Introduction to Medical Imaging-new gives a basic knowledge

Brainstorming!

1. BY Dr Nebyu Samuel Radiologist Introduction to Medical Imaging

2. Radiology • Diagnostic Imaging • Interventional Radiology

3. List of diagnostic imaging studies Plain x-rays Mammography Angiography Fluoroscopy CT scan Nuclear imaging/PET MRI Ultrasound Which of these modalities use ionizing radiation?

4. Electromagnetic Spectrum(Radiation)

5. Diagnostic Imaging • Electromagnetic Radiation – Radiography & Computed Tomography (CT) – Magnetic Resonance Imaging (MRI) – Nuclear Scintigraphy (Nuclear Medicine) • Sound Waves (exception) – Ultrasound

6. Types of Radiation Electromagnetic Radiation (photons) Radio frequency – from coils used in MRI X-Rays - from xray tube Gamma rays - from nuclear decay

7. Xray • Plain Radiography – X RAY PRODUCTION – inherent contrast – film – digital • Contrast Radiography – barium – iodine • Fluoroscopy • CT (Computed Tomography)

8. X-rays pass through patient to a receptor (film , digital, fluorescent screen, etc) ELECTRONS XRAYS

9. January 1896 - First x-ray made in public Routine x-ray current technology Wilhelm Conrad Roentgen 1845-1923

10. A diagnostic image is composed of differences in contrast between tissues!

11. INHERENT CONTRAST • Tissue Thickness & Tissue Type

12. Tissue thickness affects x-rays attenuation. WHITE GRAY BLACK Tissue Thickness LESS GET THROUGH>>MORE GET THROUGH

13. The tissue type affects the attenuation of the x-rays BLACK GRAY WHITE Tissue type MORE GET THROUGH >> LESS GET THROUGH

14. Radiographs are summation of shadows created by differences in contrast between tissues. Tissue thickness and tissue composition affect the attenuation and therefore, the shade(s) of gray in the final shadow image.

15. Xray • Plain Radiography – X ray production – INHERENT CONTRAST – film – digital / PACS • Contrast Radiography – barium – iodine • Fluoroscopy • CT (Computed Tomography)

16. INHERENT CONTRAST 5 Basic Radiographic Densities • Tissue – – – – – Air Fat Soft Tissues Bone, Calcium Metal • Appearance on XRAY – – – – – Black Dark Gray Gray White Really White

17. 5 Basic Radiographic Densities Air Fat Soft tissue/fluid Mineral Metal 1 . 2. 3. 4. 5. Name these radiographic densities.

18. TISSUE BONE SOFT FAT AIR

19. METAL

20. Xray • Plain Radiography – X ray production – inherent contrast – FILM – digital / PACS • Contrast Radiography – barium – iodine • Fluoroscopy • CT (Computed Tomography)

21. Film Radiography FILM CASSETTE

22. Film Radiography PHOTONS PRODUCED BY XRAYS HITTING A SCREEN IN FRONT OF THE FILM INSIDE OF A CASSETTE

23. Xray • Plain Radiography – X ray production – inherent contrast – film Radiography – DIGITAL Radiography • Contrast Radiography – barium – iodine • Fluoroscopy • CT (Computed Tomography)

24. ‘Digital’ Radiography • Two types – Computed radiography, called CR • Film cassette is replaced with a charged metal plate • After exposure , plate is ‘read’ in a special device – Digital radiography, called DR • Film cassette is replaced by a charged sensor (like in a digital camera or video camera)

25. Computed Radiography (CR) HERE ARE THE PLATES

26. Film --> Computer Viewing 20 TH CENTURY 21 ST CENTURY

27. Contrast Agent • Anything that enhances the differences between tissues of similar densities • For XRAY contrast agents : – Barium – Iodine • Various ways they are introduced – – – – Swallowed: barium swallow, upper GI Per rectum: barium enema In vein: Intravenous urogram In artery: Arteriogram

