You can sing. You can You Hello, I'm Antony Chadwick, the founder of the webinarett, and I'm really, really pleased to be able to welcome you to my wonderful city of Liverpool, of course, the home of the webinar Bet and the place where we've run our virtual conferences since 2013. This is the 9th annual virtual Congress.
I hope you've enjoyed the visions of our city, the views of our city. I hope you're going to enjoy your next. A few days of virtual enjoyment watching the webinars which you of course can watch at your leisure afterwards as well.
So sit back and enjoy the learning and who knows, one day we'll get to our system as well. So take care and enjoy. Hello, Anthony Chadwick from the webinar Bet.
Thank you so much for getting up bright and early. If you are in Europe or the UK, otherwise happy, good afternoon, good evening, wherever you are. Thank you so much on behalf of the webinar for for joining us for this first live session of VC 2021.
We're very fortunate today to have Mike Hertage, Professor Mike Hurtage from Cambridge Vet School, who's going to be speaking about MRI and CT, what's best to use when. I'd like to thank all of our event sponsors. Please visit the Vet exhibition to find out more, and there's links in the chat box so you can go and have a look around there, later on.
Recommend to view these sessions on a tablet, laptop or desktop rather than the phone for the best quality. And all these webinars, over the next few days will be available for 12 months after the event, so there's plenty of time for you to go in and watch them at your leisure. Don't forget to also visit the exhibition where there's the goody bag with various prizes that you can win, and actually just attending, One of the webinars means that you're already in one of our prize draws for some cash potentially drawn this time next week.
If you do have any questions, please use the question and answer box. And, you know, do get involved in the Hoover app where there's, there's lots of exciting interaction already going on and you can get to know your friends and colleagues, and also within the exhibition, we do have some video chat rooms where in the evenings we'll be holding some events as well. So lots going on, do have a, a play around and an investigation, and I'm sure you're gonna have lots of fun with that.
And hopefully lots of learning as well. Mike graduated from Liverpool University and then, immediately went to Cambridge to be a house officer, and has spent all of his career there. He's ex-dean of, of the vet school, and he's a fellow of Saint Edmund's College, Cambridge, well known, I'm sure to everyone on the call, Mike has More diplomas than I've had hot dinners.
I'm gonna let him introduce himself if he he wants to, but we're really thrilled to have Mike on. He's one of our top speakers, was named vet, webinar vet Speaker of the Year a couple of years back. So I think you're gonna really enjoy this and really looking forward, Mike, to learning more about CT and MRI.
Thanks over to you. OK, thank you very much indeed, Antony, and thank you for that kind introduction and welcome everyone to the virtual Congress 2021. It's a real honour to be amongst the first speakers at this conference.
So my task today is to talk about CT and MR. I'll give a brief overview of the different way in which the images are acquired, and then talk about what's best to use and when. So without more ado, we'll start off with CT.
We start off with CT because this uses ionising radiations, and of course, we're quite used to using ionising radiations in in the way in which we use radiography. And so we can immediately Understand a little bit better the image formation in CT compared to perhaps MR which is slightly different in the way that the images are formed and the way in which the technique works. So this is a modern CT unit, in fact, a 64 slice unit, and we'll see how that works in a, in a few moments.
Now CT is really revolutionised imaging. In the medical field and in the veterinary field. Part of the problem with a standard radiograph is that it's always a shadowgram of a three dimensional object in a two dimensional plane.
And that shadowgram means that it's quite difficult to pick out minor changes in the anatomy, and most of you will have appreciated that, I'm sure, from time to time when you've imaged it. Those of you who use ultrasound. Will be aware of the sort of slice imaging that ultrasound can do and CT can do that as well.
So it forms a slice through the patient. Here we have the patient in the middle of that gantry. They're on a table, and that table may or may not move.
And in the early CT images, then the X-ray tube would rotate round, and opposite that there was a row of detectors that detect the attenuation of the beam through the patient as the X-ray moves around the patient. Now, a number of changes have occurred over the age over over time really with the different generations. Certainly the X-ray tube still rotates around the patient.
However, the detectors now just form a ring around the patient and the X-ray tube. The tube which initially could only rotate through 360 degrees and then had to rotate back again to its original position before it could rotate and cause the second slice, can now continue to rotate through a technology called slip ring. Changes which allow the high voltage cables to be applied to the X-ray tube as it spins around.
Previously, of course, the wires would go into the tube and so it could only go for 360 degrees before having to return to its standard position. Now the rows of protectors initially were limited, they were quite expensive and . They were quite elongated to form a slice of a of a known thickness, and slowly the number of of detectors in the ring was increased and the X-ray tube then fanned out more to cover those detectors.
