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(BQ) Part 2 book “Radiography in the digital age” has contents: Computer basics, creating the digital image, digital image preprocessing and processing, digital image postprocessing, postprocessing operations in practice, applying radiographic technique to digital imaging,… and other contents.
Part III DIGITAL RADIOGRAPHY Conventional radiographs of autopsied coronal slices through the chest and head of a human corpse, appearing somewhat like MRI images Chapter 28 COMPUTER BASICS Objectives: Upon completion of this chapter, you should be able to: Overview how computer hardware and software interact to perform tasks at high speed List the types of computers and terminals, and how they relate to radiography Overview the history and development of computers and micro-circuitry Describe how peripherals integrate with the central processing unit Describe the types of storage and main components in the CPU Describe the types of storage and major components of a typical PC Distinguish between the various characteristics of modern digital memory Analyze the differences between analog and digital data and how they relate to radiographic images Understand the basic aspects of binary code and ASCII code 10 Overview the general types of software and levels of machine language 11 Define the four levels of data processing 12 Overview the hardware components and compatibility of digital communications systems A computer is any machine that can perform mathematical computations, manipulate information, make decisions and interact accurately and quickly All of these functions are based upon the fundamental ability of the machine to follow preprogrammed instructions known as algorithms Each algorithm is a concise set of instructions for a single, specific task, such as how to subtract two numbers that are inputted into the computer by the user A computer program is a collection of many hundreds or even thousands of interrelated algorithms which allow the user to perform a general application such as calculating taxes, word processing, or organizing a data base To avoid repetitious programming and wasteful duplication, algorithms that will be used repeatedly within a program, called subroutines, are written only once and stored apart from the overall instructions, where they can be accessed as often as needed by a “go to” command Artifical intelligence (AI) describes the ability of a machine to make decisions based on logic functions such as “do,” “if then,” and “if else.” An example of an algorithm for an “if else” statement might be as follows: 429 Store number A inputted from keyboard at memory address Retrieve permanently saved number B from memory to calculator Retrieve inputted number A from memory to calculator Subtract B minus A IF the result of step is positive, (if B is greater than A), go to line ELSE, (if B is NOT greater than A), go to subroutine starting at line 11 C = [A × 0.5] Print out at monitor screen: C “will be deducted from your tax” Count for seconds 10 Go to (next section of tax instructions) 11 Print out at monitor screen: “You cannot deduct this from your taxes” 430 Radiography in the Digital Age Figure 28-1 A typical microprocessor for a personal computer (PC) This is the CPU 12 Wait for “ENTER” command 13 Go to (next section of tax instructions) The part of a computer that interprets and executes instructions is called the central processing unit, or CPU A CPU that is contained on a single integrated circuit chip is called a microprocessor (Fig 28-1) The microprocessor is the heart of the computer We think of the power of a computer in terms of how much data it can input, process and output in a given amount of time The unit for this is millions of instructions per second, or MIPS Actual processing speeds range from hundreds of MIPS for microcomputers to thousands of MIPS for mainframe computers This overall power is determined primarily by the speed of the microprocessor This speed is determined, in turn, by an internal clock The faster the clock, the faster the processing Recall from Chapters and that the unit for frequency is the hertz, defined as one cycle per second For an analog clock, one cycle represents the completion of one circle around its face by the clock’s hand The speed of a microprocessor is expressed as the rate of cycles the clock can complete or count each second As with all other aspects of computers, we have seen this rate increase exponentially over time: Once measured in kilohertz and then megahertz, we now talk of the speed of microprocessors in common PC’s in units of gigahertz (billions of cycles per second) and terahertz (trillions of cycles per second) Perhaps the most common way to classify computers is by their size We generally think of a computer as the “PC” (personal computer) that fits on our desk at home Several decades ago, the computing power of a modern PC required a computer as large as an entire room All of the computing power of the lunar module which landed on the moon is now contained within a small hand-held calculator As miniaturization in electronics continues to progress, it becomes more difficult to make clear distinctions between sizes of computers, and the “size” of the computational power is more pertinent than the physical size in application With the understanding that some overlapping of terms is unavoidable, we can broadly categorize the sizes of computers as follows: Microcomputers usually have one single microprocessor, and generally fit on a desktop such as a PC (personal computer) or “notebook” computer Minicomputers contain many microprocessors that work in tandem, and are too large and heavy to be placed on a desktop The smallest minicomputers occupy a single cabinet ranging in sizes comparable to various refrigerators, placed on the floor Larger minicomputers can occupy three or four large cabinets taking up a portion of a room CT and MRI computers are examples of minicomputers Mainframe computers and supercomputers consist of microprocessors numbering in the hundreds or even thousands, and can support thousands of users They require the space of an entire room or even a whole floor of a building They are used in telecommunications companies, military and government organizations, airlines, and weather forecasting applications, to name a few The operating console of a standard diagnostic xray machine is essentially a microcomputer, with about the same overall processing power as a PC, but with all that power dedicated to the selection of proper radiographic technique while compensating for electronic and other variables THE DEVELOPMENT OF COMPUTERS Tools for performing mathematical calculations date back thousands of years to the abacus, invented in Computer Basics 431 Figure 28-2 An abacus, the earliest known computing device, used in Asia for thousands of years China The