Ralph Alexander Bundschuh, Presenter: Nothing to Disclose

Julia Dinges MD, Abstract Co-Author: Nothing to Disclose

Nikolaus Andratschke, Abstract Co-Author: Nothing to Disclose

Sabrina T. Astner, Abstract Co-Author: Nothing to Disclose

Axel Martínez-Möller, Abstract Co-Author: Nothing to Disclose

Markus Schwaiger MD, Abstract Co-Author: Research grant, Siemens AG Research grant, Bayer AG Research grant, Lantheus Medical Imaging, Inc Speaker, General Electric Company Speaker, Siemens AG

Sibylle Ziegler, Abstract Co-Author: Research grant, Siemens AG Shareholder, SurgicEye GmbH

Markus Essler MD, Abstract Co-Author: Nothing to Disclose

Stereotactic radiotherapy is a highly effective method for treatment of liver metastasis in inoperable patients. Although MRI and CT are standard imaging modalities for therapy planning, it is frequently difficult to define an exact target volume based on these methods especially if previous surgical treatment was performed. PET as functional imaging modality may help to improve the accuracy of target volume delineation. In the liver, respiratory movement can be a severe problem, and should be taken into account for the image acquisition and therapy planning.

16 patients scheduled for stereotactic treatment of liver metastasis were examined by 4D FDG-PET/CT additional to conventional imaging with CT and MR. In PET/CT immobilization was carried out by a vacuum couch and a low-pressure foil. Data were fused on a BrainLab workstation and the quality of the fusion was rated on a scale from 1 (excellent) to 5 (poor) for fusion of MR with respiratory gated and not gated PET. Target volumes were defined using conventional morphological imaging (Vcon) and PET, in PET manual delineation was done (Vman) as well as semiautomatic segmentation after validation in a phantom study (Vauto).

In two patients the suspicious lesion did not show FDG uptake and hence radiation treatment was canceled. Another 2 patients showed extra hepatic metastasis not found before and hence stereotactic treatment was not applied. In the remaining 12 patients 14 lesion were identified. The image fusion was rated with a mean of 3.4 when the not-gated PET was used while it improved to a mean of 2.0 when respiratory gated PET was used. The mean Vcon was 40 ccm while the mean Vman and Vauto were 34 and 29 ccm respectively.

FDG-PET can influences the treatment planning by identifying patients which do not profit from stereotactic treatment. For therapy planning we found that PET changes the target volume significantly. However respiratory gated PET is necessary to achieve better quality for image fusion. Movement of the liver may even more be corrected using combined PET/MR machines.

FDG-PET can help in the decision which patients do profit from stereotactic radiotherapy, in these patients it can help to improve the target volume delineation.

Bundschuh, R, Dinges, J, Andratschke, N, Astner, S, Martínez-Möller, A, Schwaiger, M, Ziegler, S, Essler, M, 4D FDG-PET/C Does Significantly Influence the Stereotactic Radiation Therapy Planning of Liver Metastasis.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9010442.html