Flashcards in Ch 10 Radiographic Quality Deck (71):
What is radiographic quality?
The exactness of representation of the anatomic part of interest in the finished radiograph
What are the (3) types of radiographic quality factors?
1. Film factors (not allot of control over)
2. Geometric factors (little bit of control over)
3. Subject factors (no control over)
What quality factor do we have no control over?
What are the film factors?
What are the Geometric Factors?
What are the Subject Factors?
Quality is the same for everyone? T/F
What is the criteria for evaluating quality?
What is spatial resolution?
Everything is in it's appropriate place
What is contrast resolution?
Scales of gray
Spatial resolution is the ability to image objects that have ____ subject contrast.
Contrast resolution is the ability to detract or distinguish objects that have _____ subject contrast.
Which modality best demonstrates spatial resolution?
What is noise?
The undesirable fluctuation of the OD of the image
Which modality best demonstrates contrast resolution?
How do we get noise on an image?
-Structure mottle- phosphor intensity screen
-Scatter Radiation-impact OD
What is Quantum Mottle?
What is the quality rule?
Fast image receptors have high noise and low spatial & contrast resolution
What is another name for the D max?
What is the Characteristic curve?
The graphic relationship between optical density and radiation exposure
What are the two pieces needed to contract a characteristic curve?
What is the highest portion of the Characteristic curve?
Shoulder (D max)
What is the lowest portion of the Characteristic curve?
What is another name for the Characteristic curve?
H & D curve
What is the most useful part of the characteristic curve?
Straight line portion
Is D max useful?
-No, it's black
Is the Toe useful?
No, too white
-Loss of density
Where do you find your grays on the Characteristic curve?
In the straight line portion
What is the portion below the toe called?
Base + Fog (B+F)
What is B+F?
-What is inherent in the film and hasn't been exposed
-Anything outside the range of exposure
In B+F, what is Base?
What the manufacturer put in the film
In B+F, what is F?
Fog in the dark room
What is optical density?
Measurement of light incident on a processed film and the level of light transmitted through the film
What chemical produces the black?
What chemical produces the shades of gray?
Base + Fog= ?
Base + Fog should not exceed...
B + F (below toe) falls ______ the exposure range.
What is the OD range of the unexposed and processed radiographic films?
Hydroqonone and phenedone work _______ to produce the blacks and grays.
Optical density is looking at what's _____ and what passes through
B+F is the _______ and processed part of the processed radiographic film.
What is the base density?
What is the Fog density?
Doesn't exceed 0.2
What is the useful range of optical density?
0.25- 2.5 LRE
What are some reasons you might get an OD greater than 0.3?
-Aging of the film
What does LRE stand for?
Log Relative Exposure
What are the OD ranges dependent on?
-Shape of characteristic curve
Optical density is measured ________.
What are the (2) types of Radiographic Contrast?
1. Image receptor contrast
2. Subject contrast
What is Image Receptor Contrast?
Inherent in the film and influenced by processing
(Things we cannot control)
What is Subject Contrast?
That which attenuates through our patient and the kVp we performed the image with
(other than kVp we cannot control)
How do we have any control over radiographic contrast, when it's determined by things we have no control over?
For the same film type a change in _____ will affect contrast only when above or below the straight line portion.
Contrast is defined by the slope of the ______ _____ portion.
When density impacts _____ it is above or below the straight line portion
Contrast that is defined by the slope of the straight line portion is also know as...
When changing technique at the D max...
Cut mAs in half
When changing technique at the toe you...
What is the Average Gradient?
The slope of the straight line drawn between two points on the characteristic curve at 0.25 and 2.0 above B+ F
What is the useful range of average gradient?
The B+ F should not exceed...
What are the average gradient constants?
What is the B+ F range?
When connecting (2) points on an H & D curve, the line is called the...
-Straight line portion
What is the formula to determine Average Gradient?
AG= OD2 - OD1
LRE 2 – LRE 1
The speed point on a film is defined as:
B + F+1
How do you chart a speed point?
As an open circle
When looking at a speed chart, the faster film is usually on the ____.
-It has a shorter scale of contrast
-Goes from white to black faster
Speed point is ___ point above B + F.