 now we have is MRI of Lassentap and this will be by Dr. Manjiri Dige. Dr. Dige is Professor of Ideology at Medical and also Medical Director of Ultrasound and Director of Ops Imaging for Ideology and Edchen Professor of Ops and Gynaecology in University of Washington. She is Fellow in Society of Adornment Ideology and Society of Ideology in Ultrasound and she has received several awards and fellowship including the Melvin Fickley Fellowship in Radiology Journalism and awarded by that has been awarded by the American Ron Jen Ray Society. She was past section chief of body imaging in University of Washington. We are thankful to you ma'am for your contributions to this course and our learning and let's begin with this talk. Good morning. My name is Manjiri Dige. I'm a professor at the University of Washington in Seattle. My topic of presentation today is MRI of Lassentap Invasion Spectrum. The goals for today's presentation include brief review of the epidemiology discussed the common findings on MRI. We'll look at some pitfalls and then also look at some management implications and some potential areas of improvement in clinical practice. We know the incidence of past has been increasing over time which is mainly because of the increasing rate of caesarean sections. Ultrasound and MRI are performed for diagnosis and are considered important methods to reduce the risk of maternal morbidity and mortality. Now in normal placentation extravillus trophoblast invade the decedure and convert the spiral arterioles of the endometrium to uteroplacental vessels which is basically desidualization. The trophoblastic proliferation leads to formation of the corionic v-lie. If the underlying endometrium is deficient desidualization fails and the trophoblast or corionic v-lie invade and penetrate the myometrium. This abnormal vascularization can be due to scarring after surgery which leads to hypoxia and this leads to the defective desidualization and excessive trophoblastic invasion. Nomenclature used for PAS includes pathologic nomenclature which is a crata seen in about 75% of cases and then in crata seen in about 18% where the v-lie actually invade into the myometrium. In a crata they only adhere to the myometrium. Per crata seen in a smaller number about 7% of cases where the v-lie extend through the myometrium into or beyond the serosa. So these are the different forms of placenta or crata spectrum or morbidly here in placenta. This is normal. This is in a crata. This is invaded into the myometrium and so in crata and then through and through and through the serosa, so per crata. The amount of placenta involved can also be variable. It can be total where all of the placenta is involved. It can be partial and also it can be focal. The incidence of placenta a crata has increased about 10-fold in the past 40 years. In 2016 a study was conducted using the national inpatient sample and they found that the overall rate of placenta crata in United States was one in 272 women for who had birth-related hospital discharge diagnosis which is higher than any other published study. The rising incidence of placenta crata spectrum correlates with the global increase in C-section rates. So in 1965 the rate of C-section C-sections was about 4.5% but that has increased to 31% in 2017. So although pass is considered a rare condition, its incidence has increased 10-fold in the past 50 years and the issue is this. This is a surgery being done in a patient with a crata spectrum and you look at the amount of hemorrhage that this patient has as you're trying to get in through the placenta get to the baby there's a you know this is getting through the uterus they will be opening up the amniotic cavity soon and so then be delivering the baby but it's just a bloody mess. This is a reason why there's maternal morbidity and mortality. Now they're through the amniotic fluid and they're trying to get the baby out and you can see the baby's hand over here so the hand is out and then the baby's head is out. So looking at the amount of bleeding this is just getting the baby out then the uterus needs to be resected if necessary along with you know obviously the placenta as well. So this is a bad disease or a bad condition not necessarily a disease but a bad condition that needs high expertise and can can actually lead to maternal death as well. So what are the risk factors for placenta crata spectrum? So if a placenta previa along with C section is considered as having the highest odds of placenta crata or placenta crata so if you have a C section along with a placenta previa your risk of placenta crata spectrum increases to 67%. If you've had myomectomy or DNC there's an increased risk as well but smaller advance maternal age has been considered to have an higher risk about 3% but we don't know if it's age or if it's parity. Some of the clinical markers that can be used include the placental biomarkers like higher AFP, plasma protein A, human placental lactogen and the total placental cell free mRNA as well which can be evaluated to assess for placenta crata spectrum. So why sprenatal diagnosis is crucial because it allows for us to plan for optimal management to decide the timing and the site of surgery. It is important because you need blood products and skilled