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วรงค โตเจริญชัยM.S. Electrical and Computer Engineering
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References:http://www.sprawls.org/resourceshttp://www.sprawls.org/resources/DIGRAD/classroom.htm
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Picture Archiving and Communication System (PACS)
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CR/Modality/Digital Radiography
CR
1. Reader Unit
Imaging Plate
DICOM 3
PACS Server
2. Console (Image Processingand Registration computer)
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2
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Patient Registration
001
James เจมส
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Workflow
Screen/Film CR (Digital)
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Workflow
Screen/Film CR (Digital)
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Patient Information System
1. Manual key in from the Console of Modalities
2. Query from the PACS worklist (need Modality Worklist)
การลงทะเบียนผูปวยจากระบบ HIS หรอื RIS ซ่ึงระบบดังกลาวจะสงขอมูลตามมาตรฐาน HL/7 ไปใหระบบ PACS เพ่ือให Modality สามารถดึงขอมูลการลงทะเบียนลวงหนา (modality worklist) ที่มีอยูในระบบ PACS มาใชได
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Patient Information Work flow
Registration
Patient
1Register
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Query/Retrieve
patient’s info.
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X-ray
HIS Server
Doctor
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See Doctor
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Request X-Ray
X-Ray Registration RIS Server
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Query/Retrieve
X-Ray exam.’s info.
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Query/Retrieve info.
PACS Server
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Store ImagesX-Ray CR/DR10
Query Images
9Query/Retrieve info.
11Query
Report
PACS Viewer
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HIS
PACS/HIS/RIS CONNECTION
TEST SERVER
SERVER& RAID
SERVER& RAID
SERVER& RAID
Rack
RISorders
reports
DMWL
DICOM
RISReportorders
DICOM
reports
PACS RIS
Voice Recognition3D Reconstruction
MS Office
IHE - Integrated Health Enterprise
ImageReport
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Patient Worklist
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Patient Information and Image
Patient Information
(HN, Name, Age, etc.)
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Patient Folder Hierarchy
Patient Folder
Study Folder
Series Folder
Images
Study Folder
Series Folder
Images
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How to get Digital image ?
• Digital Detector• CR – Computed Radiography• DR – Digital Radiography
• Direct Digital Radiography• Indirect Digital Radiography
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Detectors
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Computed Radiography
Computed Radiography
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Computed Radiography
Imaging PlateConsole
Reader Unit
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CR Basics
Computed Radiography refers to the use of Photostimulable Storage Phosphors (PSP or Imaging Plate - IP) in image capture and subsequent image digitization for Projection Radiography applications.
Light Shielding Layer
Protective Laminate
Conductive Layer
Phosphor LayerBaF(BrI):EU2+
ID Barcode Label
Flexible support
Backing Layer
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Phosphor material
Barium fluorohalide crystal with a trace of bivalent europium ionsBaFX:Eu2 , X=Cl, Br, I
•Exposure
•Instant luminescence
•Storage
•Stimulated luminescence
Imaging plate
50% after 24 hours
100%
50%
0%0 Hr 12 Hrs 24 Hrs
% L
umin
osity
Time
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Imaging plate X-Ray tube
Reading Unit
Optical Scanner
LaserBeam
Erasingunit
Light
Principles Employed In Image Acquisition, Reading and Erasure
CR Image Acquisition
Exposure
Patient
Reading System of Storage Phosphor
A/D
Converter
Laser Beam
Imaging Plate
Optical Scanner
Photomultiplier Tube
Motor
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Dual Side Reading
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New Imaging Plate : for Pediatric and Mammogram
1. Thicker layer2. Transparent support
Imaging Plate forSingle Side Reading
Protect layer
PhosphorLayer
Base Layer
Imaging Plate forDual Side Reading
(Pediatric and Mammography)
Laser beam
3. Finer Grain Phosphor (↑sharpness)
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Digital Radiography
(Direct) Digital Radiography30
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Detectors
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DR Detector Technology
1. CCD based systems (Indirect)2. Amorphous Silicon system (Indirect)3. Amorphous Selenium system (Direct)4. Phosphor + Line scan CCD (Indirect)
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Detector technology:1. CCD based systems
A. Lens Coupling B. Fiber optic coupling C. multiple detectors
A phosphor screen converts X-rays into visual light that is projected onto a CCD or onto a CCD-array
source: www.dondickson.co.uk34
Light photon
X-ray photon
Scintillator
(2688 x 2688 pixel)43cm x 43cm
a-Si sensor
GOS (Gd2O2S:Tb)or CsI
Detector technology:2. Scintillator + Amorphous Silicon (A-Si)
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Detector technology:2. Scintillator + Amorphous Silicon (A-Si)
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Pixel size : 160μm x 160μm
Signal line Gate line Bias line
a-Si MIS-type photoelectric converter
a-Si TFT
Magnified Picture of a-Si sensor
1 Pixel
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3. Photo Detector (Direct) - Amorphous Selenium
TopElectrode
Selenium
Thin filmtransistorarray
Glass Substrate
- - - -+ + ++
Read- out
Power supply
X-ray
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3. Photo Detector (Direct) - Amorphous Selenium
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Detector technology:4. Phosphor + Line scan CCD
Device IP
Scanning direction
Side View
Linear Laser SourceInline CCD (receives emitted light )
Line Scan
Light Collection Lens
Top View
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Laser Diode
CCD Array
IP
Emitted Light
Line scan CCD Technology
Aluminum
Phosphor700μm
PETPhosphor
Focused Phosphor ST-VI
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Detector technology: Summary
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Detected Quantum Efficiency (DQE)
What is DQE ?
An expression of the efficiency of an image system’s transfer, from its input to its output, as a percentage of signal to noiseratio (SNR).
inputdetector at outputdetector at
2
2
SNRSNRDQE =
DQE is limited to ~70% in practice
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DQE of detectors
DQE
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DQE Comparison
source: www.dondickson.co.uk
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Noise and Contrast
source: www.dondickson.co.uk
The detection of low contrast and high noise is a requirement
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Detector Resolution/DQE
Highest
Medium
Lowest
Contrast resolution
DQESpatial resolution
Highest~80-150 micronDR
Medium50-100 micronCR
Lowest~25 micronScreen/Film
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CR Technology
CR Advantages1. Superior flexibility and portability2. Existing x-ray system3. Lower cost than DR (Support multi-room)
CR Disadvantages1. There are cassettes to handle2. Longer image acquisition than DR3. Throughput
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DR Technology
DR Advantages1. Short processing time and image acquisition2. No imaging plates or cassettes to hassle with3. Higher DQE (contrast)
DR Disadvantages1. More expensive than CR2. Mobile radiography necessitates a wire cable3. The imaging sensor is more expensive to replace 4. Replaced/modified existing x-ray equipment
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Trends
CR • Faster throughput• Higher DQE
DR • Cheaper• Flexibility & Portability
Both technologies will probably coexist in future
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Patient Worklist
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Patient Folder Hierarchy
Patient Folder
Study Folder
Series Folder
Images
Study Folder
Series Folder
Images
HEADER (Information about image)
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Matrix size VS File size
File size of a 128x128x8 bits image ?
128x128x1 byte = 16,384 bytes (16 kB)
8 bits1 2 3 ………. 128
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128
3
.
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12
8
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Image VS File size
Image size increase 1 step (128 to 256)>> File size increase 4 times
128
256
512
512
1024
1024
256
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Characteristic Curves
DigitalDetector
Screen/Film
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103
102
101
100
10-110-2
1
2
3
100 101 102 103
Exposure mR
Film
Den
sity
Inte
nsity
rela
tive
of th
e lu
min
osity
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Dynamic Range
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10 Bit
SmaxSmin
Automatically detect bone to airand 10 bits are assigned
No Clinical InfoNo Clinical Info
12 Bit
Histogram Analysis
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The value of each pixel and the number of times that the pixel value occurs in the image
Histogram Analysis
1 2 3 4 5S1
S2S3
S4S5
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5(S1 and S2) are established to define the Lowest and
Highest areas of useful exposure as determined by the menu selection.
Bone Soft Tissues Skin Air
S1 S2Rel
ativ
e Fr
eque
ncy
X-Ray Dose ( Exposure)
Histogram Analysis : General
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Internal Organs Skin Air
S1 S2
Spine
Histogram Analysis : Spine
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Gastric
Barium Internal organs Skin Air
S1 S S2
Histogram Analysis : GI
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Spine image : Spine Protocol
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Spine image : Chest Protocol
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Spine image : Hand Protocol
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Low energy (kVp) gives a wider histogram
High energy (kVp) gives a narrow histogram
Histogram Analysis
Step wedge
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Histogram width is controlled by the kVp and subject contrastThe lowest amount of exposure (Smin/S1) and highest (Smax/S2) are recorded
Histogram Analysis
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It reflects the center of the usable portion of the histogram
Calibration is based on a 1 mR exposure at 80 kVp to the IP. Using a 72” distance through air to achieve an “S” number of 200 with a fixed
latitude “L” of 1.
“S” Number - Sensitivity
3 different mAs exposures (80kV)
The histogram shape is the same
The position on the exposure axis
changes.
