This technology eliminates the need to place cortical fiducial markers during image guided neurosurgery. As an additional and important feature, the technology is able to compensate for brain shift due to deformation of the brain during surgery.
Image-guided surgery systems (IGS) are becoming ubiquitous in medical centers. However, the full potential of such systems cannot be realized at the present due to the inordinate expense involved in getting intraoperative magnetic resonance systems. The traditional method for alignment during image guided neurosurgery involves the use of fidu- cial markers placed on the patient’s cranium. The present technology combines information gleaned from a combination of laser range scanning technology, the natural features of the patient’s cortical surface and features seen on the patient’s preoperative magnetic resonance tomograms to (1) obviate the use of fiducial markers and (2) provide for brain shift compensation. The latter feature of this technology will enable the application of IGS to other surgeries where soft- tissue deformation during surgery is of concern.
The technology is undergoing refinement and enhancement and is the basis of an ongoing 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 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:
- 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.
- Brain deformations can be measured, allowing compensation strategies for brain shift to be developed.
- 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 ultra- sound 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 ques- tion 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 technol- ogy into existing IGS systems are underway.
Intellectual Property Status
U.S. patent 7,072,705 was issued on 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.