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K Petermann

Publications and source records attributed to K Petermann.

5 recordsLinked to original sources

Multicenter German reference data base for peripheral quantitative computer tomography.

The wide spread use of bone densitometers in Germany and other European countries has required the establishment of a validated reference population data base. A semianthropomorphic forearm cross-calibration phantom (EFP), developed during a concerted research action of the European Union's programme in Biomedical Engineering (COMAC-BME), was used to cross-calibrate the peripheral quantitative computer tomography (pQCT) devices at four German centers participating in the multicenter study. In total, 723 women and 208 men were included in the normal data base. No significant regional differences were found between the data of the different centers. In addition to the manufacturers calibration standard, proper calibration of the pQCT devices could be monitored during collection of the normal female and male data base. As a merit of the COMAC-BME study the measurements obtained with all pQCT devices thus ensured an uniform reference data base for distal radius measurements in Germany.

Adult

Noninvasive prediction of SAR distributions with an electro-optical E field sensor.

An integrated electro-optical (eo) E field sensor is developed on the basis of a Ti:LiNbO3 Mach-Zehnder interferometer. A measuring device based on the lock-in principle is introduced to register the E field in phase and amplitude using this E field probe. Segmented electrodes are used to minimize influences from the dielectric surroundings on the base point capacitance of the receiving dipole. The operating point is stabilized against drift phenomena resulting from optical damage and pyroelectric effect. Sensitivity, dynamic range, harmonic distortions and mechanical properties of a prototype of this electro-optical E field sensor are evaluated. A phantom setup in the SIGMA-60 applicator was developed to test this electro-optical sensor for hyperthermia applications. Power deposition patterns of various standard adjustments of the SIGMA ring are visualized in an elliptical lamp phantom. Simultaneously, E field in phase and amplitude is determined on a closed curve in 10 degrees steps around the phantom in a substitute bolus. The numbers are stored and utilized as boundary conditions in a two-dimensional finite elements code which calculates the SAR distribution on an appropriate triangular grid inside the closed curve. An excellent qualitative agreement is obtained between visualized and calculated SAR patterns. This novel measurement method is therefore suitable for noninvasive monitoring of SAR patterns during clinical application of regional radiofrequency hyperthermia.

Electrodes