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IMG Radiology Series: MRI



In the follow-up to their radiology series, the team looks at understanding MRI scans. Led by Dr. Hansen, a junior doctor from South London, participants will delve into the basic principles of MRI scans, how they differ from CT scans and X-rays, and how these different imaging modalities contribute to understanding patient diagnoses. The presentation will cover some rudimentary physics crucial for understanding how MRI machines work, and will go into detail about the types of sequences used in MRI, including T1, T2, and Flare images. The session will mostly focus on brain MRI scans, illuminating some of the common pathologies that could be identified through this method. Overall, this seminar from Dr. Hansen and his associates will equip you with foundational knowledge about MRI scans, taking your diagnostic skills to the next level. Suitable for medical students and junior doctors interested in radiology.
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  • Basic principles of MRI
  • Interpretations with examples
  • Key uses of MRI in medicine

Learning objectives

1. Understand the basic principles of MRI imaging and how images are produced. 2. Learn about the different types of sequences in MRI imaging like T1 and T2, and concepts like flare and contrast. 3. Familiarize oneself with key MRI terminologies and understand the differences between hyperintense and hypointense signals. 4. Gain knowledge about the construction and function of an MRI machine, specifically the elements of the magnet, coils, and computer used in the scanning process. 5. Become capable of understanding how the magnetic field and hydrogen ions interact within the body during an MRI scan.
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Computer generated transcript

The following transcript was generated automatically from the content and has not been checked or corrected manually.

Hello, everyone. Thank you for joining us today. So uh we have to do another lecture in our radiology series and we are very happy to have Doctor Hansen today to present us the MRI lecture in the Radiology series. And if you have any questions, please write them in the chat. As this platform doesn't allow you to speak with. You can let them in the chat and Doctor Hansa will later answer them. So, thank you for joining and I'll let Doctor Hansa have the stage and you can begin the presentation. Thank you so much for joining us today. Thank you very much, Yale. I really appreciate your introduction and uh welcome everyone who's here. I'm just gonna share my presentation with you guys. OK. Uh Perfect. Amazing. So uh just a heads up from everyone who's here. Can you guys see the presentation? Yeah, we can see it. It's perfect. I perfect. Thank you so much. So, thank you. Um So as you said, my name is Hamza. Uh I'm a junior doctor and I work in er London or South London uh in specific Croydon. Um For those, those of you who are familiar with uh London and it's a pleasure to be here as always. Uh I graduated from the Czech Republic in 2020. Uh I studied in Olo at Polak University. Um So I'm very impressed by uh the UI MS team in particular. Um They want to see amazing people so well done to all of you guys for uh organizing all of this uh for me and my colleagues presenting this series. Um So today we're gonna be focusing on MRI scan. Uh And we're gonna be looking at some of the basic principles to understand MRI scans. Any questions uh Please feel free to ask and I will try to answer them to the best of my knowledge. Um You've already come across some imaging modalities including uh CT scans and x-rays that we've talked about in the past. Um MRI scans work on a completely different basis. And I think uh for our level, your level as medical students and also uh for most junior doctors, uh if you are interested in radiology, you can always go into a little bit more detail than what we're going to go through today. But today is going to be a very brief uh basic but um uh important presentation on the most fundamental principles of understanding how the MRI scan works and how images are produced. So once again, I'd like to say many thanks to UI M Reuber Emergency Society of Pleur University who have also put in lots of effort in uh to creating this program. Uh And also to my colleagues who are in this program with me and also presenters. So, Doctor Ti Zakar and Doctor Kartik go from Cro University Hospital. Um and uh our own very own consultant, radiologist, Doctor Paramus Brown, who is overseeing the whole series. Um So thank you very much to all of you. So, the the key objective, as I said is to learn the basic principles of uh MRI imaging. Um we are not clinical radiologists. So, uh you know, if you have any uh questions, we'll try to answer them as well as possible. And also um we