abacus consisted of a frame containing columns of beads separated by a crossbar (Fig 28-2) Each column held five beads below the crossbar, representing ones, and two above the crossbar representing fives Each whole column represented a power of 10 above the column to its right, such that 13 columns could represent numbers reaching into the trillions Equally impressive, the abacus could be used not only for all four standard mathematical operations, but also to calculate square roots and cube roots The first major step in the evolution of a completely automatic, general purpose, digital computer was taken by an English mathematician, Charles Babbage, in 1830 when he began to build his analytical engine One hundred years ahead of his time, the limitations of technology prevented Babbage from completing the machine in his lifetime Meanwhile, another English mathematician, George Boole, devised a system of formulating logical statements symbolically which led to the design of switching circuits in the arithmetic/logic units of electronic computers After Babbage’s death in 1871, no significant progress was made in automatic computation until 1937 when American professor Howard Aiken began building his Mark I digital computer Completed in 1944, it was the realization of Babbage’s dream, but the Mark I still contained some components that were mechanical rather than electronic It could perform up to five arithmetic operations per second The first fully electronic digital computer was completed at the University of Pennsylvania in 1946 by J Presper Eckert and John Mauchly Called the Electronic Numerical Integrator and Calculator (ENIAC), it consisted of 18,000 vacuum tubes (Figs 28-4 & 28-6), weighed 30 tons, and took up 1500 square feet of floor space (Fig 28-3) It could perform 5000 arithmetic operations per second This same year, John Von Neumann, a Hungarian-born American mathematician, published an article proposing that entire programs could be coded as numbers and stored with the data in a computer’s memory Almost everything he suggested was incorporated into the EDVAC (Electronic Discrete Variable Automatic Computer) designed by Eckert and Mauchly’s new company This was the first stored-program digital computer, completed in 1949 In the meantime, a breakthrough in computer hardware took place in 1948 with the development Figure 28-3 The first electronic digital computer, the ENIAC, took 1500 square feet of floor space and weighed 30 tons (U.S Army photo.) 432 Radiography in the Digital Age of the first transistor at Bell Telephone Laboratories The transistor (Fig 28-7), is a very small electronic (rather than mechanical) switch, which alternately allows or does not allow electrical current to pass through it Eckert and Mauchly quickly integrated the transistor with their basic EDVAC design to produce the much more advanced UNIVAC I (Universal Automatic Computer), completed in 1951 The UNIVAC was mass-produced within a few years and became the first commercially available computer Unlike earlier computers, it handled numbers and alphabetical characters equally well, and was the first computer to separate input and output operations from the central computing unit (Fig 28-5) The UNIVAC I used both vacuum tubes (Fig 28-6), and transistors (Fig 28-7) Both the vacuum tube and the transistor are able to represent binary digits, or bits of computer language, by simply allowing the two states of being switched on or off (The “on” condition indicates a “yes” or the number 1, and the “off ” state indicates a “no” or the number 0.) But, vacuum tubes were bulky, and the heated filaments would often burn out just as light bulb filaments do, making them very unreliable indeed The transistor allowed two critical developments to evolve: First, by the miniaturization of memory components, the size and weight of computers dropped dramatically, facilitating their mass production, their portability, and their use More importantly, memory components were now solid state, based on small crystals rather than on heated wire filaments—this lengthened their life span as much as 100 times, and also dramatically reduced the electrical power needed to run the computer The economy and efficiency of computing skyrocketed Therefore, the solid state transistor is perhaps the single most important invention in history for the development of computer hardware Since 1951, computers are considered to have evolved through at least four generations based on continued radical improvements in technology These Figure 28-5 Figure 28-6 The UNIVAC was the first mass-marketed computer, and the first to separate input/output modules from the main computer (U.S Navy photo.) Vacuum tubes, with cathode pins and anode plates (arrows) Tubes like these were the earliest switching elements in computers Figure 28-4 A technician replacing a burned-out vacuum tube, one of 18,000 such tubes in the ENIAC (U.S Army photo.) Computer Basics 433 Figure 28-7 Various sizes of solid-state transistors The transistor, used as a switching element, was perhaps the single most important development in the evolution of computers (Courtesy, Tom O’Hara, PhD.) generations are briefly defined in Table 28-1 Since the invention of the transistor, most advancements have been made in the area of miniaturization In the mid-1960s a method was developed in which hundreds of miniaturized components could be chemically fused onto a small silicon chip, typically about cm in size, to form microscopic circuits These came to be known as integrated circuits Silicon is a semiconductor—it can be doped by other chemicals to make it conduct, resist, or block the flow of electricity By introducing chemical impurities such as aluminum or boron in specific arrangements, microscopic capacitors, diodes, resistors, and transistors can be created Specific areas of the chip are treated with various chemicals to serve these functions With these areas in mind, the particular circuit is first mapped out on a large board Special photography is used to reduced the pattern to microscopic size, form a photographic negative and project the pattern onto the silicon chip More chemical impurities are baked into specified portions of the wafer to complete the circuit Further advancements in this miniaturization process have led to microprocessors which now contain millions of circuit elements within a square centimeter of silicon COMPUTER HARDWARE COMPONENTS The hardware of the computer consists of all the physical components, including input devices, the Table 28-1 Generations of Computers Generation Logic and Memory Circuit Components Generally Available 1st: Vacuum Tubes for both: Conducting = filament heated = “on” 1951 2nd: Transistors for logic: Conduction = silicon charged = “on” Magnetic cores for memory 1958 3rd: Integrated Circuits: Miniaturized components chemically fused onto a small silicon chip in