chapter 3 EXAM 2

Question 1

milliampere seconds mAs

Answer 1

quantity
product of exposure time and tube current
a measure of the total number of electrons that travel from the cathode to the anode

Question 2

peak kilovoltage kVp

Answer 2

quality

controls the quality or penetrating power of the photons in xray beam

Question 3

when radiation interacts with matter (the body) some photons are….

Answer 3

some photons are absorbed

some are scattered and some pass through without interacting at all

Question 4

absorption

Answer 4

transference of electromagnetic energy from an xray beam to the atoms or molecules of the matter through which it passes

Question 5

scatter

Answer 5

a change in direction of travel of an xray photon that may also involve a potential loss of radiation energy

Question 6

absorption + scatter =

Answer 6

attenuation

Question 7

direct transmission

Answer 7

when photons pass through the patient without interacting and reach the IR

Question 8

primary radiation

Answer 8

emerging xray photon beam

Question 9

indirect transmission

Answer 9

primary photons that undergo compton and or coherent interactions and are scattered or deflected after they go through an object

Question 10

an optimal xray image is formed only when

Answer 10

direct transmission xrays reach the IR

Question 11

a radiographic image is formed from

Answer 11

directly transmitted photons and indirectly transmitted (scattered) photons

Question 12

attenuation

Answer 12

refers to any process decreasing the intensity of the primary photon beam

Question 13

radiographic fog

Answer 13

undesirable additional density on a radiographic image caused by scatter reaching the IR

Question 14

true or false

photon interaction is random

Answer 14

true

Question 15

an xray image results from the difference between

Answer 15

the xrays absorbed photoelectrically by the patient and those transmitted to the IR

Question 16

differential absorption

Answer 16

different degrees of absorption in different tissues that result in image contrast and formation of the image

Question 17

what are the 4 factors that influence probability of interactions of photons

Answer 17

1. photon energy
2. atomic number
3. mass density
4. tissue thickness

Question 18

as photon energy increases,

Answer 18

kvp increases and absorption is reduced

Question 19

as atomic number increases,

Answer 19

it increases the chances that the xray photon will be absorbed to the 3rd power

Question 20

as xray energy increases

Answer 20

fewer compton interactions
fewer photoelectric interactions
more passing through without interacting

Question 21

as tissue atomic number increases

Answer 21

no change in compton interactions
more photoelectric interactions
less passing through without interacting

Question 22

as tissue mass density increases

Answer 22

proportional increasie in compton interactions
proportional increase in photoelectric interactions
proportional reduction in passing through without interacting

Question 23

5 types of interaction between x radiation and matter

Answer 23

1. coherent scattering
2. compton scattering
3. photoelectric absorption
4. pair production
5. photodisintegration

Question 24

coherent scattering is also called

Answer 24

classic, elastic or unmodified scattering

Question 25

coherent scattering

Answer 25

involves low energy photons below 10 KeV when the low energy photon interacts with tissue, it does not loose energy. It just changes direction and becomes excited. no ionization occurs here.

Question 26

photoelectric absorption is the most important

Answer 26

mode of interaction between xray photons and the atoms of the pts. body for producing useful images

Question 27

photoelectric absorption

Answer 27

interaction between the dray photon and an inner shell electron (k shell)

Question 28

to dislodge an inner shell electron from its orbit, the xray photon must

Answer 28

be able to transfer a quantity of energy equal to or greater than the electron binding energy

Question 29

on interacting with the inner shell electron, the xray photon surrenders

Answer 29

all of its energy to the orbital electron and ceases to exist it gets absorbed

Question 30

the ejected electron is called a

Answer 30

photoelectron

Question 31

auger effect

Answer 31

process that can occur as a result of photoelectric interactions occurs when an inner shell electron is removed from an atom causing an inner shell vacancy

Question 32

what are the byproducts of photoelectric absorption

Answer 32

photoelectrons | characteristic xray photons

Question 33

probability of occurrence of photoelectric absorption depends on

Answer 33

the energy of the xray photons and the atominc number of the atoms it interacts with

Question 34

photoelectric absorption increases to the 3rd power dramatically as the

Answer 34

energy of the incident photon decreases.

Question 35

the probability of photoelectric absorption increases dramatically when

Answer 35

the atomic number of the atoms increases

Question 36

when mass density is doubled, the chance for xray interaction is doubled because

Answer 36

twice as many electrons are available for interaction

Question 37

the interaction of xrays with tissues is proportional to the

Answer 37

mass density of the tissue

Question 38

T or F if 2 structures have the same mass density and atomic number, but one is twice as thick, the thicker structure will absorb twice as many photons

Answer 38

True

Question 39

T or F | the less a given structure attenuates xrays, the darker its radiographic appearance

Answer 39

true

Question 40

the greater the difference in the amount of photoelectric absorption, the greater the

Answer 40

contrast will be between adjacent structures of differing atomic numbers.

Question 41

as absorption increases, so does

Answer 41

the patient dose :(

Question 42

compton scattering is also called

Answer 42

incoherent scattering inelastic scattering modified scattering

Question 43

what is compton scattering

Answer 43

the interaction of xrays with matter that is responsible for most of the scattered radiation produced during radiologic procedures

Question 44

process of compton scattering

Answer 44

incoming photon interacts with loosely bound outer shell electron. it surrenders part of its energy to dislodge the electron ionizing the atom

Question 45

the ejected electron in compton scattering is called

Answer 45

compton scattered electron secondary electron recoil electron

Question 46

what can happen to the compton scattered photon

Answer 46

it can interact with other atoms it may emerge from the pt. and reach the IR causing fog it could emerge from the pt. and expose personnel

Question 47

compton scattering is the source of

Answer 47

most of the occupational radiation exposure that radiographers receive

Question 48

the probability of the compton scattering effect does not depend on

Answer 48

the atomic number of the atom | doesn't matter what it hits. it will effect an atom of soft tissue the same way as an atom of bone

Question 49

compton scattering provides no useful info on the radiograph. it results in

Answer 49

reduced image contrast

Question 50

Pair production does not occur unless

Answer 50

energy of the incoming xray photon is at least 1.022 mega electron volts this is far above the energy used in diagnostic radiology

Question 51

pair production process

Answer 51

incoming photon interacts with the nucleus of an atom of biologic tissue and disappears in the process energy of the photon is transformed into 2 new particles

Question 52

what are the 2 new particles the photon is transformed into in pair production

Answer 52

negatron (ordinary electron) | positron (positively charged electron)

Question 53

annihilation event

Answer 53

the positron and the electron it interacted with are destroyed and their energy is converted into 2 xray photons that radiate out of the atom

Question 54

photodisintegration

Answer 54

energy above 10 Megaelectron volts | energy too high for diagnostic radiation

Question 55

process of photodisintegration

Answer 55

high energy photon collides with the nucleus of an atom and the nucleus emits a neutron this makes the nucleus radioactive