FLUOROSCOPY EXAM CHEAT SHEET
OMAR CHOUDHRI
Fluoroscopy Exam Cheat Sheet
SI Units:
Absorbed Dose: Gray (Gy )& Rad; 1 Rad equals 100ergs per gram
1 Gray= 1joule/kg –Gy is SI unit
1 Gray= 100 Rads
Dose Equivalent: Absorbed Dose X Quality Factor
Rem; Sievert (Si) is the SI unit
1 Si= 1 joule/kg
1 Si=100 Rem
Electron Volt: Unit of Energy
Erg: another unit of energy 10-7 joules
Kerma: sum of kinetic energies of all charged items, unit is joule/kg or Gy.
Milliampere : mA , measure of X ray tube current, measure of quantity of X ray
Eponyms:
Stochastic Effect
Non Stochastic Effect
Photoelectric Effect
Compton Effect
Law of Bergonie & Tribondeau
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FLUOROSCOPY EXAM CHEAT SHEET
OMAR CHOUDHRI
Chapter 1
Input Phosphor traditionally Silver activated Cadmium sulphate
2nd gen CsI
Output Phosphor CsI
Photocathode is made of antimony and Cesium
Electrostatic focusing lens positively charged and invert image
Accelerating Anode has a potential of 25kV
Electrostatic focusing voltage directly proportional to magnification
Exposure directly increases proportionally with magnification to compensate for
decreased brightness = normal squared/mag mode squared
The mA is automatically increased when unit used in 6 inch magnified mode so
patient dose exposure increased (9/6 gen 2.2)
Brightness Gain = Intensifer luminance/Patterson B2 luminance
Conversion factor= luminance of output phosphor/Input exposure rate
Brightness Gain= Flux Gain(inherent) x Minification Gain
1 input phosphor photon= 1 electron ejected= 50 output photons
Minification Gain= d1 squared/d0 squared
Brightness Gain= Always above 1000-6000
Image quality function of number of absorbed photons
Quantum noise/mottle/scintillation- eliminate by higher mA so more X ray quanta,
lesser with Zn Cd compared with CsI
Resolution 4 1p/mm
For input Phosphor; Thicker screen with large particle size= bright but less
resolution
Thinner screen with small particles= less bright but better resolution
Centre of Image brighter, less distortion and better resolution
Pincushion Distortion: curved surface of input phosphor/warped image
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FLUOROSCOPY EXAM CHEAT SHEET
OMAR CHOUDHRI
Higher kVp increased transmission
Brightness = mA X kVp5
Low Contrast images low kV
High Contrast images high kV
High kVp for reduced exposure and low kVp for best contrast
kVp degrades contrast
Ouput screen Luminance is measured in mililamberts
A brightness gain of 3000 will satisfy light requirements for photopic vision
Statistical quality of image can be improved by
-increasing X ray beam
-increasing Tube Current
-increasing quantity of incident Photon
-increasing X ray to light conversion efficiency
Chapter 2
Objective Lens and Camera Lens
Beam Splitter to direct portion of light into cine 70mm or closed circuit television
camera
F number= relative Aperture/speed= focal length/ diameter
Each successive number will require exposure time twice as long
Doubling the diameter will quadruple the light gathering ability ; D2
Chapter 3
525 scan line system
Vidicon camera surrounded by 2 types of coils: focusing and deflecting coils
Target assembly : Glass faceplate/signal plate and target
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FLUOROSCOPY EXAM CHEAT SHEET
OMAR CHOUDHRI
Vidicon target: thin film of photoconductive material made from antimony
trisulphite suspended as globules in mica matrix
Electrons released from electron gun by thermionic emission
Signal plate potential 25 volts compared to wire mesh 250 volts
Focusing coils and 2 pairs of deflecting coils
From vidicon tube to CCU (Camera Control Unit) which synchronizes and Television
Monitor
Each Television frame is 525 lines
Scanned 30 times per sec by electron gun
Frame = Field X 2
To avoid flicker effect: interlaced horizontal scanning
Bandwidth or Bandpass : frequency range or total number of cycles per second
available in the camera; 4.1MhZ
Horizontal resolution: Bandwidth or Bandpass
Brightness on television screen controlled by control Grid.
Frequency per line is a measure of horizontal resolving power of camera pickup
tube and camera
In the 525 scan line , 4.5MhZ TV system the amount of cycles to image one active
line is approx 803 cycles/line
Lag or stickness when camera moved
Types of Camera Tubes:
Vidicon Camera
Plumbicon Camera: PbO conductor, less lag and least patient exposure.
