Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

3. Radiology > 2.2 - Paralleling Technique > Flashcards

2.2 - Paralleling Technique Flashcards

1
Q

What is the ideal projection geometry in radiology?

A

Image receptor and object parallel

parallel beam of x-rays

x-ray beam perpendicular to object plane and image receptor (tooth and image receptor)

image size identical to object size

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the issues with ideal projection geometry?

A

Image receptor and object are not in contact - tooth is supported by bone so the image receptor can only contact some tooth

Beams of x-rays are not parallel BUT INSTEAD DIVERGENT and as a result image size won’t be identical

X-ray beam central ray may or may not be perpendicular to object plane and image receptor

image and object size are not the same due to magnification caused by divergent beam

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why are the object and image size different?

A

Due to magnification caused by the divergent beam

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What type of x-ray is there no magnification in?

A

CBCT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the solutions to projection geometry problems

A
  1. paralleling technique

2. bisecting angle technique

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the paralleling technique?

A

this is where we must have image receptor and object parallel but not touching

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What technique is the best for taking PAs?

A

paralleling technique as it shows most accurate rep of tooth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

For the tooth and image receptor to be parallel what must they have to be positioned like?

A

Good distance apart

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe the x-ray beam in paralleling technique?

A

This is when the x-ray beam comes in and only the central beam is perpendicular to long axis of tooth and image receptor - outer beams are diverging

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What happens if x-ray beam diverges and we can’t see all f tooth?

A

Then we need to retake x-ray which increases pt dose due to poor technique

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the issue with paralleling technique?

A

In order to have the image receptor and object parallel resulting in the x-ray central beam being perpendicular to long axis of tooth and image receptor they must be some distance apart which creates a potential for undesirable magnification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How do we make up for undesirable magnification caused by paralleling technique?

A

we use a long skin to focus distance to reduce this magnification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is focus to skin distance?

A

The distance between the focal spot of the x-ray tube (where x-rays are produced) marked with a red dot on the intra-oral x-ray head to the skin surface of the patient.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What must the FSD be for paralleling technique?

A

at least 20cm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does a long focus to skin distance her with?

A

It means x-rays on outer part of beam are less divergent resulting in less magnification - MUST BE AT LEAST 20CM as its a regulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How do we measure FSD?

A

From the mark outside of the tube head (usually a red dot which is directly over x-ray source) and measure to pt end of spacer cone to check its at least 20cm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is a rectangular collimator?

A

This is used to decreased amount of radiation dosage a pt is exposed to during an intra oral radiograph

it reduces scatter radiation by focusing beam into same rectangular shape as the sensor or film being used

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What can rectangular collimators also do?

A

They also increase image quality as reduced scatter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What do rectangular collimators and beam aiming devices and film holders combined allow for?

A

reduced dose

improved quality

fewer reject images

inc benefit to pts as dont need several x-rays

20
Q

Where must rectangular collimators be?

A

On all new equipment and retro fitted to old equipment

21
Q

What does the collimator at the back of X-ray tube have?

A

Lead to absorb x-rays

aluminium

22
Q

What is the maximum diameter of circle at pt end of spacer cone?

A

60mm

23
Q

What colour is a red film holder used for?

A

BWs

24
Q

What colour is blue film holder red for?

A

Anteriors

25
Q

What colour is yellow film holder used for?

A

Posterior

26
Q

What colour is green film holder used for?

A

endo to protect endo instruments

27
Q

What parts of film holders are colour coded?

A

BIte block

beam aiming device

rod

28
Q

What is the bite block?

A

rigid area which pt bites down on

29
Q

what is the beam aiming device?

A

locator ring

metal arm

30
Q

What can we do with connecting rod?

A

We can slide beam aiming device so that its closer to pt

31
Q

What does incorrect assembly of film holder resulting in?

A

Coning off which is where the image is in part of the film and other section is completely white

32
Q

How do we know we have set film holder up correctly?

A

If when we look through beam aiming device ring the support for the image receptor is right In the middle - if not then something is wrong

33
Q

What size must a circle collimator be?

A

No greater than 60mm diameter at pt end of spacer cone

34
Q

Why is rectangular collimation better?

A

Same shape as image recpetor

30% reduction in radiation dose

35
Q

How do we set up for taking a PA radiograph?

A

First of where are we taking the radiograph - if anterior then blue and if posterior then yellow

assemble the film holder (remembering that when we look through beam aiming device we should see support for image receptor in middle)

position against teeth of interest

bite block against teeth

place cotton wool on opposite side to stabilise

support the rod and slide ring so its close to but not touching pt

bring beam aiming device close to pt but not touching

ensure in correct orientation to match receptor and spacer cone close to beam aiming device

align tube head and check in 2 diff direction - from the side and below

36
Q

When positioning for a PA what must image receptor be position against?

A

Teeth of interest - parallel to line of arch and long axis of tooth

37
Q

In paralleling techinque what must be parallel?

A

Image receptor and object (tooth) BUT not in contact

image receptor and object must be some distance apart but risk of undesirable magnification so we use a long FSD (at least 20cm) to reduce this

need use of film holders

we stabilise with cotton wool roll between bite block and teeth in opposite arch

38
Q

What are the critical points of bitewings?

A

the image receptor must be parallel to line of arch

the central ray Is at 90 degrees

vertical angle is controlled by film holder but if none then 5-10 degrees

39
Q

What are the sizes of bitewings film holders?

A

size 2

size 0

40
Q

What are size 2 bitewings used for?

A

Adults and are red

41
Q

What are size 0 bitewings used for?

A

small kids and are red

42
Q

How do we take bitewings?

A

first off select film holder and image receptor

then assemble

position against lower teeth parallel to line of arch (distal of 3 to medial of 8)

put bite block in against occlusal surfaces of lower teeth and check its parallel

get pt to bite

bring in beam aiming device

rectangular collimation correctly orientated

spacer cone to beam aiming device and align tube head

43
Q

What is the curve of speed?

A

n anatomic curvature of the occlusal alignment of the teeth, beginning at the tip of the lower incisor, following the buccal cusps of the natural premolars and molars and continuing to the anterior border of the ramus.

happy face

44
Q

What is curve of monson?

A

This is the curve of occlusion in which each cusp and incisal edge touches or conforms to a segment of the surface of a sphere 8 inches in diameter, with its center in the region of the glabella.

45
Q

best way to tell between upper and lower radiographs?

A

In lower can see bone between roots but in upperr can’t see how many roots

3. Radiology (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions