RAD 354 Chapt. 14 Computers in
Medical Imaging
• Historical dates of interest
– 1939 first electronic digital computer built
– 1944 first general purpose “modern computer”
developed
– 1946 first general purpose electronic computer
– 1948 transistor developed
– 1951 UNIVAC commercially successful computer
Digital/Analogue
• Digital is electronic impulses that can be
transmitted across wires or atmospheric
conditions (anywhere electrons can flow) AND
only TWO values = on or off/ 1 or 0
• Analogue – a multitude of VARYING quantities
Types of Computers
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Super computers
Mainframe computers
Workstations
Micro computers
Mini computers
Hardware
• Input (keyboards, pointing devices and sourc e-data
devices)
• Processing – central processing unit (CPU); control unit
and a arithmetic/logic unit; includes memory
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RAM – random access memory
ROM – read only memory
Bit – smallest unit of measure memory
Byte – 8 bits = 1 byte
RAID – redundant array of inexpensive disks****
• Has been defined differently in various texts
Optical disks (have replaces mag
tape/floppies, etc)
• CD – ROM (read only memory)
• CD-R (write data – can be used only once)
• CDE.CD-RW (allow user to erase and re-write
on the CD)
• DVD-ROM (digital versatile disk – read only
memory)
Output Devices
• Usually display screens and printers (others:
plotters, multifunction devices and audio
output devices)
• Output hardware – devices that TRANSLATE
computer information to a form that mere
humans can understand
Transmission speed (modem transfer
in bits/second- BPS
• Integrated Services Digital Network (ISDN)
“dial up” modem
• Digital Subscriber Lines (DSL) – much faster
than ISDN, but still can be done via phone
lines
Software
• Written in computer language so the
hardware can function and do what we want
it to
– “Binary numbers/switches” either 1/0 or on/off
Languages
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FORTRAN
COBOL
ALGOL
BASIC
BCPL
B
C
– REVIEW ALL AS THEY MAY BE ON THE BOARDS!
Processing Methods (does PACS ring a
bell?)
• Batch – without needing human input to
perform
• On-line – done online and immediately
• Time-sharing = makes one think he/she is the
“only one using the system”
• Real-Time = instant/fast management of the
system hardware
PACS Workflow
RAD 353 Chapt. 15 Computed
Radiography
• The medical digital terms are NOT uniform,
but vary according the BRAND of equipment
one uses
• Fuji introduced “digital imaging” in 1981
– Many forms of digital
• CE/CD
• DR/DD
CR/DD Terms
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PSL = photostimulable luminescence
PSP= photostimulable phosphore
SPS = storage phosphor screen
IP = imaging plate
SP = storage phosphor
PMT = photomultiplier tube
PD = photodiode
LUT = look up table
DICOM = digital imaging and communication in
medicine
PSL & PSP
• Photostimulable luminescence (PSL) – emit
light promptly AND at a later time!
• Photostimulable phosphor (PSP) = barium
fluorohalide – looks physically like an
intensifying screen BUT stores the latent
image via metastable electrons (STORAGE
PHOSPHOR SCREENS) = SPSs
The “Imaging plate”
• The PSP screen is inside a “rigid,” brittle,
breakable cassette
• The actual imaging receptor is called the
IMAGING PLATE
Light Stimulation Emission
• Process similar to Thermosluminescent
Dosimetry (TLD – film type badges for
dosimetry)
• They are either “powder” ( like an intensifying
screen crystal) OR arranged like “needles”
– i.e. Powder PSP or Needle PSP
Thoughts on PSP’s
• Powder vs “needle”
• Highly sensitive to RADIATION = easily fogged!
CR Reader
• The physical receptor/imaging plate/casstte is
“loaded” into the reader
– IP is removed and moves along the LONG AXIS odf
the IP!!! (slow scan)
– As the IP is moved, a deflection device is used to
deflect the LASER beam across the IP (fast scan)
• IP doesn’t really separate from the cassette housing
and doesn’t go around “rollers” etc.
CR Optical Feature
• To properly and precisely translate EACH
metastable electron (latent imaging forming
charge) in a PRECISE fashion to provide for
great SPATIAL RESOLUTION
Compare and contrast film-screen to
CR/CD/DD techniques
• Film-screen has much LOWER latitude than
CR/CD/DD!!!
– As such, a WIDE variety of techniques can be used
– “Burn em up BURNIE!!!” If in doubt – BURN IT
OUT
• Compare Characteristic curves for each:
Image Noise
• Box 25-1 SAME as for screen-film noise
• PLUS Box 25-2
– Mechanical defects – due to scan drivers
– Optical defects – laser, stimulating beam, light
quanta emission and collected
– Computer defects – electronic noise; too few
sampling; too little quantization
PACS workflow
Non-DICOM/DICOM
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RAD 354 Chapt. 24 Into to Computer Science