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Transcribed by Rahul Kallianpur Date of the Lecture 8/8/14

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[Radiology] [Panoramic, Extraoral, and TMJ] [Review] by [Friedman]

[Slide number 4] (Panoramic Radiography][Friedman] Can I have your attention please? Sorry the microphone isnt working.Sorry for the mix-up. On the syllabus its listed as 11 oclock so thats why I had no

idea. So what Im going to do to make up for that Im going to give you a much betterreview. Well make up for it. Ok, alright.Well do the best we can. Youve had somematerial on panoramic radiography with Dr. Chan she went over some of thelandmarks in different types of machines. Im going to cover panoramic radiographymore from a clinical standpoint. Things that youll be doing in the clinic. I dont wantto get into too much detail on how the machine actually works because youre notgoing to be engineers so forget about all the kvps and all that.

So what were going to talk about very quickly panoramic radiography wasintroduced to dentistry in 1959. There are two techniques currently available or thepatient can stand. IF I stress something or say it a couple of times please listenbecause I stress that. The way panoramic radiology works is theres a little slit that

the x-rays come out of. The x-rays come out of a little slit, it turns around thepatientshead the source of radiation goes in the opposite direction as the film. Okso well see examples of that. What is tomography? Tomography is how a panoramicmachine works how the filaments taken. Its radiograph in one plane of the objectwhile eliminating or blurring structures in the other plane. Now, weve heard thatwhen you take a PA or intraoral film if theresany movement the picture will comeout blurred. So how is it possible that we get a clear picture without a blurring of theimage? Well we know that the source of radiation is moving and the film is alsomoving in the opposite direction. The way that works is the process calledtomography. The best way I can explain that to you is if you have a pen and youmove the pen one part of the pen is moving up and one part of the pen is moving

down. Theresa certain point on the pen called the fulcrum or focal trough wherethereszero motion. So what happens is when we do tomography we have thepatient in the proper focal trough set by the manufacturer. If theyre in that plane,and well show you that, everything around them is going to be blurredexcept whatis in the focal trough as it goes around radiation hits and everything in the focaltrough will be sharp. Thats the second molar then it goes a little more to the firstmolar. So thats a little about tomography process and another name for panoramicimage is a pan tomograph. Well see examples of that. So far I havent repeatedanything twice. (laughter)

(Slide Number 5) (Slit Beam Collimator)

So this is the split beam here the x-rays come of here notice the patient is inthe machine, hesgot something on his head. That is to prevent the patient frommoving. We dont want the patient moving, we have movement of the source ofradiation, the slit beam and the film. Well seeexamples of that. But we want thepatient stationary. IF the patients moves, if the patient tilts their head, if the patientschin is down, if it is up thats how you will get errors in panoramic imaging. Thepatient must be positioned properly. Well go over those requirements. Also noticethe patient biting on a bite block in a little notch. The manufacturer tells us if the

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patient is biting in that notch then he is in the proper image layer focal trough. It is acurved zone where there is no blurring and everything will come out sharp. IF thepatient isnt biting on the notch, if theyreforward or behind the notch then we willsee blurring of the image. Most of the errors on panoramic imaging have to do withthe placement of the patients head. If theyre not in the proper positioning, if their

head is tilted, then there will be an error. Because then the patient is not in the focaltrough or image layer. Focal trough image layer. Ok so (laughter). Well seeexamples of that.

Slide Number 6 Panoramic RadiographyTomo, tomo-meaning sections. Going through sections. Another name for pan

in some textbooks is a laminogram which is layers. Because thats going through aslit beam thats coming through a little opening and going around the patients headas the film moves in the opposite direction. Tomogram, x-ray and source move inopposite direction, as the patient remains stationary. Focal trough is the plane of anobject that is seen clearly. Another name is plane of acceptable detail or image layer.

Thats an imaginary area set by the manufacturer. If the patient is in that positionyou will be able to see the teeth sharply and clearly and no blurring or disruptionswill be seen. Anything out of that area is blurred out and as it goes around we endup with a final image. I have a soar throat and I dont know how to work this thing.The other one is on? (turns on microphone angry IT man mumbling). My syllabussays 11 oclock. I was doing a sinus lift and I had blood all over me and they calledme in here and no I wasnt doing that I was looking at some radiographs.Anyways..

