Extra oral radiography

Question 1

direction of beam - lateral

Answer 1

aimed at side of head

Question 2

direction of beam - postero-anterior

Answer 2

starts posteriorly and passes anteriorly

Question 3

true - angulation of beam

Answer 3

perpendicular to head

Question 4

oblique - angulation of beam

Answer 4

not perpendicular to head

Question 5

occipitomental

Answer 5

through occiput then mental region

Question 6

mid sagittal plane

Answer 6

down middle of face

Question 7

orbitomeatal line

Answer 7

10 degrees difference to frankfurt plane
connects outer canthus (lateral edge) of eye with centre of external acoustic meatus

Question 8

cephalostat

Answer 8

ensures standardised positioning of equipment and patients head when taking a cephalogram
holds head at correct angle, stabilises head to prevent movement and establishes correct distance between patient , receptor and x ray source
uses ear rods and forehead support

Question 9

how far should receptor be from focal spot in lateral cephalograms

Answer 9

1.5 - 1.8m to minimise magnification and diversion effects of beam

Question 10

what piece of protective equipment is worn by the patient during a lateral cephalogram

Answer 10

thyroid collar - made of lead

Question 11

what are the two options for making soft tissues more visible on a lateral cephalogram

Answer 11

using software to enhance soft tissues after exposure
placing an aluminium wedge in the filter to attenuate the area of beam exposing soft tissues

Question 12

oblique lateral radiographs what are they and when would they be taken

Answer 12

extra oral radiograph taken from around the area of angle
provides view of posterior jaws without superimposition of contralateral side
Rarely used nowadays as OPT preferred but may be used if pt cant tolerate intra oral x rays or cant stay still for an opt

Question 13

parallax

Answer 13

apparent change in the position of an object due to a real change in the position of the observer

Question 14

Horizontal tube shift

Answer 14

method of radiographic localisation
uses two equivalent views e.g 2 bitewings or 2 periapicals

Question 15

Vertical tube shift

Answer 15

method of radiographic localisation
uses two different views e.g panoramic and oblique occlusal

Question 16

SLOB

Answer 16

same lingual, opposite buccal
if object of interest moves the same way as the x ray tubehead then it is lingual
used during radiographic localisation

Question 17

ALARP

Answer 17

as low as reasonably practical

Question 18

what should a practices quality assurance programme cover and include

Answer 18

staff training, risk assessments, image processing

Question 19

how often should digital receptors be formally checked

Answer 19

at least every 3 months

Question 20

what 3 checks should be carried out on digital receptors

Answer 20

receptor itself - is it clean , any visible damage
image uniformity - expose receptor to unattenuated x ray beam and check if image is a uniform shade of grey
image quality - take radiograph of test object and compare to what ideal image should be

Question 21

what is meant by delamination in regards to digital receptors

Answer 21

phosphor layer begins to peel away from the edges of phosphor plated digital receptors

Question 22

are scratches and cracks more common on solid state or phosphor plate receptors

Answer 22

phosphor plate
delamination can also occur

Question 23

what colour will damage to receptors show as on digital and film radiograph images

Answer 23

digital - white
film - black

Question 24

what is a common test object for image quality

Answer 24

step wedge - wooden stick with varying thickness of lead foil - must be able to differentiate clearly the different ‘steps’

Question 25

what is a collimation error also known as

Answer 25

cone cutting error

Question 26

what is fault analysis

Answer 26

identifying and explaining faults so they can be redeemed