From knee surgeries to appendectomies to cardiovascular procedures, the last two decades have witnessed the emergence of a trend that has dramatically impacted the way doctors perform surgery. Physicians and patients alike have grown to eschew the invasive, open surgeries of the past in favor of minimally invasive alternatives that allow for precise surgical solutions with less disruption of healthy tissue and quicker recovery times. In orthopedic surgery, endoscopic visualization now enables 1.2 million minimally invasive procedures a year. Fluoroscopic visualization guides 1.4 million cardiovascular interventions each year. Over 4 million minimally invasive abdominal surgeries are performed each year using laparoscopic visualization. The connecting thread across all of these procedures is real-time image guidance because intraoperative visualization satisfies the need for surgeons to see their work while simultaneously minimizing the risk to patients.

Despite this strong trend, minimally invasive neurosurgery is still performed blind in most cases. Visualization in neurosurgery is a challenging prospect. The above-referenced imaging platforms do not work as well on the soft tissue of the brain, nor can they provide three-dimensional detailed views of the brain’s intricate substructures. Only one imaging modality is capable of meeting these requirements: magnetic resonance imaging (MRI). The gold standard for diagnostic imaging of the brain for many years, MRI is the ideal platform for guiding minimally invasive, therapeutic interventions in the brain. However, a bridge between the powerful imaging capabilities of MRI and its application to real-time visual guidance in minimally invasive brain surgery did not exist until recently. The solution, developed by MRI Interventions, is the ClearPoint Neuro Intervention System. 

Platform Design and Operation

The ClearPoint Neuro Intervention System is a unique platform that enables real-time, MRI-guided, minimally invasive brain surgery.  It is an integrated system of intuitive, menu-driven software, disposable components, and reusable hardware. The software runs on the ClearPoint workstation and provides guidance to a surgeon during the planning, targeting, and delivery phases of a neurosurgical procedure. The disposable components are built around a small, head-mounted trajectory guide called the SmartFrame device. The reusable hardware components include a head fixation frame and an imaging head coil.

ClearPoint procedures are performed within a hospital’s standard, existing diagnostic MRI suite. The system is compatible with scanners from Siemens, GE, Philips, IMRIS and Brainlab, at both 1.5T and 3T field strengths.

How It Works

Patients undergoing the procedure are first placed under general anesthesia. The patient’s head rests inside the head coil and fixation frame. An MRI-visible matrix called the SmartGrid is applied to the patient’s head, and the patient is advanced into the isocenter of the MRI scanner to begin the procedure. The MRI scanner begins obtaining high-resolution images of the patient’s neurological anatomy and communicates the images in DICOM format to the ClearPoint workstation, which presents the images to the physician via the ClearPoint software.

From these high-resolution images, the surgeon sees and selects the neurological target. Once the target is selected, the surgeon uses the software to find an optimal trajectory from the surface of the skull down to the neurological target in the brain. The software assists in this process by visualizing critical structures that need to be avoided, such as blood vessels, sulci, and the ventricles. With the trajectory determined, the entry point is then identified on the patient’s head via the SmartGrid. The software recognizes where the planned trajectory passes through the MR-visible SmartGrid and identifies the specific coordinates to the physician. The top layer of the SmartGrid is then peeled back and the coordinates are used to guide the surgeon in marking the location of the entry point on the patient’s head.

After a small entry point is created, the surgeon affixes the SmartFrame device to the patient’s head. The SmartFrame is a precision-geared device with four degrees of freedom:  pitch, roll, X, and Y, which are actuated with four small, color-coded control knobs. Similar to the SmartGrid, the SmartFrame trajectory guide is also MRI-visible. With the SmartFrame attached to the patient, another set of high-resolution images is acquired and presented to the physician to reconfirm the location of the neurological target and the optimal trajectory. The new images take into account any shift in the brain that might have occurred during the procedure.

With the SmartFrame and patient anatomy in a common 3-D imaging surgical space, the interventional portion of the procedure is simple. The ClearPoint software is aware of both the planned trajectory and the SmartFrame trajectory. It then guides the surgeon in the adjustment of the SmartFrame control knobs until the SmartFrame trajectory is aligned with the planned trajectory. With everything properly aligned, the surgeon then inserts the interventional device through the center lumen of the trajectory frame. As the device is advanced through the brain, the surgeon observes real-time images to ensure that no undesirable events have taken place, such as hemorrhage, and to confirm that the desired neurological target has been reached.