28. PLAIN RADIOGRAPH OF THE CHEST BARIUM SWALLOW

29. PLAIN RADIOGRAPH OF THE ABDOMEN BARIUM ENEMA

30. Barium: upper GI STOMACH

31. Iodine: Intravenous urogram Intravenous pyelogram (IVU or IVP) KIDNEYS URETERS BLADDER

32. Iodine: Arteriogram through a catheter (tube) in the leg RENAL ARTERY AORTA ILIAC ARTERY

33. Xray • Plain Radiography – X ray production – inherent contrast – film – digital / PACS • Contrast Radiography – barium – iodine • FLUOROSCOPY • CT (Computed Tomography)

34. Fluoroscopy relies on image intensifiers to make moving (real time) X-ray pictures XRAYS IN LIGHT OUT

35. Diagram of fluoroscopic unit Photograph of a fluoroscopic unit

36. Xray • Plain Radiography – X ray production – inherent contrast – film – digital / PACS • Contrast Radiography – barium – iodine • Fluoroscopy • CT (COMPUTED TOMOGRAPHY)

37. Computed Tomography (CT)

38. U ses X-RAYS Tube & Detector spins together around the patient Computer performs calculations to estimate density of tissues in each square of a ‘slice’ Computed Tomography (CT) Brain Image 1974, Matrix 80 x 80

39. Computed Tomography (CT)

40. What is displayed in CT images? CT value; in honor of inventor of CT ( Hounsfeild unit )(HU ) - CT numbers. Each pixel has a number representing the x -ray attenuation in the corresponding voxel

41. Cont… Water and water equivalent tissue (0HU) Air corresponds (-1000HU). Tissues denser than water are given positive CT numbers. The Hounsfield scale has no upper limit.but; for medical application (-1024HU to +3071HU)

42. Hounsfield Scale

43. Windowing 4096 gray levels cannot be differentiated in single view. Human eye can only distinguish max. of 60-80 gray levels. CT value of interest - window ! Values above the chosen window - white V alues below the window - black

44. Cont…

45. Cont… For display of very small attenuation differences as given in; e.g. Brain - Narrow Window is chosen. For large differences as presented by the lung or skeleton - Wide Window.

46. Windowing cont…

47. Windowing cont…

48. Contrast for CT • Iodine injected into an arm vein • Iodine or Barium diluted in water given orally for abdomen scans • There are some risks – Allergic reaction – Kidney damage • Enhances the blood vessels and organs

49. CONTRAST IODINE

50. Contrast agents

51. The three orthogonal views In principle slice image can be generated in arbitrary orientation. However; for CT mostly a transverse (x/y plane) is scanned directly Z-axis - perpendicular scan plane Sagittal body sections (left / right) & coronal sections (ant /post).

52. Things we can do with CT image processing • CT Angiography Scan rapidly during Iodine injection in vein • Colonography Scan colon after filling with air • Bronchoscopy Scan chest air is already in bronchi • 3D Images Computer reconstruction

53. CT Angiograms

54. CT Colonography

55. CT Bronchoscopy

56. Human Responses to Ionizing Radiation

57. Human Radiation Response effect of x-rays is the result of interactions at the atomic level atomic interactions take the form of ionization or excitation of orbital electrons and result in the deposition of energy in tissue

58. Cont…

59. Cont… The abnormal molecule in time - function improperly - cease to function or death of cell At each stage in the sequence, it is possible to repair radiation damage and recover.

60. Cont… radiation response occurs within minutes or days after exposure, it is classified as an early effect of radiation. On the other hand, if the human injury is not observed for months or years, it is called a late effect of radiation.

61. Cont… Most human responses have been observed to occur after exposure to rather large radiation doses. However , we are cautious and assume that even small doses are harmful.

62. Radio-sensitivity varies with age. Experiments with animals have shown that the very young and the very old are more sensitive to radiation.

