X-RAY POSITIONING OF THE MANDIBLE (2020 UPDATED)

Summary

This educational video script focuses on radiographic positioning of the mandible, emphasizing the challenges due to its superimposed and curved structure. It details various projections, particularly the PA mandible, to visualize fractures clearly without superimposition. The script also discusses alternative views like the OPG, lateral mandible, and axiolateral projections for specific cases, highlighting the importance of proper patient positioning and equipment use for accurate diagnostic imaging.

Takeaways

• 🦷 The video discusses the radiographic positioning of the mandible, emphasizing the challenges due to its superimposition by other structures and curved shape.
• 👨‍⚕️ It is recommended to watch this after understanding the cranial vault, facial bones, and sinuses from previous videos.
• 📚 A PDF presentation is available for further study on pathologies like fractures that can occur in the facial bones and mandible.
• 🔍 The PA (Posteroanterior) mandible projection is the most frequently used technique to visualize fractures without superimposition.
• 🔬 The PA mandible projection requires specific positioning with the orbitometal line and interpupillary line horizontal, and no tube angulation.
• 📏 The positioning for the PA mandible projection aims to elongate the mandible to make fractures more visible and assess displacement.
• 👂 The OPG (Orthopantomogram) is a valuable projection for the mandible but requires specialized equipment not available in all centers.
• 👁️ The Lateral mandible projection is less common due to the difficulty in interpreting superimposed mandibular sides but is useful in certain cases.
• 🦴 Axiolateral projections are used to examine specific areas like the temporomandibular joints (TMJs) when an OPG is not available.
• 🤹‍♂️ Positioning for axiolateral projections requires precise angles and patient positioning to isolate and visualize the area of interest.
• 📐 The Orthopantomogram works by exposing a small area of the image receptor at a time while rotating around the patient to flatten the curved mandible structure.

Q & A

What is the main challenge in performing radiography on the mandible?

The main challenge in performing radiography on the mandible is that it is a curved structure and is superimposed by many other structures, making it difficult to see fractures without any superimposition.

Why is the PA mandible projection frequently utilized in radiographic projections of the mandible?

The PA mandible projection is frequently utilized because its purpose is to elongate the mandible maximally, allowing for the clear visualization of fractures without superimposition, especially those with lateral displacement.

What is the recommended technique for the PA mandible projection according to the video?

The recommended technique for the PA mandible projection involves having the orbitometal line and interpupillary line horizontal, with no tube angulation, and centering in the midsagittal plane at the level of the mid-mandibular angles.

What is the purpose of the lateral mandible projection?

The purpose of the lateral mandible projection is to provide a view of the mandible in a true lateral position, which can be useful when there is a query of a mandibular fracture, despite the superimposition of the two mandibular sides.

How should the patient's head be positioned for a lateral mandible projection?

For a lateral mandible projection, the patient's head should be in a true lateral position with the interpupillary line horizontal, and the central ray should pass through the mid-mandible.

What is an Orthopantomogram (OPG) and how is it beneficial for mandible radiography?

An Orthopantomogram (OPG) is a specialized projection that exposes a small area of the image receptor at a time while rotating around the patient, resulting in a flat representation of the curved mandible structure. It is beneficial as it shows the entirety of the mandible in one structure, which is useful for identifying fractures or other pathologies.

What are some common issues with OPG positioning and how can they be avoided?

Common issues with OPG positioning include improper alignment of the bite plane, patient movement, and interference from broad shoulders. These can be avoided by ensuring the patient's bite plane is in a slight smile position, instructing the patient to stay still, and adjusting the patient's position to prevent shoulder interference.

Why is it important to remove metallic foreign bodies before performing an OPG?

It is important to remove metallic foreign bodies before performing an OPG to prevent artifacts on the image, which can obscure the view of the mandible and other facial structures.

What is the purpose of the axial lateral projection for the temporomandibular joints (TMJs)?

The purpose of the axial lateral projection for the TMJs is to project the target TMJ above the rest of the bones of the base of the skull, allowing for a clear view of the joint, which is particularly useful when querying a disruption to the TMJs.

