Intervention using CEUS - HD

Introduction to Contrast Ultrasound in Intervention

Thank everyone for staying to the last lecture.

What we're gonna talk about is how contrast ultrasound can help us in intervention.

I think as an ultrasound user and as an interventionist, we know that ultrasound has been a very good modality for us because it allows us to use multiple approaches and access planes for our target.

You can always say that in ultrasound intervention, if we can see a target, we can probably get to it.

The challenge for all of us in intervention is what do we do if we can't see the lesion?

The answer to that question after two days of contrast ultrasound course is that if we can't see something because there's a lack of inherent contrast between the normality and abnormality, all we need is a contrast agent.

I would say that it's probably fitting, although not desirable for me or for anyone, that this lecture is the last lecture over two day contrast course, because I hope that by the end of this talk you'll see that the use of contrast ultrasound contrast agent is a natural progression in terms of ultrasound guided intervention with all the advantages that were talked about in the last two days being summarized in the work of interventional procedures.

Ways to Use Ultrasound Contrast Agents

Ultrasound contrast allows us to obtain enhancement information in real time.

Broadly speaking, there are two ways that we can use our ultrasound contrast agent.

As we discussed previously, we can either inject intravenously, which allows us to visualize both microvasculature and macro vasculature in real time for the first time on the ultrasound.

In addition, we can also inject our contrast ultrasound agent endovascularly to look at body cavity, either physiological or pathological.

In the intravenous use, like I said in the macrovascular vasculature, what we can get is a real time angiographic like information that allows us to perform any intervention without incurring any radiation dose in the microvasculature.

It allows us to see the microvascular abnormalities of various parenchymal abnormalities and allows us to have an improved ability to differentiate between normality and abnormal tissue.

To this end, the Epsom has published some guideline for interventional ultrasound under which some emerging technologies have been discussed.

Indications for the use of contrast ultrasound in intervention have been recommended and it is under this framework that we're going to talk about clinical application.

Ultrasound contrast agent use in intervention with the aim to help us to improve our success rate, but also to avoid any complications if we can help with the contrast agent.

Applications in Biopsy Guidance

The first thing to say is that one of the most common procedures that we perform with ultrasound is a biopsy and ultrasound contrast agents help us to target area that's viable.

This is particularly important if your target lesion is large and in a large lesion, there's usually an area of necrosis centrally and contrast ultrasound can help us to avoid the necrotic area in percutaneous biopsy.

Therefore, improve our positive yield during biopsy.

It has been shown that with the help of contrast agent, we can improve our positive yield in necrotic lesion up to 10% in some cases, in certain cases where the lesion may have a component which is more vascular.

I have a case here of a papillary renal cell carcinoma, which has three negative biopsies under both ultrasound and CT scan.

When the patient returned again with a negative biopsy, we can see it on the contrast ultrasound.

There is a vascular component within this hypovascular lesion that we can see on CT.

Therefore guided biopsy on the contrast ultrasound to this vascular hypervascular area was taken.

And this returned a positive yield for this lesion.

Conversely, an area of avascularity is also important when we are choosing a target for biopsy.

In this case, we have a transplant kidney where the accessory renal artery was sacrificed during this transplant surgery, a contrast ultrasound examination was performed, which demonstrated the avascular portion of the transplant kidney.

Therefore, when we plan the biopsy, we can avoid that renal portion to allow us to avoid getting a misleading histological diagnosis in patient who has an acute renal failure for the renal transplant.

Other than looking at the vasculature, sometimes there are just lesions where we can't really see.

Contrast enhanced ultrasound can be useful in identifying biopsy targets which are poorly visualized by conventional B-mode ultrasound.

This may be a lesion which is hypervascular, or a target which is avascular surrounded by normal vascular parenchyma.

One example is hepatic abscess drainage.

On the B-mode ultrasound, it's very difficult to delineate exactly where the pocket of abscess is within the liver.

But with the help of IV use of contrast and ultrasound contrast agent, we can see the avascular portion that allows us to target our drainage successfully.

The same principle can be used in a hypervascular lesion.

We can either use contrast ultrasound to help us to identify the lesion that we have already seen in other modality, or alternatively, sometimes the contrast and hand zone may show up other lesions that wasn't seen in other modality, and allow us to take a different approach and take a biopsy from another lesion.

If your target of intervention is adjacent to a normal parenchyma which you want to avoid causing any damage, such as in the case of a subcapsular renal abscess, what you could do is use contrast enhancement on the ultrasound to show the boundary between the collection and your normal parenchyma.

Therefore, you can target your collection with confidence without knowing exactly where to avoid puncturing, to avoid additional damage to your underlying kidney.

Nephrostomy Procedures and Needle Visualization

In this case, one of the common procedures to be performed on the ultrasound is a nephrostomy and the worst kind of ostomy, or when you put the ultrasound probe, someone has tried to put a nephrostomy before there's a large pararenal collection, there's a lot of blood, a lot of pus in the renal calyceal system.

On the B-mode ultrasound, you just can't identify where the calyces are.

What you could do is if you inject IV contrast, what you can see is the avascular portion of the calyces, and you can target those areas and make a procedure much easier.

Contrast can not only help your target, sometimes the difficulty of a biopsy procedure is to actually see the needle fine needle that you're using and to see your needle.

What you need to do is to optimize your position, but if you can increase the visibility of your needle, that will also help in terms of getting success for your procedure and just taking the nephrostomy.

Again, as an example, what we do here is taking the stylet out from a fine needle for nephrostomy, which flush needle with a tiny drop of a microbubble contrast.

You can see that under the contrast ultrasound, you can see the needle very clearly.

In addition to this, what we also notice is that when we make the successful puncture, you can see a positive visual confirmation of your success on the contrast ultrasound.

I'll show you the picture and what I want you to focus on is the way the microbubbles are flushed out from the needle by the pressure of the collecting system of the urine flow from your needle.

As you enter the collecting system, you can see the contrast being washed out.

The video is on the loop, so that's why it's coming back again, but it's right.

Treating Transient Vascular Targets: Endoleak Example

The other thing is sometimes your target can be transient, particularly if it's a vascular target.

I think yesterday when we were talking about endoleak in our aortic session, there was a question about percutaneously treating an endoleak on the ultrasound guidance.

This is what we did here.

This patient had a type two endoleak in an unusual 11 centimeter sac arising from the internal iliac artery, which was previously treated with a stent graft over the origin of the internal iliac artery and multiple coil embolization of the distal branches.

He returned presenting with abdominal pain and hydronephrosis.

The other thing I forgot to mention is that he's also 95 years old, so the surgeon didn't want to go anywhere near him.

The difficulty of treating it percutaneously was to identify the enhancing portion within the large sac under the CT or fluoroscopy, because what we really need to have is a real time angiographic information.

On the CT scan, unless you inject contrast continuously, it's very hard to highlight those areas.

Also the metallic artifact from the previous coil made the procedure difficult, but it actually was fairly straightforward on the contrast enhanced ultrasound with an enhanced channel identified on the ultrasound scan, and we can directly puncture that area.

We injected thrombin onyx and treated endoleak successfully.

Ablation Procedures

With the same principle as biopsy, we can use contrast ultrasound to help us to guide our ablation procedure for various cancers.

Contrast ultrasound is safe and effective, and the enhancement information that we get is comparable to CT or MRI in terms of guidance and also per procedure monitoring.

In terms of the success of the ablation therapy, this is a procedure performed by one of my colleague Dr. Yusef. He performed an ablation of a liver lesion successfully.

Following the procedure, you can see the loss of vascularity of a liver lesion on the contrast ultrasound.

The procedure can be completed with immediate confirmation with ultrasound with an ultrasound scan.

This is another case of a renal lesion.

The first picture that you're looking at on the right is a renal cell carcinoma after the first cycle of ablation and what you could see is that there's residual vascularity within that lesion.

What we then do is carry our second ablation cycle.

On the completion contrast ultrasound study, you can see the complete loss of that vascularity within that lesion to confirm that we have treated this lesion successfully.

Post-Procedure Confirmation and Emerging Applications

Like I said, a lot of these procedures you may have noticed are tailor made for specific clinical questions.

There are many emerging applications which are not listed in the guideline.

These include the use of contrast which we talked about in various tubes and ostomies to help us identify the success of a drainage procedure.

Nephrostogram is one procedure that we found particularly useful.

