3D Ultrasound – Part 2

September 7, 2006

OBGYN.net Conference CoverageFrom FIGO 2000 INTERNATIONAL FEDERATION of GYNECOLOGY & OBSTETRICS: Washington DC, USA

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Dr. Timor-Trisch: “Ladies and gentlemen, we will switch gears now and we will show two opposite things of the same coin. Jorge is from Florida - warm and nice, and I am from New York - cold and rainy. He is talking about gynecology, and I’m talking about obstetrics. He is young, and I am more mature. He is using the computer extensively, and it’s very hard to fight his technology with my plain slides, but I’m getting there too. He scanned a live patient, and I will only show you a videotape, but this is also part of what three-dimensional ultrasound can do. I will be talking today about the three-dimensional assessment of the fetal brain but not before I show you what I am basing my three-dimensional ultrasound of the fetal brain and that is the two-dimensional ultrasound. 

A comprehensive neuroscan has to include, as far as I’m concerned, the scanning of the brain in all three planes. Transvaginal sonography, as I will show you, enables the sagittal plane and the coronal plane but it’s very rare or almost never that you can get the axial plane or the horizontal plane, but transabdominal sonography enables the axial plane. Remember, when you do a BPD for a head circumference measurement, that is your axial plane where the brain scans are usually done. I will also tell you today that scanning the brain only in the axial plane is not cutting the mustard - that’s in American. In a language that everybody would understand - that is not the proper fetal neuroscan to be done, therefore, you should use jointly the transabdominal and the transvaginal scans. This is what you would see with a transabdominal scan and, remember, you see the far hemisphere much better; the near hemisphere is like you are driving through the London fog, you absolutely don’t see anything. Now after 15 or 16 weeks this boney structure will prevent you from getting good pictures of the fetal brain, therefore, the fetal neuroscan uses the fontanels as acoustic windows that you can sneak in. Also remember that around 15 to 16 weeks the sagittal suture is also quite wide, therefore, you can get into the fetal brain along the sagittal suture as well as the anterior fontanel. If transvaginal sonography is possible or in other words, if the fetus is in vertex presentation - very clear images can be seen. Now you have a new problem, the sections are not parallel and, therefore, the strict nomenclature of the classical planes of coronal and sagittal cannot be used with transvaginal sonography. Now the technique is simple; you insert the vaginal probe and with your abdominal hand you manipulate the head in a position to see the fontanel at your footprint of the probe. Then you turn your probe around and around and you get the sagittal and the coronal planes, and you can enjoy the beautiful pictures you get. 

Let me now base my three-dimensional ultrasound onto what you have to see but you have to know the two-dimensional anatomy and, therefore, we propose a new nomenclature in which we have three groups in the coronal planes - the frontal, midcoronal, and an occipital group. When you turn your probe in the coronal plane very far anteriorly and you see the orbits, then you have this frontal-1 section where you see the falx and brain tissue. In the second one is the frontal-2 section, you still see the falx but you also see a little bit of the anterior horns and maybe the frontal part of the corpus callosum, and this looks like a steer’s head configuration - the F2 and the F1 sections. Now just to make a small, I would say – warning, when you scan the fetal brain you really have to go back and read your anatomy books once again in order to understand some of the structures that you will see. The third section is really part of the midcoronal group and it’s called midcoronal-1. That’s when you see the lateral ventricles, the cavum septi pellucidi, the knee of the corpus callosum and the two caudate nuclei or the head of the caudate nuclei. The next is the midcoronal-2 section, which is the most important section on which you see the two lateral ventricles and the choroid plexus in it. Then you see the choroid plexus dipping into the third ventricle and that’s the foramen of Monro, the third ventricle with its choroid plexus, the cavum septi pellucidi, and the corpus callosum. You also see the two thalami and, of course, the falx on the upper part. The third group is the midcoronal-3, which is quite important, and you see the lateral ventricles with the choroid plexus with its entire body of them. You see the tentorium, the posterior part of the corpus callosum, the splenium right there, the cerebellum a little bit but not real well on this and on a classical midcoronal-3, and of course you see the falx. The occipital group starts with occipital-1 where you see the lateral ventricles and the cerebellar hemispheres, the fourth ventricle sometimes, the tentorium of course right there, and sometimes you even see the cisterna magna. I call this the owl’s eye configuration because it looks like those night birds from the jungle; they look like O’s. In the occipital-2 section you will see the hemispheres and the cisterna magna and the tentorium. 

