 Hello everyone, I am Dr. Vijay Vaskarnawari. Today I will be discussing with you about the role of MRI in liver iron quantification. So, MRI known as a biomarker because MRI can prognosticate the particular pathology in liver like iron, fat, fibrosis, equal to that of a biopsy and where you can avoid a biopsy which has its own potential lethal complications and biomarker because MRI gives results almost equal to that as of the biopsy and it kind of gives you a picture where the treatment can be modified, treatment can be assessed and majority of the diffuse liver diseases like I told you, iron, fat and fibrosis can be evaluated with high degree accuracy. I will be approaching the topic of liver iron quantification in the following manner. We will discuss something about iron metabolism, what are the causes of iron overload, how do you differentiate between primary and secondary iron load status, complications of hepatic iron overload, what are the lab markers, I mean if a patient comes to us directly he will not be sent for MRI. There are the hematoma and call this will try to assess his lab parameters. What is the role of lab parameters? Where do they stand today when compared to MRI? Then the MRI proper where we assess the iron overload, basic physics of MRI, standard protocol followed as on today. How do you calculate the parameters which are used by MRI like T2, R2, T2 star, R2 star, liver iron quantification and myocardial iron concentration. How do you report, how do you interpret? You got a value, you got a T2 star value, you got R2 star value, you got T2 you got R2. How do you report, how do you interpret based upon standard guidelines which are given already and then what are the limitations of MRI, then we look at some case studies. If we look at the iron metabolism per se, overall intake of iron in the normal diet is approximately 10 to 20 milligram per day of which only 1 to 2 milligrams is absorbed in the proximal deodorant. This is facilitated by a protein known as hepsidine which is produced by hepatocytes. Whenever there is an abnormality in this protein hepsidine, there is abnormal intestinal absorption of iron, just keep it in mind. Next, once the iron is absorbed in the deodorant, it goes into the plasma and in the plasma, the iron is transported by a protein known as transferrin. So, transferrin is nothing but a transport medium of plasma iron after absorption in the gut. Now, normal transferrin saturation is 25 to 40 percent. When there is excessive iron absorption because of abnormality of either hepsidine or excessive iron intake, then what happens? The transferrin saturation, if it exceeds more than 45 percent, then the non-transferrin bound, that means the transferrin cannot accommodate extra iron. That iron is known as non-transferrin bound iron which is in the plasma. Now, it has to go and get stored somewhere and the first storage organ is liver. So, it has got non-transferrin bound iron, has got high affinity for hepatocytes. It goes and stays in the hepatocytes. If the transferrin saturation becomes more than 75 percent, then a special type of non-transferrin bound labile toxic iron radicals are released in the blood which obviously go and attack the hepatocytes faster. And these are toxic radicals which leads to oxidative stress on the cells, repeated inflammation and subsequently fire forces. So, that means you say that a repeated iron overload status more than 75 percent of transferrin saturation will lead to repeated inflammation, oxidative stress and fire forces. So, this is the basic pathology behind the iron metabolism. Now, iron is stored predominantly as ferritin and if ferritin gets saturated, ferritin is a protein, when it gets saturated, it is stored as hemosyterin which is a separate molecule which forms clusters in the way wherever it is stored hemosyterin. What is meant by iron overload status? Iron overload status is a systemic disorder characterized by high level of plasma iron and accumulation of iron in parenchymal cells in the form of ferritin and hemosyterin. So, we have now known that the plasma iron transported by transferrin and if transferrin saturation is increased, it is over saturated, it goes into the cells and most commonly hepatocytes because the iron has definitely for hepatocytes. In the hepatocytes, it is stored in the form of ferritin and if ferritin gets saturated, it is stored in the form of hemosyterin. And the greatest advantage of MRI and ease of MRI is liver is the main iron storage organ and in the liver, it is stored in hepatocytes and if they get saturated, then it