Copyright 2006 by Thomson Delmar Learning ALL RIGHTS

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Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Unit VI Special Imaging Systems Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS

Unit VI Special Imaging Systems Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Chapter 40 Fluoroscopy Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Chapter 40 Fluoroscopy Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Objectives • Differentiate fluoroscopic examinations from static diagnostic radiographic examinations • Describe a typical

Objectives • Differentiate fluoroscopic examinations from static diagnostic radiographic examinations • Describe a typical basic fluoroscopic image chain • Explain difference between fluoroscopic operation and a diagnostic x-ray tube Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 4

Objectives • Describe advantages of image intensified fluoroscopy over conventional screen fluoroscopy Copyright ©

Objectives • Describe advantages of image intensified fluoroscopy over conventional screen fluoroscopy Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 5

Objectives • Explain function and operation of: – Image intensification tube input screen –

Objectives • Explain function and operation of: – Image intensification tube input screen – Photocathode – Electrostatic focusing lenses – Anode and output screen Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 6

Objectives • Explain operation of a multifield magnification image intensification tube • Discuss effects

Objectives • Explain operation of a multifield magnification image intensification tube • Discuss effects of minification and flux gain on total brightness gain • Explain basic function of a fluoroscopic automatic brightness control Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 7

Objectives • Discuss factors affecting: – Fluoroscopic image contrast – Resolution – Distortion –

Objectives • Discuss factors affecting: – Fluoroscopic image contrast – Resolution – Distortion – Quantum mottle Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 8

Objectives • Explain operation of: – Optical mirror viewer system – Video camera CCD

Objectives • Explain operation of: – Optical mirror viewer system – Video camera CCD – Video camera tube – Video monitor Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 9

Objectives • Evaluate three basic types of fluoroscopic viewing systems • Explain uses of

Objectives • Evaluate three basic types of fluoroscopic viewing systems • Explain uses of dynamic and static fluoroscopic recording systems • Evaluate fluoroscopic recording systems for clinical situations Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 10

Objectives • Explain digital fluoroscopic image acquisition • Relate problems with mobile radiographic equipment

Objectives • Explain digital fluoroscopic image acquisition • Relate problems with mobile radiographic equipment to mobile fluoroscopic equipment Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 11

Objectives • Discuss various methods of reducing dose to patient, radiographer, and radiologist during

Objectives • Discuss various methods of reducing dose to patient, radiographer, and radiologist during a fluoroscopic examination Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 12

Historical Development • Dynamic examination • Active diagnosis – Domain of radiologist • Fluoroscope

Historical Development • Dynamic examination • Active diagnosis – Domain of radiologist • Fluoroscope – Invented by Edison in 1896 Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 13

Fluoroscopic Imaging Chain • Specialized x-ray tube • Image receptor – Fluoroscopic screen –

Fluoroscopic Imaging Chain • Specialized x-ray tube • Image receptor – Fluoroscopic screen – Mirrors – Image intensification • Video camera and monitor Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 14

Fluoroscopic Uses • Functional studies – GI tract studies – Angiograms Copyright © 2006

Fluoroscopic Uses • Functional studies – GI tract studies – Angiograms Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 15

Fluoroscopic Positioning Previewing • Radiographers are trained in positioning • Unnecessary radiation exposure to

Fluoroscopic Positioning Previewing • Radiographers are trained in positioning • Unnecessary radiation exposure to patient is unethical • Fluoroscopic equipment should not be used to preview patient’s position Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 16

Types of Equipment • C-arm • Under table/over table units Copyright © 2006 by

Types of Equipment • C-arm • Under table/over table units Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 17

Types of Equipment • Raise and lower image receptor for accuracy – Can vary

Types of Equipment • Raise and lower image receptor for accuracy – Can vary beam geometry and image resolution • Full beam intercept Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 18

Fluoroscopic X-Ray Tubes • m. A range: 0. 5 – 5. 0 m. A

Fluoroscopic X-Ray Tubes • m. A range: 0. 5 – 5. 0 m. A • 15” minimum SOD in fixed fluoroscopic equipment • Foot switch Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 19

Early Fluoroscopic Screens • Very dim • Required dark adapted viewing • Low visual

Early Fluoroscopic Screens • Very dim • Required dark adapted viewing • Low visual acuity – Uses scotopic vision (rods) Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 20

Image Intensification • Introduced in 1948 • Higher visual acuity – Uses photopic vision

Image Intensification • Introduced in 1948 • Higher visual acuity – Uses photopic vision (cones) Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 21

Image Intensification Tube Components • Input screen and photocathode • Electrostatic lenses • Magnification

Image Intensification Tube Components • Input screen and photocathode • Electrostatic lenses • Magnification tubes Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 22

Image Intensification Tube Components • Anode and output screen • Total brightness gain –

Image Intensification Tube Components • Anode and output screen • Total brightness gain – Minification gain x flux gain Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 23

Input Screen and Photocathode • Input screen – 0. 1 – 0. 2 mm

Input Screen and Photocathode • Input screen – 0. 1 – 0. 2 mm layer of sodium activated Cs. I – Converts intercepted x-ray beam to light • Photocathode – Emits electrons when struck by light emitted by input screen Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 24

