Stephan F. Simon

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The paper reports on investigations concerning the application of block oriented fractal coding schemes for encoding of color images. Correlations between the different color planes can be exploited for the aim of data compression. For this purpose the similarities between the fractal transform parameters of one block location but different color planes are(More)
OBJECT The aim of this study was to analyze the cellular immune response and histopathological changes in secondary brain tumors after gamma knife surgery (GKS). METHODS Two hundred ten patients with cerebral metastases underwent GKS. Seven patients underwent subsequent craniotomy for tumor removal between 1 and 33 months after GKS. Four of these patients(More)
The purpose of this study was to assess the use of positron emission tomography (PET) as a stereotactic planning modality for gamma knife radiosurgery (GKS). The authors developed and validated a technique for fiducial marker imaging, importation, and handling of PET data for integration into GammaPlan planning software. The clinical feasibility in applying(More)
Voronoi cells for vector quantization subject to an entropy constraint are considered. It is shown that the constraint on the output entropy leads to a weaker and even vanishing dependency of the Voronoi cell's volume on the probability density function. Using some simplifying assumptions like linearization of a small part of the r-dimensional input space(More)
Objectives. The aim of this prospective phase II study is to evaluate the treatment of early-stage breast cancer (T1 N0) with intraoperative electron radiation therapy (IOERT) in terms of local control, early complications, and cosmesis. Patients and Methods. From February 2010 to February 2012, 200 patients underwent partial IOERT of the breast. Inclusion(More)