Chapter 8:Fluoroscopic Imaging Systems

1 IAEAI nternational Atomic Energy AgencySlide set of 95 slides based on the Chapter authored by A. Kyle Jonesof the IAEA publication (ISBN 978-92-0-131010-1):Diagnostic Radiology Physics: A Handbook for Teachers and StudentsObjective:To familiarize the student with the principles of the construction and operation of fluoroscopic Imaging systemsChapter 8:Fluoroscopic Imaging SystemsSlide set prepared by Maherfollowing initial work byS. EdyveanIAEACHAPTER 8 TABLE OF Fluoroscopic Imaging Performance & Equipment Adjunct Imaging Application-Specific Auxiliary Dosimetric Considerations in FluoroscopyBibliographyDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, Fluoroscopic Fluoroscopic Imaging Exposure Control (AEC) Imaging Performance & Equipment Adjunct Imaging Acquisition Subtraction Angiography (DSA) Chapter 8 TABLE OF CONTENTSD iagnostic Radiology Physics.

2 A Handbook for Teachers and Students Chapter 8, Application-Specific Remote Fluoroscopy Vascular & Interventional Mobile Auxiliary Spot Film Operating Recursive Dosimetric Considerations in Skin Dose Safety Considerations for Patient Safety Considerations for Operator ProtectionBibliographyCHAPTER 8 TABLE OF CONTENTSD iagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, INTRODUCTION Fluoroscopic Imaging : real-time radiographic imagingPlain Radiography: good SNR, poor Temporal ResolutionFluoroscopy: poor SNR, good Temporal ResolutionDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, FLUOROSCOPIC EQUIPMENTC omponents: High Voltage Generator X-Ray Tube (XRT) X-Ray Image Intensifier (XRII) Video CameraDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, FLUOROSCOPIC The Fluoroscopic Imaging ChainXRII converts:low intensity X-ray photon fluencetohigh fluence of Visible PhotonsDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, 7 IAEAI nput phosphor converts: X-Rays to LightMost commonly used phosphor .

3 CsI(Tl) crystals grown in a dense needle-like structure - prevents lateral light spreadTop portion of a ~750 micron thick film of CsI(Tl) demonstrating well separated columnar FLUOROSCOPIC The Fluoroscopic Imaging ChainDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, 8 IAEAP hotocathode converts: Light to ElectronsLight photons strike a very thin bi- or multi-alkali photocathodeElectrons: Releasedthrough photoelectric effect Repulsedfrom photocathode Acceleratedtowards anode by 25-30 FLUOROSCOPIC The Fluoroscopic Imaging ChainDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, 9 IAEAO utput phosphor converts: Electrons to LightElectron beam focused by electrodes onto a thin powder ZnCdS:Ag (P20)Incident Air Kerma Rate (IAKR): 15-40 Gy/min40 cm FOV FLUOROSCOPIC The Fluoroscopic Imaging ChainDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, 10 IAEAI ntensification -two mechanisms.

4 Electronic (orFlux)Gain - KE gained by electrons from acceleration (~50 typically) MinificationGain- reduction of large X-ray image at Input phosphor ( 40 cm) to a smaller diameter Output phosphor ( cm)402 256 Brightness Gain = (Electronic Gain).(Minification Gain)ranges from 2,500-7,000in FLUOROSCOPIC The Fluoroscopic Imaging ChainDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, 11 IAEAC onversion Factor: also used to express gaindefinition:Ratio of Luminanceat the output phosphor to the Incident X-ray Air Kerma Rateat the input phosphortypically 9-27 FLUOROSCOPIC The Fluoroscopic Imaging ChainDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, 12 IAEAO ptical System couples XRII to video cameraincludes.

5 Collimating Lensto shape the divergent light from the Output phosphor Apertureto limit the amount of light reaching the video camera Lensto focus the image onto the video FLUOROSCOPIC The Fluoroscopic Imaging ChainDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, 13 IAEAV ideo Camera captures the XRII output image, andconverts it to an analogue electrical signal that conforms to a recognized video format ( NTSC/PAL/SECAM)Older Video Cameras - Photoconductive target scanned by electron beamModern Video Cameras- Charge-Coupled Device (CCD) FLUOROSCOPIC The Fluoroscopic Imaging ChainDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, 14 IAEAP hotoconductive Video CamerasTARGET MATERIALCAMERA known as Vidicons FLUOROSCOPIC The Fluoroscopic Imaging ChainDiagnostic Radiology Physics.

