Dental Radiology - Midterm

Front 1

Exposure

Back 1

Is the measure of radiation quantity, the capacity of radiation to ionize air. SI unit is Kerma – Kinetic energy released in matter

Front 2

Dose

Back 2

Is the measure of the energy absorbed by any type of ionizing radiation per unit mass of any type of matter. SI unit is gray (Gy)

Front 3

Formula for Intensity

Back 3

(no. of photons in beam × energy of each photon) / (area × exposure rate)

Front 4

Intensity

Back 4

The total energy contained in the beam per unit area per unit time.

Front 5

What two characteristics describe intensity?

Back 5

Quality and quantity

Front 6

Intensity depends on what five factors?

Back 6

target material
KVp
mA
Exposure time
Source to film distance (SFD

Front 7

When there is increase in KVp by 15, should you indcrease or decrease the exposure time by half?

Back 7

Decrease

Front 8

Short wavelength, high frequency and greater energy are characteristic of Hard or Soft X-rays?

Back 8

Hard

Front 9

Long wavelength, low frequency, and low energy are characteristic of Hard or Soft X-rays?

Back 9

Soft

Front 10

mA determines the number of ______?

Back 10

Photons

Front 11

mAs or mAi is the product of what?

Back 11

mA and time in seconds or impulses

Front 12

1 Impulse is equivalent to what?

Back 12

1/60th of a second

Front 13

Formula for Inverse Square Law

Back 13

I1/I2 =(D2)2/(D1)2

Front 14

Why is there a rapid decrease in intensity with increasing distance in an x-ray beam?

Back 14

Because the total light emitted is spread out over an increasingly larger area.

Front 15

When changing from 8 inches PID to 16 inches PID, what needs to be done to the exposure time?

Back 15

Needs to be increaseed by the square of the distance or a factor of 4 to get same density on the film.

Front 16

Federal regulations needs x ray source to be not less than ___ inches for an x ray tube operating at or above ___ KVp.

Back 16

7 ; 50

Front 17

Attenuation

Back 17

Reduction in the intensity of the beam either by absorption (photoelectric effect) or scattering (compton scatter)

Front 18

What are the three types of interactions of x-rays with matter?

Back 18

Coherent scattering
Photoelectric absorption
Compton scattering

Front 19

Why is the photoelectric effect the most important interaction in production of radiographs?

Back 19

Because it produces radiopaque and radiolucent areas on a radiograph.

Front 20

True/False: Energy is transferred during Coherent Scattering.

Back 20

False

Front 21

-5-8% of total interactions
-Produced by low energy photons (less than 10 KeV)
-Contributes very little to film fog

Back 21

Coherent Scattering

Front 22

Interaction of a low energy photon with an outer shell electron, producing a photon with the same energy but different direction, is termed what?

Back 22

Coherent Scattering

Front 23

The probability of photoelectric effect is in inversely proportional to...

Back 23

The third power for the x-ray energy

Front 24

The probability of photoelectric effect is directly proportional to

Back 24

The third power of the atomic number of the absorbing material

Front 25

Photoelectric interaction cannot occur unless the...

Back 25

Incident x-ray has energy equal to or greater than the electron binding energy

Front 26

In photoelectric absorption, the recoil/photoelectric electron travels a short/long distance and gives off the energy by primary/secondary ionzation.

Back 26

short; secondary

Front 27

What percent of photons are absorbed by photoelectric process

Back 27

30%

Front 28

In Photoelectric Absorption, most interaction occurs in which shell?

a. K shell
b. L shell
c. M shell
d. N shell

Back 28

a. K shell

Because the incident photon displaces an inner shell electron

Front 29

True/False: In Photoelectic Absorption, the photon ceases to exist.

Back 29

True; It is total x ray absorption interaction

Front 30

Atomic number (Z) of a) compact bone and b) soft tissue are?

Back 30

a)13.8
b)7.4

Front 31

Name the 4 factors that influence Photoelectric Absorption

Back 31

1. The wavelength or photon energy of the x-ray
2. Thickness of the material
3 Density of the material
4. Atomic number of the material.

Front 32

Higher KVP = shorter/longer wavelength x rays, which penetrate the material more/less readily.

Back 32

shorter; more

Front 33

True/False: Thicker piece of any material results more x-radiation absorption than a thinner piece of the same material.

