Basic Physics

Question 1

X-rays are produced when energetic electrons interact with nuclear electric fields

Answer 1

Bremsstrahlung

Question 2

Produced when target K-shell electrons are ejected by the indicednt energetic electrons

Answer 2

Characteristic x-ray

Question 3

Three possible fates of x-ray incident on matter

Answer 3

Scattering
Absorption
Penetration

Question 4

Occurs when a low-energy x-ray photon is scattered from an atom without any energy loss

Answer 4

Coherent scatter

Question 5

X-rays are primarily scattered via

Answer 5

Compton scatter

Question 6

Occurs between tightly bound (inner shell) electrons and incident x-ray photons

Answer 6

Photoelectric effect

Question 7

Incident photons interact with outer shell electrons

Answer 7

Compton scatter

Question 8

fraction of incident photon removedf from the beam in traveling unit distance

Answer 8

Linear attenuation coefficient

Question 9

Acounts for all x-ray interactions

Answer 9

Attenuation coefficient

Question 10

Binding energy of the K-shell electrons in iodine

Answer 10

33 keV

Question 11

Used to quantify the x-ray beam intensity

Answer 11

Air kerma

Question 12

the thickness of material that attenuates an x-ray beam by 50%

Answer 12

Half-value layer

Question 13

HLV of soft tissue ~1

Answer 13

Mammography

Question 14

HLV for soft tissue is ~3 cm

Answer 14

Abdomninal radiography

Question 15

Factors tha influence BOTH X-ray quantity and Quality

Answer 15

Tube voltave (kV)
Filtration

Question 16

DOminant source of scatter

Answer 16

Compton interactions

Question 17

Minor contributor to total scatter (<5%)

Answer 17

Coherent scatter

Question 18

Does scatter affect spatial resolution or mottle?

Answer 18

No

Question 19

scatter increases markedly with increasing?

Answer 19

Field size

Question 20

Reduces total patient mass irradiated and reduces scatter

Answer 20

Collimation

Question 21

Scatter removal (grids) are essential when patient thickness exceeds _cm.

Answer 21

12 cm.

Question 22

Use of low tube voltages in x-ray imaging results in what interactions?

Answer 22

Photoelectric

Question 23

Increasing tube voltage results in what interactions?

Answer 23

Compton

Question 24

Percentage of (useful) primary radiation that passes through the grid

Answer 24

Primary transmission

Question 25

Grids are expected to transpit about _% of (useful) primary x rays and absorb the remaining _%

Answer 25

70% 30%

Question 26

Grids are expected to absorb _%of (useless) scatterd protons and transmit the remaining _10%

Answer 26

90% 10%

Question 27

Ratio of radiation incident on the grid to the transmitted radiation

Answer 27

Bucky favctor

Question 28

Artifacts caused by improper alignment, wrong focal spot to film distance for focused grids and inverted grids

Answer 28

Grid cutoff

Question 29

Occers when there is air gap between the patient and corresponding image receptor

Answer 29

Geometric magnification

Question 30

Scattered photons are less likely to reach the image receptor when there is an?

Answer 30

air gap

Question 31

Major drawback of magnification imaging

Answer 31

Increased focal spot blurring

Question 32

Material that emit light when exposed to radiation

Answer 32

Scintillators (phosphors)

Question 33

used scintillators coupled to a two-dimensional array of light detectors

Answer 33

Flat panel detectors

Question 34

Image intensifier input phosphors are scintillators, generally made of

Answer 34

Cesium iodide (CsI)

Question 35

absorb x-ray which are converted into charge

Answer 35

Photoconductors

Question 36

Widely used in mammography (excellent absorber)

Answer 36

Selenium

Question 37

Most common photoconductor in use in digital radiography

Answer 37

Selenium

Question 38

first digital detectors to replace screen-film, historically known as computed radiography

Answer 38

Photostimulable phosphors