Image Orthicon Camera: larger, light & temp sensitive, works at lower illumination
levels, better resolution, no lag, more expensive, long warm-up time
Charged Coupled devices: small, low power, long life and no lag; used in high speed
imaging such as cardiac cath.
Kell Factor= Vertical Resolution/ scan lines = 0.7
Weakest Link in Image intensified change is TV system
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FLUOROSCOPY EXAM CHEAT SHEET
OMAR CHOUDHRI
Most important part of TV monitor is Cathode Ray Tube
Chapter 4
Recording head Gap Width 0.001mm
Video Disc Recorders used to record single fields, single frames or a short sequence.
Low Dose to patient
Spot Film Cameras and Cine Cameras record image from output phosphor of image
intensifer
Video Recordings are obtained from output of television camera tube
Underframing: poor optical system, avoid
Exact Framing: only 58% of frame used
Overframing: Part of Image Lost
Total Overframing: increases patient exposure
Check Calculation for skin exposure 3.6R/min
Cinefluororadiography equipment check once a year
Spotfilm Camera : Reduced cost, time and radiation exposure
Equipment requirements for fluoroscopy:
Fixed Table: Arthrogram, enterclysis, retained stone removal, biopsy and position of
tubes
Motor Table: ERCP, UGI, Tube CHolangiography, GB spot films, VCUG
Using a Spot film Camera film size with greatest dose to patient 105mm
Common video disc frame rate 30/sec
Cineradiography is influenced by synchronization, frame rate & f # of optical system
Chapter 5
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FLUOROSCOPY EXAM CHEAT SHEET
OMAR CHOUDHRI
TID (Time Interval Difference Mode) : insensitive to respiratory motion, cardiac
activity and motion artifacts
K Edge Image intensification: Using Cerium to isolate iodine signal, limited to X ray
tube power requirments
Subtraction of phase related sharp masks is necessary to minimize the unsubtracted
background
Logarithmic processing of data prior to subtraction is necessary to ensure that the
contrast will produce the same residual signal in the subtracted image
Typical X ray exposure for a left heart study is 200R
Conventional
Temporal
resolution
Spatial Resolution
Contrast
+/-
+
_
+
_
+/_
+
Cinefluoro
Computed
Tomography
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Chapter 6
Velocity of Light= wavelength X frequency
Thermionic Emission
Bremsstrahlung radiation 90%
Characteristic radiation
Increasing voltage , produces X rays of shorter wavelength and high Energy
Photoelectric effect: knocks off inner electron
Compton Effect: knocks off valence electron and original photon is scattered
Brems radiation transforms kinetic energy f the electron into radiant energy
Radiation capable of freeing electrons: ionizing radiation
Tube Current
Permeability of Xray determined by kV
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FLUOROSCOPY EXAM CHEAT SHEET
OMAR CHOUDHRI
Chapter 7
Exposure:
X ray intensity and quantity proportional to mA or tube current
Kilovoltage Peak Kvp determines quality of X ray, more penetrability
Collimation decreases exposure & quantum mottle
Filtration stops less penetrable rays; at least 2.5mm Al
Intensity of X ray Beam at the table top should not exceed 2.2R/min for each mA of
operating tube current at 80 kVp
With AEC limit of exposure 10R/min
Without AEC 5R/min
With Boost 5R/min
Monitor X ray tube current and potential at least once a week in 9inch water or 7
7/8 lucite phantom
1cm at under table X ray tube and 30cm when measuring overhead X ray tube
Target to panel distance should not be less than 18 inches and shall not ebe less
than 12 inches
For Boost fluoro : special activation at Control panel needed , audible signal, Table
top dose limited to 20R/ min unless recording devices used
Chapter 8
300 R temporary sterility in females
30R temporary sterility in males
Genetically significant dose: future children, X ray exam rate, mean gonadol dose per
exam
A dose of 50mRem delivered in a single exposure may result in cessation of sperm
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FLUOROSCOPY EXAM CHEAT SHEET
OMAR CHOUDHRI
At 25 Rads or Less ordinary laboratory or clinical methods show no indications of
biological injury
Cancer susceptibility from XRT decreasing order: Female breast, Thyroid,
Hemopoetic Tissue, lungs, GI , Bones
50 Rads to fetus involuntary abortion
Dose for Cataracts 200-250 Rads
The X ray tube housing must be constructed so that the leakage radiation at a
distance of 1 m from the target cannot exceed 100mR in 1 hr when the tube is
operated at 80kVP
Lead Apron/bucky and lead curtain,gloves and thyroid shields 0.25mm Lead
Exposure reduction 97%