microscopic circuits 1965 4th: Microchips: Enhanced miniaturization of integrated circuits Large-Scale Integration (LSI) = thousands of elements Very Large Scale Integration (VLSI) = millions of circuit elements onto a cm chip 1970s 1990s 434 Radiography in the Digital Age processing system, memory and storage devices, output devices and systems for communication These physical components are connected as shown in Figure 28-8 From this diagram, it is clear that there is a flow of information from input, output, and memory storage devices to the central processing unit or CPU This flow of data is carried by a multiwire line called a bus The connections of bus lines to each of the devices are called ports Serial ports transmit data sequentially one bit at a time The common USB (Universal Serial Bus) has several transmission wires and prongs so that it can transmit several data streams simultaneously, however, each of these channels still uses a serial protocol, hence its name Input/output or I/O devices, also called peripherals, transmit data to and from the computer Input devices include the keyboard, the mouse, the trackball, the joystick, the touchpad, and the light pen Most of these are pointing devices which con- trol the location of the cursor (usually an arrow), which indicates the insertion point on the screen where data may be entered These devices all require the user to enter information one character or menu selection at a time, and are somewhat slow In order to more quickly copy information directly from a document, or from an audio or visual scene, source-data entry devices were developed These include bar code readers, scanners and fax machines, sensors, microphones, and digital cameras and camcorders Output devices include printers, display screens and speaker systems The display screen or monitor is typically a liquid crystal display (LCD)—two plates of glass with a substance between them that can be activated in different ways to make the crystals appear lighter or darker To create smooth-looking letters and numbers on a monitor screen, a character generator is used to illuminate selected dots in a × matrix for each character Figure 28-8 Workstation Computer CPU OUTPUT INPUT Additional primary memory Laser camera Optical jukebox External storage The central processing unit directs data flow from input devices, between primary and secondary memory and the arithmetic/ logic unit, and to output devices Computer Basics A video display terminal (VDT) uses a keyboard and mouse or trackball for input, and a display screen for output A dumb terminal cannot any processing on its own, but is used only to input or receive data from a host computer, such as is done at airport check-in counters An intelligent terminal has builtin processing capability and memory, but does not have its own substantial storage capacity Most x-ray machine consoles would be categorized as intelligent terminals Most modern printers are either ink-jet printers or laser printers Ink-jet printers place an electric charge onto small drops of ink that are then sprayed onto the page Laser printers form an image on a drum which is then treated with a magnetically charged ink-like substance called toner, and then transferred from the drum to paper While ink-jet printers are quieter and less expensive, they can print only 10 to 20 pages per minute Laser printers have their own memory to store such information as fonts separate from the computer, and their own limited data processor They provide sharper resolution in the image (up to 475 dots per cm), and can print from 32 to 120 pages per minute depending on the power of the computer they are connected to Most radiographic images are viewed as soft copies on the LCD monitor screen Sometimes it is desirable to print them out on transparent plastic film which can be on an illuminator or viewbox for examination, or physically carried from place to place Images or text that have been printed onto paper or plastic film are referred to as hard copies The Central Processing Unit The central processing unit (CPU) performs data manipulation in the computer It tells the computer how to carry out software instructions The CPU for a mainframe computer may be large enough to occupy its own separate cabinet, while the CPU for a typical PC is usually a single microprocessor All CPU’s may be divided into two basic components: The control unit, and the arithmetic/logic unit These two operate on information and data retrieved from a primary memory storage system The control unit directs the flow of data between the primary memory and the arithmetic/logic unit, 435 as well as between input devices, the CPU, and output devices The control unit is analogous to a traffic cop directing the flow of traffic through an intersection It tells input devices when to start and stop transferring data to the primary memory It also tells the primary memory unit when to start and stop transferring data to output devices The control unit coordinates the operations of the entire computer according to instructions in the primary memory It is programmed to select these instructions in proper order, interpret them, and relay commands between the primary memory and the arithmetic/logic unit Each set of instructions is expressed through an operation code that specifies exactly what must be done to complete each task The operation code also provides addresses that tell where the data for each processing operation are stored in the memory Somewhat like a very sophisticated hand-held calculator, the arithmetic/logic unit (ALU) performs all the arithmetic calculations and logic functions required to solve a problem Data to be operated upon must be retrieved from addresses in memory, and are temporarily held in the ALU’s own storage devices called registers These registers are connected to circuits containing transistors and other switching devices To perform arithmetic and logic operations, electrical signals must pass through three basic circuits called the AND-gate, the OR-gate, and the NOT-gate, used in different combinations One combination of these gates results in subtraction, another selects the larger of two numbers, and so on The result of a calculation is first stored in the ALU’s main register called the accumulator Results may then be exported from the accumulator to internal or external memory, or directly to an output device such as a display screen Primary memory is also referred to as main memory or internal memory, mostly stored on chips Four sectors of primary memory space are reserved for distinct functions as follows: The program storage area retains program statements for a specific application, transferred from an input device or secondary storage Upon the request of the control unit, these instructions are “read” and executed one at a 436 Radiography in the Digital Age time to perform the operations