anesthesia, surgical and interventional radiology team to be ready. C section is usually planned at 36 weeks of gestation to minimize the risk of spontaneous labor and surgical planning has to be individualized according to the imaging findings and the patient risk factors. The importance of antenatal detection of invasive placentation also relies on the fact that maternal morbidity has been shown to decrease when these disorders are diagnosed prenatally because it allows for all this pre-planned treatment as well. Other thing to consider is that fertility counseling needs to be considered with the patient because with this condition the uterus might not be saved and the patient might not have be able to have any more kids in the future. So the under the MRI indications mostly most commonly limited or inconclusive ultrasound leads to you know an MRI being done and mostly it's paid for patients who have high BMI other causes sometimes of placenta is posterior and lateral and it's difficult to see it on ultrasound and it is also helpful to increase the level of confidence especially in high risk patients and then to assess the depth of invasion in these cases. We don't know for sure if MRI does allow for better delineation if it allows for a better you know modification of depth of invasion or change in management and these are questions that need to be answered in the future. We usually perform MRI at between 23 and 30 weeks of gestation. Patient is supine or in the left lateral decupitis if she's in third trimester because they may not tolerate the supine position. Bladder is usually moderately full and we use a multi-channel phased array surface coil or a body coil. We usually have a radiologist available at the scanner to look at the images and decide if any modification or additional images are necessary. We use a 1.5 tesla scanner but 3 tesla can be used. They can be technical challenges because of the dielectric effect but if someone if you have good expertise you can use a 3 tesla magnet as well. So as we mentioned between 23 and 30 weeks of gestational age there's no incidence or no evidence for increased risk of MRI at any point in gestation so that's important to remember that's actually an ACR policy that has been published. We don't use any contrast that there's been no need for contrast shown in the published studies. We get an informed consent from the mother because there's you know there's lack of evidence based on the deleterious effect of MRI if any on the fetus. It's just not enough there's no evidence so we usually get informed consent from the mother. So about 23-24 weeks to 30 weeks our protocol includes a single shot fast pin echo sequences in three planes. We adjust the field of view according to what is necessary to cover the placenta. We sometimes we do get a T2 weighted balanced FFE image as well and we might get two planes either coronal axial and either coronal or sagittal. We get a T1 weighted sequence it can be either in an axial or sagittal plane. We get a even a diffusion weighted image. We usually get that in axial sometimes in sagittal as well and then as I said we don't give any IV contrast. So these are just two images showing the utility of balanced FFE images. We think balanced FFE images help a lot because one it gives you this India ink artifact between the bladder wall and the placenta and we find that to be really helpful when we're looking for invasion into the bladder wall. So in this particular case these are similar images or at the same level and you can see that there's some focal disruption seen over here but I'm not really confident about the rest of the wall anteriorly but on the balanced FFE image I can see that the India ink artifact is preserved everywhere except for this focal area where I suspect there might be a small focal invasion of focal per crater. The other reason we do balanced FFE is because it helps in differentiating between vessels and uterine wall because vessels are usually bright on balanced FFE images. What does a normal placenta look like? It is homogenous this is a placenta at 22 weeks and you can see that it has uniform appearance. These actually are dark areas along the periphery are small vessels they're not T2 dark bands and then at 33 weeks you can see that the homogeneity decreases and you get more of a heterogeneous appearance of the placenta but if you see a relatively homogenous placenta that can exclude abnormal placentation with a high level of confidence as well. So we'll look at the features later but this is what a normal placenta would look like. Normally uterine wall so it can be dark on T2 weighted images so you can see the wall over here on both sides. If you have a lot of vessels in the uterine wall it can appear a little bright as well so it can be a mildly hyper intense on T2 weighted images so you need to know you know look at multiple sequences look at multiple you know and balanced FFE of course they look the uterine wall looks dark except for the vessels which look bright. So you know in the literature there is inconsistency and variability on the imaging nomenclature that has been used for past interpretation and clinically as well my colleagues may use different terminology compared to me. This creates confusion among radiologists