Slide Number 7 Panoramic RadiographyThese are some of the features we spoke about that you dont need to get

involved with but those thatre interested you can. Some machineshave a fixed focaltrough. Which means youllhave difficulty with large patient vs. small patientbecause they wont fit in the focal trough. And they could be errors based on that.Some more expensive machines you can adjust the trough for the size of the patient.These are the ways that you can adjust the focal trough in the machine. Thepanoramic radiograph uses curved surfaced tomography which means your taking acurved area of the head and turning it into a flat surface. So you know there will be acertain amount of distortion in the had just knowing the fact that you have a roundhead and you are making it into a flat surface. Its like one of those maps of the worldwhere they open it up and Greenland looks gigantic. One of those maps because ofthe changing from a round globe to flat surface.

Slide number 8 principle of tomographyBut notice the principle of tomography is that the source of the radiation is

moving in this direction and the film is moving in the opposite direction. So we havethis reciprocal movement. And anything in the focal trough. This is the focal troughon this one, this is actually a medical tomography. Notice that anything in the focaltrough will appear in the same position in all the image. In the center, in the center,in the center and it will not be blurred. All the other areas will be blurred. Anything

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out of the focal trough, very important because the focal trough in our machineswhen the patient bites down the anterior part of the focal trough is about threemillimeters so you dont have much of a margin for error. If the patient is a littleforward or back theyll be out of the focal trough and that area of the mouth of theanterior teeth will be blurred. Well see some examples of that in a moment.

Slide Number 9 rotational tomographyOk hers another example, some of the older machines werent on a flat cassette.They were on a drum and the drum would turn and not only would the x ray sourcestart here and here and this would turn in this direction but this would also turn. Soyou had a lot of motion going on. The theory in tomography is the more elaboratethe motion is, the sharper the picture is going to be. Theoretically. We use, we dontuse these things here, we use a flat cassette. You may see some old panoramicmachines that way.

Slide Number 10 panoramic units

So different panoramic units differ in the number and location of the centers ofrotation. The choice of a fixed or adjustable focal trough we spoke about. Type orshape of the film transport it could be a flat transport or a circular round transportand they all use intensifying screens. These are extraoral projections. Why do weuse intensifying screens? Less radiation to the patient. Those films are very, verysensitive to light. So when a small amount of radiation hits the cassette, light is givenoff by the intensifying screens which are the white structures inside the cassette. Sothe film is sandwiched in between the two cassettes. Ok? We happen to have apanoramic unit. Two of them that do not use cassettes. We now have digitalpanoramic x-ray machines so if some of the other older offices use these, well talkabout the processing of these films vs. the digital imaging. Ok?

Slide number 11 panoramic units continuedSome design differences, every manufacturer is different. The head positioningdevice and how the patients head is held is going to a little bit different. Some havea little knob that you can turn and squeeze and look at the patientseyeballs and seewhen they start to pop out you then stop turning the screw. No you dont do that,very gently and a bite block is different sizes, some go higher some go lower. All ofthose bite blocks are used to make sure the patient is in the proper position. If thepatient is in the proper position you will get a good image. If theyrenot in theproper position theyllbe outside of the focal trough and errors will occur. You havea different kvp and milliamperage settings. This is preset for you, some machines

you can adjust the kvp. So, if you have a little child in the office and you just took apanoramic image on an adult you want to reduce the kvp otherwise the image willbe dark. Kvp affects the image density or darkness of the film. Some machines havean automatic kvp sensor. So as it starts to turn like the first tenth of a second itllread out the amount of kvp and automatically boost it down or up depending uponthe patient. This is a wonderful feature when it works. When it doesnt work youregoing to get lousy films. So consider that when you purchase the machines. You guysare going to get out of dental school and open up your office. Panoramic machines,

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the one we have are about $45,000. Thats a difficult buy so if any of you areinterested let me know. I can set you up with a guy in Brooklyn. No hesactually notfrom Brooklyn. There are a lot of companies out theres, you just get in contact withthem. What they will do for you is you give them a space in the office, they will comein, and they will install a brand new machine for you. They will give you all the films

that you need. And if anything happens to the machine, they will come and fix it.What a country right? Theres got to be a catch. Whatsthe catch? It costs younothing, they put a meter on your machine. So every time you press the button tomake a panoramic image, youve got to give them 20 bucks or 30 bucks. Whateverthey work out for you. Sounds great right? You get a machine for nothing and yourecharging $150 or $200 for the image. Give them 20 or 30 bucks. But heresthe catch,you have to give them a certain number of films a month. So if you are first startingout you may not be able to do 40 or 50 films. If youredoing 50 films and youregiving them 20 bucks for film. What is that $1000? I dont know my math isnt verygood. So uh youregoing to have to consider that. So getting back to this, some ofthem are wall mounted and some of them are standing. All of them work with the

