3D in Gynecology - SD

Introduction to 3D Ultrasound

This lecture is about 3D ultrasound and how you can use it to evaluate the female pelvis and how it can really add to the diagnostic capability of ultrasound, in evaluating gynecologic patients.

What is 3D ultrasound? It's really a volume acquisition of an entire area of volume that you can then slice and dice in various orientations to tease out information that is held within that volume. You can display the volume in three orthogonal planes, as I'll show you in a moment. And there is one dot that represents a single point in space that is the intersection between all three planes. That dot can be moved around, or you can move the plane around so that all three planes become interactive.

This technology enables us to see anatomic sections in an orientation different from the acquisition section. Here's an example where at the top here we have the acquisition plane, which is in cross-section, transverse view of the uterus. And you can see that plane B, as we call it, is a longitudinal view of the uterus. And of course then plane C is a completely reconstructed plane, a plane that you cannot image in directly. And you can also identify this little dot in all three planes. That is the intersection of the three planes and you can see that it's on the endometrium.

So 3D is volume scanning, much like CT and MR. It's a volume acquisition that permits an infinite number of types of displays and certainly an infinite number of scan planes that you can display. And many of you can display these other planes in your mind's eye because as a trained sonographer, as you scan in 2D, you reconstruct in 3D what you think is going on. But it is amazing how sometimes the actual display can differ from what you think in your mind's eye should be.

Also 3D volume imaging makes us much less dependent on the person who's actually scanning because you're not just dependent on the one picture that that person took because you can re-scan the volume and generate any pictures after the patient is gone.

Advantages of 3D Ultrasound in Gynecology

Now the most important aspect I think of 3D ultrasound is the ability, at least in gynecology to display the coronal plane of the pelvis. For example, the coronal plane of the uterus. And here in the coronal of the uterus you can see the triangular shaped endometrium. You can even see the portion of the tube, the interstitial portion of the tube quite well. And you can see the shape of the endometrial cavity as well as the shape of the outside of the uterus, very much like you would with an MR, but actually in my opinion, better than you do with MR.

So the advantages of 3D is that the, the acquisition of data requires only one sweep. You take one sweep in 2D to generate your volume and basically if you're scanning transvaginally you can take one sweep of the uterus and one sweep of each ovary and be done and be able to reconstruct the entire scan offline using the volumes that you've obtained.

This is very different from a cine clip or a videotape where you are still dependent on the person who actually was holding the probe. In this case you can re-scan the pelvis in a different orientation from the orientation that was used to originally scan it.

So the most important benefit of 3D in gynecology is the ability to generate the reconstructed planes. Much like I'm showing you here where you can see the, IUD which is present within uterine cavity short of an MRI, this plane is not usually able to be displayed directly.

Evaluating IUD Placement

So here is the patient with the IUD. We are scanning it, we're scanning the uterus and longitudinally. We can also scan it transversely, but what we can't do directly is generate the coronal plane where you can actually see the IUD inside. This helps us a lot to look at for example, the placement of an IUD. In this view we have a normal placement of an IUD, which is squarely in the uterine cavity.

This patient on the other hand came in with some pain, some left-sided pain, and what we see here is that the limb of the IUD here seems to be embedded outside the cavity in the myometrium and that may be the source of this patient's pain.

Here's another IUD which is actually bent within the fundus of the uterus in a peculiar orientation. We really don't know using 2D ultrasound what the real position of the IUD is.

Here's a patient that has a low lying IUD. You can see the IUD is down in the lower uterine segment or cervix and wouldn't it be easy to just pull the string and get that IUD out? Well let's look in the coronal view and see where it really is. Well, here's the coronal view. Here's the top of the uterine cavity right here. The IUD is indeed down in the cervix, but look at this limb of the IUD, which is embedded in the cervix and would be very painful to remove.

Here's another case where in 2D ultrasound, the IUD is a little bit low. It's not at the fundus where it should be, but in the coronal view you can see that it actually has embedded itself on both sides where both arms of the IUD are embedded in the myometrium. This is an important, piece of information to have if you're trying to remove that IUD.

Now with 3D ultrasound one can also send these packets of information, this volume via telemedicine to somebody else who may want to reevaluate the entire pelvis and re-scan it in a different way. Or you may be receiving the raw data from another place and may wish to re-scan the pelvis slightly differently. This is very different from a video clip, which where you are really dependent on the method by which the acquisition was done.