comes to cook for cells or reticular residual system. Number one, number two, liver is the first to show iron overload status in the entire body and it mirrors the iron homostasis in the body. So, that is why in all these conditions of primary and secondary iron overload status, if you look at liver, quantify liver iron, it automatically will try to tell you about iron homostasis in the body, entire iron metabolism in the body. So, that is why that is the greatness of the calculation of liver iron because it tells you about the entire homostasis. That means, if liver iron is very high, that means you can probably estimate that there will be definitely something in your heart, in pancreas, in cellar, in bones, all these places. So, that is why liver iron quantification has got a very major role in assessing the liver, in assessing the total iron homostasis. I have already told you, the transparent what is the transport medium ferritin is a storage medium in the liver, in the predominant liver of iron. So, these two are important. While these two are important, I will come to you when we assess the lab parameters. How to assess what is important in lab parameters? We will come there. I will come there. Hepatic iron overload causes a primary and secondary. Primary is genetic disorder known as hereditary hemocomotorosis. Secondary is haemocytrosis because of iron overload status, sickle cell disease, thalassemia, aplastic anemia, repeated destruction of RBCs linked to iron overload status, all these conditions come into it. Now, one important point, elevated serum ferritin and hepatic iron also occurs in viral hepatitis, alcohol-related CLD, metabolic syndrome, diabetes and NAFLD. This is the point which radiologists have to remember because when you are assessing the liver as a whole, not only iron, assessing the liver as a whole. For example, I have got a patient with NAFLD, alcohol-related CLD. In such a situation, it is known that in addition to fatty change in fibrosis, they also have an important component of increased hepatic iron because of altered metabolism of iron known as ferritin dysregulation. So, this happens in these conditions. So, what you are looking at as a MRA picture on the Dixon images or in the opposed phase images is not only because of fat or fibrosis, it is also because of iron dysregulation. This part you have to reoccur. Increased iron deposition may or may not be associated with hyper ferritin anemia. I will come to that conclusion. I will come to this part in the next set of slides. So, there is a limitation of assessing of plasma ferritin and transferrous saturation because lab parameters are not very sensitive in trying to tell us about the iron-homestasis in the body. MRI liver-iron quantification becomes food-proof method to assess the iron-homestasis. Increased hepatic iron will lead to oxidative stress, inflammation, fibrosis and cirrhosis NASH plus hemosclerosis. That means, non-alcoholic state of death and hemocytosis have a deadly combination. There is increased incidence of fibrosis and increased risk of HCC in these situations. As it is NAFLD has increased risk, it can bypass from CLE directly become HCC, directly can develop HCC. Now, if you add hemocytosis to it, deadly combination. So, increases of HCC can also be there in hereditary hemocomostasis because of elevated hepatic iron content. What are the orbital systems susceptible to general iron overload? Pituitary, thyroid, heart, liver, pancreas and gonads. All these are affected by iron-homestasis. How do you classify the iron-homestasis? Hereditary hemocromostasis because defective HFCG and what are the key manifestations of clinical manifestations of hereditary hemocromostasis, liver cirrhosis, heart failure, bronze diabetes. They used to call earlier bronze diabetes because of skin pigmentation because of the deposition of the heavy metals. Now, transfusion hemocytosis can occur because of repeated blood transfusions in beta thymine major, in sickle synthesis, in minor dysplastic syndromes and a plastic anemia. How do you differentiate between memory hemocromostasis and transfusion hemocytosis? What is the basic difference? This is a very important slide for all of you to remember. Primary hemocromostasis is gentrically nearer to effect results in increased intestinal optic. I told you hepsidine is the liver and the liver protein which if it has abnormality automatically there is excessive iron absorption. Now, in transfusion hemocytosis is often iotrogenic due to multiple transmissions or iron replacement therapy. In primary hemocromostasis, the