RADPRO MODUE 7 and 8

Question 1

The x-ray beam is characterized by

Answer 1

quantity and quality

Question 2

The intensity of the x-ray beam of an x-ray imaging system is measured in

Answer 2

milligray in air/mGya
miliroentgen
qunaitiy

Question 3

Another term for x-ray intensity

Answer 3

radiation exposure

Question 4

is a measure of the number of ion pairs produced in air by a quantity of x-rays.

Answer 4

mGya (mR)

Question 5

Ionization of __ increases as the number of x-rays in the beam increases.

Answer 5

air

Question 6

Most general-purpose radiographic tubes, when operated at approximately ___-

Answer 6

70 kvp

Question 7

effect of mas in quantity

Answer 7

increased

Question 8

effect of kvp to qunatitiy

Answer 8

The change in x-ray quantity is proportional to the square of the ratio of the kVp;

Question 9

note

Answer 9

that by increasing kVp and reducing mAs so that image receptor exposure remains constant, the patient dose is reduced significantly.

Question 10

note

Answer 10

There is no change in contrast when using digital image receptors.

Question 11

relationship between quantity and distance

Answer 11

X-ray intensity varies inversely with the square of the distance from the x-ray tube target. This relationship is known as the inverse square law.

Question 12

note

Answer 12

When SID is increased, mAs must be increased by SID² to maintain constant exposure to the image receptor.

Question 13

The purpose of these is to reduce the number of low-energy x-rays.

Answer 13

filtration

Question 14

Disadvantage of x-ray beam filtration:

Answer 14

Reduced image contrast when using screen film caused by x-ray beam hardening. X-ray beam hardening increases the number of high energy x-rays in the beam by removing the lower-energy non-penetrating x-rays.

Question 15

As the energy of an x-ray beam is increased, the penetrability is

Answer 15

increased

Question 16

one description of the ability of an x-ray beam to pass through tissue.

Answer 16

Penetrability

Question 17

___ and ___do not affect radiation quality; they do affect radiation quantity.

Answer 17

mas and distance

Question 18

note

Answer 18

Factors that affect x-ray beam quality also influence radiographic contrast when screen film is the image receptor.

Question 19

Whereas 100-keV x-rays are attenuated at the rate of approximately

Answer 19

3%/cm of soft tissue

Question 20

10-keV x-rays are attenuated at approximately

Answer 20

15%/cm of soft tissue

Question 21

In radiography, the quality of x-rays is measured by

Answer 21

HVL

Question 22

In radiography, the quality of x-rays is measured by

Answer 22

3 to 5 mm Al or 3 to 6 cm of soft tissue.

Question 23

NOTE

Answer 23

To improve image contrast, it is also desirable to remove x-rays with energies above a certain level. Unfortunately, such removal of regions of an x-ray beam is not normally possible.

Question 24

NOTE

Answer 24

As filtration is increased, so is beam quality, but quantity is decreased

Question 25

the glass or metal enclosure of an x-ray tube filters the emitted x-ray beam

Answer 25

INHERETN FILTER

Question 26

The inherent filtration of a general purpose x-ray tube is approximately

Answer 26

0.5 mm Al equivalent.

Question 27

thin sheet of Al positioned between the protective x-ray tube housing and the x-ray beam collimator is the usual form of added filtration.

Answer 27

ADDED FILTRATION

Question 28

2 Sources of Added Filtration:

Answer 28

1.1-mm or more sheets of Al Collimator contributes an additional 1 mm Al

Question 29

compensates for differences in subject radiopacity.

Answer 29

compensating filters

Question 30

X-ray interact with matter in the following five ways

Answer 30

coherent scattering, (2) Compton scattering, (3) photoelectric effect, (4) pair production, and (5) photodisintegration.

Question 31

on __ and __ are important in making an x-ray image.