Back 33

True

Front 34

The more dense a material, the less x-radiation absorbed.

a. Both statements false.
b. First false, second true.
c. First true, second false.
d. Both statements true.

Back 34

c.

Front 35

True/False: Atomic number of an object usually has far less of an effect on x-ray absorption than thickness or density.

Back 35

False. It has far more of an effect.

Front 36

True/False: The characteristic radiation that occurs during Photoelectric absorption does not contribute anything of diagnostic value.

Back 36

True

Front 37

Compton scattering reduces/increases contrast in an x-ray image

Back 37

reduces

Front 38

True/False: The probability of Compton effect is inversely proportional to energy and independent of atomic number.

Back 38

True

Front 39

In Compton Scattering: photons interact with inner shell electrons, creating scattered photons that contribute to film fog.

a. Both statements true.
b. First true, second false.
c. First false, second true.
d. Both statements false.

Back 39

c.

Front 40

In Compton Scattering, what percent of photons in the dental X ray beam are absorbed by this process?

Back 40

62%

Front 41

Attenuation:

Back 41

The reduction in the intensity of the x-ray beam as it traverses dental tissues by either the absorption (photoelectric) or (Compton) scattering of photons from the x-ray beam

Front 42

True/False: If only photoelectric effect is considered. X-rays that undergo photoelectric absorption produce negative diagnostic information

Back 42

True

Front 43

X-rays that do not reach the film represent structures that have low/high absorption characteristics and results in white/black areas on the film, are termed radiopaque/radiolucent

Back 43

high; white; radiopaque

Front 44

Which tissue structures look radiopaque on radiographs?

Back 44

Cortical Bon
Enamel
Metallic Restorations

Front 45

X-rays that penetrate the jaws and are transmitted with no interactions whatsoever are termed radiopaque/radiolucent

Back 45

Radiolucent

Front 46

Which tissue structures look radiolucent on radiographs?

Back 46

Soft Tissue
Pulp
Periodontal Ligament

These are easily penetrated by the x-ray

Front 47

Order the differential absorption of x-rays by these structures from most to least:

Enamel
Cementum
Metallic Restorations
Dentin
Cortical Bone
Soft Tissue
Cancellous Bone

Back 47

Metallic Restorations > Enamel > Dentin > Cementum > Cortical Bone > Cancellous Bone > Soft Tissue

Front 48

What type of filter is used in radiograph machines?

a. Tungsten
b. Tin
c. Copper
d. Molybdenum
e. Aluminum

Back 48

e. Aluminum

Front 49

The filtration apparatus of radiograph machines reduces low/high energy long/short wavelength photons

Back 49

low; long

Front 50

The 3 components that contribute to Inherent Filtration are:

Back 50

Glass wall
Insulating oil
Barrier to prevent oil from escaping

Front 51

Inherent filtration =

a. 0.5 - 1 mm of Aluminum
b. 0.5 - 2 mm of Aluminum
c. 1.0 - 1.5 mm of Aluminum
d. 1.0 - 2 mm of Aluminum

Back 51

b.

Front 52

True/False: Total Filtration = Inherent Filtration + Added Filtration

Back 52

True

Front 53

If using a 70 kVp radiograph machine, you should have 0.5 mm of aluminum; all higher voltages require 2.5 mm.

a. Both statemnts true
b. First true, second false.
c. First false, second true.
d. Both statements false.

Back 53

c. For 70 kVp, should have 1.5 mm of aluminum

Front 54

A Collimator is made up of what 2 components?

Back 54

Rectangular PID (position indicating device) & rectangular collimator

Front 55

Collimation:

Back 55

Means to alter the shape of an x ray beam, usually by the use of a metallic barrier with an aperture in the middle

Front 56

True/False: Rectangular PID has an area of approx. 3.5×4.4cm this reduces the pt. exposure by 60% compared to the round PID with a diameter of 7 cm.

Back 56

True

Front 57

True/False: Non screen film are used for intraoral radiographs whereas screen films are used in extraoral radiography

Back 57

True

Front 58

Screen films are used in combination with screens to increase/reduce the patient dose

Back 58

reduce

Front 59

True/False: Non screen films are exposed by x rays and screen films are exposed by visible light

Back 59

True - Intraoral views: only place where direct exposure films and no screens are used

Front 60

The efficiency with which a film responds to x-ray exposure is known as...

