Digital Imaging and Image Manipulation

Question 1

first CCD system (3)

Answer 1

1988
Radiovisiography
Trophy X-Ray
Vicennes, France
Invented by
Dr. Francis Mouyen

Question 2

principle of the CMOS detector

Answer 2

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

Question 3

digitization

Answer 3

inside the computer, the electronics instantaneously reads the charge in each pixel, converting the charge into 256 or more shades of gray

Question 4

CMOS
(3)

Answer 4

 Newer technology
 Require less power
 Superior image quality

Question 5

bit depth

Answer 5

the number of colors/gray shades that a pixel is able to show

Question 6

bit depth
number of shades of gray

Answer 6

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

Question 7

CCD and PSP plates have been applied in
(2)

Answer 7

panoramic and plain skull images

Question 8

Similar spatial resolution as film-based format :

Answer 8

4 lp/mm

Question 9

Inferior contrast resolution possibly
compensated by

Answer 9

manipulation function

Question 10

why digital imaging is appealing? (4)

Answer 10

 Significantly less radiation
 Better image (?)
 Lower costs — more net income
 Environmentally friendly - less toxic chemicals are
disposed into the sewage systems

Question 11

 Lower costs — more net income (3)

Answer 11

 Reduced patient chair time
 No variable costs: film, chemicals
 Elimination of the darkroom

Question 12

why dental imaging should be appealing? (3)

Answer 12

 Electronic communication improves efficiency
 Rapid acquisition
 Image portability

Question 13

 Image portability
(3)

Answer 13

• storage
• transmission
• duplication

Question 14

general steps in digital image formation (4)

Answer 14

X
-ray shadow Shadow image
detected by
digital sensor
Numerical pixel
values sent to the
computer
Digital image
on the computer
screen

Question 15

 What is image processing?

Answer 15

 Mathematical manipulation of image data

Question 16

 Qualitative
(2)

Answer 16

 Uses mathematical operations called matrix
transformations
 Magnify, adjust contrast, brightness, gray scale,
colors, swap black and white

Question 17

Analytical

Answer 17

 Measure lengths, pixel values, bone density

Question 18

digital image processing/modifications (4)

Answer 18

• Compression
• Imaging manipulations
• Automated image analysis
• Image reconstruction

Question 19

Compression
(4)

Answer 19

– 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

Question 20

File memory size can become quiet large
due to
(3)

Answer 20

– size of grid (sensor size)
- number of images
- bit depth

Question 21

skipped
Imaging manipulations (7)

Answer 21

➢ Edge Enhancement – sharpening filter
➢ Noise Reduction – softening filter
➢ Optimization of density/contrast
➢ Inversion of gray scale
➢ Magnification
➢ Emboss function
➢ Pseudocolor enhancement

Question 22

To be able process and construct an image,
the computer will

Answer 22

turn the voltage signal to
numbers and then to shades of gray

Question 23

To be able manipulate an image, the computer will
change

Answer 23

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

Question 24

imaging manipulations
 Depend on
 Make the images subjectively more
 DO NOT increase the

Answer 24

viewer preference
appealing
diagnostic
accuracy

Question 25

inversion of gray scale

Answer 25

Reverse the black and white

Question 26

The brightness and contrast adjustments

Answer 26

The brightness and contrast adjustments are
done together to subjectively find the “best”
combination of brightness and contrast to
highlight the clarity of the structures in the
image

Question 27

noise reduction may

Answer 27

May degrade or remove important diagnostic information

Question 28

edge enhancement (4)

Answer 28

 Remove low-frequency noise; increases image
contrast
 Exaggerate the contrast difference between adjacent
pixels; to increase contrast, all pixel values are
stretched; the dark shades become darker and the
light shades become lighter
 Enhances local contrast and makes edges sharper to
diagnose caries, restoration fit, and fractures
 simulates disease; (Is this a good thing?)

Question 29

magnificaiton

Answer 29

Enlarge a specific area till the biggest detail

Question 30

emboss function (inactive)

Answer 30

 Applies a three dimensional effect to the image
 Could be useful in presentation situations

Question 31

Automated image analysis
(5)

Answer 31

• Length (in MiPACS viewer)
• Angles
• Bone Density
• Area
• Circumference
• Etc…

Question 32

linear measurement

Answer 32

measurement of the length of the root canal (to within 0.1mm)

Question 33

automated image measurement

Answer 33

Get an exact measurement of the length of the root canal (0.1mm)
by using the endo needle as reference

Question 34

Image reconstruction

Answer 34

Data is utilized by other software programs
and produces different image presentations