Physics of Diagnostic Imaging 1 & 2

Question 1

Amount of energy is inversely proportional to _________

Answer 1

wavelength

Question 2

T/F: Longer wavelength = higher energy

Answer 2

FALSE!

Longer wavelength = LESS energy

Question 3

The basic unit of energy in electromagnetic radiation

Answer 3

eV (electron volt)

Question 4

EM radiation > ____ eV

can ionize living cells

Answer 4

15 eV

Question 5

The _________ potential is what makes xrays dangerous

Answer 5

ionization potential

Question 6

An electron ejected from the shell of an atom

Answer 6

ION

Question 7

T/F: Ionization of DNA (caused by xrays) can increase

the risk of cataracts

Answer 7

TRUE

Question 8

What is a roentgen?

Answer 8

A unit of exposure to radiation

Question 9

What is a Rad/Gray?

Answer 9

A unit of absorbed dose of radiation

Question 10

What is a Rem/Sievert?

Answer 10

A unit of dose equivalent

1 Rem = 1,000 mRem

Question 11

The typical person is exposed to _______ mRem/year

Answer 11

360 mRem/year

(1 mRem/day)

Question 12

1 chest x-ray is equivalent to a dose of ____ mRem

Answer 12

10 mRem

Question 13

T/F: There is an increased risk of radiation exposure when flying in an airplane

Answer 13

TRUE!

About 2.5 mRem dose for a 1-way flight across the US

Question 14

T/F: Lead protective gear is great for protection against all types of radiation

Answer 14

FALSE!

Lead protective gear ONLY protects from SCATTER RADIATION

not the primary beam!

Question 15

A voltage potential (Vp) is

electrically _________ at the Anode, and

electrically _________ at the Cathode

Answer 15

POSITIVE at the Anode (target)

and

NEGATIVE at the Cathode (filament)

Question 16

Milliamperes (mA) is the unit of measure for

Answer 16

Electric current

Question 17

The more electric current passed through the cathode (filament)

the ____ electrons produced

Answer 17

MORE

Question 18

Increased Voltage Potential = Increased speed of electrons

= ______ energy of x-ray

Answer 18

INCREASED

Question 19

How is voltage potential (energy of the xray) adjusted on

the xray machine?

Answer 19

Using kVp!

Question 20

What are filaments and anodes usually made of?

Answer 20

Tungsten

Question 21

kVp = the _______ of the xray

mAs = the ________ of the xray

Answer 21

kVp= quality of xray

mAs= quantity of xray

Question 22

Increasing kVp increases the ______ of the xray

Answer 22

energy

Question 23

Increasing mAs or time of exposure

increases the _______ of xrays produced

Answer 23

number

Question 24

This principle is responsible for image generation from an x-ray

Answer 24

Photoelectric Effect

Question 25

Due to this effect, the x-ray photon (energy) is completely absorbed, and NO scatter is produced

Answer 25

Photoelectric Effect

Question 26

The probability of photoelectric interaction is directly proportional to Z³, which provides a differential between \_\_\_\_\_\_\_

Answer 26

tissues

Question 27

The higher the value of Z³, the _______ the image, because there is better absorption with a higher value.

Answer 27

WHITER

Question 28

If energy is too high, photoelectric effect is reduced, resulting in \_\_\_\_\_\_\_\_\_\_\_

Answer 28

Contrast Loss

Question 29

This effect is responsible for nearly all scatter radiation in diagnostic radiology

Answer 29

Compton Effect

Question 30

How is the the Compton Effect different from the Photoelectric Effect in regards to the incoming photon energy?

Answer 30

In the Photoelectric Effect, incoming energy is COMPLETELY absorbed. In the Compton Effect, not all energy is absorbed --\> SCATTER!

Question 31

Which effect contributes to film fogging?

Answer 31

The compton effect (scatter radiation)

Question 32

What happens when photographic emulsion (silver halide crystals) is exposed to xrays?

Answer 32

Silver halide crystals precipitate as elemental silver- black dot

Question 33

Increasing kVp and mAs would _____ film blackness

Answer 33

increase

Question 34

\_\_\_\_\_\_ focal spot to film distance would increase film blackness

Answer 34

_decreasing_ FS-FD would increase film blackness

Question 35

The Heel Effect contributes to _______ film blackness

Answer 35

increased

Question 36

Doubling the mAs will _____ the film blackness

Answer 36

_double_

Question 37

Increasing the kVp by \_\_\_\_% will double the film blackness

Answer 37

_15%_

Question 38

What is the standard FS to FD length?