and clinician and adds heterogeneity in data collection which makes you know it has an impact on the patient's care. So this particular group it's the European working group on abnormally invasive placenta launched the proposal for ultrasound and MRI descriptors. The ultrasound descriptors were published in 2016 and the MRI descriptors were published in 2019 and they aim to reduce the ambiguous terms and define standardized terminology. So they believe that this will benefit future research clinical care and teaching aspects. This can be found in this particular article by Morrell in 2019 and this is the one that describes the MRI features. So I'm going to use the standardized MRI descriptors and we'll talk about the findings on pass. So these are the descriptors that I use and we'll go through each and every one. So the first one is heterogenous placenta. So normal placental signal appears as homogenous T2 hyperintense and relatively T1 hypointense. There is of course interobserver there's moderate interobserver agreement because this is a subjective feature. You can have heterogeneity from advanced gestational age, hemorrhage and then T2 dark bands and then as I said absent heterogeneity implies either absence of pass or a less severe form of pass. So just to show you the difference this is a homogenous placenta. This is a normal placenta with a homogenous signal. Compare that to this particular placenta which has a very heterogenous signal within it. This was a case of placenta in CRETA. So the key in this particular descriptor is looking at the signal of the placenta. Placental bulge. This is deviation of the seros are from the expected plane and it's caused by an abnormal bulge of the placental tissue into the neighboring organs. So the uterine serosa appears intact but the shape is distorted. So when you look at the uterus it has a pear shaped appearance. But in this lower uterine segment you can see that there's this abnormal bulge. So this abnormal bulge suggests pass with a high sensitivity and specificity almost up to 89 to 90 percent or so. So this is what a placental bulge looks like. Looks like if you draw a line along the normal uterine wall you can see that this part of the placenta is bulging outside. Placental in Chen in their published paper in 2018 described this finding and had actually and classified them into different types. Type 1 and type 2. In type 1 the bulge is it distorts it slightly outwards into the adjacent myometrium but the outline is intact. So you can hear you can see here that the outline is intact but the placenta does bulge a little bit outside. In type 2 there is focal bulge which distorts the outline of the uterus and there's a blurring of the adjacent outline. So in type 2a you'll have these bridging vessels. Type 2b will not have bridging vessels. We don't necessarily use these times but it's important to remember placental bulge as a feature in pass and the key here is to look at the uterine outline or uterine serosa and see if it's intact or not. Dark intraplacental bands are one or more areas of hypointensity with a linear appearance in contact with the maternal surface of the placenta. They correspond to fibrin deposits and it's considered as one of the best features to detect pass and has very good interobserver agreement. So normally you can see them in normal pregnancy after 30 weeks of gestation especially in patients who have preeclampsia and IUGR but they are probably related to placental infarcts as such. So this is what dark intraplacental bands look like. So you can see these dark bands in the placenta. They do extend to the maternal surface of the placenta and the key here is to look for these dark areas within the placenta. Now we said they are fibrin deposition and they may still be a false positive and the false positive as I said is probably because of placental infarction. They're seen about in about 5% of normal mature placenters. They have no significance unless of course the patient has IUGR or preeclampsia. You can also see dark intraplacental bands in patients who have intervulus thrombus or they have or patients who have bleeding and intervulus hemorrhage when they have seen in the subcarionic region but there are ways to deal with that as well. So just an example. This is a patient twin pregnancy twin A had this dark appearing area within the placenta. This was diagnosed you know this was read by two attendings at two different times and reported as you know placental creta but there was no placental creta on pathology. So these are just two images in this particular patient. Our patient did have CBI intrapartum bleeding and lower uterine segment atoni but when the pathology came back for the placenta it said that there was extensive fibrin deposition because of chronic placental insufficiency. So this was probably an area of infarction in this placenta and not necessarily a dark intraplacental band leading to placenta creta. So this was a false positive case. Kudbert in their paper in 2016 had this example of you know pitfall. So this patient had in dark areas seen on T2-8 sagittal image and you can see that you know the asterisk marks that these images from their paper and this was dark on multiple sequences. This was sagittal, this was coronal and