X-Ray Tubes/Production

Question 1

Characteristics of a Cathode:

Answer 1

1. Filaments
2. have a (-) charge
3. Step down Transfer
4. Thermionic Emission (boiling of of electrons)

Question 2

Characteristics of an Anode:

Answer 2

1. Its the Target
2. (+) charge
3. HIGH Z = MORE bremmstrahlung
4. determines Characteristic X-Ray Spectrum

Question 3

Characteristics of Accelerating Potential:

Answer 3

1. QUANTITY increases with kVp^2
2. QUALITY increases with kVp (less low E, more forward directed)
3. Wave Forms: Single Phase, 3 Phase, Constant Potential

Question 4

Characteristics of Tube Current (mA):

Answer 4

1. # of electrons flowing between Cathode and Anode

2. as Tube Current increases, Quantity increases

Question 5

Characteristics of Filtration (for x-ray tubes)

Answer 5

1. increased Filtration increases Quality (beam hardening)

2. Compound Filters: Thoraueus Filter, Sources (Sn,Cu,Al,patient)

Question 6

What part of the x-ray tube uses a focusing cup (grid) to direct the flow of electrons?

Answer 6

Cathode - directs the flow of e’ to the Anode

Question 7

Describe the Line Focus Principle:

Answer 7

1. 99% of E is transferred to heat, 1% to formation of diagnostic x-rays (60/40 for therapeutic x-rays)
2. the target angle is between 6-20 degrees
3. smaller angle = smaller focal spot

Question 8

What material does the Anode use and why?

Answer 8

Tungsten, it has a high melting point

Question 9

What is the equation used to find the efficiency of producing x-rays?

Answer 9

Efficiency = 1.3 x 10^-9 x Z

Question 10

What material is used to help with beam hardening

Answer 10

10% rhenium

Question 11

At what rate does the Anode spin for x-ray production?

Answer 11

3600 rpm

Question 12

Describe Heel effect - when is it possible?

Answer 12

Heel effect is when the intensity on the Anode side is < the intensity on the Cathode side.
It is less noticeable for large focus-film distances and for smaller targets.
It only occurs in kV x-ray production due to the angled Anode (MV x-ray production the Anode is not angled)

Question 13

Characteristics of Diagnostic X-Ray PRODUCTION:

Answer 13

1. Primarily Bremsstrahlung
2. < 150 keV, characteristic represents 20%
3. > 150 keV, characteristic is «< 1%

Question 14

How is Diagnostic X-Ray INTENSITY related to kVp and mAs:

Answer 14

1. Proportional to KVp^2

2. Proportional to mAs

Question 15

Characteristics of Focal Spot:

Answer 15

1. Smaller FS gives better resolution (more detail)
2. as kVp increases, FS decreases (better resolution)
3. as mA increases, FS increases (less resolution)