will try to make it as fun as possible for you. OK? But uh if you do want to go into more detail, more than happy to provide you some resources or even uh some good places you can check out. Um And uh any questions that you have, I will be happy to help. So, a small overview of this presentation is we're gonna go over some basic uh physics. Uh This would be great for those of you who enjoyed physics at um school. I guess that you don't really cover much physics in medical school that I remember anyway. Um But uh if you like it, that's great. If you don't like it, you might not like this topic as much. Uh But I think it's important um to have a good overview of the physics. Background uh for MRI scans because without understanding what's actually happening, uh you won't really understand the basic principles like T one and T two imaging. Um So it's important to go with the basic physics um that leads us on to the next point which is the different types of sequences or imaging that we have in MRI. Um So T one T two, we're gonna talk a little bit about flare and what flare is and contrast. Uh And finally, we're going to be looking quite a lot at the brain. That's probably the most common type of MRI scan that you will come across. But you may come across other types during your medical school career. For example, soft tissue imaging, musculoskeletal imaging, uh MRI in the context of M RCP or magnetic residence cholangiography. So um there are lots of different uses for the MRI, but we're going to be looking at the brain in particular for today. So we're gonna talk a little bit about the key terminology. Um Now, in, as I said before, X rays and CT scans, we talked a little bit about the terminology we used. There was uh opacities or lucency in tons of x-rays or in, in the case of CT scans uh density. OK. But when we talk about MRI scans, we talk about intensity of the signal. So hyper intense and hypo intense and that is comparing the different body tissues together. OK. So go into the imaging in a little bit more detail later on. But essentially, we have an image there just to illustrate this particular concept. Um in the first image uh what appears brighter, what the arrow is showing essentially in the brain or cerebral tissue uh is a hyper intense signal. OK. And, and the reason why I would say it's hyper intense is because it presents as brighter than the surrounding tissues, right. Um In comparison, in the second image, you can see that actually uh in the same area, there may be some darker type of tissue and we refer to that as hypo intense signal. All right. Now, um the intensity of the signal coming from a specific tissue varies on a number of different things. It varies on the composition of that type of tissue, the age of that type of tissue. Um uh and also um that is important in identifying things like specific pathologies. OK. So if you're looking for specific pathologies, uh and you want to differentiate between different types of tissues, um understanding the type of signal that's been given off is important, you can also use other techniques to enhance uh particular type of um uh signals. OK. But we'll talk about that a little bit later on. So the basic components of an MRI machine uh for those of you uh who are here, um does anybody know the function of any of those three particular um uh components of the MRI machine. Um OK. Um So we've got a couple of different types of components in the MRI machine. We've got a magnet, uh We've got different coils uh And we've got a computer or essentially a scanner. Um And uh or a part which is a part of the scanner. Um And they all work together to essentially produce an image. OK. And that's your MRI image. Now, the whole, the basic principle of how an MRI machine works uh is essentially based on uh magnetic fields. OK. And you're essentially creating an external magnetic field that will affect the body. We're gonna talk a little bit about how that is in a, in a minute. Um But in a nutshell, the body er is made up of a lot of water, roughly about 70% of the body is made up of water and water contains both hydrogen and oxygen. As we know, the hydrogen aspect er is essentially a a proton or H plus ion essentially. Now, a magnetic field can affect that hydrogen ion by affecting the way it spins and also the way it aligns itself. OK. So it will align essentially in the direction of that magnetic field. So the whole point of the magnet which is point number two is essentially to create the magnetic field, we also have what's called a gradient. And the whole point of that gradient is to break that field into smaller parts which are focused on the body or different parts of the body. Er, and as we spoke, the managed peels will affect the hydrogen protons all at all er around the body. Next, we have what's called the radio frequency coil or the radio frequency pulse. And we will talk about the effect of the radio frequency pulse in the next couple of slides. But essentially, once again, it changes the way hydrogen protons act in the body. And once the hydrogen protons start to lose the effect of that radiofrequency pulse, we use those timings to determine what kind of image we're looking at. So we if it's at one or T two weighted image, but as I said, we'll come on to that in just a minute. Um And finally, the computer in the scanner essentially receives in the form of a current, uh it receives uh information which then turns into an image and that is how we see the whole MRI image. OK. So the main key concept in this particular slide is essentially that an externally applied magnetic field um is created and it it affects the whole entire body uh which consists of a lot of water. OK. Um And we can measure the strength of that magnetic field. So usually the unit is tesla uh and it's usually between about 1.5 to 3 teslas is being the strength of the magnetic field. So we spoke a little bit about this magnetic fields and hydron. Uh So in the first image, we can essentially see that the um hydron are all moving in different directions. And the key term here is vector, there is no net vector or net magnetization. In figure one, they're all moving in different directions in in in in opposite directions and against each other as well. Whereas if you essentially expose them to an external magnetic field, they will, most of them will align anyway, with that magnetic field. As you can see, there's a couple of them pointing in the opposite direction, but most of them are pointing in the direction of the magnetic field. So what happens um to the energy of that hydrion? Does anybody know what we would refer to as a low energy state or a high energy state? So in terms of the first image, we refer to that as a low energy state. OK. And the second image we refer to that as a higher energy state, right. So when we expose hydrogen ions uh to a radiofrequency pulse, uh it causes a particular effect on the hydrogen ions. Um just to keep it simple, uh you'll see in this image here that there's different types of axis, you've got the z axis and the xy plane with the xy axis. All right. And we use this to demonstrate the effect of the radiofrequency pulse on hydrogen ions. So when the field is externally external magnetic field is applied to the hydro ions, they will align across the z axis uh in one particular direction as you can see in take a while once the radio frequency pulse is applied, which is in radio frequency, which is in image two, you can see that in image three the net magnetization changes, changes to the xy plane. All right. So there's a movement of the net magnetization. OK. We refer to that as in phase and that's important to understand because over time, when there's no uh externally applied magnetic field or radio frequency pulse, the hydrogen ions start to lose their position in, in phase and they go back to being out of phase. And that is a very specific time that we um that, that is important when looking at MRI scans. OK. Um So the term that we use to this change in fields is usually called uh flipping uh of the of magnetization uh into the xy plane. OK. So next, we're gonna talk about something called t one relaxation time. And uh we talked in the previous slide about how it moves from the Z axis to the xy axis. And over time, this flips back to the Z axis. So if you want to think of it in the opposite direction to this arrow here, which is a curved arrow showing movement from the Z to the xy over time that reverses and it goes back to the Z axis. And we say that that is transverse to longitudinal relaxation. So transverse to longitudinal. Uh but like what this image is showing here essentially. OK. So if we focus on the red arrow, it's going from the xy plane to the Z plane. Now, this is an important time, different tissues have different times and we call this the T one time essentially OK to T one relaxation time. Uh And when we image tissues, they will present differently on T one weighted images um as a result of this particular time and the two tissues or two types of um er matter that we look at essentially is water and fat. We're going to talk about how those present a bit later on. But they have different timings when it comes to T one relaxation time and therefore present quite differently. OK. The second concept is uh when we look at T two relaxation time or T two time essentially. And that's called the transverse relaxation. All right. So in the first image, if we focus on the circular, the white circle, essentially, we can see a particular arrow pointing in in a particular direction. And going back to the beginning when we talked about exposing hydrogen ions to an external magnetic field uh and a radio frequency pulse, they align in a particular fashion and they pres which