Tracking a cylindrical opening
Inventors
Mikuszeit, Nikolai • Schilling, Christian • Zerres, Olaf • Brunner, Georg • Kirsch, Stefan R. • Ashe, Westley D. • Schneider, Mark Robert • Kogan, Vladimir F.
Assignees
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Publication Number
US-10779892-B2
Publication Date
2020-09-22
Expiration Date
Abstract
A system comprising: a sensor configured to be introduced into a clearance hole of a surgical implant, wherein the sensor is configured to be introduced in proximity to a generated magnetic field and cause distortion of the magnetic field; and one or more field measuring coils configured to: measure a characteristic of the magnetic field when the sensor is in proximity to the magnetic field; and provide, to a computing device, a signal representative of the measured characteristic of the magnetic field, wherein the computing device is configured to determine one or both of a position and an orientation of the sensor and the clearance hole based on the measured characteristic of the magnetic field.
Core Innovation
The invention provides an electromagnetic tracking system for tracking a clearance hole of a surgical implant by introducing a sensor into the clearance hole. The sensor is configured to be introduced in proximity to a generated magnetic field and to cause distortion of the magnetic field. One or more field measuring coils measure a characteristic of the magnetic field when the sensor is in proximity to the magnetic field and provide a signal representative of the measured characteristic to a computing device, which determines a position and an orientation of the sensor and the clearance hole based on the measured characteristic.
The sensor is implemented with a three-dimensional orthogonal geometry in which each orthogonal dimension has a different length. This geometry supports tracking based on distortion of the generated magnetic field, and it emphasizes using cylindrical symmetry to discount roll and enable a five degree of freedom sensor. The system includes sensor geometries such as an ellipsoid sensor geometry.
The system further emphasizes a wireless sensor formed with a shell and ferrofluid having magnetic properties, including superparamagnetic iron oxide nanoparticles such as magnetite and maghemite. The document also describes ferrofluid and shell handling, including removal by piercing and magnetic pulling, and alternative retention using biocompatible and biodegradable shell material. The document relates the tracking to surgical implant use cases such as intramedullary nail clearance-hole targeting and fastener insertion without excessive imaging, using the determined position and orientation.
Claims Coverage
The document provides two independent claims: one system claim and one method claim. Across these claims, the core inventive features are a clearance-hole electromagnetic tracking sensor that distorts a generated magnetic field, one or more coils that measure a magnetic-field characteristic, and a computing device that determines the sensor and clearance-hole position and orientation from that measured characteristic.
Clearance-hole sensor distorting a generated magnetic field with 3D orthogonal unequal dimensions
A sensor configured to be introduced into a clearance hole of a surgical implant, the sensor having a three-dimensional orthogonal geometry with each orthogonal dimension having a different length, wherein the sensor is configured to be introduced in proximity to a generated magnetic field and cause distortion of the magnetic field.
Field measuring coils providing a characteristic signal for computing
One or more field measuring coils configured to measure a characteristic of the magnetic field when the sensor is in proximity to the magnetic field and provide, to a computing device, a signal representative of the measured characteristic.
Computing device determining position and orientation from the measured characteristic
The computing device configured to determine a position and an orientation of the sensor and the clearance hole based on the measured characteristic of the magnetic field.
Receiving coil signal and determining pose in the method
A method that introduces the sensor into a clearance hole of a surgical implant so the sensor is introduced in proximity to a generated magnetic field and causes distortion, receives by a computing device from one or more field measuring coils a signal representative of a characteristic of the magnetic field measured when the sensor is in proximity, and determines by the computing device a position and an orientation of the sensor and the clearance hole based on the measured characteristic.
Claim coverage centers on electromagnetic tracking of a surgical implant clearance hole by inserting a sensor with a three-dimensional orthogonal geometry having unequal orthogonal dimensions so the sensor distorts a generated magnetic field. One or more field measuring coils measure a magnetic-field characteristic and provide a representative signal to a computing device, which determines position and orientation of both the sensor and the clearance hole from the measured characteristic.
Stated Advantages
Improves tracking accuracy by emphasizing cylindrical symmetry to discount roll.
Enables a 5DoF sensor and simplifies hardware/processing.
Documented Applications
Tracking a cylindrical clearance hole in a surgical implant such as an intramedullary nail for clearance-hole targeting.
Supporting fastener insertion and external access using the determined position and orientation of the clearance hole and sensor without excessive imaging.
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