Answer 31

compton and pohotelectric

Question 32

low-energy x-rays tend to interact with whole atoms, which have diameters of approximately

Answer 32

10−9 to 10−10 m

Question 33

moderate energy x-rays generally interact

Answer 33

electron

Question 34

high-energy x-rays generally interact with

Answer 34

nuclei

Question 35

low-energy x-rays tend to interact with

Answer 35

whole atoms

Question 36

X-rays with energies below approximately __keV interact with matter by coherent scattering,

Answer 36

10

Question 37

the incident x-ray interacts with a target atom, causing it to become excited

Answer 37

Coherent Scattering

Question 38

measurement of wavelength in coherent scattering

Answer 38

equal to that of the incident x-ray (λ = λ′) and therefore of equal energy

Question 39

Note

Answer 39

in cohenrent direction of the scattered x-ray is different from that of the incident x-ray.

Question 40

There is no energy transfer and therefore no ionization.

Answer 40

Coherent Scattering

Question 41

Most coherently scattered x-rays are scattered in the

Answer 41

forward direction

Question 42

X-rays throughout the diagnostic range can undergo an interaction with outer-shell electrons

Answer 42

Compton Scattering

Question 43

the ejected electron in compton scattering is called

Answer 43

compton electron

Question 44

what happen to the x-ray ejected in compton

Answer 44

The x-ray continues in a different direction with less energy

Question 45

X-rays in the diagnostic range also undergo ionizing interactions with inner-shell electrons.

Answer 45

Photoelectric Effect

Question 46

The x-ray is not scattered, but it is totally absorbed

Answer 46

Photoelectric Effect

Question 47

photoelectric effect and earned Albert Einstein the __ Nobel Prize in physics in

Answer 47

1921

Question 48

kinetic energy equal to the difference between the energy of the incident x-ray and the binding energy of the electron.

Answer 48

Photoelectric Effect

Question 49

NOTE

Answer 49

For higher atomic number target atoms, electron binding energies are higher (37 keV for barium K-shell electrons). Therefore, the kinetic energy of the photoelectron from barium is proportionately lower.

Question 50

NOTE

Answer 50

For low atomic number atoms, such as those found in soft tissue, the binding energy of even K-shell electrons is low (e.g., 0.3 keV for carbon). Therefore, the photoelectron is released with kinetic energy nearly equal to the energy of the incident x-ray.

Question 51

RELATIONSUIP OF PHOTOEELCTRIC EFFECT TO ENERGY

Answer 51

The probability of the photoelectric effect is inversely proportional to the third power of the x-ray energy (1/E)³

Question 52

The interaction between the x-ray and the nuclear field causes the x-ray to disappear, and in its place, two electrons appear, one positively charged (positron) and one negatively charged.

Answer 52

Pair Production

Question 53

The positron unites with a free electron, and the mass of both particles is converted to energy in a process called

Answer 53

annihilation radiation.

Question 54

pair production involves only x-rays with energies greater than

Answer 54

1.02 MEV

Question 55

X-rays with energy above approximately ___ can escape interaction with electrons and the nuclear field and be absorbed directly by the nucleus.

Answer 55

10 MeV

Question 56

the nucleus is raised to an excited state and instantly emits a nucleon or other nuclear fragment.

Answer 56

photodisintegration

Question 57

contributes no useful information

Answer 57

Compton-scattered x-rays

Question 58

provide diagnostic information. (radiopaque)

Answer 58

Photoelectric x-rays

Question 59

produce dark areas in the radiograph. (radiolucent)

Answer 59

Transmitted x-rays

Question 60

The total reduction in the number of x-rays remaining in an x-ray beam after penetration through a given thickness of tissue is called

Answer 60

attenuation.

Question 61

the product of absorption and scattering.

Answer 61

attenuation.

Question 62

an all-or none condition for x-ray interaction.

Answer 62

Absorption

Question 63

An interaction such as the photoelectric effect is called an

Answer 63

Absorption process