How to reslice a DICOM volume ?

DICOM volume reslicing are available for any 3D Dataset. Two options are available : static and oblique reslicing. This function is also active with registred volumes. Be aware that each additional layer increases the computation time.

Static reslicing

Static reslicing is available when using a Talairach coordinate system. Geometric transformations used in static reslicing are composed of rigid rotations along X, Y, Z defined by the user.

The user have to choose four points which define two axes : a line which goes from the anterior commissure (AC) to the posterior commissure (PC) line and a vertical line along Z which defines the inclinaison of the volume. Two points are mandatory : a “vertical up” point (VU) and a “vertical bottom” point (VB). The center of rotation is located at the center of the volume.

The chosen points are stored in a table (AC, PC, VU, VB). The coordinates of the points are stored in two coordinates system:

1. The native coordinate system used during the acquisition of the DICOM images (X Coord, Y Coord, Z Coord, see table below).
2. A coordinate system centered on the DICOM volume (sometimes used in stereotaxic procedure using Leksell frame, X AC-PC, Y AC-PC, Z AC-PC) :

• The origin of the coordinate system is defined by the middle of the AC-PC line,
• X is positive toward the right side,
• Y is positive toward the front side,
• Z is positive toward the top of the volume.

        This coordinate system is converted from the native coordinate system using AC/PC/VB and VU points. Be aware, that the values are imprecise due to multiple rounded operations. Only the native values are accurate.

To set CA, navigate in the volume and place the navigations lines on AC, then press AC button. The current position will be stored as CA coordinates. Repeat the same procedure for PC, VB and VU points. Then press . The volume will automatically be resliced according to the AC-PC line.

Oblique reslicing

Oblique reslicing is useful to improve the understanding of a volume of interest (VOI) inside a 3D dataset.

When the user navigate inside the DICOM volume, a sustained right mouse click will initialise a rigid rotation according to the angle defined by the course of the mouse from its initial position to its final course. The center of the rotation is the last location of the user inside the volume.

The angle should lay between -90° and 90°. The mouse goes automatically to the right end of the vertical line, to facilitate the rotational movement.

• The user can navigate in the volume as previously described (see “How to navigate in a DICOM volume”). A left mouse click on any view (sagittal, coronal or axial) will display three orthogonal slices of the volume at mouse point coordinate.
• To go back to the initial position of the volume, uncheck .
• The angle defined in the last rotation is stored. When the user checks , the volume will be resliced according to the parameters in memory.
• The angle of rotation in memory is reset when the user press the  button.

Back to “Table of contents”