1. Chapter 1: What Is Digital Imaging?

2. What is Digital Imaging? Digital Imaging is the transforming of energy: (from light photon, sonic, magnetic, x-ray, or gamma radiation sources) to electrical signals that are measured and assigned discrete binary values. Binary data is processed into image information which may be enhanced, printed, displayed on a monitor, and stored as a computer file.

3. Digital Modalitites Every imaging modality may be digital. Some are only digital. From an equipment standpoint, the major difference between the modalities is the type of energy used, how the energy is changed as is traverses the body, and how the remnant energy is measured as it leaves the body.

4. Computed Tomography (CT) X-radiation passes through, and is attenuated by the atomic composition of cells and tissues. Is only digital

5. Cardiovascular Interventional Technology (CVI) digital application started in the 1980s X-radiation passes through, and is attenuated by the atomic composition of cells and tissues.

6. Magnetic Resonance Imaging (MRI ) Is only digital Hydrogen atoms excited by radio frequencies (RF) create magnetic vectors that sweep an antenna.

7. Nuclear Medicine Technology An isotope is injected, ingested or inhaled. After being metabolized, concentrations of the isotope are collected by the nuclear medicine camera.

8. Diagnostic Medical Sonography and Vascular Technology Sound waves pass into, and are reflected off of interfaces of tissues and organs.

9. Digital Radiography (DR) X-radiation passes through, and is attenuated by the atomic composition of cells and tissues. Digital applications were available in the early 1980s, but the difficulties of displaying radiographic quality images (in terms of spatial resolution) made it unpopular. In the year 2000 it was beginning to be accepted.

10. Digital Mammography X-radiation passes through, and is attenuated by the atomic composition of cells and tissues. Like digital radiography, highly dependant on excellent spatial resolution.

11. Digital Fluoroscopy (DF)

12. R/F Digital C-Arm

13. Question: How is an analog radiographic image made? Begin with photons coming off the anode. Outline the process, step by step. Use the appropriate terminology. Incident, Attenuation, Remnant radiation, Latent, Manifest

14. Answer: How does a radiographic image get on a film? Incident beam leaves anode. Attenuation in body. Remnant radiation exits in pattern of anatomy. Photons interact with silver halide crystals. Latent image is formed. Manifest image on development.

15. Question: What does a graphic representation of density building on a film look like, and what is it called? D log E (or) H & D Curve (or) Hurter & Driffield Curve (or) Characteristic Curve (or) Sensitometric Curve

16. Producing a digital radiograph is the same as for analog film, up to the point of the photons interacting with the film. Digital imaging samples the remnant radiation with (some kind of) a detector, not film.

17. Analog : The continuous build up of density on a radiographic film is an analog process.

18. For Example:Analog Time The passage of time as recorded on a watch with a continuous- sweep secondhand is an example of an analog measurement of time.

19. Digital Time The passage of time as recorded on a digital clock, in discrete values, is an example of a digital process

20. Analog is continuous. Digital is discrete.

21. Computer circuitry is made up of a series of switches that store data in one of two elementary -discrete- states: on, or off. = 0 = 1 Open Closed

22. 0 and 1 are the only two numbers used in the binary (two numbers) numbering system 0 and 1 are binary digits or bits Digital computers store data as binary digits.

23. Pascal’s calculator - 1642 A series of gears, turned by hand, rotated a wheel with numbers that showed in a window. When the number in the ones column reached nine, it turned the wheel in the tens column to 1, and the ones column returned to zero. Pascal invented his device to relieve the fatigue of spirit associated with the work of doing arithmetic. A mechanical device, not programmable

24. Jacquard’s Loom - 1804 Instructions for weaving patterns into cloth were fed into Jacquard’s machine by this early version of punched cards that were made of wood. The red arrows show the cards entering and leaving the machine. A mechanical device, that was programmable

25. Babbage’s Difference Engine - 1822 A crank was turned to perform a mechanical progression of numbered gears in columns that, like Pascal’s calculator, represented increasing powers of ten.

26. Hollerith’s tabulator Like Pacal’s calculator, and Babbage’s difference engine numbers were carried over from one column to the next. The great advantage of this device was the use of electric motors to drive mechanical parts, and punched cards to input data. In 1880 it took 9 years to tally the results of the US census. Herman Hollerith built an electromechanical calculator that used punched cards to input data on the population (age, gender, numbers in family, etc), and reduced the time to do it in half, on a greater population, with a more detailed analysis.

27. George Boole 1815-1864

28. Mark I - 1944 The gears of its predecessors were replaced by mechanical switches. Electric motors, were used to drive the mechanics that opened and closed the switches, and punched cards were used to input data. An electromechanical device, that was programmable.

