Caliper
Used if the body part is more than 10 cm (grids are used)
Between 19-24 cm
NO central ray angle
More than 24 cm from ASIS to to table top angle:
3-7 degrees cephalic
Below 19 cm:
3-7 degrees caudad
How will increasing the focal spot size effect the spatial resolution of a radiograph?
Decrease Spatial Resolution
Right: PA
Left: AP
Erect
Horizontal Air Fluid Levels
What is the difference between the two?
A. High Contrast, Short-Scale, Low kVp, Long wavelength, more contrast
B. Long Scale, Low Contrast, High kVp, Short wavelength, less contrast
B. high contrast
Both have the same receptor exposure
OVEREXPOSURE
Focus Grid Upside Down
4 causes of grid cut off:
Off level
Off center
Upside Down Focus Grid
Off Focus
No Grid:
5:1 Grid:
8:1 Grid:
12:1 Grid:
16:1 Grid:
1
2
3
4
5
6
always collimate to the IR and not the patient
Total Filtration has to be:
2.5
Inherent:
.5 mm Al
Added Filtration:
2 mm Al
A. regular bone
B. foreshortened, part not parallel
C. elongated
A.
B.
C.
A. Accurate
B.
Filter was half in and half out
below the the tube, above the collimator