same principle. They just look different, they have different head holding devices,different colors and things like that. Some units can be used for tmj projections. Inorder to take tmj tomography which is slices of the tmj, youregoing to have to havea machine that can adjust the focal trough. A lot of students say, Dr. Friedman, whydo they make the focal trough so tiny? Doesnt give us much room to work. Butheresthe point, the smaller the focal trough is, the sharper the image is going to be.Because itsgoing to blur everything else out, and just have that sharp image. So thatsmall focal trough is advantageous to the dentist, because these machines areconstructed to see the teeth and internal structures. If you make the focal troughlarger, the image wont as sharp or as clear. Ok?

Slide Number 12- Different panoramic unitsAnd these are some of the machines. Notice theresall kinds of lights on here

because again you have a light for the patientshead. And every machine is differentso theyll either give you the ala-tragus line or theyll give you the Frankforthorizontal. You also have a little light going down the middle of the nose to positionthe patient to make sure they are not tilted. All of these are extremely importantbecause if the patient is not in the correct position, they will not be in the focaltrough or image layer and therefore the image will come out problematic.

Slide number 13 positioning requirementsThese are some of the imaging requirements: mid sagittal plane should be

perpendicular to the floor, depending on the machine youreusing there will bedifferent line ala tragus or Frankfort plane. Correct bite position or chin position,has to be parallel to the floor, slightly down. Head positioning prevents patientshead tilting. No patient movement. Tongue position. Now you would think, whywould the patients tongue be a problem? I think Dr. Chan showed you somepanoramic images where you saw something called the pharyngeal airspace, thedorsum of the tongue. Do you remember those? If not I have some images that illshow you. Itsvery important that the patient has their tongue to the roof of their

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mouth. What I tell the patient to do is youve got peanut butter on the back of yourpalate, can you get it off for me? That prevents a very radiolucent band called thepharyngeal airspace. Remember the pharyngeal airspace is the dorsum of thetongue and the soft palate. And well show you examples of that in a minute. And thelead apron, its different for a panoramic machine. Whatsthe difference between a

lead apron that we use for a pan and a lead apron that we use for an intraoral film?Well the machines going around the entire head and back of the patient, so there hasto be a back to the lead apron to protect the patient. The ones we have in clinic onlyhave one front part of the apron. The ones we use in clinic have the thyroid collar toprotect the patientsthyroid. You cantdo that with a pan, because if the lead apronis up too high in the thyroid area then you will cause ghosting in the area. Metallicimaging on the film which well show you in a little while. These are some of thelines that you dont have to memorize, the machine will tell you what to do. Theyreeither Frankfort horizontal or ala tragus. The midsagittal line should beperpendicular to the floor.

Slide number 14/15- common patient positioning requirement for panoramicunits/patient with lead apron and no thyroid collarHeresa patient with a lead apron and no thyroid collar. Because if any kind of metalcomes up in this area, the x-rays are not coming out in straight lines, theyll comeout in angles of 4-7 degrees. Dont memorize that. Because of that, when youretaking a panoramic image, the chin should be slightly down. The manufacturer willtell you that, very slightly down to compensate for the angulation. And well seewhen you have a ghost image, the ghost will be on the opposite side higher than theimage itself. Well show you that in a little while. These pictures are great.

Slide number 16 panoramic image

Ok so our panoramic image shows the entire dentition supporting bone fromcondyle to condyle on one film. Thats one of the advantages of a panoramic image,the larger the field size or broader area of coverage. Ok so if you want to see animpacted 3rdmolar you cant see it on a periapical film so that would be a reason forusing the panoramic film. Broader area of coverage. Well see examples where youcan see carotid artery calcifications, I think Dr. Chan showed you those on apanoramic image. Weve been finding a lot of those on older patients. We can pickup some calcification of the carotid artery. Only because you have a larger field size.However it lacks the same definition and detail as intraoral radiographs. It lacks thesame definition and detail as intraoral radiographs. It actually lacks the samedefinition and detail, and I repeat that because itsimportant. And there are reasons

for that. When you take an intraoral film, your film is very close to the tooth and welearned the object film distance. The closer the distance the sharper the image willbe. Take a look at the way a panoramic is taken. The source is out here, the film isout here, look at the focal film distance. The focal film distance is much longer thanit should be. When you have a long focal film distance, what does that do to theimage? By divergence it causes magnification of the image and loss of some detail ofthe image. The same holds true for the way itstaken. Theresan intensifying screenand light is given off. And the light thats given off is not going to give you as sharp or

