Plus applications user manual  2.9.0.bf99f0e
Software library for tracked ultrasound image acquisition, calibration, and processing.


Typically tracking and imaging devices require spatial and temporal calibration after they are set up.

Calibration using fCal

Spatial calibration algorithms determine unknown transformations that remain constant after the system is set up. Typically these are transformations between the coordinate systems of an object (e.g., image slice, calibration phantom, stylus) and a tracking marker that is rigidly attached to that object.

  • Pivot calibration algorithm is used for computing the transformation between the tip(StylusTip) of a pointer tool (a.k.a. stylus) and the marker that is attached to the tool (Stylus).
  • Phantom registration algorithm determines the transformation between the calibration phantom's coordinate system (Phantom) and the attached marker's coordinate system (Reference). The method uses landmark registration: transformation between an object and the attached marker is computed by touching predefined positions on the object with a tracked stylus.
  • Probe calibration algorithm is used for determining the transformation between the coordinate system of the image (Image) and the marker that is attached to the US transducer (Probe).

Temporal calibration determines time offset between data streams acquired by different devices. Temporal calibration is essential if data is acquired while tracked tools are moving, because then any temporal misalignment results in spatial errors.

Freehand tracked ultrasound calibration application (fCal) implements all the above described calibration algorithms in a single application.

Calibration using SlicerIGT modules

SlicerIGT extension of 3D Slicer contains a number of spatial calibration modules that allow computing transforms and using them in Plus.