Fibroid Center

MR-guided Focused Ultrasound

What is the ExAblate® MRgFUS treatment and how does it work?

Your doctor has prescribed the ExAblate® MRgFUS procedure to treat your symptomatic uterine fibroids because you are a good candidate for the device.

ExAblate® patient table

Figure 1. ExAblate® patient table docked to the MR scanner.

The ExAblate® device uses energy that is generated by an ultrasound source (in the patient table) and where the rays of the ultrasound are focused at a specific point in the body to create a significant heating at this focus that is much higher than anywhere else. This is similar to how the sun's rays ignite a flame when focused under a magnifying glass.

The ExAblate® system is fully integrated to a Magnetic Resonance imaging scanner (see Figure 1). The whole procedure is actually conducted inside the imaging scanner. During this procedure, the ExAblate® will use the MR imaging for planning your treatment, treatment delivery guidance and therapy feedback during the treatment of the symptomatic uterine fibroids.

Visualization of treatment

Figure 2. Visualization of the actual treatment for fibroids with the ExAblate® system.

Ultrasound is a form of energy that passes through skin, muscle, fat and other soft tissue so no incisions or inserted probes are needed. The ultrasound energy is also non-ionized. High intensity focused ultrasound energy, when focused on a small target volume, provides a therapeutic effect by raising the tissue temperature of the target high enough to destroy it. Only tissue at the target is heated well above the temperature needed to kill the tissue.

Am I suitable for the ExAblate® treatment? – Contraindications

ExAblate® MRgFUS is not suitable for all patients. Patients who have any of the following should inform their doctor so he can make good treatment choices with you.

Please discuss all these conditions with your physician so your doctor can properly evaluate your suitability for the ExAblate® therapy.

Things you must do to avoid serious harm – Warnings
Things you must do to avoid other harm – Precautions
  1. Tell your physician of all medications you take and of any risks or tendencies you may have for blood clots. Due to the period of immobilization required for the ExAblate® treatment, the risk of a blood clot forming can increase because you must lie still for so long during this treatment. If your risk for blood clots is high, your medical team may perform additional tests and prescribe additional medications during the procedure that may avert any potential problems.
  2. You will be instructed to shave all skin hair around the area that would be exposed to the ExAblate® ultrasound beam. Stubble or hair sticking above the skin surface may focus the heat on the area around the hair and result in skin burns. Your medical team will also wipe the area with alcohol immediately before treatment to remove oils to reduce the risk of skin burns
  3. You must lie very still for the entire treatment without moving. Straps or restraints may be used to help you hold your position and prevent your moving during the treatment. You will also be given medication to increase your comfort during the treatment, or reduce any painful treatment sensation that you may experience during the delivery of the therapy.
  4. You will be given a Stop Sonication button before the treatment starts which you will hold during the treatment. If you experience great pain or discomfort, push the button to stop the treatment and tell your physician your the problem. Your physician will be able to address your concern to alleviate the issue.
  5. You will need to take medicine before and during the procedure to dull your pain and make you more comfortable during the procedure. The pain is generally temporary lasting only seconds after the sonication, then it dissipates. If you are experiencing significant pain that lasts longer, you need to tell your doctor so they can give you enough medication that will allow them to alter the treatment so that they may still heat the tissue to the proper temperature to treat the fibroid.
  6. Tell your physician of any medical conditions you have that could affect your ability to lie prone on your abdomen for long periods of time. Medical conditions could include neck or back problems (herniated discs or pinched nerves), severe arthritis, etc.
Risks of having this done

Infrequent complications have been reported following ExAblate® MRgFUS treatments which are described below:

Short Term Risks - Day of Treatment up to 2-Weeks Post-Treatment

The most common potential risk associated with the ExAblate® device and procedure is pain and discomfort (mild, moderate and severe) related to the delivery of the sonication energy (heating the fibroid to temperatures hot enough to kill it) which dissipates shortly after the sonication (approximately less than 1 minute) and can be managed with judicious use of narcotic and sedative medications administered by your physician. Other risks include position-related pain due to the position you maintained during the entire treatment process which can appear after treatment within 1-3 days and should resolve quickly. These can be minimized by careful positioning at the procedure start to support the rest of the body in a comfortable position during the treatment.

If there is improper acoustic coupling (i.e., the interface between the body and the transducer gel pad has gaps), then there is a possibility of skin burn. These events are acute, occurring on the day of treatment or soon after, with red skin patches or even 2-3 degree burns. These are minimized by ensuring the skin around the area of the treatment is free of any hair, oil based product and cleaned prior to treatment. In addition, these events may be further minimized by communication with your doctor when you first feel skin pain.