of a saved program The working storage or scratch-pad storage area temporarily holds data that is being processed by the arithmetic/logic unit, and intermediate results There is a designated temporary storage area for data received from input devices which is waiting to be processed There is a designated temporary storage area for processed data waiting to be sent to output devices The unit for measuring storage capacity is one byte, consisting of eight bits (binary digits) of information The significance of this number is that eight bits are sufficient to create a single character which can represent almost any alphabetical letter, number, other value or symbol needed to communicate The bit, an acronym for binary digit, is the smallest unit of storage, consisting of a or An address is assigned to each permanent character stored within the memory Therefore, each address consists of eight storage units, whether all of them are needed or not to contain a particular character Just as the number of a particular mail box at the post office has nothing to with what is contained therein, the addresses within computer memory are only designated locations where bytes are stored, and have nothing to with the particular character stored there They are necessary for the control unit to locate each character when it is needed Physically, most primary memory is contained in RAM (random access memory) and ROM (readonly memory) chips mounted on boards and connected directly to the CPU Most computers have slots for additional boards of RAM chips to be inserted (Fig 28-9) which generally speeds up the computer’s response time The motherboard or system board is the main circuit board for a computer, usually the largest board within the casing (Fig 28-10) It anchors the microprocessor (CPU), RAM and ROM chips and other types of memory, and expansion slots for additional circuit boards such as video and audio cards that enhance specific capabilities of the computer The power supply for a computer must be carefully controlled Most computer circuits are designed to operate at volts or 12 volts A power supply box (Fig 28-11), includes a step-down transformer (Chapter 7) and resistors used to reduce the voltage of incoming electricity to levels that will not burn out delicate computer components Additional resistors leading into specific devices may be found on the motherboard Computer components also require a steady, reliable supply of power that will not be immediately affected by split-second interruptions, reductions or surges in the incoming electricity supply For this purpose, numerous capacitors may be found on the motherboard, which store up incoming electrical charge and then release it in a controlled, constant stream Figure 28-11 gives a broad overview of the major components one will see upon opening the processor casing for a typical PC These include the power supply, optical disc drives (CD and DVD) and flash memory drive, and the motherboard with the CPU (microprocessor), banks of RAM chips and slots for additional memory, banks of ROM chips, and various attached cards containing audio, video, and modem circuits Figure 28-9 RAM chips mounted on a removable board Index G Gamma radiation, 12, 68 Gauss, 106 Gauss’ law, 106 Generators, 124, 138, 263 battery-powered, 265 constant potential, 265 electrical, 124 high-frequency, 140, 264 kVp, effective, 264 mobile units, 265, 671 power rating, 140 sharpness, 265 single-phase, 138, 263 three-phase, 139, 263 x-ray beam spectrum, 174 x-ray production, 174 Genetically significant dose, 724 Geometric integrity, 225 Geometric variables, 182 Gradation processing, see Postprocessing, gradation processing Graphs, 40 Gravity, 18 Gray level, pixel, 457, 463 Gray scale, 215, 463 contrast, relation, 215 digital image processing, 493 kVp, 250 penetration, 214, 250 Gray, unit, 717 Grids, 304, 586 Aliasing, 586 alignment, 314 bucky factor, 310 canting, 312 construction, 304 contrast improvement factor, 310 convergent point, 312 cut-off, 312 digital fluoroscopy, 688 digital imaging, use of, 586 effectiveness, effiiciency, 306, 309 measuring, 309 exposure, 310 focused, 312 frequency, 307 historical, 11, 304 indications for use, 308, 586, 587 kVp, 309 lead content, 307 line suppression, 530 lines, 305, 312 Moire artifact, 586 mottle, 587 oscillating, 306 parallel, 313 part thickness, 308 Potter-Bucky mechanism, 11, 305 radius, 312 ratio, 306 reciprocating, 306 reducing use, 587 scatter, 304 selectivity, 310 stationary, 305, 312 subject contrast, 307 technique conversions, 311 virtual grid software, 308, 588 Ground state, atomic, 167 nuclear, 66 Grounding, electrical, 107 H Habitus, body, 287 Half-life, radioactivity, 709 Half-value layer, 267, 655 Halo effect, 555 Heat, 25 Heat dissipation, x-ray tube, 26, 152, 169 Heat units, calculating, 157 Heel effect, anode, 323 Henry, J., 122 Hertz, H., 93 Hertz, unit, 75 Heterogeneity, x-ray beam, 164 High-frequency generators, 140, 263 Histogram, 46, 482 analysis, 486 characteristic curve, 487, 555 scatter, effects, 578 History of x-rays, Hospital information system (HIS), 451, 647 I Illuminance, 663 Illumination, room, 664 Image Analog, 443 analysis, 377 artifacts, 220, 619 brightness, 213 855 856 Radiography in the Digital Age components, 211, 213 compression, 643 contrast, 211, 215, see contrast controlling factors, 560 criteria for digital image quality, 557 density, hard copy images, 213 digital, see Digital image display monitors, 627 distortion, 227, 234, see Distortion electronic, 627 fluoroscopic, see Fluoroscopy fog, see Fog gray scale, 215 magnification, 227, 231, see magnification matrix, 457, 612 negative, 214 noise, 213, 216, 217, see Noise pixels, 459 brightness, 461, 465, 491 gray level, 461, 465, 491 pitch, 611 size, 457, 460, 611, 612, 616 positive, 213 processing, see Processing, digital production, 181, 197 qualities, digital, 557 general, 211 hierarchy of, 236 recognizability, 225 resolution, 236, 381, 459 saturation, 449, 450 shape distortion, see Distortion sharpness, 225, 229, see Sharpness signal-to-noise ratio, 217, 242, 562, 574 unsharpness, 227, see Unsharpness visibility, 211 windowing, 468, 505, 553 window level, 468 window width, 468 Image intensifier, 9, 676 anode, accelerating, 677 brightness gain, 678 conversion factor, 678 development of, 9, 674 fiber optic bundle, 690 flux gain, 678 focusing lens, electrostatic, 676 input phosphor, 676 magnification mode, 678 minification, 677, 679 multifield, 678 output phosphor, 678 photocathode, 676 Image receptors, 599 CR, 604 DR, 599 Immobilization, 361 Incoherent scatter, see Compton scatter Induction electromagnetic, 102, 123, 124, 437 electrostatic, 109 motor, 125 Informatics, medical imaging, 646 Infrared radiation, 85, 169 Insulators, electrical, 115 Intensifying screens, 10 Intensity beam, x-ray, 239 distribution, heel effect, 266, 323 light, 211 milliamperage, 