reticular dysplasticism is abnormal whereas in transfusion hemocytosis, RAS is intact. Then in primary hemocromostasis, iron is deposited liver, heart, pancreas and skin. In transfusion hemocytosis, iron is deposited predominantly liver, spleen and bone marrow. So, this point you have to remember because when you are looking at liver, iron, beta thymine, you can also look at heart, quantification of heart, iron and also pancreas. Also look at cellar, look at bone marrow, skin of course you cannot see. So, if you remember that heart is predominantly more involved in primary hemocrosis and pancreas is more involved in primary hemocromostasis whereas in transfusion hemocytosis which is the most common form of hemocytosis which you get to see and which you are asked to evaluate by MRI in transfusion hemocytosis, liver, spleen and marrow these three are mainly. Now, in primary hemocromostasis, hepatic iron is stored in hepatocytes because there is abnormality of RAS, Kupfer cells whereas in transfusion hemocytosis, the hepatic iron is stored predominantly in reticulandrosis, that is Kupfer cells. The primary hemocromostasis is treated with phlebotomy and transfusion hemocytosis is treated with iron chelation. These points if you remember, it will become a good clinical reticulandrosis. This I have taken from a very important article I will share, I will share the details of the article in the next couple of slides. It is an article in 2016 in radiographics as hepatic iron overload status primer for radiologist. This is normal, you can see this is normal hemocromostasis that is primary, pancreas and liver are predominantly involved. In transfusion hemocytosis, liver, bone marrow and spleen are involved. In sickle cell disease, liver, bone marrow involved and spleen goes into auto nephrectomy status. Spleen is small in size, dysmorphic has a low signal on T2. What are the modalities to assess the iron homeostasis in the body? Number one, lack of parameters of serum ferritin and transfer in saturation. Ultrasonic abdomen not very useful. CTS, go to limited, limited extent. In all these iron overload status and hemocromostasis, plain CT scan has an adrenation value more than ATHU 80 75 to ATHU. It is more than that, you suspect hepatic iron overload status. Biomagnetic susbitometry, we are not very comfortable with this. MRA is the modality of choice as of today. Standard of care in many of these iron overload status, especially a transversional hemocytosis. Lab carameters like I told you, serum ferritin, transfer in levels are widely used to delicate the iron overload. When a patient comes to us, first the hematologist will assess and then send to us the serum ferritin and transfer in levels. Serum ferritin, if it is more than 270 nanogram per ml, that means the patient has got iron overload, some form of iron overload. Similarly, transfer in saturation also is done. But the problem is, if serum ferritin elevated, it is not purely because of iron overload status. We have seen in this COVID pandemic that serum ferritin and LDH are inflammatory markers. So, serum ferritin can be increased in all kinds of inflammation. So, that is why serum ferritin is not a great modality to pick up iron overload status. That is why it has got a lot of false positives, especially with COVID pandemic, everyone has got a ferritin is elevated. Now, transfer in saturation again is not very great because it can be decreased. Actually, it should be increased in iron overload status. It can be decreased in chronic iron deficiency, inflammation states, malignancy, uremia, and nephrodisiin problem. So, that is why the biological markers like transfer in saturation and ferritin are not very useful. And then that is why MRA has got a great role, first to play in diagnosis, diagnosis and quantification and follow up of iron overload status, especially iron homoesthesis in the body. What are the MRA methods? There are these couple of MRA methods. We will go into in detail about the main method and then we will just skip through the basic methods. Most simple method is known as liver to muscle signal intensity ratio. Very simple, I will show you in couple of slides. Then D2 went R2 relaxometry. Now, all of us know that when iron goes into the liver, the susceptibility of the liver hepatic cells is very high and automatically there will be low T2 values. And similarly, the R2 values also I will show what is R2, what is T2, I will tell you in a couple of slides. Similarly, R T2 star and R2 star. T2 is a regular phosphine echo technique. T2 star is a gradient echo technique. So, if