Imaging Techniques

Question 1

which of these shows 2-3 teeth from crown to apex and surrounding apical tissue

Answer 1

periapical

Question 2

which of these shows crowns of upper and lower premolars and first and second molars on one film

Answer 2

bitewing

Question 3

how to tell the difference between periapicals and bitewing x rays when taking them

Answer 3

periapical x ray beam shoots on one side of bite block (so bite block does not sit flat in mouth)
bitewing bite block in middle or x ray film (so looks flat in the mouth)

Question 4

when may vertical bitewing be used? disadvantages too

Answer 4

perio- to see bone level

BUT see less teeth

Question 5

describe occlusal x rays and when they may be used

Answer 5

show larger area (whole upper/ lower dentition)

useful for anterior teeth

Question 6

with which intraoral technique is thyroid guard used and why

Answer 6

occlusal

x ray shot from above (at near angle of nose) so may hit thyroid gland which is v radiosensitive

Question 7

list 5 extra oral radiographic techniques

Answer 7

1. panoramic
2. lateral cephalometric
3. oblique lateral
4. postero-anterior mandible
5. occipito-mental (OM)

Question 8

other names for panoramic

Answer 8

DPT (dental panoramic

OPG (orthopantomograph, machine used for x ray)

Question 9

when may a lateral cephalometric radiograph be used? why

Answer 9

in ortho/ orthosurgery

shows relationship of upper and lower arches and soft tissue outline

Question 10

when may an oblique lateral x ray be used and why

Answer 10

children- too small to fit bite block in mouth

people with disabilities- cannot tolerate bite block in mouth

Question 11

how to take oblique lateral

Answer 11

side of interest placed against image receptor, face turned towards it

Question 12

how to take poster-anterior mandible and what you see

Answer 12

patients chin down –> occipital bone lifts –> can see mandible and lower facial features

Question 13

how to take occipito-mental (OM) radiograph and what you see

Answer 13

chin up –> occipital bone down –> can see facial bones and zygomatic arches

Question 14

explain how cone beam computed tomography works

Answer 14

cone-shaped beam of x rays rotates around patient to create image

Question 15

what is cone beam CT useful for?

Answer 15

hard tissue

Question 16

what are CT scans useful for?

Answer 16

hard tissue (and soft tissue)

Question 17

how do CT scans work?

Answer 17

x ray source and detectors move around pt (pt laid down) producing series of axial images. 3D reconstruction avoids superimposition

Question 18

how does ultrasound work?

Answer 18

probe gives off high frequency sound waves
sound waves reflected back at interfaces between tissues
reflection picked up by probe which produces the image

Question 19

when are ultrasounds used in dentistry 3

Answer 19

salivary glands
thyroid gland
neck lumps

Question 20

why is jelly used with ultrasounds

Answer 20

sound waves do not travel well through air

Question 21

how does MRI work

Answer 21

strong magnetic field lines up protons in hydrogen atoms
short bursts of radio waves knock protons out of alignment
as protons realign with their magnetic field their rotation induces electrical signal in receiving coil –> can distinguish between various types of tissue
produces images in multiple planes

Question 22

how to take MRI

Answer 22

pt positioned within magnet

receiving coil positioned close to magnet

Question 23

problems with MRI

Answer 23

claustrophobia
noisy
expensive –> not many machines, long waiting time

Question 24

what radiographic technique shows functioning? explain how it works

Answer 24

radionuclide imaging
pharmaceutical label attached to radio-isotope
put in to pt
go to intended organ in body (eg thyroid gland)
radioactive part emits gamma rays
gamma rays detected by gamma camera

Question 25

what other type of radiography uses gamma rays

Answer 25

bone scintigraphy scan

Question 26

what radiographic techniques do not use ionising radiation

Answer 26

ultrasound
MRI
**radionuclide, bone scintigraphy??

Question 27

3 types of intra-oral radiographic techniques

Answer 27

periapicals
bitewings
occlusals