Radiofrequency ablation planning beyond simulation

It is a challenging task to plan a radiofrequency (RF) ablation therapy to achieve the best outcome of the treatment and avoid recurrences at the same time. A patient specific simulation in advance that takes the cooling effect of blood vessels into account is a helpful tool for radiologists, but this needs a very high accuracy and thus high computational costs. In this work, we present various methods, which improve and extend the planning of an RF ablation procedure. First, we discuss two extensions of the simulation model to obtain a higher accuracy, including the vaporization of the water in the tissue and identifying the model parameters and to analyze their uncertainty. Furthermore, we discuss an extension of the planning procedure namely the optimization of the probe placement, which optimizes the overlap of the tumor area with the estimated coagulation in order to avoid recurrences. Since the optimization is constrained by the model, we have to take into account the uncertainties in the model parameters for the optimization as well. Finally, applications of our methods to a real RF ablation case are presented

Tunable cylindrical micro lenses based on aluminum nitride membranes

We introduce sputtered aluminum nitride thin films for tunable micro-optics. During lens fabrication, AlN is deposited on a silicon substrate. Silicon is structured by using DRIE, which allows fabrication of circular, rectangular and irregular membrane shapes. In this contribution, we present the design, fabrication and characterization of AlN membranes for tunable cylindrical lenses. An optimized "dogbone" membrane is presented, which deflects cylindrically and has a small footprint. Compared to conventional rectangular membranes the optically useful area is doubled. The load deflection characteristic is investigated and basic relations between the refractive power and applied pressure are found. The relation can be used for tailoring the membrane properties, i.e. their residual stress, for a specific application. According to this calculation, a refractive power of 25 dpt with a lens aperture of 3x3 mm(2) is achieved for 12 kPa of applied pressure. The cylindrical deflection of the "dogbone" membrane is measured. The maximum shape difference in measured to be 270 nm

Evaluation of the Global MOZART-2 Chemistry-Transport Model Using MOZAIC Data

(2-9 juin 2004)

Lokale und regionale Ozonproduktion: Chemie und Transport

Das durch den Bundesminister für Forschung und Technologie geförderte Vorhaben ist ein Beitrag zu dem EUROTRAC Subprojekt "Tropospheric Ozone Research" (TOR). Der Förderungszeitraum erstreckte sich vom 1. 1.1989 bis zum 31. 12. 1991. Die Bundeszuwendung machte etwa ein Drittel der gesamten Aufwendungen in dem Vorhaben aus, der Rest wurde aus KFA Mitteln bestritten. Folgende wichtige Arbeiten wurden in dem Vorhaben durchgeführt: • Koordinierung von TOR • Entwicklung und Technologietransfer von Meßgeräten (NO$_{x}$, J$_{NO_2}$, H$_{2}$O$_{2}$) • Hilfestellung bei der Durchführung und Qualitätskontrolle von Stickoxidmessungen in TOR $\bullet$ Aufbau der Meßstation Schauinsland und Durchführung kontinuierlicher Messungen von: - O$_{3}$, H$_{2}$O$_{2}$, organischen Peroxiden (Photooxidantien) - NO, NO$_{2}$, NO$_{y}$, C$_{2}$-C$_{5}$-Kohlenwasserstoffen, CO (O$_{3}$-Vorläufer) - Organischen Nitraten (Indikatoren für Radikalchemie) - Meteorologischen Daten - Photolysefrequenz von NO$_{2}$ $\bullet$ Durchführung von Meßkampagnen zur Untersuchung der Radikalchemie - Messungen der RO$_{2}$-Radikale zur Bestimmung der Ozonproduktionsrate - Messung von NO$_{3}$- und RO$_{2}$-Radikalen bei Nacht zur Aufklärung der Nachtchemie Die Entwicklung von Konzepten zur Bewertung der Ozonbilanz, insbesondere bzgl. der katalytischen Effizienz der Stickoxide bei der Ozonerzeugung, erfordert eine möglichst genaue Differenzierung von Luftmassen nach Herkunft, Belastung mit Spurenstoffen und Alter. Es ist also eine Klassifizierung der Messungen sowohl nach meteorologischen als auch nach luftchemischen Gesichtspunkten notwendig. Auf Grund der besonderen geographischen Lage der TOR-Station Schauinsland unmittelbar am Rand des Oberrheingrabens wird die Meßstation durch unterschiedliche Luftmassen beeinflußt. [...

Inorganic trace gases and peroxy radicals during BERLIOZ at Pabstthum : an investigation of the Photo Stationary State (PPS) of NOx and O3

[1] Meteorological and chemical measurements, including peroxy radicals, made during the Berlin Ozone Experiment (BERLIOZ) in summer 1998 at Pabstthum, a rural site about 50 km NW of the city, are described. The analytical techniques and data quality are discussed, including the comparison of different methods deployed side by side at Pabstthum. The highest concentrations of NOx (>20 ppb) and other precursors were observed on days when relatively young air was advected to Pabstthum from the greater Berlin area. NOx often increased during the night due to emissions from the surrounding soils under stagnant conditions with a shallow boundary layer as is evident in the strong negative correlation between nocturnal NO mixing ratios and product of ozone and wind speed. The ozone production rate (PO3) calculated from the photostationary state (PSS) of NOx and O-3 increased with NO and reached values of up to 90 ppb h(-1). PO3 calculated from NO and the measured peroxy radical concentrations was much lower, around or below 10 ppb h(-1). The lower production rates obtained from the peroxy radical measurements are consistent with the ozone budget in the city plume of Berlin. The new JPL recommendation for the rate coefficient of the reaction of NO with O-3 slightly improves the disagreement between PSS and measured peroxy radicals. However, another enhancement of 10-20% in the rate coefficient would be required in order to match the results within the uncertainty of the measurements in the high NOx regime. Even then, PSS remains to overpredict PO3 by a factor of 2 at low NOx concentrations. Hence, a yet unidentified process must exist in the atmosphere that converts NO to NO2 without leading to a net production of ozone. The PSS results from other studies are similar as at Pabstthum, suggesting that the overestimation of peroxy radicals and PO3 by the PSS approach is not a particular feature of the conditions at the site