Chapter 4: Radiographic imaging Flashcards
1
Q
What can we record in the bitewing view?
A
The coronal maxillary portion and mandibular teeth
2
Q
What can we observe in the cephalometric radiograph?
A
- Diseases
- Impacted teeth
- Trauma
- TMJ
- Abnormalities
- Relationship between orofacial and dental structures
- Growth and development
- Treatment progression
3
Q
Radiology is the study of
A
The study of the effects of ionising radiation on living systems
4
Q
What happens when an atom loses an electron?
A
It becomes a positive ion, and the free electron becomes a negative ion
5
Q
Requirement to get ionisation:
A
Energy
6
Q
Ions formed from the atom acquire a negative or positive charge
A
- Subatomic particle
- Other atoms
- Molecules
- Ions
- Light
7
Q
We need a specific type of radiation to ionise the matter.
True or False.
A
True
8
Q
What is radiation?
A
It is the emission or transmission of energy in the forms of waves or particles through space or through a material medium
9
Q
Types of radiation
A
- Electromagnetic radiation
- Particle radiation
- Acoustic radiation
- Gravitational radiation
10
Q
Non ionising: they do not produce enough ______
A
Energy
11
Q
Non ionising radiations
A
- Visible light
- Infrared
- Microwave radiation
- Radio waves
12
Q
We need enough _____ to alter the matter, to ionise
A
Energy
13
Q
Transmission of energy through space and matter has 2 types:
A
- Particulate
- Electromagnetic
14
Q
What is particulate?
A
When atoms break up releasing alpha or beta –> radioactivity
15
Q
Is particulate dangerous?
A
Yes
16
Q
What is electromagnetic (EM)?
A
These waves are propagating through time-space carrying electromagnetic energy
17
Q
What is less harmful, the particulate or the electromagnetic?
A
The electromagnetic is less harmful
18
Q
Types of EM
A
- Gamma rays
- X-rays
- Ultraviolet rays
- Visible light
- Infrared (heat)
- Microwaves
- Radiowaves
19
Q
Gamma rays and X-rays have enough energy to ionise, so they have higher energy. They are ______
A
Ionising matters
20
Q
What radiology only involves electromagnetic radiation?
A
Oral and maxillofacial radiology
21
Q
How does the X-ray machine work?
A
It produces an X-ray that passes through the patient’s tissues and strike a digital receptor or film to make a radiography image
22
Q
What is an X-ray tube?
A
It is a cathode and anode situated with an evacuated glass envelop or tube
23
Q
Who created the X-ray tube and when?
A
Wilhelm Röntgen, a German scientist on November 8, 1895
(he has a Nobel prize in physics)
24
Q
Factors controlling the radiographic imaging
A
- X-ray beam
- Objects
- Digital receptor/film
25
What happens when we modify the exposure time?
Changing the exposure time modifies the duration of the exposure and thus the number of protons generated
26
What does the exposure time control?
The density and the contrast
27
The quantity of radiation produced by an X-ray tube is ______ ______ to the tube current (mA) and the time the tube is _______ (exposure time)
Directly proportional, operated
28
What does the tube current control?
Density
29
What does mA stand for?
Milliamperes; a unit representing the amount of current passed through the X-ray tube
30
What does increasing the tube voltage peak (kVp) do?
it increases the potential difference between the cathode and the anode, increasing the energy of each electron when it strikes the target
31
The greater the energy of an electron, the _____ probability it will be converted into X-rays photons
Greater
32
What does the tube voltage peak involve?
Contrast
33
What does kVp stand for?
Kilo-voltage
34
What does the distance tube-film do?
It affects the radiation intensity and exposure time
35
What does the distance tube-film involve?
Quality
36
If you increase the distance, you _____ the exposure time
Increase
37
What is a collimator?
It Is a metallic barrier with an aperture in the middle
38
What is the collimation used for?
- To restrict the size of the X-ray beam and the volume of the tissue irradiated
- It reduces the exposed volume and the patient's exposure
- The collimator will restrict, narrow and direct the X-ray beam
39
What does the collimation improve?
The image
40
What does filtration do?
it removes low-energy photons from the beam while allowing high-energy photons that are able to contribute to making an image to pass through
41
By law, all the units should have a _____ and a _____
Collimator and Filter
42
What is the inverse square law?
The intensity of an X-ray beam is inversely proportional to the square of the distance between the source and the point of measure
43
What happens when the source of the target is doubled?
The intensity of the beam decreases to 1/4
44
The image will decrease in distance (inverted square law). True or False.
False. It increases in distance, the final image will be bigger
45
The quality of radiography does not vary from one device to another. True or False
False, the quality of radiography can vary from one device to another
46
X-ray beam properties
1. Exposure time
2. Tube current (mA)
3. Tube voltage peak (kVp)
4. Distance tube-film
5. Collimation
6. Filtration
7. Inverse square law
8. Device efficacy
47
The greater the thickness of an object, the ____ the radiation intensity
Greater
48
What does the thickness of the object increase?
The mA, kVp, and exposure time
49
X-rays are absorbed proportionally to the mass (density) they go through. True or False
True
50
What does the density increase?
