Chapter 10 concepts of radioGraphic quality
what are the radiographic quality rules
1. fast IRs have high noise and low spatial resolution and low contrast 2. high spatial resolution and high contrast resolution require low noise and slow IRs 3. low noise accompanies slow IRs with high spatial resolution and high contrast resolution
what are some principles to be considered when planning a particular examination
1. use of intensifying screens decreases patient dose by a factor of at least 20 2. as the speed of the IR increases radiographic noise increases and spatial resolution is reduced 3. low contrast imaging procedures have wider latitude or margin of error in producing an acceptable radiograph
Accuracy in positioning the patient is most critical with which of the following ?
APR/ Automatic exposure
Magnification
All images on the radiograph are larger than objects they represent
Foreshortened
An example of gross distortion shows that the image of an inclined object can be smaller than the object itself
Before a radiographic technique chart is prepared which if the following would be most important
Calibrating the xray imaging system
Which of the following is necessary to construct a characteristic curve?
Densitometer
Subject contrast
Determined by the size shape and xray attenuating characteristics of the anatomy that is being examined and the kVp of the xray beam
Which of the following technique charts requires accurate measurement
Fixed , high, and variable kilovoltage ,
Which of the following technique charts provides the least amt of patient radiation exposure?
High kilovoltage
Which of the following will increase exposure latitude ?
High kilovoltage chart
A longer grayscale on a radiograph can be obtained by doing which of the following ?
Increasing kVp
Image receptor contrast
Inherent in the screen film combo and is influenced somewhat by processing of the film
Penetration of the anatomic part by the xray beam can best be controlled by which of the following ?
Kvp
Which of the following anatomic structures should exhibit the greatest subject contrast with muscle ?
LUNG
The optical density present on the radiograph can be best controlled by which of the following ?
MAs
When fixed kVp tech is used for various anatomic thickness, a change will be required in which of the following ?
MAs
A radiograph that exhibits a long grayscale contrast has which if the following features ?
Many shades of gray that have minimal diff
image magnification increases with increasing ?
OID
the magnification factor increases with increasing ?
OID
Which of the following procedures would make best use if high kilovoltage chart
Pelvis
increasing which of the following is effective in reducing FSB
SID
the magnification factor is dependent on what?
SID
which of the following geometric factors affect radiographic quality ?
SID
Which of the following is a basic characteristic of variable kilovoltage chart
Short scale of contrast
Structure mottle
Similar to film graininess but refers to the phosphor of the radiographic intensifying screen
Quantum mottle
Somewhat under the control of the radiologic tech and is a principal contributor to radiographic noise in many radiographic imaging procedures
Base density
The OD that is inherent in the base of the film
Contrast resolution
The ability to distinguish anatomical structures of similar subject contrast such as liver-spleen and gray matter-white matter
Resolution
The ability to image 2 separate objects and visually distinguish one from the other
Spatial resolution
The ability to image small objects that have high subject contrast such as bone -soft tissue interface a breast microcalcification
Visibility of detail
The ability to visualize recorded detail when image contrast and OD are optimized
Radiographic contrast
The contrast of a radiograph viewed on an illuminator
Fog density
The development of silver grains that contain no useful information
Film graininess
The distribution in size and space of silver halide grains in the emulsion
Radiographic Noise
The random fluctuation in the OD of the image
Straight line portion
The region in which a properly exposed radiograph appears
Characteristic curve
The relationship btw OD and radiation exposure
The anatomic part to be examined must be measured bc
The selected radiograph tech depends on anatomy thickness
Sensitometry
The study of the relationship btw the intensity of exposure of the film and the blackness after processing
Which of the following is the function of optimizing contrast
To make detail visible
Distortion
Unequal magnification of different portions of the same object
Which of the following technique charts requires higher patient radiation dose
Variable kilovoltage
a foreshortened image results from what?
an inclined object
When radiographic technique factors are adjusted to provide an acceptable image and then filtration is added to the xray tube which of the following will increase ?
avg energy of the xray beam
unexposed but processed film may appear cloudy and dull bc of which of the following ?
base density
Distortion primarily occurs ?
bc subject anatomy is inclined
which of the following is the principal reason for using direct-exposure radiography
better spatial resolution
ensuring good screen film contact also ensures reduced
blur
How can distortion be corrected ?
by proper patient positioning
what factors may affect the finished radiograph
concentration of processing chems, degree of chemistry agitation during development , development time and temp
use of contrast media principally affects which of the following
contrast resolution
reducing field size through proper collimation usually results in improved
contrast resolution ; patient dose
spatial resolution improves as screen blur
decreases , motion blur decreases and geometric blur decreases
if the object plane and the image plane are not parallel
distortion occurs
geometric blur is controlled principally by which imaging system characteristic?
focal spot size
spatial resolution is principally affected by which of the follwoing
focal spot size
which of the following is most responsible for radiographic spatial resolution ?
focal-spot size
as the time of film development is increased beyond the manufactures recommendations what happens ?
fog increases
which of the following is most often influenced by focal spot size ?
geometric blur
Which of the following radiographic techniques should result in the widest exposure latitude?
high kvp ,latitude film,low grid ratio
focal spot blur is the most
important factor for determining spatial resolution
When proper radiographic detail cant be obtained bc of a large OID what change in technique may be used to improve the detail ?
increase SID
magnification is reduced by which of the following
increasing SID and reducing OID
latitude and contrast are
inversely proportional
the primary control of radiographic contrast is
kvp
which of the following does not affect image blur?
kvp
when one images an object lateral to the central axis of the xray beam the FSB will be
larger on the cathode side
the primary control of OD is
mAs
Distortion of an xray image results from unequal?
magnification
what are the 3 geometric factors
magnification , distortion , focal-spot blur
patient motion is usually the cause of
motion blur
Abortion blur is most clearly related to which of the following?
object shape
which factor most often reduces the visualization of low contrast structures on a properly exposed radiograph ?
patient motion
another term for FSB is
penumbra
When the focal spot is switched from large to small
penumbra will be reduced
Subject contrast is enhanced with the use of contrast media bc
photoelectric interaction is increased
focal spot blur occurs bc the focal spot is not a
point
to obtain minimum magnification one should of which of the following ?
position the anatomy close to the IR
to minimize magnification one should do which of the following ?
position the object as close to the ir as practical
in mammo which of the following conditions would be most effective in improving the sharpness of detail of microcalcifications near the chest wall?
positioning the anode on the same side as the chest wall
which of the following will reduce motion blur?
proper patient instructions
The use of high-mas , low kvp and of slower IRs reduces
quantum mottle
which of the following is the main component of radiographic noise?
quantum mottle
to reduce magnification one should do which of the following?
reduce OID
FSB can be reduced by
reducing OID
sharpness of detail on a radiograph is principally improved by which of the following ?
reducing patient motion
film contrast is
related to the slope of the straight line portion of the characteristic curve
a radiograph that shows a relative lack of FSB would be ?
sharp in detail
we need to exposure time as
short as possible
extremity xray exam results in which of the following
short scale contrast
the focal spot blur is small on the anode side and large on the cathode
side of the image
radiographic spatial resolution is improved by the use of which of the following ?
slower radiographic intensifying screens
the best way to minimize FSB w/out affecting optical density is to use a very what?
small focal spot
the sharpness of detail in a radiographic is best increased by the use of which of the following ?
small focal spot
image contrast is the product of IR contrast and
subject contrast
kvp is the most important influence on
subject contrast
when an object is present to one side of the central axis of the xray beam what remains unchanged?
subject contrast and magnification factor
higher fog density reduces
the contrast of the radiographic image
base density refers to which of the following ?
the optical density of the base
the principal cause of motion blur mvmt of which of the following ?
the patient
The diagnostically useful portion of a characteristic curve most often includes which of the following ?
the straight- line portion
thick objects are more distorted than
thin objects
to improve bony detail in a radiograph , the radiologic technologist could do which of the following ?
use a smaller focal spot
Focal spot blur can be reduced by which of the following
using the small focal spot