How can the axial lateral mandible projection help in identifying fractures of the mandibular ramus or angle?

The axial lateral mandible projection helps in identifying fractures of the mandibular ramus or angle by separating the mandibular angles and rami, allowing for a clearer view of the target area, which can be particularly useful when an OPG is not available or suitable.

What supplementary projection is recommended to complement the OPG for a more comprehensive radiographic examination of the mandible?

A supplementary projection such as the PA mandible is recommended to complement the OPG. This allows for the visualization of any displacement of fragments, which may not be clearly seen in the OPG due to superimposition in the midline over the cervical spine.

Outlines

00:00

🦷 Mandible Radiography Techniques and Considerations

This paragraph discusses the complexities of mandible radiography due to its superimposed and curved structure. It emphasizes the importance of the PA mandible projection for identifying fractures without superimposition. The speaker advocates for a specific technique to maximize mandible elongation, including positioning the orbitometal line and interpupillary line horizontally without tube angulation. The focus is on the PA mandible projection's ability to reveal fractures, especially those with lateral displacement, and the importance of knowing surface anatomy for accurate collimation and radiography settings.

05:02

🔍 Lateral Mandibular and Axiolateral Projections for Fracture Assessment

The second paragraph delves into less common lateral mandibular projections and their challenges in clarifying fractures. It describes the positioning for a lateral mandibular projection, requiring a true lateral head position and specific image receptor dimensions. The paragraph also introduces the concept of axial lateral projections, particularly for examining the temporomandibular joints (TMJs), and explains the positioning and angulation required to isolate the TMJ over the parietal bone on the non-affected side. The discussion includes the use of open and closed mouth positions to assess TMJ functionality.

10:02

📐 Axiolateral Mandible Projection for Ramus and Angle Fractures

This section focuses on the axiolateral mandible projection, a technique used to examine potential fractures in the mandibular ramus or angle. The speaker clarifies the objective of this projection, which is to separate the mandibular angles and rami for clearer visualization. The positioning involves a combination of head rotation, head tilt, and tube angulation to achieve a 30-degree cephalad angle. The goal is to have the mandible parallel and close to the image receptor, which may require adjustments such as a small sponge under the patient's neck for comfort and artifact prevention.

15:05

🛠️ Orthopantomogram (OPG) Technique and Positioning

The fourth paragraph outlines the principles and positioning for an orthopantomogram (OPG), a specialized radiographic technique for the mandible. It highlights the importance of patient communication, removal of metallic objects, and the use of a bite piece for proper alignment. The speaker advises on patient positioning to ensure the head is still and the shoulders are relaxed to prevent movement during the OPG's rotational exposure. The paragraph also addresses common positioning errors and their impact on image quality, emphasizing the need for a horizontal orbitometer line and a vertical head position.

20:07

📝 Optimal Bite Plane Alignment in OPG for Mandible Imaging

The focus of this paragraph is on achieving the correct bite plane alignment during an OPG to ensure a sharp and clear image of the mandibular structures. It discusses the ideal curvature of the bite plane, which should resemble a slight smile, and how deviations from this can result in an 'angry mouth' appearance or an exaggerated smile, indicating the chin is too far forward or back, respectively. The speaker provides guidance on adjusting the patient's head position to correct these issues and achieve optimal image quality for dental and mandibular assessment.

25:08

✅ Final Thoughts on Mandible Radiography and Supplementary Projections

In the concluding paragraph, the speaker wraps up the discussion on mandible radiography, emphasizing that while the OPG is a valuable tool for visualizing the entire mandible, it should not replace supplementary projections like the PA mandible for assessing fragment displacement. The speaker acknowledges the midline superimposition over the cervical spine in OPG images and invites questions on cranial vault positioning while encouraging further study of the provided PDF file detailing common pathologies of the cranial vault and facial bones.

Keywords

💡Mandible

The mandible, also known as the lower jawbone, is a crucial facial bone involved in the video's theme of radiography and the study of fractures. It is described as a challenging area for radiography due to its superimposition by other structures and its curved shape. The script discusses various projections, such as the PA mandible projection, to visualize the mandible effectively.

