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RAD 354 Chapt . 14 Computers in Medical Imaging

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

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RAD 354 Chapt . 14 Computers in Medical Imaging

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  1. 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

  2. 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

  3. Types of Computers • Super computers • Mainframe computers • Workstations • Micro computers • Mini computers

  4. Hardware • Input (keyboards, pointing devices and sourc e-data devices) • Processing – central processing unit (CPU); control unit and a arithmetic/logic unit; includes memory • 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

  5. 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)

  6. 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

  7. 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

  8. 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

  9. Languages • FORTRAN • COBOL • ALGOL • BASIC • BCPL • B • C • REVIEW ALL AS THEY MAY BE ON THE BOARDS!

  10. 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

  11. PACS Workflow

  12. 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

  13. CR/DD Terms • PSL = photostimulable luminescence • PSP= photostimulablephosphore • 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

  14. 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

  15. The “Imaging plate” • The PSP screen is inside a “rigid,” brittle, breakable cassette • The actual imaging receptor is called the IMAGING PLATE

  16. Light Stimulation Emission • Process similar to ThermosluminescentDosimetry (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

  17. Thoughts on PSP’s • Powder vs “needle” • Highly sensitive to RADIATION = easily fogged!

  18. 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.

  19. 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

  20. 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:

  21. 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

  22. PACS workflow

  23. Non-DICOM/DICOM

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