Elizabeth Mokrouosova, Applications Project Coordinator

Eating breakfast, tying shoelaces, writing, and even getting dressed are tasks that all of us perform daily but think little about. For those living with Essential Tremor (ET), any voluntary movement such as picking up a spoon to eat may be followed by uncontrollable shaking of the limb in use. The condition can progress to the point that sufferers’ daily lives become extremely limited. According to the U.S. National Library of Medicine, ET is a common disorder affecting up to 10 million people in the United States. Although ET is eight times more common than Parkinson’s disease according to the International Essential Tremor Foundation, it is far less known, and therefore may be more difficult to properly diagnose. To improve the lives of ET patients who have found little to no results from their medications, Mini-Circuits customer Insightec developed Exablate Neuro, an Incisionless Neurosurgery Platform.

Exablate Neuro is based on Insightec’s proprietary Magnetic Resonance (MR)-guided focused ultrasound technology, which uses high-energy sound waves to ablate a small area of tissue in the brain causing tremor. The focused ultrasound treatment is done under Magnetic Resonance Imaging (MRI) and has been approved by regulatory authorities to treat patients with medication-refractory Essential Tremor and Tremor-dominant Parkinson’s Disease in the U.S., Europe, Japan, Australia, Korea, Taiwan and Israel.

One difference between ET and Parkinson’s tremor is that ET affects the hands, head, and even voice, while Parkinson’s Disease (PD) affects the hands and legs, but rarely the head and voice. ET is present in voluntary actions while PD is present when the hands and legs are at rest. Most telling during a diagnosis is a patient’s family history. Over 50% of patients with ET have a family history of the condition, which is rarely found to be the case with PD.

The need for treatment is heightened considering that in addition to daily tasks becoming difficult and stressful, many people with ET end up socially isolating themselves out of embarrassment about their condition. The isolation may place them at greater risk for developing additional health issues such as heart attack, stroke, depression, anxiety, and early death. In a survey conducted by Frost & Sullivan of 272 patients with Essential Tremor, 43% of respondents experienced difficulty performing their job duties and 29% were forced to retire early.

Insightec’s mission is to redefine surgery by using sound waves instead of a scalpel. Sound waves pass safely through the skull, and tissue is only heated to ablative temperatures where the sound waves converge, giving surgeons precise control for the procedure. Targeted ablation of nerve tissue where symptoms are found to originate results in a therapeutic effect for patients, many of whom experience immediate improvement of the tremor in the treated hand. With no need to open the skull as in a craniotomy, this treatment reduces the risk of bleeding and infection and is completed in a single session. Patients often go home the same day and are able to return to their daily activities within a few days.

Creating the focused ultrasound platform was no small feat. To assist Insightec in finding the right Mini-Circuits model for their application, Senior Applications Engineer, Boris Benger, recommended one of our low noise, high dynamic range amplifiers. High dynamic range is imperative for detecting small signals amongst the presence of many larger signals in an MRI environment. The small signal that Insightec searches for in Essential Tremor patients is the Vim nucleus of the thalamus, a very small area of the brain that has been identified as the target responsible for causing tremors.

Insightec’s Graphical User Interface (GUI) used for locating the Vim nucleus in a patient

MRI scanners use strong magnetic fields and radio waves to generate a high-resolution image used for diagnosis, and in this case, to guide treatment. The strength of the magnetic field – measured in Teslas (T) – on which the MRI operates determines the quality of the image. Exablate Neuro can be used with 3T, or 128 MHz, offering an extremely sharp visual of the target. The platform can also be used with 1.5T MRIs.

One of the key technological challenges during the development of Exablate Neuro was delivering enough energy to the target since the skull absorbs ultrasound energy. Exablate Neuro is the first and only device that has succeeded in accomplishing this.

During the treatment, the patient lies on a treatment bed which moves in and out of the MRI scanner. A silicone cap with MRI coils is placed on the patient’s clean-shaven head and a stereotactic frame is affixed. The patient’s head is then placed within a helmet-shaped transducer, which uses advanced algorithms to help ensure that the ultrasound waves converge at the exact target with sub-millimeter accuracy according to the shape of each patient’s skull.

The Mini-Circuits high dynamic range amplifier is used in the coils to help enable precise targeting. Energy is transmitted to the prescribed location and gradually increased until the measured temperature reaches the right level needed for treatment.

The 1.5T MR Guided Focused Ultrasound (MRgFUS) Head Coil

New developments in MRI technology have been gaining traction in recent years. While Insightec was developing compatibility with 3T MRIs, the FDA issued an official statement approving 7T MRI’s. The MRI market is expected to grow to $7 billion in 2020, up from $5.1 billion in 2014. As more medical devices become available in the market, more patients have access to innovative treatments such as Insightec’s Exablate Neuro.

Ageing populations, growth in awareness about early diagnosis, and technological advancements have all contributed to growth in demand for advanced medical imaging and related therapies for patients. The United States is also experiencing an increasing prevalence of chronic diseases that require early diagnosis and timely treatment. MRI systems for diagnosis and treatment of brain disorders are dominating the market and are the most advanced tools currently available to patients and healthcare providers.

Mini-Circuits is keeping up with market demand and growth with ongoing development of products for new generations of MRI’s. We are proud to support customers advancing the state of the art in medical and diagnostic imaging technologies that will have profound impacts on people’s lives and wellbeing. We look forward to supporting Insightec’s Exablate Neuro and other groundbreaking medical applications in the future.

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