Digital Imaging and Image Manipulation Flashcards
first CCD system (3)
1988
Radiovisiography
Trophy X-Ray
Vicennes, France
Invented by
Dr. Francis Mouyen
principle of the CMOS detector
X-ray → scintillating material → light photos → silicon → electrons
deposited in electron wells and converted to voltage in each pixel→
smoother signal digitization → software processing → images on
monitor
digitization
inside the computer, the electronics instantaneously reads the charge in each pixel, converting the charge into 256 or more shades of gray
CMOS
(3)
Newer technology
Require less power
Superior image quality
bit depth
the number of colors/gray shades that a pixel is able to show
bit depth
number of shades of gray
2^(bit)
1 bit (21
) = 2 shades of gray
2 bits (22
) = 4 shades of gray
3 bits (23
) = 8 shades of gray
4 bits (24
) = 16 shades of gray
8 bits (28
) = 256 shades of gray
16 bits (216) = 65,536 shades of gray
24 bits (224) = 16.7 million shades of gray
CCD and PSP plates have been applied in
(2)
panoramic and plain skull images
Similar spatial resolution as film-based format :
4 lp/mm
Inferior contrast resolution possibly
compensated by
manipulation function
why digital imaging is appealing? (4)
Significantly less radiation
Better image (?)
Lower costs — more net income
Environmentally friendly - less toxic chemicals are
disposed into the sewage systems
Lower costs — more net income (3)
Reduced patient chair time
No variable costs: film, chemicals
Elimination of the darkroom
why dental imaging should be appealing? (3)
Electronic communication improves efficiency
Rapid acquisition
Image portability
Image portability
(3)
- storage
- transmission
- duplication
general steps in digital image formation (4)
X
-ray shadow Shadow image
detected by
digital sensor
Numerical pixel
values sent to the
computer
Digital image
on the computer
screen
What is image processing?
Mathematical manipulation of image data
Qualitative
(2)
Uses mathematical operations called matrix
transformations
Magnify, adjust contrast, brightness, gray scale,
colors, swap black and white
Analytical
Measure lengths, pixel values, bone density
digital image processing/modifications (4)
• Compression
• Imaging manipulations
• Automated image analysis
• Image reconstruction
Compression
(4)
– affects image file size in memory storage
- useful for storage issues eg. “zipping” files
- actual file size is larger that stored file size
- compression is an algorithm tha can shrink the
file size for storage and recreate the data when
retrieving the data
File memory size can become quiet large
due to
(3)
– size of grid (sensor size)
- number of images
- bit depth
skipped
Imaging manipulations (7)
➢ Edge Enhancement – sharpening filter
➢ Noise Reduction – softening filter
➢ Optimization of density/contrast
➢ Inversion of gray scale
➢ Magnification
➢ Emboss function
➢ Pseudocolor enhancement
To be able process and construct an image,
the computer will
turn the voltage signal to
numbers and then to shades of gray
To be able manipulate an image, the computer will
change
density values to predetermined numbers
which then changes the image’s presentation i.e.,
lighter darker, etc.
Are post post-display mathematical algorithms that
manipulate the digital signal
imaging manipulations
Depend on
Make the images subjectively more
DO NOT increase the
viewer preference
appealing
diagnostic
accuracy