239 rate, 239 Interactions anode, 164 atomic number, 152, 200, 291 bremsstrahlung, 164 characteristic, 167 in patient, 189 in x-ray tube, 167 coherent scatter, 188 Rayleigh, 1885 Thompson, 188 Compton effect, 185 compton/photoelectric ratio, 202 contrast agents, 290 density, physical, 200 energy, x-ray beam, 202 patient, within, 183 photoelectric, 184 tissue, 204 x-ray tube, 164 Interface, 87 Interference, wave patterns, 94 Inverse Square Law, 38, 75, 339 formula, 340 scatter, 352 Ion pair, 63, 602 Ions, 62, 759 Ionic bonding, 61 Ionization, 12, 62 electroscope, 110, 732 Isomer, 68, 709 Isometric Angles, 363 Isotopes, 65, 66 Index J Jackson focus tube, 10 Joule, 20 K Kassabian, M.K., 700 K-edge effect, 617 Digital subtraction, 689 Kernels, 500, 511, 516, 524 Key operator functions, CR, 539 Kilovoltage, 249 average, 166, 172, 173, 174 compton scatter, 202 contrast, digital image, 576 contrast, subject, 202, 205, 250 control, kVp, 134 meter, kVp, 137 digital image, effects, 578 effective, 264 energy, x-ray beam, 249 fifteen percent rule, 252 fixed, see optimum kVp technique fixed kVp approach, 390 fog, 256 gray scale, 250 grids, 309 high kVp technique, 566 scatter, 566 mottle, 568 intensity, x-ray beam, 172 interactions, ratio between, 202 line-voltage compensator, 133 minimum, 251 optimum kVp technique, 254, 258, 412 patient exposure, 255, 796 peak, 249 penetration, x-ray, 250 photoelectric interaction, 202 quality control, 657 scatter radiation, 256, 302 spectrum, x-ray beam, 172 subject contrast, 202, 205, 250 sufficient, 250 variable kVp technique, 390, 392 wavelength, x-ray, 79 x-ray production, 172 kVp, see Kilovoltage Kinetic energy, 22, 163 L Laser film digitizers, 89 film printers, 90 optical disc storage, 90 Lasers, 87 CR reader, 88, 607 Latent image, 377 Latitude, exposure, 576 Lenz, H., 126 Lenz’ law, 126 Light, visible, 91 diffusion, 92 dispersion, 92 focusing, 92 reflection, 91 refraction, 92 vs x-rays, 91 Lighting, ambient, 664 Line-focus principle, 155, 321 Line-pairs per millimeter, 383, 611 Line voltage compensator, 133 Linear energy transfer (LET), 765 Linearity, mA, 654 Liquid crystal display (LCD), 627 active matrix, 629 advantages, 627, 632 disadvantages, 632 dot pitch, 630 lag, 629 nematic liquid crystals, 627 passive matrix, 628 pixels, 634 dead pixels, 632, 665 nature of, 634 pitch, 630 states (on and off), 628 stuck pixels, 632, 665 subpixels, 634 polarization of light, 627 polarizing lenses, 627 refresh time, 629 response time, 629 subpixels, 634 viewing angle dependency, 627, 633, 666 Look-up tables, 502 function curves, 502 permanent, for rescaling, 491 variable, for gradation processing, 502 Luminance, 633, 662, 663 Luminescence, 606 857 858 Radiography in the Digital Age M mA, see milliamperage mA control, 136 meter, 137 mAs, see Milliampere-seconds Machine phase, see Generators Macroradiography, 354 Magnets, 104 electromagnet, 105 gauss, 106 gauss’ law, 106 permeability, 104 retentivity, 104 tesla, 106 Magnetic dipole, 103 domain, 104 fields, 81, 101, 105 materials, types of, 101 moment, 103 Magnetic resonance imaging, 85 Magnetism, 101 Magnification, 227, 231 factor, 233, 354 focal spot, 330 formula, 232 fluoroscopic, 678 object-image receptor distance, 352 percentage, 233 ratio, 231, 354 SID/SOD ratio, 232, 354 source-image receptor distance, 336 variables, 379 Magnification technique, 337, 354 Maiman, T.H., 87 Markers, 537, 590 mA, see Milliamperage mAs, see Milliampere-seconds mAs calculations, 241 mA/time combinations, 239 Mass, 17, 53 Math areas and volumes, 37 basic operations, 32 dimensional analysis, 35 graphs, 40 inverse square law, 38 scientific notation, 34 terminology, 31 unit conversions, 35 Matter, 53 dual nature of, 93 states of, 23 Measurability, Measurement, standards of, 17 Medical imaging informatics, 646 Mendeleyev, D., 57 Metadata, 642 Meters, x-ray circuit, 137 Microwaves, 84 Matrix, digital image, 457, 612 Milliamperage, 137, 147, 239 effective mA, 263 mA meter,138 mA/time relation, 240 optimum, 412 quality control, 654 Milliampere, (mA), 116 Milliampere-seconds, 116, 239 calculating, 240 exposure, 239 intensity, 239 mA/time combinations, 240 spectrum, x-ray beam,171 underexposure and quantum mottle, 242 Minimum change rule, 286, 414 Mixture, 53 Mobile fluoroscopy, 684, 813 Mobile radiography, 671 alignment and positioning, 672 distance, 672 generators, 265, 671 geometrical factors, 672 mAs selection, 672 technique charts, 674 Modified scatter, see Compton scatter Modulation transfer function, 382 Moire artifact, see Aliasing Molecule, 53 Morgan, R.H., 10, 411 Motion, 370 contrast, 372 distortion, 372 false images, 372 generators, 265 penumbra 371 sharpness, 226, 371 time, exposure, 244, 372 Motor, electric, 124 induction, 125 Mottle, 216, 242 centering for DR, 590 digital systems, 516, 524, 586, 587, 590 electronic, 217, 242, 681 fluoroscopic scintillation, 681 quantum, 242 signal-to-noise ratio, 242 Index underexposure and, 242 N National Council on Radiation Protection (NCRP), 817 Natural frequency, 83 Neutron, 57, 65 Newton, Isaac, 91 Noise, 213, 216 algorithmic, 217 artifacts & casts, 297 electronic, 217, 242, 681 false images, 373 fluoroscopic, 681 grid lines, 305, 312 reduction for del drop-out, 480 interpolation, 480 kernels, 480 scatter radiation, 188, see Scatter radiation signal-noise ratio, 218, 681 variables, 378 Noise reduction, digital, 516, 524 Nomenclature, radiography 181 Non-conserved quantities, 20 Nuclear fission, 65 Nuclear forces, 18 Nuclear fusion, 65 Nucleons, 64 Nucleus, atomic 64 Nyquist frequency, 611 O Object-image receptor distance, 182, 349 air-gap technique, 351 distortion, 354 exposure, 352 long OID technique, 354 macroradiography, 354 magnification, 352 scatter, 350 sharpness, 352 subject contrast, 349 Observation, scientific, Octet rule, 59 Oersted, H.C., 101 Off-centering, see Alignment, beam-part-film Off-focus radiation, 274 Ohm, 118 Ohm’s law, 119 Okham, William of, 17 Optical disc storage, 90 Optimum kilovoltage technique, 254, 258, 412 Optimum milliamperage, 412 Orbitals, atomic, 55, 56, 60 Overcollimation, 275, 583, 590 Overexposure, 243, 576 saturation, 549, 550 Oxygen enhancement ratio, (OER), 769 P Pascal, B., 24 Parsimony, scientific, 5, 17 Part grids, 308 measurement of, 283, 401 scatter radiation, 303 thickness, 191, 199, 283, 303, 362 shape, 362, 396 Pathology, 293 additive, 294 destructive, 294 trauma, 295 Patient age, 289 anthropology, 289 average thickness, 284, 396 casts and splints, 297 condition, 283 contrast agents, 290 disease, see Pathology exposure, 543, 566, 571, 576, 794 ALARA philosophy, 13, 266, 725 automatic exposure control (AEC), 800 exposure levels, diagnostic, 794 field size, 797 fifteen percent rule, 255, 575 filters, 265, 797 fluoroscopic, 685 generators/machine phase, 797 genetically significant dose (GSD), 724 gonadal exposure levels, 796 grids, 797 half-value layer (HVL), 800 image receptors, 797 kVp, 173, 255, 390, 796 mAs, 796 positioning, 798 speed class, digital, 800 technique, radiographic, 566, 800 quality control and, 798 habitus, 287 molecular composition, 290 pathology, 293 859 860 Radiography in the Digital Age physique, 287 post-mortem, 295 radiation protection elective scheduling, 801 equipment guidelines, 802 fluoroscope technology, 685, 803 pulse width, 804 issues, current, 805 pregnancy, policies, 801 shielding, 801 respiration, 292 soft tissue technique, 296 thickness, 191, 199, 283 tissue composition, 290 trauma 295 Penetration, x-ray beam, 191 CR and DR, 577 energy, beam, 250 filtration, 166, 266 generators, 264 gray scale, 214, 250 half-value layer, 267, 655 kilovoltage, 250 sufficient, 191, 214, 250, 577 tissue types, 251 Penumbra, 226, 327 absorption, 379 diagrams, 228, 379 focal spot, 327 geometrical, 226, 329, 380 motion, 226 total, 381 vs scatter, 303 also see sharpness Periodic table of the elements, 57 Phase, machine, see generators spectrum, x-ray beam, 174 x-ray production, 174 Phosphor, CR, 604 Efficiency, 610 Absorption, 616 Conversion, 616 Emission, 616 k-edge effect, 617 Phosphorescence, 606 Photocathode, 608, 676, 728 Photoconductivity, 93 Photoelectric effect / interaction, 93, 184, 608 Photoelectric/compton ratio, 202 Photoelectron, 184 Photomultiplier tube, 608, 728 Photon, 93 Photospot camera, digital, 675, 683 Photostimulable phosphor imaging, 88, 605 Phototimers, see automatic exposure controls Picture archival and communication systems (PACS), 450, 639 access, image, 643 accession number, 648 compression, image 643 control computer, 641 copying images, 643 development, 11 DICOM (Digital Imaging and Communications in Medicine) standard, 642 DICOM header, 642 DICOM viewers, 646 functions, 642 local area networks (LANS), 451, 641 metadata, 642 optical jukebox, 641, 643 prefetching, 643 RAID (Redundant Array of Independent Discs), 646 resolution, loss of, 643 RIS/HIS, 451, 647 service class, 641 storage area network (SAN), 646 storage capacity, 643 wide area network (WANS), 450, 641 workstation, 470, 627, 639 Pincushion distortion, fluoroscopic, 683 Pitting, anode, 156 Pitch, dexel, 611 dot, 630 pixel, 611, 630 Pixel, 459 brightness, 459, 461, 465, 493 dead, 632 formula for size, 612 gray level, 459, 461, 465, 493 nature of, 634 pitch, 611, 630 size, 459, 611, 612, 614 stuck, 632 subpixels, 634 Pixel-shifting, 689 Pixel size formula, 460, 612 field-of-view, 612 matrix, 460, 612 spatial resolution, 460, 612 Plank formula, 79 Plank, M., 79, 95, 184 Pocket dosimeter, 732 Positioning, 370 Standardization of, 391 Positive beam limitation, 273, 274 Postprocessing, digital, 499, 539 Index background suppression, 512 band-pass filtering, 522 data clipping, 508 definition of, 478 detail processing, 511 edge enhancement, 512, 523, 554 enhanced visualization processing (EVP), 523 filtering, high-pass, 523 low-pass, 523 unsharp mask, 512 Fourier transformation, 520 inverse, 521 frequencies, image, 516 frequency domain, 516 frequency processing, 517 parameters, 522 kernels, 500, 511, 516, 524 multiscale processing, 522 pyramidal decomposition, 522 smoothing, 512, 554 spatial domain, 511 spatial processing, 511 kernels, 511 point processing, 500 display, preparation for, 524, 527 dual energy subtraction, 529 dynamic range compression/control, 509 edge enhancement, 512, 523, 554 enhanced visualization processing, 523 equalization, tissue, 510 gradation/gradient processing, 502, 526 gray scale curve, 502 intensity transformations, 505 look-up tables, 502 parameters, 505 halo effect, 555 kernels, 500, 511, 516, 524 look-up tables, 502 function curves, 503 permanent, for rescaling, 491 variable, 503 mottle, corrections for, 525 noise reduction, 524 operator adjustments, 529 perceptual tone scaling (PTS), 526 spatial operations, 500 special postprocessing, 529 dual energy subtraction, 529 grid line suppression, 530 suites, digital processing, 527 tissue equalization, 510 unsharp-mask filtering, 512 Postprocessing in practice, 539 alternative algorithms, 551 criteria for digital image quality, 557 dark masking, 556 edge enhancement, 554 exposure indicators, 542 errors, 550 exposure parameters, 548 image reversal, 506, 557 image stitching, 557 menu screens, navigating, 539 resizing, 557 smoothing, 511, 554 speed class, 541 windowing, 553 Potential bridge, 135 Potential difference, electrical, 108, 117 Potential energy, 21 Potter-Bucky diaphragm or grid, 10, 305 Potter, Hollis, 10, 305 Power, 119 electrical, 119, 127 rating, generators, 140 Preprocessing, digital, 477 anode heel effect, 479 definition of, 478 drop-out, dexel, 480 exposure field recognition, 482 field uniformity corrections, 479 dark noise, 479 dexel drop-out, 480 electronic response & gain offsets, 479 flat field corrections, 479 light guide variations, CR, 480 scintillator thickness, variable, 479 image analysis, 481 exposure field recognition, 482 histogram, 482 analysis, types of 486, 488 construction, 482 errors, 488 gray scale curve, 487 overcollimation, 487 values (volume) of interest (VOI), 483 look-up tables, permanent, for rescaling, 491 partitioned pattern recognition, see segmentation noise reduction for del drop-out, 480 interpolation, 480 kernels, 480 rescaling, 490 LUT, permanent, 491 Q values, 491, 495 re-mapping, 493 S values, 492 861 862 Radiography in the Digital Age physicists’ terminology, 495 segmentation, 481 errors, 590 uniformity, field, 478 Prereading voltmeter, 137 Pressure, liquid, 23 Primary beam, radiation, 181 Principal quantum number, 59 Processing, digital, see postprocessing, digital, and preprocessing, digital Processing, standardization of, 391 Programmed exposure controls, 423 Projection routines, 391 Proportional anatomy technique, 394, 585 Protection, radiation Patient, see Patient, radiation protection Personnel, 806 Proton, 57 Protraction of radiation dose, 768 Pupin, Michael, 10 Q Q values, 491, 495 Quality, x-ray beam, see also spectrum, beam Quality, image, 211, 225 criteria for digital image quality, 557 hierarchy of image qualities, 236 Quality assurance, 643 Quality control, 653 automatic exposure control, 659 beam alignment, 657 collimator, 657 digital system monitoring eraser system, 661 field uniformity, 660 intrinsic (dark) noise, 661 spatial resolution, 661 display systems, monitoring, 661 ambient lighting, 664 candela, 662 class of monitor, 662 contrast tests, 663 DICOM gray scale display function, 664 dead or stuck pixels, 665 grayscale standard display function (GSDF), 664 illuminance, 663 lumens, 662 luminance, 662 luminance ratio, 664 luminance tests, 663 noise, 664 photometer, 663 reflectance tests, 664 resolution, 664 stability, 666 steradians, 633, 662 test patterns, 665 viewbox, see illuminators viewing angle dependence, 633, 662 distance indicators, 657 equipment testing, 654 filtration, 655 fluoroscopic unit, 660 focal spot, 