Uterine Anomalies

Now the coronal view of the uterus is also very important to look at the shape of the uterine cavity. And here we have a uterine cavity which is abnormal. You have a septum right in the center here dividing the uterus into two horns right here. But this is not a bicornuate uterus. This is a septate uterus because the top of the uterus, the top of the fundus or the myometrium is actually straight. There is no indentation up here to match the indentation of the lining and therefore this is a septate rather than a bicornuate uterus.

Here's an example of a normal uterine cavity where you can see that normal triangular shape of the uterine cavity and compare it to a septate uterus. Of course, the outside of the uterus would look the same, but the inside of the uterus has a division in the middle that divides the cavity into two parts. This is called a subseptate 'cause the septum doesn't go all the way down. These women have a very high incidence of miscarriage, infertility or preterm delivery, and all sorts of complications during pregnancy. So it would be likely that this patient would be a candidate for the removal of that septum.

Now many of you may be thinking that in fact you can make the diagnosis of a septate or bicornuate uterus in 2D by observing the endometrium separated by this tongue of myometrium in between, which indicates that there is no, continuity between these two horns. And here are two different uteri that in fact show or display this finding. But are they the same? Can you conjure up in your mind what this uterus really looks like or what these uteri really look like? Are they the same or are they different? Well, let's take a look at the coronal view and in fact they are very different. This one is a arcuate uterus, which is a slight dip, considered a normal variant and considered that these folks are not necessarily at risk for pregnancy complications. They do not tend to get operated on for this. On the other hand, this one has a deeply septate uterus and you can actually see both horns quite nicely all the way to the interstitial portion of the tube. But you can see that this is a very deep septum. This is not a bicornuate uterus because there is no indentation at the top. There is just an indentation in the cavity.

Well, let's look at two other uteri. These are again, uteri that are where the cavity is divided into two by a tongue of myometrium. Are they the same? The answer is absolutely not. Here is a, arcuate uterus, again, very mild. Finding considered a normal variant here on the other hand is not only a septate uterus, but we also now have an indentation at the top of the, uterus of the outside of the uterus itself. So this is a bicornuate uterus. These are not as likely to be associated with miscarriage and adverse pregnancy outcome.

Here are a couple of other cases. This is an interesting case because you can see the IUD is in fact in the uterus, but it's low in the uterus because it was not able to be pushed up due to this septum. So this patient can easily get pregnant. In up here in the parts of the uterus, which are at the fundus, which you can see clearly in 2D do not contain an IUD. And here is a similar uterus showing that broad subseptum that divides, the uterus in two. And here's another example of the patient with the septate uterus showing you how nicely you can see the portion of the tube that travels through the myometrium.

Here is an example of a bicornuate uterus where you can see the indentation at the top of the uterus as well as the indentation, in the cavity. Compare that to this image where you only see one horn. There is no second horn. This is a unicornuate uterus, a very difficult diagnosis to make with a regular 2D ultrasound. And then here is the subseptate uterus showing a rather shallow broad septum that only goes down a little ways.

Now let's compare all of these. Let's compare the bicornuate uterus. This is fairly standard bicornuate uterus with an indentation at the top here and in the cavity. This one is a combination of a septate and a bicornuate, and this one is a septate straight septate uterus. This person would have a harder time with pregnancy than the other two. Look at how easily you can actually make these various diagnoses that in 2D are extremely difficult to do.

Now here's a patient that looked pretty normal on a 2D scan. Here is a transverse view of the uterus. Here's a longitudinal view of the uterus. This is quite normal. The uterus is deviated a little bit to one side, but when we take a look at the coronal plane, we clearly have a unicornuate uterus. We really have only a half a uterus in this case and this is an important diagnosis to make and yet very difficult to do unless you have that coronal view.

And sometimes when you have a unicornuate uterus as we have here and here is that one horn. Now this time it's on the other side. Sometimes you have a more complex uterine shape abnormality. And in this case you have one horn right here and then you have a rudimentary horn over here. Rudimentary horn has a little cavity in here. This is the same case showing you that little cavity over here with that rudimentary horn, which is not connected to the rest of the uterus. So this is a complex Müllerian malformation of the uterus, which places the patient at risk for having complications of pregnancy and certainly an ectopic pregnancy might reside in here and be at risk for rupture.

