Convert Direction Cosines to Anatomical Direction

For cross-sectional DICOM images the orientation must be derived from the Image Orientation (Patient) direction cosines.

getOrientation(xyz, delta = 0.0001)

Arguments

xyz	is a vector of direction cosines from “ImageOrientationPatient” (0020,0037).
delta	is the tolerance around zero for comparisons.

Value

Anatomical direction shall be designated by the capital letters:

posterior

right

left

head

foot

Details

C.7.6.2.1.1 Image Position And Image Orientation. The Image Position (0020,0032) specifies the x, y, and z coordinates of the upper left hand corner of the image; it is the center of the first voxel transmitted. Image Orientation (0020,0037) specifies the direction cosines of the first row and the first column with respect to the patient. These Attributes shall be provide as a pair. Row value for the x, y, and z axes respectively followed by the Column value for the x, y, and z axes respectively. The direction of the axes is defined fully by the patient's orientation. The x-axis is increasing to the left hand side of the patient. The y-axis is increasing to the posterior side of the patient. The z-axis is increasing toward the head of the patient. The patient based coordinate system is a right handed system; i.e., the vector cross product of a unit vector along the positive x-axis and a unit vector along the positive y-axis is equal to a unit vector along the positive z-axis.

References

http://www.dclunie.com/medical-image-faq/html/part2.html

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