Transcript DIGITAL RADIOGRAPHY- review of the literature (Asma`a).ppsx

College of Dentistry
516 MDS
Asma’a Al-Ekrish
DIGITAL
RADIOGRAPHY
A REVIEW
HISTORY
Image Plate Systems
1947- Berg and Kaiser
1975- optical scanner and
digitizer
1981- publicly presented in
1994- the first dental PSP
(Digora-Sordex)
Solid State Systems
1960's- development of
CCD and CMOS
1970’s- CCD (Bell
Laboratories)
1988- CMOS (Scotland)
1980’s- first intraoral
digital system Francis Mouyen
(Radiovisiography
system RVG,
Trophy, France
TYPES OF DENTAL IMAGES
Analogue:
•
Gray shades are
continuous and
show a gradual
change
Digital:
•
Gray shades have
discrete values and
are assigned to
individual picture
elements.
•
Smooth transitions
changed into a
checker pattern, by
the pixels
IMAGE RECEPTORS




Sensors
When X-rays hit sensor, an electronic charge is
produced on the surface of the sensor.
Electronic signal is sent to the computer (either
directly or indirectly) as an analogue signal and
there is digitized ( by a frame-grabber or A-D
converter)
Measurements of the photon intensity are
transmitted to the computer where they are
recorded numerically
THE DIGITAL IMAGE
B) Image as
detected by
the digital
sensor; each
square is a
pixel.
A) X-ray
shadow.
D) Digital
image on
the
computer
screen.
C) Numerical
representation
of pixel
values.
(van der Stelt 2000; van der Stelt 2005)
THE DIGITAL IMAGE
A) X-ray
shadow.
C) Numerical
representation
of pixel
values.
B) Image as
detected by
the digital
sensor; each
square is a
pixel.
D) Digital
image on
the
computer
screen.
THE DIGITAL IMAGE
THE DIGITAL IMAGE
binary numerals
0 (zero)
1(one)
01101001  28 = 256 possible
combinations
0011100011010101  216 = 64,000
possible
combinations
DIRECT AND INDIRECT
DIGITAL IMAGING
A. Direct Digital Radiography:
Real Time Systems (CCD or CMOS)
B. Semi-direct Digital Radiography
SPS Image Plates
C. Indirect Digital Radiography
Converting a pre-existing analogue image to a digital
one
REQUIREMENTS OF DIGITAL
SYSTEM
1. X-ray generator
2. Sensor
3. Computer
4. Software
5. Monitor
6. Printer
REQUIREMENTS OF DIGITAL
SYSTEM
COMPONENTS OF THE SYSTEM MUST
BE DICOM COMPATIBLE
( Digital Imaging Communication in Medicine )
REAL TIME SYSTEMS
A- Charged Couple
Device (CCD) Sensors
B- Complementary
Metal Oxide
Semiconductors
(CMOS) sensors
REAL TIME SYSTEMS
CCD
Intensifying screen
fibreoptics
CCD
SILICON CHIP WITH ELECTRONIC CIRCUIT
EMBEDDED INTO IT.
REAL TIME SYSTEMS
CCD
Production of the image
X-rays
light from scintillating
layer
To A-D
converter
electronic signal
REAL TIME SYSTEMS
CCD
Production of the image
A-D Converter
1- Sampling
2- Quantization
White and Pharoah (2004)
REAL TIME SYSTEMS
CCD
Advantages
and
Disadvantages
REAL TIME SYSTEMS
CMOS
RAM
Microcontroller
unit
REAL TIME SYSTEMS
CMOS
Advantages
and
Disadvantages
REAL TIME SYSTEMS
CCD vs. CMOS
When invented
Power consumption
Sensitivity to light
Sensitivity to x-rays
Cost
Manufacturing
Fixed pattern noise
Quantum efficiency
CCD
1967
400mW
Excellent
High
High
Expensive
Low
Excellent
CMOS
1967
40mW
Excellent
Unknown
Low
Expensive
High
Fair
Adapted from Langlais, R.P., and Miles D.A. Digital radiographic imaging: Technology for the next
millennium. www. Learndigital.net
REAL TIME SYSTEMS
ADVANTAGES
1. Image immediately displayed
2. Higher spatial resolution than semi-direct systems
(PSP)
REAL TIME SYSTEMS
DISADVANTAGES
1. Cost
2. Bulky
3. Electrical
4. cords
5. Rigid
6. Active- area limitations
(PSP)
IMAGE PLATE SYSTEMS
Photostimulable Phosphor Plates
Protective
coating
backing
barium
flourohalide
IMAGE PLATE SYSTEMS
Production of the Image
Decay of the Image
IMAGE PLATE SYSTEMS
ADVANTAGES
1.Thin
2.Flexible
3.Cordless
4.Size comparable to standard size films
5.Reusable
6.Broad exposure latitudes
7.May be used with existing x-ray generators
IMAGE PLATE SYSTEMS
DISADVANTAGES
1. Extra step- scanning procedure
2. Dose reduction not as much as with solidstate detectors
EXTRA-ORAL RADIOGRAPHY

CCD or PSP may be used

Tomography only with PSP
QUALITY FACTORS

Resolution: how well closely spaced
objects can be distinguished



Sharpness: distinctiveness of feature
boundaries
Contrast: distinctiveness of light and dark
areas.
Distortion: the difference between the
apparent and true locations of points on an
image.
QUALITY FACTORS
Modulation Transfer Function (MTF):
Describes the ability of a system to
record the spatial frequencies that are
available to be recorded

Noise: unwanted fluctuations in image
density

Detector Quantum Efficiency (DQE):
combined effect of noise and contrast
performance of an imaging system,
expressed as a function of object detail.

