rad tech a week 2 radiographic equipment spring 2009
TRANSCRIPT
OBJECTIVES• IDENTIFY GENERIC
COMPONENTS OF THE RADIOGRAPHIC EQUIPTMENT
• DESCRIBE VARIOUS PLANES OF X-RAY TUBE AND TABLE MOVEMENT
A look inside the body
• X-rays are a form of electromagnetic energy. X-rays have high enough energy to penetrate the human body leaving different densities on the image below
• Dependant on the Z# of the material
The Electromagnetic Spectrum• X-rays have wavelengths much shorter than
visible light, but longer than high energy gamma rays
MEASURED IN ANGSTROM 0.1 – 0.5 FOR X-RAYS
THE X-RAY TUBE
• The X-Ray tube is the single most important component of the radiographic system. It is the part that produces the X-rays
How “X-rays” are createdSEE: MAN MADE RADIATION (PG.93)
TO PRODUCE X-RAYS
YOU NEED:
• A SOUCE OF ELECTONS
• A FORCE TO MOVE THEM QUICKLY
• SOMETHING TO STOP THEM SUDDENLY
PRODUCTION OF X RAYS
Requirements:
– a source of fast moving electrons
– must be a sudden stop of the electrons’ motion
– in stopping the electron motion, kinetic energy (KE) is converted to EMS energies
• Infrared (heat), light & x-ray energies
How Are X-rays Made?• X-rays are produced
when electrons strike a metal target.
• The electrons are released from the heated filament and accelerated by a high voltage towards the metal target.
• The X-rays are produced when the electrons collide with the atoms (electrons) of the metal target.
How “X-rays” are created
• Power is sent to x-ray tube via cables
• mA (milliamperage) is sent to filament on cathode side.
• Filament heats up – electrons “boil off”
• Negative charge
Tungsten
• Filaments are usually made of tungsten
• Tungsten provides higher thermionic emission than other metals
• Tungsten has a very high melting point
Filament
• When current (mA) is applied to the coil of wire electron are ejected
• The outer-shell electrons of the filament atom are “boiled off”.
– This is known as thermionic emission
Focusing cup
• The filament is embedded in a metal cup that has a negative charge
• Boiled off e- tend to spread out due to electrostatic repulsion. The focusing cup confines the e- cloud to a small area
How “X-rays” are created
• Positive voltage (kVp) is applied to ANODE
• Negative electrons = attracted across the tube to the positive ANODE.
• Electrons “slam into” anode – suddenly stopped.
• X-RAY PHOTONS ARE CREATED
Anodes - Target
Cu
W
•Common target material is Tungsten• Electrons interact with W – photons created
Molybdenum or Graphite base
Rotating Anodes• 2” to 5” disk (focal track)• Induction motor
• Speed 3000 to 10000 rpm
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X-ray Production
• electrons move at high speed (kV)
• collide with target on anode
• kV of electrons converted to x rays & heat
electronsanode
target
How “X-rays” are created
• Electron beam is focused from the cathode to the anode target by the focusing cup
• Electrons interact with the electrons on the tungsten atoms of target material
• PHOTONS sent through the window PORT – towards the patient
XRAY TUBE HOUSING
• MADE OF LEAD AND STEEL
• TO ABOSRB ANY STRAY RADIATION
• TO PREVENT X-RAY PHOTONS TO LEAK FROM THE TUBE
X-RAY TUBE
• MADE OF PYREX GLASS TO WITHSTAND HIGH HEAT LOAD
• IS GAS EVACUATED – (so electrons won’t collide with the air
molecules in the tube)
X-ray Tube Construction
A. GLASS HOUSING (ENVELOPE)
B. MOLYBDENUM NECK OF ANODE
C. STATORS /ELECTROMAGNETS
D.TUNGSTEN ANODE (FOCAL SPOT)
E. WINDOW OR PORT FOR BEAM EXIT
F. FILAMENT (CATHODE)
G. FOCUSING CUP
Radiographic tables
Are designed to support the patient during a radiographic exam
Comfort is not the primary concern Foam pads should be used if the
patient will be required to be on the table for longer than 10 minutes
Tabletop
Must be uniformly radiolucent to easily permit x-ray to pass through.
Carbon fiber is used because it is strong and very little x-ray photons are absorbed.
Usually tabletops are flat however some are curved
Tabletop
Most tabletops are floating, some are motor-driven
The brakes can be released usually by the technologist hand or foot
The brakes are electromagnetic Floating table tops save significant
amounts of time and strain on the technologist
Tables
• Tilting rooms are designed for both diagnostic and fluoroscopic work– Tilting models usually tilt to 90 degrees in
one direction and 15 – 30 degrees in the other direction
– Tilting models include ancillary equipment; footboard, shoulder support, handgrips, compression bands
Tube Supports
• Designed to help technologists with various tube locations for creative imaging.
• Tube suspension systems are available in 5 versions:– ceiling mounted, floor-to-ceiling, floor, mobile
and c-arm.
The ‘BUCKY’
• The bucky is the device in the table or chest board that holds the film cassette. The ‘bucky’ is like a drawer that opens and closes to insert and remove the film cassette.
COLLIMATOR
• ATTACHES DIRECTLY BELOW THE X-RAY TUBE
• SERVES AS A X-RAY BEAM LIMITING DEVISE
• CONTROLS THE SIZE AND SHAPE OF X-RAY FIELD
RADIOGRAPH• PERMANENT RECORD MADE USING
RADIATION
– RADIO- RADIATION (usually x rays)
– GRAPH PERMANENT RECORD (film)
CASSETTE or FILM HOLDER
• The CASSETTE is used to hold the film during examinations. It consist of front and back intensifying screens, and has a lead (Pb) backing. The cassette is light tight
CONTROL CONSOLE
• GIVES THE TECHNOLOGIST CONTROL OF THE X-RAY MACHINE
• TECHNIQUE SELECTION
• Located OUTSIDE of the Radiographic Room
The Control Console
• The control console is device that allows the technologist to set technical factors (mAs & kVp) and to make an exposure.
• Only a legally licensed individual is authorized to energize the console.
“Technique”kVp , mAs (mA x s)
• What is set at the control panel
• How the “image” is created on the “film” or Image receptor (digital)
• kVp controls the “ENERGY” of the beam
• The Higher kVp – more penetrating
• Ranges is 50 -110 in Diagnostic x-ray
“Technique”kVp , mAs (mA x s)
• mA- is the current in combination with the time – determines HOW LONG the beam will stay on
• Controls the density on the film/image
Why you see what you see
• The films or images have different levels of denisty – different shades of gray
• X-rays show different features of the body in various shades of gray.
• The gray is darkest in those areas that do not absorb X-rays well – and allow it to pass through
• the images are lighter in dense areas (like bones) that absorb more of the X-rays.
IMAGES
• DENSITY = THE AMOUNT OF BLACKENING “DARKNESS” ON THE RADIOGRAPH - mAs controlled
• CONTRAST – THE DIFFERENCES BETWEEN THE BLACKS TO THE WHITES - kVp controlled
Safe Light
• 15 Watts
• Red filter
• Must be 3-6 feet from counter top or feed tray of processor
• Used to be amber or orange filter
RTA LAB 1 : EQUIPMENT
• Next week…..
• TOUR OF THE IONIZING LAB HERE ON CAMPUS.
• COMPLETE IN CLASS WORKSHEET FOR TERMINOLOGY