Electrostatic Lenses • Accelerate and focus electron pattern across tube to anode • Primary

Electrostatic Lenses • Accelerate and focus electron pattern across tube to anode • Primary source of brightness gain Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 25

Magnification Tubes • Greater voltage to electrostatic lenses – Increases acceleration of electrons –

Magnification Tubes • Greater voltage to electrostatic lenses – Increases acceleration of electrons – Shifts focal point away from anode • Dual focus – 23/15 Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 26

Magnification Tubes Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 27

Magnification Tubes Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 27

Magnification • Input screen diameter • Diameter used during exam Copyright © 2006 by

Magnification • Input screen diameter • Diameter used during exam Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 28

Anode and Output Screen • Anode – Positively charged – 25 k. Vp –

Anode and Output Screen • Anode – Positively charged – 25 k. Vp – Hole in center allows electrons to pass through to output screen Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 29

Anode and Output Screen • Output screen – Glass fluorescent screen – Zinc-cadmium sulfide

Anode and Output Screen • Output screen – Glass fluorescent screen – Zinc-cadmium sulfide – Emits light when struck by electrons Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 30

Total Brightness Gain • Minification gain x flux gain Copyright © 2006 by Thomson

Total Brightness Gain • Minification gain x flux gain Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 31

Minification Gain Minification gain = Input screen diameter 2 output screen diamter 2 Copyright

Minification Gain Minification gain = Input screen diameter 2 output screen diamter 2 Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 32

Flux Gain • Measurement of conversion efficiency of output screen – 1 electron strikes

Flux Gain • Measurement of conversion efficiency of output screen – 1 electron strikes output screen – 50 light photons are emitted – Flux gain = 50 Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 33

Fluoroscopic Generators • Same as those used for static radiography Copyright © 2006 by

Fluoroscopic Generators • Same as those used for static radiography Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 34

Brightness Control • Automatic brightness control • Automatic dose control Copyright © 2006 by

Brightness Control • Automatic brightness control • Automatic dose control Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 35

Brightness Control • Automatic brightness stabilization – Automatic adjustments made to exposure factors by

Brightness Control • Automatic brightness stabilization – Automatic adjustments made to exposure factors by equipment • Automatic gain control – Amplifies video signal rather than adjusting exposure factors Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 36

Image Quality • • Contrast Resolution Distortion Quantum mottle Copyright © 2006 by Thomson

Image Quality • • Contrast Resolution Distortion Quantum mottle Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 37

Contrast • Controlled by amplitude of video signal • Affected by: – Scattered ionizing

Contrast • Controlled by amplitude of video signal • Affected by: – Scattered ionizing radiation – Penumbral light scatter Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 38

Resolution • Video viewing – Limited by 525 line raster pattern of monitor Copyright

Resolution • Video viewing – Limited by 525 line raster pattern of monitor Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 39

Size Distortion • Affected by same parameters as static radiography – Primarily OID –

Size Distortion • Affected by same parameters as static radiography – Primarily OID – Can be combated by bringing image intensifier as close to patient as possible Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 40

Shape Distortion • Geometric problems in shape of input screen – Concave shape helps

Shape Distortion • Geometric problems in shape of input screen – Concave shape helps reduce shape distortion, but does not remove it all – Vignetting or pin cushion effect Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 41

Quantum Mottle • Blotchy, grainy appearance – Caused by too little exposure – Most

Quantum Mottle • Blotchy, grainy appearance – Caused by too little exposure – Most commonly remedied by increasing m. A Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 42

Viewing Systems • Video viewing system • Video camera tubes – Cathode – Anode

Viewing Systems • Video viewing system • Video camera tubes – Cathode – Anode Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 43

Viewing Systems • Video camera charge-coupled device (CCD) • Video monitor • Digital Copyright

Viewing Systems • Video camera charge-coupled device (CCD) • Video monitor • Digital Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 44

Video Viewing System • Closed circuit television – Video camera coupled to output screen

Video Viewing System • Closed circuit television – Video camera coupled to output screen and monitor • Video cameras – Vidicon or Plumbicon tube – CCD Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 45

Video Camera Tubes • Plumbicon and vidicon tubes similar – Different target materials –

Video Camera Tubes • Plumbicon and vidicon tubes similar – Different target materials – Plumbicon has faster response time than vidicon Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 46

Video Camera Tube Components • Cathode – Control grid • Electromagnetic focusing coils •

Video Camera Tube Components • Cathode – Control grid • Electromagnetic focusing coils • Electrostatic deflecting coils Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 47

Video Camera Tube Components • Anode – Face plate – Signal plate – Target

Video Camera Tube Components • Anode – Face plate – Signal plate – Target Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 48

Cathode • Heating assembly – Electron gun – thermionic emission • Control grid –

Cathode • Heating assembly – Electron gun – thermionic emission • Control grid – Shapes electron beam Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 49

Raster Pattern • Electron beam is accelerated across TV camera tube to anode •

Raster Pattern • Electron beam is accelerated across TV camera tube to anode • Slowed at anode by wire mesh in front of target Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 50