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clear of an image as direct radiation. So those are some of the reasons it lacks thesame definition and detail. So if youre looking for an incipient carious lesion. Ifyourelooking for the beginning of periodontal disease, or the beginning of aperiapical pathology then dont use a panoramic image. Itsnot the way to gobecause it lacks the same definition and detail as intraoral radiographs for the

reasons I just mentioned. There are several other reasons. Ok significant horizontaldistortion. Again itsgoing around the patient so there will be a distortion in thehorizontal component of it. Less vertical distortion. Objects with greater densityappear in two places: the usable image and the ghost image. When you learn to readpanoramics youll see that theres all kinds of superimposition, all kinds of ghostthings. And a ghost occurs when theresa dense object. Ill give you an example thenshow you pictures. If the patient doesnt remove their earing. Well see whathappens. How many times will you see that earing on the panoramic image? Theanswer is two times. Youllsee the actual earing and itll be sharp, you can see everyloop in the earing. But on the opposite side youregoing to see a ghost image. Andthe ghost image is detrimental because it could block areas that were looking for

pathology or areas that we want to diagnose. So a ghost image has less sharpness,reversed, and seen higher than the actual image. So any metallic object or denseobject outside of the focal trough would you say that an earing is inside the focaltrough? No the focal trough is a very narrow 3d curved zone. Focal trough or imagelayer. So any metallic object outside the focal trough will form a ghost image. A lot ofstudents say to me, well Dr. Friedman the patient has implants all over their mouth,crowns, bridges and fillings. How come we dont see ghosting of those image? theanswer is that theyrein the focal trough. Ok so not all metal or dense objects willghost. Only objects outside the focal trough. Well see a lot of pictures of these.

Slide number 17 ghost images of the opposite sides of the mandible.

Ok heresan example of ghosting. If you look at these arrows here you seethis white line. The white line runs from here across there and we know itsnot ananatomic landmark. Theresnothing like a white line running here. We know thattheresa white line, which I cantshow you. The external oblique ridge. But this is awhite line thats not supposed to be there. How do we get the white line? It has to dowith patient positioning. But this part of the mandible since its cortical bone isdense, itllghost over to the opposite side and be higher. Itllbe higher because ofthe 4-7 degrees. Well see ghosting of the palate and a lot of things superimposedwith different structures. Youllnotice the patient had some sort of surgicalprocedure on the condyle on the right side possible a condylar fracture. Ok butthats the process of ghosting where a dense object is sent over to the other side if

itsoutside the focal trough.

Slide number 18- advantages of panoramic tomographyThese are some of the advantages of panoramic tomography. Size of field,

broader coverage we can see carotid artery calcification. Quality control. Itsmucheasier to position the patient then try to stick films in the patient mouth. Simplicity.Patient cooperation. What happens if they cant open their mouth? They just hadtrauma or trismus and cant take a PA film. Thatllbe one of the advantages of a

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panoramic image. What about the time? How long does it take to take a panoramicimage? About 14-22 seconds depending on the machine. You dont have to knowthese numbers. But as far as advantages, time is the advantage. Ok dont we have animage quality, definition and detail? No we dont have that. But we have time. Whatabout the dose? Were getting a picture of every tooth in the mouth like a full series

of x-rays. Getting condyles, coronoid process, lower border of the mandible,maxillary sinus, orbits, external auditory meatus, anything you can think of, hyoidbones, styloid process things like that. Whatsthe dose to the patient? When we usea cassette the dose is 4 bitewing x-rays which is amazing. With the digital machineits 2 bitewings. Very low dose. Thats an advantage as well. How can we get such alow dose of radiation if were getting all these thick structures like the skull? Itsnotlike a tooth where the film is next to it and the x-rays come through. It needs to gothrough the entire head. Whatsthe reason for that? Intensifying screens. Theyreused for extraoral films. Well see examples of those as well.

Slide 19 anatomical landmarks

Ok Imnot going over the landmarks. Dr. Chan covered that but I will saythere are certain ones you should know. I wont ask you questions about landmarksbut there will be questions about them and ill try to list some of those for you. Youshould know where the hyoid bone is, the styloid process, the bony structures

of the zygoma, zygomatic process and temporal bone. Ill go over that when wedo the review.

Slide 20- large field size carotid artery calcificationWhat this is showing you is one of the advantages of the panoramic imaging

you would pick up things that you wouldnt see in a full set of x-rays. You get thecondyle, the angle of the mandible. We have the sinuses and orbits. This is the hard

palate. This is the nasal septum. We have the anterior nasal spine. These are thestructures we can see in both panoramic and intraoral films.