you use T2, it will take long time. You cannot use breath hold techniques because T2 basically, you know that any T2 you do has to be respiratory gated and it is, I mean there are lot of variations in respiration, movement artifacts and so on and so forth. So, T2 is good, but the problem is T2 cannot have breath hold, you need a respiratory gating. T2 star is a gradient recall echo technique where it can be done in a breath hold. I will show you in the physics why T2 star is more preferable than T2. So, preferred method nowadays is T2 star because it can be done in a single breath hold, single sequence more reproducible, more user friendly. Now, there are other sequences known as a multi-echo GRE sequence which is used to pick up the iron overload. And what happens in multi-echo GRE sequences? When you use this T1 based GRE sequence, you use 6 T's and these 6 T's are ones which will give you results about in phase, out of phase, fat only, water only, protonacy fat fraction and R2 star or iron quantification of it. So, when you give this multiple echoes into the liver, the output is in 6 pattern in 6 forms and among these 6 forms, the advantage of these 6 forms is you can get fat, you can get iron, you can get fat like protonacy fat fraction, you can get iron as R2 star. What is R2 star? I will come to you in the next couple of slides. So, this method is known as ideal IQ and GRE, ideal quant in Philips, liver lab at Histo in Siemens. Very robust sequence, 16 second breath hold, excellent sequence. If you don't have all these special sequences also, this sequence is more than enough to assess the hepatic iron quantification. In addition to that, you can also get fat, you can also get water only, fat only, in phase, opposed phase. So, this is one of the remarkable breakthroughs in MRI technology of labours. Again, basic physics is simple, it is shown very clearly here. Outside magnetic field B0, inside the magnetic field, when there is excessive iron deposition, all the protons go into this array, they go into this array, they are monolane, T2 waiting goes into a toss. That is why the T2 signal decay occurs very fast and because T2 signal decay occurs very fast, you get signal very fast and the reduction in the signal industry of the hepatic parenchyma signal occurs very fast and that is what is the basic physics of MRI hepatic iron signal decay, fast signal decay because of iron deposition. If there is less iron deposition, signal decay occurs slowly. If there is severe iron deposition, signal decay occurs fast because of excessive iron deposition causing susceptibility to the magnetic field causes signal decay. That is what is the basic physics of end deposition. You can see here that you give multiple TEs. Now, the role of MRI is giving multiple TEs at varying levels. Start at a TE of 1 millisecond, go up to 7.4 here. When you give multiple TEs in the liver, what happens is when there is excessive iron deposition, there will be very fast defacing because of iron saturation, there will be very fast defacing and very fast susceptibility effect of liver parenchyma and the liver signal drops very fast. You can see here that in a normal individual from 1 millisecond to 7.4, there is almost no signal drop, literally the same whereas when there is severe iron or status, starting at 1 signal drop and suddenly the signal drops. So, this signal drop is what is estimated by us, is what is used by the liver parameters to assess the quantification of iron in the liver parenchyma. So, this signal drop is quantified by T2 and T2 star. T2 is only fast pinnacle technique which is not breath hold, not any more used, not comfortable for anyone. T2 star is a GRE based sequence, fast single breath hold technique, 15 seconds, 16 seconds, you can get this technique. So, that is why T2 star based technique is what is commonly used to assess the liver iron load. This is a graph which I have shown earlier as an image, this is a graph as the iron load increases. So, the decay occurs very fast and T times becomes so low that means from 1 to 7.4, after 1, at immediately 1.42, the signal saturates, the liver parenchyma signal saturates because the decay occurs very fast, the iron load status is very severe. If it is my, then slowly at 15 milliseconds, 10 milliseconds, the decay occurs. Now, what is the important point here? When you start doing a T2 star technique, signal decay occurs. What is meant by R2 star? R2 star is the rate at which the signal decay occurs, it is the rate at which the signal decay occurs. You can quantify the rate at which the signal decay