Once we complete the nephrostomy puncture, what we do then is inject diluted contrast agent into the nephrostomy tube.

This first confirms for us a successful placement of the tube within the collecting system.

If there's any pathology within the ureter, as in this case where there's a distal stricture, we can identify that and this can be performed at bedside.

If you receive a request to check the nephrostomy position, you can do this easily with an ultrasound machine at the bedside rather than bring the patient down, which may cause additional risk if a patient is unstable.

The patency of ureter can be confirmed by seeing the flush of contrast running into the bladder.

This can be visualized very clearly on the contrast ultrasound study.

Monitoring Complications: Pseudoaneurysms and Fistulas

One thing that's important is to help us during the procedure, but what's also important is to have a modality that helps us to identify complications when they occur.

What we can do is using the vascular application of contrast ultrasound to monitor our femoral punctures, which are very regularly performed in any interventional radiology department.

In a puncture site where there's small leak of bleed, sometimes active bleeding cannot be readily identified on Doppler study due to slow flow.

But if there's any extravasation, this can be clearly seen with contrast ultrasound study.

If a pseudoaneurysm forms, usually this can be treated percutaneously with thrombin injection under the guidance of color Doppler ultrasound or conventional ultrasound.

But sometimes if the anatomy of the pseudoaneurysm is complicated with fine channels, then additional use of contrast enhanced ultrasound may allow us to study the morphology of pseudoaneurysm much more clearly and allow us to plan our procedure more carefully.

You can see that following a successful thrombin injection, the contrast agent disappears from the pseudoaneurysm, which is now thrombosed and no longer filled by the intravascular contrast volume.

Following a biopsy, pseudoaneurysm within the kidney or the liver is also a potential risk.

These can rupture and bleed.

If we can identify them, we can then plan for an embolization procedure.

What I find particularly useful is that following your embolization procedure, what you could also do is perform an in-table contrast study to confirm that the pseudoaneurysm that you identified previously is successfully embolized before you take the patient off the table and return back to the ward.

Particularly if you're on call at night, you don't want to be called again at 3 AM in the morning.

We've been trying to do some early studies to look at fistulas following biopsies.

These are some studies looking at the time intensity curves following the formation of AV fistula following transplant kidney biopsies just to study whether there's any shunting and hemodynamic information linking to clinical deterioration of renal functions.

We have a very small number, but this is just to highlight the fact that with the use of ultrasound contrast agent, there's a lot more hemodynamic information that we can get in terms of studying the microvasculature.

Ultrasound-Guided AV Fistula Angioplasty

We can also use the fact that this is an intravascular agent to study larger vessels.

One of the procedures that we perform regularly is ultrasound guided AV fistula angioplasty.

The reason to do it on the ultrasound guidance rather than fluoroscopy guidance is that we select a group of patients who have the fistula formed and they're waiting for the fistula to be matured.

But these are patients who have a deteriorating renal function, but not yet on dialysis.

Any fluoroscopy guided procedure with our IO contrast will be detrimental to the remaining renal function.

These procedures can be performed by ultrasound alone.

But what we find is that the advantage of using ultrasound contrast agent is one, improve the visualization of the morphology of any type of stenosis.

As we've seen already in our carotid artery lecture yesterday, to distinguish a tight stenosis or near occlusion is very difficult with the artifacts associated with color Doppler study, but with contrast ultrasound agent because the normal anatomy is not seen on the contrast ultrasound specific mode.

All we see is enhancement internally.

We can see the intraluminal morphology very clearly and that allows us to guide our needle and plan for treatment for this procedure.

But I guess more importantly, a lot of these procedures are performed as a day case.

We perform the procedure in the morning and the patient goes back home late afternoon.

Before we send a patient home, we need to make sure that there is no complications.

We found that the use of ultrasound contrast agent improves our safety profile.

The reason for that is that we can conclusively exclude an active extravasation from a puncture site.

This is an example of a contrast extravasation following balloon angioplasty on the first image on the right, you can see this contrast leak outside the lumen of our fistula.

But following treatment, which what we do as a standard procedure is performing a prolonged balloon inflation over the rupture site, that usually stops the bleeding.

You can see that on the subsequent study, we can be safely reassured that there is no further extravasation whereas on the color Doppler study on the B-mode ultrasound is very difficult to be completely reassured before we discharge a patient.