658 half-value layer, 267, 655 kilovoltage, 657 light field alignment, 657 milliamperage, 654 repeat analysis, 666 reproducibility, exposure, 655 timer, exposure, 654 Quantum, 23, 79, 93 Quantum mottle, 242 signal-to-noise ratio, 242 Quantum theory, physics, 23, 96 R Radar, 84 Radiation, 12 accidents, 13, 700, 703 background, 610, 702 bombs, 703 dual nature of, 93 electromagnetic, see Electromagnetic waves heat, 26 ionizing, 12 landmark amounts, 702 manmade, 705 medical, 702 natural, 8, 12, 702, 704 perceptions, public, 699 primary, 181 protection, see Protection, radiation remnant, 181 safety, 13, 699 scatter, see Scatter radiation sources, 704 manmade, 705 medical, 702, 706 natural, 8, 702, 704 types, 12 units and measurement, 715 ALARA, 13, 266, 725 becquerels, 721 Index coulomb per kilogram (C/kg), 716 biological effectiveness, 720 dose, absorbed, 717 dose area product, 718 dose equivalent limits (DELs), 722 exposure, 715 genetically significant dose, 724 gray, 716, 717 negligible individual dose, 724 sievert, 720 Systeme international, 715 weighting factors radiation, 720 tissue, 720 x-ray, see X-rays Radiation detection instruments, 725 accuracy, 727 annealing, 730 cascade effect, 734 continuous discharge, 738 control monitor, 736 film badges, 730 gas-filled detectors, 732 geiger-mueller tubes, 734 ion chambers, 733 modes of operation, 725 optically stimulated luminescence dosimeters, 729 personal monitors, 735 pocket dosimeters, 732 proportional counters, 734 range, 728 recombination 736 resolving time, 727 saturation, 734 scintillation detectors, 728 sensitivity, 725 thermoluminescent dosimeters (TLDs), 730 types, 728 voltage dependence, 736 Radiation perspectives, 699 Radiation protection, 793 agencies, advisory and regulatory, 817 ALARA, 13, 266, 725 areas, types of, 817 barrier shielding, 814 factors, 816 cardinal principles, 700, 807 dose equivalent limits (DELs), 722 dose limiting organs, 722 equipment guidelines, 802, 813 equipment shielding requirements, 811 exposure levels to patients, 794 gonadal exposure levels, patient, 796 holding of patients, 811 863 ICRP, 817 isoexposure curves, 808 lead aprons, 809 leakage, x-ray tube, 813 NCRP, 817 patient protection, see Patient, exposure and Patient, protection personnel protection, 806 cardinal principles, 700, 807 equipment guidelines, 813 equipment shielding requirements, 811 isoexposure curves, 808 monitoring, 806 policies, 811 policies for technologist pregnancy, 812 reports, radiation, 806 shielding requirements, 809 lead, effectiveness of, 809 posted warnings, 817 reports, radiation, 806 risks, comparative, by exam, 794 shielding, patient, 801 technique, optimum, 796, 800 AEC, 800 digital processing speed class, 800 field size limitation, 797 generators and filtration, 797 grids and image receptors, 797 mAs and kVp, 796 positioning, 798 quality control, 800 tenth value layer, 810 Radio AM, 83 FM, 83 waves, 83 Radioactivity, 8, 66, 707 alpha particles, 12, 67, 707 beta particles, 12, 57, 67, 707 beta decay, 57, 66 decay rate, 708 gamma rays, 12, 68, 708 half-life, 709 types, 707 units, 716 x-rays, 707 Radiography, development of, 6, 9, 11 safety of, 14, 699 Radioisotope, 66, 708 Radiology information system (RIS), 451, 647 Radiolucent, 92 Radionuclide, 66 Radiopaque, 92 864 Radiography in the Digital Age Radon, 13, 704 RAID, 438 Rare earth screens, 10 Rating charts, 156 Rayleigh interaction, 188 Rayleigh, J 188 Receptors, image, 599 CR phosphor plates, 604 detective quantum efficiency, 618 DR receptors, 600 direct conversion, 601 indirect conversion, 603 efficiency, 616 CR, 616 DR, 618 k-edge, 617 speed, inherent, CR, 542 Recognizability factors, image, 225 Recoil electron, 185 Recorded detail, see Sharpness of recorded detail Rectification, 134, 138, 263, see machine phase Rectifier, electronic, 134 bridge, 134 solid-state, 134 Redundant array of independent discs, 438 Reflectance tests, 664 Reflection, 87, 91 Refraction, 87, 92 Relative biological effectiveness (RBE), 766 Remnant beam, radiation, 181 Repeat analysis, 666 Reproducibility, exposure, 655 Reproducibility, scientific, Rescaling, 490 LUT, permanent, 491 Q values, 491, 495 re-mapping, 493 S values, 492 physicists’ terminology, 495 Resolution, 235, 381, 559 Contrast resolution, 384, 463, 465, 525, 682 detail processing, 511 exposure-trace diagrams, 380 fluoroscopic, 676 LCD, 635 microscopic, 382 modulation transfer function, 382 overall, 235, 381 spatial, 225, 383, 459 digital systems, 459 Resonance, 83 Respiration, 292 Ripple effect, 139, 264 Roentgen, Wilhelm Conrad, Rollins, William, 9, 273 Rotor, 124, 136, 147, 153 High-speed, 153 Rotoring, 136, 153, 158 Rutherford, E., 14, 57 S S-values, 492 Saturation, 449, 450 Scale, gray, see gray scale Scatter radiation, 301 causes, 302 coherent, 188 collimation, 275, 303 Compton, 185 CR plate, 610 digital image, effects on, 578 exposure, overall, 301 exposure, personnel, 811 levels, 807 shielding from, 809 field size, 275, 303 fog, see Fog grids, 304 incoherent, 185 inverse square law, 352 kVp, 256, 302, 566 modified, 185 OID, 350 Part thickness, 303 Rayleigh, 188 subject contrast, 201, 275 thickness, part, 303 Thompson, 188 unmodified, 188 vs blur, 303 Scientific method, Scientific notation, 34 Scintillation, fluoroscopic, 681 Screen cassette, 10 Segmentation, 481 errors, 590 Self-correction, scientific, Semiconductors, electronic, 115, 432 Shape distortion, see Distortion, shape Shape ratio, 234 Sharpness, 225, 229 CR systems, 611 digital systems, 519 focal spot, 327 formula, 229, 355 generators, 265 Index line-focus principle, 321 motion, 226, 371 object-image receptor distance, 352 positioning, 370 SOD/OID ratio, 228, 355 solving for, 225 source-image receptor distance, 336 source-object distance, 225, 355 time, exposure, 244 variables, 378 Shells, atomic, 57, 59 SID, 335, see Source-image receptor distance SID/SOD ratio, 233, 254 Sievert, 713 Signal/noise ratio, 218, 242, 566, 574 Single phase generators, 138, 263 Size distortion, see Magnification Smoothing, 512, 554 SOD, see Source-object distance SOD/OID ratio, 228, 355 Soft tissue technique, 296 Sonography, 87 Source-image receptor distance (SID), 182, 335 angled beam, 368 compensation for, technique, 341 distortion, 339, 368 estimating, 335 exposure, 339, 368 inverse square law, 38, 339 magnification, 336 measuring, 335 mobile radiography, 672 quality control, 657 rules of thumb, 344, 672 sharpness, 336 short SID technique, 337 square law, 341 technique adjustments, 341 technique rules of thumb, 344, 368 Source-object distance, macroradiography, 354 magnification, 354 sharpness, 355 Space charge, 147, 239 effect, 148 Spatial frequency, 382, 459 Spatial resolution, 225, 229, 382, 459 digital systems, 459, 519, 611 focal spot, 327 formula, 229, 355 generators, 265 line-focus principle, 321 motion, 226, 371 object-image receptor distance, 352 positioning, 370 SOD/OID