OrientationXMedConPatientBased

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2. Patient Based

As told for the equipment based coordinate system, the patient based coordinate system is simply a variation on the three slice orientations which are supported by (X)MedCon. We learned from the DICOM 3.0 standard that the axes are as follows:

 X-axis: Right    (hand)  ->  Left      (hand)
 Y-axis: Anterior (front) ->  Posterior (back)
 Z-axis: Inferior (feet)  ->  Superior  (head)

As we also learned from the equipment based coordinate system, the row and column unit vectors of a slice (image) are defined with the direction cosines. In the patient based coordinate system an extra tag is used to define the direction in the patient of both vectors. The DICOM syntax is:

direction of row vector \ direction of column vector

The abbreviations used in this DICOM tag tell where the unit vector is pointing to:

 L = towards Left 	R = towards Right
 A = towards Anterior 	P = towards Posterior
 F = towards Feet 	H = towards Head

(X)MedCon supports the following four orthogonal patient orientations:

Fig.1a: supine head first

Fig.2a: prone head first

Fig.: Front view of imaging device
with equipment based coordinate system

Fig.1b: supine feet first

Fig.2b: prone feet first

Note: Here you see that in case of a patient lying supine head first, the coordinate system coincide with the equipment based system.

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