 Hello, everyone. I'm Dr. Rajesh Chauval, consultant at Jaisalok Hospital, Mumbai, and Thane Artisan Center. And it's wonderful to be back on Indian Radiology's channel, an extremely unique educational platform. And today I'm going to be discussing liver elastography. I have been very fortunate to have conducted workshops at RSNA, as well as a lot of other conferences on this topic. And this is where I've realized the common problems that people face. So I have made this presentation, keeping in mind the common issues that people face as well as a practical approach. I hope you really enjoy this. Hello. So today I'm discussing with you liver elastography and just a brief background of what the problem is. There's a huge prevalence of liver diseases in India. And what is assuming epidemic proportions is a non-alcoholic factor in the disease, which can affect almost 35% of the population. And this is a problem because these livers are going to behave very similar to the alcoholic liver diseases. So irrespective of whatever is the predisposing condition that causes the chronic liver disease, the pathology almost remains the same, where we have development of fibrosis due to the deposition of collagen within the tissues. And this eventually leads to cirrhosis where the liver becomes very nodular and there's architectural distortion. Now we know that cirrhosis is a clinical problem because this can lead to portal hypertension and even conditions like HCC. So the key over here is to detect fibrosis at a very early stage because fibrosis is potentially reversible and we may be able to halt or even reverse liver damage. Now the problem is detecting fibrosis is not very easy because patients remain asymptomatic until the final stages of the disease. And even in case of cirrhosis, a good number of them can be compensated and will remain asymptomatic for a very, very long time. So all this while the gold standard of really detecting the spectrum of cases was conducting a liver papacy and pathologists came up with various scales, various kinds of grading to detect or identify the severity of fibrosis. And the commonest one which is used is a metabolic scoring which classifies the fibrosis into mild moderate CVR and classifies it as F0, F1, F2, F3, F4. The problem with liver papacy we know is it's not something which is very easy. There can be a lot of problems with respect to the sample size, with respect to the reporting of the thing. And whatever we say and do, it remains an invasive procedure with a large share of complications. So this cannot be really used as a screening tool on a day to day life. So what we really need is a non-invasive tool which can do a good assessment of the liver fibrosis. It's very easy to use, it's reproducible and can be used as a screening modality. And this is where our elastography pops in. So elastography for all practical purposes is like an imaging equivalent of palpation. What we are trying to really assess is whether the pathology has made the tissues harder or has it made it softer? So there are different types of elastography which can be used in the liver. You have transient elastography or what was popularly called as fibroscan. You have MRI and then you have the ultrasound-based RFE techniques which are the point shear wave and the 2D shear wave. Fibroscan if you look at it has a fair share of problems. Its basic limitation is that there's no anatomical reference image of where exactly we are scanning and this can lead to a lot of problems. As far as MRI is concerned, yes it is good, it can give a very good assessment of almost the entire liver. You can use a whole lot of measurements to assess and give you a whole lot of information but the problem remains that it's quite expensive. It is very time consuming and we need specialized equipment to do it which is not necessarily cheap. And this is where ultrasound elastography walks in because it uses our routine machines, it uses our routine probes. Yes you do need a software upgrade on the machine but it is nowhere as expensive as that in an MRI. The advantages of using ultrasound shear wave is that you have an anatomical reference. So you know exactly where you're measuring and you can avoid a whole lot of fallacies. It is not so influenced by body mass index or a cytos, there's good reproducibility and as a result of all this we get a very good accuracy. So what we use in ultrasound is the shear wave technique which basically gives us a quantitative analysis of the fibrosis. So what happens is first you have this induction pulse which comes through the tissue, it generates shear waves within the tissue, okay perpendicular to it. So these shear waves disperse through the tissue then you pass another detection pulse which helps to detect the rate of progression of the shear waves or in other words gives us the velocity of the shear waves in the tissue. And this is what we are using for our assessment. So this is very similar to dropping a stone in the water. So when we drop a stone that's your induction pulse. What is generated are these ripples which is the shear wave and we detect the velocity of these ripples in the water. So what is the rationale behind the whole thing? Normally the liver is a very viscous tissue, it's not really favourable for favourable to progression of the elastography waves. But when fibrosis sets in the tissue becomes very hard and as a result of this there's rapid progression of the waves through the tissue. Now we have this bufum guidelines which have come out in July 2018. I would recommend everyone to go online and check this out because this is very very useful. It gives us a good indication of how we should do it and how we should interpret our elastography studies. So there are a couple of three requisites that we should follow when we do elastography. First of all the patient should be fasting for 6 hours. We should not do the scan immediately after the patient walks into the clinic. Let him wait for some time and then do the scan in a little while. We need to know what type of disease we are looking at. We need to assess our lab reports. We need to understand what LFTs are. We do a quick survey on ultrasound we see for portal hypertension, see for acitis and what is also important is ruling out CCF for acute hepatitis. So which segments do we analyse? We have to leave out the left lobe of the liver because this is bound to get pulsations from the heart so it's going to get artifact. So what we can analyse is segment 7, 8 and 5. This is what the guideline suggests and what is also very important is how we position the patient. We need to position the patient in the supine or semi-decubitus position with the hand above the head as this increases the intercostal space and what we need to consider over here is that we need to get a very very good 2D image. If we do not get a good 2D image the propagation of shear wages not going to be good and we are not going to get good readings. So we go in an intercostal space we avoid our rip shadows we get a good 2D image and then we can proceed with the study. We need to ask the patient to do a shallow breath hold don't do a deep inspiratory or deep expiratory this is going to hamper your image as well and what we need to do is target or keep this focus roughly 2 centimeters below the capsule because the sweet spot of the RP is roughly around 4 to 5 centimeters from the transducer surface so this is what we need to target. So there are two types of shear waves which are available on the ultrasound machines one is the point shear wave which has been there for some time and what has popped up over the last two three years is the 2D shear wave. So let us discuss the point shear wave what happens in this is you get this small box which is roughly around 0.5 to 1 centimeter square we should place this box like I said 2 centimeters below the capsule and this box has to be absolutely perpendicular to the transducer as well as the capsule of the liver as we can see over here. Also we have to ensure that the box is not placed within vessels or large baleary radicals so then we ask the patient to do a shallow breath hold and we acquire our readings. The guidelines state that we should take 10 readings at the same spot and that is adequate for our interpretation. So what we get is a reading like this in meters per second you can also configure your machine to give you a reading in a kilo Pascal's and both are absolutely right. Now coming to the 2D shear wave the advantage over here is that we have a much larger box as we can see over here which is roughly 20 centimeters square and we can place multiple calipers within a single box. So this calipers is what is going to give you the readings so we place a caliper within the box and we get a reading over here. So within a box you can maybe take two or three assessments and what this helps in doing is reducing the number of samplings that you are going to be taking. Again we have to be careful of how we are going to do it we need to avoid the vessels as far as possible we have to avoid large baleary tracts but there are ways of avoiding these problems when it comes to 2D shear wave because what we have on the left hand side of the screen is something called as a confidence map. So this confidence map basically tells us that we should take the readings in areas where it is green which is represented as 100% on the scale and we should avoid areas which are red which comes as 0% on the scale. So your confidence in the red area is 0% whereas your confidence in the green areas is 100%. So for example if the vessel pops in like it has in this case it reflects as a red area and we know that we do not want to take readings over there. So this is a very good assessment of how is your elastography image whether you should take your readings in this image and if yes in which area you should take it. The other advantage of having the 2D shear wave is that we can even take the readings on a frozen image or even a retrospective loop which is not a luxury that is available in the point shear wave because we have to take live readings over there. The other factor that we need to consider is look at this IQR upon median. So this IQR upon median should ideally be less than 30% and actually as close to 0% as possible. So this is how you get the reading. You have this large box, you place these calipers, you can place multiple calipers and you can see that you have multiple readings within a single box. You can alter the size of the caliper, you can play around quite a bit with these images. Again the importance of confidence map I would just like to lay stress on it. You can see that there's a large vessel passing through over here which reflects as red. So you know that you do not want to take readings in this area and again the interquartile range like I mentioned we need to ensure that the interquartile range is less than 50%. So these two factors are a very good quality indicator of your assessment of your lastography image and can help you to guide where you should take the readings and where you should not. Once you are done with the readings, how do we interpret it? Well we go to a report page and there's this huge amount of data which really pops up as you can see over here and forget about everything don't get too confused. All we need to look at is this median velocity over here which is what we are going to use for reporting and the IQR upon median over here which is a qualitative assessment as I have described before. Traditionally we have been trying to correlate our elastography values with the pathological scoring of meta-vit. So we have said that when the velocity is less than 1.37 meters per second this is classified as f0 f1 and that translates to clinically non-significant fibrosis. When we have a velocity more than 2.2 meters per second this classifies as a f4 and some bit of the f3s and this corresponds to basically advanced fibrosis or cirrhosis and anything in between is considered as f2 and f3. So like I said what we are trying to do is correlate our elastography findings with the meta-vit scoring but this represents a huge problem as you can see in the graph because there's a lot of variation with respect to the probability and if we have readings which pop up in between over here it's very confusing because we cannot say that it is definitely going to be an f2 or f3 reading and this is a big big big problem. So the consensus conferences which have been conducted it's been decided that the best use of elastography is to sort out the extremants of the spectrum so it's very good when you want to detect these patients with clinically non-significant fibrosis or minimal fibrosis which constitutes as 0 f1 and the other end of the spectrum which is the f3 and the f4 which is a clinically significant fibrosis but we should not use it to classify fibrosis which falls within this range. So all this is very confusing so the SRU has come up with a new update it's proposed a new rule of four which should be getting published soon which states that if the velocity is less than 1.3 meters per second there's a high probability of this being normal if it is less than 1.7 and you do not have any clinical science it rules out compensated advanced chronic liver disease if the velocity is between 1.7 and 2.1 it is suggestive of compensated advanced chronic liver disease but we need further evaluation if it is more than 2.1 it rules in a compensated advanced chronic liver disease and if it is more than 2.4 it is highly suggestive of a clinically significant portal hypertension so this is what we should eventually follow going ahead in the future. So the clinical applications if you look at elastography yes we need you can use it to diagnose and rule out fibrosis we can potentially use it to stage fibrosis but like I said there's a little bit of a controversy regarding that because we have been using it very effectively to avoid biopsies to follow up patients and see how they are responding to treatment so just a couple of examples that I would like to show here is a patient with a median stiffness of 1.2 and this was normal a patient with mild fibrosis where the median stiffness was around 1.5 advanced fibrosis where the stiffness is around 1.6 and you can see that in case of cirrhosis the values are going up to 2.3 meters per second. There are some sources of variability which pop in due to in the elastography it can vary a little bit depending on the type of the underlying disease it varies depending on the modality which you are using so ideally we should use the same modality while following it up there can be some variability depending on the machines as well though all the vendors are trying to bring this under single roof and sort out this problem. The major problems that we encounter on a clinical practice is when there is acute flare of hepatitis and congestive cardiac failure because both these conditions can give rise to falsely elevated values so if you're thinking of clinically acute hepatitis we should wait for a few weeks before we repeat our procedure and in case of congestive cardiac failure 2 we are not going to get very good values so it is a problem and this is something that we have to definitely keep in mind so in spite of doing the best that we can there can be certain limitations if we do not get very good ultrasound images it's going to be a problem we may get reverberation artifacts if the patient is not going to be able to breath hold very good and these are some of the limitations when it comes to liver elastography but all in all it's been a very effective tool for using it as a screening tool and definitely it's going to improve in the near future. I hope you like the presentation and I encourage all of you to go back and start using this as soon as possible and at the same time please keep safe and please take all possible precautions while working under the current situation. Thank you.