Now here's a patient that looked like she had a perfectly normal uterus, but when we looked at the reconstructed coronal view, it was clearly a T-shaped uterus, which is unfortunately a, a problem with infertility. And these patients are unable to get pregnant or to carry pregnancies very far in the most cases. And here is just one more case showing you a septate uterus right here. But what we have here is a twin pregnancy in one of the horns. This patient is at risk because she has a septum which puts her at risk of miscarriage. And then on top of that, she's also going to try to carry twins. So this is a very difficult pregnancy that probably requires a high risk obstetrician to take care of.

Polyps and Fibroids

Now let's go on to other displays of the uterus other than the shape. Other important information that you can get from 3D of the uterus is a look at the polyps and fibroids that can occur within the uterine cavity. And this is an example of a uterine cavity right here and inside that uterine cavity is chockfull of these polyps that you can actually see very nicely outlined by a little bit of fluid that is there. It is very important to be able to see those polyps or see fibroids that might be submucosal and might be candidates for being resected.

Here is an example of such a fibroid. This is a 2D view of a submucosal fibroid, right, right here. And the question is, do we need to put in some fluid here to outline that fibroid and figure out how much of it is really in the cavity? What 3D ultrasound does is it allows us to answer that question without putting in the fluid. If you bring the patient back at a time when the endometrium is thick, then it can be used as a contrast media to outline that fibroid and it can work just as well as having some fluid.

Here's another example of a submucosal fibroid right here. You can see it in a couple of different planes. These are regular 2D scans, but when I take the volume, I can then be in complete control of all the information in the volume and I can get this, image to be such that the fibroid is tangential to the wall of the uterus. And then I can use the endometrium to outline the outline of that fibroid and show us exactly where that stalk is and where the obstetrician needs to go in there to resect the fibroid.

Now we can also display the volume in other ways. Here is another type of display. This is a display that's very similar to a CT or an MR where you have a volume and you display it by multiple slices that are perpendicular to each other. And so here we start at one end and go to the other and we can see the submucosal fibroid in various different slices until it, when it first appears right here, until it actually disappears right there.

Now here is a longitudinal view of the uterus showing a rather thick endometrium right there. That thick endometrium is really ill-defined on this one image. And unless you had other images, you wouldn't know why the endometrium is thick. On the transverse view you get an inkling that the reason that it's thick is because it's a polyp 'cause there's a little piece of the cavity here that's separate and that doesn't, that contains a little bit of fluid. But when you render the coronal view, you can actually identify the polyp within the cavity. It's a big polyp, tiny bit of fluid outlining one of the cornua right here.

Now here is another patient who has a polyp and you can see on the 2D image that there is a polyp right here that's being measured. This patient also probably has a fibroid right here, but that fibroid is ill-defined hard to figure out where the margins are so that you can measure it. But if you then take a coronal plane, a reconstructed plane, and here we're also using a thick, technique, a thick slice technique, which is simply a technique where instead of just a thin slice you can stack several slices together and make a thick slice. Now the advantages of that is that you get more edge enhancement and here is that fibroid that we couldn't see the edges of and actually we can see the edges of it very nicely. Now it's a little blurrier because you have several slices together that you're averaging, but you do get better edge enhancement.

Here is the polyp that again, you have the edge enhancement a little better and you also can see the lining of the uterus or the endometrium as separate from it.

You can also turn on the color after all 3D. Ultrasound is 2D ultrasound, it's just a whole volume of it so you can use the same techniques. And here we're turning on the color on this fibroid. And what do we have a small, feeding vessel right here that indicates that there is blood going to that polyp.

Here's a patient that had an endometrial carcinoma and you can see here that the endometrium is ill-defined. It's certainly thickened as indicated by the calipers. And when you turn on the colors, there's quite a bit of blood flow going on there.

Now here's a thick slice technique and even with the thick slice, I was not able to get a good edge enhancement going around this tumor. And that's because it's diffuse. It probably doesn't have a very good edge. It's probably infiltrating and very hard to get the edges to show up.

Now this patient, on the other hand had a very large what appeared to be a polyp that was protruding from the cervix. Here's the top of the uterus over here and you can see that this polyp is just poking its way through the cervix. When we turn on the color, you can see that there's a huge amount of blood flow going down through the stalk to the polyp. And in fact, there is more blood flow than I would ordinarily expect for just a polyp. And here it is in 3D, showing the vasculature to this polyp. In fact, this was not a polyp, this was a sarcoma on a stalk that was actually protruding through, the cervical canal.

Sonohysterography with 3D Ultrasound

Now if you do intend to do sonohysterography where you put a little bit of fluid in the cavity to outline any defects in the cavity, definitely do it with 3D ultrasound. Here's an example of the coronal view showing a little polyp right here that is easy to see. You put in some fluid, you take a quick sweep of the cavity and then you have all the information right there. You don't have to keep taking pictures over and over again.

Now here is a sonohysterogram. This is the normal one and you can see the transverse view of the uterus here and the longitudinal view of the uterus. By taking the sweep, taking the entire volume, you can then display any part of the cavity with the fluid in it, including this reconstructed view, which is that coronal view that we've been talking about. Once you have that view, you can take a look at it, live, which is, in this case we've got a split screen going where we've dropped down a little perpendicular line that is at right angles to the screen and displayed what we can see here, which is, a coronal aspect of this uterus filled with fluid. And this is in the, the reconstructed plane.

Now if there are polyps, you can then generate any view of the polyps. Here's the coronal view of the polyps and here you have two polyps, a little polyp right there and a bigger polyp right here. And you can measure those at your leisure after the patient is gone without getting confused as to which polyps you did measure, which one you still need to measure and then forgetting to measure one and having the patient be gone, you have all of the information that you've acquired very quickly.

Here's a patient that has just one polyp and you can see here that I've put the dot on the polyp and this helps me to identify the same spot on all three planes. This is the coronal plane again and you can see that spot on all three planes. You can also, see the difference between doing just a 2D, doing just a 3D and then doing a 3D with the addition of the fluid.

Here's a regular 2D and this shows you that there is a little polyp right here. So then we can do a 3D and show the coronal plane with the top of the uterine cavity right there. And here's our polyp right over on the side and that may be enough, but if you want to, you can also include some fluid that you can inject through a small catheter and outline the entire polyp very nicely.

You can render the surface of the polyp and we haven't really talked too much about surface rendering, but surface rendering is another option when you have a volume and if you have a fluid interface like you do right here, you can render the surface of the polyp because that's within your volume. And so this is the standard coronal reconstructed plane showing you that triangular shaped cavity with the polyp in it. Or you can then do the surface rendering of the surface of the polyp. And here we're seeing that surface. We're also seeing this surface of the catheter, which is right there. And you can take a look at that in the form of a virtual hysteroscopy, for example, sort of looking at the surface of the moon if you will.

Here's another patient. And in regular 2D ultrasound, you really can't see why this endometrium is thickened. So we really do need to introduce a little bit of fluid. The endometrium is definitely irregular here, but by introducing a little fluid you can outline these rather large, this rather large polyp and these other smaller polyps here. And then if you want, you can render the surface because you do have some fluid in there. Now you can render the surface of these polyps and take a look at them as though you were doing a hysteroscopy. That's why we call it a virtual hysteroscopy. And here's another example of the, the polyp. Now, if you were to just do a regular 2D exam, you might have only found this one polyp, which we can see longitudinally or transversely. And if the operator holding the probe had not noticed the other smaller polyp, perhaps a picture wouldn't exist of it. On the other hand, once you have the volume and you're reconstructing it and navigating through the volume, then you can identify perhaps this second little polyp, which you may or may not have seen originally, but you certainly have a picture of it even if you didn't. And here's the surface rendering of these two polyps, which, makes for a, a picture, which has some depth.

Applications in the Adnexa

Now 3D ultrasound is also very useful in the adnexa. Here's an example in the adnexa of cystic areas that certainly looked like ovarian cysts. Wasn't really sure what they were, they were ill-defined. Certainly non-specific in their appearance. But in fact, if you then reconstruct the plane that you can't scan and you will immediately see that this is a hydrosalpinx. So that tube right here is filled with fluid and it's just that the tube up here is going in and out of plane and that's why you're seeing it as little cysts. But if you generate that reconstructed plane, which we've done in the third image, you can actually display the actual tube. You can also take a look at the tube, in this kind of parallel slice imaging. And then, that will also show you as you glance through all these slices that this particular cyst is a tube.

Now this was an interesting case that I saw where this patient had a lot of pain and here was the ovary, at least I thought it was the ovary didn't know what these little areas were. They looked like little cysts, but they weren't clear cysts. They were filled in with echoes here, a little bit irregular. This cyst seen longitudinally looked like this, so it was a bit elongated, filled with echoes, low level echoes, didn't know what it was. So I went ahead and did a 3D of that area to display the scan plane that you cannot scan in. And this is what we saw, it was a tube. So here is the tube that is dilated and filled with fluid.

