XRay Physics 2

Question 1

If an x ray is produced nearer the nucleus, will the resulting xrays be lower or higher energy and frequency?

Answer 1

Higher energy and frequency

Question 2

If the atomic number of a filtration material is lower, what is the effect on the likelihood of the photoelectric effect?

Answer 2

Likelihood of PEE will be increased

Question 3

If the density of a filtration material is higher, what is the effect on the likelihood of the photoelectric effect?

Answer 3

Likelihood of PEE is higher

Question 4

What is the aim of filtration?

Answer 4

Via PEE, to remove useless low energy xrays that don;t reach the detector but would otherwise contribute to patient dose

Question 5

What is the photoelectric effect?

Answer 5

When xrays interact with patient atoms, releasing a photoelectron

Question 6

What is the equation for likelihood of photolectric effect?

Answer 6

T (likelihood of PPE) proportional to pZ3/E3

p = density of material
Z = atomic number of material
E = energy of electron

Question 7

What is inherent filtration and what does it consist of?

Answer 7

Glass envelope, oil, xray window and collimator

Question 8

How many mm of Al equivalent is inherent filtration?

Answer 8

0.5 to 1.5 mm

Question 9

What is added filtration?

Answer 9

Placing an additional aluminiu sheet 10.5 to 1.5 mm thick. Can also be berylium, Gu, Tin.

Question 10

Does maximum energy change with filtration?

Answer 10

No

Question 11

Does photon number increase of decrease with filtration?

Answer 11

Decrease

Question 12

What happens to the average energy of the xray beam with filtration?

Answer 12

Increases

Question 13

What is collimator made of and why?

Answer 13

Lead because it has a high atomic number

Question 14

What happens to the average energy of the xray beam with collimation?

Answer 14

Nothing

Question 15

What are the two benefits of collimation?

Answer 15

1) Reduced scatter off patient so better spatial resolution (less noise, more contrast)
2) Decrease in patient dose

Question 16

What is xray quantity?

Answer 16

Number of photons in xray beam.

Question 17

What is xray quality?

Answer 17

Average energy of the xray beam

Question 18

Are the xrays produced more Bremsstrahlung of more Characteristic?

Answer 18

Bremsstrahlung

Question 19

What determines the energy of the electron striking the tungsten’s focal point?

Answer 19

The tube potential

Question 20

What two things are interacting to make Bremsstrahlung radiation?

Answer 20

Bombarding negative electron being attracted to positive tungsten nucleus

Question 21

What is the process causing Bremsstrahlung radiation?

Answer 21

As electron comes towards nucleus, it slows down and changed direction. Loss of kinetic energy from slowing is released as Bremsstrahlung radiation.

Question 22

If the electron is closer to the nucleus, is Bremsstrahlung radiation increased or decreased? Why?

Answer 22

Increased because more kinetic energy loss

Question 23

If atomic number is lower, is Bremsstrahlung radiation increased or decreased? Why?

Answer 23

Decreased because fewer nuclear protons so less attraction between electron and nucleus.

Question 24

Would maximum photon energy change if different target material with a different atomic number was used?

Answer 24

No. This is determined by kVP alone.

Question 25

As energy increases, does change of PEE increase of decrease?

Answer 25

Decrease

Question 26

What four factors determine number of photons?

Answer 26

1)Current (mAs) 2) kVP 3) target material 4) filtration

Question 27

What two things are interacting to make Characteristic radiation?

Answer 27

Bombarding electron and target's shell electron

Question 28

What is the process causing characteristic radiation?

Answer 28

If kinetic energy of bombarding electron is higher than target shell electron, shell electron is ejected (photoelectron). The bombarding electron is deflected off at an angle. The vacancy in the k shell is filled by electron from higher energy l,m. This loss in energy from dropping down a shell is released as characteristic radiation.

Question 29

What force is determining characteristic radiation and what in turn determines that?

Answer 29

Binding energy between k and l electrons. BE itself is determined by number of protons in nucleus and distance of electrons from nucleus.

Question 30

Are the ka/kb peaks in characteristic radiation dependent or independent on energy of bombarding electron?

Answer 30

Independent

Question 31

Is Bremstallung radiation independent or dependent on energy of bombarding electron?

Answer 31

Dependent, as kVP increases, bombarding electron energy increases and Brem radiation increases.

Question 32

What happens to characteristic <10 KeV?

Answer 32

Inherent filtration filters them out.

Question 33

If filament current is decreased, will this increase or decrease quality or quantity? What is the mechanism?

Answer 33

Decrease quantity. Reduced current means lower filament heat means fewer electrons available at filament surface for thermionic emission.

Question 34

Do characteristic peaks increase or decrease if filament current is increased? Why?

Answer 34

Neither, changing filament current has no effect on characteristic peaks because dependent on material, not current.

Question 35

What is tube potential?

Answer 35

This is what accelerates electrons from the cathode to the anode

Question 36

Does increasing tube potential increase or decrease electron energy or electron number? Why?

Answer 36

Increases both electron energy and electron number (bc at set filament current, more tube potential --> more tube current and more electrons pulled away).

Question 37

Does maximum photon energy change with increased tube potential? Why?

Answer 37

Yes because maximum photon energy corresponds with maximum tube potential.

Question 38

What happens to Bremsstrahlung radiation as tube potential is increased?

Answer 38

More Brem radiation because bombarding electrons loose all their kinetic energy

Question 39

Does filament current affect quality? Does it affect quantity?

Answer 39

Affects quantity but not quality

Question 40

Does adding filtration change quality?

Answer 40

Filtration increases quality because low energy electrons are removed

Question 41

Does adding filtration change quantity?

Answer 41

Filtration decreases quantity because the lower energy electrons are removed reducing the overall number of electrons

Question 42

Does added filtration change the characteristic peaks?

Answer 42

No as long as the same material is being used

Question 43

Is Bremstrallung radiation directly or indirectly proportional to atomic or mass number?

Answer 43

Directly proportional to atomic number

Question 44

What is kV ripple?

Answer 44

The difference between kVP and baseline

Question 45

If you use a high frequency inverter to keep waveform at kVP, what is the kV ripple?

Answer 45

4%

Question 46

What is the kV ripple of single pulse 1 phase waveform?

Answer 46

100%

Question 47

If you reduce kV ripple, what does this do to quantity and quality?

Answer 47

Increases both quality and quantity

Question 48

If you increase kV ripple, does this increase kVP?

Answer 48

No change in kVP as max kVP always reached

Question 49

Does kVp change quality or quantity?

Answer 49

Quality and quantity

Question 50

In this analogy, is kVp or mA the amount of water flowing or water pressure?

Answer 50

kVp = water pressure mA = how much water is flowing Higher pressure = more forceful spray. More flow = more water volume.

Question 51

Does mA affect quality or quantity?

Answer 51

Quantity only