And so if you have a relatively old machine, it'll be a full slice. It takes quite a long time to acquire the images, . And of course it gets heated, so occasionally you have to cool it down before we till you can take the next image acquisition.
But now we go on to 3264 and you can get 128 slice images, CT scanners, and they can produce the images much faster. So here we have a single slice, and what happens with the patient now is it moves slowly through the gantry so that we acquire the images in a helical array. And obviously, if you have 64 slices, you can move down the body very quickly, and that means that we can acquire images in a very short space of time.
So an advantage of CT is that it is quite quick, but it is using ionising radiation. So, the advantages of a multi-slice CT are not only the faster scanning times that I've mentioned. And we can often get through within a matter of seconds to do, say, the chest of a dog.
But we have the advantage of doing a large coverage. We can use thinner slices to get more information, more resolution, and we can also acquire images, . As isotropic voxels, and the voxel is the detector and if we can get a volume of, of information, then we can cut that information in any and which way.
And so multiplanar reconstructions that I'll show you a little bit later become possible. We don't just have to look at the sequential slices as we go through the patient. Now, this produces a vast amount of information and you know, a medium to large breed dog, if you were to do head to tail would require something.
In the region of about 20 to 3000 slices. So you've got a large amount of information that has to be sifted through to get the most out of this imaging modality. Now, as the X-ray beam passes through the patient, the beam is attenuated, and the detector picks up that attenuation and each pixel of information picks up that, that chain.
Now this can be converted into Hansfield units. Hansfield, Godfrey Hansfield was the British inventor that developed CT for EMI at that at that time. And the units are fairly arbitrary, and they go from -1000 for air up to around about plus 1000 for bone, and you can see that bone varies depending on its compaction from about 700 to + 3000 for very dense bone.
Lung, which contains some soft tissue, comes down to about -500. Fat is, of course, less opaque than, than soft tissue. So it's -100 to -50.
Is 0, so it's right in the sort of midline. Then CSF of 15, kidney at 30, blood at between 30 and 45, muscle between 10 and 40. That means that we can start to Pick up some changes between the tissues that we image.
Now, when we look at a radiograph, of course, we can see fat because that's different from soft tissue, but soft tissue and water have the same radio opacity, so we can't differentiate between, say, the chambers of the heart or the contents of the bladder without using contra contrast techniques. Now we can do that to a certain extent with CT but we add in contrast very often, and that will intensify the the image by producing a higher number of hands filled units than the standard if it's got a blood supply, and that is going through the blood supply. So let's look at a few images, because these are the sort of images that we get.
This is taken from a multiplanar reconstruction of an elbow joint. For those of you who aren't used to looking at elbow joints, this is a normal elbow joint. This is the radius.
This is the ulnar taken as a transverse image. In the dorsal plane, showing the medial coronoid process of the ulmer, something that can easily fragment, something that can be quite frustrating to look at with standard radiographs, because we look for secondary. Degenerative joint disease associated with the fragmentation of the medial coronoid, but here we can see the medial coronoid has broken off this ulna and is now tipped up and rotating into the joint space.
So just by taking a slice out of that two dimensional image from a three dimensional structure, we can see a lot more information than we can on a standard radiograph. Here are some reconstructions from the stifle of a dog taking the sagittal. View through the lateral condyle and through the medial condyle.
And if we look at the medial condyle first, we can see that it's got a nice smooth border, the subchondral bone is quite clearly defined as it passes around, the condyle comes up here in the next slice into the trochlear ridge. But when we look on the lateral side, we can see a large defect in the caudal part of the condyle, with sclerosis of the bone underneath it and a soft tissue filling. And this is an osteochondrotic lesion of the lateral condyle of the, femur, of the dog.
Now those of you who look at spaniels will know that they sometimes have this humeral intercondylar fissure, sometimes called an incomplete ossification of the humeral condyle. . We now think that this is more an acquired lesion than a developmental lesion, but there is a weakness between the two aspects of the condyle that can allow this fissure to develop.
Now we can see that with arthroscopy, if it goes through the cartilage, and if we're very lucky with a craniocoral view of the elbow on a radiograph, we might be able to image the fissure if it passes at right angles to the the radiograph. But very often these fissures go obliquely across. And they can be extraordinarily difficult to image on a radiograph taken in two directions as we normally do for the elbow.
