Otto Sauer

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PURPOSE To evaluate a novel four-dimensional (4D) image-guided radiotherapy (IGRT) technique in stereotactic body RT for liver tumors. METHODS AND MATERIALS For 11 patients with 13 intrahepatic tumors, a respiratory-correlated 4D computed tomography (CT) scan was acquired at treatment planning. The target was defined using CT series reconstructed at(More)
The aim of this work was to evaluate the accuracy of dose predicted in heterogeneous media by a pencil beam (PB), a collapsed cone (CC) and a Monte Carlo (MC) algorithm. For this purpose, a simple multi-layer phantom composed of Styrofoam and white polystyrene was irradiated with 10 x 10 cm2 as well as 20 x 20 cm2 open 6 MV photon fields. The beam axis was(More)
PURPOSE . The influence of two different calculation algorithms ("pencil beam" [PB] versus "collapsed cone" [CC]) on dose distribution, as well as the dose-volume histograms (DVHs) of the planning target volume (PTV) and the organs at risk was analyzed for irradiation of lung cancer. MATERIAL AND METHODS . Between 10/2001 and 02/2002 three-dimensional(More)
PURPOSE To evaluate the precision of image-guided radiotherapy (IGRT) using cone-beam computed tomography (CB-CT) for volume imaging and a robotic couch for correcting setup errors in six degrees of freedom. PATIENTS AND METHODS 47 consecutive patients with 372 fractions were classified according to whether a patient fixation device was used (pat(fix): n(More)
A variety of detectors and procedures for the measurement of small field output factors are discussed in the current literature. Different detectors with or without corrections are recommended. Correction factors are often derived by Monte Carlo methods, where the bias due to approximations in the model is difficult to judge. Over that, results appear to be(More)
PURPOSE To scrutinize the positioning accuracy and reproducibility of a commercial hexapod robot treatment table (HRTT) in combination with a commercial cone-beam computed tomography system for image-guided radiotherapy (IGRT). METHODS AND MATERIALS The mechanical stability of the X-ray volume imaging (XVI) system was tested in terms of reproducibility(More)
In the vicinity of interfaces between materials of different atomic number Z, extremes in absorbed dose occur for high-energy photon irradiations. The spatial extension of the effects is within the range of 1 cm, which may not be ignorable from the radiobiological point of view. At the front side of a high-Z slab a maximum is observed, whereas at the exit(More)
Essential for the calculation of photon fluence distributions for intensity modulated radiotherapy (IMRT) is the use of a suitable objective function. The objective function should reflect the clinical aims of tumor control and low side effect probability. Individual radiobiological parameters for patient organs are not yet available with sufficient(More)
PURPOSE To evaluate whether the position of brain metastases remains stable between planning and treatment in cranial stereotactic radiotherapy (SRT). METHODS AND MATERIALS Eighteen patients with 20 brain metastases were treated with single-fraction (17 lesions) or hypofractionated (3 lesions) image-guided SRT. Median time interval between planning and(More)
Convolution/superposition software has been used to produce a library of photon pencil beam dose matrices. This library of pencil beams is designed to serve as a tool for both education and investigation in the field of radiotherapy optimization. The elegance of this pencil beam model stems from its cylindrical symmetry. Because of the symmetry, the dose(More)