RADT 1010 Final Exam– Questions With Correct
Solutions
Production of xrays require four factors Right Ans - source of electrons,
target, high-voltage, vacuum
What is the envelope made of + the dimensions Right Ans - pyrex glass
or metal, 10'' long, 6'' central diameter, 2'' peripheral diameter
What purpose does protective housing serve? Right Ans - - controls
leakage and scatter radiation
- isolates high voltages
- provides means to cool tube
What controls leakage radiation and scatter radiation Right Ans - -
housing made of lead-lined cast steel
- leakage radiation limit (100 milliroentgens per hour at 1 meter)
What controls high-voltage isolation and tube cooling Right Ans - -
dielectric oil (insulates, promotes cooling)
- air fan
What is the cathode made up of Right Ans - - filament(s)
- focusing cup
- associated wiring
What must the filament do Right Ans - must provide enough resistance
to e- flow so that heat produced will cause thermionic emission (occurs @
2200 degrees)
filament material and why Right Ans - tungsten because it has high
melting point and difficult to vaporize. Can also be rhenium and
molybdenum.
Explain thermionic emission Right Ans - occurs when filament heated at
2200 degrees, causes electrons to be released from filament. when high
voltage released at exposure, e- are driven toward anode
,what causes tube failure Right Ans - - tube arcing (vaporized tungsten
collection on envelop)
- filament breakage (often due to boost and hold)
what is the focusing cup made of Right Ans - nickel or molybdenum
does a focusing cup have a high/low, negative/postivite potential Right
Ans - low negative
what is the mA for space charge effect Right Ans - maximum mA is
1000-1200
three functions of anode assembly Right Ans - - target surface
- conducts high voltage
- serves as primary thermal conductor
components of rotating anode assembly Right Ans - - anode
- stator
- rotor
Description of stator Right Ans - located outside envelope, is a bank of
electromagnets
description of rotor Right Ans - - is a copper cylinder connected to an
anode disk by a molybdenum stem.
- It turns when the stator is energized.
- contains ball bearings.
at what speed does the rotor turn at Right Ans - - 3200-3600 rpm
- 10000-20000 rpm high speed anodes
what is the rotating anode made of and why Right Ans - tungsten-
rhenium alloy, because it has high atomic number, high melting point, has
heat conducting ability
what temperature does the focal track get to Right Ans - reaches 1000-
2000 degrees in normal use
,what is the anode backed with and why is it backed Right Ans -
molybdenum and/or graphite. backing assists with heat loading
warmup procedure of anode benefits Right Ans - prevents cracking,
helps maintain vacuum, stress relieved anode
what is target area and what areas Right Ans - portion of anode that
electron stream contacts, point source of xray photons
- target, focus, focal point, focal spot, focal track
is a large or small focal spot better for life of anode Right Ans - large
focal spot is better for life of anode
what size focal spot is required for image quality Right Ans - small focal
spot
What is the line focus principle? Right Ans - by using a small anode
angle you can change the size of the effective focal spot (make it smaller for
better resolution) without increasing the heat and damaging the anode.
what is effective focal spot controlled by Right Ans - actual focal spot
and target angle
what are the diagnostic ranges Right Ans - 10-1200 mA
0.001 to 10 seconds
30-150 kVp
description of xray table Right Ans - uniform, radiolucent surface, easy
to clean, no crevices that could collect contrast media, contains bucky/IR
what are the different tube supports Right Ans - - overhead
- floor
- floor to ceiling
- mobile
- c-arm
what are the uses of upright units Right Ans - chest, abdomen, AC joints,
cervical spine
, how is shock hazard minimized from the high-voltage cables Right Ans -
1. insulation
2. grounded wire sheath
3. secondary side of high voltage transformer is grounded
what can be selected on operating console Right Ans - power on/off, kV,
mA, time, exam (hand, hip,etc.), AEC chambers, detector being used, focal
spot size, view worklist
exposure switch description Right Ans - deadman switch, pressing
halfway down starts rotor and filament boost circuit, depress in one
motion to maximize tube life
how long do moblie xray unit cord need to be Right Ans - mobile xray
exposure switch requires 3-meter cord
what does the generator do Right Ans - - supplies electrical power to
xray tube (high voltage b/w anode and cathode, filament voltage/current)
- controls exposure timing (turns exposure on and off, high voltage
switched on and off)
what does the main xray circuit contain Right Ans - exposure switch,
timer circuit
incoming line current description Right Ans - - 60 Hz alternating
current (mains supply/incoming line current; 3-phase)
- 120 V
- will be converted to high voltage and to high current in different parts of
the xray circuit
line compensation description Right Ans - - most imaging systems
operate on 220 V (some 110 or 440)
- incoming power is not always accurate
transformer description Right Ans - - principle components of xray
generators
- convert low voltage to high voltage through electromagnetic induction
Solutions
Production of xrays require four factors Right Ans - source of electrons,
target, high-voltage, vacuum
What is the envelope made of + the dimensions Right Ans - pyrex glass
or metal, 10'' long, 6'' central diameter, 2'' peripheral diameter
What purpose does protective housing serve? Right Ans - - controls
leakage and scatter radiation
- isolates high voltages
- provides means to cool tube
What controls leakage radiation and scatter radiation Right Ans - -
housing made of lead-lined cast steel
- leakage radiation limit (100 milliroentgens per hour at 1 meter)
What controls high-voltage isolation and tube cooling Right Ans - -
dielectric oil (insulates, promotes cooling)
- air fan
What is the cathode made up of Right Ans - - filament(s)
- focusing cup
- associated wiring
What must the filament do Right Ans - must provide enough resistance
to e- flow so that heat produced will cause thermionic emission (occurs @
2200 degrees)
filament material and why Right Ans - tungsten because it has high
melting point and difficult to vaporize. Can also be rhenium and
molybdenum.