Back 60

Film sensitivity or speed

Front 61

Exposure time and film speed varies proportionately/inversely?

Back 61

Inversely

Front 62

Speed of the film is designated alphabetically from A to F. Federal recommendations requires the use of film with greater then C speed.

a. Both statements true
b. First false, second true.
c. First true, second false.
d. Both statements false.

Back 62

C - Federal recommendations requires the use of film with greater then E speed.

Front 63

Arthur A. Dugoni school of dentistry policy mandates the use of __ speed film.

Back 63

F

Front 64

Match the film size to the use:

2: patients with small mouth or pediatric cases
0: used for anterior PA radiographs
4: used for posterior PA & BW radiographs
1: used for occlusal views

Back 64

0: patients with small mouth or pediatric cases
1: used for anterior PA radiographs
2: used for posterior PA & BW radiographs
4: used for occlusal views

Front 65

Emulsion consists of homogeneous mixture of ________ and _______ crystals.

Back 65

gelatin; silver halide

Front 66

True/False: Gelatin is clear so that it will transmit light, and sufficiently porous to allow the processing chemicals to penetrate it

Back 66

True

Front 67

True/False: Base is composed of thin clear plastic made of triacetate or polyester that is 0.007 inches (0.25 mm) thick

Back 67

True

Front 68

What is the active ingredient in the radiographic emulsion?

Back 68

Silver Halide or silver iodo-bromide crystals

Front 69

Placing the film on the wrong sides results in what on radiographs?

Back 69

"tire-marks"

Front 70

If you expose film before radiograph is taken, film will look brighter/darker?

Back 70

darker

Front 71

The dimple on the film should be located where?

a. Apical 3rd of tooth
b. Middle 3rd of tooth
c. Coronal 3rd of tooth
d. Facing the PID
e. C and D

Back 71

E

Front 72

True/False: Formation of latent image, which cannot be seen by the naked eye; will be visible after it passes through chemicals

Back 72

True

Front 73

All are true, EXCEPT:

a.Intensifying screenings are used in pairs, one on each side of the film
b.Intensifying screens are positioned inside the cassette
c.The purpose of the cassette is to hold each intensifying screen in contact with the x-ray film to maximize the sharpness of the image
d.Most cassettes are flexible but they may be rigid.

Back 73

d - Most cassettes are rigid, but they may be flexible

Front 74

Screen films have more/less reolution than non-screen films

Back 74

less

Front 75

The Film-Screen combination is used for:

a. Intraoral radiographs
b. Extraoral radiographs
c. Intra & Extraoral radiographs

Back 75

b

Front 76

True/False: The Base provides mechanical support for other layers. May be coated by a reflecting layer to improve image sharpness.

Back 76

True

Front 77

Which is the most important layer of a screen?

a. Supercoat
b. Phosphor Layer
c. Reflecting Layer
d. Base

Back 77

b

Front 78

Phosphor Layer

Back 78

Composed of phosphorescent crystals suspended in a polymeric binder. Most commonly lanthanum and gadolinium

Front 79

Supercoat/ Protected polymer coat

Back 79

About 15 µm is placed over the phosphor layer to protect the phosphor and provide a surface that can be cleaned

Front 80

What is the major advantage of using extraoral screen and film combinations?

Back 80

You reduce the amount of exposure to a patient

Front 81

What is the major disadvantage of using extraoral screen and film combinations?

Back 81

The resolution is not that good

Front 82

Fast screens have small/large phosphor crystals and efficiently convert x-ray photons to visible light, but produce images with lower/higher resolution

Back 82

large; lower

Front 83

As the size of the crystals or the thickness of the screen decreases/increases, the speed decreases/increases, but image sharpness increases/decreases

Back 83

decreases; decreases; increases

Front 84

If you want good resolution on your radiographs, would you prefer a slower or faster speed screen?