💡Radiography

Radiography is the process of creating images of the internal structures of the body using X-rays. The video script focuses on the radiography of the mandible and facial bones, highlighting the techniques and challenges involved in visualizing fractures and other pathologies.

💡PA Mandible Projection

The PA (Posteroanterior) mandible projection is a specific radiographic technique mentioned in the script that aims to elongate the mandible to identify fractures without superimposition. It is a frequently utilized method for examining the mandible, as it helps in clearly visualizing any fractures or displacements.

💡Orbitometal Line

The orbitometal line is a reference line used in radiographic positioning to ensure proper alignment of the patient's head. In the script, it is mentioned that this line should be horizontal during the PA mandible projection to achieve the correct elongation of the mandible for clear imaging.

💡Interpupillary Line

The interpupillary line refers to the horizontal alignment between the pupils of the eyes, used as a positioning guide in radiography. The script specifies that this line should also be horizontal during certain projections to ensure accurate imaging of the mandible and facial bones.

💡Fracture

A fracture is a break or crack in a bone. The video script discusses fractures in the context of the mandible and facial bones, emphasizing the importance of identifying these injuries through radiographic projections to guide treatment.

💡Orthopantomogram (OPG)

An orthopantomogram is a type of X-ray that provides a panoramic view of the entire mandible and maxillary teeth on a single image. The script mentions the OPG as a valuable projection for the mandible, although it requires specialized equipment and is not available in all imaging centers.

💡Axiolateral Projection

The axiolateral projection is a radiographic technique that introduces an angle to the patient in approximately a lateral position. The script describes its use for examining the temporomandibular joints (TMJs) and specific areas of the mandible, such as the ramus and angle, especially when an OPG is not available.

💡Temporomandibular Joints (TMJs)

The temporomandibular joints are the joints connecting the mandible to the temporal bones of the skull. The script discusses the importance of visualizing these joints in cases of suspected injury or dysfunction, using specific projections like the axiolateral TMJ projection.

💡Lateral Mandible Projection

The lateral mandible projection is a radiographic technique used to view the mandible from the side. The script mentions that while this projection is not frequently used due to the superimposition of structures, it can be valuable when performed correctly to assess certain aspects of the mandible.

💡Superimposition

Superimposition in radiography refers to the overlapping of internal structures on an X-ray image, which can obscure details. The script discusses the challenges of superimposition in imaging the mandible and how different projections can minimize this effect to better visualize fractures and other pathologies.

Highlights

The video discusses the radiographic positioning of the mandible, a complex area due to its superimposition by other structures and curved shape.

After the video, a PDF presentation on facial bone and mandible pathologies, especially fractures, is recommended for further study.

The PA mandible projection is the most frequently used technique to visualize fractures without superimposition.

Proper positioning for the PA mandible projection includes a horizontal orbitometal line and interpupillary line, with no tube angulation.

The PA mandible projection aims to elongate the mandible to make fractures and displacements more visible.

The OPG (Orthopantomogram) is a valuable projection for the mandible but requires specialized equipment.

Lateral mandible projections are less common due to the difficulty in clarifying fractures with overlapping images.

Axiolateral projections can be useful for examining the temporomandibular joints (TMJs) when OPG is not available.

Axiolateral TMJ projections involve a 25-degree angulation to project the TMJ above the base of the skull.

Axiolateral mandible projections are challenging and aim to separate the mandibular angles and rami for clearer fracture visualization.

OPG positioning requires careful patient communication and removal of metallic objects to prevent image artifacts.

The correct bite device is crucial for OPG to ensure the teeth are in the same plane for a sharper image.

Proper patient positioning in OPG is key to capturing the entire mandible in focus, including maintaining a horizontal orbitometer line.

The bite plane in an OPG should resemble a slight smile, indicating correct patient positioning.

Supplementary projections like the PA mandible are necessary alongside OPG to show fragment displacements.

The midline of the OPG is often superimposed over the cervical spine, which can compromise image quality in that area.