means they rotate, but over time, they lose that. And what happens is they start to move around rather than being focused in one particular direction. And that's what you can see happening in the white circle as we go across in time. Uh So this particular time is what we call transverse relaxation. And is important when we look, when we are looking at T two time or T two imaging essentially. So those are the basic concepts when it comes to T one and T two imaging. So to recap T one imaging essentially is transverse to longitudinal and the time that it takes for that to happen, whereas T two is transverse relaxation time. So fat and water present differently in T one images and T two weighted images. Um And we're gonna talk about a comparison of uh fat and water to other types of tissues coming up in just a minute. But essentially, the key thing to note is that in T one images, fat appears brighter than fluid or water, essentially a as it has a higher er intense signal or a more intense signal essentially. Uh And you can see from uh the graphs as well that basically fat has a shorter T one time or T one relaxation time and T two time as well in comparison to water or fluid. Um the effect of this is different in both uh in both types of images. So in T one weighted images, the fluid appears to be darker as compared to areas of fat which spread to be brighter. But in T two weighted images, the the effect is quite the opposite. Uh if you want to see things like cerebrospinal fluid or even sometimes acute uh uh bleeding or uh strokes. Uh So you can get the blood, for example, uh T two with images would show uh the fluid or water being brighter than the surrounding fat, which is in the uh cerebrum or the brain tissue. So, as I said, this is a uh comparison essentially of different types of uh tissue. So, water uh has the longest time in T one and T two as compared to fat, which is significantly less, but the effect of them is slightly different. Essentially, you've got other types of tissue here as well. So, muscle, liver, for example, which are greater than uh fat. Um and you've got uh type particular types of proteins, for example, that will be a lot less. So the type of tissue you're imaging will have different timings when it comes to T one and T two. And as a result will appear differently on the MRI scan. So, uh we've got an example here uh just to uh show something different rather than the brain, but we're looking at the knee here essentially. So I said MRI scans can be used to image um a lot of different types of bo body tissue, er including musculoskeletal imaging. Um So we tend to do an ultrasound first uh and then progress to an MRI if need be. But um MRI is quite commonly used when it comes to knee problems or even shoulder and joint problems. So in the first image, which is at one weighted image, you can see that the fluid uh in where the synovial capsule is and the joint uh essentially is black in comparison to the surrounding tissue, which is whiter. So fat is brighter than the surrounding fluid. But in the T two weight image, the um fluid is basically uh brighter and that's the same as we saw in this particular image of the brain essentially. OK. So most people explain that the brain tissue in comparison to fluid is brighter or darker, but it's important to understand what that actually means because when you're comparing it to different types of tissues, then um you'll be able to understand uh or differentiate between tissues a lot more easily and understand what's going on. Er when we talk about pathologies, generally, er the majority of pathologies er have a high water content. Er so they will um appear differently on T one or T two imaging. So, in this particular case, we're looking at a tumor which is causing a bit of a mass effect uh and some surrounding edema. So as we said, the T one weighted image, you can see that the fluid is darker in comparison to the surrounding brain parenchyma or tissue, which is made up a lot of fat. And so it's darker and the brain pyma is whiter. Uh but the surrounding edema around the tumor is also darker in comparison to the brain parenchyma. OK, which presents differently to T two where the fat is darker. And you can see the surrounding cerebrospinal fluid, which is more white. Uh and in the middle and the ventricular area is a lot more white. And similarly, the edema surrounding the tumor is a lot more whiter as well. So generally, if there's an abnormality in signals, um and you're look, you're, you're carrying a pathology that most of the time there's a higher um water content or fluid content and it could be things like edema or even bleeding. So we're gonna now talk a little bit about the um uh particular er sequences, different sequences and MRI scans that we can use to enhance particular um er features of the scan. Er So flare MRI stands for fluid attenuated inversion