Digitally reconstructed X-ray image
Digitally reconstructed X-ray images (abbr .: DRR) are made as part of modern radiation therapy . They are similar to normal x-rays, but they come from the image data of a computer tomography . A virtual view of the three-dimensional data set z. B. of the chest, the voxels are given a density-dependent transparency. The result is a summation image of all structures in the viewing direction. The most common purpose is to display a radiation field from the point of view of the radiation source. B. can be compared with the simulator image.
generation
An image with the same geometric perspective of the radiation from the radiation device is generated from the CT data set . The image is created by a voxel summation along the divergent beam spreading from the focus to the image plane . Eight neighboring voxels are averaged at each node ( trilinear interpolation ).
advantage
- Radiographs of non-coplanar fields are possible.
disadvantage
- lower spatial resolution (1 line pair per mm) compared to the film (2 line pairs per mm)
- Creation of motion artifacts
Different display options
- Creation of contrast between soft tissue and bone
- Creation of contrast between soft tissue and lungs
- MIP ( maximum intensity projection )
- equal weighting of all density values
literature
- E. Richter, T. Feyerabend: Fundamentals of radiation therapy . Springer-Verlag, ISBN 3-540-58230-4