radiographic image quality Flashcards
• It refers to the fidelity with which the anatomical structure that is being examined is rendered on the radiograph.
• Il is the exaciness of representation of the patient’s anatomy on a radiographic image.
RADIOGRAPHIC IMAGE QUALITY
Il is the ability to image small objects that have high subject contrast
SPATIAL RESOLUTION
abilly to distinguish analomical structures of similar subject contrast
CONTRAST RESOLUTION
random
Ructuation in the
OD of the image.
RADIOGRAPHIC NOISE
Unintended
optical density on a radiograph or
another fim-lype image receptor
ARTIFACT
Spatial resolution is measured by using a
_______
Line - pair Test pattern
spatial resolution is expressed by the number of _____ that are imaged.
line pairs per millimeter (ip/mm)
lead lines separated by equal size with equal interspaces
line-pair test
more line pairs, smaller object can be imaged
higher spatial resolution
very fast screen
7 lp/mm
fine detail screen
15 lp/mm
direct
50 lp/mm
naked eye
10 lp/mm
components of radiographic noise
film graininess
structure motile
quantum motile - random nature by which xrays interact w IR. can be controlled by a radiographer. only few xrays can reach IR
scattered radiation - primary source of radiographic noise. high kvp. low energy xrays
recorded detail
degree of sharpness
ability of intensifying screens to produce light
speed
have high noise and low spatial resolution and low contrast resolution
fast image receptors
High spolial rescution and high contrast resolution require
low noise and slow imoge receptors
film factors
density
contrast
speed
latitude
density
primary control of OD is
mAs
degree of blackening on the radiograph
optical density
IR contrast and subject contrast
primary control is kVp
radigraphic contrast
refers to the range of exposures over which the IR responds with OD in the diagnostically useful range.
latitude
wide latitude
long scale contrast - mababa contrast
narrow latitude
short scale contrast - mataas contrast
time and temperature
processing
geometric factors
distortion
magnification
blur
is the misinterpretation in the image of the actual spatial relationships among objects.
spatial distortion
Unequal magnification of different portions olfthe same object is
shape distortion
distortion depends on
object thickness
object position
object shape
Al images on the radiograph are larger than the objecis they represent, a condition called
magnification
MF = magnification factor
IS/OF or SID/SOD
subject factors
thickness
density
atomic number
motion
When the effective atomic number of adjacent tissues is very much different, subject contrast is
very high
bone effective atomic number
13.8
muscle effective atomic number
7.4
lungs effective atomic number
7.4
fat
6.3