recovery time. It's quite a complex thing, but essentially the whole point is to negate the signal from the uh free flowing, free flowing fluid or in particular the CSF. So you can see in this particular case, the CSF is black. Uh it's more hypo intense compared to the brain tissue. OK. Um And what are the particular examples that we can use this in? There's a number of different reasons why we do flare imaging but um commonly it's used for things like lesions. So, if you want to classify the type of lesion, you're looking at whether it's cortical or subcortical. Um And we're looking at, we'll look at a couple of images later on as examples where flair imaging has been used and we'll talk a little bit about contrast in MRI. So previously, we talked about contrast in CT scans, we talked about different types of contrasts including iodine. But in this particular case, when we use MRI, we use gadolinium. Um And once again, it's used to enhance particular features um which may not be very visible on um non contrast scans. Essentially. Uh you can see on this particular image of the brain that actually in the pre uh precontrast scan, there seems to be some kind of irregularity there. Um maybe a tiny bit of mass effect if you wanna call it that. But definitely some kind of abnormal signal post contrast. Uh there is enhancement of some irregular tissue there or mass in this particular case, which could be a tumor. But given the clinical context of the situation, uh it can be diagnosed and some uh post contrast effects, uh it can cause headache, dizziness, nausea, sometimes patients complain of flu like symptoms. Um And they may also say that for example, they feel like going to the toilet um to pass urine. Uh but there's various different ways that they can present after having gadolinium uh injection uh which is in intravenous. So now we're gonna look at some examples of the MRI uh brain. So remember when we're looking at imaging, there's different planes that we look at imaging in. We got your axial, your coronal and your sagittal. And that's very basic to understand when you're looking at any kind of image. Um it's very important to understand what plane you're looking at things in. OK. And also to understand that the patient's left, maybe your right and vice versa. Um Everything in radiology is very anatomical, of course. So you've got to use the right terminology when uh describing that particular scan or looking at uh whatever you're looking at essentially. So anterior posterior. Uh but um the most important thing here is to know what size you're looking at basically and what plane. So once again, uh we're going to appreciate the differences between what T one waste images look like versus what T two waste images look like uh on a brain MRI. Uh And we can see that there are uh very clear differences in the ventricular system which is, which contains the CSF and also CSF surrounding the brain sulci are very hyper intense with a higher signal in T two weighted imaging as compared to the T one was imaging. And in the T one weighted imaging, the brain tissue which mainly consists of fat has a higher intensity of signal as compared to T two weighted imaging. Um And of course, you can go into more detail and talk a little bit more about the anatomy, but we're not going to focus on that just yet, I think the main point of this presentation is to identify and appreciate the key differences between uh the different types of sequences or scans that you can have in MRI. So it gives you a beginner's um a foundation essentially to go from. Uh we, we spoke about flare earlier on and I just wanted to include this image to appreciate what it looks like in comparison to the T one and T two imaging. Uh So, as I said, we essentially um uh change the er intensity of free flowing fluid or CSF essentially, as you can see here, it's actually become very dark uh or black essentially in this case, which is somewhat similar to the T one imaging and it looks a bit like at one imaging, but actually, it's a flare, it's a flare up sequence essentially. And in comparison to T two, which is hyper intense and there are other types of sequences which include um T two star or DWI for example, but they can be used to enhance things like blood on imaging um or even uh certain other pathologies like masks as well. So we're gonna look through a couple of examples now. Um And we'll see what you guys think. I think we've got two comments here. So can we touch an indication that you want to? Yeah, sure, of course. Thank you very much. Uh And the second question is, is there any degree of the property below that contrast. Be safe. Sure, thank you. Appreciate that. Uh So, um yeah, so T one and T two and why would we would uh why would we would use one over the other? Um So essentially, it depends on the type of tissue that we're looking at. Uh And it depends on, for example, if we're, we're trying to differentiate between different types of tissues. So, in the case of T two, if you want to look for things like uh bleeds or fluid, uh T two imaging may be better. Uh Whereas if you're looking, if you're not querying, for example, potential bleed. Uh So it really depends on clinical scenario essentially. Um But T two imaging is better to look uh is better used when looking for uh pathologies that include uh things like bleeding, for example, or fluid essentially. Uh you can see a little bit more clearly on that. Um But actually a lot of the time they have both scans done or even a flare scan and combination as well. So it really depends on the clinical indication er and the presentation of the patient as well. Um And the second question is, is there any degree of nephropathy uh below which gad contrast can be unsafe. So, uh generally speaking, um I think we have to check the renal function of the patient before administering gadolinium. Um I'm not too sure uh particularly about the degree of nephropathy that the guideline and contrast may cause. Um but uh but that's something that we can look into and, and, and, and let you know. But, yeah, I think the uh generally speaking, uh we have to look at the uh EGFR and the renal function or the renal panel of the patient before providing contrast. Um And if, for example, they uh are not able to have it for whatever reason, then it may be because of that. Um OK, so we move on to the next slide. Yeah. OK. So, uh Right. Um So we've got a first pathology. So we've got an 85 year old male, uh which presents with sudden right sided blurry vision and headache and he feels quite uh nauseous as well. Um He has a past medical history of atrial fibrillation hypertension and he's got a large prostate essentially. Um So he's come in, you've seen him in the emergency department. What other questions do you think you're gonna ask him? Does he take any anticoagulants? Great. Fine. Fantastic. Um Good. So, yeah, you can ask him about his pharmacological history. Um I think the key things to ask here is how sudden his symptoms have been. Um And also if he has any problems uh with his limbs or his a neurological exam essentially, OK, because you might be thinking of a couple of things and what are you thinking of when uh when a patient presents like this? Yup. Trying to. Yeah, thank you. Mhm. Stroke? Great. Fantastic. So, in terms of exams, we talked a little bit about what we'll do. So we did, we do a basic neurological examination. Uh, let's say he's had this, uh, nausea or blurry vision for a while, at least a couple of days you can do, for example, the hints exam as well. Um, so, uh, that's that, uh, and, uh, in terms of investigations, so you've done a CT head, for example. Um And there's a small pathology in the CT head. Uh And you've spoken to a stroke specialist as to what that might be. So you've admitted him for an MRI scan and this is what the images of the MRI scan look like. So let's talk about the first image on the left. Uh Do we think that's at two weighted image or at one weighted image? What do we think? Bye. OK. Great. And uh why do we think that this is at two weighted image? Uh What can you tell me about the uh what, what essentially enhances uh signal and what has a lower signal essentially? So the fluid in the ventricular areas at a higher signal or lower signal in comparison to the surrounding brain tissue? Yeah, hyperintense signals. Great. Fantastic. So you can see at the bottom in uh towards the occipital area on the left side of the patient that there's a small abnormality we're talking about here essentially. OK. And uh the second image is actually what we refer to as a DWI type sequence. OK. But it enhances that there's actually a little bit of blood. So this is an infarct or a bleeding essentially. And uh it's a stroke, OK. So that's an acute stroke that we're looking at and just to compare. So we have um uh in comparison to patients who have presented with previous strokes, you can see that actually uh previous strokes presents us quite differently. So it's more hypo intense in compared to the hyperintensity that we just saw. So, pathology two, we've got a 30 year old female with a two month history of confusion, memory loss and headaches past medical history. She's got fibroids, she's got some ovarian cysts. What other questions would you ask? Ok. So she's presented with a bit of confusion, memory loss, headaches. Uh What, what, what are the other causes? What could could uh also cause these symptoms? Uh If we're not thinking about um anything related to the brain, for example. So it could be endocrine related, it could be thyroid related. Uh It could be a number of different things, it could be related to the menstrual cycle, for example. Um So uh there could be a number of different causes for these symptoms, but because