But when we actually form a slice through that condyle, we can see the fissure quite clearly, we can see the sclerosis, on each side of the fissure. And if we look at an animal that might have damaged this and perhaps broken the elbow by fracturing through the through the condyles. Then if we image the other side, we might find the start of a fissure, an incomplete fissure there, and therefore that animal can be treated prophylactically to prevent it from, fracturing at a later stage.
Now, other advantages of CT are not just the multiplanar reconstruction of the image, but the ability to produce three dimensional models that we can edit and then spin around. Now this is from a police dog that was in a riot and and during the riot, a brick was thrown at the police dog. And the dog actually carried on working for a couple of hours after this and then collapsed, and so it was noted that it has skin wounds, so it was thought that some underlying damage.
But what we can see here is obviously a fracture of the Skull through the frontal sinuses. Here we have the frontal sinuses. Here we can see the orbit is just affected by the frontal sinus being pushed down a little bit.
It's a common muted fracture, as you might expect from the point of a brick hitting. The skull, but the most important thing from this dog is that when we look at the cranial, the the cranial vault, we can see that this is totally intact. So whilst this obviously is a serious injury, it hasn't fractured through to the brain.
And with CT, which is pretty sensitive for looking for subdural hematomas, there was no subdural hematoma there, and actually this dog made a, a full recovery. But you can see that not only producing this image, but then by editing it, by taking off the nose and taking off the back of the skull, looking down into the frontal sinuses, you can get a really good impression. Of, what is going on, within that, with that fracture.
Now, all of that information is on the original slices and is available, of course, in the multiplanar reconstruction. But you have to be quite experienced to be able to interpret that, and, and if you're trying to explain to somebody, you know, what actually has gone wrong, then it's quite useful to be able to produce these these image reconstructions so that people can understand better what is going on underneath that. Here's another example, a dog that was lame on the radiographs of its shoulder, both the craniocaudal and the lateral, we could see this fragment of bone, but it wasn't clear where that fragment of bone was coming and why or whether that fragment of bone was associated with the lameness that the dog was showing.
But Here you can see the fragment of bone, and you can see where it was coming from, and this, of course, is the site of the insertion of the infraspinatus muscle. So we were able to show that this was an avulsion fracture of the insertion of the infraspinatus muscle, and yes, that would be associated with with lameness. Now many of you will be able to identify that this radiograph of the chest shows a soft tissue mass in the ventral lung.
On this right lateral view, it's fairly clearly defined. On the left lateral view, it's less clearly defined. And since we know when we lie an animal on its side, the lobes nearest to the plate will deflate and the upper lobes will overinflate.
So by just showing these two views, we can predict that this is in the left cranial lobe. And we can see that on the dorsoventral. So we look around the lungs, these are good quality radiographs and because we've got a solitary mass within the lung, we'd be thinking that this might be a primary lung tumour.
Primary lung tumours can be removed surgically, and you can get a good resolution providing there's no secondary spread. But when we do a CT, then we find as we take the slices through the, thorax that we've got another nodule here in the dorsal image of the right lung field. Further back, we've got another one in the caudal lobe of the left side, .
And another one here on the right side. This has multiple secondaries associated with that, primary, tumour. So this wouldn't be a good candidate to remove the primary because these secondaries would grow, particularly this one would, would double in size over its, over its, its appearance.
So. That would require different type of treatment. Here we have again a mass within the, the lung, and we can see from this view and from this multiplanar reconstruction, it's in the right, side, and from this model that we can generate very quickly, then we can see.
Where it is actually attached to or in contact with the chest wall. And that allows us then to do a fine needle aspirate of that mass to be able to ascertain the actual pathology of the mass. In this case, here, we have a springer spaniel 6 year old with a one month history of coughing non-responsive to antibiotics.
And on our radiograph, we can see an increased capacity within the caudal left. Lung field, but we can't see much more about that. We can see the bronchus going into the left caudal lobe.
We can see that there's some peribronchial infiltrates around that, but we can't see exactly what is going on. And so we took a CT of that, and if I can get this CT to work and scan through, which I'm I think I can. OK, so these multiplanar reconstructions show us that in that caudal lobe, and here we have the caudal lobe, we have a foreign body blocking the bronchus.
We've got some thickening. Of the of the mucosa of the bronchus. We've got some changes further down the lung, where infected material is passed down, and caused some inflammation within the perirronchial tissues.
This foreign body looks very much like a And the ear of wheat, and we can see on this sagittal view that it's blocking the bronchus. It's wedged within the bronchus, and that's what's causing our increased capacity that we could appreciate on those original radiographs. But now we can see it in a lot, lot more detail.
So here in the left, dorsal bron called lo bronchus, we can just see the edge of the, the foreign body. We know that it's a lot longer than that, so we shouldn't be happy until we've seen the whole of the era of wheat removed from that bronchus by endoscopy. We're looking at carcinomas of the adrenal adrenal masses, and what we find is that as with ultrasound, there are a lot of animals that have incidental adrenal masses that are imaged fortuitously perhaps at abdominal ultrasound.
Here we have a CT of the abdomen of an animal with an adrenal mass. The reason for doing this is not, in fact, just to diagnose the adrenal mass that had already been diagnosed by ultrasound, but to see whether or not this mass would be surgically removable. So here we have the right kidney, the left kidney, spleen and liver, the caudal vena cava coming through here.
This is with the uncontrasted image. We've got a little bit of calcification within the mass, which is quite common for adrenal tumours, but we can see tissue around that. And just To ensure that if we give contrast, then we can find that there are clear borders.
There's some blood vessels going into the mass here, but we can get around this mass, and it's not invading the caudal vena cava through the frenico abdominal vein, which is quite a common problem with adrenal masses, whereas This dog, which has a smaller adrenal mass, again, we're showing the post contrast views. We can see the heterogeneous pacification of this left adrenal mass, the renal vein coming around here, but it is growing in through the frenico abdominal vein, directly into the caudal vena cava. And extending about halfway across the caudal vena cava in this particular case.
So that would mean that surgery for this would be technically slightly more complex, not impossible, but, but certainly it would have a higher risk than the last case, which actually had a larger adrenal mass. Now, in this case, here's the pre-contrast image, the post-contrast image, again, it's a left adrenal mass growing into the caudal vena cava, tending to fill up most of the caudal vena cava, which you can do without developing any clinical signs associated with obstruction. Of the caudal vena cava, but actually extending right the way up the caudal vena cava.
So here we have the thrombus, extending right up to the diaphragm, and that would be technically much more difficult, to remove, without it fragmenting off and going off into the lungs, causing a pulmonary embolus. Contrast examinations can be used in all the ways in which we can use them for standard radiography. So here is a contrast examination, just an intravenous contrast taken at a time interval that will show the portal filling of the vessels.
So here's the vessel, portal vein coming through and then going. Forwards joining up with the caudal vena cava here. And this is an intrahepatic portosystemic shunt in in a cat.
So really quite a small animal to be able to image and get the the diagnosis, but with just an intravenous injection of contrast and taking the timing appropriate to filling the portal system, then we can get that diagnosis. And likewise, we can use contrast for standard radiography and an intravenous urogram to show ectopic ureters. Here we can see the ureter coming down across the bladder wall.
It normally implanted the bladder wall here, but actually it extends cordially and goes in. To the urethra a little bit further down, some filling then of the urethra. And again, this is a cat, so really a very small, young cat, with, really good diagnostic information that we would have probably some difficulty in producing on standard radiographs.
This is a greyhound with a yotthorax, we knew that it obviously it had a kyothorax, but the question is, would ligation of its thoracic duct actually help this dog? And so we inject contrast, usually into the popliteal lymph nodes. They drain into the abdominal cisterna chilie, come through the diaphragm.
Usually there are several thoracic ducts that come through. Normally this would come round and then join the cranial vena cava just in front of the heart. But what you can see here is a large number of anomalous lymphatic vessels that have taken up that contrast and make it really quite difficult to think that surgery is going to make a great deal of difference so this dog was treated medically for this condition.
OK, enough, there's an introduction to CT. What about magnetic resonance imaging? Well, the, the actual machine might look similar from the outside.
You've got a table, and you've got a bore, but in this case, it's all associated with magnetism, not ionising radiation. And There are high field magnets, as you can see here, and then low field magnets, which you can see here, and a lot of practises have invested in low field magnets because they are ostensibly cheaper to buy and cheaper to, to, to run. And we'll talk a little bit about the advantages and disadvantages of, of, of each as we progress through this presentation.
But these are two examples, an open magnet, in a low field MRI. MRI system. It allows us access to the patient more easily.
As you can see there, we can actually turn the magnet on its side. This is one for looking at the horse's distal limb produced by Hallmark. So what are the advantages of MRI?
Well, in terms of imaging, it is absolutely excellent for tissue contrast, especially for soft tissues. It will differentiate between muscle and tendon. It will differentiate between the cartilage of the lining of the joint, to the bone, from the fluid that will be within the joint, it really does provide such exceptional tissue contrast that is just not possible to produce from ionising radiations, even if you use contrast techniques to try and increase that tissue differentiation.
