This technology is fundamentally a new way to align a patient in an image-guided surgery system (registration) without the use of fiducial markers on the cranium exterior. The system utilizes laser range scanning technology, the natural features on the cortical surface and the corresponding natural features derived from the patient’s preoperative magnetic resonance tomograms. In addition, the technology is amenable to measuring deformation (brain shift) for use within a mathematical model-based strategy for shift compensation.
This technology could augment any existing image-guided surgery system. The next horizon for IGS is compensation for soft-tissue deformation. The vast majority of medical centers can afford IGS systems but cannot afford dedicated intra-operative magnetic resonance (iMR) imaging suites. This technology allows for the registration and tracking of deformations within surgery without that expense. It also directly supports the complimentary models for brain shift compensation. IGS systems, both in approach and equipment, are economically scalable to an unprecedented level, whereas iMR has significant medical center infrastructure costs associated with adoption (e.g. space, staffing, maintenance, etc.). In five years, image-guided surgery systems are expected to routinely provide some mechanism to compensate for soft-tissue deformation. As image-guided surgery attempts to move out of the cranium for application, it will be even more important to utilize an approach like the one described here. There is little doubt that effective compensation will open up new markets as this technology is applied to other organs. As an example, image-guided neurosurgery was not generally reimbursable a decade ago, but now is the standard of care.
The technology is undergoing refinement and enhancement and is the basis of an on-going 40-patient study to qualify the method for both registration and deformation measurement. Methods continue to evolve for implementation and to take full advantage of the unique patient data from this study.
To date, preliminary versions of the registration strategy have been tested in approximately 12 clinical cases. The deformation measurements have been tested with two clinical cases. Several phantom experiments were also conducted that show each strategy works under controlled experimental conditions.
A second prototype intra-operative acquisition system was just completed, and this system has been tested in a small number of neurosurgical cases. This work is currently supported by an NIH grant that will to continue for approximately two more years.
As clinical data is collected and application is made to actual neurosurgical data, the system and methods are being validated concurrently with image-guided systems.
This revolutionary approach has three distinct advantages: (1) Registration is accomplished off the brain surface; therefore, this method should be more accurate in the presence of shifts upon durotomy than approaches using outer-cranial fiducials. (2) Brain deformations can be measured, allowing compensation strategies for brain shift to be developed. (3) The overlays provided by this technology provide new spatial cues to surgeons to aid orientation in the intracranial environment.
Current Competitive Products
From the perspective of registration, this technology could replace or augment any registration method that uses external fiducial markers or features. Currently, nothing is used to measure and compensate for brain shift except for intra-operative imaging (magnetic resonance and ultrasound primarily). Magnetic resonance is neither practical nor economically scalable. Ultrasound is a good candidate; however it does not have the soft tissue contrast necessary. It should be noted, however, that the overall strategy the development team is working towards includes intra-operative ultrasound as a part of the technique.
Neurosurgeons will prefer this technology since the technique performs registration compensation for brains that deform upon durotomy, which is a common occurrence that compromises any registration solely dependent on external fiducials. Hospitals will prefer it because it should improve the quality of image-guided surgery at minimal cost. The approach will provide some compensation for deformation but in a platform that is on the same order of cost as a standard-of-care IGS system. It will not require new infrastructure to be built within the hospital operating rooms, nor excessive staffing and maintenance costs. Ultimately, by providing better guidance to the neurosurgeon, the hope is that better resections will be facilitated on a more routine basis. It has been shown in the literature that more complete resections do improve patient outcome for brain tumor patients.
Use of this technology has shown (1) that quality laser range scans (LRS) of the brain surface can be achieved, and (2) that registration by use of the cortical surface is achievable and accurate. There are no barriers within today’s standard operating rooms that prevent its adoption, as it has minimal impact on surgical times or space requirements. The adoption of this technology would be no different than the adoption of other digitization equipment into the operating theater.
Some investigators raise the question of the adequacy of available computer processing to solve the relatively large number of equations required in a time frame that is appropriate for the surgical suite. Current and rapidly evolving computational ability and speed suggest that this is readily addressed by devotion of the appropriate computer resources at a reasonable cost.
The goal is to translate this technology to the clinic in a meaningful way. It is anticipated that with appropriate personnel and resources, this technology could be developed into a product prototype in 1-2 years. Efficient strategies for the integration of the laser range scanner technology into existing IGS systems are underway.
Intellectual Property Status
- issued July 4, 2006 covering apparatus and methods of brain shift compensation. A pending U.S. non-provisional patent application addressing the cortical surface registration and deformation tracking is under examination, and significant claims having already been allowed by the Patent Office. Dr. Miga is a member of an internationally-recognized team that continues to create leading edge technologies for image-guided surgery.