Abstract: A method and system to determine brain stiffness is disclosed. A probe to measure tissue water content is inserted through an aperture (burr hole) in the cranium into brain tissue. The probe has two electrically separated plate conductors with a dielectric which forms a capacitor plane. One conductor has a surface mount resistor to allow exact impedance matching to the core of a coaxial cable. The other conductor attaches electrically to the shield of the coaxial cable. The probe is stabilized in the brain tissue through a plastic ventriculostomy bolt which has been secured by screw tapping into the cranium. The coaxial cable connects to a spectrum analyzer. Brain water content and blood congestion alter the resonant frequency of the probe, allowing a realtime readout of apparent tissue water content.

Abstract: A guidance system for guiding a surgical instrument without visual information to a target in tissue. The system centers the target upon the trajectory of an infinite family of zero-flux curvilinear lines emanating from either a fixed magnet or an ac or dc electromagnet which is mounted on the instrument. The approach to the target allows selection of straight and curved trajectories based on the zero-flux lines that intersect the target. A self-centering attachment that holds the magnet allows any straight instrument to be guided by the system. The zero-flux lines are measured by a magnetometer that is located on a remote location on or in the tissue. The transducers of the magnetometer measure the magnetic field strength that is present if the instrument deviates from the zero-flux line. The guidance information is plotted on a display that allows a user to guide the instrument along the zero-flux line to the target.

Abstract: A method and a surgical guidance system (20) direct an instrument to a target (40) located inside a patient (22). The surgical guidance system (20) includes a fixation frame (28), a first arc member (36), a second arc member (38), and first (78) and second (84) electromagnetic (EM) radiative sources. The first arc member (36) and the second arc member (38) are adjustably coupled to rotate about a common axis (48) and are adjusted in response to a target address and at least three marker addresses so that the target (40) is located at the center point of a virtual sphere defined by the arc members. A first electromagnetic (EM) radiative beam (80) and a second electromagnetic (EM) radiative beam (86) are projected from the system (20) and intersect at a line. The line forms a trajectory (146) along which an instrument can be directed to the target (40).

Abstract: A surgical guidance system includes a magnetic field generator carried by a support frame, a guidance system controller, at least one magnetic field sensor located at a surgical instrument, and a feedback display device. The guidance system indicates the position of the surgical instrument relative to a trajectory as the surgical instrument approaches a surgical target within a body. The magnetic field generator establishes a magnetic field having geometric characteristics that indicate the trajectory from an initial point to the target. The sensors detect the distinguishable orientation of the magnetic field along the trajectory, and the feedback display device indicates whether the surgical instrument is aligned or misaligned with the trajectory. The magnetic field generator is adjustable upon the support frame such that the approach angle and position of the trajectory may be selected.

Abstract: A system (10) presents a graphic guidance object (46) in a display screen (40) to aid a surgeon in guiding a probe (12) from an initial point (82) relative to a body (14) along a desired trajectory (54) to a target (52). The graphic object (46) may be presented simultaneously with a live video image (44) from an endoscope and with tomogram images (42). The graphic object (46) includes a probe tip indicator (88) and a trajectory indicator (94). These indicators (88, 94) are positioned relative to one another to graphically indicate how far and in which direction to move a probe tip (36) to cause the probe tip (36) to intersect the desired trajectory (54). A roll orientation feature (118) and a distance-to-target feature (126) are included in the graphic object (46). The graphic object (46) changes in real time to track movement of the probe (12).

Abstract: An apparatus for non-invasively stabilizing the head of a patient is provided. The apparatus includes a support frame, a rigid template mounted to the support frame, a plurality of fiducial marker housings located on the support frame, and a mounting assembly that attaches the support frame to a table or a bed. The rigid template is formed by molding a heat-activated sheet of plastic around the head or face of the patient. A method for treating the head of a patient is also provided. The method involves forming a rigid template that conforms to the head and/or face of a patient, positioning the head with the rigid template, performing a radiographic imaging procedure, and performing a subsequent surgical procedure. The imaging and surgical procedures are performed with the patient stabilized in the same position.