It has multiplanar imaging capacity. You can image a subject in any direction, and that allows us, therefore, to get the best possible images, to produce a diagnostic a scan. Now we mentioned multiplanar reconstruction.
Of CT and they have improved dramatically over the last 10 or 15 years. So we do have multiplanar capacity with both techniques, but the imaging quality with MRI can be exceptional. The other interesting thing, of course, is that it lacks the use of ionising radiations.
There are safety controls, and we'll talk about some of those in association with the magnetic force, but really, the imaging does cause no permanent damage. It can heat tissues a little bit, but, but there's no real known side effects from that. And that Means that we can follow diseases.
Obviously, brain and spinal cord injuries are are things that, change over a period of time, and we can monitor the progression or monitor the resolution of these changes without adding to the ionising radiation load that that patient would suffer. And when we think about CT, CT would provide. Something in the region of about 100 times more ionising radiation exposure than a standard radiograph.
So, you know, it's not an insignificant amount of ionising radiation and therefore, there has to be a risk benefit to the patient of providing that examination. Also, there's no beam hardening artefact that can occur, particularly with the earlier and smaller CT equipment whereby the X-rays going through bony structures, particularly the base of the brain around the middle ear, become hardened by the amount of bone that's present in that area compared with other parts of the skull. And that, gives rise to a particular artefact that makes it difficult to get information, say, from the middle and inner ear.
Now, the technique of MRI, I won't go into much detail, but, but it relates to the hydrogen ion. Hydrogen ion, of course, is diffusely distributed throughout the body, and the nucleus of the hydrogen ion is made up of one proton. And these atoms spin.
They spin like a, a spinning top, and they go in all sorts of different directions, so they do have a magnetic pole because they're spinning, and that magnetic pole can be in any, which direction. However, if you put it into a strong magnet, then they will always align along the force of that magnetic field. Now, not always the same way, so north may be up.
You can see here, but it can be downwards as well. But they do align along the lines of the magnetic field in that strong magnetic field. What then happens is that a radio wave is passed into the body, and that sends these protons into a procession that knocks them out of the axis of spin.
However, they then realign, and when they realign, they give off a radio frequency, and the size of that radio frequency can be computer generated into an image as to what's happening to the hydrogen ions, within the body. And that's how MRI produces the images. Now, the advantages of a low field MRI is that the purchase and installation costs are less than a high field MRI.
A high field MRI requires super cooling of the coils to produce the electromagnetic force at a much higher rate. Permanent magnets though, that are used in low field require no power supply, and they're made of ferromagnetic substances that retain their magnetism. The operating costs, therefore for a low field are significantly, less than for a high field magnet, and that's why many people have gone for low field MRI, and in terms of producing a good image, if you, concentrate on.
Getting a good image, you can get just as good an image with a low field magnet as you can with a high field magnet, certainly for diagnostic purposes, but the major area with of of disadvantage will be that the field of view is much smaller. And so, you may have to move the patient several times, reposition it, re-scout the images, and, and, that takes considerably longer. So in permanent magnets, the lines of flux run vertically between the poles of the magnet, and that keeps the magnetic field really con confined to a very small area of the around the magnet.
And the very little free fringe fields, magnetism. And that's really important from the point of view of magnetic objects that might be brought into the magnetic field, because these are a real danger. Even with a low field magnet, you would get a pair of scissors moving from the examination table to the magnet, and they would be very difficult to remove.
With a high field magnet, they would be. Moving at great pace even from areas around the magnet and could damage either people or the patient on the way to the magnet, and then they can be extraordinarily difficult to remove, and the larger they are, the more difficult they will be. So, .
There are disadvantages from a high field magnet. Here you can see an oxygen cylinder that's sailed into the gantry that would have taken off and moved at pace to get to that position. Anyone in the way probably would have been killed by that oxygen cylinder moving into the magnetic field.
Here's a magnetic. A trolley, that shouldn't have been anywhere near the magnet, and you can see that again it's been sucked into the magnetic field. So there are real dangers of high field magnets that aren't quite so dangerous with the low field magnets, and great care needs to be taken and and made absolutely clear that magnetic items should not be taken in.
This also means that animals with ferrous magnetic material within them. Are at risk of the magnetic forces moving that foreign material, and, sometimes causing damage, particularly for sensitive organs like the eye, a splinter of ferrous metal within the eye, for example, would be a contraindication for for MRI. So we know that there are magnetic dangers of, of high field magnets that we have to be careful with and, and need to, to avoid.