Transcripts

this video covers the positioning of the

mandible

it should be watched after having first

viewed the

three preceding videos which looked at

the cranial vault

the facial bones and the sinuses

after this video there is a pdf

presentation which describes

some of the pathologies particularly

fractures

which can readily occur within the

facial bones and mandible and i

encourage you to have a look at that

non-narrated presentation

the mandible is a potentially

challenging area

to perform radiography on

because it's superimposed by many other

structures

and it's a curved structure it can be

very challenging to

to see fractures of this region

as such there are some projections which

can be utilized on the mandible

but probably the only one which is

utilized very frequently

is the pa mandible amongst the plane

radiographic projections

the pa mandible projection can be

undertaken a number of different ways

essentially the purpose of this

projection is to be able to

elongate the mandible maximally

so that any fractures can be seen

without any superimposition

and any fractures which have a

displacement media laterally can be seen

readily as such while there are a number

of different ways to

perform this projection the technique

which i advocate for you

here should have the best chance of

being able to show any fractures

for the pa mandible projection the

common information is that the

orbitometal line

should be horizontal that is that the

uh forehead is tucked in so the

patient's nose and forehead is against

the

image receptor and the interpupillary

line should be horizontal

when we undertake those two things you

can see that the primary beam should be

able to elongate that mandibular

structure

i do not advocate a tube angulation for

mandibular projections

now the intention of this projection is

to have the divergent ray

cutting through the mandibular angle and

elongating the entirety of the mandible

that is the

intention here

so a pa mandible projection requires for

the orbitometer line to be horizontal

and the interpupillary line to be

horizontal

there should be no tube angulation and

the centering point should be

in the midsagittal plane at the level of

the mid

mandibular angles the head is positioned

such that the patient's nose and

forehead is against the image

you should collimate superiorly to

include the entirety of the external

order trimiatus which is the patient's

earhole level and all the way down to

the patient's mental synthesis and both

of those

surface anatomy structures should be

well known to you

when you perform this projection which

is on a 24 by 30 portrait with about 75

kbp

you should end up with a projection

which looks like this

now as you can see if the mandible has

been elongated

and if there is a fracture hopefully

there won't be any superimposition of

the proximal and distal fragment

sections

over each other so you should be able to

see that fracture

we should be able to see almost all of

the mandible certainly the superior most

parts of the temporomandibular joints

are going to be superimposed by the

lower part of the facial bones and the

the temporal constructs

and certainly the medial aspect that is

the midline

mental symphysis aspect is going to be

superimposed over the cervical spine

however we should be able to see the

entire mandible

even with some superimposition

assuming that the mandible is a

symmetrical structure and it can be

displaced somewhat by fracture

we should be able to see that mandible

as a fairly symmetrical structure

so we've performed our pa mandible

the next views that you do really depend

upon the facilities available to your

particular

imaging center the opg

or orthopantomogram is a very good

projection for the mandible but it

requires specialized equipment and not

all centers have access to it

as such it's important to be able to

describe some of the other

projections as well

the lateral mandible tends to be

undertaken

reasonably infrequently when a patient

has

got a queried mandibular fracture

superimposing

the two mandibular sides over each other

doesn't really clarify the situation if

anything it probably makes it a little

bit more challenging

however to perform a lateral mandible

projection

requires for the head to be in a true

lateral position and as i've discussed

in previous videos

having the patient positioned in

approximately a 45 degree

rotation of their thorax such that then

their head is turned in a true lateral

position

is the best way to position these the

interpupillary

line should be a horizontal structure

and the central ray passes through the

mid

mandible and by mid mandible what i mean

is essentially a point halfway between

the

mental symphysis and the external

auditory meatus

that lateral mandibular projection

should have

a 24 by 30 landscape or

portrait image receptor it doesn't

really matter too much but i tend to go

with landscape

and it really does require for the

patient to really have that sort of once

again that shoulder and neck and close

to the image receptor

when performed well it should look

something like this and you can see that

there is almost complete superimposition

of structures such as the mandibular

angle and

mandibular rami the mandibular condyles

and the petrous temporal bones

aren't perfectly superimposed because

