week 6 Xray physics up too chapter 10

Question 1

higher energy photons are produced by increasing what?

Answer 1

KVp

Question 2

as you increase filtration what is affected?

‘beam hardening’

Answer 2

decreases the xray energy keV by absorbing the lower energy photons

Question 3

inherent filtration

Answer 3

is built into the machine to remove the low energy photons

Question 4

added filtration is done when you need?

Answer 4

to balance the intensity of x-ray exposure over an area of anatomy that is not uniform in density and/or thickness

Question 5

what portion of the wedge is over the thin part of the thoracic spine?

Answer 5

the thick part

Question 6

collimator is set to go straight through?

Answer 6

the dense part of the anatomy of the pt.

Question 7

Penetrability =

Answer 7

ability of x-ray beam to penetrate

Question 8

Attenuation =.

Answer 8

reduction of beam intensity due to absorption and scattering

of photons not quality

Question 9

Half-value layer (HVL) =

Answer 9

that thickness of absorbing material that will cause the exiting beam intensity to be one-half of the entering (ie, incident) beam intensity

Question 10

uniform attenuation is not seen in what kind of imaging?

Answer 10

diagnostic xray beam

Question 11

For a beam NOT composed of monoenergetic photons, what actually happens to the half-value layer as the beam passes thru matter?

Answer 11

becomes thicker as the beam passes through matter

Question 12

what do you think a tenth-value layer would be?

Answer 12

reduce it too a 10th of that value

Question 13

Five basic interactions may occur betweeen matter and xray

Answer 13

Coherent scattering
Photoelectric interaction
Compton interaction
Pair production
Photodisintigration

Question 14

photons of electromagnetic radiation tend to interact with structures similar in size to their ________?

Answer 14

wavelength

Question 15

Low energy photons (longer wavelength) tend to interact with

Answer 15

atoms

Question 16

Moderate energy photons tend to interact with

Answer 16

electrons

Question 17

Higher energy photons tend to interact with

Answer 17

nuclei

Question 18

“classical scattering” or “Thompson scattering”

occurs at what energy levels?

Answer 18

photon energy levels below 10keV

Question 19

coherent scattering affects what amount of xray photons?

Answer 19

small amount

Question 20

during coherent scattering the xray energy is ______ and ________ from the atom

Answer 20

1. absorbed

2. re-emitted

Question 21

pair production?

Answer 21

Photon disappears and 2 oppositely charged pieces of matter (one electron and one positron) are formed

Question 22

what is the Photodisintigration energy level

& this is between what two structures?

Answer 22

(>10MeV) photon and nucleus

Question 23

pair production energy level between what two structures?

Answer 23

Interaction of high energy (>1.02MeV) photon and electromagnetic field of nucleus

Question 24

in photodisintigration what happens to the photon?

Answer 24

Photon disappears a nuclear fragment is emitted

Question 25

Photoelectric interaction?

Answer 25

Interaction of lower energy photons in the diagnostic x-ray beam

Question 26

does ionization occur during Photoelectric interaction?

Answer 26

yes, the photoelectron is ejected

Question 27

Photoelectric interaction involves electron from where atomic orbit?

Answer 27

inner shell

Question 28

what absorbs the energy of the xray?

Answer 28

inner shell electron due to

Question 29

KE + BE is equal to what?

Answer 29

the energy of the xray

Question 30

the photon that is produced in the photoelectric interaction?

Answer 30

secondary xray photon produced by xray not inside the tube (tungsten)

Question 31

is all of the energy absorbed in photoelectric interaction?

Answer 31

yes

Question 32

probability of photoelectric interaction is dependent on?

Answer 32

energy of the xray and the atomic number of the atom involved

Question 33

relationship of the xray energy and PE event?

Answer 33

inversely proportional to the 3rd power of the xray energy

Question 34

atomic number and PE relationship?

Answer 34

directly proportionally to the 3rd power of the atomic number (z#)

Question 35

compton interaction involves?

Answer 35

photons within the diagnostic spectrum that have intermediate to high energy

Question 36

in compton interaction the incident photon interacts with the

Answer 36

outer shell e-

Question 37

does ionization occur in compton?

Answer 37

yes

Question 38

what is the characteristic of incident photon in comptone?

Answer 38

scattered

Question 39

scattered photon means?

Answer 39

redirected from their original vecter and contains 2/3 or more of the incident photon NRG;

Question 40

with minimal direction change of a e- what happens to the energy loss

Answer 40

it will be minimally loss

Question 41

are scattered photons useful in image production?

Answer 41

no

Question 42

what is the caution of scattered photons?

Answer 42

potential to have othoer ionizing events to go on so they are hazardous

Question 43

Atomic number of the involved atom _____ affect Compton interaction probability

Answer 43

does not

Question 44

as compton interactions decrease what happens to the photon energy?

Answer 44

it will increase

Question 45

why are compton interactions more predominant when the average beam energy increases?

Answer 45

because photoelectric energy decreases more in xray energy; in turn increasing chance of compton interaction

Question 46

how do you control photon energies?

Answer 46

with kVp

Question 47

at about 80 kVp what is happening in regards to compton vs photoelectric?

Answer 47

about equal to eachother

Question 48

which one predominates at higher kVp in comparison to compton and photoelectric?

Answer 48

comptom

Question 49

differential absorption defintion?

Answer 49

difference in the absorbing ability between 2 different materials

Question 50

what influences the differential absorption (photoelectric interactions)?

Answer 50

the atomic energy

Question 51

as you from fat > soft tissue > lung > bone what happens to the atomic number?

Answer 51

it increases | * little difference between fat and other soft tissue

Question 52

how can you use contrast materials?

Answer 52

use the ones with greater atomic number to give an outline.

Question 53

what is the difference between compton interaction and photoelectric interactions in reagards to diagnostic imaging?

Answer 53

compton: does not contribute Photoelectric: does contribute

Question 54

photoelectric interactions effect attenuation in what way?

Answer 54

they play a big role in it by decresing the number of photons as it goes through tissues

Question 55

how does scatter e- effect the attenuation?

Answer 55

decreases the # of photons in the beam with some backscatter

Question 56

mass density?

Answer 56

how many atoms are present per unit volume of material