radiographic localisation Flashcards
need for radiographic localisation
to determine location of a structure or pathological lesion in relation to other structures
- only needed where clinical examination insufficient to provide answer
- clinical examination must always occur prior to radiographic examination
5 clinical situations for radiographic localisation
position of unerupted teeth
- normal but impacted (cannot meet normal occlusal plane position)/ectopic
- supernumerary (common in upper anterior)
- proximity to important structures (inferior alveolar canal, maxillary sinus, nasal cavity)
location of roots/root canals
- endodontics
- surgery
relationship of pathological lesions
trauma
- dental
- bone fractures
soft tissue swellings - ? tissue/source (could be tooth)
3 stages of using radiograph as information
- Observation - look and see
- Interpretation - listen and think
- Management - patient’s needs, what is there primary concern
use sequentially
how to spot and correct faults or diagnostic puzzles
(3 steps)
- perception
- recognition
- resolution
influenced by knowledge base
what can you observe from this radiograph?
technical acceptabilitly?
abnormalities?
need for more X-rays?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/334/869/708/q_image_thumb.png?1612198409)
- technical acceptability
- Why was it being taken?
- Abnormalities
- Mesial apex radiolucency on 6 – non vital?
- Distal root on 6 – shorter – why? Chronic inflammatory changes causing it to resorb?
- 8 – mesial root is curved – dilaceration – sharp bend
- 8 distoangluar rotated compared to 7
- Supernumerary distal to 3 molar – position transverse to arch
- need for further radiography
- only need to know if the supernumerary needs extract – clinical Q
observe this radiograoh
![](https://s3.amazonaws.com/brainscape-prod/system/cm/334/869/859/q_image_thumb.png?1612198444)
No apices – poor quality radiograpgh
8 is transverse?
how to decide if tooth transverse
2D – lacking knowledge
- Need to view from right angles
- use both together
The “right angle” view
- from lateral and from underneath
crown is lingual of 8
no full length of roots – need more radiographs if extractions
![](https://s3.amazonaws.com/brainscape-prod/system/cm/334/869/909/a_image_thumb.png?1612198510)
options for radiographic viewing at right angles
(3)
- panoramic and lower true occlusal (may need to use PA film as unacceptable for pt for occlusal film distal)
- paralleling periapical and lower true occlusal
- CBCT (cone beam CT) – each of the MPRs is at right angles to the others
methods of radiographic localisation
normally two views required
- views at right angles in their projection geometry
- views with any different projection, provided the difference is known
with the aid of opaque objects (e.g. gutta percha point – sinus involvement, GP in and able to see what apex is causing the problem )
anatomical knowledge crucial
radiographic localisation if views not at right angles
- known projection geometry
- must both include item to be localised and stable reference point (ideally intra oral)
- multiple combinations possible
- utilise horizontal or vertical “tube shift” to aid interpretation
parallax
apparent change in the position of an object caused by a real change in the position of the observer
the objects appear to change their relationship – to each other and to you
- gradation
horizontal and vertical tube shift and the observer
Consider the position of the X-ray tube when each view is taken
- Imagine that you are looking at the patient from that position
Your viewing point is interchangeable with the X-ray tube head position
- BUT for a panoramic radiograph we consider looking from in front of the patient, as if back along the X-ray beam
viewing and beam location
Radiographs normally viewed from the buccal aspect of the patient, therefore:
- beam “passing” from buccal to lingual
- buccal is closest to observer
- lingual/palatal is furthest from observer
parallax mneonic for comparing positon of one structure to another
S same
L lingual
O opposite
B buccal
my PAL comes with me - palatal
sequence of steps in radiographic localisation (4)
- identify direction of tube movement
- ? what do we need to know the location of
- choose a reference
- observe movement of ? in correct direction