Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Rad 102: Intro to radiologic technology > The X-Ray Tube > Flashcards

The X-Ray Tube Flashcards

1
Q

What is the cathode?

A

the negative side of an x-ray tube. Its function is to produce a thermionic cloud

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the filament?

A

A small coil of thin thoriated tungsten wire. It is set in the cathode assembly within the focusing cup

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why is tungsten the material of choice for the filament?

A

because it has a high melting point of 3,370 degrees and it is difficult to vaporize.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why are rhenium and molybdenum also desirable xray tube materials?

A

because of their high melting points. Rhenium = 3170 degrees and molybdenum is 2620 degrees.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Most x-ray tubes have dual filaments, what is this called?

A

Dual focus arrangements

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the function of the filament?

A

to provide sufficient resistance to the flow of the electrons so that the heat produced will cause thermionic emission to occur

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is one of the primary causes of premature tube failure?

A

the radiographer’s habit of holding the rotor switch prior to making exposures. Every second the switch is depressed, life is removed from the filament.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What do most tube manufacturers recommend to avoid premature tube failure?

A

they recommend that two step exposure switches be fully
depressed in one motion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the focusing cup?

A

a shallow depression in the cathode assembly designed to house the filament

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the purpose of the focusing cup?

A

it is provided with a low negative potential. As more and more electrons build up in the area of the filament, their negative charges begin to oppose the emission of additional electrons. this is called a space charge affect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the anode?

A

the positive side of the x-ray tube. It has three functions:

serves as a target surface for the high voltage electrons from the filament, there by becoming the source of the x-ray photons

it conducts the high voltage from the cathode back into the x-ray generator circuitry

it serves as the primary thermal conductor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens to electrons at the anode target surface?

A

high speed electrons from the filament are suddenly stopped, resulting in the production of x-ray photons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why is a faster rotating anode better to have?

A

the faster it rotates, the better the heat dissipation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the 3 reasons why tungsten is the metal of choice for the source of x-ray photons?

A

high atomic number

high melting point

heat conducting ability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What happens to a rotating anode with time?

A

eventually some of the rotating anode will vaporize sufficient target focal track material to roughen or pit the target area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What can be done to prevent target pitting?

A

properly performing anode warm - up procedure

17
Q

What are the repercussions of failing to follow proper x-ray warm up procedures?

A

It can cause the entire anode to crack if the molybdenum absorbs the heat too rapidly and exceeds its expansion capability

18
Q

What is the target area?

AKA focal point, focal spot, or the focal track

A

the portion of the anode where the high voltage electron steam will impact

19
Q

What is the actual focus spot?

A

the physical area of the focal track that is impacted

20
Q

What is the effective focal spot?

A

the area of the focal spot that is projected out of the tube toward the object being radiographed

21
Q

What is the line focus principle?

A

it is used to reduce the effective area of the focal spot

22
Q

What controls the effective focal spot size?

A

by the size of the actual focal spot and the anode target angle

23
Q

What is the most common diagnostic radiography target angle?

A

12 degrees

24
Q

The effective focal spots vertical dimension is the one that is stated as what?

A

the focal spot size

25
Q

What is the anode heel effect?

A

because of the geometry of an angled anode target, the radiation intensity is greater on the cathode side

26
Q

What is the only part of the cathode or anode assemblies that is located outside of the vacuum of the envelope?

A

the stator

27
Q

What happens if the stator fails?

A

the rotor will cease to turn the anode, which would result in the immediate melting of a spot on the target because anode targets are not designed to absorb the heat of a high voltage exposure while stationary

28
Q

Where is the rotor located?

A

inside the stator and inside the envelope

29
Q

What is the rotor composed of?

A

a hallow copper cylinder of cuff.

30
Q

What is the cuff of the rotor?

A

it is the true rotor that is affected by the electromagnetic field of the stator, causing it to turn

31
Q

What is the envelope?

A

it is the glass casing that all of the anode assembly is in (except the stator)

AKA the tube

32
Q

What is the tube/envelope designed to do with left over unwanted photons?

A

the housing is designed to absorb them

33
Q

What is the maximum amount of leakage radiation allowed from the tube?

A

it must not exceed 100mR/hr at 1 meter

Rad 102: Intro to radiologic technology (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions