Computers in Medical Imaging – Chapter Computer Networks, PACS and Teleradiology – Chapter 17 Brent K Stewart, PhD, DABMP Professor, Radiology and Medical Education Director, Diagnostic Physics a copy of this lecture may be found at: http://courses.washington.edu/radxphys/PhysicsCourse04-05.html Brent K Stewart, PhD, DABMP Outline ¬ ¬ ¬ ¬ ¬ ¬ ¬ ¬ Storage and Transfer of Data in Computers Analog Data and Conversion between Analog and Digital Forms Components and Operations of Computers Performance of Computer Systems Computer Software Storage, Processing and Display of Digital Images Computer Networks PACS and Teleradiology Brent K Stewart, PhD, DABMP Brent K Stewart, PhD, DABMP Decimal Form (Base 10) ¬ ¬ ¬ ¬ In general, a positional numbering system encodes the numbers as: anbn + an-1bn-1 + + a2b2+ a1b1+ a0b0 (0 < < b, i = 0,1,2, ,n), where the integer b > is the radix (or base) of the numbering system The leftmost digit is called the most significant digit, the rightmost the least significant digit Whenever it is not clear which base is being used either a subscript will be used to denote it or the base will be written in parentheses Decimal form (radix 10): 4210 = (4x101)+(2x100) Brent K Stewart, PhD, DABMP Binary Form (Base 2) ¬ ¬ ¬ Powers of 2: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024 Binary form (radix 2): 1010102 = (1x25)+(0x24)+ (1x23)+(0x22)+ (1x21)+(0x20) = 3210 + 810 + 210 = 4210 Other radices used in computing ¬ ¬ Octal (b=8) Hexadecimal (b=16; A=10, … F=15) Brent K Stewart, PhD, DABMP Conversion between Decimal and Binary Forms ¬ Conversions between decimal and binary forms: keep dividing by powers of the target radix until you are left with a remainder < b Bushberg, et al., The Essential Physics of Medical Imaging, 2nd ed., pp 6262-63 Brent K Stewart, PhD, DABMP Digital Representation of Data (1) ¬ Bits, Bytes and Words ¬ ¬ ¬ ¬ Smallest unit of storage capacity = bit (binary digit:1 or 0) Bits grouped into bytes: bits = byte Word = 16, 32 or 64 bits, depending on the computer system addressing architecture Computer storage capacity is measured in: ¬ ¬ ¬ ¬ kilobytes (kB) - 210 bytes = 1024 bytes ≈ a thousand bytes megabytes (MB) - 220 bytes = 1024 kilobytes ≈ a million bytes gigabytes (GB) - 230 bytes = 1024 megabytes ≈ a billion bytes terabytes (TB) - 240 bytes = 1024 gigabytes ≈ a trillion bytes Brent K Stewart, PhD, DABMP Digital Representation of Data (2) ¬ Digital Representation of Different Types of Data ¬ ¬ Alphanumeric text, integers, and non-integer data Storage of Positive Integers ¬ ¬ ¬ ¬ ¬ ¬ In general, n bits have 2n possible permutations and can represent integers from to 2n-1 (the range usually denoted with square brackets): n bits represents 2n values with range [0, 2n-1] bits represents 28 = 256 values with range [0, 255] 10 bits represents 210 = 1024 values with range [0, 1023] 12 bits represents 212 = 4096 values with range [0, 4095] 16 bits represents 216 = 65,536 values with range [0, 65535] Brent K Stewart, PhD, DABMP Digital Representation of Data ¬ Binary Representation of Signed Integers ¬ ¬ ¬ ¬ Floating Point Form ¬ ¬ ¬ 23 For very large or very small numbers (e.g., 6.023 x 1023) 010011112 Similar to scientific notation: 0.111111112 x Binary Representation of Alphanumeric text ¬ ¬ ¬ ¬ Include the use of negative numbers Reserve first bit for the sign (+/-): [-127,127] – one’s complement Two’s complement: [-128, 127] – simplifies electronic circuitry ASCII = American Standard Code for Information Interchange ASCII code for representation of text, e.g., A = 01000001 Stored in one byte (128 characters) Computer needs to keep track of the data type Brent K Stewart, PhD, DABMP 10 Transfers of Data in Digital Form ¬ ¬ ¬ ¬ ¬ ¬ Data are transferred between the various components of the computer and with devices external to the computer in binary format A voltage of fixed value (e.g., +5V) is used to represent Another voltage value (e.g., 0V) is used to represent Changes between the voltage states occur through synchronization signals from the computer’s clock clock cycle = the minimum time increment (τ) at which a1 or transition can occur clock frequency = 1/τ (usually given in MHz or GHz) Brent K Stewart, PhD, DABMP 59 Local Area Network (LAN) ¬ ¬ ¬ ¬ Topology: star, ring and bus Protocol: Internet and Ethernet use TCP/IP = Transport Control Protocol/Internet Protocol Media: wire, fiber-optic and air Ethernet ¬ ¬ ¬ ¬ Shared bandwidth Switched – full duplex 10, 100, 1000 and 10,000 Mbps/sec ATM/SONET ¬ ¬ ¬ Asynchronous Transfer Mode Synchronous Optical Network 155, 622 and 2,500 Mbps Brent K Stewart, PhD, DABMP 60 Wide Area Network (WAN) Internet = LANs mesh connected with WANs all using TCP/IP Brent K Stewart, PhD, DABMP 61 Acquisition of Digital Images ¬ ¬ Film digitization and frame grabbers (old) DICOM modalities ¬ ¬ ¬ ¬ ¬ ¬ ¬ ¬ Computed Tomography (CT) Magnetic Resonance Imaging (MRI) Nuclear Medicine (including SPECT and PET) Ultrasound (US) Computed Radiography (CR) Digital Radiography (DR) Digital Fluoroscopy (DF) Mammography (one digital, but mostly film) Brent K Stewart, PhD, DABMP 62 Storage of Images ¬ Data Storage Technologies (redundancy and backup) ¬ ¬ ¬ ¬ ¬ ¬ Hierarchical Storage Management (HSM) systems RAID: redundant array of inexpensive disks Magneto-optic disk (MOD/EOD) WORM optical disks Digital Linear Tape (DLT) and other tape formats, e.g., D2, D3 Data Compression ¬ ¬ Lossless (compression ratio < 4:1) Lossy (compression ratio > 4:1) 10 Mbytes Mbytes Mbytes 2.5:1 Brent K Stewart, PhD, DABMP 10 Mbytes 63 Brent K Stewart, PhD, DABMP 64 Display of Images for Interpretation ¬ ¬ Large format raster-scanned CRT and LCD (flat panel) CRT/LCD more or less equivalent to film ¬ ¬ ¬ ¬ ¬ ¬ ¬ Lesser spatial resolution, greater contrast resolution (LUT) Pixel Resolution: 1024 x 1280 (C), 1200 x 1600 (B), 1728 x 2304 (A) Luminance: 240-280 cd/m2 vs 1713 cd/m2 (light box) Dynamic Range: bit depth (16-bit per pixel frame buffer) Veiling Glare: stray ambient light reduces contrast ROC Studies: OK for primary diagnosis Some 3MP flat panel monitors already in the depart ¬ 1536 x 2048 pixels and 700 cd/m2 Brent K Stewart, PhD, DABMP 65 Neuroradiology Reading Room 4B w/s 1200x1600, $54K Brent K Stewart, PhD, DABMP 66 Registration ADT 27 Step PACS Shuffle ADT ADT DICOM HL7-DICOM Broker DICOM DICOM SQL CR 17 SQL PACS Database Modality Worklist Storage SCU HL7 Interface Engine Order 16 Report ADT IDXrad RIS 11 SQL DICOM SQL PACS Archive DICOM 10 DICOM DICOM MR Modality Worklist Storage SCU Web Browser Order SQL 14 Report ADT CT Modality Worklist Storage SCU Order 15 Report 27 Exam Series/ Images 13 Accession Number 12 DICOM MINDscape 20 Cookie Brent K Stewart, PhD, DABMP Order PACS Workstation 16 Report 26 CGI Query 21 Select Report 19 Logon 18 SQL PACS Web Server 25 Select Exam 24 Report Talk Voice Recognition 23 SQL Return 22 SQL Query MIND 67 Display of Images for Consultation Brent K Stewart, PhD, DABMP 68 Brent K Stewart, PhD, DABMP 69 PACS Web on MCIS PC 1280x1024 $3K Brent K Stewart, PhD, DABMP 70 5E ICU PACS 2C workstation 1280x1024, $27K (same monitors as Web) Brent K Stewart, PhD, DABMP 71 Back to the Future “There is no reason anyone would want a computer in their home.” - Ken Olson, president, chairman and founder of Digital Equipment Corp., 1977 Brent K Stewart, PhD, DABMP 72 Raphex 2002 Diagnostic Question ¬ D45 The number of 512 x 512 images with 12 bit pixel values that can be stored on a gigabyte optical disk is approximately _ (Assume integer byte values at each pixel location.) ¬ ¬ ¬ ¬ ¬ ¬ A B 40 C 500 D 4000 E 5000 2GB = 231; 512x512x2bytes/pixel = 219; 231/219 = 4096 Brent K Stewart, PhD, DABMP 73 Raphex 2003 Diagnostic Question ¬ D50 A DICOM standard for cine specifies that the image matrix is 512 x 512 with a depth of bits per pixel You have the need to store high-speed, high-resolution DSA raw data (1024 x 1024 x 16 bits) The relative disk storage space needed to store an individual image for the latter is times as large as the original ¬ ¬ ¬ ¬ ¬ A 32 B 16 C D E Brent K Stewart, PhD, DABMP [...]