Depends on the method of image
acquisition and the variables to produce
the image.
★ Determines how clear, accurate, and
diagnostically useful an image is.
IMAGE QUALITY
Factors that affect image quality are:
- Contrast
- Blur (Detail)
- Noise
- Distortion
- Artifacts
Fundamental characteristic of
an image.
The difference in densities
(brightness levels) between a structure or object and its
surrounding area.
Physical contrast represents
differences in tissue
composition.
Contrast
sharp
differences (black & white
image, e.g., bone vs. lung
High Contrast
subtle
differences (grayscale image,
e.g., soft tissue imaging).
Low Contrast
Detail is determined by the
small anatomical features that
can be seen in the image.
Visibility of detail is limited due
to the imaging method.
Causes:
a. Motion (patient or tube)
b. Limitations of the
imaging system (pixel
size, resolution)
c. Focal spot size
d. Inherent property in
digital imaging
blur
blur
Detail is determined by the
small anatomical features that
can be seen in the image.
Visibility of detail is limited due
to the imaging method.
Causes:
a. Motion (patient or tube)
b. Limitations of the
imaging system (pixel
size, resolution)
c. Focal spot size
d. Inherent property in
digital imaging
It appears as grainy or textured
appearance on the image.
The amount of image noise
depends on the imaging
method.
Also referred to as image
mottle.
Always balance exposure: too
low ➜ noise, too high ➜
overexposed.
Image Noise
Also referred to as image
mottle.
Image Noise
Always balance exposure: too
low ➜__, too high ➜
___.
noise, overexposed
Change in size or shape of the
resultant image from the
original.
1. Magnification ➜ Size
distortion: Achieved by
increasing the distance
of the object from the
image receptor or
decreasing the distance
of the the image
receptor.
2. Elongation or
Foreshortening ➜ Shape
distortion: Caused by
improper angulation of
the X-ray beam, part, or
receptor.
As OID increases, size distortion
(magnification) increases; as OID
decreases, size distortion
(magnification) decreases
Distortion
Distortion
two types
magnification, elongation or foreshortening
Achieved by
increasing the distance
of the object from the
image receptor or
decreasing the distance
of the the image
receptor.
Magnification ➜ Size
distortion:
Caused by
improper angulation of
the X-ray beam, part, or
receptor.
Elongation or
Foreshortening ➜ Shape
distortion:
As OID increases, size distortion
(magnification)
increases
as OID
decreases, size distortion
(magnification)
decreases
Unwanted or misleading marks
or patterns appearing on a
radiographic image that are not
part of the actual anatomy.
Artifacts
A shadow of the pelvis is seen on the chest
x-ray above
★ Two exposures on the same
imaging plate. Results in
superimposed images
★ Always erase or reset image
plate before reuse.
Double Exposure
Grainy appearance caused by
insufficient X-ray photons reaching the
detector.
Quantum Mottle
wavy, crisscross pattern seen when
grids with low grid frequency interact
with the pixel matrix of the detector.
Moiré Pattern
Appear as white or black spots/lines on
the image.
★ Caused by defective detector elements.
Missing lines or pixels
A bright “halo” seen around dense
objects due to overuse of edge
enhancement algorithms during
processing.
Uberschwinger Artifact (Halo Effect)
A residual image from a previous
exposure remains on the plate.
★ Appears faintly over a new image.
Ghost Images
Distortion due to image stitching
(combining multiple images into one).
★ May cause misalignment or overlap
errors.
Digital Image Composting Artifacts