They're less serious for the low field magnets. However, the disadvantage of low field magnets is that there's a lower signal to noise ratio, so, that you need more signal averages or longer imaging times will be necessary to produce the same degree of information. And now there are ways around that with computing to generate fairly good or very good images of the brain, and most of the ones that I would show you will be actually from low field just to show how good those images can be.
However, there, there are other restrictions. There are less pulse sequences that can be developed for low fields. There's impaired detection of calcification and haemorrhage, compared with the high fields, and they enhance less with gadolinium, the contrast.
That's used for MRI then with the high field. So there are swings and roundabouts, but as a diagnostic machine that's going to be used on a regular basis, low field is certainly one that can be worth considering. But it does have its limitations.
One is the field of view. Here we You can see an image in the centre, but towards the periphery, the field of view becomes slightly stretched, compared with a high field where we can get the whole of this abdomen in place, and we can see that there's a nodule within the pancreas in this case associated with an insulinoma. So what is MRI definitely useful for?
Well, we know that it's useful for the brain. It produces much, much better images of brain tissue than you could ever get with a CT even with contrast. So, for, conditions of the central nervous system, the brain, the spinal cord, MRI would be, the best, technique to be used.
But it's also useful for other areas of the head. The, nasal chambers and sinuses can be imaged extraordinarily well. Compared with the CT, it will provide you a lot more soft tissue detail than CT.
It will show you the difference between, for example, a tumour and retained secretions, so you can identify the tumour mass much more clearly. You can identify granulomas associated with fungal tissue, much better. You can look at the tympanic bullae, you can look at the inner ear, and you can get much clearer images of those than you can of the actual structures within the inner ear than you can with CT.
Orbits mandibles, temporomandibular joints, nasopharynx, all soft tissue in areas that are motionless for a period of time, will provide really good MRI, subjects for investigation. So masses in static areas, the neck, the limbs, the pelvis, dorsum of the trunk, you will get phenomenal information. And also for identifying sinus tracts and around the pharynx with a stick injury or in the flank with a migrating foreign body, you can get exceptionally good information from the MRI.
However, it's less useful for the thorax, because the acquisition of these images takes per sequence around about. 3 to 5 minutes, and so there will be motion artefact, and that motion artefact will reduce the amount of information we can get from moving structures within the, within the chest. Yes, you will see changes within the thorax.
We often do see those when we're looking at the, thoracic spine, but it's not the modality of choice. For the abdomen, it can provide extraordinarily good detail, but the closer you get to the diaphragm, the more likely there is to be artefact from motion of breathing, and that is variable and unpredictable. And that makes it difficult because you're using an expensive acquisition.
And you want to be sure that the, information you're getting is going to be diagnostic. So there are instances where you would, do that. You can do it, of course, by gating the respiratory tract, but you can get very good information, from cranial abdominal information, for a diagnosis.
People always say that you know, CT is best for bones, MRI doesn't show bone. That's not quite true. It doesn't show compact bone very.
Clearly, compact bone will be black, as you can see here, but you can look into the bone, and often with pathology, it is the changes in the medulla, the changes in the periosteum that predict the diagnosis of. The conditions. So it's quite feasible to get good information about those changes and we've used it, for example, for humeral fissures, for the use and for osteosarcomas, as we we'll see later.
We need to be aware that there are two predominant types of waiting for MRI, T1 and T2, and these have different characteristics and allow us to identify different types of tissue within the within the brain. This can be added to by contrast media, which can then increase the conspicuousy of the organs, particularly with blood supply or when there's damage to the brain. So MRI assessment criteria are much the same as we would look for with with CT or with radiography.
We look at the normal anatomy, the changes in, in number positions, size, etc. But it's a very good technique for looking at intracranial lesions. So here on T1 and T2, T1 usually gives you the best anatomy.
Whereas T2 will give you the pathology because, water is hyper intense or white on the, the image. So, this is an area of pathology. You can see.
On the T1, that it's slightly hypo intense in this area, but you can see that there's an obvious mass effect pushing over the midline towards the right hand side. And on the T2 here, sorry, on the T2 here, you can see the mass, you can see edoema around it. In the contrast, you can see this ring of enhancement around the mass, which allows us to say it suggests that this is a glioma with destruction of the blood brain barrier around the mass, which allows the contrast to seep in and produce that effect there.
As I say, you can image it in any plane so you can get a three dimensional view of the whole of the tumour. A meningioma here, showing a nice dural tail, will enhance massively with gadolinium because the meninges have good blood supply and outside the blood brain barrier. So they usually enhance fairly homogeneously, as you can see here throughout the whole .