... signal into a frequency-coded signal for transmission over a telephone line Brent K Stewart, PhD, DABMP 32 Hierarchy of Software ¬ Applications Software - programs to perform specific functions desired by the user ¬ ¬ ¬ ¬ May be written in either high-level or machine language Generally an executable program run by the OS Hopefully user-friendly, flexible and intuitive to use Operating System (OS) - the... Usually stored as a 2D array of data, I(x ,y) : I(1,1), I(2,1), … I(n,m-1), I(n,m) ¬ Each minute region of the image is called a pixel (picture element) represented by one value (e.g., digital value, gray level or Hounsfield unit) ¬ Typical matrices – CT: 512x512x12bits/pixel; DR: 2048x2560x10 bits/pixel ‡ ¬ Total number of bytes/image = pixels/image · bits/pixel · (1 byte/8 bits) ‡ aligned along byte... printed ¬ ¬ ¬ Video display controller/card ¬ ¬ ¬ ¬ ¬ Cathode ray tube (CRT) Flat-panel display (TFT = thin-film transistors) Receive digital data from computer memory Store locally on card with VRAM (video RAM) Registers to manipulate the original image or text data DACs to convert into on-screen video image Usually computer equipped with keyboard, mouse, trackball or joystick (could be head-less... characterized by ¬ ¬ sampling rate or frequency (e.g., samples/sec – 1 MHz) number of bits output per sample (e.g., 12 bits/sample = 12-bit ADC) Bushberg, et al., The Essential Physics of Medical Imaging, 2nd ed., p 69 Brent K Stewart, PhD, DABMP 15 ADC Potential Loss of Data ¬ ¬ ¬ Sampling and quantization (digitization): loss of data (necessary evil) Minimum sampling frequency (Nyquist limit) to accurately represent... power goes off? G77 Which device can you generally not write over again? Brent K Stewart, PhD, DABMP 31 Raphex 2002 General Question ¬ G82 Concerning digital computers, all of the following are true, except: ¬ ¬ ¬ ¬ A ROM stands for Random Order Memory B A word is a set of consecutive bits treated as an entity, and occupying one storage location in memory C A byte contains 8 bits D A modem is a device... 18 Main Memory ¬ ¬ ¬ ¬ ¬ ¬ ¬ ¬ Random access memory (RAM): volatile Buffer between CPU and mass storage devices Memory addresses where data and instructions reside Also read-only memory (ROM): static DRAM: dynamic RAM SRAM: static RAM (cache) VRAM: video RAM (display card) All RAM volatile! Brent K Stewart, PhD, DABMP Bushberg, et al., The Essential Physics of Medical Imaging, 2nd ed., p 71 19 Central... Portability Permanence (CD-R vs CD-RW) Mechanical drive Storage medium Controller Hierarchical: trade-off speed vs cost per MB Brent K Stewart, PhD, DABMP 23 Mass Storage Devices Bushberg, et al., The Essential Physics of Medical Imaging, 2nd ed., p 76 Brent K Stewart, PhD, DABMP 24 Display Interface and Keyboard/Pointing Devices ¬ ¬ Display computer information in visual form Usually displayed on a... OS, Linux, UNIX Brent K Stewart, PhD, DABMP 33 Computer Security ¬ Goals ¬ ¬ ¬ ¬ Data Backup Practicing “Safe Computing” ¬ ¬ ¬ Malicious programs exist, such as viruses, worms, Trojans, time bombs, and password grabbers Types of viruses: executable file, boot sector and macro infectors Deny unauthorized users access to your system ¬ ¬ ¬ Deny unauthorized persons access to data Protect programs and data... instructions for CPU execution Instruction cycle - CPU fetches the instructions from memory and executes them sequentially An instruction may cause the CPU to perform one of the following: ¬ ¬ ¬ ¬ ¬ Mathematical operation Transfer data Compare Jump to an instruction other than the next in the sequence Each instruction consists of two parts: an opcode specifying the operation to be performed and an address... some operating systems Brent K Stewart, PhD, DABMP 27 Brent K Stewart, PhD, DABMP 28 Performance of Computer Systems ¬ ¬ ¬ ¬ ¬ ¬ ¬ ¬ Review Many factors that affect the time required for a computer to complete a task Clock speed of the CPU, e.g., 3.4GHz Pentium 4 CPU architecture, e.g., number of bits/instruction and parallelism Width and clock speed of the I/O between Memory hierarchy, dimensions and