29. On + Off = Off Off + Off = Off On + On = On AND Gate

30. On + Off = On Off + Off = Off OR Gate On + On = On

31. On = Off Off = On NOT Gate

32. 0+00+0 0 0 Operation of a Half Adder = 0

33. 1+01+0 0 1 Operation of a Half Adder = 1

34. 0+10+1 0 1 Operation of a Half Adder = 1

35. 1+11+1 1 0 Operation of a Half Adder = 2

36. Three Things a Computer Does 1. Arithmetic functions 2. Comparison functions 3. Memory Accomplished with accuracy and speed

37. ENIAC - 1946 The first fully electronic calculator used 18,000 vacuum tubes that replaced the switches of Mark I. The input of data was accomplished by turning knobs, reconfiguring telephone patch cords, and punched cards.

38. UNIVAC I - 1951 The first commercial computer sold in the United States. UNIVAC was build by the inventors of ENIAC, J Presper Eckert, and John Machly. “Computers of the future may weigh no more than 1.5 tons.” Popular Science, 1949

39. Cathode Anode Grid Vacuum tube: When the grid is positively charged electrons are drawn from the cathode to the anode, creating a closed circuit (1). When the grid is negatively charged electrons are repelled, and circuit is open (0). Transistors: Similar in principle to the operation of a vacuum tube. The solid state semi-conducting material allowed this switching device to use less energy and produce less heat in a smaller component. Vacuum Tubes and Transistors

40. Vacuum tube, Transistor, and IC

41. Within an integrated circuit (IC) are millions, billions, or trillions of AND, OR, and NOT gates embedded in the layers of the miniaturized circuits of the semi-conductor material. Silicon wafers are manufactured in clean rooms to prevent the smallest contaminate from being introduced. Integrated Circuits

42. Generations of Electronic Computing 1st - 1951- 57 Vacuum tubes 2nd - 1958 - 63 Transistors 3rd - 1964 - 69 Integrated circuits 4th - 1970 - 90 Very large scale integration (VLSI) leading to the microprocessor (computer in single chip). 5th - 1999 - Age of connectivity

43. Binary numbering 1248163264128256512 2 0 2 1 2 2 2 3 2 4 = 140 0 0 0 0 0 0 1 1 1 0 = 421 0 1 0 1 0 1 1 1 1 1 1 1= 127

44. Binary numbering 1248163264128256512 84 1 128 010100

45. Binary numbering 1248163264128256512 400 1 512 100100 384 00

46. Picture Elements (PIXELS) An image displayed on a monitor is comprised of individual dots called pixels. One bit of computer memory (on or off) is all it takes to light up a pixel, or not. One Pixel

47. Picture Elements (PIXELS) The sum of the pixels in an image display forms a matrix

48. MRI: Mid-sagittal plane, brain scan. Scale of contrast 2 1 Only one bit of data is needed to control each pixel: on or off. 2 1 Scale of Contrast

49. Question: How can a simple on/off switch be used to store complex information that contains many shades of gray? Answer: Many switches are used in combination.

50. On/off switches are arranged in groups of eight in the computer’s circuitry CC Eight bits = one byte Consider the expanded gray scale of two switches in combination. (Chapter 2 has a complete explanation of the binary numbering system.) OFF ON OFF ON OFF ON BlackDark grayLight grayWhite In addition to turning the electron been on and off, a second switch stores values that control the quantity of electrons in the beam, creating a gray scale.

51. With enough bytes of memory, any number can be represented by combinations of binary digits offon 16 8 4 2 1 1 0 1 = 5 1 1 1 = 7

52. 250 The number 47 defines the shade of gray for the pixel in column 250, row 210. Printout of the data in the matrix of a CT image

53. Column 250 Row 210 Values of digits stored in bytes of computer memory directly correspond to the illumination of pixels. In this case, the pixel in column 250, row 210.

54. A representation of a CT section as image data, analogous to a paint-by-numbers drawing

55. Question: If one bit of data is enough to turn a pixel off or on, what can a byte of data do for a single pixel? Answer: A byte of image data stores values for 256 shades of gray. (Chapter 2 has a complete explanation of the binary numbering system.)

56. How many KB of computer memory is required for a monitor with a 512 x 512 matrix displaying a gray scale of 2? 512 x 512 = 262,144 bits 262,144 / 8 bits per byte = 32,768 bytes 32,768 bytes / 1024 bytes in a kilobyte = 32KB Answer = 32KB

57. How many bytes of computer memory is required for a for a monitor with a 512 x 512 matrix, displaying 256 shades of gray (2 )? 8 512 x 512 = 262,144 bits 262,144(8bits)/8 bits per bytes = 262,144 bytes 262,144 bytes/1024 bytes in a kilobyte =262KB Answer = 262KB Conclusion: Images are memory hogs.