Slide 21- disadvantages of panoramicImage quality is number one. You dont get the same definition and detail

because of the reasons we outlined. The distance and magnification. There ismagnification of the image. Imsure you have nothing to do over the weekend, butwhat you can do is take a panoramic on one patient if theresone in the chart.Measure the size of the first molar, go to the periapical film and measure the size.What you will find is that theresabout a 25-30% magnification on panoramic due tothe divergence of the x-ray beam and distance. So if youreplanning implant

placement for patient and take panoramic image and see wow theres10 mm ofbone there be careful. There may not be 10 mm of bone. So well tell you what youcan do when you do plan that. The focal trough or image layer is that curved zone,theresno image movement. That image is sharp and everything else is blurred. Youhave overlap of the teeth because again youretaking a curved or round head andconverting it to a flat surface. All kinds of superimposition. The zygomatic bone willsuperimpose over the palate and teeth. Distortion is based on what we just spokeabout. The other disadvantage is overuse. In clinic they send patients down for

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panoramic to check one area for an implant. Thats not an indication for a panoramicimage. Ok? And they want to check if theresan infection in tooth number 28. If youwant to see the infection in tooth 28 take a PA film. If you want to checkinterproximal caries in tooth 28? Bitewing. Ok so whatsthe best film to take

for interproximal caries? A bitewing. A bitewing is the best film for

interproximal caries. You may be able to see it on a PA but a bitewing is muchbetter, a lot better.

Slide 22- processing panoramic radiographsOk how do we process these panoramic films? The same way process in the

developer and fixer. Were not going to have this because we had coverage of that onprocessing but understand the safelight is very important. You cantuse the samesafelight as you use for PA. These films called screen films are a lot more sensitive tolight. So you have to use a specified safe light. Of course how do you check? Coin test.You can do that with a panoramic film as well. Make sure the safelight is not faulty.We can have the proper bulb but the filter may not be proper. Ok so use the same

film compatible with the screen. Check your cassette before putting the film in there.Static electricity: you go into the dark room and therescarpeting and you take yourfilm out of the cassette and touch your film and what happens? Static electricity istransferred onto the film. How do we see that when we process the film? Will weexpect to see light areas or dark areas? If you said dark areas yourecorrect becausestatic electricity is a form of energy. Any kind of energy such as light will fog the film.This is what youre going to see if I have the slide. Oh here we go.

Slide 23- static electricityIm going to leave that up for a while, I really dont have to leave it up because

you never see anything like that. It looks like a tree is growing out of the patients

eye. Typically its called the static electricity artifact and you get that when youeither take the film out of the package in the box and if its very tight and you pull itout and put it in the cassette you can get a static electricity artifact. Some textbooksrefer to this as dark lightning bolts. This is a nice slide to look at.Everyone look atit cause you may see it again.

Slide 24- common errors in panoramic radiographsOk uhh some of the common errors in taking panoramic radiographs. If the patientis in the proper position you wont have any errors. But you get patients that canhardly walk and you put their head in the machine, do the best you can. Some cantstand and have wheelchairs. Any error that occurs is due to improper placement of

the patient. Positioning is very important. If the patient is too far forward and dontbite in the notch, what does that mean? The anterior teeth arent in the focal trough.The anterior teeth will be very blurry. Posterior teeth may not be blurry. This is veryunique. Very rare that you have blurry posterior. The focal trough is much wider inthe posterior region. Anterior is the problem. When faculty sends a patient down forpanoramic anterior teeth we send them away because itsnot a good image. Therewill be problems. Too far forward will blur the anterior teeth. The teeth will be verynarrow, little skinny teeth like needles. Well see that. If you see little skinny blurred

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anterior teeth you know the patient was too far forward. If theyretoo far back,theyll be out of the trough and the anterior teeth will be blurry. Since theyrefurther from the radiation theresa larger circle so there will be fat teeth. If thepatients head is tilted up or down well seeexamples of that. If the patient is movingyou will get a blurred image. Thats why you have the head device. If the patient

failed to put his or her tongue on the roof of their mouth then you will get apharyngeal airspace which is a radiolucent band running across the upper

teeth. That band represents the dorsum of the tongue. Its the space between

the dorsum of the tongue and the soft palate. By having them put their tongue

up you eliminate that airspaceand make diagnosis easier.

