Navigating Through the Brain

Image Guided Surgery with microscope image injection aids visualization and orientation during neurosurgery

March 20, 2017

One of the challenges of neurosurgery is orientation at the surgical site. When resecting tumors, removing arteriovenous malformations, or clipping aneurysms, surgeons often have to work near healthy and functional brain tissue. When resecting the tumor, the challenge is always to spare as much healthy tissue as possible. Neuronavigation technology, also referred to as Image Guided Surgery (IGS) enables surgeons to plan the ideal approach before making a cut and helps to execute that plan by providing intraoperative orientation.

 

At the base of the human skull there is a particularly high concentration of vital structures: blood vessels, nerves, centers for hormonal control of bodily functions, and centers for regulating breathing, blood pressure, and heart activity. Brain tissue cannot regenerate itself, so even the smallest injury can cause irreversible, profound brain damage, leaving patients with a permanent disability. This also makes the treatment of disease very difficult. Malignant gliomas, which account for 45% to 50% of all brain tumors, infiltrate into brain tissue as they grow. Even under a surgical microscope, peripheral tumor regions are hard to differentiate from healthy tissue.

Continuous real-time view of the surgical field

Neuronavigation works like a GPS system, enabling accurate position tracking of instruments within the patient’s anatomy. Surgeons can outline the tumor, identify organs at risk, and define the optimal access pathway to the tumor to prevent injury to healthy structures.

Before surgery, CT or MR images of the patient are taken. In the operating room, the navigation system matches these images up with the live patient images using a wireless laser pointer. The pointer identifies surface points on the patient’s skin which are transmitted to the navigation system via an infrared camera. During the procedure, the camera also transmits the locations of the instruments and equipment – including the microscope – which are outfitted with reflective markers.

The patient images prepared prior to surgery are loaded into the navigation system and reconstructed into images on the monitor or injected into the oculars of the surgical microscope. This gives the surgeon a continuous, real-time map of the position of the instruments in relation to the brain structures and the tumor.

Image injection for a complete picture

To view the neuronavigation data, surgeons normally need to raise their heads from the microscope to look at the navigation screen. Thanks to image injection systems, like the new CaptiView from Leica, and in combination with the new picture-in-picture feature from Brainlab, the surgeon can see navigation data directly in the microscope’s eyepieces. The full-HD display of CaptiView image injection with LED backlighting provides bright, crisp injected images with distinct margins. Neuronavigation data from the IGS system can be viewed either in the right, the left, or both eyes and the CaptiView system is also able to display real-time HD images from an endoscope and FL800 vascular fluorescence. ”By having all information directly in the microscope’s ocular, the surgeon does not have to reorient between the microscope and the navigation screen, but can remain fully concentrated on the patient during the whole procedure”, explains David A Smith, Product Manager at Leica Microsystems. Furthermore, injected images are also displayed in the assistant binoculars and can be recorded in full HD quality, supporting teaching both inside and outside of the OR.

Microscope integration offers new imaging options

Brainlab is one of the market leaders in the field of image-guided technology and was the first to work together with Leica to integrate its neuronavigation software with surgical microscopes. The latest microscope integration software from Brainlab works seamlessly with CaptiView image injection and M530 microscopes from Leica allowing data to be injected into the microscope’s eyepiece and additionally displayed on screen. With improved 3D visualization, the new Brainlab software provides a more realistic representation of planned objects, structure and fiber tracts throughout the entire procedure.

Touch-based rotation of the microscope view on the navigation screen allows for a look behind the actual video plane to reveal underlying structures in 3D for more anatomical insight. The “Probe’s Eye” feature reconstructs the patient dataset to the microscope’s position and orientation for a direct comparison of preoperative data and intraoperative anatomy. With “Navigation update” the surgeon is able to correct initial registration based on the patient’s anatomical landmarks.

Figure 1: Microscope integration with Cranial Navigation application, viewed with CaptiView image injection.

Limiting guesswork in tumor resection

Every neurosurgical procedure demands a vast amount of surgeon experience, patience and competence. Although neuronavigation does not replace surgical skill, it effectively supports the surgeon in pre-operative planning and during the procedure by giving more precise information in the most critical moments.

"The integration of the microscope with neuronavigation helps the surgeon to accurately identify questionable areas", explains Valentin Elefteriu, Product Manager Augmented Reality at Brainlab. "For example, if they focus on the edge of a tumor and can’t tell exactly where the tumor tissue ends, a look at the pre-planned anatomic data with microscope image overlay reveals whether the focused area is part of the tumor or not. Precise planning may also minimize head shaving, skin incisions, and bone flap sawing and thus reduce stress for the patient.”

 

 

Brainlab is a registered trademark of Brainlab AG registered in Europe, the United States and other countries.

 

 

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