Chapter 6: X-Ray Equipment Flashcards
Two types of tables:
Diagnostic and Therapeutic
diagnostic table
diagnostic ranges
10-1200 mA
0.001-10 s
25-150 kVp
therapeutic table
- Radiation oncology
o Capable of x-ray and electron therapy
o MeV energies
List characteristics of the tables:
-uniform, radiolucent surface
-flat surface
- 4 way table top motions
-bucky tray
-variable heights
-fixed and tilting models
what is the correct order when image is taken:
tube -> pt. -> table -> grid -> AEC -> IR
what are the numerous configurations of tube supports
-overhead 3D tubecrane suspension
-floor to ceiling
-floor mounted
-mobile
- Carm
- Supports image receptor in a vertical orientation
o Bucky assembly
o May include AEC - Vertical travel
- Tilting or nontilting
upright receptor units
Specialized Diagnostic Equipment
- Mammography
- Tomography
- Dental/panoramic
- Computed tomography (CT)
- Radiation therapy simulators
- Urologic
Inefficient x-ray production
Single-phase power
o Most popular and widely available
- Three-phase power
standard power for xray generation
220V coming in
60 Hz alternating current
nearly all xray equipment operates on WHAT VOLTAGE :
210- 220V
voltage for 3 phase
440–480 V 3-phase
what voltage ripple is produced in the single phase
Single-phase
produces 100%
voltage ripple
- 3-phase power produces
very low voltage ripple - Most efficient type of
electrical power - Used with high-end
electrical devices
o x-ray machines
multi-phase power
what phase does not drop back down to 0
multi- phase power
o High voltage side of circuit
o Exposure switch
o Timer circuit
- Main x-ray circuit
what phase is more efficient and most popular and widley avialble
3 phase
what is your undirectional
undirectional = direct current= rectified
what is your high voltage side
secondary
what is your low voltage side
primary
where is your exposure switch
primary
where is your time switch
primary
o Low voltage side of circuit
o Provides current and voltage to filament
o Permits selection of milli-amperage (mA)
Filament circuit
what voltage side is the filament circuit
Low voltage side of circuit
what is happening to your current and thermionic emission in filament circuit
increasing
how is your voltage and amps in the filament circuit
decreased voltage and increased amps
what circuit provides current and voltage to filament and permits selection of mA
filament circuit
what is your exposure switch
deadmans switch (pressure needs to be applied)
- Deadman switch
- Located behind control window on generator console
- Depress in one motion to maximize tube life
o X-ray exposure initiated automatically after rotor is at correct
rpm’s
exposure switch
how long is the cord for mobile equipment
6 feet
how long is the cord in the xray room
1 foot
- Regulates exposure termination
- Electronic timers
o Most sophisticated - Capable of very short exposure times
o 0.001 second - Milliampere-second (mAs) timers
o Terminates exposure based upon a predetermined mAs value - AEC timers
Timer circuit
list type of generators
- Single-phase
- Multi-phase
- 3-phase
- High frequency
- Capacitor discharge mobile units
- Battery-operated mobile units
- Falling load
what type of generator is described here:
* Full-wave rectified
o 2 pulses per Hz
o 120 pulses per second
o Voltage ripple 100 percent
single phase generator
what type of generator is described here:
* Full-wave rectified with 6 diodes
o 6 pulses per Hz
o 360 pulses per second
o Voltage ripple 13–25 percent
Multi-Phase/Three-Phase Generators
3 phase 6 pulse
what type of generator is described here:
* Full-wave rectified with 12 diodes
* 12 pulses per Hz
* 720 pulses per second
* Voltage ripple 4–10 percent
Multi-Phase/Three-Phase Generators
3 phase 12 pulses
pulses is also known as :
diodes
voltage ripple for single phase
100 percent
voltage ripple for 3 phase 6 pulse
13 to 25 percent
voltage ripple for 3 phase 12 pulse
4 to 10 percent
voltage ripple for high frequency
1% most efficient
AC and DC power converters and inverters
o Convert 60 cycle to kilohertz (kHz)
o Full-wave rectified unit can produce 12–13 kHz waveform
o Voltage ripple of 3–4 percent
o Most popular and common type of generator
o Most efficient x-ray production
High-Frequency Generators
- Requires precharging a large
electrical capacitor - Battery charging
- Produce a current-wavetail
after exposure termination - Delivers a lower rms voltage
and lower output - Typically use a grid-biased xray tube
Capacitor Discharge Mobile Units
-Terminate exposure based upon a predetermined exposure value
Controls only exposure time
-Commonly called phototiming
- Ionization chambers
- Minimum reaction time
-Backup time
AEC
- Located in front of image receptor
(IR) - 5-mm parallel-plate chamber
- Radiolucent at correct kVp’s
- Typically have three detector
positions - Not used with distal extremities
Ionization Chambers
- Minimum amount of time required to terminate exposure in AEC
Minimum Reaction Time
- Used to protect patient and equipment
- Equipment often allows technologist to set backup
o Should be set at 150 percent of anticipated manual technique - Maximum exposure per U.S. Public Law:
o 600 mAs - Exposures >50 kVp
Back up time circuit