Explain thermionic emission Right Ans - occurs when filament heated at
2200 degrees, causes electrons to be released from filament. when high
voltage released at exposure, e- are driven toward anode
,what causes tube failure Right Ans - - tube arcing (vaporized tungsten
collection on envelop)
- filament breakage (often due to boost and hold)
what is the focusing cup made of Right Ans - nickel or molybdenum
does a focusing cup have a high/low, negative/postivite potential Right
Ans - low negative
what is the mA for space charge effect Right Ans - maximum mA is
1000-1200
three functions of anode assembly Right Ans - - target surface
- conducts high voltage
- serves as primary thermal conductor
components of rotating anode assembly Right Ans - - anode
- stator
- rotor
Description of stator Right Ans - located outside envelope, is a bank of
electromagnets
description of rotor Right Ans - - is a copper cylinder connected to an
anode disk by a molybdenum stem.
- It turns when the stator is energized.
- contains ball bearings.
at what speed does the rotor turn at Right Ans - - 3200-3600 rpm
- 10000-20000 rpm high speed anodes
what is the rotating anode made of and why Right Ans - tungsten-
rhenium alloy, because it has high atomic number, high melting point, has
heat conducting ability
what temperature does the focal track get to Right Ans - reaches 1000-
2000 degrees in normal use
,what is the anode backed with and why is it backed Right Ans -
molybdenum and/or graphite. backing assists with heat loading
warmup procedure of anode benefits Right Ans - prevents cracking,
helps maintain vacuum, stress relieved anode
what is target area and what areas Right Ans - portion of anode that
electron stream contacts, point source of xray photons
- target, focus, focal point, focal spot, focal track
is a large or small focal spot better for life of anode Right Ans - large
focal spot is better for life of anode
what size focal spot is required for image quality Right Ans - small focal
spot
What is the line focus principle? Right Ans - by using a small anode
angle you can change the size of the effective focal spot (make it smaller for
better resolution) without increasing the heat and damaging the anode.
what is effective focal spot controlled by Right Ans - actual focal spot
and target angle
what are the diagnostic ranges Right Ans - 10-1200 mA
0.001 to 10 seconds
30-150 kVp
description of xray table Right Ans - uniform, radiolucent surface, easy
to clean, no crevices that could collect contrast media, contains bucky/IR
what are the different tube supports Right Ans - - overhead
- floor
- floor to ceiling
- mobile
- c-arm
what are the uses of upright units Right Ans - chest, abdomen, AC joints,
cervical spine
, how is shock hazard minimized from the high-voltage cables Right Ans -
1. insulation
2. grounded wire sheath
3. secondary side of high voltage transformer is grounded
what can be selected on operating console Right Ans - power on/off, kV,
mA, time, exam (hand, hip,etc.), AEC chambers, detector being used, focal
spot size, view worklist
exposure switch description Right Ans - deadman switch, pressing
halfway down starts rotor and filament boost circuit, depress in one
motion to maximize tube life
how long do moblie xray unit cord need to be Right Ans - mobile xray
exposure switch requires 3-meter cord
what does the generator do Right Ans - - supplies electrical power to
xray tube (high voltage b/w anode and cathode, filament voltage/current)
- controls exposure timing (turns exposure on and off, high voltage
switched on and off)
what does the main xray circuit contain Right Ans - exposure switch,
timer circuit
incoming line current description Right Ans - - 60 Hz alternating
current (mains supply/incoming line current; 3-phase)
- 120 V
- will be converted to high voltage and to high current in different parts of
the xray circuit
line compensation description Right Ans - - most imaging systems
operate on 220 V (some 110 or 440)
- incoming power is not always accurate
transformer description Right Ans - - principle components of xray
generators
- convert low voltage to high voltage through electromagnetic induction
