EM Tracker Coil Characterization - Revision history

Traneus: Added detail

2017-01-18T19:06:01Z

Added detail

Traneus: Added detail

2017-01-18T19:04:04Z

Added detail

Traneus at 18:22, 18 January 2017

2017-01-18T18:22:28Z

Traneus: Improved some language.

2017-01-11T17:31:31Z

Improved some language.

Traneus: Further discussion added

2017-01-09T21:21:49Z

Further discussion added

Traneus at 21:17, 9 January 2017

2017-01-09T21:17:23Z

Traneus at 21:14, 9 January 2017

2017-01-09T21:14:46Z

Traneus at 21:08, 9 January 2017

2017-01-09T21:08:51Z

Traneus at 21:04, 9 January 2017

2017-01-09T21:04:47Z

Traneus: Coil Characterization is EM problem, not mechanical problem

2017-01-09T21:01:52Z

Coil Characterization is EM problem, not mechanical problem

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EM Tracker Coil Characterization
When we test a tracker for accuracy, we generally check using point sets that make mechanical sense. For example, we may use a 3D robot to move the receiver all over the working volume (also called the motion box).

← Older revision		Revision as of 19:06, 18 January 2017
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	The scribble data-collection method involves mounting the receiver on a small flat slider, and slowly sliding the receiver around (and rotating the receiver) on a known-flat surface (such as a granite surface plate). We know that the points mechanically are all on a plane (though we do not know exactly what plane), and that the receiver orientations must all be the same within rotations about the axis perpendicular to the plane.		The scribble data-collection method involves mounting the receiver on a small flat slider, and slowly sliding the receiver around (and rotating the receiver) on a known-flat surface (such as a granite surface plate). We know that the points mechanically are all on a plane (though we do not know exactly what plane), and that the receiver orientations must all be the same within rotations about the axis perpendicular to the plane.

−	For coil characterization, the transmitter is mounted under the center of the known-flat surface.	+	For coil characterization, the transmitter is mounted under the center of the known-flat surface, as close as the minimum range (minimum transmitter to receiver distance) of the tracker permits.

← Older revision		Revision as of 19:04, 18 January 2017
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	The scribble data-collection method involves mounting the receiver on a small flat slider, and slowly sliding the receiver around (and rotating the receiver) on a known-flat surface (such as a granite surface plate). We know that the points mechanically are all on a plane (though we do not know exactly what plane), and that the receiver orientations must all be the same within rotations about the axis perpendicular to the plane.		The scribble data-collection method involves mounting the receiver on a small flat slider, and slowly sliding the receiver around (and rotating the receiver) on a known-flat surface (such as a granite surface plate). We know that the points mechanically are all on a plane (though we do not know exactly what plane), and that the receiver orientations must all be the same within rotations about the axis perpendicular to the plane.
		+
		+	For coil characterization, the transmitter is mounted under the center of the known-flat surface.

@@ Line 9: / Line 9: @@
 One important property of electromagnetics, is the boundary-condition property: If we know the magnetic field everywhere on the boundary of the working volume, we can calculate the field inside the working volume.
-For coil characterization, the boundary-condition property suggests characterizing coils using only the the plane of the working volume closest to the transmitter. This could be done with a 2D robot or with a 3D robot. If a 3D robot is used, we can then use the remainder of the 3D robot points to check mechanical accuracy.
+For coil characterization, the boundary-condition property suggests characterizing coils using only the the plane of the working volume closest to the transmitter. Farther-away data points provide no characterization-dependence not already in the closest points, so farther-away points can confuse characterization fitters.
-Pete believes (though has not verified) that the 2D robot can be replaced by the scribble-test data-collection method in this paper:
+Pete believes (though has not verified) that the scribble-test data-collection method in this paper would serve for coil characterization:
 * C.A. Nafis, V. Jensen, L. Beauregard, P.T. Anderson, "Method for estimating dynamic EM tracking accuracy of Surgical Navigation tools", SPIE Medical Imaging Proceedings, 2006. Reports low-cost accuracy-measuring techniques and results for various trackers.
 The scribble data-collection method involves mounting the receiver on a small flat slider, and slowly sliding the receiver around (and rotating the receiver) on a known-flat surface (such as a granite surface plate). We know that the points mechanically are all on a plane (though we do not know exactly what plane), and that the receiver orientations must all be the same within rotations about the axis perpendicular to the plane.

@@ Line 7: / Line 7: @@
 The coils can only be manufactured to so much precision. Characterization measures the actual properties of each coil, to improve the tracker accuracy.
-The important electromagnetic property, is the boundary-condition property: If we know the magnetic field everywhere on the boundary of the working volume, we can calculate the field inside the working volume.
+One important property of electromagnetics, is the boundary-condition property: If we know the magnetic field everywhere on the boundary of the working volume, we can calculate the field inside the working volume.
 For coil characterization, the boundary-condition property suggests characterizing coils using only the the plane of the working volume closest to the transmitter. This could be done with a 2D robot or with a 3D robot. If a 3D robot is used, we can then use the remainder of the 3D robot points to check mechanical accuracy.
@@ Line 15: / Line 15: @@
 * C.A. Nafis, V. Jensen, L. Beauregard, P.T. Anderson, "Method for estimating dynamic EM tracking accuracy of Surgical Navigation tools", SPIE Medical Imaging Proceedings, 2006. Reports low-cost accuracy-measuring techniques and results for various trackers.
-The scribble data-collection method involves mounting the receiver on a small flat slider, and slowly sliding the receiver around (and rotating the receiver) on a known-flat surface (such as a granite surface plate). We know that the points mechanically are all on a plane (though we do not know exactly what plane), and that the receiver orientations must all be the same, except for rotations about the axis perpendicular to the plane.
+The scribble data-collection method involves mounting the receiver on a small flat slider, and slowly sliding the receiver around (and rotating the receiver) on a known-flat surface (such as a granite surface plate). We know that the points mechanically are all on a plane (though we do not know exactly what plane), and that the receiver orientations must all be the same within rotations about the axis perpendicular to the plane.