“S” Number - Sensitivity
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Scatter – Use of Grids Distance – SIDCollimationMenu selectionDelay in processing from time of exposure
Factors that affect “S” number
An “S” number under 75 is typically considered over exposure
Under exposure is generally represented by an “S” number greater than 500
“S” Number - Sensitivity
Chest, General 200-600 Chest, Port. 100-400
Skull 100-400 Abdomen 100-400
Spine 100-400 GI 100-300
Extremities 75-200
Chest, Pedi. 200-700 Abdomen, Pedi. 200-700
Typical “S” # Range
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Anatomical menu selectionCenteringCollimationGrid used (subjects > 10 cm)Proper kVp range selectedCheck “S” number and “L” valueIP used or erased in past 48 hours
Image Quality Review
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>10 cm
80 kVp
Day 1
Portable Chest - No Grid
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Portable Chest – 6:1 Grid
Same Pt.
85 kVp
Day 2
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You be the Judge
Day 1 Day 2
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Images should not be critiqued by “S” number alone.
It is very important to view the whole image
Image Quality Review
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Image ProcessingMulti-objective Frequency Processing (MFP)
MFPConventional
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An enhancement coefficient can be set for each size structure.Image quality can be freely adjusted just like sound quality that can be adjusted freely with a graphic equalizer.
Sound Quality Adjustment (graphic equalizer)
Soun
d
Low Frequency High
Sound quality can be freely adjusted.Sounds above a certain frequency can be adjusted.
Conventional processing Multi-objective Frequency Processing
Large Structure Size Small
Image Quality Adjustment (frequency processing)
Small structures below a set size can be enhanced.
Image quality can be freely adjusted.
Low Frequency High
Soun
d
Res
pons
e
Res
pons
e
Large Structure Size Small
Enhancement Characteristic Optimization
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Image ProcessingGradation and Frequency processing
Left side image(Stimulating F/S)
Right side image(Enhanced image)
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Image ProcessingDynamic Range Control (DRC)
No DRC process DRC process
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Image ProcessingGPR (Grid Pattern Removal)
Removes stationary grid pattern
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ObjectiveSuppress noise in an image with minimum loss of diagnostic information (sharpness) while enhancing image quality.
Image ProcessingFNC : Flexible Noise Control
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Noise component extraction
processing
Suppression coefficient (0.0
to 1.0)
Overview of Processing
Subtraction
Original image Noise-suppressed image
Noise components
Image ProcessingFNC : Flexible Noise Control
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Com
bina
tion
Proc
essin
g
EdgeDetection
Processing
CalcificationPosition
DetectionProcessing
Calcification Edge
Information
OriginalImage
Detection of Centerof Calcification Image
Non-Calcification Edge
Image Processing - MammographyPattern Enhancement Mammography (PEM)
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Image ProcessingEnergy subtraction
Original Image Soft Image Bone ImageDifferentiation between tumor and Calc.
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Image ProcessingEnergy Subtraction
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Energy Subtraction Principle
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PACSServer Farm Doctor’s home
InternetInternet OPD2
OPD1Ward
Radiology Department
Enterprise PACS Network
Intranet
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• LCD Monitor > 20” color or B/W (calibrated)• High resolution 3-15 Mega Pixels• High Brightness > 500 Cd/m2, Contrast Ratio > 600:1
• Need special display adapter or VGA Card• Consistent Image Quality and Medical Approval (FDA)
Diagnostic Display
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Display Luminance (cd/m2) Controlled
• View Box ≥ 1000 No
• LCD Display 200 – 300 No(Consumer)
• LCD Display 500 – 1000 Yes(Medical grade)
Brightness or Luminance
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Constant Luminance for the Life of the Display
600 cd/m2
6500 hours
500 cd/m2
17000 hours
700 cd/m2
2000 hours
800 cd/m2
200 hours
Maximum Luminance as a function of Runtime
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60
65
70
75
80
85
90
95
100
1 10 100 1000 10000 100000
Backlight Operation (Hours)
Lum
inan
ce (%
)
LCD Vendor Data
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SMPTE Pattern for testing monitor
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Technology Selections
• Applications • Reading Speed (films/hour)• Resolution (pixels/mm)• Software /ease of use• Service and support
Energy Subtraction
CassetteLess
Compact General Chest Check upMammogram112
CR Conclusion
Image acquisition1. Imaging plate2. CR Reader unit3. Image processing computer (CR console)
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DR Conclusion
Type of DR/Image acquisition1. CCD2. Amorphous Silicon3. Amorphous Selenium4. Phosphore + CCD
DQE (efficiency of detector)
Noise vs. Contrast
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