you can see a dark band in that region and so you would think that this is probably a dark intraplacental band. But if you look carefully at the balanced gradient echo image you can see that there's bright signal in this region and this was actually not a dark intraplacental band but it was a recent hemorrhage. So the T1 sequence actually helped in evaluating this area and avoiding a misqual of placenta creta. This is an example from our institution. This patient had so these are axial T2-8 sequences, coronal T2-8 sequences and then balanced FFE. So this just illustrates why balanced FFE is helpful. There's a dark intraplacental band in this region and on that axial image coronal image it corresponds to this particular area but this area was bright on balanced FFE image. When you look at this different area in this patient of a dark intraplacental band axial coronal and then this is the balanced FFE image. You can see that on the balanced FFE images these dark intraplacental areas actually look different and that is the reason for this is because this was a dark intraplacental band but this particular thing here was a blood vessel. So blood vessels are bright on balanced FFE image and they balanced FFE can help differentiate between these two things whether it's a dark intraplacental band which is a fibrin deposition versus a blood vessel. So we find balanced FFE images to be quite helpful for us in some of these problem-solving areas. Placental ischemic infarction is another feature. You can see it on T2-8 and T1-8 sequences. They appear as increased signal intensity on T2 and decreased signal intensity on T1. They can result in placental heterogeneity and they can be seen in patients with preeclampsia or IUGR. So this is an example which shows an intraplacental infarct. So the key is to look for intraplacental pathology and this is T2 weighted sequence. This is a T1 weighted sequence. On T2 it's bright, T1 it's low signal intensity and diffusion is helpful here because on diffusion you can see that there is restriction but this was seen as a bright area on T1 weighted images and low signal intensity on T2 weighted images. So that's how we could make the difference. Loss of retroplacental dark zone which is this is a thin dark line. It is non-specific, can be seen, can be absent in normal pregnancy as well. So this particular area you can see this dark intraplacental band as an interface between the placenta and the myometrium and in the lower uterine segment in the same patient in this particular area you can see that there is we don't see this dark intraplacental band. Similarly on an axial image you can see that posteriorly this dark intraplacental band is lost in patches. So this is considered as one another feature of placenta accretar spectrum. Myometrial thinning is over thinning of the myometrium to less than one millimeter. So basically being invisible. It is seen on T2 weighted sequences. Normally the myometrium does become thin as the pregnancy progresses but especially at areas of caesarean section scars it is known to it can thin out quite significantly. So non-specific appearance but this is another feature that we look for in placenta accretar spectrum. So this is just to show you normal myometrium overlying the placenta you can see very thin myometrium. This is just a zoomed up image and you can see normal myometrium cure and then does become quite thinned out overlying the placenta. So you would suspect placenta accretar spectrum because as you see the placenta normal myometrium is thinned out and there's probably invasion into the placenta. Bladder wall interruption which is irregularity or disruption on the normal hypo intense bladder wall. It has high specificity and positive predictive value but low sensitivity for prenatal accretar detection. These are examples of bladder wall invasion. So T2 weighted sequence and you can see focal area of disruption of this hypo intense line of the urine bladder wall and this is a zoomed up image showing the same thing. So the key here is to look for this hypo intense line along the bladder wall. Focal exophytic mass is a break or extension beyond the uterine serosa. So you'll see placental tissue protruding through the uterine wall and extending beyond it. So most often because the placenta previous are associated with you'll see it along the you know as a mass filling the bladder. It predicts placenta accretar but does have low sensitivity and so this is an area of focal placental focal exophytic mass. As you can see there's extension of this placenta beyond the uterine wall and beyond the serosa as well. A normal vascularization of the placental bed which is where you see large vessels within the placental bed with disruption of the uteroplacental interface. This is seen on a T2 weighted sequence. So this is an example. So there's increased number of vessels seen over here on a sagittal and an axial image. This corresponds with the ultrasound finding of increased vascularity as well. And so this is an area of suplicental hypervascularity. So these are the features that we see on MR. These are the previously used terms and the recommended terms. Marked placental heterogeneity is called as heterogeneous placenta. Uterine bulging we don't really have a definite word