Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

4 Publications
Optimum Voxel Size for Reconstruction of In Beam PET Data
Shakirin, G.; Crespo, P.; Fiedler, F.; Wagner, A.; Enghardt, W.;
At the heavy ion therapy facility at the Gesellschaft für Schwerionenforschung Darmstadt, Germany, an in-beam PET scanner is operated for quality assurance monitoring simultaneously to the therapeutic irradiation. The PET scanner, which is completely integrated into the treatment facility, registers the annihilation γ - rays following the decay of minor amounts of β+ radioactive nuclei produced via nuclear reactions between the ions of the therapeutic beam and the atomic nuclei of the irradiated tissue. From a comparison of the reconstructed activity distributions with those predicted from the treatment plan, deviations between the prescribed and the applied dose distributions can be detected. The solution currently implemented for the reconstruction of in-beam PET data is the ML-EM algorithm adapted to the low statistics case and to the dual head geometry. The size of image elements (voxels) influences significantly the quality of the image. A small voxel size increases the resolution but produces high oscillations of a signal. Large voxels produce homogeneous images, however, with low spatial resolution. The size of the voxel is always a compromise between suppressing signal oscillations which requires larger voxel size, and covering small imaging details which requires smaller voxel size. The standard voxel side-length used for the BASTEI scanner, 1.6875 mm, is exactly 1/4 of the crystal width. For in-beam PET the size of the voxel can be enlarged for typical irradiation fields from the standard (1.6875 mm)3 to 2 × 2 × 3 mm3 without loss of quality. The images reconstructed with bigger voxel are less noisy and still contain enough information about activity in small cavities and deviations of the range. Reconstruction performs almost two times faster for the 2 × 2 × 3 mm3 voxel.
Keywords: in-beam PET, reconstruction, voxel size, radiotherapy, ML-EM, OS-EM, RFS-EM
  • Poster
    IEEE Dresden 2008, 19.-25.10.2008, Dresden, Germany
  • Contribution to proceedings
    IEEE Dresden 2008, 19.-25.10.2008, Dresden, Germany
  • Contribution to external collection
    in: GSI Scientific Report 2008, GSI: GSI, 2009
  • Poster
    OncoRay Retreat meeting, 14.-15.01.2009, Bautzen, Germany

Publ.-Id: 11898 - Permalink