we're focusing on the brain at the moment, uh there's a particular diagnosis that uh she has. We're gonna talk about that in a minute. Does anybody cerebral Mets. OK. Yeah. So there's one particular potential here. Uh Any other guesses as to what might be causing it? Meningioma? Great. OK. Uh So you do an examination and you find that she's actually presents with hyporeflexia. Uh And uh uh she's got a slightly abnormal uh some cerebellar signs as well. Uh What do you think might be going on here? So you do an MRI scan and the MRI scan presents with these images. OK. So you can see there's some lesions uh across not just the brain but the uh spine as well. OK. So um these particular areas of abnormality are actually uh uh multiple lesions in multiple sclerosis. OK. So this is a patient who was presented with multiple sclerosis. Uh And in this particular um image in the first one on the left side, this is at two image. Um and we're looking at a flare image on the right side. OK. So, using enhancing uh the intensity of those particular lesions to see them a little bit more clearly. Finally, the third one. So we have a 56 year old male, um previous smoker, six months of night sweats, weight loss. Now, hemoptysis, he has a persistent headache. He's got a past medical history of CO PD. Um You've done a basic X ray and on the X ray, you can see a small abnormality. Uh and you think to yourself, what might this particular abnormality be? You do a CT thorax. Um And that ct thorax shows uh a very suspicious looking mass. Um What do you think might be going on as to why he's having his brain, brain symptoms? I think we've already talked about this actually. Um But uh essentially we're looking at what, what might be going on metastasis. So, uh yeah, so this is a patient who may have a pulmonary or lung cancer essentially. Um And he, you do an MRI scan because he's presented with those headache symptoms. Um And you can see that there's some lesions here. OK. Uh And here are those lesions basically um enhanced post contrast. OK. So uh basically, these could also be um uh the the tuberculosis claws are present in a similar way. Uh But in this particular case, these are metastasis from a lung primary essentially, right? So, um if you want to learn more about those uh particular um topics that we've discussed, I'll recommend checking two channels on youtube. So, navigating radiology, which I've used as well um for this particular lecture uh by Dr Rajesh uh Baa and also uh Leicester Medical School Radiology as well. They've got some nice videos on brain MRI. Uh Radio pia is a great website for those of you who are more interested. Uh And then we've got uh some books as well if you wanna have a look at them. But uh yeah, that brings us to the end of the lecture. I can see we've got a couple of questions here as well from uh doctor Hey daddy. Uh so, oh wow. Uh late in the hospital between active disease and chronic scarring, was it better when coupled with pet scanning? Uh to be very honest with you, I think your radiologist is probably in better position to answer those questions. But what I can say is when it comes to um uh cardiac imaging MRI uh imaging is very important, especially looking at things like uh atrial fibrillation um or for example, cardiac scarring post, uh myocardial infarction. So, pet imaging, you don't really, I mean that's more nuclear uh side of things. But pet imaging you don't really use unless you, you are thinking of, for example, uh tumors or things like that. So uh you can use them in specific cases. Um But uh but in, in the case of uh cardiac history, a patient who has cardiac history, for example, uh I think that uh it's very, it's very specialized essentially. Um But uh MRI uh imaging in terms in the, in the, in terms of context of the heart is usually used to look at things like scarring and fibrosis as a result of uh myocardial infarction DWI. So DWI is a type of um er sequence essentially that can be used for enhancing particular features. Uh So we talked about the previous uh slides. Uh Let me just get back to some here. Um Yeah. Yeah. So uh DWI can be used to basically enhance particular features like bleeding, for example, or even an acute stroke as this in in this particular case. Um So yeah, there are different types of sequences but we can go into more detail um in the next uh lecture if need be if you guys are more interested. Thank you very much. I really appreciate it. Thank you, Doctor Hamza. And if you don't mind, let's just wait like one more minute to see if there are more questions and if of course, thank you so much for the amazing presentation. Thank you for us today. Oh, I see. There's a new. Oh, thank you. Ok, thank you. Yes. So that's perfect. So I think we can finish it off. Thank you very much again for joining us for the presentation and thank you very much. I appreciate it. Goodbye.