for it but now we use placental bulge as a description. These three words these three descriptions are used for loss of retroplacental dark zone. Abnormal intraplacental vascularity I think we can call that as abnormal vascularization of the placental bed. We don't use a term tending of the bladder wall anymore, bladder wall interruption and focal exophytic mass. So these terms these old terms should be discarded for future use and the new term should be used for description. I'd like to talk about new techniques and diffusion weighted MR is something that we've been using for our cases as well. So this particular paper from 2009 has shown that at this at a b value of 1000 seconds per millimeters you can clearly define the border between the placenta and the myometrium. So this is an example. These are t2 weighted images. There's some you know sinning along the posterior wall of the posterior myometrial wall posterior lateral and along the right lateral aspect but the diffusion ADC map shows you the placenta and the utrient wall quite quite well. So here you can see the utrient wall appearing bright placenta is lower signal intensity and then as you go further down this is taken at a higher level this is in the lower utrient segment. You can see that you don't see the high signal intensity of the utrient wall anymore so there's definitely thinning of the myometrium in this particular region. So it increases we did a study in on diffusion weighted images and we found that it actually increases your confidence. It doesn't increase the sensitivity or specificity of compared to the t2 weighted sequences but it did increase our confidence level in assessing for placenta create our spectrum. Quickly like to show you some cases. This is case one. These are sagittal images t2 weighted images from left to right and you can see the bulge placental focal bulge in that region. So the description in this case would be so here's your myometrial thinning in this particular area, loss of retropalacental dark zone, hydrogenous placenta, bladder wall interruption and then focal exophytic mass. This shows you the placental bulge and then the dark intrapalacental bands. This was a patient who had placenta in crater. Another case just looking at the images so the red arrow shows dark intrapalacental bands. Green arrow show you the myometrial thinning. You can see the myometrium really well up to here and then it's completely thinned out. Similarly on the other side as well there's myometrial thinning over here. This shows you the focal placental bulge. The serozyme is intact but there's a bulge in that particular region. Similarly on the right side as well there's a focal placental bulge. This patient had a hysterectomy and you can see that this was a placenta in crater with likely focal precreta. This is a resected specimen where you can see the placenta bulging out. On opening up this uterus you can see the placenta with a lot of hemorrhage and sections show you the thinning of the myometrium. You can see the thinning out here and the focal extension into the placenta. This is case three where the red shows you the intrapalacental dark bands. The blue shows you the overall heterogeneity in this placenta. The light blue areas show you the placental bulge as you can see over here and then the green area shows you the placenta myometrial thinning as well. This is a resected specimen in this patient. You can see the big bulge along the so this is where the cervix would be. This is the fallopian tube over here and so this is the bulge from the placenta extending outwards and you can see there on a cross-section really well how the myometrium looks normal thickness over here but then in the lateral aspect you can see the extension of the placenta into the myometrium and focal bulging in this region. This was a placenta in crater because there was no breach of cirrhosa just about two millimeters from the cirrhosa. So in summary placental adhesion spectrum or abnormalities it's a challenging diagnosis needs clinical experience expertise and of course collaboration with other physicians from the obstetrics department as well. Some of the cardinal MRI features include dark intrapalacental T2 bands, placental heterogeneity, disorganized vascularity and utrient bulging. MR is not a reliable predictor of depth of invasion. It's the volume of dark intrapalacental bands. A degree of abnormal vascularization may correlate with the depth of placental invasion. This is something that needs to be further evaluated with studies. Atresan is the first imaging modality. MR does add value because it establishes or increases the diagnostic confidence. You can look for parametrial extension so it helps with anatomical information, location of the surgical incision if you have any large vessels that are intervening as well. The accuracy depends on experience and expertise available and some of these additional sequences like the balanced FFE and diffusion weighted images will be helpful. Future prospective studies are needed to see if MR can be useful at junk to ultrasound and the management plan should be based on the worst read in these cases because that is what will decide how the patient needs to be managed. These are some of the references. Thank you for your time.