63. EARLY EFFECTS OF RADIATION ON HUMANS 1. Acute radiation syndrome Hematologic syndrome Gastrointestinal syndrome Central nervous system syndrome 2. Local tissue damage Skin Gonads 3. Hematologic depression

64. LATE EFFECTS OF RADIATION ON HUMANS 1. Leukemia 2. Other malignant disease Bone cancer Lung cancer Thyroid cancer Breast cancer 3. Local tissue damage Skin Gonads Eyes 4. Shortening of life span 5. Genetic mutation

65. Effects of Fetal Irradiation Prenatal death Neonatal death Congenital malformation Childhood malignancy Diminished growth and development

66. The Commandments of Radiation Protection Understand and apply the cardinal principles of radiation control: time, distance, and shielding . Do not allow familiarity to result in false security. Never stand in the primary beam. Always wear protective apparel when not behind a protective barrier. Always wear an occupational radiation monitor and position it outside the protective apron at the collar. Never hold a patient during radiographic examination. Use mechanical restraining devices when possible. Otherwise, have parents or friends hold the patient.

67. Cont… The person who is holding the patient must always wear a protective apron and, if possible, protective gloves. Use gonadal shields on all people of childbearing age when such use will not interfere with the examination. Examination of the pelvis and lower abdomen of a pregnant patient should be avoided whenever possible especially during the first trimester. Always collimate to the smallest field size appropriate for the examination

68. Comparisons of Effective Dose

69. Magnetic Resonance Imaging (MRI)

70. Magnetic Resonance Imaging • Starts with a really strong magnet – Supercooled with Liquid Helium / Nitrogen • Transmit radio wave pulses into patient • Listen for return radio waves caused by interaction with protons (water) in the patient’s body • Process the frequency and phase of the returned signals by computer

71. Magnetic Resonance Imaging Starts with a really strong magnet – Supercooled with Liquid Helium / Nitrogen Transmit radio wave pulses into patient Listen for return radio waves caused by interaction with protons (water) in the patient’s body Process the frequency and phase of the returned signals

72. Coils

73. Sagital C-spine MRI

74. Brain MRI

75. MRI Contrast Gadolinium solution injected into vein Gadolinium alters the interaction of radio waves with the protons in water so that it gives MORE signal Shows up as white on images

76. Magnetic Resonance Angiography May be done after injecting contrast (Gadolinium) or without(TOF ) Flowing blood changes the way that radio waves interact with the water in blood – May give more signal (IN TOF) – May give less signal (AS FLOW VOID)

77. TOF

78. Ultrasound

79. Ultrasound • Uses high frequency sound – 2-15 MHz typically used • The sound is produced and detected with the same device: TRANSDUCER • Transducer – Speaker: sound into patient – Microphone: sound coming back from patient Ultrasound uses sound waves . Audible 20Hz and 20 000Hz. I nfra sound < 20Hz Ultrasound > 20 000Hz

80. Cont… The frequency affects the image QUALITY The HIGHER the frequency, the BETTER the resolution The LOWER the frequency, the LESS the resolution but good penetration

81. Reflected Echo’s Strong Reflections = ‘ Echogenic’ - White (Diaphragm , tendons, bone)

82. Reflected Echo’s Weaker Reflections = Grey Most solid organs, thick fluid – ‘isoechoic ’ Homogeneous

83. Reflected Echo’s No Reflections = Black (Fluid within a cyst, urine, blood) ‘Anechoic ’ or echo-free

84. Color Flow Imaging The direction of blood flow is indicated by the display color Flow is from left to right on the image, I t is directed toward the transducer on the left-hand side of the image and away from the transducer on the right-hand side.

85. Angiography And Interventional Radiology

86. Interventional Radiology Needles for biopsy or fluid removal Catheters to make angiograms Catheters with balloons to open blood vessels Stents to hold blood vessels open Coils and material to block blood vessels Catheters to drain abscesses Tubes for feeding Etc …

87. Angiogram of normal kidney SPINE THIS IS THE CATHETER COMING UP FROM THE LEG ARTERY 11 TH RIB

88. Angiogram of renal Cancer THIS IS THE MALIGNANT MASS

89. THIS IS THE CANCER MASS Angiogram of artery to mass THIS IS THE CATHETER COMING UP FROM THE LEG ARTERY

90. Angiogram after embolization NO BLOOD FLOW TO THE MASS NOW IT CAN BE REMOVED WITHOUT EXCESSIVE BLEEDING

91. Non Surgical Biopsy

92. Draining Abscess

93. Angioplasty Balloon Vascular Stent

94. BEFORE Angioplasty & Stent AFTER

95. Thank you