Raster Pattern • Electromagnetic focusing coils – Shape electron beam into single point •

Raster Pattern • Electromagnetic focusing coils – Shape electron beam into single point • Deflecting coils – Cause electron stream to scan target in raster pattern Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 51

Anode • Face plate • Signal plate – Positively charged thin film of graphite

Anode • Face plate • Signal plate – Positively charged thin film of graphite • Target – Changes light pattern to electronic signal sent to video system Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 52

Target • Thin insulating mica • Matrix of globules of photoconductive material – Vidicon

Target • Thin insulating mica • Matrix of globules of photoconductive material – Vidicon • Antimony trisulfide – Plumbicon • Lead oxide Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 53

Video Camera Charged Coupled Devices (CCD) • Semiconducting device • Emits electrons in proportion

Video Camera Charged Coupled Devices (CCD) • Semiconducting device • Emits electrons in proportion to amount of light striking photoelectric cathode • Fast discharge eliminates lag Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 54

Video Camera Charged Coupled Devices (CCD) • Operate at lower voltages than video tubes

Video Camera Charged Coupled Devices (CCD) • Operate at lower voltages than video tubes • More durable than video tubes Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 55

Video Monitor Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 56

Video Monitor Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 56

Digital Fluoroscopy • Image intensifier output screen coupled to TFTs • TFT photodiodes are

Digital Fluoroscopy • Image intensifier output screen coupled to TFTs • TFT photodiodes are connected to each pixel element • Resolution limited in favor of radiation exposure concerns Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 57

Recording the Fluoroscopic Image • • Dynamic systems Cine film systems Videotape recording Static

Recording the Fluoroscopic Image • • Dynamic systems Cine film systems Videotape recording Static spot filming systems Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 58

Recording the Fluoroscopic Image • Cassettes • 105 mm chip film • Digital fluoroscopy

Recording the Fluoroscopic Image • Cassettes • 105 mm chip film • Digital fluoroscopy Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 59

Dynamic Systems • Cine film • Videotape Copyright © 2006 by Thomson Delmar Learning.

Dynamic Systems • Cine film • Videotape Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 60

Cine Film Systems • Movie camera intercepts image – 16 mm and 35 mm

Cine Film Systems • Movie camera intercepts image – 16 mm and 35 mm formats – Record series of static exposures at high speed – 30 – 60 frames per second Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 61

Cine Film Systems • Offer increased resolution – At the cost of increased patient

Cine Film Systems • Offer increased resolution – At the cost of increased patient dose Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 62

Videotape Recording • VHS-S Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Videotape Recording • VHS-S Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 63

Static Spot Filming Systems • Cassettes • 105 mm chip film Copyright © 2006

Static Spot Filming Systems • Cassettes • 105 mm chip film Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 64

Cassettes • Standard size - 9” x 9” • Stored in lead-lined compartment until

Cassettes • Standard size - 9” x 9” • Stored in lead-lined compartment until ready for exposure • When exposure is made, m. A is raised to radiographic level • Multiple image formats Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 65

105 mm Chip Film • 12 frames per second • Beam splitting mirror Copyright

105 mm Chip Film • 12 frames per second • Beam splitting mirror Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 66

Digital Fluoroscopy • Use CCD to generate electronic signal • Signal is sent to

Digital Fluoroscopy • Use CCD to generate electronic signal • Signal is sent to ADC • Allows for post processing and electronic storage and distribution Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 67

Radiation Protection During Fluoroscopy • The patient • The radiographer and radiologist • Others

Radiation Protection During Fluoroscopy • The patient • The radiographer and radiologist • Others Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 68

Patient Protection • Tabletop exposure rate – Maximum 10 R/min – Typically 1 –

Patient Protection • Tabletop exposure rate – Maximum 10 R/min – Typically 1 – 3 R/min Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 69

Patient Protection • Minimum source-to-skin distance – 12” for mobile equipment – 15” for

Patient Protection • Minimum source-to-skin distance – 12” for mobile equipment – 15” for stationary systems • Audible alarm at 5 mins. • Same rules for collimation Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 70

Patient Protection • Typical exposure rates – Cinefluorography • 7. 2 R/min – Cassettes

Patient Protection • Typical exposure rates – Cinefluorography • 7. 2 R/min – Cassettes • 30 m. R/exposure – 105 mm film • 10 m. R/exposure Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 71

Protection of Radiographer and Radiologist • Lead apron – 0. 25 mm Pb/eq •

Protection of Radiographer and Radiologist • Lead apron – 0. 25 mm Pb/eq • Highest energy scatter – 90 o angle to the incident beam – Same level as radiographer /radiologist’s gonads Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 72

Protection of Radiographer and Radiologist • Single step away from the table decreases exposure

Protection of Radiographer and Radiologist • Single step away from the table decreases exposure exponentially • Bucky slot cover • Lead rubber drape • Radiologist as shielding Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 73

Protection of Others • Radiographer’s responsibility to inform others in the room to wear

Protection of Others • Radiographer’s responsibility to inform others in the room to wear lead apron • Do not initiate fluoroscopy until all persons have complied Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 74