Of the tissue mass, although you can on occasions, get some cystic meningiomas, which can enhance with a ring around them that makes it slightly more complex to identify the type of tumour within the brain. Inflammatory conditions within the brain here on a T2 weighted slice shows a a large hyper intense area within the medulla of the brain, causing some pushing up and the compression of the cerebellum. In the transverse images, you can see the effects of T2, the flare, which then takes out the CSF, so CSF is now black rather than white and allows us to identify the area of hypertensive intensity.
So it's a T2 weighted image, but With the CSF cancel that, giving us the area of hyperintensity more clearly. And then the T1 with gadolinium showing little uptake of contrast in this case apart from the meninges surrounding the medulla showing that this is a meningoencephalitis. The pituitary, of course, is outside the blood brain barrier.
So again, it shows up very clearly, because it will take up contrast, and in this case, it's a very large macroadenoma, in a cat with with hypersommatotrophism or. Or increased growth hormone levels, and we can see that this is having an effect on the cerebrum, pushing the cerebrum underneath the tentorum back into the cerebellum and the cerebellum then out through the cisterna magna, quarterly. But it's not just for CNS for soft tissue tumours, it's, it's really good and identifies the area that would have to be removed with a border to get a good clearance.
So this is a vaccination sarcoma, a very aggressive type of fibrosarcoma that occurs in cats. You can See that it's avoiding some of the muscles, but infiltrating other areas of the muscle. You need at least a couple of centimetres margin to get around this mass.
So this one would be removable. This is T1, T1 with contrast to T2, T2, of course, for the pathology, T1 for the anatomy. Whereas this one is as a slightly smaller area of tumour on the T1 and T2.
But if we look in the transverse images, we can see that it's much more invasive and actually growing into the bone around the thoracic vertebra into the thoracic spine. So this is not going to be removable in this particular area. I've shown, I've suggested that it can be used for, for bone and certainly produces fairly good images.
This was a perosteal osteosarcoma. You can see on the T1 that there's some new bone on the medial aspect of the femur. You can see with the T2 that the pathology is much more extensive than you might have thought otherwise, and with the gradient echo, you can identify it as being separate from the bone, but attached to the bone at that periosteum.
This is not the same dog, but these are some images from a CT with achondroblastic sarcoma, showing the same effect on the bone and the soft tissues, and you can take your choice. Both of those will produce good diagnostic images. One of the things about MRI is it's still in the development stage and that there are new sequences coming through all the time to increase the amount of information that we can get from from the images, and particularly the three dimensional imaging.
These allow us to acquire a block of data that we can then cut in any direction. And we can cut that down to very fine slices, less than a millimetre in occasions, but this shows a subarachnoid cyst that on the 3 millimetre slices that would be fairly standard, You get the idea that there's there's some pathology there, but actually, once you start to cut it finally, you can see the extension of that subarachnoid cyst, and you can cut that in any direction you like. In this image, of the, cervical vertebra, you might see some disc material around here, disc material around here, but what's going on around here?
What's your diagnosis? Would you cut? Where would you cut?
Well, when we do the, 3D, images, we can see that there is a lot of, disc material. As you come back, it passes round over the top of the spinal cord, then comes down and it's coming up from here. So, removing this would be helpful, but maybe, removing this also would be worthwhile.
So trying to get that disc material out to relieve the compression, would be, important. As I say, it's very good for the definition within the inner ear, also for nerve roots as they come out of the spine through the fat, which is bright. There's the nerve root coming out here, coming down there, and we can follow the nerves as they go outside.
X bone allows us to get a lot of information from the bony material more than we had with just the T1 and T2 images. So in conclusion, the approach should be patient selection is very important. Our ability to localise the lesion.
Is of paramount importance. One of the things that we shouldn't be doing with these very powerful techniques is we don't know what's going on with the animal. We'll just put it in the scanner, see what we get out and see whether we can make a diagnosis, because that's almost destined to failure.
The fishing exercise is not going to produce good images of any pathology that is there, unless we can identify where it's likely to be. And when we've identified where it's likely to be, we need to ask ourselves the questions, what information are we expecting to get from this? And what questions do we need to be answered to really help the diagnosis, treatment, and prognosis of the patient.
It's not just to make a diagnosis and the Diagnosis is actually unlikely to be made because it might show us something, but we still have to do biopsies to make a diagnosis. So we need to think about those things beforehand, and we need to choose the most effective technique that is appropriate for the area and that is cost effective. That requires equipment, it requires technique that needs to be perfected, whichever imaging modality we're using, and it above all needs us to be able to interpret the massive amount of images that we have.
