RAD 354 Chapt. 24 Intro to Computer Science

• 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

• 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– 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

• 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. 25 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

• 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