Slide 25 Patient positioned too far forwardSo lets go through a couple of these quickly. The patient is too far forward. I

know itsnot a good picture. The anterior teeth are completely blurred. And theyrelittle tiny, itsy bitsy teeth.

Slide 26 patient positioned too far backPatient is too far back. This is not a good example. The anterior teeth should

be wider. Since its not a good example you wont see it on Monday.

Slide 27- patient head tilted upIf the patient is tilted up what youregoing to get is the hard palate. This

white opaque area up here is the hard palate and whatsgoing to happen is youllhave a flat occlusal plane. Or reversed like patient is frowning. This next one is avery nice picture. I dont have it in color.

Slide 28- patient head tilted down

This is a nice picture. The patientshead is tilted down. What would youexpect? The bottom of the chin will be cut off. You have a very exaggerated smileline. Very exaggerated smile line or V shaped mandible. Very exaggerated

smile. What you see here in the center. Does anyone know what the opacityrepresents? Something called ghosting. What would you guess the opacity is? Thespinal column since the patient is down. What you have to do when you take a pan ispull the guys head so that the spinal column isnt superimposed. If the head is tilteddown or patient is slumping you will get opacity which is a ghosting of the spinalcolumn which is a dense object outside of the focal trough. Were going to see thespinal column in three areas on a pan. Thats the ghosting. If you have anexaggerated smile line, chin is cut off, the patients head was tilted down. Ok?

Slide 29- patient movement during exposureEverything blurry posterior teeth and anterior teeth.

Slide 30 tongue not against the roof of the patients mouthTongue not against the roof of the mouth what happens? Follow the arrow

for a dark radiolucent band. The bottom of the radiolucent band represents thedorsum of the tongue. Did Dr. Chan show you that? You should know that the

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bottom of the radiolucent area, in the pharyngeal airspace is due to the patient nothaving their tongue to the roof of their mouth. This is a problem in diagnosis. Makesure they put the tongue there.

Slide 31- common errors

Other errors. The patient slouching youllsee ghosting of the spinal column.Failure to remove objects: the patient doesnt take the hearing aids off. They donttake their earrings off or any kind of bobby pins. Itsgoing to ghost. Ghosts are nice.WhatsCasper the friendly ghosts favorite yogurt flavor? Boo berry. I dont knowhow I got a ghost joke into panoramic radiography. If you dont remove the metalobjects youllget ghosting because those are dense objects outside the focal trough.Lead apron placed too high on the patient in the back of the neck then the x-rays arecoming from 4-7 degrees. Youllget what looks like a sharp fin. Have you ever beento Coney Island? See any sharks? Theresa little fin comingyoullsee an example.You wont see it in a book but thats what I call it. What happens as the device isturning around the patientshead, you have a patient with thick shoulders and all of

a sudden his shoulders stop the machine. What youllget is radiation will keepcoming out of one spot. So you will get a dark radiolucent line where the machinestopped. Ill show you an example of this. Static electricity we saw, thats a good one

Slide 32- patient slouchingHere we have an example, the only explanation for something like this is the

patient was slouching. This is a ghost image of the spinal column from patientslouching. If the lead apron is too high, you wont get that that high because theapron wont be up to the top of the patients head. What you will see is an inverted vshaped opacity at the bottom. Very common on a lot of these films.

Slide 33 failure to remove metal objectsLets do this one first. Man, whatsgoing on here? First of all the patient has glasses.Ok those glasses were left on. This actually is a ghost image. This isnt the patientsearing it would be way off to the side where we cant see it. This is a ghost image ofthe opposite side. What does the patient have? Braces. If the patient has braces its amajor problem because there are no roots. What happened to the roots here?Straight teeth and no roots. These are not braces. This is a denture left in place. Theopaque things in the denture teeth. Therestwo types of denture teeth: acrylic andyou wontsee these in that because the acrylic teeth will bond to the acrylic base ofthe denture. What about porcelain teeth? Does porcelain bond to acrylic? No itdoesnt. So how does the technician make a denture with porcelain teeth? There are

little metal pins that retain the teeth on the denture. This patient has a dentureglasses and earrings. That shouldve been removed.

Slide 34- placement of lead apron too highThis is that little shark fin I was talking about. This is not the spinal column. If

it were it would go way up to the upper teeth. Ok? So we also have another exampleof the pharyngeal airspace here. Theresa dark radiolucent area band here as the

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patients tongue wasnt at the roof of their mouth. This again is the hard palate here.This is an example, this is very unique. Itsalmost like the static electricity.

Slide 35 film cassette slowed down because of patient contactWhat happened here is the patient was having a pan taken. As it went to the back of

his head it got stuck on his shoulder. The machine stopped and radiation keptcoming out, you have a radiolucency here, which represents where the machinestopped. Newer machines if it stops will shut off radiation and the patient wontgetthat excessive radiation. Imgoing to keep going because I want to spend more timeon the review. I apologize for coming in late.

Slide 36/37 extraoral radiograph techniquesWere going to talk about extraoral radiograph techniques. Extraoral films are

indicated when a patient cannot or will not open his/her mouth for the film to beplace intra-orally. When the area being radiographed is larger than or cannot beseen on an intra-oral radiograph. If you suspect some sort of fracture of the

zygomatic arch, the patient comes in and yourein a residency program. The patientgot hit with a bat. PA and intraoral will do nothing for you. If you want to seecondyle PA will do nothing for you. You need a way of seeing object or pathologyaround something like the 3rdmolar and you suspect its a cyst then you needsomething a little larger. An extraoral film is different than panoramic in that itdoesnt move. Its static. The panoramic image is a unique image like a computertomography, which uses movement. This is a static film. The film is kept stationaryand the source of radiation is kept stationary. Lets go over some of the films. Whatdo we need to do? Need to take an extraoral film, need a regular dental x ray unit, acassette that looks like that which has a film screen combination in it holding deviceand a grid. The grid is optional, well cover that in a little.

Slide 38- extraoral cassetteThis is the extraoral cassette if you look inside you see this white material.

Those are the intensifying screens, which reduce radiation to the patient. You canplace this on the wall raise or lower it. The patient is positioned and the film isplaced in here.

Slide 39 a wall-mounted cassetteA wall mounted cassette holder, and the patients head is positioned in

different ways to get the image youreinterested in seeing. There are indications forall of these images. Some of these machines will have a grid. And what the grid is is

you place the grid in front of the film. So this is the film here.

Slide 40- grids/extraoral radiographyThis is the grid. What it has is a radio resistant area where the x-ray cant

come through and there are radio transparent areas too. The radio transparentareas are parallel to the film. Perpendicular to the film, excuse me. You want themost perpendicular rays to prevent magnification of the image. Another thing youcan notice is when we take extra oral films, in order to get entire image on the

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(break)

So we spoke about the lateral oblique projection. Theresa lateral skullprojection and a lateral skull projection is where the cassette is placed here and the

x-rays come from the side. Orthodontists use lateral cephalometric projection tomeasure facial growth, predict facial growth.The reason its cephalometric-cephalos meaning head and metric meaning measuring. They want to put differentpoints on the skull and measure its growth so they can determine the progress ofthe braces and youlllearn that when you get into orthodontics. The differencebetween a lateral skull and cephalometric projection is that the cephalometricprojection is always taken at the same distance. Itsusually taken at 5 feet. So everytime the child or teenager comes in and they want to take measurements to see howit grew in relation to the initial ceph it has to be done exactly the same way. Thesame distance otherwise itll be comparing apples to oranges. The lateral ceph isused by orthodontists to predict and measure facial growth. Its a form of the lateral

skull projection.

Slide 47 posteroanterior projectionThen you have something called the poster anterior projection. So think about howyouregoing to have to do that. The x-rays are coming postero-antero. So you willput the patient like this and have the x-rays come through that way. Posterioranterior projection. What happens if you put the cassette back here and you comethis way? Anterior posterior projection. Whys that not on the list? We dont use itmuch in dentistry. And the reason we dont use it and usethat if youre looking for askull fracture in a hospital. For dental purposes we know structures closest to thefilm will be sharpest. We know that about image detail. When were looking for facial

structures you want it as close to the facial structures as possible and thats why wetake a postero-antero projection and not the other way around.

Slide 48 posteranterior waters view of the maxillary sinusThere's another called the waters view which is a postero-antero projection

with some variation. It enlarges the middle third of the faces and if youre

looking for maxillary sinus pathology using a cassette and regular x-ray

machine, not talking about advanced imaging but if youre looking to see

maxillary sinus pathology then the waters view is the way to go. So use waters

projection for maxillary sinus pathology using a cassette and x-ray machine. Ofcourse there are many many ways you can see the maxillary sinus with advanced

imaging techniques. From an extraoral cassette if yourelooking for maxillary sinus,and youllsee why when we see pictures of these.