Answer 38

40 - 60 inches

Question 39

This is the effect caused due to a portion of the xray beam being absorbed by the Anode. It results in increased film blackness due to an xray beam that is less intense on the Anode side and more intense on the Cathode side.

Answer 39

The Heel Effect

Question 40

Why would you want to place thicker body parts under the cathode side of an xray machine?

Answer 40

To combat the Heel Effect and give a uniform exposure across the radiograph

Question 41

Motion results in decreased image sharpness. What factors can be put in place to combat this?

Answer 41

Decrease the exposure time Decrease the grid ratio Decrease the FS to FD

Question 42

A long FS to FD _____ detail

Answer 42

INCREASES detail but more mAs is needed

Question 43

Magnification occurs as object-film distance \_\_\_\_\_\_

Answer 43

increases

Question 44

Screen convert xrays into visible light via \_\_\_\_\_\_\_

Answer 44

phosphorescence

Question 45

Screen vs. Non-screen Technique: Which has superior detail but greater exposure?

Answer 45

Non-screen | (greater kVp and mAs)

Question 46

Screen vs. Non-screen Technique: Information from this technique is spread over a larger area

Answer 46

Screen Technique

Question 47

Collimators, Grids, and Shielding all function to limit \_\_\_\_\_\_\_\_\_

Answer 47

SCATTER radiation

Question 48

Grids are characterized by a ratio. The ______ the ratio, the more effective at reducing scatter

Answer 48

higher | (But must increase mAs to compensate!)

Question 49

A Bucky is a device that moves the grid during exposure. What does this prevent?

Answer 49

Moving the grid prevents lines (due to the lead strips in the grids) that would otherwise occur with a stationary grid

Question 50

Scatter radiation ________ as patient size (thickness) increases

Answer 50

_increases_

Question 51

How do you determine if a grid needs to be used?

Answer 51

If the patient is over 10 cm in thickness, use a grid!

Question 52

The opacity difference between adjacent areas on a radiograph is known as

Answer 52

Contrast

Question 53

The number of density gradations between the lightest radiograph shadow and the darkest radiograph shadow is known as

Answer 53

The Scale of Contrast

Question 54

A radiograph with a **high** contrast and *few* shades of gray between the lightest and darkest areas on the radiograph is said to have a _______ Scale of Contrast

Answer 54

_SHORT_

Question 55

A radiograph with **LOW** contrast and *many* shades of gray between the lightest and darkest areas of a radiograph is said to have a _______ Scale of Contrast

Answer 55

_LONG_

Question 56

Another name for Long Scale of Contrast (low contrast)

Answer 56

LATITUDE

Question 57

How is Short Scale of Contrast achieved?

Answer 57

High mAs and Low kVp

Question 58

How is Long Scale of Contrast achieved?

Answer 58

Low mAs and High kVp

Question 59

Abdominal radiographs are taken with a \_\_\_\_\_\_ Scale of Contrast

Answer 59

_SHORT_

Question 60

Thoracic radiographs are taken with a \_\_\_\_\_\_\_\_ Scale of Contrast

Answer 60

_LONG_

Question 61

Why would you want to avoid using expired film?

Answer 61

Film will fog spontaneously when too old

Question 62

A visual cue or signal that is produced by a pathologic change in tissue and may be detected in a medical image

Answer 62

Roentgen (Imaging) Signs

Question 63

What are the 5 opacities?

Answer 63

Gas Fat Soft Tissue = Fluid Opacity Mineral = Bone Opacity Metal

Question 64

False white or black lines that appear at sharp boundaries are due to this phenomenon

Answer 64

Mach Phenomenon

Question 65

Continuous scale from black to white

Answer 65

Analog Gray Scale

Question 66

An area of increased radiopacity (whiteness) that occurs when 2 overlapping objects are in the path of the xray beam and are *not* in contact with one another

Answer 66

Summation

Question 67

When the margins of two objects cannot be distinguished or are difficult to distinguish because of similar opacities and their margins are *in contact* with one another

Answer 67

Silhouetting

Question 68

What is happening in radiograph A?

Answer 68

Silhouetting

Question 69

What is happening in radiograph B?

Answer 69

Summation

Question 70

What is happening in radiograph D?

Answer 70

Summation

Question 71

The blackest shade on a radiograph is most likely \_\_\_\_\_\_\_

Answer 71

GAS

Question 72

The whitest shade on a radiograph is most likely \_\_\_\_\_\_\_ or \_\_\_\_\_\_\_\_

Answer 72

dense bone or metal