Now with the sagittal planes, you have three kinds. The median section - only one of them of course, and the right and left oblique-1 and the right and left oblique- 2. The median section is the most important plane in addition to the midcoronal-2, the median section will show you a magnificent picture that you can only see when you do an MRI of the brain, usually when the baby is born. Here of course you see the corpus callosum, the cavum septi pellucidi, the cavum vergae, the thalamus with the pericallosal there, the corpora quadrigemina, the cerebellum, the fourth ventricle, the cisterna magna, and once again, please forgive me for cursing you with all these names. Again, if you want to understand fetal brain anatomy, you really have to go back to the books. The corpus callosum I showed you is like a C-shaped structure, it has a body, a knee, and a tail and that is very important to image. Now the posterior part of the cavum septi pellucidi is called cavum vergae and this patient was sent to me because they showed on one scan outside the hospital a cystic structure and they were not sure what it was. The moment you use these frontal-1 and -2, midcoronal-1, -2, and –3, occipital-1 and -2 then you can systematically scan the brain and you will see on three-dimensional ultrasound how easy this is done. I’m fighting to get these on the 2D scans. I was able to show that the anterior part of the corpus callosum is here and the posterior part of the corpus callosum is the cavum vergae. 

You can also see that I don’t always use all seven planes because they are unimportant at times, in this case I used only five. The right and left oblique-1 are extremely important planes because you see the anterior horn and the posterior horn. You shouldn’t see it but it’s there, the temporal horn or the inferior horn below the thalamus. If you see the temporal horn on an oblique right and left, it is usually pathological, there is ventriculomegaly. The oblique-2, very lateral right and left sections, I don’t use too many times but you can see here the parietal and the occipital operculum which then close later in pregnancy to hide the insula and, of course, the middle cerebral artery is right there. Let me now summarize this, I don’t really want you to see from the back the structures on each of these frontal, midcoronal, and occipital sections but remember one thing, there are a lot of structures that you see in the brain. The cluster of the structures that you see at any given plane should be stable and should be a fixed number. When you see that number of structures you know that you’re are talking about a certain plane. Once again, the most structures that you see are usually the midcoronal-2 and, once again, in the sagittal plane the median section. If you want to go to this one, we have an article but it probably will be obsolete by using the three-dimensional ultrasound. 

I also would like to show you that you can image the blood supply of the brain in the coronal and sagittal planes and, indeed, you see magnificent pictures such as these. In order to image some of the more important vessels of the brain, as far as I’m concerned, you usually have to image one brain artery which is the pericallosal artery which is really showing you that the corpus callosum is present because there are three structures that go hand in hand - the pericallosal artery, the corpus callosum, and the cavum septi pellucidi. This is how you diagnose directly and not by indirect signs of agenesis of the corpus callosum which I will show you in one or two pictures. Now of course when you have your median plane, you can see quite a lot of beautiful arteries and this is at 17-weeks starting from the internal carotid and going up to the branches of the arterial cerebral artery. 

Now let me show you some pathology and then we’ll go right away to 3D. For instance, here are the porencephalic cysts. Now when you say porencephalic cysts, that’s a bleak and bad diagnosis anyway but in order to show the extent of the lesion and the localization of the lesion, I propose that by using this very compulsive way to look at the brain by sections, you can localize and tell the extent of the lesion. In this case, it was in the right side, and there was a new hemorrhage there; and on the left side there was an old lesion, which created the porencephalic lesion. Here is a holoprosencephaly in which, once again, I used only several of the planes but the diagnosis is clear and once again if you have all these, you can definitely make the diagnosis in a very, very short time. In this case, a lobar holoprosencephaly, which you have to differentiate from a septo-optic dysplasia, was also seen on that midcoronal-2 picture or even on the midcoronal-1 if you want but the midcoronal-2 is the best. The box-shaped lesion without the walls of the cavum septi pellucidi makes the diagnosis extremely easy when you do a compulsive section-by-section analysis of the brain. 

Now let me go to the 3-D ultrasound and all that you heard was really the basis of what I will be talking about. Once again, I told you that transvaginal sonography really does not image the brain in the classical parallel sagittal or coronal sections or horizontal sections. The transabdominal scan will give you only one plane, which is the axial plane. It’s very seldom you can do a coronal plane and almost never the sagittal plane, you have to fight for it, and once again, the pictures are not extremely clear. Now if you use the experience of the neonatologists which really published this a very long time ago in 1986, the Grand Atlas of Neo-anatomy showed you clearly that you can go into the neonatal brain through the fontanel and get magnificent pictures which are really doing the same thing as you would do an anatomy de-sectional plane. 

