Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
101 Cards in this Set
- Front
- Back
|
What are the 4 Radiographic Image Properties?
|
1. Density
2. Contrast 3. Resolution 4. Distortion |
|
|
Define DENSITY.
|
The overall degree of BLACKNESS on the film.
|
|
|
The overall degree of BLACKNESS on the film is the definition of what radiographic image property?
|
Density
|
|
|
If the density is too low, how does the film look?
|
underexposed, thus very light and white
|
|
|
if there is high density, how does the film look?
|
it is overexposed and appears darker.
|
|
|
what property of a radiographic image allows one to say "this film is too light or that one is too dark?"
|
Density
|
|
|
what are the 2 primary controlling factors for DENSITY?
|
Miliamperage (mA) and Exposure Time (sec)
|
|
|
Miliamperage (mA) and Exposure Time (sec) are primary controlling factors for what radiographic property?
|
DENSITY
|
|
|
What is the equation for Total Exposure?
|
mA x sec = mAs = Total exposure
aka miliamperage times sec = total exposure |
|
|
mA x sec = ?
|
Total Exposure
|
|
|
as long as mAs is equal, what else will also be equal?
|
density
|
|
|
T/F: as long as mAs (= miliamerage x exposure time) is equal, film density will also be equal.
|
T
|
|
|
Ideal Exposure is what exposure time?
|
0.5 sec
|
|
|
1/2 of ideal exposure is what exposure time?
|
0.25 sec
|
|
|
What does LATITUDE describe?
|
The Range of exposures that make a suitable radiograph.
|
|
|
The Range of exposures that make a suitable radiograph describes what concept?
|
Latitude
|
|
|
how is density effected by kilovoltage?
|
increases with kVp
|
|
|
how is density effected by object size?
|
decreased with thickness. if you go through something really THICK it will turn out pretty white = radiopaque
|
|
|
how is density effected by developing time?
|
increases with time
|
|
|
how is density effected by developing temperature?
|
increases with temperature.
|
|
|
how is density effected by fixing time?
|
decreases with overFixing
|
|
|
how is density effected by TFD (tube film distance)?
|
decreased with TFD
|
|
|
how is density effected by film?
|
increases with speed
|
|
|
how is density effected by screens?
|
increases vs. non-screen
|
|
|
how is density effected by PSP scanner settings?
|
mathematical adjustment
|
|
|
name some other factors that influence density:
|
kilovoltage, object size, developing time, developing temperature, fixing time, tube-film distance (TFD), film screens, PSP scanner settings
|
|
|
CONTRAST is defined as?
|
The difference in densities btwn adjacent areas of a radiograph or The range of densities from white to black.
|
|
|
The difference in densities btwn adjacent areas of a radiograph is the definition of what property?
|
CONTRAST
|
|
|
The range of densities from white to black is a definition of what property?
|
contrast
|
|
|
what is the primary controlling factor for CONTRAST?
|
kVp (kilovoltage peak)
|
|
|
why is kVp the controlling factor for contrast?
|
bc an x-ray beam with HIGH ENERGY (kVp) penetrates all tissues more evenly, giving LESS CONTRAST.
|
|
|
what specialty LOVES high kVp? (less contrast)
|
periodontists. low contrast = little steps of contrast.
|
|
|
is High contrast is associated with short or long scale?
|
high contrast = short scale
|
|
|
Long scale is associated with what type of contrast?
|
low contrast = long scale
|
|
|
Detecting caries is easier with what type of contrast?
|
High contrast = short scale
|
|
|
T/F: Low Contrast = High kVp = Long scale contrast = Periodontists preferred.
|
T
|
|
|
T/F: High Contrast = Low kVp = Short scale contrast = good for detecting Caries
|
T
|
|
|
Overall GRAYNESS or Dull film quality is due to what qualities?
|
High kVp, long scale, low contrast
|
|
|
Overal CRISPNESS or Bright Quality to film is due to what quality?
|
Low kVp, short scale, high contrast
|
|
|
What scale has MANY shades of gray?
|
Long scale (high kVp, low contrast)
|
|
|
small differences exist btwn steps describes what type of contrast?
|
LOW contrast (long scale, high kVp)
|
|
|
what type of kVp produces low contrast bc all thicknesses are penetrated more EVENLY due to the high engery of xrays?
|
High kVp
|
|
|
HIGH CONTRAST has smaller or larger differences existing btwn steps?
|
Larger differences
|
|
|
Does high contrast of more or fewer shades of gray? and what type of scale is this?
|
fewer, short scale
|
|
|
T/F: a LOW kVp produces High Contrast bc the thicker steps stop all of the lower penetrating xrays produced by the lower energy
|
T
|
|
|
70 kVp is ideal. T/F
|
T
|
|
|
50 kVp is High contrast. T/F
|
T
|
|
|
90 kVp is High contrast. T/F
|
F. Low contrast
|
|
|
what is the purpose of CONTRAST?
|
to bring out DETAIL
|
|
|
HIGH contrast = better caries detection. T/F?