they are a more peripheral structure

on this image lateral mandible

and or lateral facial bones can be

undertaken with a special

form of lateral imaging of the facial

bones called lateral cephalometry

which basically uh puts the patient's

head

into a clamp-like device

which means that the patient will be in

a true lateral position

but it can be performed quite readily

just with standard radiographic

positioning

so we should have superimposition of

bilateral structures we should see the

entirety of the mandible and it should

be very close to a true lateral

projection

if you do not have access to an opg

but there is a query or suspicion

of a fracture around the mandibular

ramus

and angle then the axiolatural

projections can be useful

the first axiolateral projection i'd

like to talk about is for the

tmjs

and an axio lateral projection is

essentially

one which introduces an angle to a

patient

in approximately a lateral position

if you wanted to have a look at the

patient's temporomandibular joints an

opg or lateral cephalometry is the ideal

projection

however without having access to those

if you wanted to see whether or not the

patient had a disruption

to their temporomandibular joints or

tmj's

then the axiolateral projection is what

you do

starting off with the patient in a true

lateral position

what you're going to do is instead of

having the central rod be a horizontal

structure

you are going to introduce an angulation

such that the central ray passes through

the tmj

closest to the image receptor now often

what this means

is first of all having a practice run

sitting

or standing the patient against the

erect bucky and then assessing

the level of their temporomandibular

joints their ear hole

level so that you can ensure that your

image receptor is at the correct level

then

introducing about a 25 degree coordinate

angulation

such that it strikes the image receptor

at that height

then bring the patient back in and

position them in a true lateral position

and you should end up with the

superimposition of the target

temporomandibular joint over the

parietal bone

on the non-affected side

so hopefully that smooth plate like bone

of

for example in this image the patient's

left parietal bone will be superimposed

over the tmj and you should see that

target tmj

quite well so

the axial electrical tmj projection is a

true lateral

with the affected side touching the

image receptor but a 25 degree cord out

angulation

hitting that target tmj passing through

the parietal bone on the other side

depending upon the queried pathology

it might be performed with the patient's

mouth open or closed

or still or an open

and closed series if you were querying

something such as

a temporomandibular joint dislocation or

subluxation

this patient is having a

axiolateral tmj projection with an open

mouth this photograph shows a tube

angulation of 30 degrees i don't think

30 degrees is necessary 20 to 25

should be all you require because all

you're really trying to do

is to project that temporary

temporomandibular joint above the rest

of the bones of the base of the skull so

30 degrees is a bit too much there

and we should end up with something like

this hopefully you can see the

socket there of the temporomandibular

fossa and hopefully you can see the

mandibular condyle

now in this projection these two

projections we have both

a closed and an open projection when the

patient's mouth is

open or when your mouth is open your

mandible moves

inferiorly and anteriorly such that that

condyle will then move against that

process just anterior to the

temporomandibular fossa

an axiolateral tmj projection is

commonly very commonly performed

bilaterally and so you may end up doing

open and closed left open and closed

right to be able to show that tmj

functionality

the axiolateral mandible is probably one

of the most difficult projections to

describe

rather than go straight into the

positioning of this projection

i'd instead like to tell you the

objective and that will hopefully

clarify

why we are doing this projection and how

we do it

the image in front of you shows a young

lady who is

having some x-rays done of her mandible

perhaps she's not a suitable candidate

for an opg or perhaps we don't have

access to an opg machine

but we have a query of a possible

fracture of the

mandibular ramus or angle

for that reason axiolateral mandible

projections can be performed

now these can be performed with the

patient supine as was the way this

photograph was originally taken

or erect and that's the way that i've

actually just rotated this

photograph

now in this photograph

we have the patient's right side being

closest to the image receptor

and we are imaging the right hand side

the purpose of this projection this

photograph in front of you

is to try to get the majority

of the right side of the patient's

mandible

in contact with the image receptor and

parallel with the image receptor

it's not a true lateral projection you

can see that we have got a

cephalad angulation the purpose of that

cephalad angulation

is to project the patient's left

mandibular ramus and angle superiorly

and out of the way

the right side is the area of interest

on this

projection now you'll notice that i have

not

stated a particular tube angulation at

this point

the purpose of this projection is to

separate the mandibular