Back 84

slower

Front 85

The speed and resolution of screens depends on:

a. Phosphor type and phosphor conversion efficiency
b. Thickness of phosphor layer
c. Presence of reflective layer
d. Phosphor grain size
e. All of the above

Back 85

e

Front 86

Radiographic density refers to the degree of blackness/whiteness on a radiographic film

Back 86

darkness

Front 87

Factors affecting radiographic density include:

a. mAs
b. KVP
c. Source to the film distance
d. All of the above

Back 87

d

Front 88

True/False: As the exposure time (t) and tube current (I) are increased, the density of the radiographic image also increases

Back 88

True

Front 89

Overall darkness of the film is called...

Back 89

Film Density

Front 90

Optical density =

Back 90

Log10 I0/It

I0: intensity of the light from the viewbox

It:intensity of the light transmitted from the film.

Front 91

Radiographic Density =

Back 91

Intensity of incident light minus intensity of transmitted light

Front 92

True/False: If film is very dark (entity is dark), you won’t have a lot of light photons being transmitted

Back 92

True

Front 93

True/False: A radiopaque portion of a radiograph will correspond to the thickest portion and the smallest optical density

Back 93

True because the thicker the subject, the more the beam is attenuated and the lighter the resultant images

Front 94

A characteristic curve is a plot of relationship between film ______ _______ & _______

Back 94

optical density; exposure

Front 95

Radiographic Contrast:

a. Describes the range of densities on a radiograph
b. Is defined as difference in densities between light and dark areas on a radiograph
c. Is affected by KVP
d. Affects how many shades of gray can be seen on a radiograph
e. All of the above

Back 95

All of the above

Front 96

When you increase KVP, you increase/decrease the contrast

Back 96

decrease; this means that it's more difficult to tell the difference between two shades of gray

Front 97

All of the following will lead to less subject contrast EXCEPT:

a. greater thickness
b. greater density
c. greater distance
d. higher atomic number

Back 97

c

Front 98

Film Contrast:

Back 98

The capacity of the radiographic film to display differences in subject contrast

Front 99

Film contrast is measured as:

Back 99

The average slope of the diagnostically useful portion of the characteristic curve

Front 100

Radiographic Speed:

Back 100

The amount of radiation required to produce an image of standard density

Front 101

True/False: As the speed of the film is increased, the amount of exposure required to produce standard density increases as well

Back 101

False; it decreases - less exposure time

Front 102

Sharpness

Back 102

The ability of a radiograph to define an edge

Front 103

Resolution

Back 103

The ability of recording separate structures that are close together

Front 104

Resolving Power

Back 104

Measured as the number of line pairs

Front 105

True/False: Digital Radiographs have better resolution

Back 105

False

Front 106

True/False: Panoramic film screen combination can resolve about 5 lines per millimeters whereas PA films, which can delineate clearly more than 20 line pairs/mm

Back 106

True

Front 107

The greater the latitude, the steeper the slope.

a. Both statements true.
b. Fist false, second true.
c. First true, second false.
d. Both statements false.

Back 107

c

Front 108

All of the follwing are true about the Parallex Effect EXCEPT:

a. Causes unsharpness
b. Occurs when double emulsion films are used
c. Slight magnification occurs on the side away from the x ray source
d. All of the above are true

Back 108

d

Front 109

Decreasing the angle of the anode = increases/decreases the effective focal spot size = increasing/decreasing the sharpness

Back 109

decreases; increasing

Front 110

Increasing the distance between the focal spot and the object results in increased/decreased sharpness and decreases/increases magnification of the object.

Back 110

increased; decreases

Front 111

Decreasing the distance between the object and the film decreases/increases the sharpness and decreases/increases the magnification of the object.

Back 111

increases; decreases

Front 112

When the central ray is perpendicular to the film but the object is not parallel with the film, this results in...

Back 112

Foreshortening of the radiographic image

Front 113

When the central ray is perpendicular to the object but not the film, this results in...

Back 113

Elongation of the radiographic image

Front 114

Latent Image

Back 114

The invisible image that is produced in film emulsion by light or x-rays and is converted into a visible image after processing

Front 115

What creates the latent image?

Back 115

The AgBr crystals

Front 116

Temperature of processing solutions in the tanks should be...

Back 116

70°F

Front 117

Automatic processing involves all of the following EXCEPT:

a. Development
b. Rinsing
c. Fixation
d. Washing
e. Drying

Back 117

b. Rinsing

Front 118

What is the purpose of the developer?

