Radiology Board Review #1 Theory before anatomy

Question 1

Radiation Discovery: Who and what year?

Answer 1

Wilhelm Conrad Roentgen, 1895
*X-ray: unknown nature
*Discovered when experimenting with a cathode ray tube

*1st dental radiograph took in 1896
—Dr Otto Walkhoff, a German scientist, is credited with creating the first dental radiograph in 1896

Question 2

Radiation

Answer 2

Radiation
*Emission & propagation of energy through space

Question 3

Particulate Radiation

Answer 3

*Tiny particles of matter that posses mass & travel in straight lines at high speeds
*Electrons, bata particles, cathode rays, protons, alpha particles, neutrons

Question 4

Electromagnetic Radiation

Answer 4

*Propagation of wave-like energy (w/out mass) through space of matter
*X-rays, cosmic rays, UV rays, visible light, infrared light, radar waves, microwaves, radio waves
*Vary in energy
*Ionizing vs non-ionizing
*Believed to move through space as both a particle (photon) and a wave

Question 5

X-rays:

Answer 5

Shorter wavelengths: resulting from tungsten target being hit with accelerated e- in a vacuum
Higher frequencies

Question 6

Wave concept:

Answer 6

Velocity:
speed of a wave = speed of light
Wavelength: distance between one crest of one wave and the crest of the next / distance in a periodic wave between 2 points of corresponding phrases
*Determines the energy and penetrating power
Shorter wavelength, higher the energy, more penetrating (harder) the beam
Frequency: # wavelengths that pass a given point in a certain amount of time / # of crests that pass per unit of time

Question 7

Electromagnetic Radiation Wave Theory:

Answer 7

*How radiation propagated in the form of waves
*Useful when considering radiation in bulk when millions of quanta are being examined

Question 8

Electromagnetic Radiation Quantum Theory:

Answer 8

Electromagnetic energy described ad bundles of energy called photons
Successful in correlating experimental data
*interaction of radiation with atoms
*Photoelectric effect
*Production of x-rays

Question 9

Ionization

Answer 9

Most atoms are neutral
*# protons = # electrons
* Ion: atom gains or loses an electron
* Atoms lose an electron, an ion pair results
- Proton = (+)
- Electron = (-)

Question 10

Ionizing Radiation:

Answer 10

radiation that is capable of producing ions

Question 11

Photon:

Answer 11

*Elementary particle responsible for electromagnetic phenomena
*Carrier of electromagnetic radiation of all wavelengths
( gamma, x-ray, UV, visible , infrared, microwave, radio)
*Differs from electron & quark in that it has zero rest mass
*Travels in a vacuum & at the speed of light
*has both wave and particle properties

Question 12

primary Radiation:

Answer 12

X-ray beam that exits the tubehead

Question 13

Secondary Radiation:

Answer 13

X-radiation that is created when the primary beam interacts with matter

Question 14

Scatter Radiation:

Answer 14

*Form of secondary radiation
*X-ray that has been deflected from its path by the interaction with matter

Question 15

Interaction of X-radiation:

Answer 15

1. X-ray can pass through the patient
2. X-ray can be completely absorbed by patient
3. X-ray can be scattered
4. X-ray can be transmitted

Question 16

Light can have 4 fates when hits tissue:

Answer 16

1. Absorbed
   Primary & beneficial effect of laser energy
2. Reflected
   Beam redirecting itself off the surface, no effect on tissue.
   Ex: caries-detecting laser
3. Scattered
   May harm surrounding structures
4. Transmitted
   May harm surrounding structures
   Laser energy directly through tissues

Question 17

Bremsstrahlung Radiation:

Answer 17

*Produced by sudden slowing or stopping of e- towards a target
*Primary source of x-rays
*Negatively charged e- directed towards a (+) charged source ——>loss of velocity occurs
*Generate continuous spectrum of photons

Question 18

Characteristic Radiation:

Answer 18

*Only a minor source of radiation
*e- from filament displaces an e- from a shell of tungsten target atom - atom ionizes