angles and rami to achieve that

we have an approximately 30 degree

cephalad angulation

that 30 degree cephalad angulation

can be achieved by a 30 degree

tube angulation a 30 degree

tilting of the head to the side

or any combination of those two angles

to create the sum of 30 degrees

so i will be describing this as though

the patient's head is tilted

15 degrees on this side and with a 15

degree tube angulation

but the important message is this tube

angulation

plus head tilt equals 30 degrees

there is an additional positioning

rotation to the scribe as well

but if you are mindful of the fact that

this mandible

the right hand side of this patient's

mandible needs to be parallel to

and closely as close as possible to in

contact with the image receptor

will be able to understand this

projection

we start off with the patient in

approximately a lateral position

we then have the patient

turn their head

toward the image receptor

so the patient if you were to have a

look at the patient's eyes they are not

looking

straight ahead but rather their head has

been turned

15 degrees toward that image receptor

if you were to feel your own mandible

now you could obviously feel that it

starts out as a broad structure near

your ears

and tapers into the midline by turning

the head towards one side

we bring the majority of that mandibular

structure

parallel with the long axis or parallel

with a plane of the film

after we have rotated the head we also

then

tilt the head such that

it plus the tube angulation

equals 30 degrees so i've mentioned 15

degrees there

however it is part of your total

angulation

often having a small sponge underneath

the patient's

neck and mandible may assist so long as

it's not going to cause an artefact

so the head is turned into the image

receptor

and the mandible is slightly away

from the image receptor but the forehead

is tilted

closer in that will separate

the left and right mandibular rami

so 15 degree head

rotation 15 degree head

tilt 15 degree tube angulation

but functionally the head tilt and

angulation

equals 30 degrees

now if you're able to achieve that this

is what you should end up with

a position where the patient is off

lateral that is that their head is not

in a true lateral position it's 15

degrees turned into the erect bucky or

table bucky

and it is also angulated such that the

top of the head is closer in towards the

film the forehead is closer

so the interpupillary line will be on a

15 degree angle is another way of

considering it

the tube angulation plus that head tilt

equals 30 degrees the centering point is

going to be

in the target mandibular body so the

central ray is going to pass

essentially just anterior to the

mandibular angle

and at the midpoint between those two

mandibular

angles

it can be done erect or supine and you

can see that this is one way of

performing the projection it does

distort the image a little touch so i

would prefer to have the image receptor

be flat

but it's not a bad way of positioning it

this is what you should end up with it's

actually a very very pretty

projection once it's performed well you

can see on this particular projection

that the entirety of the patient's

mandibular condyle

angle ramus and body almost all the way

up to the mental symphysis can be

projected

clear of any of the rest of the skull

and the rest

of the mandible the the target side is

showing well but the non-target side's

projected way off the top of the image

you will get some superimposition over

hyoid bones and things like that that's

very very normal

and so in terms of the criteria we

should show the mandibular condyles off

the cervical spine so we can see that

condyle

and that that target region the affected

side of body

ramus mandible can be seen maximally

once we get into the curvature of the

patient's mental synthesis we

will the anatomy will be distorted of

course

we'll perform this projection

bilaterally to show

both sides because we are going to be

very likely to have multiple fractures

over the mandible

and now the orthopedimogram

the principle of an orthopantomogram

is to only expose a small

area of the image receptor at one

particular time

and that over that exposure and as we

expose segment by segment of the image

receptor

the entirety of the x-ray tube and image

receptor

rotate around the patient subsequently

we should end up with a curved structure

of the mandible

being shown as a flat structure across

the plane of the image receptor

opg positioning is something which is

frequently done quite

poorly there are a number of things that

i'd like you to be aware of

first of all communicate with your

patient try to get all metallic foreign

bodies out of the way

earrings nose piercings other facial

piercings false teeth things like that

should be

taken out of the possibility of causing

an artifact on the image in front of you

there you can see

in that photograph that the model is

biting onto a small piece of plastic

that is essentially between her teeth

this is the most correct byte device to

use

if you have been on placement and have

seen an opg you may have seen some which

have got this byte device

some which use like a tray that the

mandible slides into or probably both

and for most machines it's an

interchangeable thing

ideally you should wherever possible

utilize the bite

