CH 5 Flashcards
Converts 220 volts of AC to DC
High Voltage Generator
The generator is a ___ component of the imagin system, not under control of the technologist.
Fixed
Name the 3 basic generating systems:
1)Single Phase 2) Three Phase 3)High Frquency
Generator affects what in regards to photons?
Quality and quantity
Generator purpose and alternate name?
Device that converts mechanical energy to electrical energy. AKA Dynamo
The unit for frequency is?
Hertz
The frequency of the sine wave is determined by?
The # of cycles per second
How many times per/second do the electrons in a 60 Hz alternating current change their direction of movement?
60 times
Hertz is also known as
Pulses, impulses or alternations
During half wave rectification photons are produced and emitted during?
the positive cycle
Full Wave Rectification is?
The same as the half wave except there is no “dead time”
What does 3 phase rectification result in? (6 and 12 pulse)
In higher quality and quantity photons
High frequency means
A “nearly” constant positive voltage, less than 1% ripple
Single phase generators have how much ripple?
100% ripple
3 phase 6 pulse generators have how much ripple?
14% ripple
3 phase 12 pulse generators have how much ripple?
4% ripple
High frequency generators have how much ripple?
1% ripple
What generating system has the highest frequency rating when creating x-ray photons?
High Frequency
Where does power for x ray generating systems come from?
Normal incoming household line, which is 120 volts of AC.
Nearly all x-ray equipment works within
210-220 volts
All rad tech operated controls are in the
low voltage side of the circuit, this is done to prevent high voltage shock hazard.
Dead man type switch
Requires constant pressure.
By law the control consule must have:
mA, kV meter and a timer,
All tranformers run on what kind of current?
AC
Transformers are need to?
Increase of decrease the voltage.
Types of Transformers
Auto-Tranformers, Step up (or High Tension), Step Down (Low Filament)
Tranformer Law Formula
(Vs/Vp)=(Ns/Np)
Most xrays in the diagnostic energy range are created from
Brem’s and Characteristic
Brems entails the:
Breaking or slowing of electrons.
Electrons come from what end of the tube?
The Cathode.
The focusing cup is what kind of charge?
Negative
Thermoionic Emission
Heat builds up creating a boiling over.
Thermoionic Emission is also known as?
Space Charge and Electron Cloud
What directly influences radiation dose to the patient?
mAs
Double mA or time will do what to the radiation dose to the patient?
Double the dose
What kind of device should be used to aid in the setting of mAs to reduce unnecessary repeats?
Calipers
What is directly responsible for the quality or the energy of the beam?
kV
The energy of the beam is also known as?
Penetrating Power
An increase in penetrating abilities is due to?
Increase in kV
Electrons moving faster in the tube from the cathode to anode is due to?
Increase in kV
The faster the electrons move the higher
the quality of x-rays we have
A voltage meter measures what?
Volts
Optimum kV techiniques:
What we must always practice, when making an exposure on a patient. Smallest amount of radiation.
Optimum kV is what kind of principle?
ALARA
Power ratings for Single units Formula
VxAx0.7=Watts
Single Phase Rectified Unit Formula
mAxSxkV=HU
Three phase 6 pulse Unit Formula
mAxSxkVx1.35=HU
High Frequency Heat unit formula?
mAxSxkVx1.40=HU
AEC (Automatic Exposure Control)
Controls time only, automatically terminates the exposure once enough x rays have penetrated a specific part being radiographed.
AEC is also known as:
Phototimer and Ionizing Chamber
Minumum Reaction time
Length of time needed for AEC to respond to radiation and for the generator to terminate the exposure.
Back up time
Times that cannot exceed tube limit and should be set at 150% of the anticipated manual exposure mAs.
Backup time is designed to do what?
Prevent over exposure.
What are the 3 basic components to create X-rays
1)Source of electricity 2)mA and kV 3)X-ray tube consisting of a cathode and an Anode (source and target) .
Fillament or dual filament is found on what side of the tube?
Cathode
Filament is made of
Tungsten
What is the anode made of?
Tungsten and enhanced with rhenium-alloy
How thick is the anode?
5-13 cm
What is used as the target focal track material?
Tungsten
Area of bombardment is called?
Target, focus, focal point, focal track, and focal spot (any of these)
Ionization is
The addition of or subtraction of an electron from an atom
Bremsstrahlung is a form of?
Electromagnetic radiation.
Brems is the
Sudden deceleration of electrons interacting with the Tungsten Anode
X-rays from what kind of beam?
Polyenergetic/Polychromatic/Heterogeneous
Photons are
Bundles of energy that travel in waves.
5 types of interactions with matter are:
Coherent, Photoelectric, Compton, Pair Production, Photodisintegration.
X-ray properties
Invisible, Neutral, No mass, Travel at Speed of light, Cant be optical focused, form polyenergetic beam, penetrates matter, can produce Secondary scatter radiation, can cause substance fluoresence (glow), Can cause biological effects.
