Ch 10 Radiographic Quality II Flashcards
What is film speed affected by?
- Immersion time
- Temperature
- Chemical activity
The longer the film stays in the chemical bath, the _______ the line becomes.
Straighter
If you increase your speed, what happens to your mAs?
It goes down
Speed and mAs are _______ proportional.
Inversely
A wide latitude, would have ____ shades of gray.
Many
A narrow latitude, would have a ______ scale of contrast
Short
Latitude and contrast are _______ proportional.
Inversely
What is Latitude?
Range of exposures that will produce densities within the diagnostic range
What is the formula for Latitude?
Latitude= E h - E I
E h=
High exposure point OD 2.50
E l=
Low exposure point OD 0.25
A narrow latitude film requires ______ exposure accuracy and produces short gray scales.
Greater
The _______ amount of magnification should be maintained.
Smallest
What is the ratio of image size to object size?
Magnification
Some magnification will _____ exist.
40”-?
72”-?
Always
40”- 1.1
72”- 1.05
What is SOD?
Source to object distance
What is OID?
Object to image distance
What is the acceptable magnification range?
?
How many cm are in an inch?
2.5
What are the (2) factors that effect image magnification?
- SID
2. OID
What is distortion?
Unequal magnification of different portions of the same object
Distortion is dependent on…
- Thickness of object/ part
- Position
- Shape of the object
The thicker the object the _____ distortion present on the final radiograph.
More
We must compensate for object unsharpness with factors we can control, such as:
- Focal spot size
- SID
- OID
Fine detail=
Small focal spot
Smaller x-ray beam width will produce a _____ image.
Sharper
General radiology uses _____ focal spot
Large
The larger the focal spot the more ____ you get.
Penumbra
What is Penumbra?
Fuzzy border that appears outside the image
The greater the distance between tube and the cassette, the greater the image…
Sharpness
To reduce penumbra, use the _____ amount of SID.
Maximum
The closer the object to the film, the _____ the detail.
Sharper
When OID goes down, penumbra goes down and sharpness goes ____.
Up
When OID goes up, penumbra goes up and sharpness goes ____.
Down
Penumbra and Sharpness are _______ relational.
Inversely
Objects not on the central axis appear ______.
Distorted
If the object plane and the image plane are not parallel, image _______ will appear.
Distortion
What is Foreshortening?
Image size is reduced as the angle on inclination along the central axis increases
What is elongation?
The image size is lengthened as the inclination is increased
What is shape distortion?
The misrepresentation by unequal magnification of the actual shape of the structure being examined
The farther away the part of interest is from the CR of the image receptor, the greater the ______.
Distortion
What is focal spot blur?
Focal spot is not a point, but rather a rectangular source (0.1- 1.5mm)
What is the most important factor in determining resolution?
Focal spot blur
What is focal spot blur caused by?
- Large effective focal spot
- Short SID
- Long OID
What side of the tube is focal spot blur the greatest?
The cathode side
How do you minimize focal spot blur?
- Use small focal spots
- Decrease OID
- Increase SID
The difference between SID and OID =
SOD
Can you control subject factors?
No