occurs. So, R2 star is measured in hertz and T2 star is milliseconds. That is what is important. Now, when you start doing a chemical shift imaging of liver, you have got two T's in phase, opposed phase. Opposed phase comes first, in phase comes opposed. In phase comes like opposed phase is 2.1, 1.5, 4.2 or 4.4 and for in phase. So, opposed phase comes first. So, when there is excessive iron deposition in liver, there is a paradoxical shift of signal drop. In the in phase, there is a severe signal drop when compared to opposed phase. That is because of excessive iron deposition leading to early decay of the signal. It is a moving fast decay. You can see here that the fast decay that occurs when multiple T's are given, multiple T's are given. You can look at fast decay of the liver signal that happens, parenchyma signal happens at multiple T's. So, the rate of decay that means rate at which the signal drops is known as R2 star and that is measured in hertz. T2 star values are measured as milliseconds and that is how you quantify the liver iron. Now, one method known as signal density ratio between liver, spleen and para spinal muscles. This was used, it is still used, it is a very good method, but it is good in mild iron overload, but in severe iron overload, it goes by the toss. So, how do you measure simple? When you run a T2 technique of the abdomen, if liver signal is far less or less than that of the para spinal muscle, para spinal muscle signals here, then it means to say that there is liver iron overload status. So, depending upon signal drop or we cannot say signal drop, but depending upon calculate the signal intensity of liver and para spinal muscle, based upon that, it is what is known as Ganton method where you quantify liver iron by measuring the liver signal at in these three on T2 weighted images in these at these three levels, three ROIs and then ROI at the bilateral para spinal muscles and then they meant your equation, you calculate, put these values there and then depending upon the ratio of a signal between the liver and para spinal muscles, you can quantify liver iron. That is one method. The other method is what I told you is T2, T2 star, R2, R2 star. T2 star is a preferred method. The rate of decay of the liver para spinal signal is known as R2 or R2 star. So, how do you calculate R2 star? Calculation of R2 star is very simple. If you have a T2 star, it is 1000 by T2 star. Then similarly, if you have an R2 star, 1000 by R2 star is T2 star because the T2 star and R2 star are inversely proportional. I will explain this point very clearly here. For example, if the R2 star is 500, that means very high R2 star, that means there is very high iron rod status, T2 star automatically comes down. That is 2, 1000 by 500 is 2. You can imagine that whenever there is excessive iron overload, the signal drops and rate of signal also drops equally. So, that is why the T2 star and R2 star are inversely related. So, whenever there is a high iron content, automatically T2 star value becomes low or on the contrary, whenever there is a high faster signal decay, that means R2 star is very high. Why R2 star is becoming very high? There is iron overload and signal decay is occurring very fast. So, when signal decay is very fast, that means rate of decay. If rate of decay, that means R2 star. If R2 star is very high, that means signal decay and even paramount is occurring very fast. That means, excessive iron overload and that is why T2 star values are very low. When T2 star values are very low, it means to say that there is even hepatic iron overload. So, always remember that R2 star and T2 star are inversely related. Number one, when you calculate R2 star, 1000 by R2 star, because inversely, 1000 by R2 star is the T2 star. For example, R2 star is 800. 1000 by 800, 1.1, 1.2 is T2 star. That means severe, very severe iron overload. So, R2 star very high values indicate that there is very high iron overload in the liver. Proportionately, the T2 star becomes very low because it only exudes iron overload status, the signal also becomes very low. This is what is known as T2 star and R2 star equation and both of them are very useful. I reiterate, R2 star if very high or T2 star if very low, that means there is iron overload status. When you calculate R2 star, the dedicated sequences. For example, in GE, there is sequence known as R2 star sequence which you will run as for liver and heart also for myocardium also and R2 star will give you in detail about the various, you can draw ROAs, get R2 star. And now the advanced methods have come where you