.. _UserDefinedSweepforSimulation:

User Defined Sweep for Simulation
=================================

For both the :ref:`HybridUltrasoundSimulation` and the :ref:`UltrasoundSimulation` algorithms, the user can define a sweep for the simulated ultrasound images, if the algorithm is not invoked with an existing sweep. The sweep is then defined by two splines, the Transducer Spline and the Direction Spline. The Transducer Spline defines the motion of the simulated ultrasound probe tip center, and the Direction Spline defines the direction of the simulated ultrasound probe. The simulated images will originate on equally spaced points along the Transducer Spline and will be directed towards equally spaced points on the Direction Spline.

- **Number of Frames**: The number of frames in the ultrasound sweep.
- **Depth**: The depth of the ultrasound sweep.
- **Probe Width**: The width of the ultrasound probe.
- **Frame Geometry**: The geometry of the ultrasound frames. Can be either Linear or Convex.
- **Angle**: The imaging opening angle for convex frame geometries.
- **Slice Reference**: The reference spline for the alignment of the frames in the sweep. Can be either "Center" or "Direction". The images will be orthogonal or parallel (depending on the parameter "Slices Perpendicular") to the center spline or the direction spline respectively.
- **Slice Perpendicular**: The alignment of the frames in the sweep, relative to the splines. If active, the frames will be perpendicular to the reference spline, otherwise they will be parallel to it.
- **Transducer Spline**: The spline that defines the motion of the simulated ultrasound probe tip center. After clicking this button, it can be created in the MPR views by placing one or more points with a left click and adding the final spline point with a right click. The order of the points is important, as the first point will be the starting point of the simulated motion.
- **Direction Spline**: The spline that defines the direction of the simulated ultrasound probe. After clicking this button, it can be created in the MPR views similar to the Transducer Spline. The order of the points is important, as the first point will define the direction of the first frame.

Exemplary User Defined Sweeps
-----------------------------

The following images show three exemplary user defined sweeps. The first one is a linear sweep in elevation direction, as one might perform along an extremety. It contains 4 frames and was created with **Slice Perpendicular** active. The Transducer Spline (shown in green) and the Direction Spline (shown in blue) are parallel to each other.

.. figure:: img/synthetic_ultrasound_sweep_straight.png
   :align: center

   Straight sweep
   
The second sweep images a target from different planes. It contains 5 frames and was created with **Slice Perpendicular** active. Note how the Transducer Spline (shown in green) is longer than the Direction Spline (shown in blue).

.. figure:: img/synthetic_ultrasound_sweep_curved.png
   :align: center
   
   Curved sweep
   
The third sweep shows a sweep with only lateral motion, as if keeping a target in the image plane but moving the probe sideways. It contains 5 frames and was created with **Slice Perpendicular** inactive, thus the frames are tangential to the Transducer Spline (shown in green).

.. figure:: img/synthetic_ultrasound_sweep_tangential.png
   :align: center

   Sweep with lateral motion

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