[Dissection technique--is ultrasound the best method?]. / Dissektionstechnik--Ist der Ultraschall das beste Medium?

Preventive hemostasis is extremely important in endoscopic surgery. Ultrasonic dissectors are used very often. We tested the occlusion safety of bipolar forceps and ultrasonic dissector for porcine vessels. Thermographic videos showed maximum temperature up to 200 degrees C when using one ultrasonic dissector. The lateral damage zone in vivo and in vitro measured between 2 and 6 mm.

MR imaging in the presence of vascular stents: A systematic assessment of artifacts for various stent orientations, sequence types, and field strengths.

A systematic evaluation of the potential quality of magnetic resonance images recorded in the presence of metallic stents was performed on a low-field open imager operating at 0.2 T and on a high-field closed unit operating at 1.0 T. Eight different stent types were examined by two-dimensional gradient-echo sequences with echo times of 4 and 10 msec and by a fast spin-echo technique. In addition, a three-dimensional gradient-echo sequence was applied with an echo time of 2.4 msec. A set of sequence and slice parameters was used on both scanners. Thus, artifacts due to susceptibility effects depending on the magnetic field strength could be distinguished from radiofrequency shielding effects in the lumen of the stents (independent of the field strength). Nine different orthogonal orientations of the stent axis and the image (in terms of slice, read, and phase-encoding direction) were tested, and the artifacts (extension of signal void and visibility of the lumen) were compared. The optimal strategy for visualization of vascular and perivascular regions outside the stents was fast spin-echo imaging with the stent axis and read direction parallel to the static field. Susceptibility-induced signal void in gradient-echo images was minimal using the three-dimensional approach. Increased transmitter amplitudes above usual values provided clearly improved insight in the lumen using gradient-echo sequences.

Experimental Studies and Theoretical Predictions for the H + D2 rarr > HD + D Reaction.

The H + H(2) exchange reaction constitutes an excellent benchmark with which to test dynamical theories against experiments. The H + D(2) (vibrational quantum number v = 0, rotational quantum number j = 0) reaction has been studied in crossed molecular beams at a collision energy of 1.28 electron volts, with the use of the technique of Rydberg atom time-of-flight spectroscopy. The experimental resolution achieved permits the determination of fully rovibrational state-resolved differential cross sections. The high-resolution data allow a detailed assessment of the applicability and quality of quasi-classical trajectory (QCT) and quantum mechanical (QM) calculations. The experimental results are in excellent agreement with the QM results and in slightly worse agreement with the QCT results. This theoretical reproduction of the experimental data was achieved without explicit consideration of geometric phase effects.