Back 118

To chemically reduce the exposed silver halide crystals (those with a latent image) into black metallic silver

Front 119

The developer solution also _______ the film emulsion during this process

Back 119

Softens

Front 120

The developer solution contains oxidizing/reducing agent which interact with silver ions in the crystals and convert them to solid grains of metallic silver

Back 120

Reducing

Front 121

Areas with many exposed crystals are more/less dense because of their lower/higher concentration of black metallic silver grains after development

Back 121

more; higher

Front 122

All of the following are components of developing EXCEPT:

a. Developer
b. Activator
c. Condensor
d. Preservative
e. Restrainer

Back 122

c. Condensor

Front 123

The reducing agent in the Developer is:

Back 123

Hydroquinone (Paradihydroxy benzene)

Front 124

Activators:

Back 124

Alkali compounds such as sodium or potassium hydrozide

Front 125

Developer are active only at alkaline pH values around pH:

Back 125

pH = 10

Front 126

Which is true?

a. It is an anti-oxidant
b. It is composed of sodium sulfite
c. Protects developer from oxidation by atmospheric oxygen & extends longevity of developer
d. Combines with the brown oxidized developer to produce a colorless soluble compound
e. All of the above

Back 126

e

Front 127

All are true of the Restrainer EXCEPT:

a. Made of potassium bromide and benzotriazole
b. Restrains development of unexposed silver halide crystals
c. Antifog agent
d. increases contrast
e. Restrians development of exposed crystals

Back 127

e

Front 128

True/False: Rinsing is usually done for 20 seconds under safelight conditions.

Back 128

True

Front 129

Fixing removes AgBr crystals which were/were NOT exposed by x-radiation

Back 129

Were NOT

Front 130

All of the following are true about Fixing EXCEPT:

a. Film must be kept in fixer for minimum of 5 minutes
b. Removes the unexposed silver halide crystals from the film emulsion
c. Hardens the film emulsion during this process
d. Films may be removed from the fixing solution after 3 minutes for viewing

Back 130

a. Films are to be kept in fixing solution for a minimum of 10 minutes

Front 131

All are components of Fixing EXCEPT:

a. Clearing Agent
b. Acidifier
c. Preservative
d. Activator
e. Hardener

Back 131

d. Activator

Front 132

Clearing Agent is:

Back 132

Ammonium Thiosulfate: dissolves the unexposed silver halide grains

Front 133

Which is true of the Acidifier?

a. It is an acetic acid buffer system (pH 4-4.5)
b. Promotes good diffusion of thiosulfate into emulsion and silver thiosulfate complex out of emulsion
c. Neutralizes any developer solution still present on the film
d. All of the above

Back 133

d. All of the above

Front 134

If you put the film in the fixer before you put it in the developer, you’ll get _________ film.

Back 134

Radiopaque (white)

Front 135

The Fixing Preservative is:

Back 135

Ammonium Sulfite

Front 136

Which is true of the Fixing Preservative?

a. Prevents oxidation of thiosulfate clearing agent
b. Binds with any colored oxidized developer carried over into fixing solution
c. Both above are true

Back 136

c

Front 137

What is the Fixing Hardener

Back 137

Aluminum Sulfate

Front 138

Which is true of the Fixing Hardener?

a. Made of Aluminum Sulfate
b. Complexes with gelatin and prevents damage during subsequent handling
c. reduces swelling of the emulsion during the final wash
d. lessens mechanical damage to the emulsion and limits water absorption, thus shortening drying time
e. All of the above

Back 138

e. All of the above

Front 139

Washing step requires about 20 mintues (for manual processing). Films must be air-dried at room temperature.

a. Both statements true.
b. First true, second false.
c. First false, second true.
d. Both statements false.

Back 139

a. Both statements true

Front 140

Safelighting: X ray film are very sensitive to light in _______ region and less sensitive to _______ and ____ wavelengths.

Back 140

blue-green; yellow and red

Front 141

Handling under safelight should be limited to about ___ minutes

Back 141

5

Front 142

All are true of Darkroom lighting EXCEPT:

a. Handling under safelight should be limited to 5 min
b. Keep safe distance betwween light & working area
c. Unwrapped films exposed to safelight for more than 2-3 minutes will appear fogged
d. Safelight must be placed a minimum of 10 feet away

Back 142

d. A minimum of 4 feet is best