Well, let's go back to what we were seeing before and see if we can figure out what we were seeing. Well, we were seeing a dilated tube. This is a part of it there, there's another part of it here. There's another part of it there. This tube is going in and out of plane here. And unless you can actually generate the image that goes in and out of plane, which we have done over on the other side, you can't really appreciate that this is a hydrosalpinx. And in fact there is the ovary, which is right next to the hydrosalpinx which looks normal.

So 3D ultrasound can actually help you to learn what you're looking at in 2D. Here's another multiseptate cyst looks somewhat tubular. You might suggest that it might be a hydrosalpinx, but how can you be sure? Well, you can be sure by generating the reconstructed plane.

Now you can also use inverse mode. And inverse mode is a way to make a cast of everything that is cystic inside. Now here is a tubular cystic area which is inside the volume. Now this is a just a single 2D image, but let's see what happens if you take a volume of this and then turn on the inverse mode and make a cast of everything that's cystic inside that volume. Well here we have, we have the hydrosalpinx, we also have the fimbriated end of the tube here, which of course we didn't see before because it was in a different plane. And we also have a follicle which is located in the ovary, which is also in another plane. So you have a lot of information in the inverse mode because you've made a cast of everything that's cystic, but everything that's solid has melted away in the image.

Here's another example of a hydrosalpinx where we have made the cast. And then it doesn't matter what plane anything is in because you're imaging the entire volume and you've made a cast of everything within that volume.

Here's another example of a hydrosalpinx really easy to see once you have understood, that you need to use 3D and make a cast to see what all the cystic areas are. And lastly, this was a multitude of cysts here. Could not get this to look tubular in any way, but with the casting you can actually see that it is a tube with a dilated end.

Now here is a, an ovary right in here, hard to see, but when we do the coronal plane in this area, in the postmenopausal ovary, you will identify it perhaps a little better. Here is the ovary here with a thick slice technique. The ovary I think may be better seen in the coronal view.

Bladder and Pelvic Floor Applications

How about bladder masses? The bladder lends itself beautifully to 3D surface rendering for example, because there's fluid and here is a ureteral seal. Here are two ureteral seals and this is what the ureteral seal looks like when you image it, on surface, rendering it from within the bladder. Here is a lesion in a different patient's bladder and this is a small bladder carcinoma or transitional cell carcinoma.

One day as I was waiting to put the transvaginal probe in the vagina, I happen to press the button to take a volume. And as you can see here, I'm looking down the vagina, down the rectum and down the urethra. But whenever you take a volume, always take a look at the plane that you have reconstructed, which is a plane that you may have never seen before because you can't scan in that plane. And what do we have here? I'm gonna turn it right side up for you. We have the floor of the pelvis, we have the urethra, the vagina, and the rectum. This is an image that typically you can only get with an MRI, at least you could only get with an MRI until the advent of 3D ultrasound.

Now we can identify the floor of the pelvis very nicely and actually generate multiple cuts that show the urethra, the wall of the urethra, the vagina, the rectum. And you can actually even take a look at the mucosa of the rectum right here and at the muscles, in the floor of the pelvis and at the demarcation of the wall of the urethra and all sorts of information that you can get down there.

Conclusion: The Future of 3D Ultrasound

So how will 3D change ultrasound? Well, let me ask you, if the most favorable planes to image the female pelvis, are those directly available transvaginally, I think we've probably made do with the only options that technology has offered, which is to image the uterus on end. Now, 3D ultrasound enables us to see the image planes from any orientation that we have not had access to in the past. This provides many more capabilities than ultrasound ever had, and perhaps we'll find that the pelvis is better scanned in a plane other than the ones that we've been using.

You know, 3D imaging is not new CT and MR has used it for decades with the reconstruction of volumes in many fancy displays in any plane using soft tissue windows, bony windows, lots of different types of displays and windows. In fact, now ultrasound has acquired a similar capability. That's why 3D volume imaging in ultrasound is one of the most important advances in modern sonography. It's going to put ultrasound back, in the forefront of cross-sectional imaging. And the type of displays that we can get with this technique are infinite. I think 3D ultrasound will challenge MRI's imaging capability.

So it's really now up to us in the ultrasound community to discover the areas that have become accessible to ultrasound, because now we're able to reconstruct any plane and even scan it in real time. This progress allows us to maintain and cement ultrasound's role in the cross-sectional imaging arena. Thank you.