tools.NavigatorMotionTracker

class bartorch.tools.NavigatorMotionTracker

Bases:

Six-degree-of-freedom rigid pose from a navigator’s 2D planes, filtered over time.

Each plane is registered in 2D against the same plane of the first navigator. A plane measures the rotation about its normal and the translation along its two in-plane axes; these are linear in the rotation vector and translation of the 3D pose, which are solved for by least squares over the planes and passed to a RigidMotionEKF. The planes’ normals must span the three rotations and their in-plane axes the three translations; three orthogonal planes are the usual set. The in-plane model holds while the out-of-plane motion is small enough that each plane still intersects the anatomy of its reference.

Parameters:

• registration (RigidRegistration, default=None) – Registration of each plane; a RigidRegistration with its defaults otherwise.

• process_noise (float or sequence of float, default=0.0001) – Passed to RigidMotionEKF.

• measurement_noise (float or sequence of float, default=0.01) – Passed to RigidMotionEKF.

• initial_covariance (float, default=1.0) – Passed to RigidMotionEKF.

filter

The filter carrying the pose.

Type:

RigidMotionEKF

reference

Planes of the first navigator; None before the first track().

Type:

list or None

property registration

Registration each plane is measured with.

property pose

Current filtered pose, about the navigator’s centre.

reset()

Discard the reference navigator and the filtered pose.

track()

Register one navigator against the reference and return the filtered pose.

Parameters:

• planes (sequence of torch.Tensor or numpy.ndarray) – One 2D image per plane, in the same order at every call.

• axes (sequence) – Per plane, (row_axis, column_axis): unit 3-vectors, in the frame the pose is wanted in, along which the image’s first and second array axes run. The two must be perpendicular.

• dt (float, default=1.0) – Time since the previous navigator.

• spacing (float or sequence of float, default=1.0) – In-plane pixel size, one value or one per plane. Translations are returned in its unit.

Returns:

The filtered 3D pose relative to the reference navigator, about the origin of the axes frame; zero for the first navigator.

Return type:

RigidMotionEstimate

Raises:

ValueError – If the number of planes differs from the reference, the axes are not a perpendicular pair per plane, or the planes leave a rotation or translation component unmeasured.

Examples using NavigatorMotionTracker

Rigid head motion from navigators

Rigid head motion from navigators