Characteristics of X-rays

Question 1

two mechanisms of x-ray production

Answer 1

• bremsstrahlung

- characteristic radiation

Question 2

what is bremsstrahlung x-ray production?

Answer 2

electron to nucleus interaction

Question 3

what is characteristic radiation?

Answer 3

electron to electron radiation

Question 4

bremsstrahlung: x-rays produced when ______ are suddenly _____ when they pass close to the nuclei of a ________

Answer 4

high velocity e-, decelerated, high Z# absorbing material

Question 5

3 requirements of Bremsstrahlung radiation

Answer 5

electrons, high velocity to electrons, high Z# absorbing material

Question 6

bremsstrahlung has _____ and ___ interactions

Answer 6

direct hit, near-miss

Question 7

because not all e- attain the same ___, some move at different ___ than others, ultimately producing _________, or__________

Answer 7

velocity, velocities, radiation of different energies, polychromatic x-ray beam

Question 8

what percentage of diagnostic beam is bremsstrahlung?

Answer 8

70%

Question 9

in near-miss bremsstrahlung interactions: the closer the e-, the ________ of the bremsstrahlung photon

Answer 9

closer the electron

Question 10

characteristic radiation: a number of e- with inner orbital electrons of W, overcome the ______, and cause _____

Answer 10

binding energies, ionization

Question 11

result of characteristic radiation is a polychromatic x-ray beam but __________ than bremsstrahlung

Answer 11

much narrower energy spectrum

Question 12

the energy of characteristic radiation is specific to ________

Answer 12

the Z of the producing material

Question 13

what percentage of diagnostic x-ray beam is characteristic?

Answer 13

30%

Question 14

incident electron knocks ______ (____); incident electron may continue as a ______

Answer 14

inner electron out (recoil electron), photoelectron

Question 15

are x-rays electrons?

Answer 15

no

Question 16

electrons are….

Answer 16

• particulate radiation
• have mass
• and have variable velocity

Question 17

x-rays are…

Answer 17

-electromagnetic radiation (no mass, fixed velocity)

Question 18

radiation that originates at focal spot, leaves the tube through window, is useful in image formation

Answer 18

primary (usable) beam

Question 19

radiation that originates at focal spot, leaves the tube through barriers around the tube

Answer 19

leakage radiation

Question 20

radiation that originates in tissues, causes image noise

Answer 20

secondary/scatter radiation

Question 21

what is used to minimize leakage radiation?

Answer 21

glass, oil, and metal enclosures

Question 22

change in kVp changes ________

Answer 22

potential difference between cathode and anode

Question 23

increase kVp does what to the number of photons generated (quantity)?

Answer 23

increases quantity

Question 24

increase kVp does what to the mean energy of the photons (beam quality)?

Answer 24

increases quality

Question 25

increase kVp does what to maximal energy of photons (beam quality)?

Answer 25

increases quality

Question 26

increase kVp does what to radiographic contrast?

Answer 26

decreases contrast

Question 27

For constant receptor exposure, exposure time and kVp are ________

Answer 27

inversely related

Question 28

when kVp is increased, ____ should be decreased

Answer 28

exposure time

Question 29

most times, we "set and forget" _____ while we change ____

Answer 29

kVp and mA; exposure time

Question 30

increase mA, what happens to amount of power applied to filament?

Answer 30

increased

Question 31

increase mA, what happens to x-ray beam quality?

Answer 31

increasing mA does nothing to beam quality

Question 32

what happens to receptor exposure when we increase mA?

Answer 32

increase exposure

Question 33

exposure time does not influence ______

Answer 33

energy of the photons

Question 34

mAs is a product of ______(__) and _______(_)

Answer 34

tube current (mA), exposure time (s)

Question 35

what is the control of size/shape of x-ray beam?

Answer 35

collimation

Question 36

increased collimation leads to...

Answer 36

smaller beam, decreased receptor exposure

Question 37

- circular, diameter at end of cone = ____ | - rectangular end of cone = ____

Answer 37

``` circular = 2.76" rectangular = 2.0" ```

Question 38

a rectangular collimation reduced ______

Answer 38

patient exposure/dose substantially

Question 39

purpose of filtration

Answer 39

preferentially remove long wavelength photons

Question 40

lower kVp results in _______, but the longest wavelength are not useful in _______; they increase patient dose/radiation hazards and _____

Answer 40

higher radiographic contrast, image formation; must be removed

Question 41

_____ + ______ = total filtration

Answer 41

inherent + added

Question 42

examples of inherent filtration

Answer 42

widow of x-ray tube, insulating/cooling oil, oil seal

Question 43

examples of added filtration

Answer 43

aluminum discs (1/2mm or 1mm)

Question 44

beam produced at or below 70kVp = ___mm Al equivalent

Answer 44

1.5mm

Question 45

beam produced at 90 kVp = ___mm Al equivalent

Answer 45

2.5mm

Question 46

if filtration increase, mAs should be ____ to ________

Answer 46

increased, maintain similar receptor exposure

Question 47

the thickness of a material which, when placed in the path of an x-ray beam, will reduce quantity of radiation by 50%

Answer 47

half value layer (HVL)

Question 48

HVL is an indicator of x-ray beam _____

Answer 48

quality (penetrability)

Question 49

a beam with higher mean energy (higher penetrability) has a _____

Answer 49

thicker HVL

Question 50

you need to increase HVL with...

Answer 50

increased kVp, increased filtration

Question 51

for constant receptor exposure, exposure time should be ____ when SID (source to object distance) increases

Answer 51

increased

Question 52

based on inverse square law, exposure time is ______ to the square of SID

Answer 52

directly proportional

Question 53

with inverse square law, if you double the distance, intensity becomes ____ the original

Answer 53

1/4

Question 54

with inverse square law, if you half the distance, intensity becomes ____ the original

Answer 54

4x

Question 55

attenuation in which photon ionizes absorber (tissue) atoms, convert their energy to ejected e-, and then cease to exist

Answer 55

absorption attenuation

Question 56

attenuation in which photons interact with absorber (tissue) atoms, but is deflected in another direction

Answer 56

scattering attenuation

Question 57

3 types of beam attenuation

Answer 57

- coherent scattering - photoelectronic absorption - Compton scattering

Question 58

how many photons undergo coherent scatterin?

Answer 58

7%

Question 59

how many photons undergo photoelectronic absoprtion?

Answer 59

27%

Question 60

how many photons undergo Compton scattering?

Answer 60

57%

Question 61

did you look at the 3 types of beam attenuation photos on the powerpoint?

Answer 61

I hope you did, they sure help!

Question 62

coherent scattering process

Answer 62

1. low energy incident photon interacts with whole photon 2. atom momentarily excited; photon momentarily disappears 3. excited atom returns to ground state; release photon 4. photon absorbed by tissue

Question 63

coherent scattering has a (contribution/no contribution) to image noise

Answer 63

no contribution

Question 64

______ and _____ cause secondary and tertiary ionizations

Answer 64

photoelectric absorption and Compton's scattering

Question 65

photoelectric radiation process

Answer 65

1. Incident x‐ray photon interacts with an inner orbital electron 2. Inner electron is ejected; called photoelectron or recoil electron (atom is ionized) 3. higher orbital e- falls to fill vacancy 4. this "fall" emits electromagnetic energy

Question 66

Compton's scattering process

Answer 66

1. Incident photon interacts with an outer orbital e- 2. Overcomes binding energy, ejects e- (ionization) 3. Ejected e- (called Compton’s electron) acquires part of the energy 4. Remainder of energy given off as scattered, weaker energy photon