← Older revision		Revision as of 21:21, 9 January 2017
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	Pete believes (though has not verified) that the 2D robot can be replaced by the scribble-test data-collection method in this paper:		Pete believes (though has not verified) that the 2D robot can be replaced by the scribble-test data-collection method in this paper:

−	C.A. Nafis, V. Jensen, L. Beauregard, P.T. Anderson, "Method for estimating dynamic EM tracking accuracy of Surgical Navigation tools", SPIE Medical Imaging Proceedings, 2006. Reports low-cost accuracy-measuring techniques and results for various trackers.	+	* C.A. Nafis, V. Jensen, L. Beauregard, P.T. Anderson, "Method for estimating dynamic EM tracking accuracy of Surgical Navigation tools", SPIE Medical Imaging Proceedings, 2006. Reports low-cost accuracy-measuring techniques and results for various trackers.
		+
		+	The scribble data-collection method involves mounting the receiver on a small flat slider, and slowly sliding the receiver around (and rotating the receiver) on a known-flat surface (such as a granite surface plate). We know that the points mechanically are all on a plane (though we do not know exactly what plane), and that the receiver orientations must all be the same, except for rotations about the axis perpendicular to the plane.

← Older revision		Revision as of 21:17, 9 January 2017
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	For coil characterization, the boundary-condition property suggests characterizing coils using only the the plane of the working volume closest to the transmitter. This could be done with a 2D robot or with a 3D robot. If a 3D robot is used, we can then use the remainder of the 3D robot points to check mechanical accuracy.		For coil characterization, the boundary-condition property suggests characterizing coils using only the the plane of the working volume closest to the transmitter. This could be done with a 2D robot or with a 3D robot. If a 3D robot is used, we can then use the remainder of the 3D robot points to check mechanical accuracy.
		+
		+	Pete believes (though has not verified) that the 2D robot can be replaced by the scribble-test data-collection method in this paper:
		+
		+	C.A. Nafis, V. Jensen, L. Beauregard, P.T. Anderson, "Method for estimating dynamic EM tracking accuracy of Surgical Navigation tools", SPIE Medical Imaging Proceedings, 2006. Reports low-cost accuracy-measuring techniques and results for various trackers.

← Older revision		Revision as of 21:14, 9 January 2017
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	In 6DOF trackers, the coils must be precisely characterized for their electromagnetic properties: gains, non-orthogonalities, non-concentricities, and finite-size effects. Since characterization is measuring electromagnetic properties, the point set chosen should make electromagnetic sense rather than mechanical sense.		In 6DOF trackers, the coils must be precisely characterized for their electromagnetic properties: gains, non-orthogonalities, non-concentricities, and finite-size effects. Since characterization is measuring electromagnetic properties, the point set chosen should make electromagnetic sense rather than mechanical sense.

−	The important electromagnetic property, is the boundary-condition property: If we know the magnetic field on the plane of the working volume closest to the transmitter, we can ~~calculate~~ the ~~field elsewhere in~~ the ~~working volume~~.	+	The coils can only be manufactured to so much precision. Characterization measures the actual properties of each coil, to improve the tracker accuracy.
		+
		+	The important electromagnetic property, is the boundary-condition property: If we know the magnetic field everywhere on the boundary of the working volume, we can calculate the field inside the working volume.
		+
		+	For coil characterization, the boundary-condition property suggests characterizing coils using only the the plane of the working volume closest to the transmitter. This could be done with a 2D robot or with a 3D robot. If a 3D robot is used, we can then use the remainder of the 3D robot points to check mechanical accuracy.

← Older revision		Revision as of 21:08, 9 January 2017
Line 4:		Line 4:

	In 6DOF trackers, the coils must be precisely characterized for their electromagnetic properties: gains, non-orthogonalities, non-concentricities, and finite-size effects. Since characterization is measuring electromagnetic properties, the point set chosen should make electromagnetic sense rather than mechanical sense.		In 6DOF trackers, the coils must be precisely characterized for their electromagnetic properties: gains, non-orthogonalities, non-concentricities, and finite-size effects. Since characterization is measuring electromagnetic properties, the point set chosen should make electromagnetic sense rather than mechanical sense.
		+
		+	The important electromagnetic property, is the boundary-condition property: If we know the magnetic field on the plane of the working volume closest to the transmitter, we can calculate the field elsewhere in the working volume.

← Older revision		Revision as of 21:04, 9 January 2017
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	EM Tracker Coil Characterization		EM Tracker Coil Characterization
		+
	When we test a tracker for accuracy, we generally check using point sets that make mechanical sense. For example, we may use a 3D robot to move the receiver all over the working volume (also called the motion box).		When we test a tracker for accuracy, we generally check using point sets that make mechanical sense. For example, we may use a 3D robot to move the receiver all over the working volume (also called the motion box).
		+
		+	In 6DOF trackers, the coils must be precisely characterized for their electromagnetic properties: gains, non-orthogonalities, non-concentricities, and finite-size effects. Since characterization is measuring electromagnetic properties, the point set chosen should make electromagnetic sense rather than mechanical sense.