And finally, I just point out that the RCVS in a disciplinary hearing in 2008, published in the vet record. So suggested that Mr. X is charged with dishonestly telling the dog's owners that the chest radiographs that he had taken showed no evidence of metastatic tumours, when in fact they did.
And secondly, recommending further diagnostic work, including an MRI scan and fine needle aspirates of the lung when he knew or should have known. That the work was unnecessary and would not benefit the animal's welfare. So do remember with these absolutely exquisite techniques for providing information that we've got to justify the information on the benefit to our patients.
And with that, I'll leave it there. Thank you very much indeed for listening. Thanks very much, Mike, that was splendid.
We'll see if any questions come up. In the meantime, if people want to put down in the chat box where they're listening in from, that would be quite interesting just to see who we've got on the line today. I hope you've all managed to find your way here either by the Zoom link or by going through the exhibition, and yeah, we've certainly got some time if people can stay on to to answer any questions, so do let us know where you're, Listening in from.
That's in the chat box and then if you've got any questions, put that in the question answer box. While we're waiting for that, Cornell said he's listening in from Romania. Sally from Switzerland, Georgia from Zimbabwe, so a few of them coming through.
We've got Roberto asking the question, very interesting, thank you, . He's just asking, is there special software for producing the 3D images of the CT or is it provided with the CT itself, or do you have to get something extra? OK, that's a very good question.
Most of the CT providers will provide you with software that can help you develop those images. Some of the older machines that may be limited, but there are Diom viewers that will all, be able to produce those sort of images. Most, I would say, radiologists tend to use Horos, which is a freeware for the Apple Mac, and it provides all those facilities to generate those those sort of.
But there are paid versions as well. There's some that are more easy to use than others for the generation of those those 3D images, but you need to have a good viewer to be able to really get the best out of the DO images. Great, thank you.
We've got Finland and Ireland and Zambia coming up and Scotland as well, so great to see people listening in from from lots of different places. Fascinating to hear that EMI were the first to create a a CT scanner as well, they obviously decided music wasn't enough for them, they went into other areas as well. I think it was the opposite really, they, they sold off their their medical .
Inventions I think. Did they, OK, and then the, the . The MRI Semen seems to be one of the big companies, but who actually.
Invented it, do we know? One of my trivia questions here, Mike, I've put you on the spot, haven't put me on the spot. I don't think that it's not somebody like Godfrey Haunsfield who obviously, you know, because he put his name to the units was identified.
I mean, MRI has been used for spectroscopy for a long period of time, and I think it was, it was only when the computerization became feasible to generate the images that . You know, most of it is not the magnetic field, it's the software that goes with it, that makes the images so, so beautiful. Fantastic.
Let me see, yes, we're putting in the, full VC 2021 event schedule there so you can see what else is going on at 1 o'clock, or is it 12 actually, Catherine, is it 12 or 1? Let me just. See, we've got our next webinar which is on sustainability in the veterinary practise, which I think will be really interesting, and we've got another webinar at, yeah, 1 o'clock, for the webinar this afternoon and then one at 7 as well.
So, lots going on and of course we've released a lot of content this morning, so you can go in and have a look around as well, and I hope you er managed to find all that OK. There's also a, a post session survey if you want to do that. And I think we've also sent you a link directing you to the vet exhibition, which is, Coming together and well worth a look at if you haven't already.
Looked at that. Let me see if there are any questions. Doesn't seem to be anything coming through there.
Mike, again, probably an awkward question, was the, was the oxygen so that in the MRI was that at Cambridge or have you managed to take that photograph from somewhere else or don't you want to answer that question? It wasn't at Cambridge, but I don't want to answer the question. I, I must admit, you know, again, being a simple dermatologist, I didn't realise they were quite as potent as that, but, you certainly don't want those sort of things flying around the .
Exam room, do you? Absolutely. And you can think what speed a pair of scissors would get up to, you know, if it had a pointed edge caused quite a lot of damage, yeah.
Yeah, it's really interesting to know. I don't think there's any more questions. Really enjoyed that mic, as always, you've made it really clear even to a simple dermatologist where we use one or the other.
So thank you so much. They, they do just add so much. But as you say, if, if we use any of these tools or any blood tests or anything, just because we're guessing and we have no idea what's going on, we perhaps won't get the results we hoped for.
No. Thanks again, Mike, thanks everyone for listening and hopefully see you all on at one o'clock for the webinar on sustainability. Take care, thanks everyone, bye bye.
Thanks Mike. Bye.