Program: gdcm
Module: $RCSfile: gdcmOrientation.cxx,v $
Language: C++
- Date: $Date: 2005/09/20 15:11:19 $
- Version: $Revision: 1.10 $
+ Date: $Date: 2005/09/21 16:39:53 $
+ Version: $Revision: 1.11 $
Copyright (c) CREATIS (Centre de Recherche et d'Applications en Traitement de
l'Image). All rights reserved. See Doc/License.txt or
return vec3;
}
-} // end namespace gdcm
-
-
// ---------------------------------------------------------------------------
return dic
*/
+
+
+// ------------------------------------------------------------------------
+/*
+2.2.2 Orientation of DICOM images
+
+
+http://www.dclunie.com/medical-image-faq/html/part2.html#DICOMOrientation
+says :
+
+A question that is frequently asked in comp.protocols.dicom is how to determine
+ which side of an image is which (e.g. left, right) and so on.
+ The short answer is that for projection radiographs this is specified
+ explicitly using the Patient Orientation attribute, and for cross-sectional
+ images it needs to be derived from the Image Orientation (Patient) direction
+ cosines. In the standard these are explained as follows:
+
+ * "C.7.6.1.1.1 Patient Orientation.
+ The Patient Orientation (0020,0020) relative to the image
+ plane shall be specified by two values that designate the
+ anatomical direction of the positive row axis (left to right)
+ and the positive column axis (top to bottom).
+ The first entry is the direction of the rows, given by the
+ direction of the last pixel in the first row from the first
+ pixel in that row.
+ The second entry is the direction of the columns, given by
+ the direction of the last pixel in the first column from the
+ first pixel in that column.
+ Anatomical direction shall be designated by the capital
+ letters: A (anterior), P (posterior), R (right),L (left),
+ H (head), F (foot).
+ Each value of the orientation attribute shall contain at
+ least one of these characters.
+ If refinements in the orientation descriptions are to be
+ specified, then they shall be designated by one or two
+ additional letters in each value.
+ Within each value, the letters shall be ordered with the
+ principal orientation designated in the first character."
+
+ * "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 provided 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 sid 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."
+
+Some simple code to take one of the direction cosines (vectors) from the
+Image Orientation (Patient) attribute and generate strings equivalent to one
+of the values of Patient Orientation looks like this (noting that if the vector
+is not aligned exactly with one of the major axes, the resulting string will
+have multiple letters in as described under "refinements" in C.7.6.1.1.1):
+
+*/
+
+/**
+ * \brief computes the Patient Orientation relative to the image plane
+ * from the 'Image Orientation (Patient)'
+ * The first entry is the direction of the rows, given by the
+ * direction of the last pixel in the first row from the first
+ * pixel in that row.
+ * The second entry is the direction of the columns, given by
+ * the direction of the last pixel in the first column from the
+ * first pixel in that column.
+ * Anatomical direction is designated by the capital
+ * letters: A (anterior), P (posterior), R (right),L (left),
+ * H (head), F (foot).
+ * Refinements in the orientation descriptions are designated
+ * by one or two additional letters in each value.
+ * @return orientation string as "rawOrientation\columnsOrientation"
+ */
+std::string Orientation::GetOrientation ( File *f )
+{
+ float iop[6];
+ if ( !f->GetImageOrientationPatient( iop ) )
+ return GDCM_UNFOUND;
+
+ std::string orientation;
+ orientation = GetSingleOrientation ( iop )
+ + "\\"
+ + GetSingleOrientation ( iop + 3 );
+ return orientation;
+}
+
+
+std::string Orientation::GetSingleOrientation ( float *iop)
+{
+ std::string orientation;
+
+ char orientationX = iop[0] < 0 ? 'R' : 'L';
+ char orientationY = iop[1] < 0 ? 'A' : 'P';
+ char orientationZ = iop[2] < 0 ? 'F' : 'H';
+
+ double absX = iop[0];
+ if (absX < 0) absX = -absX;
+ double absY = iop[1];
+ if (absY < 0) absY = -absY;
+ double absZ = iop[2];
+ if (absZ < 0) absZ = -absZ;
+
+ for (int i=0; i<3; ++i)
+ {
+ if (absX>.0001 && absX>absY && absX>absZ)
+ {
+ orientation = orientation + orientationX;
+ absX=0;
+ }
+ else if (absY>.0001 && absY>absX && absY>absZ)
+ {
+ orientation = orientation + orientationY;
+ absY=0;
+ }
+ else if (absZ>.0001 && absZ>absX && absZ>absY)
+ {
+ orientation = orientation + orientationZ;
+ absZ=0;
+ }
+ else
+ break;
+ }
+ return orientation;
+}
+
+
+
+} // end namespace gdcm
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