Slide 49/50/51 submentovertex projection/anatomy of the tmj sagittalview/transcranial tmj projection

The last one is called a submentovertex. Try to figure that out. It means thatyou're coming below the chin, the vertex of the skull is the top of the skull. So youhave to put the cassette here ok? Imnot making this up. And you have the patient

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tilt their head all the way back ok? And come in underneath here. As youllsee its avery good projection for the zygomatic arches. Zygomatic arches are the cheekbone.So if you suspect a cheekbone fracture the best type of extraoral film would be

a submento vertex. Submentovertex is used to see zygomatic arches. If you

have any reason to want to see the zygomatic arches I would suggest a

submentovertex. So this is a lateral oblique projection coming from underneath thechin. What youllsee is everything on the opposite side, you can also do this with anocclusal film. For those of you that had preclinic I showed some of the students howto put the film on for wisdom tooth impaction or infection. You can put that here andthe source comes from underneath the chin. Thats why itscalled a lateral obliqueprojection. Coming from the side, the direction of the rays is from an oblique angle,thats opposed to a lateral skull film which is coming directly from the side. This iscalled a lateral skull projection. This is useful for systemic diseases such as cottonwall appearance on skull or Pagetsdisease. If youre orthodontists youlltake thisand itllbe called a lateral cephalometric measuring of the head projection. The onlydifference is here you dont have any specific distance.

Slide 52- positioning angling board for transcranial projectionWith a cephalometric film you place the patient in whatscalled a cephalo

stat. whatsa cephalostat? Something that holds the patients head in one positionevery time you take the film. So thats a variation of the lateral skull projection. Thecephalometric projection is used by ortho to measure facial growth. This is what acephalo stat is. Put the patient here at a set distance from the radiation and putthese in the patientsear. Get a device that holds them steady, take a lateral skullprojection. The orthodontist will take measurements off of that and plan the orthoprocedures based on the lateral ceph film. This is a postero antero projection againthe cassette is their the x-rays come from the back to the front. The structures that

was most interested in such as the nasal cavity sometimes to check for growth orfracture of the nasal septum. Very good film if patient has a lesion in the mandibleand we want to check if itsmoving laterally you can see it bulging on thisprojection. Heres a posterior-anterior projection. Whats the difference here? Onthe first projection the nose was up against the cassette and the chin was away. So ifyou put the chin, have the patient tilt their head, put the chin on the cassette, youcan have all sorts of variation. Take a look at this its not very clear I apologize. If thelights were down you could see right here are the maxillary sinuses. So by havingthe patients do that, its a posterior-anterior projection and the mouth is open, thechin is against the cassette. You get the waters view which is excellent for maxillarysinus pathology. So how do we tell difference between anterior posterior projection

and a waters view? If we look at them youllsee magnification of the middle third ofthe face that shows the sinuses. Youllsee the odontoid process. You dont have toknow that. On the posterior anterior you will not see that. So again magnification ofthe middle third of the face to diagnose sometimes we can see an infection if thesinus is cloudy. It needs to be very black and radiolucent because itsbasically acavity in the skill. Any growth and well see clouding or some kind of polyps orgrowth in sinus. This would be an excellent film. This lady is smiling but shesnot in

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the correct position. The cassette is on her head and the x-rays are coming fromunderneath, it looks exactly like this.

Slide 53- submentovertex projectionTake a normal submentovertex projection. At a normal kvp itlllook

something like this. But look what happens to the zygomatic arches. Very difficult tosee them. Because the x-rays are going through and burning that area out. Too muchkvp and exposure. So what do you do? If you look at the top one here thats asubmentovertex with lower exposure. Therefore you can see on the right sidetheresa depressed fracture of the zygomatic arch. This patient was hit with a batthat fractured zygomatic arch on the right side. So this is the best way of seeing ita submentovertex underexposed. Regular exposure would not show this.

Slide 54/55/56/57 conventional panoramic view of the tmj-endWe used to do these years ago with tomography of condyle with TMJ area. Wewould see the medial and lateral of the condyle when we used the SMV. We dont

use that anymore cause now we have a more sophisticated machine. So again toview the zygomatic arches underexposed submentovertex image. As far as the TMJwe wont go into it deeply. Just know that you can see the condyle on the panoramicimage. Can rule out gross pathology. But better views of TMJ are tomographicimages of the TMJ. The old way was trans-cranial. We dont do that any longer. Herewe can see the lateral and medial of a submentovertex. This is normal exposure soyou cantsee the zygomatic arches here. This is a tomographic view of the TMJ. Oneis an open position and one is closed position. This position the patient is openbecause theyreout of the glenoid xfossa. Heresthe articular eminence.

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17/18: ExtraOral