Introduction to Clinical Radiography

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Introduction to Clinical Radiography

• RADI R103
• SSII
• Unit I Terminology Equipment

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Introduction to Clinical Radiography

• Unit I
• Lecture 3 -- Equipment

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Equipment

• to produce x rays
• to record the image
• to control size shape of beam
• accessories patient comfort items
• to process the image

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X-Ray Producing Equipment

• x-ray tube
• high voltage generator
• control console

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X-Ray Tube

• Glass vacuum diode tube

• cathode
• negative electrode
• source of electrons
• 2 filaments (coils)

• anode
• positive electrode
• attracts stops electrons

cathode -
anode
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X-ray Tube
anode
cathode
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ANODE

• target
• Area on anode where electrons stop
• focal spot
• Area on target that emits the x rays
• types of anodes

Rotating Anode
Stationary Anode
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What Happens in an X-Ray Tube

• cathode -- supplies e-
• anode -- attracts e-
• electrons -- move at high speed (KE) to target
• -- collide with target
• -- KE of e- changed to x rays heat
• x rays -- emitted isotropically at focal spot
• unusable -- x-rays absorbed by tube shielding

çe-
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Protective X-Ray Tube Housing

• Surrounds tube
• Lead
• Small opening allowing beam of x rays to exit
• Shield to absorb x rays not used
• Leakage radiation - x rays that penetrate the
  housing

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High Voltage Generator

• provides power to move (accelerate) electrons
  from cathode to anode
  
• 40,000 to 150,000 volts (40 TO 150 kVp)
• 1,000 volts 1 kVp
• v to kV ? 1000
• kV to V ? 1000
• connected to x-ray tube with high tension cables

-

HV generator
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Control Panel (Console)

• MANY VARIATIONS
• knobs vs. buttons, etc.
• Touch-screen type control panel

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CONTROL CONSOLE or PANEL

• MAIN ELEMENTS
• main power switch (circuit breaker near
  console)
  
• ON/OFF (on the console)
• Technique controls (kV, mA, t, etc.)
• Exposure controls
• Equipment operation indicators

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kVp SELECTION

• kVp used to control ENERGY LEVEL of x rays
• PENETRATION (QUALITY) OF BEAM
• main control for image CONTRAST
• selection in unit value range from 40 kVp to 150
  kVp
  
• Increments major 10 kVp minor 1 kVp

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mA SELECTION

• MILLIAMPERAGE
• 1A 1000 mA A ? 1000 mA
• 1mA 0.001 A mA ?1000 A
• amperage of e- flowing in a current
• controls of x rays produced
• QUANTITY OF X RAYS IN BEAM
• main control for image DENSITY
• SELECTOR (stations)
• limited to specific values

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TIME SELECTION

• length of time machine produces x rays
• fractional vs. decimal vs. millisecond
• range of selections usually at specific values
• not same on all machines

Decimal Timer Selections
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Time Conversions
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mA Time work together

• combined for total control on QUANTITY
• mA of e- (per second of time)
• time duration
• Relative value for total of x rays
• mAs mA X t (t in decimal or fraction)
• when é mAs similar é in of x rays
• 2x mAs 2x of x rays

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What is the mAs for 300 mA at 6 ms?

• mAs mA x t
• t 6?1000 .006 s
• 300mA x .006 s
• 1.8 mAs

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Focal Spot Selection

• activates small or LARGE filament in cathode
• ê or é size of focal spot emitting x rays
• small FS sharper image
• more tube wear
• LARGE FS less sharp image
• less tube wear

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Exposure Activating Switch

• Two Position Safety Control
• 1 prepares tube for x-ray production
• a. rotates anode to correct speed
• b. heats selected cathode filament (release e-)
• 2 produces x rays
• "DEAD MAN" type safety switch
• - operator must use both positions in order
• - operator must continue to hold switch for time
  set
  
• - will not allow continuous or double exposures

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EXPOSURE NOTIFICATION METHOD

• positive indicator of x ray production
• multiple methods
• audible
• sound during or at end of exposure
• visible
• light
• meter
• combined -- audible visible

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Sample Technique ChartHand