You may experience numbness or tingling in your back, possibly extending down your leg. If this happens during the procedure, push the Stop Sonication button immediately and tell your doctor. The nerves in the sacrum behind the uterus may be irritated by the treatment. This unusual side effect, when it does occur, almost always resolves immediately. Rarely, women have had symptoms that have lasted up to a year after the treatment. By stopping the sonication and changing the angle of the ultrasound beam, these nerves can be avoided.

You may have soreness or inflammation in the tissue in front of your uterus, including the anterior abdominal muscles and the fat beneath the skin. This happens because sometimes these areas are heated during the procedure. This has been reported in about 10% of patients in earlier studies of the device; symptoms resolved quickly in those patients.

You may experience a blood clot (also known as Deep Venous Thrombosis, or "DVT" for short) after the procedure that is not treated emergently; you may have complications related to it if it does not resolve quickly. If this were to occur, the clot could travel to other part of the body and cause heart, brain, or lung damage.

You may experience a fever within a few days after the procedure if a large amount of tissue has been ablated. If your temperature goes above 100F for 24 hours, you should call your physician.

You may see blood in your urine or have a bladder or kidney infection because of the catheter used to drain your bladder during the procedure within days to a week after the procedure, but it should resolve completely. If you get a urinary tract infection, you may need antibiotics and it may take approximately 2 weeks to resolve.

You may have bruising in the area of the iv catheter following the procedure, similar to that experienced after blood draws which should resolve on their own within a week.

You may feel tired for several days after the procedure because of the exertion to remain still for so long.

Benefits of having this done

Most women who are suitable candidates for this procedure reported significant symptomatic improvement within 3 - 6 months of treatment, with improvement lasting for 3 years of follow up in one study. The procedure is non-invasive (i.e., not surgical scars) and may be performed in out-patient basis.

How to decide about this treatment

You must explain all your medical conditions to your physician as well as the level of pain that you are experiencing. Your physician will evaluate whether you are a good candidate for the ExAblate® treatment. Together, in consultation with your physician and caregivers, you will need to decide if you can tolerate the treatment and are a suitable candidate. Your physician will also discuss any other treatment options that are available to you.

What happens before the treatment?

Once you have been evaluated to see if you are a suitable candidate as described above and have explained to you all the risks associated with the device and the procedure, you may be scheduled for treatment. You will shave the skin over the target area. You will have a urinary catheter placed to drain your bladder during the procedure and will wear compression stockings during the procedure. Your physician may start you on medication to minimize risks of DVT. An intravenous catheter will be placed into your arm to administer fluids and medications. You will be administered medications to dull your pain and make you comfortable. You will be positioned prone on the table so that the anterior pelvis is in direct contact with the transducer gel pad without any gaps and so that you are comfortable and supported. Your heart rate, blood pressure and blood oxygen levels will be monitored throughout the procedure.

What happens during the treatment?

Treatment setup

Figure 3. Picture of a treatment set up for an ExAblate® treatment

You will be given a Stop Sonication Button to hold during the procedure. You will be moved inside the MR device (see Figure 3). If you get claustrophobic, tell someone so that you can receive medication to keep you calm. The procedure will be performed from a computer in the room adjoining the MR suite. A circulating nurse will be close to check on you and to administer medication.

A series of MR images is taken for the purpose of planning the treatment. The physician will mark the area to be treated and the machine will calculate and plan the treatment to identify the number of sonications needed to cover the area and the energy needed to perform those sonications and avoid vulnerable areas with nerves and bowel.

Initially, very low strength sonications are delivered to ensure that the MR and the transducer are aligned properly. After that, the sonications will be at full strength and will move sequentially over the area marked for treatment. After each sonication, the doctor will talk to you to make sure you are okay. You must remain still throughout the treatment session.

After all the sonications have been performed, a contrast agent will be administered through the IV catheter and a final series of MR pictures is obtained to see how well the treatment target was covered.

What happens after the treatment?

You will be removed from the machine, and you will be moved to recovery room for observation for 1-2 hours. Once you have been determined to be stable, all the monitoring equipment and catheters will be removed. Your physician will come by to evaluate you, and to explain to you the post treatment care that you may need. Your physician will let you know when you can go home, almost always the same day and when you will need to return for a follow-up visit.

When to call your doctor

If you experience severe pain that is not relieved by the medication prescription, bleeding, or fever of 100F or higher within 48 hours of treatment, call your physician. You may receive a follow-up phone call the next day, or you may be scheduled for a post-treatment follow-up visit.

Where to find out more

Call the Fibroid Center (650) 498-1108

Glossary
MRgFUSMagnetic Resonance guided Focused Ultrasound Surgery
Sonicationa pulse of ultrasound energy delivered over a period of 10-20 seconds

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