Special Imaging Systems Unit VI Special Imaging Systems

Chapter 40 Fluoroscopy

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

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

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

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

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

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

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

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

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

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

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.

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

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.

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

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

Fluoroscopic X-Ray Tubes mA range: 0.5 – 5.0 mA 15” minimum SOD in fixed fluoroscopic equipment Foot switch Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

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.

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

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

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.

Input Screen and Photocathode 0.1 – 0.2 mm layer of sodium activated CsI 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.

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

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

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

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

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

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

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

Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. Minification Gain Minification gain = Input screen diameter2 output screen diamter2 Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. Patient Protection Typical exposure rates Cinefluorography 7.2 R/min Cassettes 30 mR/exposure 105 mm film 10 mR/exposure Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Protection of Radiographer and Radiologist Lead apron 0.25 mm Pb/eq Highest energy scatter 90o angle to the incident beam Same level as radiographer /radiologist’s gonads Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

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.

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