Novel magnetic technology for intraoperative intracranial frameless navigation: in vivo and in vitro results.

OBJECTIVE: To characterize the accuracy of the Magellan electromagnetic navigation system (Biosense Webster, Tirat HaCarmel, Israel) and to demonstrate the feasibility of its use in image-guided neurosurgical applications. DESCRIPTION OF INSTRUMENTATION: The Magellan system was developed to provide real-time tracking of the distal tips of flexible catheters, steerable endoscopes, and other surgical instruments, using ultra-low electromagnetic fields and a novel miniature position sensor for image-correlated intraoperative navigation and mapping applications. METHODS: An image registration procedure was performed, and static and qualitative accuracies were assessed in a series of phantom, animal, and human neurosurgical studies. EXPERIENCE AND RESULTS: During the human study phase, an accuracy error of up to 5 mm was deemed acceptable. Results demonstrated that this degree of accuracy was maintained throughout all procedures. All anatomic landmarks were reached with precision and were accurately viewed on the display screen. Navigation that relied on the system was also successful. No interference with operating room equipment was noted. The accuracy of the system was maintained during regular surgical procedures, using standard surgical tools. CONCLUSION: The system provides precise lesion localization without limiting the line of vision, the mobility of the surgeon, or the flexibility of instruments. Electromagnetic navigation promises new advances in neuronavigation and frameless stereotactic surgery.

Experimental streptococcal meningo-encephalitis in cultured fish.

In 1984 a disease of fish appeared in Israel which spread rapidly in cultured fishponds. The disease affected tilapia (Oreochromis aura x Oreochromis nilotica hybrids) and trout (Oncorhynchus mykiss). Common carp (Cyprinus carpus), although reared in community with tilapia were not susceptible to the disease. Various species of ornamental cyprinids and cichlids were also affected. Morbidity was high and mortality ranged between 50% (in trout) and 30% (in tilapia). Clinical and pathological findings indicated that the tilapia and trout suffered from meningitis and menigo-encephalitis. Two new streptococcal species, Streptococcus shiloi and Streptococcus difficile were isolated from diseased fish. The disease was reproduced experimentally in both trout and tilapia with the two streptococcal species. The LD50s of S. shiloi and S. difficile strains cultured in vitro (two to three passages on BHI medium) were 10(7)-10(8) cfu. The virulence of these strains was increased (LD50:10(2)-10(5) cfu) after three passages in vivo (brain to brain passage in fish without culture on agar plates). Highly virulent strains did not differ from low virulent strains by any identifiable extrachromosomal elements.

Vaccination with whole-cell vaccine and bacterial protein extract protects tilapia against Streptococcus difficile meningoencephalitis.

Formalin-killed Streptococcus difficile strains used as vaccines delivered intraperitoneally were able to protect tilapia against a challenge of 100 LD50. The protection obtained was not strain specific. A vaccine based on an S. difficile extract containing 50% protein conjugated to alum also protected tilapia challenged with a virulent S. difficile strain. Protection in tilapia was correlated with the development of specific agglutinins. Western blot analysis supported the hypothesis that only a few proteins act as protective antigens in both the whole-cell vaccine and the streptococcal extract. The high efficacy of these vaccines make them good candidates for the control of streptococcal fish meningoencephalitis.