The mA, kVp, and exposure
51
Object properties
1. Thickness
2. Density
52
Digital receptor film properties
1. Films: the thickness of the emulsion, screens, radiographic speed
2. Intensifying screens: creates an imagined receptor system that is 10 to 60 times more sensitive to x-ray than the film alone
3. Film develop: contrast, density, fog, and sharpness
53
If we have a good intensifying screen we will need so much exposure time. True or False
True
54
When the radiation strikes the patient, ____ happens
Attenuation
55
When attenuation happens, the X-ray beam is ____ in intensity as the body acts as a barrier
Reduced
56
Types of attenuation
- Absorption interactions (type 1): absorption of individual photons in the beam by atoms in the absorbing tissues
- Scattering interactions (type 2): photons are scattered out of the beam
57
Type of tissue exposed in interactions of X-ray with matter
- Bone: hard tissue, whitish, radio-opaque
- Soft tissues: blackish, radiolucent
58
Match the letters with the numbers:
A. More likely to absorb X-ray photons
B. More likely to let them pass through
1. Soft tissues
2. Bone
A. 2
B. 1
59
The 3 means of beam attenuation (absorption or scattering)
- Coherent scattering
- Photoelectric absorption
- Compton scattering
60
Coherent scattering:
Rayleigh, classical, elastic scattering
- Low energy photon
- Interacts with a whole atom
- It ceases to exist
- The excited generated another X-Ray photon
61
Photoelectric absorption:
- Primary contributor to the image
- Incident photon interacts with an electron in an inner orbital of an atom
- The photon ejects the electron and it becomes a recoil electron --> photoelectron
62
Compton scattering:
- Secondary contributor to the image (second best contributor)
- Reduces contrast
- The photon interacts with an outer orbital electron
- The outer receives kinetic energy and recoils from the point of impact
63
Match the letters with the numbers:
A. Happens 7% of the time
B. Happens 57% of the time
C. Happens 27% of the time
1. Compton scattering
2. Photoelectric absorption
3. Cohering scattering
A. 3
B. 1
C. 2
64
What is the best type of attenuation in terms of contribution to the image?
The photoelectric absorption
65
In geometric enlargement:
- The image of the film is _____ than the object
- When the distance of the focal spot increases, the image ____
- Larger
- Decreases
66
Intraoral devices
- Backbone
- Periodical
- Bitewing
- Occlusal
- Diagnostic information
- Clinical procedures
67
What is panoramic imaging (pantomography)?
An X-ray source and image receptor rotate around the patient's head and create a panoramic image of both the maxillary and mandibular dental arches and their supporting structures
68
When is panoramic imaging used?
- Diagnostic problems requiring broad coverage of the jaws
- Initial evaluation
- Patients who do not tolerate intraoral procedures well
69
Problems of panoramic imaging
- Does not display the fine anatomic detail
- Unequal magnification and geometric distortion
- Overlapped structures
70
Numerous technological innovations have driven the shift from film to digital systems. True or False
True
71
Digital imaging properties
- Processing time
- Film, developing (chemical solutions)
- Image interpretation: enhancements, measurements, corrections
- Image transferring
- Radiation is reduced by 80% as the exposure time is reduced
72
Disadvantages of digital imaging
- Costly
- Expensive components
- Systems becoming obsolete
73
Film imaging components
1. Emulsion:
- Sensitive to X-ray and visible light
- Silver halide grains
2. Base:
- Plastic supporting material
- Provides flexibility
- Uniformly translucent
74
Film techniques
1. Periapical (several sizes)
2. Bitewing (paper tab to support the film)
3. Occlusal (the patient bites the film they might feel uncomfortable)
75
What can we see in the periapical view?
- Crowns, roots and the surrounding bone
76
What can we see in the bitewing view?
- Coronal portion of the maxillary and mandibular teeth
- Interproximal caries
- Height of the alveolar bone
77
What can we see in the occlusal view?
- Larger areas of the maxilla and mandible teeth
78
What radiographs have intensifying screens?
Panoramic and Cephalometric
79
Steps of film processing
- Immerse exposed film in the developer
- Rinse the developer off the film in the water bath
- Immerse film into the fixer
- Wash fill in water to remove the fixer
- Dry the film and mount it for viewing
- Darkroom and equipment
- Automatic film processing
80
What is radiation dosimetry?
It is the measurement calculation and assessment of the ionising radiation dose absorbed by an object, usually the human body
81
Principles of safety and protection
1. Justification: benefit-risk
2. Optimisation: reduce unnecessary exposure
3. Dose limitation: dose limits for dentist and staff
82
Standards for patients
- Justification; influences what the patients are selected for radiographic examination
- Pregnancy
- Filtration and collimation devices
- Exposure time reduction
- Source to skin distance: 40 cm
- Barriers: leaded aprons and thyroid collars (for the patient)
83
Standards for personnel
- Avoid primary beam
- Position and distance rule
- Dosimetric control: dosimeters, measure absorbed dose from ionising radiation
- Leaded aprons