Now Jorge already told you, and I’m very happy about it because I don’t have to waste that much time, you do the acquisition by placing the region of interest and selecting the Y and the X plane boxes. You get the image on the screen as he described it to you, instead of the uterus you now have the brain, in the A box - the coronal plane, in the B box - the sagittal plane, and in the C box - the horizontal plane. It was not said but you also have noticed the active box is always the one that has a frame around it and, therefore, you can go and change the active box to all of these planes. Of course, I’m using here a line drawing to show you what I can do with the probe. I can move the probe from the anterior fontanel to the back through or along the sagittal suture in order to have a much better view of the posterior fossa. Now I will show all of this during the videotape, therefore, I’m going quite fast here because I would like you to enjoy more of the live presentation of the videotape. But watch out, you will see the same case in which this is an 18-week pregnancy with a normal brain, and once again, this is the active box. Watch the active box while I am changing the plane going from frontal to occipital and the picture will change here. The C box will not change because I keep the same horizontal level at all times. Now here I will move the coronal plane a little bit to the back so here is the steer head configuration with anterior horns peeking through. A little bit more posterior, and you have another view of the anterior horns. Move it a little more towards the occiput and here is what I call the midcoronal-2 plane, and here are the choroid plexus, the foramen of Monro, the thalami, and the third ventricle. Moving it to the back would be my midcoronal-3 plane with a beautiful view of the choroid plexus, and once again, move it all the way to the back and you see the occipital horns and the posterior fossa. Here is a picture that moved a little bit out of the frame but these are mainly the main pictures that I’m looking at that without which I cannot really make a good diagnosis of the fetal brain along the three most important midbrain images. 

Now we’ll go to the sagittal planes. Now the active box is on the right on the sagittal side, and I’m moving the line that goes from left to right, from right to left, and that box will change. Here you have the line over the left side of the brain showing the anterior posterior horns in the choroid plexus. Move it to the middle, and here move it to the right side with the right anterior horn and posterior horn and the right choroid plexus. Once again, we don’t change the C box. Here are the three sagittal planes that I consider extremely important in order to localize midbrain structures and lateral ventricular structures. Now we move the box to the lower C box and this is now the axial box, and I will move the entire line going through box A and B up and down in order to see the different planes up and down such as a very high horizontal and mid-horizontal near the low horizontal section. 

Some of the pathologies that you can see will be one of many; I couldn’t bring all the pathologies. You can see the agenesis of the corpus callosum, and I brought this because this is really what 3D imaging of the brain is all about. Those who do brain scans understand that the agenesis of the corpus callosum is made by indirect diagnosis. It is made by seeing the lateral ventricles being displaced and moved upwards, and the third ventricle connecting with the intra-hemispheric fissure. You see the radial positioning of the gyri but, basically, very few times you see the corpus callosum and that’s what you have to see. On the axial section you also see the corpus cephalea so here is agenesis of the corpus callosum in which the median section tells you the story. Only the knee of the corpus callosum is there, there is ventriculomegaly, corpus cephalea, the tear drop shape, the lateral ventricles, and of course once again, the third ventricle moving up and connecting with the intra-hemispheric fissure. 

Here is one interesting way that we look at the brain. Once again, if you do it with two-dimensional transvaginal sonography you already go in a slanted and oblique way to image the lateral ventricles. Now here you can do it elegantly by tilting the head, taking the symmetrical nice head and tilting it to the left and then scanning along that line. You see the three horns on the same picture because otherwise you wouldn’t see them quite nicely. Here are the anterior, posterior, and inferior horns, and all of them are dilated. We call this the three-horn view. You will see an article coming up in one of the journals and it’s in print now. Once again, it’s easy to move and tilt the head to the right side and then you see the right three-horn view. 

Before I show you the tape, here is something that you should also consider because it helps. The three-dimensional machine that we used, which is once again the Medison machine, has color or angio capability and that is crucial when you want to determine the diagnosis of partial agenesis of the corpus callosum. It’s not enough to see the coronal planes, it’s not enough to see the horizontal planes with the tear drop shape ventricles but you have to diagnose the extent of the existence or the lack of the corpus callosum. By turning on the color, you will see that there is a very short pericallosal artery. Now this is even more important when you look for arachnoid cysts, and I will come to that but not before making Jorge’s talk a little more adapted to what I need. My most important feature in the three-dimensional ultrasound machine of medicine is that dot which for some reason I call the marker dot. I’m not sure what others call it, but I call it the marker dot. As a matter of fact, that is the point where three planes meet each other and by putting that point to the right or to the left, you really can localize with absolute precision the place you are in the brain that you want to see, and in the tape you will see that. But let me show you a case about alobar holoprosencephaly in which not only looking at the brain brings me the diagnosis of holoprosencephaly in this trisomy 13 case at 17-weeks but you can immediately image the face in which the proboscis and that cyclops was detected. Once again, we really did not work too much on this, probably about ten minutes until we got a very beautiful picture. 

