Direction of X, Y and Z axis in DICOM patient coordinates

Development
1

Hi All,

I am developing DICOM Viewer with help of VTK/ITK and for one 3D model I need from DICOM data (dcm files) to get Direction of X, Y and Z-axis in DICOM patient coordinates.
For this purpose I believe I will need help of follow DICOM Tags:

  • 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 respectto 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.

To calculate:

  • Direction of X-axis in DICOM patient coordinates
  • Direction of Y-axis in DICOM patient coordinates
  • Direction of Z-axis in DICOM patient coordinates

I will give 2 examples how should looks DICOM input values and result output values (Direction of X, Y and Z-axis in DICOM patient coordinates):

Example 1:
Input values:
Image Position (0020,0032) = -90.587402322119, -109.07805985037, -54.313941027148
Image Orientation (0020,0037) = 0.99980097943443, -0.0052184900275, 0.01925535987173, 5.1979E-11, 0.96518213254221, 0.26157876638076

Output values:
Direction of X-axis in DICOM patient coordinates: 0.999800979434429, -0.00521849002749999, 0.01925535987173
Direction of Y-axis in DICOM patient coordinates: 5.19383355768177e-11, 0.965182132542206, 0.261578766380758
Direction of Z-axis in DICOM patient coordinates: -0.0199499754876277, -0.261526706825732, 0.964990041448579

Example 2:
Input values:
Image Position (0020,0032) = -88.948269885356, 31.931496794475, 81.739738901004
Image Orientation (0020,0037) = 0.79547348593335, 0.60598839359928, -4.0729377E-9, -0.234829907807, 0.30825831580772, -0.9218631813533

Output values:
Direction of X-axis in DICOM patient coordinates: 0.795473485933353, 0.605988393599283, -4.07293770000002e-09
Direction of Y-axis in DICOM patient coordinates: -0.234829907806982, 0.308258315807713, -0.921863181353261
Direction of Z-axis in DICOM patient coordinates: -0.5586383871310699, 0.733317719381138, 0.387515515644527

So my question what is connection between values of input and output in my examples, how is calculate output (directions of X, Y, Z axis) from input values (Image Position (0020,0032) and Image Orientation (0020,0037))

Thanks in advance,
Tim

2

Hi Tim -

You might find the information on this page helpful:

Note that there can be a lot of special cases mapping image acquisition slices to 3D space, due to things like gantry tilt, irregular spacing, time series acquisitions, etc. If you are planning to give your software to other people and those people expect to be able to load “any” dicom data you are signing up for a lot of maintenance headaches. If you need to handle cases like this robustly you may consider building on 3D Slicer or MITK, which provide higher level abstractions that have already been heavily tested and debugged.

1 Like
3

@pieper

I solved, actually all that need to be done is to used vtkMath::Cross(directionXAxis, directionYAxis, resultZCross);
as last vector is need to be calculate as cross product from others two.

But thanks for help