|
T
|
|
|
T/F: high contrast better for caries detection. low contrast better for perio desiease (bone loss) eval.
|
T
|
|
|
Fog affects contrast. T/F
|
T
|
|
|
how is contrast improved?
|
by the elimiation of FOG
|
|
|
eliminating FOG improves what?
|
contrast
|
|
|
the standard diameter xray beam to decrease FOG is what?
|
2.75 inch
|
|
|
compton scatter causes FOG. t/f
|
T
|
|
|
how do you eliminate compton scatter?
|
metal grids or make the beam very small.
|
|
|
for NBDE, what is the diamter of the beam to decrease FOG?
|
2.75 inch diameter
|
|
|
RESOLUTION is defined as what?
|
the ability to distinguish btwn 2 closely spaced points.
|
|
|
the ability to distinguish btwn 2 closely spaced points defines what?
|
resolution
|
|
|
what are the primary controlling factors of Resolution (the geometric ones)?
|
1. focal spot size
2. object film distance (OFD) 3. tube film distance (TFD) |
|
|
what are the primary controlling factors of resolution (the non-geometric one)?
|
1. film grain size
2. patient/tube/film motion |
|
|
strip + space =
|
line pair
|
|
|
measurement of resolution can be done by using resolution plate which is constrcuted of alternating lead strips and what?
|
adjacent spaces of equal width
|
|
|
what are the units of resolution?
|
line pairs/ milimeter
|
|
|
the human eye can only resolve ______ unmagnified in ideal situations.
|
8-10 line pairs/mm
|
|
|
PSP plates provide 7 line pairs which when magnified creates a building block pattern or pixelated appearance which demonstrates the limits of the imaging system. T/F
|
T
|
|
|
the D-speed intraoral film is how many lp?
|
15 line pairs/ mm
|
|
|
digital radiography image receptor is how many lp?
|
10 line pairs/ mm
|
|
|
the pan/ceph film (used with screens) is how many lp?
|
2 line pair / mm
|
|
|
what is PENUMBRA?
|
the area of UNSHARPNESS in the projected shadow of an object
|
|
|
the area of UNSHARPNESS in the projected shadow of an object is defined as what?
|
PENUMBRA
|
|
|
T/F if you have a LARGE focal spot will your penumbra be more or less?
|
more
|
|
|
a small focal spot = less penumbra. t/f
|
t
|
|
|
a 16 inch TFD is known as the Long cone technique. and creates large penumbra. t/f
|
f. 16 inch TFD is the long cone technique but it creates small penumbra
|
|
|
what can create a large penumbra?
|
8 inch TFD = short cone technique or increased OFD (paralelling technique)
|
|
|
decreased OFD (bisecting technqiue) creates what size of penumbra?
|
small
|
|
|
E speed film = faster speed, larger crystals, less radiation to expose. t/f?
|
t
|
|
|
faster speed, larger crystals, less radiation to expose describes what type of film?
|
E Speed film
|
|
|
D speed film = slower speed, smaller crystals, more radiation to expose. t/f?
|
t
|
|
|
slower speed, smaller crystals, more radiation to expose describes what type of film speed?
|
D speed film
|
|
|
t/f: points of information are dispersed more widely by the fluorescence of the intesifying screen crystals, resulting in unsharpness.
|
t
|
|
|
film is exposed by both radiation (xray) and visible and UV light (fluorescence) t/f
|
t
|
|
|
miscellaneous factors affecting resolution include ?
|
patient motion (blurring), film movement (blurring), xray tube motion (increase the effective focal spot size & thus penumbra)
|
|
|
who invented the PARALELLING technique, the breaksystem in the elevator and killed himself later?
|
KELLS
|
|
|
Distortion describes what?
|
The image should be the same size and shape as the object
|
|
|
size distortion = what?
|
magnification
|
|
|
size distortion = magnification. t/f
|
t
|
|
|
shape distortion = distortion. t/f
|
t
|
|
|
what are the primary controlling factors of magnification? (they also control sharpness)
|
geometric factors: 1. OFD
2. TFD |
|
|
if image size is larger than object this =
|
magnification
|
|
|
if you have a SMALL OFD what type of magnification will you get?
|
less
|
|
|
less magnification results from smaller ofd. t/f
|
t
|
|
|
greater magnification results from what type of OFD?
|
larger ofd
|
|
|
long TFD results in what type of magnification
|
reduced magnification
|
|
|
short TFD results in what type of magnification?
|
increased magnification
|
|
|
increased magnification results from what type of TFD?
|
short Tube film distance and LARGE object film distance
|
|
|
distortion is controlled by what primary factors?
|
angular relationship btwn :
TEETH FILM BEAM |
|
|
elongation distortion occurs when?
|
insufficient beam angulation. image is LONGER than objectF
|
|
|
FORESHORTENING distortion occurs when?
|
when there is excessive beam angulation. image is SHORTER than object
|
|
|
the 4 image properties of radiographs are?
|
DENSITY
CONTRAST RESOLUTION DISTORTION |