QUALITY FACTORS
CONTRAST RESOLUTION
QUALITY FACTORS
SPATIAL RESOLUTION
QUALITY FACTORS
SPATIAL RESOLUTION
QUALITY FACTORS
SPATIAL RESOLUTION
QUALITY FACTORS
SIGNAL TO NOISE RATIO (SNR):
Reproduced from Oakley (2003 )
QUALITY FACTORS
ARTIFACTS
Distortions are any unwanted elements in the image
Produced by either:
• the image sensor (CCD/CMOS),
• optical system,
• internal image processing algorithms, or
• compression algorithm.
IMAGE DISPLAY- MONITORS
Cathode Ray Tubes
(CRT)
Flat panel- Liquid
Crystal Displays
(LCD)
Reproduced from Oakley (2003 )
IMAGE DISPLAY- MONITORS
QUALITY FACTORS OF MONITORS
1. dot pitch
2. resolution
3. luminance
4. brightness and contrast settings
IMAGE DISPLAY- MONITORS
QUALITY FACTORS OF MONITORS
5. refresh rate
6. color depth
7. footprint and weight
8. contrast layer
FACILITIES OFFERED BY
DIGITAL RADIOGRAPHY
Dose reduction
( van der Stelt 2000; van der Stelt 2005 )
FACILITIES OFFERED BY
DIGITAL RADIOGRAPHY
Dose reduction
FACILITIES OFFERED BY
DIGITAL RADIOGRAPHY
Image processing
Image Enhancement
Image Analysis
Contrast enhancement
Filtering
Subtraction
Color
Measurement
Segmentation
Feature extraction
Object classification
CADIA
Image Restoration
Image Synthesis
Image Compression
System defects
Geometric
Transformation
Tomosynthesis
TACT
Localized CT
Lossless
Lossy
Miles, D. (2000). "The future of digital imaging in dentistry." Dental Clinics
of North America 44: 427-438
FACILITIES OFFERED BY
DIGITAL RADIOGRAPHY
Storage, archiving, retrieval
FACILITIES OFFERED BY
DIGITAL RADIOGRAPHY
Electronic transmission
GENERAL ADVANTAGES
1.
Dose reduction
2.
Time- faster to acquire
3.
No chemical processing- eliminating processing
errors, saving space and money on the long term.
Environmentally friendly
4.
Long term savings on film processing
5.
Better gray scale resolution
6.
Image processing
7.
Teleradiology
8.
Less storage space
GENERAL DISADVANTAGES
1.
Initial setup cost
2.
Less spatial resolution
3.
Sensor size
4.
Requires more space in the operatory- but no dark
room.
5.
more time to process information
ESSENTAIALS OF ANY
SYSTEM

Quality diagnostic images

Radiation dose less than film

Lossless archiving is allowed in an
image file format DICOM compatible
FUTURE of DIGITAL
RADIOGRAPHY




The paperless office
Computer aided diagnosis and detection
of defects
3-D visualization of dental structures
based on radiographic data at the level of
single teeth
Wireless technology
FUTURE of DIGITAL
RADIOGRAPHY




Continued reduction is storage media and
size
Testing, maintenance, and upgrade of
equipment and software online
Research towards a "smart card"- which
could carry a patient's medical and dental
notes along with their radiographic images
Global education and distanc learning
References:
Analoui, M. and K. Buckwalter (2000). "Digital radiographic image archival, retreival,
and
management." Dental Clinics of North America 44(2): 339-358
Farman, A. and T. Farman (2005). "A comparison of 18 different x-ray detectors currently
used in dentistry." Oral Surg Oral Med Oral Pathol Oral Radiol Endod 99: 485-9.
Miles, D. (2000). "The future of digital imaging in dentistry." Dental Clinics of North
America 44: 427-438.
Oakley, J. (2003). Digital imaging. A primer for radiographers radiologists and health
care professionals. London, Greenwich Medical Media Limited.
van der Stelt, P. F. (2000). "Principles of digital imaging." Dental Clinics of North America
44(2): 237-247.
van der Stelt, P. F. (2005). "Filmless imaging. The uses of digital radiography in dental
practice." JADA 136: 1379-1387.
White, S. C. and M. J. Pharoah (2004). Oral radiology.Principles and interpretation. St.
Louis, Mosby.
Questions?
Thank You