Now so far I’ve talked about transvaginal sonography and three-dimensional ultrasound but the picture on the right is a transabdominal picture. If you get good penetration and a good picture, and you can at times even transabdominally, you can get quite a good picture of the fetal brain. Once again, if you can do an external version, which I do very often to see the brain with the transvaginal probe, I do it. If I cannot, I put the vaginal probe into the umbilical depression and try to do it that way or do an abdominal scan. Here is a case of a quadrigeminal plate arachnoid cyst at 24-weeks. In order to counsel this patient the correct way, the pediatric neurologist and neurosurgeon said – well, if this fetus has a corpus callosum the outlook is quite good, and if it doesn’t it’s miserable. So we then turned on the color and demonstrated the pericallosal artery and have shown that it is moved very much to the right. Why is that - because if you have an arachnoid cyst that straddles the falx from the two sides, the pressure destroys the corpus callosum. If it’s on one side of the falx, the corpus callosum stays alive and that was the case in this case. We also tried it in a way to see whether the cyst is here, and this work was really done by Dr. Babinski who’s in the audience. She’s from Hungary and she did this nice picture for me showing that there is a cyst right there, and then we have the pericallosal artery that has moved to the right. 

I will stop but not before showing you that you can also do a beautiful scan of the vertebral column and that really completes it, it’s still the central nervous system. Remember, in cases of the abnormal karyotype 2 and other vertebral problems, you can really image the vertebral column quite nicely as in this case using the transparency mode in which you suppress the soft tissues and keep the high echogenic vertebral column and the ribs. This was a case of hemivertebra but I will show you one, which is much nicer. I got this from Dr. Hobbins and this is a three-dimensional picture of hemivertebra right there. 

In summary, a three-dimensional fetal neuroscan is a promising imaging technology, and I honestly can tell you that now that we have it, I could not do without it. That’s the reason that on the east coast right now we get almost all the referrals that have any doubts of a problem of the central nervous system because we can do a very precise workup. Normal anatomy and pathology can be better and more confidently defined. Patient counseling can be more focused and what is even more important, pediatric neurology and neurosurgical consultants understand the pathology better and they don’t tell the patients - wait till the baby is born, we’ll do an MRI, we’ll tell you what’s going on. Now they rely on our pictures in order to give the patients more precise counseling. I think we should eagerly await improving 3D equipment and everyday it is happening and it’s a great teaching gain. 

Now let me show you the video, it will be another five minutes or so but I hope that you’ll enjoy the live scan of the brain in this case. We start out by having the three coronal, sagittal, and axial picture on the screen, and you can see that I’m walking the sagittal line to the back. You see that I’m going and changing the picture in the active box. I will soon change the imaging level a little bit because I would like to show you some other levels but I’m almost to the back here showing the cerebellum and disappearing in the posterior part. You can see that the C box doesn’t change. Now I’m going quite fast back to the front in a second, also watch the marker dot because the marker dot will be on the same spot every time in all three planes. Once again, I’m going now with the marker dot to see to the right and you will see in a second that I replaced the marker dot in a structure. Now it’s in the thalamus here and here, and on the lower picture. Now I am on the cavum septi pellucidi right there in all three. Now I’m going to the right, once again, anterior horn, posterior horn, and inferior horn right there. Now you can see that the changes will be in the C box when I go up and down. I’m starting at the base of the skull, cisterna magna, and the cerebellum. Here you see the fourth ventricle and third ventricle going up. You see the two anterior horns, two posterior horns, and disappearing here is the sagittal sinus and disappearing on top of the head. Here is the fontanel by the way that I originally got the picture. Now on the next images you will see the importance of the marker dot. See the marker dot is in the left anterior horn and now in the right anterior horn in all three places. Now I’m going to the middle and I’m going back to the anterior horn. Now I’m going to see what that little structure there is and in all three I am in a little tiny choroid plexus cyst so you can really localize the lesion quite perfectly. Now I am in the cavum septi pellucidi. Now I’m trying to see what’s going on in the anterior horn, all three places, and left and right anterior horns. This is the active box. I want to see the corpus callosum probably right now. This is the arachnoid cyst that I was talking about. Take a look now, once again, I am scanning the sagittal plane and see the coronal plane is moving, and I want to see the septum. You can see I’m walking the marker dot along the septum in all three planes. I also wanted to see whether there is any vessel there because interestingly enough you will probably read one day when it appears that we punctured this cyst in utero in order to aspirate the contents. We wanted to avoid all the vessels so we are very keen about looking for the vessels. We wanted to see how far anteriorly and posteriorly it goes, and what the extent is on the horizontal picture. Can you see that it’s a middle lesion pushing the sagittal sinus and the midline structures to the right? Here is when you turn on the color and we wanted to see whether the pericallosal artery is indeed present or not. We were very happy to see that the pericallosal artery was present but not in the midline, it was present and pushed to the right side. Basically, this was my part of trying to bring you a little bit of what three-dimensional ultrasound can do in imaging the fetal brain. I hope that this will be the standard of examinations in the years to come. Thank you very much.”