If available, some graphic aids can be helpful to show image orientations.
1) A graphic icon of the labeled primary axes (A, L, H) with relative lengths given by direction sines and orientation as if viewed from the normal to the image plane can help orient the viewer, both to identify image plane orientation and to indicate possible in plane rotation.
2) Ingraphic prescription of obliques from other images, a sample original image with an overlaid line or set of lines indicating the intersection of the original and
oblique image planes can help orient the viewer.
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The basic anatomical directions are:
right(R) to left (L), posterior (P) to anterior (A), and feet (F) to head (H).
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A standard display orientation for images in the basic
slice orientation is:
1) transverse: A to top of image and L to right,
2) coronal: H to top of image and L to right and
3) sagittal: H to top of image and A to left.
The location in the R/L and P/A directions can be specified relative to the axis of the
magnet.
The F/H location can be specified relative to a convenient patient structure.
The orientation of single
oblique slices can be specified by rotating a
slice in one of the basic orientations toward one of the other two basic
orthogonal planes about an axis defined by the intersection of the 2 planes.
Double
oblique slices can be specified as the result of tipping a single
oblique plane toward the remaining basic orientation plane, about an axis defined by the intersection of the
oblique plane and the remaining basic plane. In double
oblique angulations, the first rotation is chosen about the vertical image axis and the
second about the (new) horizontal axis.
Angles are chosen to have magnitudes less than 90° (for single
oblique slices less than 45°); the sign of the angle is taken to be positive when the rotation brings positive axes closer together.
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