do this multi-echo GRE sequence or Dixon-Quant or liver lab or history where if you draw an ROA, automatically you will get T2 star values. And more importantly now, a special software algorithms have come third party vendor where if you draw an ROA, you get a T2 star value, you get an R2 star value and besides that, you will also get liver iron quantification in milligrams per gram of liver. This is what I told you about post-processed image from a multi-echo GRE sequence, this sequence. Now on a multi-echo GRE sequence, I told you six and the six in the six outputs, you got an R2 star, you got a PDFF. PDFF is a so here you draw an ROA, ROA here in liver, it is 385, 1000 by 385, 2.5 milliseconds is T2 star. Now here you can draw ROAs, it is 735, R2 star, hepatic research 1.8, 1000 by R2 star is T2 star, 1.3. Similarly, there are softwares in GRE in being known as ready view or in Phillips you call it as a Dixon-Quant or liver lab, liver lab is there in a liver histone in Siemens, you can get in this advanced workstation software you can get, you can even draw on the myocardium, you can get the T2 star and R2 star of myocardium. Now how to calculate the hepatic cardiac iron concentration? Now the three steps are calculate R2 star, calculate T2 star, now calculate the accurate hepatic iron or myocardial iron concentration and that is expressed as milligram of iron per gram of dry weight of liver or heart, how to calculate? Only 1.5 T is at the calculation are very simple. There are special downloadable software known as Iron Alliance Health by Julian Vitale in on the web, you can download, you can just place the T2 star value of liver and heart automatically get the iron concentration. So how do you express, how do you interpret the liver and heart iron quantification? This is what it is here, what is normal, what is it normal? Once derived T2 star, T2 star, you download this app, it is for app for mobiles, app for android, app for computers, everything is available download this app. At 1.5 or 3, put T2 star value there, for heart put T2 star value here. Automatically you look at the liver iron concentration and myocardial iron concentration and depending upon the amount of iron there, you quantify it as mild monitor severe iron molecules. When you start reporting, you report as the study was fought on 1.5 or 3 T, based on measurements in multiple regions of printers, the R2 star and T2 star of liver and heart what assessed, which correspond to iron concentration LAC, MIC of milligram of iron per gram and ranges with you. Similarly, if there is any previous study, comment on the previous study, comparison of treatment and attach the reference ranges and standard guidelines for interpretation. We give reference values, myocardium T2 star more than 20, R2 star less than 50. Similarly, T2 star here, similarly at 3 Tesla here, what is normal, what is mild to moderate, what is severe. Similarly, for liver, you can give how much is the T2 star. If T2 star is 4.5 to 15.4, it is mild. If T2 star is 2.1 to 4.5 milliseconds, it is moderate. If T2 star is less than 2.1, it is severe herpatic iron overload. Similarly, the LIC and MIC can also be given. For example, the liver iron concentration algorithm downloaded, I can tell you what are the bitfalls iron calculation by MRA. If there is very excessive iron overload, that means more than 20 milligram per gram, then the liver decay, saturation, the liver signal decay occurs at for example, 0.8 milliseconds or 0.5 milliseconds. But you are interrogating at 1 millisecond. That means already liver has reached this peak desaturation, peak signal decay, then you are going to underestimate the liver iron concentration. So, you should remember that what you estimate in severe is okay. But very severe, you cannot because your MRA cannot do a T value of 0.8 or 0.5 milliseconds. That is why very severe iron load status cannot be accurately estimated. You can say severe and very severe, but cannot accurately quantify. That is the limitation of the MRA. This you should remember. How to avoid artifacts when you assess the MRA? You need to have a proper breath hold. If there is no breath hold, there is movement artifact, respiratory movement artifact. It goes for a toss. Even on a dedicated R2 star sequence, it goes for a toss. Then placement of ROAs, avoiding blood vessels, surfaces, hyalum, and especially in the heart, you place in the mid-intervention class. So, this is what is about liver iron concentration by MRA. Very simple, very easy. Try to follow this. Thank you very much for your patience and attention.