When Fluoro tube working at 100kVP
1ft 500mR/hr, 2 ft 100mR/hr, 3 ft 50mR/hr
Mobile Screen desks 1-2mm lead
Gonad shield 0.5mm lead
135 degrees safe for operator
Pocket Ionization chambers: can be accidently discharged and min range
Whole Body Limits for rad equivalent 5Rem, extremities 50 Rem, Lens 15 Rem
mA during Spot filming 100-150mA
Numbers to Remember
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Fluoro xrays tubes operate at 125-150 kVp; 2-5 mA
Filtration must be at least 2.5mm Al equivalent
Filtration eliminate less penetrating xrays before patients are exposed
Intensity of xray beam at tabletop fluoro no greater than 2.2 Rads/min/mA (at
80kVp)
Source-to-tabletop = target-to-panel distance shall be >12inch; should be >18
inch
Increase image intensifier-to-pt distance increases pt dose
Carbon fiber table tops reduce pt dose
Primary protective barrier = image intensifier assembly, at least 2mm Pb equiv
Bucky slot cover / protective curtain/drapes at least 0.25mm Pb
Gonad shield at least 0.5mm Pb
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FLUOROSCOPY EXAM CHEAT SHEET
OMAR CHOUDHRI
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Routine fluoro: max allowable exposure rate = 5 Rad/min
With AEC, max exposure rate = 10 Rads/min; w/o AEC = 5 Rads/min
When boost is available, max exposure rate = 5 Rads/min
High Level (boost) fluoro: (10-50 Rads/min) 2-10 times higher dose than
conventional fluoro; max tabletop dose = 20 Rad/min when not using recording
devices
Cumulative manual-reset time = 5min
AEC=ABC: check current and potential qwk using phatom
Brightness gain = electronic gain (=flux gain from accelerating anode and output
phosphor) x minification gain (input diameter^2 / output screen diameter ^2)
Conversion factor is a measure of brightness gain = ratio of intensity of output
phosphor to input exposure rate
High kVp decreases subject contrast
Video Disc Recording (fluoro only on long enough to make 1 frame on TV
monitor) reduces pt dose by 95%
Spot Films w/ conventional cassettes >100 mA, high resolution, short exposure
Photospot camera less quality than conventional, ½ to 1/3 dose of spot films
Grids reduce scattered radiation from patient
Patient = source of scattered radiation, produced via Compton interaction
High kVp, large field size, thick body part increases scattered radiation
Magnification use higher voltage from electrostatic lens. 6inch mode mags from
9inch mode & increase pt dose by 2.25
Quantum mottle = quantum noise = scintiliation = more visible in high resolution,
high contrast sys
Modulation Transfer Function (MTF) expresses resolution (cesium iodide 4
lp/mm)
Brightness increases by square of kVp increase
Horizontal resolution depends on bandwidth
Vertical resolution depends on Kell factor (=vertical resolution / # scan lines
[525])
F-number(=focal length/lens diameter); lower f# -> more light, faster lens, less pt
radiation exposure
Brightness gain and contrast gain tested annually
Use lowest mA and highest kVp to minimize dose
Monitor TV monitor brightness/contrast daily
Wear lead if likely to receive more than 5mRad/hr
Overexposure notification: immediate if 25rem total, 75rem eye, 250rem skin;
24hr if 5rem total, 15rem eye, 50rem skin
Max occupational exposure = 5 rem/yr (over 18yo; <18yo = 10% of that dose)
General public exposure max 0.1 rem/yr = 0.002 rem/hr
High radiation area = may receive >0.1 rem/hr at 30cm from source
Radiation area = may receive > 0.005 rem/hr at 30cm from source
Gray = SI unit of absorbed dose: 1Gy = 100 Rads = 1J/Kg
Rad (Radiation Absorbed Dose) = special unit of absorbed dose: 1Rad =
100ergs/gm
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FLUOROSCOPY EXAM CHEAT SHEET
OMAR CHOUDHRI
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Rem = specialunite of dose equivalent (Rads x quality factor) : 1rem=0.01 sievert
Sievert = SI unit of dose equivalent (Gray x quality factor)
Quality factor for xray =1
Photoelectric effect = collision of xray photon with inner orbital electron,
knocking electron out of orbit, photon loses all energy
Compton scattering = xray photon hits outer orbital electron and making recoil
electron and decreasing photon energy
Pair production = incident photon is annihilated producing electron/positron
pair
10-14 days after onset of menses = improbably for pregnancy
Max dose during 9 months of pregnancy = 0.5 rem (+0.05rem if knowledge
delayed)
Ok if additional dose to embryo no more than 0.05rem during remainder of
pregnancy if dose is already 0.5rem at time of declaration of pregnancy
Phantom = 9inch water or 7.9 inch lucite
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