6 A Handbook for Teachers and Students Chapter 8, 15 IAEAP hotoconductive Video CamerasResistivityof the photoconductive target changes based on the amount of light striking itCreating a Latent Imageof the XRII output phosphorAs the Electron Beamis scanned rapidly across the target, its intensity is modulated by this latent imageThe resulting small current is integratedacross a large resistance and converted to a voltage that is FLUOROSCOPIC The Fluoroscopic Imaging ChainDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, 16 IAEAP hotoconductive Video CamerasLAG Describes the Speedof response of the video camera to a changing signal High lag can result in blurred images of moving objects, but noise will be reduced through Temporal IntegrationSIGNAL-TO-NOISE RATIO (SNR)

7 Cameras with low SNR contribute to increased noise levels in fluoroscopic images - temporal integration can reduce this Maximum SNR is achieved when a video camera is operated near its maximum signal level - important that Apertureset accordinglyFundamental characteristics FLUOROSCOPIC The Fluoroscopic Imaging ChainDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, 17 IAEAA nalogue video waveform can be displayed directlyon a video monitorWaveform can also be digitized using an ADCI mportant ADC characteristics include: Bit Depth Sampling RateDigital images stored in a Video BufferPhotoconductive Video FLUOROSCOPIC The Fluoroscopic Imaging ChainDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, 18 IAEACCD Video CamerasA Solid -State Devicecomposed of many discretephotoconducting cellsLight from the Output phosphor is converted to electrons in an Amorphous Siliconphotoconducting layerThe electrons are stored in Potential Wellscreated by applying a voltage between rows and columns of FLUOROSCOPIC The Fluoroscopic Imaging ChainDiagnostic Radiology Physics.

8 A Handbook for Teachers and Students Chapter 8, 19 IAEACCD Video CamerasStored charge that has accumulated during an exposure is read out using parallel and serial Shift Registersthat move charge from column to column and row to row in a Bucket-Brigade fashionThis creates an analog signal that is amplifiedand output as a video signal or digitized FLUOROSCOPIC The Fluoroscopic Imaging ChainDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, 20 IAEACCD vs Vidicon Absence of Lag Wider Dynamic Range Reduce or eliminate Blooming, at the expense of Fill Factor and FLUOROSCOPIC The Fluoroscopic Imaging ChainDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, 21 IAEAFlat Panel Image ReceptorsReplacingXRIIs in modern systemsAdvantagesinclude.

9 Larger Size Less bulky Profile Absence of Image Distortions, and a Higher QDEat moderate to high IAKRFlat panels broaden applications to include Rotational Angiographyand Cone-Beam FLUOROSCOPIC The Fluoroscopic Imaging ChainDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, 22 IAEAFlat Panel Image ReceptorsTypical IAKR for fluoroscopic Imaging with a full-FOV flat-panel receptor (30 cm x 40 cm) range from 27-50 FLUOROSCOPIC The Fluoroscopic Imaging ChainSuffer from Additivenoise sources and therefore perform poorly compared to XRIIs at low IAKR Diagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, 23 IAEAV ideo Image DisplayImages must be converted from digital to analog form for image display on a viewing monitorEarly television standards determined at least 525video scan lines of the image were necessary to adequately display moving imagesBandwidth restrictions required scanning two frames or Video Fields, each containing one half (262 1 2) of the scan lines, in an Interlacedfashion to eliminate flickernote: NTSC FLUOROSCOPIC The Fluoroscopic Imaging ChainDiagnostic Radiology Physics.

10 A Handbook for Teachers and Students Chapter 8, 24 IAEAV ideo Image DisplayInterlacedscanning provides a refresh rate of 60 Hz while only requiring the bandwidth of 30 HzProgressivescanning videonote: NTSC FLUOROSCOPIC The Fluoroscopic Imaging ChainDiagnostic Radiology Physics: a Handbook for Teachers and Students Chapter 8, 25 IAEAV ideo Image ResolutionSpatial resolution limited in the Verticaldirection by the number of effective lines used to make the imageThe effective number of lines is the number of scan lines in the image multiplied by the Kell FactorThe Kell factor is an empirically determined factor that describes Verticalimage degra