Chapter 6: The x-ray tube

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60 terms · Physics final study guide

source of electrons, target, high-voltage, and vacuum

What are the 4 things needed to produce x-rays?

filament

What is the source of electrons in the x-ray tube?

anode

What is the x-ray tube target called?

filament, focusing cup, and associated wiring

What are the three parts of the cathode assembly?

nickle

What is the focusing cup generally made out of?

focal spots

What are the associated wiring in the cathode assembly?

thoirated tungsten

The filament is a coil of ___ ___.

recorded detail

The filament length and width impact what?

high melting point and difficult to vaporize

What are the two main reasons tungsten is selected as the filament material?

rhenium and molybdenum

What are two other good choices, besides tungsten, for the filament material?

dual focus

What is the term used to describe the type of x-ray tubes that have two focal spots, one large and the other small, as well as two filaments, one large and the other small.

thermionic emission

What is the process of electrons being released from the filament as it is heated called?

tube arcing

What is the name of the tube failure where vaporized tungsten is collected on the envelope?

filament breakage

What is the name of the tube failure that occurs from "boost and hold"?

space charge effect

The negatively charged focusing cub compresses the thermionic cloud. This process is known as what?

biased focusing cup

A ___ ____ ____ maintains the focusing cup at a more negative voltage than the filament (used in mammography).

saturation current

What is the filament phenomenon that has been achieved when there are no further thermionic electrons to be driven toward the anode?

target surface, conducts high voltage, and primary thermal conductor

What are the three functions of the anode assembly?

anode, stator, and rotor

What are the 3 components of the anode?

stationary and rotating

What are the 2 different types of anode?

tungsten-rhenium alloy

Rotating anodes are composed of _______ ____ because it has a high z#, melting point, and heat-conducting ability.

anode layering

What assists with heat loading for the anode?

molybdenum or graphite

With a layered anode, the tunsten is usually backed with what?

molybdenum

What is the target material used for mammographic equipment?

lower

Mammographic equipment requires (lower / higher) energy photons?

beryllium

What material is the tube window made out of for mammographic equipment?

warm-up procedure

What gradually warms up the anode and helps maintain the vacuum?

cracking

Warming up the tube prevents what from occuring?

target area

What is the portion of the anode that the electron steam contacts?

focal track

What is the circular path that is impacted by the electron beam for a rotating anode?

rotating anode

What type of anode dissipates heat more effectively?

actual

Which focal spot is the area on the anode that is impacted?

effective

Which focal spot is the area on the IR that results?

Line focus principle

What is the relationship between the actual and effective focal spot called?

actual focal spot and target angle

The effective focal spot is controlled by what two things?

isotropically

X-rays are emitted _____.

smaller, better

A smaller target angle has a ____ effective focal spot and ____ detail.

SID

What is the distance between the IR and X-ray tube?

SOD

What is the distance between the x-ray tube and object?

OID

What is the distance between the object and image receptor?

large, small

A ____ IR and ____ SID will show a noticible effect from the anode heel effect.

cathode

The anode heel effect states that more x-rays escape on which side?

less

Move of a target angle has (more / less) impact with the anode heel effect.

electromagnets

The stator is a bank of _____ located outside the envelope?

copper

The rotor is made of what material?

rotor

What turns the staor when energized?

ball bearings

What part of the rotor reduce friction or heat?

pyrex glass or metal

What is the envelop made out of that is ease to mold and easy for x-rays to pass through?

window and vacuum

The envelope contains what two important parts of the x-ray tube?

protective housing

What controls leakage and scatter radiation?

high

The protective housing isolates (high / low) voltages.

lead-lined cast steel

The protective housing is made of what?

100 mR/hour

The leakage radiation limit for the protective housing is ______ at 1 meter?

dielectric oil

What surrounds the envelope and is used to insulate, promote cooling, and is sometimes circulated trhough a heat exchanger?

tube rating chart

What chart or graph is used to determine how much heat or exposure a tube can take?

anode cooling curves

What chart or graph is used to determine how long to wait until another exposure can be taken?

kVp x mA x time x rectification constant

How do you determine the heat units?

1

What is the rectification constant for a single phase generator?

1.35

What is the rectification constant for a three phase generator?

1.4

What is the rectification constant for a HF generator?

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