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Raymond Schulz, Voxel
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Kay Paumier, Communications Plus
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For Immediate Release
Holograms Overcome Some Limitations of Traditional Stereotaxy for Complex Neurosurgeries, Doctors Report
Philadelphia -- April 27, 1998 -- The Digital Holography(tm) System from Voxel(r) (NASDAQ:VOXL) may be more cost-effective and reliable than frame-based stereotaxy for complex neurosurgeries, physicians will report this week at the annual meeting of the American Association of Neurological Surgeons (AANS).
The Digital Holography System uses data routinely collected by Computed Tomography (CT) and Magnetic Resonance (MR) scanners to produce true three-dimensional images. A proprietary multiple-exposure process holographically superimposes all the cross-sectional data from the tomographic studies onto a single piece of 14"x17" holographic film. When the film is viewed on a special lightbox, the transparent Voxgram(r) images literally extend out in space, enabling physicians to interact in, around and through the life-size holograms as if they were real specimens of anatomy.
Holography More Accurate and Less Expensive than Frame-Based Stereotaxy for Large Craniotomies
Dr. John Collins, Chief of Neurosurgery at Tripler Army Medical Center (Honolulu), compared MRI-derived holography with frame-based stereotaxy for intricate brain surgeries.
MRI data from three patients with brain tumors was converted into holograms. Noting that the "detailed, life-sized, three-dimensional images vividly and accurately depicted" each tumor, Dr. Collins determined the desired excision boundaries by measuring the tumor within the holograms. Using "easily recognized landmarks," the surgeon then directly cross-referenced the measurements taken from the holograms to similar measurements on the brain and found that "the holograms matched the actual intraoperative cortical surface appearance." Dr. Collins concluded that "during small craniotomies in which the problem of brain sag and shift is minimal or non-existent," navigation by holograms demonstrated "close correlation with results obtained using frame-based stereotaxy." In craniotomies that involve large exposures, holograms appear to be "more reliable than frame-based stereotaxy because measurements within the hologram remain consistent despite the brain shift or sag that develop during resection." Noting that "other solutions to overcome the problem of brain shift during surgery require very large capital investment for the purchase of highly specialized facilities," Dr. Collins stated that "holography may provide the most cost-effective means to achieve accurate neuronavigation during large-opening craniotomies at a cost that is easily manageable at most community medical centers." (MRI-Derived Holographic Neuronavigation Compared to Frame-based Stereotaxy to Determine the Resection Boundaries for Complete Excision of a Dominant Supplemental Motor Cortex Oligodendroglioma, Burton BS, Collins JJ, Schulz RA, Geil GE, Stereotactic and Functional Surgery Program, Scientific Poster 1310)
Holography Overcomes Certain Limitations of Stereotaxy for Cannulation of Cysts
Dr. William C. Bergman, Associate Chief of Neurosurgery and Director of Neurosurgical Research at Santa Clara Valley Medical Center (San Jose, California) and Associate Professor of Neurosurgery at Stanford University Medical Center (Palo Alto, California), investigated the efficacy of holography for cannulation of cysts within the brain.
A Laitinen stereotactic frame (Sandstrom Technologies) was placed on each of the six patients, three of whom presented complex trajectory problems, prior to performing the CT scan. Three-dimensional holograms were created from CT, MR and MRA data. The transparent Voxgram(r) images were superimposed over each other, "demonstrating the spatial relationships of these structures with regard to each other. The resulting image clearly demonstrated cystic structures, ventricles, vessels and pre-existing catheters, all within the skull and stereotactic frame." Using the hologram as a phantom, Dr. Bergman placed the actual stereotactic frame within the holographic image, chose the optimal trajectory, and adjusted the articulated arm of the stereotactic device. Subsequently, Dr. Bergman used the frame "to effect stereotactic placement of the cannula in the usual manner."
Dr. Bergman concluded that the combination of holography with the Laitinen stereotactic frame successfully overcomes certain limitations of traditional stereotactic techniques alone.
(An Improved Stereotactic Technique for Cyst Cannulation, Bergman WC, Norbash AM, Schulz RA, Geil GE, Shatsky SA, Stereotactic and Functional Surgery Program, Scientific Poster 1293 )
Holography Compensates for Abnormal Brain-to-Skull Relationships in Complex Cranioplasties
Dr. Bergman also examined whether holography could compensate for abnormal brain-to-skull defect relationships in complex cranioplasties. In such cases, traditional cranioplasty techniques have serious drawbacks. Transparent holograms were made from CT sections of the area of the defect and mirror-image holograms made of the intact side. Dr. Bergman superimposed the hologram of the skull defect over the mirror image of the opposite side, creating a "perfect cranioplasty outlined by the defect edge." A plasticine model was molded within this three-dimensional image. Additionally, the skull-defect hologram was superimposed over a hologram of the brain, rendered from the MRI. The inner surface of the model was then built up or hollowed out to accommodate the contour of the brain surface. A negative mold was fashioned using the plasticine model, and a cranioplasty of methyl methacrylate was then molded. Dr. Bergman concluded that "this method facilitated an excellent cosmetic fit with little or no dead space" particularly in cases with abnormal brain-to-skull relationships. (Cranioplasty Technique Which Compensates for Abnormal Brain-to-Skull Defect Relationships, Bergman WC, Prolo DJ, Shatsky SA, Schulz RA, Geil GE, Neurotrauma and Critical Care Program, Scientific Poster 1333)
Other Studies In addition to the research cited above, physicians at several other prominent medical institutions throughout the country have studied the Digital Holography System, including Massachusetts General Hospital-Harvard Medical School (Boston); George Washington University Medical Center (Washington, D.C.); Irvine Medical Center-University of California at Irvine; and Mallinckrodt Institute of Radiology-Washington University (St. Louis).
The Digital Holography System was awarded FDA clearance in September 1995. In January 1997, Voxel was awarded a U.S. patent covering 13 claims, including five independent claims for the company's method of making multiple-exposure holograms. An existing reimbursement code for reporting medical procedures was amended effective January 1, 1998, to explicitly reference holographic imaging of CT and MR data. This provides a method by which clinicians may more accurately report, and seek reimbursement for, use of Digital Holography. Based in Laguna Hills, California, Voxel is a public company founded to develop, manufacture and market volumetric display systems based on multiple-exposure holography.
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Voxel and Voxgram are registered trademarks and Digital Holography is a trademark of Voxel.
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