piece it will have a groove in the top

and bottom to allow for the top and

bottom teeth to be in the

same plane and so you're going to end up

with a sharper image of the teeth

in addition while it is less fun to bite

on something to just rest your chin

in a slot it will have a

better image quality and it does mean

that the patient's less likely to

turn their head which is the case when

you use the tray

the patient is placed in the opg machine

after you've removed all of the

foreign bodies and things like that

communicate well with your patient and

let them know that the machine is going

to take

10 seconds it's going to make noise and

most particularly

and this is very very important for

broader shoulder patients

let them know that if the machine

brushes up against their shoulders that

they are to try to stay as still as they

can and to let it move around

them

the patient will bite onto the bite

piece or as necessary slide their

chin into that mandibular tray and a

rest is going to be placed against the

forehead

and possibly some clamps against the

side of the head as you can see in this

photograph

with the intent of keeping the head

absolutely still

the orbitometer line should be

horizontal

and so this photograph the chin has

tilted up a little bit too far i would

have liked to have seen

the chin down a little touch more

the patient's shoulders should be

relaxed now

in this particular photograph this model

is is a slim

shouldered lady however one of the

things that you can do

is to wrap your arms underneath

that bar that you can see in front of

the patient

and so the left hand holds on to the

right

bar and vice versa that will then bring

the shoulders

anteriorly and medially and that should

allow

for the tube to move around the patient

with a little bit more comfort and less

safety issues the head should be

vertical the vertical line should be

running straight down their face

and these opgs can be performed in a

with a patient in a chair and that's

fine particularly if you've had a

patient who's had an assault or

something like that

and you want to make sure that they're

not a fainting risk but really you

should be assessing your patient for

their

ability to comply if you use a chair

do not use a rotating chair because if

the tube hits the patient's shoulders

that rotating chair is just going to

rotate the patient around as well

okay so use a chair with fixed legs

tell that patient to stay nice and still

not to turn their head

and what you should end up with is a

nice

gentle opg

now when performed well the the standard

positioning doesn't really apply for the

opg because

you can't change the angle it's an image

receptor specialized for the purpose or

indeed a dr

opg machine and the central ray of

course well it's going to go all the way

around that patient so it's going to be

at approximately the level of the

the mid mandible you should have that

interpupillary line horizontal though

the mirror in front of the patient

should have

lines etched into it to enable you to

know if the patient's in a true

interpupillary line being horizontal

position

when the projection has been performed

and the

orbit hermeator line is horizontal you

should end up with the image that you

can see in the middle of the screen

there

if the patient's chin is too far forward

or the head has been tilted too far back

you're going to end up with a much more

easily performed opg because the head's

up nice and high

but it's not going to get the majority

of those facial bones

structures those mandibular structures

in the same plane so it's going to be

out of focus

similarly if you have got the chin too

far back the forehead too far

forward you're once again going to

project

structures outside of that plane of

focus

and so once again you're not going to be

able to see good detail of all of the

teeth and mandibular structures

so when an opg has been performed

well the patients bite plane

that is the alignment of their upper and

lower teeth

should be in a slight smile and the

image in front of you

in the middle of screen represents the

ideal curvature of the bite plane

if you've got a flat bite plane like the

image on the top of the screen

that looks like they've got an angry

mouth you've got the chin too far

forward you need to bring the forehead

more forward

and conversely if you've got that very

very exaggerated huge

smile that you can see down the bottom

the chin is too far back you really need

to bring that

chin forehead chin forward and forehead

back

the opg is one which really does require

a fair amount of compliance but it is a

very very good projection for being able

to show the entirety of the mandible as

one structure

it is not the be all and end-all of

radiography the mandible you still do

need a supplementary projection

such as the pa mandible a complementary

projection i should say

so as to be able to show any

displacement of fragments

the opg always suffers from the fact

that in the midline it's going to be

superimposed over the c-spine so you may

have some compromised image quality

there

if you have any questions about any of

the positioning of the cranial vault

please do jump onto discussion board

otherwise i encourage you to have a look

at the final pdf file which outlines

the common pathologies of the cranial

vault

and facial bones and good luck with your

studies