Endocavitary Contrast Use

I think other emerging application is what we've talked about in previous lectures, the use of endocavitary ultrasound agent into the collections.

The benefit of this is that this can help us to first of all confirm the correct placement of any tubes that we place in the collection.

Allow us to estimate the volume of our collection.

Also if it's a multilocular collection where there are multiple pockets, you want to make sure that your drain comes in communication with all the pockets that you wish to drain.

This can be placed into any tube in the body.

This is a liver abscess.

It can clearly be placed in the pleural spaces as well to identify an empyema effusion.

But what we found really with this procedure is the real strength, which cannot be replaced by any other procedure, is to identify when there's a fistula between a collection and other internal organs.

Here I have a case where contrast was injected down the ureter, there was a ureteric injury and the contrast was leaking out into a collection.

But as we scan the patient in real time, all we notice is that there's enhancement within the small bowel loops which shows peristalsis.

What this is showing us is that there's real time transition of the contrast from the ureter into the abdominal collection into the bowel loops.

This patient has a ureteral enteric fistula, and this cannot be visualized in any other modality in real time other than contrast enhanced ultrasound.

Any fistula that's formed can be followed and identified.

We have seen previously by the work of another of my colleague Dr. Dhi on demonstrating a fistula between a hepatic artery and the biliary.

This is the benefit of using endocavitary ultrasound agent to detect any complications.

Avoiding Unnecessary Interventions and Diagnostic Value

I think one other thing I just want to mention is that it's always said that the only way to avoid any complication or intervention is not to do any intervention.

If you have procedures that you have a modality that allows you to not to do any intervention, that will help you to avoid the complication that associated with intervention.

I think that's a crucial point for ultrasound agent for interventional procedures as well.

We talk about the improved diagnostic value of contrast enhanced ultrasound in various organs.

Here we have a solid looking lesion within the kidney, but it shows no enhancement.

It's probably a complex hemorrhagic cyst, but the fact that there's no enhancement allows us to take conservative management to carry on monitoring this lesion rather than sticking a needle in with possible cause of any bleeding complication to this patient.

Diagnosing Endoleaks with Contrast Ultrasound

This is a case of contrast ultrasound agent using the macrovasculature.

These are demonstrations of different endoleaks in patients and following an aortic stent graft placement of aortic aneurysm, usually if there's an endoleak depending on the type of endoleak, this requires additional treatment.

But we have a patient with a rare type four endoleak.

As discussed yesterday, these are very rare.

What you can see, and the reason why I want to show you the scan is that you can see the power of contrast ultrasound.

You can see individual bubbles jetting through the fabric of the stent graft that allows us to make the diagnosis of a type four endoleak confidently.

With a type four endoleak, it's usually related to the coagulation status of patient.

If we are sure that this large endoleak is a type four, we can monitor this patient with serial scans.

By doing that, what we can do is also monitor this patient under contrast ultrasound without repeat CT examination.

You can see after 24 hours, there was already reduction of the size of that endoleak around the stent graft and the endoleak completely disappeared after 48 hours.

All this is performed without any additional nephrotoxic contrast to the patient or any radiation dose incurred.

Fusion Imaging with Contrast Ultrasound

One last thing I want to talk about is that with new technologies, what we can also do is to get the help with CT and MRI and fusion imaging can be useful in ultrasound guided procedures in lesions that's difficult to visualize.

When we perform fusion, we can also perform it with ultrasound contrast agent.

This is a procedure that performed recently and there's a small target of a type two endoleak.

With the help of fusion, we can identify the anatomy and morphology of the stent graft in relation to the endoleak.

Should we decide to perform treatment for this endoleak percutaneously, it will allow us to target this area much more easily with the help of ultrasound and CT guidance.

Conclusion

I just want to conclude that again, the use of ultrasound contrast agent is a natural progression of ultrasound guided intervention.

You'll probably find that the whole talk that I've just given is a revision of the old areas that we've covered in the last two days.

But what we do find is that performing intervention on the contrast ultrasound, it does offer potential to address specific questions that you may encounter and you can tailor major solutions to individual clinical challenges that you may face.

I would just like to conclude by thanking all my colleagues who have helped in the work of contrast ultrasound intervention.

Thank you.