Physics - Chapter 6 Flashcards
What kvp do imaging systems usually operate between?
25-150 kvp
What is the tube current in an imaging system?
100-1200mA
What shape is an xray couch/table?
Flat or curved
How far can a fluoroscopy table tilt toward the feet?
90 degrees
How far can a fluoroscopy table tilt toward the head?
30 degrees
What is a common material for an xray table to be made of?
Carbon Fiber
What are the 3 principle part of an xray imaging system?
Xray tube
Operating console
High voltage generator
What does Theo operating console allow technologists to control?
Xray tube current and voltage
What is xray quantity?
Intensity (mAs)
What is xray quality?
Penetrability (kvp)
How many volts are xray imaging systems designed to operate at?
220V
Some can operate at 110V or 440V
What percent can the voltage vary by in a hospital? Why?
Up to 5%
Electric power companies are not capable of providing 220V accurately and continuously
What part of the operating console measure the voltage provided to the xray imaging system and adjusts that voltage precisely to 220V?
Line compensator
Has only one winding and one core
Autotransformer
Designed to supply a precise voltage to the filament circuit and to the high voltage circuit of the xray imaging system
Autotransformer
T/F
The primary voltage and the secondary voltage in an Autotransformer are directly related to the number of turns of the transformer enclosed by the respective connections
True
What does the major kvp selector do?
Gives a broad selection of kvp technique
What does the minor kvp selector do?
Fine tunes the selected technique
What is the filament current measured in?
Amperes (A)
What current do filaments usually operate at?
3-6A
Tube current
mA
Tube voltage
kV
Line compensation
kV
Lower the voltage for safer use and manipulation
Autotransformer
What is the full name for a filament transformer?
Filament heating isolation step-down transformer
What does the filament transformer step the voltage to?
Approx. 12V
What is the current and voltage in the primary windings of a filament transformer?
0.5A - 1A
150V
What is the current and voltage in the secondary windings of a filament transformer?
5A - 8A
12V
What are the most accurate type of timer?
Electronic
Uses synchronous motor as timing mechanism
Minimum exposure time = 17 ms
Synchronous
Monitors the product of mA and time
Terminates exposure when specific mAs is obtained
Milliampere-second timer
Measures quantity of radiation that reaches the IR
Exposure automatically terminates when required intensity has reached IR
AEC
What are the 3 parts of a high voltage generator?
High voltage transformer
Filament transformer
Rectifiers
The process of converting AC to DC
Rectification
What type of transformer is the high voltage transformer?
Step up
What is the turns ratio of a high voltage transformer usually between?
500:1 and 1000:1
What is responsible for increasing the output voltage from the autotransformer to the kvp necessary for xray production?
High voltage generator
What is the oil primarily used for in a high voltage generator?
Primarily used for electrical insulation
What is the primary voltage in a high voltage transformer measured in?
Volts
What is the secondary voltage measured in in a high voltage transformer?
Kilovolts
What is the primary current measured in in a high voltage transformer?
Amperes
What is the secondary current measured in in a high voltage transformer?
Milliamperes
What type of current is required for an xray tube?
DC
What is required to ensure that electrons flow from cathode to anode only
Voltage rectification
What results from single phase power?
Pulsating xray beam
What is a disadvantage of a single phase power supply?
Xrays produced during the lower part of the voltage cycle have low penetrability
Multiple voltage waveforms are superimposed on one another, resulting in a waveform that maintains a nearly constant high voltage
Three phase power supply
What are the limitations of three phase power supply?
Initiation time and extinction time
Generator producing a nearly constant potential voltage waveform, improving image quality and lowering patient dose
High frequency
What is the converted frequency in a high frequency generator?
500-25 000 Hz
Variation between minimum and maximum voltage
Voltage ripple
T/F
Less voltage ripple leads to better beam quality/quantity
True
100% voltage ripple
Single phase
14% voltage ripple
Three phase, six pulse
4% voltage ripple
Three phase, twelve pulse
1% voltage ripple
High frequency
High voltage generator power(kW) = maximum tube current (mA) at 100kvp and 100ms
Power rating
What is the power rating for basic radiography?
30-50kW
What is the power rating for interventional radiography?
Up to 150kW