ratio, 228, 355 solving for, 225 source-image receptor distance, 336 source-object distance, 225, 355 time, exposure, 244 variables, 378 Spectrum, electromagnetic, 82 Spectrum, x-ray beam, 44, 166, 167, 170, 267 filtration, 172, 267 generators/machine phase, 174, 267 kVp, 172 mAs, 171 target material, 170 Speed CR receptor, inherent, 542 Speed class, digital, 541 Spin, atomic particles, 101 electron, 60, 81 Spot-filming, fluoroscopic photospot cameras, 675, 683 technique, 681 Square law, 341 Standardizing radiographic technique, 391 States of matter, 23 thresholds for, 25 Static electricity, 107 Stationary grids, 305, 312 Steradians, 633, 662 Subject contrast, 164, 190, 197 atomic number, tissue, 200 attenuation, 190, 197 collimation, 273 compton/photoelectric ratio, 202 contrast agents, 204, 290 density, physical tissue, 200 field size, 273 gray scale, 215 grids, 307 kilovoltage, 202, 205, 249 motion, 372 object-image receptor distance, 349 photoelectric interaction, 184 photoelectric/compton ratio, 202 scatter radiation, 201, 273 soft tissue technique, 296 thickness, tissue, 190, 199 tissue types, 204, 290 variables, 378 x-ray beam, 164 energy, 202 Suborbitals, see orbitals Suppixels, 634 865 866 Radiography in the Digital Age Subtraction, digital, 688 Energy subtraction, 689 k-edge, 689 mis-registration, 689 pixel-shifting, 689 temporal subtraction, 688 time-interval difference mode, 689 Subtraction, dual energy, 689 filtration method, 689 kVp method, 689 T T-Triangle, for: electromagnetic waves, 78 waves, 77 Ohm’s law, 119 Power law, 120 Tabletop-tube distance, 368 Target, anode, 170 Technique body shape, 396 casts and splints, 297 charts, see Technique charts digital imaging, application to, 565, 576 signal-to-noise ratio (SNR), 218, 242, 566, 574 fixed kilovoltage, 392 fluoroscopic, 681 four centimeter rule, 190, 199, 286 fifteen percent rule, 252 grid factors, 311 high-kVp technique, 566 mottle, 568 scatter, 566 latitude, exposure, 576 manual, 417, 585 mobile radiography, 671 myths, digital, 584 optimum kilovoltage, 254, 258, 412 part thickness, 283 patient exposure, 566, 575 post-mortem, 295 programmed exposure controls, 423 proportional anatomy, 394, 585 saturation, 549, 550 soft tissue, 296 SID, rules of thumb for, 344, 672 simplifying and standardizing, 391 variable kilovoltage, 392, 393 Technique by proportional anatomy, 394 digital applications, 585 Technique charts, 398, 569 automatic exposure, 421 developing, 401 digital, 569 formats, 398, 401 manual, 398 mobile, 406 patient exposure, 398 proportional anatomy, 394 Teleradiology, digital, 11, 450 Temperature, 25 Tesla, 115, 126 Thermionic emission, 9, 135, 147, 239 Thickness, body, 283 Attenuation, 190, 199 average ranges, 284, 396 compensation for, 285, 396 distortion, 362 four centimeter rule, 190, 199, 286, 396 measurement of, 284, 401 scatter radiation, 303 subject contrast, 199 Thin film transistors (TFTs), 601, 629, 687, 691 Thompson effect / interaction, 188 Thompson, J.J., 188 Three-Mile Island power plant, 13, 700, 703 Three-phase generators, 139, 263 Thyratron, 142, 414 Time, exposure, 239 Exposure, 239 fluoroscopic, 802 mA-time relation, 240 motion, 244 see also timers Timers, exposure, 141 AEC, 141 back-up, 412 fluoroscopy, 802 mAs, 141 quality control, 674 Tissue, Atomic number, 200 Composition, 290 Contrast, subject, 204, 290 Density, physical, 200 Differential absorption, 92, 164, 191, 197, 199, 200 Thickness, 190, 199, 283 Types, interactions, 204 penetration, 251, 290 Tissue equalization, 510 Tomography, computerized, 464, 805 Transducers, 21 Transformers, electrical, 126, 134 step-down, 128, 136 step-up, 128, 134 Index Transformer law, 127 Transistor, 432 Transmutation, 66 Trauma, 295 casts and splints, 297 postmortem technique, 295 soft-tissue technique, 296 Tube current, 151 Tube, x-ray, 147 anode, 152 cathode, 149 components, 149 development of, 10 efficiency, 148 failure, 156 filaments, 149 focal spots, 149, 154 focusing cup, 149 glass envelope, 155 grid-controlled, 150 heat dispersion, 26, 152, 156 housing, cooling chart, 157 life, 158 rating charts, 156 space charge, 147 warm-up, 158 window, 156 x-ray production, 147 Tube-tabletop distance, adjustments for angles, 368 U Ultrasound, 87 Ultraviolet, 85 Umbra, 226, 353 Underexposure, 242 Units conversions, 19, 35 derived, 18 fundamental, 17 radiation, 715 systems, 19 Unmodified scatter, 188 Unsharp mask filtering, 512 Unsharpness, 227, see also penumbra and sharpness formula, 229 focal spot, 327 geometric, 225, 227, 380 measuring, 227 motion, 226, 371 OID, 352 SID, 336 SOD/OID ratio, 228, 355 V Variable kilovoltage technique, 390, 392 Variables, radiographic, 182 affecting: distortion, 379 exposure, 378 magnification, 379 noise, 378 sharpness, 378 subject contrast, 378 Veiling glare, fluoroscopy, 683 Viewing angle dependence, LCD, 627, 633, 666 Vignetting, fluoroscopy, 683 Virtual grid software, 308, 588 Visible light, see Light, visible Visibility factors, image, 211, 213 Volt, 118 Voltage, see Kilovoltage Voxel, 464 attenuation coefficient, 464 W Wave function, 95, 516 Waves, 73 Amplitude, 74 Compressional, 73 Cycle, 75 Electromagnetic, 78, 80 Electromagnetic formula, 78 Formula, 76 Frequency, 75 Longitudinal, 73 Plank formula, 79 Pulses, 75 Transverse, 73 Wave forms, electrical, 121, 251 Wavelength, 75 Electromagnetic energy, 79 Weight, 53 Weighting factors, radiation, 720 Windowing, 468, 505, 553 intensity transformations, 505 terminology, 553 Window level, 468, 554 Window width, 469, 554 Work stations, 470, 627, 639 X X-rays, 867 868 Radiography in the Digital Age absorption, 92 attenuation, 92, 464 bremsstrahlung, 164, 173 characteristic, 167, 189 characteristics of, 91, 93, 707 discovery, energy, see also kilovoltage and filtration generation, see production below history, interactions, see Interactions production, 147, 163, 173 transmission, 92 wavelength, 78, 79 vs visible light, 91 X-ray beam, 97, 181 corpuscular model, 97 energy, average, 249 peak, 80, 249 heterogeneity, 164 nomenclature, 182 quality and quantity, 139, 171 spectrum, 44, 166, 167, 170, 267 factors, 170 filtration, 172 generators/machine phase, 174, 267 kVp, 172 mAs, 171 target material, 170 X-ray machine circuits, 133 generators, 138 X-ray tube, 147, see Tube, x-ray Z Z number, atomic, 57 Zero, absolute, 27 ... of the decimal point would indicate hundreds, or groupings of 1 02 But, in the binary system, a “1” positioned in the third place to the left would indicate fours, or groupings of 22 Table 28 -3... number?” If the value there is one, there is a in the number Move to the left one place and ask if there are any 2 s in the number In this case, the value there is one, indicating a “yes” to the question... = 20 = 1’s 10’s 2nd place = 21 = 2 s 3rd place = 22 = 4’s 4th place = 23 = 8’s = 24 = 16’s Value = 10,000’s 5th place Value 446 Radiography in the Digital Age binary number system, the