Biomedical subjects

W Daum

Publications and source records attributed to W Daum.

14 recordsLinked to original sources

PubMed2003

Second-harmonic generation in GaAs: experiment versus theoretical predictions of chi(2)xyz.

For GaAs we have determined |chi((2))(xyz)(-2omega;omega,omega)| in second-harmonic generation experiments using two-photon energies between 2 and 5 eV. In addition to the E1, E1+delta(1), E'0, and E2 critical-point bulk transitions of GaAs, a surprisingly strong surface transition at 3.35 eV was observed for natively oxidized GaAs(001) samples. A detailed comparison with theoretical predictions reveals that calculations that include many-particle effects at the level of the "scissors" approximation can describe the overall frequency dependence of the second-harmonic susceptibility reasonably well.

Journal Article↗

PubMed1999

[MR-track pointer. A reusable device for localization during interventions].

PURPOSE: Development of an helpful instrument for a better planning and orientation during MR guided interventions. MATERIAL AND METHODS: We developed a reusable, sterilizable instrument that can be filled both with a solution of Gd-DTPA (1%) and with a sodium chloride solution (0.9%). The pointer has a diameter of 3 and 5 mm resp. and its length is 100-150 mm. The instrument can be combined with an interactive stereotactic tracking device. RESULTS: The MR-Track-Pointer can be fixed to the two handpieces of the integrated interactive tracking system without problems. The pointer can be seen both on T1w and T2w sequences inside and outside of the tissue. This new instrument can be interactively used for reliable planning the biopsy trajectory, planning craniotomies and identifying structures which are only visible on MR images. CONCLUSIONS: The MR-Track-Pointer is an ideal supplement for the integrated virtual tracking system. It permits a minimal invasive orientation and facilitates the exact localisation of suspect lesions in sensible regions during MR guided interventions, e.g. diagnostic biopsies and tumour resections.

Biopsy↗

PubMed1993