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NBDE II Board Busters > Radiology > Flashcards

Flashcards in Radiology Deck (71):
1

Rank from least to most radiopaque

PDL space
dentin
enamel
ZOE
amalgam

2

most __ lesions are well-defined unilocular

90% of the time, diffuse radiolucencies indicate __

benign

CANCER - if there is a loss of cortical plates, the first dx is cancer

3

osteoradionecrosis is

most common factors precipitating osteoradionecrosis are (2)

necrosis of bone produced by ionizing radiation that is more common in the mandible > max (cause richer vascular supply to max)

factors - pre and post-irradiation extractions and perio disease

4

damage to __ predisposes a pt to developing osteoradionecrosis

it's a complication that can occur in pts taking what meds?

blood vessels!

IV bisphosphonates, or oral bisphosphonates > 3yrs (ex. Fosomax)

5

bony projection that arises from the sphenoid bone and extends down and posteriorly is the

hamular process

6

coronoid process usually seen on which films?

PAs of molars in maxilla

tapered or triangular radiopaque below or superimposed on molars of maxilla

7

how long should dental xrays be retained?

legally, radiographs are property of who?

indefinitely

the dentist! but pt has right to reasonable access

pts can refuse dental xrays, but entist must decide if an accurate dx can be provided or tx can be provided

8

why do digital xrays require less radiation?

reduced by what %?

sensor is more sensitive to xrays

50-80% less

9

storage phosphor imaging system uses what instead of a sensor?

reversible imaging plate, more flexible and comfortable

10

a direct digital imaging system works using

intraoral sensor attached to a fiberoptic cable

11

indirect digital imaging system works by

scanning an existing xray and digitizes the image

12

the most common digital image recptor is the

charge-coupled device (CCD)

-solid state detector with silicon chip
-also used in home video cameras, fax machines, telescopes

13

primary radiation is generated at the __ of the xray tube

ANODE, and is attenuated by the filter and object

14

secondary radiation "Scattered"

from interactions of primary radiation beam with atoms in the object
-major source of image degradation

15

in secondary radiation (scattered) what 3 interactions can occur

coherent scatter
photo electric absorption
Compton scattering <-- cause most scattered xrays in dx imaging

16

how can you best reduce the amt of scatter radiation? by using a __, __ cone

leaded, rectangular cone (PID)

17

in normal dental dx procedures, who receives the greatest hazard from secondary scatter radiation?

operator

18

collimation is the control of ___ and ___

the control of SIZE and SHAPE of the xray beam

19

the diameter of a circular beam of radiation at the pt's skin can't be larger than __ inches

2.75

20

xray beam is composed of rays of diff. wavelengths and penetrating power (polychromatic) because

the potential across the xray tube constantly changes as the kilovoltage changes

21

are short or long wavelength xrays useful?

SHORT are useful, and long are useless!
Short ones (high energy) have good penetrating power, are produced at higher kilovoltages, and form the image on the film.

Long ones don't reach the film in reasonable quantities, and only add onto the radiation the pt gets! Use ALUMINUM discs to "filter" these out.

22

filtration reduces 3 things:

3 types of filtrations:

reduces: pt dose, contrast, film density

1. inherent filtration - incl. OIL around xray tube to dissipate heat, ~0.51 mm aluminum
2. added filtration - added aluminum sheets in cone
3. total filtration = inherent + added

23

recommended total filtration = __ mm aluminum below 50 kVp, and __ mm over 70 kVp

0.5 mm < 50 kVp
2.5 mm > 70 kVp

24

when taking xrays, operator should stand at least __ feet away, and behind a lead shield

and be at __ angle from the beam

6 feet away

90-135 degrees

25

what film provides the most effective way to reduce exposure time, amt of radiation reaching pt and amt of scatter radiation to the dentist?

EKTA-SPEED film

26

standards: 1 year radiation exposure, max. dose = __ REM for someone who works near radiation

__ REM for a non-occupationally exposed person

5 REM (0.1 REM per week)

0.5 REM

27

sequence of radiation injury (3)

1. Latent period - btw exposure and onset of symptoms
2. Period of cell injury - cell death, changes in fxn, abnormal mitosis
3. Recovery period - some cells recover

28

are effects of radiation additive?

YES
damage that remains non-repaired accumulates -> can lead to carcinogenesis -> carcinomas, genetic mutations, leukemias, cataracts

29

the greater/lesser rate of potential for miosis and the more mature/immature the cells are, the MORE susceptible the cells are to radiation

greater mitosis and immature

30

radiosensitive cells incl

small lymphocytes (immature), bone marrow, reproductive cells, immature bone cells

prostate gland, hemopoietic tissue (most sensitive)

31

radioresistant cells incl

mature bone, muscle (most resistant), nerve (pulp)

32

measure of the energy imparted by radiation; traditional unit is called

RAD - radiation absorbed dose

33

what measure is used by the dentist to compare biologic risk effects/estimates of diff types of radiation damage?

equivalent dose "dose equivalent"

34

effective dose measures risk in

humans

35

__ is the traditional unit of radiation exposure measured in air and only applies to __ rays and __ rays

Roentgen (R)

only applies to xrays and gamma rays

36

electromagnetic radiation includes

microwaves, x-rays, visible light, gamma rays

xrays and gamma rays are NON-PARTICULATE radiation energy

37

a sialolith in Wharton's duct is best viewed with which radiograph?

cross-sectional occlusal

38

what xray is designed to dx basilar skull fractures? when you suspect a fracture of the zygomatic arch?

submental-vertical (submentovertex)

gives dx info about the zygoma, zygomatic arches, mandible

source below mandible, film above head

39

the standard radiograph for showing an ANTERIOR view of the paranasal sinuses and mid-face and orbits is?

Water's view

posterior-anterior projection, face against film and xray behind head

dx mid-facial fractures, sinus infxns, lesions of max sinus

40

the best film to visualize CONDYLES and NECK OF MANDIBLE is?

Towne's view

AP projection, pt on back and film under head, xray from front and rotated 30 deg from Frankfort plane, directed at condyles

-assess status of condyles, condylar neck rami because often superimposed by MASTOID and ZYGOMA

41

reverse Towne's view is used to identify fractures of the __ and __

condylar neck
ramus

42

developer solution fxn is to reduce __ crystals to __

silver halide crystals -> black metallic silver

43

xray developing solution has 4 chemicals

1. developing agent (hydroquinone)
2. antioxidant preservative (sodium sulfite)
3. accelerator (sodium carbonate)
4. restrainer (potassium bromide)

as developing solution gets weaker, the films get lighter

44

yellow brown film is caused by

fogged film is from

low solution levels will appear as?

bad fixing (brown) or rinsing

improper film storage, outdated films

developer cut-off (straight clear border) or fixer cut-off (straight black border)

45

xray fixing solution fxn is to

stop development and remove remaining unexposed crystals

time is 2x as long as developing time

46

4 chemicals in fixing solution

1. clearing agent (sodium or ammonium thiosulfate) - removes underdeveloped crystals
2. antioxidant preservative (sodium sulfite)
3. acidifier (acetic acid)
4. hardener (potassium alum)

47

incorrect vertical angulation will cause __ and __

1. foreshortening - excess vertical angulation, teeth appear too short

2. elongation - most common error!

48

general rule for horizontal angulation is the central ray should be __ to the mean antero-posterior plane of teeth being xrayed

perpendicular

49

overlapping interproximal areas are from incorrect ___ angulation

horizontal

50

central ray is 0 if the tube is adjusted so the ray is __ to the floor

positive angulation is when the tube is directed up/down?

negative angulation?

parallel

positive - at floor

negative - at ceiling

51

bisecting angle technique

based on geometric rule of isometry, image on film is equal to length of tooth when central ray is 90 deg to imaginary bisector

52

what is the advantage to the bisecting angle technique?

disadvantage?

decreased exposure time

image might be distorted, SHORT cone so not true img, can't judge correct alveolar bone height

53

paralleling technique

advantages?

disadvantages?

film is placed parallel to long axis of tooth, central ray is perpendicular or at right angles to long axis of tooth and plane of film

no superimposition on max molar view, accurate dx of periodontal bone height, image accurate

requires INCR exposure time (LONG cone), object-film distance needs to be increased

54

cervical burnout is caused by

relatively low x-ray absorption

55

inverse square law is

intensity if inversely proportional to square of the distance from the source

intensity of xray beam depends on distance from the FOCAL SPOT

56

focal spot is

tungsten on the ANOE (target) from which xrays emanate

size of the focal spot influences radiographic DEFINITION

57

the short cone is how big?

long cone?

20 cm (8 in) - exposes more tissue, more divergent beam

41 cm (16 in) - reduces amt of exposed tissue, less divergent beam

58

target film distance (source to film) is determined by?

length of the cone

59

half-value layer (HVL) is the

amt of material required to reduce the intensity of an xray beam to HALF

normally expressed in aluminum or copper thickness

~2 mm aluminum ( 50% of xrays are absorbed by 2 mm aluminum), doubling this thickness doesn't absorb all the xrays but one HALF of the remaining xrays

60

what indicates the QUALITY of an xray beam?

half-value layer (HVL)

61

intensifying screens convert xray energy into?

used for what kind of radiographs?

visible light, so radiation pt receives is decreased

for all extra-oral xrays

62

radiograph operator controls what 3 factors?

1. kilovoltage (kVp) - quality or penetrating power of xray beam that controls speed of ELECTRONS, alters CONTRAST quality

2. milliamperage (mA) - controls # of xrays produced, usually 7-15 mA

3. exposure time

63

# of e- determines what?

QUANTITY of xrays produced, controlled by temperature of tungsten filament

64

how can you increase film density? 4 factors

mA
kVp
time
source-object distance

65

doing what to kVp will cause the xray to have a longer scale of contrast?

how do you increase subject contrast?

INCREASING

decreasing kVp

66

density is the __

it increases as these 3 factors increase, and vice versa

overal DARKNESS of a radiograph

mA, kVp, exposure time

67

image magnification is minimized by using a __ cone

long

68

where is the stream of electrons produced?

what houses the tungsten filament?

electron stream travels from __ to __

filament (tungsten in the CATHODE)

molybdenum cap

from filament (cathode +) to tungsten target (anode -)

69

the anode (-) that stops the stream of electrons is the

part of the tungsten target struck by the e- beam is?

tungsten target

focal spot

70

occult diseases are

small carious lesions, cysts, tumors that present NO clinical signs or symptoms

rare, so xray exam of jaws should not be done to look for it when no signs! (except for caries)

71

mental foramen is seen around what tooth?

root apex of 2nd premolar