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Flashcards in Exam 3 Deck (59):
1

what makes panoramics unacceptable for detection of caries and subtle periodontal bone defects

the unsharpness of the image

2

what makes panoramics unacceptable for measuring distance

Distortion

3

what head position is correct for panoramic images

patients head should be facing straight forward,
occlusal plane should be tilted slightly Downward
Neck should be extended
patients Tongue should be placed against roof of moutth

4

Describe the series of lights new panoramics use to align patients

Midline light: prevents head rotation
Vertical light: ensure proper anterior-posterior position of teeth
Horizontal light: ensure proper occlusal tilt-(_Frankfort plane parallel to floor

5

What will happen if patients head is twisted or rotated during panoramic imaging .

Teeth ramus and adjacent structures will be distorted horizontally
too narrow on side turned away, too wide on other side
especially anterior teeth

6

What will be the results of the panoramic image if patients head is too far back ?

Bc teeth and jaws are bejind the image layer so horizontal magnification will be greater

teeth will appear wide and blurry especially prominent in anterior parts of the jaw

TMJ not seen bc behind edges of film.

7

What will be the Pano result i patient head is too far forward?

teeth and jaws are in front of the image layer, so horizontal magnification will be smaller

teeth will appear narrow and blurry, especially in the anterior parts of the jaw

cervical vertebrae often appear at sides of films since head is so far forward

8

If patients chin is too high during panoramic imaging then....

image of hard palate often superimposed on roots of maxillary anterior teeth

TMJ sometimes not seen since they are behind the edges of the film

9

If patients chin is too low during panoramic imaging...

bc mandibular teeth are behind image layer, they look wide and blurry while maxillary anterior teeth are relatively non distorted
* Anterior teeth moved down, posterior teeth moved up, so occlusal olane as an accentuated "smiling" appearance

+ overlap of teeth especially prominent an
- image of cervical vertebrae often appear at edge of film because they move forward when head is tipped down

10

if patients tongue is improperly positioned during panoramic image

if tongue not on palate we will see Air Space as a broad radiolucent band across the maxilla

11

If patients head is slumped forward during panoramic image

cervical verterbrea moved forward enough to make radiopacity in middle of film

12

What is velocity of a wave

wavelength x frequency

13

True or false: Velocity is the same for all forms of electromagnetic energy

True
all travel at c = the speed of ligt

14

what does the term photon refer to

energy carried by radiation

15

what are the wavelengths of x rays

0.01nm-0.05nm

16

what is the wavelength of visible light

300 - 800 nano meters

17

Frequency is

Number of wavelegnths

18

What is Ionizing radiation

radiation with enough energy to ionize or cause biological change

19

True or false : x rays have mass and charge

False

NO ENERGY has MASS
and it doesnt have charge bc it would be extra dangerous

20

X ray filament have vacuum glass tube with anode filament and cathode target

False

It has a Cathode filament and anode target

(anode is AT target A= anode T= target

21

what happens when electrons collide with target?

It converts kinetic energy to electromagnetic energy

22

what is filament made of and what does it do?

made of thin tungsten wire
when heated y current it boils off electrons in a process call Thermionic emmission

23

What is the cloud of electrons around filament called

Space charge

24

Where is the positive and negative charge on a xray

Anode taget cathode filament

25

when xrays are produced where are they emitted from?

Filament

26

what is made of malybdenum?

Focusing cup

27

what is the focal spot?

the point on anode target where electrons in tube target was focused

28

How much of the x rays actually produce image

1%

29

what ae the 2 mechanism of x ray production

Brehmstrahlung radiation
Characteristic radiation

30

what is Milliamperes(MA

qualtity of electrons moving across the tube from the cathode filament to the anode target produced by tube current

31

tube current produces

millamperages

32

which shell is closest to nucleus

K shell

33

Brehsstrahlung radiation

Responsible for 90-85 % of x rays
Poly energetic
Produced when electrons slow down near nucleus
responds to changes in Kv

34

Characteristic Radiation

When energy directly hits K shell and a electron is knocked out and element reaches characteristically too fill void - this radiation differs by element

35

exposure time is measured in

Impulse, seconds or number of xray

36

Long exposure time

more electrons
more xrays , darker image

37

impulses=

second x 60 ( always 1 or more)

38

seconds=

Impulse/60

39

which photons are undesirable & why?

low energy photons, bc it leads to biological damage

40

What does filtration do?

Absorb the low energy photons

41

How is filtration measured

mm Al- amount need to penetrate aluminum

42

Inherent Filtration

without a added filter it has .5-2.0 mm Al

43

What are the added filtration requirements for units operating at 70Kvp or Lower

1.5 mm Al

44

what are the added filtration requirements for units operating at higher than 70 Kvp

2.5 mm Al

45

True or false : Filtration increases average energy of xray photons in primary beam and increase number of photons

First part true second half false

Filtration increases energy but DECREASES NUMBER of PHOTONS

46

Energy or quality of photons increases with

Increased Kvp and Filtration

47

Number or quantity increases with

Increased mA
Increased Exposure time
Increased Kvp

48

Which PID shape reduces radiation dose

Rectangular- It reduces it by 65% compared to round

49

which PID length radiation dosage by how much

35% 16" compared to 8"

50

Inverse square law

1/d^2 =Impulse
short PID needs shorter time
long PID needs long exposure
(new exp time/ old)= ( new PID length)^2/old ^2

51

5) The area of image sharpness between the x-ray source and film that will be imaged on the panoramic is called

Image Layer

52

the following affect film speed

Emulsion thickness
crystal size
Film Packet size

53

The purpose of the developing step in film processing is to

To reduce silver halide crystals into metalic silver

54

The latent image in film base radiography consist of an accumulation of

-Neutral metallic silver at the Latent Image Site

55

The most appropriate extra-oral radiograph technique for imaging the paranasal sinuses (maxillary, frontal, ethmoid) is

Water View

56

The most common extra-oral radiographic technique used in dentistry is

Lateral cyphalometric projection

57

The primary and singular function of a collimator is to

reduce scatter

58

44) Sella turcica i.e pituitary fossa is clearly identified (without superimposition) in which of the following extra oral x-ray

Lateral Skull projection

59

where are ghost images formed

betwee xray source and effective center of rotation