A Range of Neurosurgical Procedures

The ClearPoint system facilitates a wide range of neurosurgical procedures. The target patient populations for ClearPoint are the 2.2 million individuals in the U.S. (over 4 million worldwide) who suffer from treatment-resistant neurological disorders, such as Parkinson’s disease, treatment-resistant epilepsy, and glioblastoma multiforme brain tumors, among others. Procedures enabled by the ClearPoint system include “asleep” deep brain stimulation (DBS) surgery, laser ablation treatment, and direct drug delivery. 

"Asleep" Deep Brain Stimulation

Patients with progressive neurological illnesses like Parkinson’s disease, for whom medication tends to lose effectiveness, can often benefit from deep brain stimulation (DBS).  However, without ClearPoint, these surgical procedures typically require the patient to be awake and off medications throughout the entire surgery. Not surprisingly, many patients are unwilling or unable to undergo an awake brain surgery. ClearPoint provides a solution for these patients by enabling an "asleep DBS" procedure, which allows patients to sleep through surgery under general anesthesia and remain on their medications. An estimated 150,000 patients suffer from late-stage Parkinson’s disease and potentially could benefit from an “asleep DBS” ClearPoint procedure.

Awake DBS surgery can also be daunting, and often prohibitive, for young patients, such as those suffering from pediatric dystonia. The ClearPoint system provides these patients with a potentially life-changing treatment option that would otherwise be unavailable to them through traditional means.

Laser Ablation

A quarter million people in the U.S. suffer from treatment-resistant epileptic seizures. While a surgical option exists--resection of the affected tissue--this procedure is traditionally highly invasive, involving an open craniotomy. Using new laser ablation technology in conjunction with the ClearPoint System for guidance and visualization, surgeons can now pinpoint an area of tissue for destruction, watch the laser as it reaches the neurological target, and confirm precise ablation of the targeted tissue, obviating the need for an invasive craniotomy. 

Using the same technique, this can be used to target and attack brain tumors, enabling high-resolution visualization as the tumor is destroyed from the inside out. Thirty thousand patients in the U.S. might benefit from a targeted laser ablation procedure.

Direct Drug Delivery

Finally, ClearPoint is providing solutions to an array of longstanding challenges inherent in delivery of drugs to diseased tissue in the brain. Central to these challenges is the fact that systemic delivery of drugs to the brain often fails because the body’s blood brain barrier (BBB) prevents the drug from ever reaching the diseased area. And, attempts to administer the drug by direct injection often fail because the delivery procedure is performed blind.

The ClearPoint System resolves both of these issues. Using ClearPoint doctors can bypass the BBB and ensure the drug reaches the neurological target because the entire procedure, from initial placement of the drug delivery cannula throughout the drug infusion, is fully visualized in real time.

ClearPoint’s unique capability in drug delivery has led to its inclusion as the delivery platform in a growing number of clinical trials, including two drugs for treating Parkinson’s disease and three drugs for treating malignant brain cancers.

Gaining Commercial Traction

The ClearPoint Neuro Intervention System was developed by MRI Interventions, Inc. (Memphis, Tenn./Irvine, Calif.) and is currently installed at 25 sites in the U.S. and Europe, including Brigham and Women’s Hospital in Boston; MD Anderson in Houston; Emory University Hospital in Atlanta; and the VA Hospital in San Francisco. Movement into new sites continues as surgeon and patient awareness grows.

A growing number of peer-reviewed journals, including Journal of Neurosurgery and Journal of Stereotactic and Functional Neurosurgery, have published articles regarding ClearPoint. Recently a research team led by Dr. Philip Starr, Professor of Neurological Surgery and Dolores Cakebread Endowed Chair in Neurological Surgery at University of California, San Francisco (UCSF), and Dr. Jill Ostrem, neurologist and Associate Professor at UCSF, presented data at the International Parkinson and Movement Disorder Society’s 2013 Congress regarding the positive outcomes in a group of pediatric dystonia patients who underwent “asleep DBS” procedures with the ClearPoint System.   

National patient advocacy groups are also taking notice of the life-changing potential this technology represents. “Asleep DBS” was featured in the American Parkinson Disease Association’s 2013 Summer newsletter.

Through direct MRI guidance and precision targeting, the ClearPoint System is making available treatment options for a host of patients who have for years been stuck between unworkable conventional treatments and otherwise untreatable neurological disorders. ClearPoint represents neurosurgery’s coming of age, into the era of real-time visualization, finally catching up to the fields of orthopedic, cardiac and abdominal interventions in realizing the powerful potential of intraoperative image guidance. 


Kimble R. Jenkins is president and CEO of MRI Interventions Inc. (kjenkins@mriinterventions.com