Question 19

Properties of X-Rays

Answer 19

*Characteristics: invisible, no mass, no weight
*Travel: in a straight line, at the speed of light
*Wavelengths:
- Have shorter wavelengths, high frequency
- Hard x-rays: short, high penetration
- Soft x-rays: longer less penetrating, more likely to be absorbed into the tissues
*Penetration: pass through matter or absorbed by matter, depending on atomic structure of matter
*Produces: an image on photographic film
*Causes: Ionization
*Distance: lose intensity with distance

Question 20

Image Characteristics
Detail / Resolution / Definition:

Answer 20

*Over sharpness of image
*Called “radiographic definition”
*Relates to distinct and sharp demarcation of image elements
*Focal spot size: smaller = sharper image
*Film composition: smaller silver halide crystals = sharper image
*Movement of film or patient during exposure = less sharp image
*Influenced by: PID length, type of films, use of intensifying screens

Question 21

Image Characteristics
Penumbra (“fuzziness or un-sharpness”):

Answer 21

1. Source of radiation large
   *Small focal spot keep penumbra small
   *Large focal spot keep penumbra go up / bigger
2. Source to object distance
   *Long SOD will go down penumbra(magnification), short SOD will go up penumbra(magnification)
3. Object to film distance
   *Small object-to-film distance go down penumbra(magnification)
   *Large object-to-film-distance will go up un-sharpness

Question 22

Image Characteristics
Sharpest image with least distortion:

Answer 22

1. Small focal spot
2. Short object-to-film-distance
3. Large targe(source)-to-film-distance
4. Film and tooth parallel
5. Beam perpendicular to film

Question 23

Image Characteristics
Density:

Answer 23

*Overall Darkness or lightness
*More photons = more density
*influenced by: film type, processing, exposure time. mA(milli amperage) settings, PID length, kVp setting, source to object distance

Question 24

Image Characteristics
Contrast:

Answer 24

*Variations of gray and between white and black
*How sharply dark and light areas are separated
*Influenced by: patient size, film type, processing, film storage, Mainly kVp setting

Question 25

dental x-ray PID:

Answer 25

PID: positioning indicator device
Where the x-ray beam exposes the receptor. The x-ray head and the PID are lead lined to contain the x-ray and prevent unnecessary radiation exposure to the patient and the operator.
The PID is also called a cone.

Question 26

Dental radiology—-KVP:

Answer 26

kVp (kilovoltage) control —– regulates the high voltage electrical circuit by adjusting the potential difference between the electrodes.
Altering the kilovoltage setting influences the quality or penetration of the x-rays produced and image contrast or differences in density.

Question 27

Image Characteristics
High contrast / short scale:

Answer 27

*Few shades of gray, mostly black and white
*High visual contrast
*Produced by low kVp settings
*Less than 75kVp

Question 28

Image Characteristics
Low contrast / Long Scale:

Answer 28

*Many shades of gray
*Low visual contrast
*Produced by high kVp
*Settings higher than 80kVp

Question 29

Image Characteristics
Radiolucent:

Answer 29

*Portion of a processed radiograph that is dark or black
*Things that permit the passage of x-rays
*Air space, soft tissue

Question 30

Image Characteristics
Radiopaque:

Answer 30

*Portion of a processed radiograph that is light or white
*Structures that absorb x-rays
*Enamel, dentin, bone, metals

Question 31

Image Characteristics
Magnification:

Answer 31

*Image appears larger than the actual size of the object it represents
*Decrease object-film distance decrease magnification(tooth close to film)
*Increase target-to-film distance decrease magnification (use a longer PID or cone)

Question 32

Image Characteristics
Distortion:

Answer 32

*Variation in the true size and shape of the object being radiographed
*May be unequal magnification of different parts of the same object
*Results from improper film alignment or angulation of the x-ray beam
*To minimize distortion:
1. Object and film must be parallel
2. X-ray beam must be directed perpendicular to the tooth and film

Question 33

Attenuation:

Answer 33

Process where radiation loses power as it travels through matter. (Removal of x-ray photons)
* As the energy of radiation to up^, the # of photons passing through matter go up^
* As density, atomic #, electrons per gram of material go up^, the # of photons passing through the matter go down

Question 34

Elongation:

Answer 34

*Central ray not perpendicular to object
*Object and film not parallel
*Insufficient vertical angulation

Question 35

Foreshortening:

Answer 35

*Central ray not perpendicular to films
*Object and film not parallel
*Excessive vertical angulation