Johann Otto

Measurements of the optical properties of breast tissue using time-resolved transillumination

Time-resolved in vivo measurements have been performed to determine the optical properties of the female breast. The optical parameters at 800 nm are of special interest for medical diagnosis since this wavelength is close to the isosbestic point of oxy- and deoxyhemoglobin. The measurements have been performed with a Ti:sapphire laser using a synchroscan-streak camera. The diffusion model has been used to calculate the absorption coefficient (mu) A and the reduced scattering coefficient (mu) s equals (mu) s (1 - g). Measurements at different positions on the mamma showed systematic changes of the time-resolved signals which can be explained by the composition of this heterogenous tissue. A good agreement between the measurements on the right and left mamma has been found. Additionally, time- resolved experiments on breast tissue in vitro at 532 nm, 800 nm, and 1064 nm have been performed to study the optical properties at these wavelengths.

Chip verification of 4 Mbit DRAMs by e-beam testing

Abstract Due to their high level of integration, dynamic random access memories (DRAMs) place vigorous requirements on the tools needed for internal signal analysis. In this regard, electron-beam testing proves an invaluable analysis tool for design and process optimization. The e-beam tester described here enables testing of a 4 Mbit DRAM, as well as of the future generation which will utilize submicron interconnections. Major development effort has been carried out with respect to the electron optics to fulfill the required e-beam tester performance. Other important verification criteria include the associated test hardware and degree of CAD integration, as well as improved circuit layout for e-beam testability at chip level. Typical 4 Mbit DRAM verification procedures will be outlined: basic logic verification, graphical comparison of simulated and measured signals by CAD integration and precision waveform measurements being the main topics. Finally, future demands will be discussed.

Spectral transillumination of human breast tissue

By transilluminating human tissue in vivo in the visible and near-IR regions, specific information can be obtained in utilizing both the scattering and the absorbing properties of light. Different compositions of fatty, fibrous, glandular, and muscular tissues are associated with different optical parameters (reduced scattering and absorption coefficients). To characterize human breast tissue in vivo, measurements were carried out in a clinical environment. Thus the tissues, which showed a variety of pathalogical alteration, where measured in patients with different age, different breast size, in varying locations in the breast. The results indicate that other characteristics beyond the pure detection of the amount of blood in the neovascular network, in particular the volume concentrations of water and fat, seem to be important for the discrimination. In order to quantify this observation, an analytical model was developed that takes the volume percentages of fat and water, the concentration and oxygenation of hemoglobin, and the relevant optical coefficients into account. The in vivo spectra could be fitted in all cases. Typical results will be discussed and preliminary statistical correlations presented.

On-chip reliability investigations on power modules actually working in inverter systems

The paper contains the results of temperature measurements for reliability investigations on IGBT modules actually working in inverters for industrial and traction applications. For this, the chip temperature and its transient behaviour have been monitored under different driving conditions of the inverters. Specially prepared IGBT-modules have been used to investigate the industrial and the traction inverters in their electrical and thermal behaviour. The measurement techniques were suitably adapted to the different configurations of the two inverters.

Spectral transillumination of female breasts and breast tissue-like material

Several types of tissue-like materials, animal tissues and human breast tissues in vitro, have been measured by a photospectrometer at visible and near-infrared wavelengths (between approximately 500 and 1100 nm) with the aim of correlating the dominant spectral features. In the clinical part of this work female volunteers of different age with various thicknesses of breast tissue at different sites were transilluminated spectroscopically in vivo in this diagnostic window. In addition, phantom experiments have been conducted to answer the question of how sensitively absorbing objects hidden inside a turbid medium several centimeters thick may be identified from their spectral signature. On the basis of these results it may be possible to improve the detectability of breast lesions, for example tumors, by a spectral transillumination technique.

Time-resolved transillumination of turbid media

The suitability and limits of time-resolved transillumination to determine inner details of biological tissues are investigated by phantom experiments. The achievable improvement is demonstrated by using different phantoms (absorbing objects embedded in a turbid medium). By means of line-scans across a sharp edge the spatial resolution and its dependence on temporal resolution can be determined. To demonstrate the physical resolution according to the Rayleigh-criterion, measurements were performed on blackened bead pairs. Investigations with partially transparent beads demonstrate the high sensitivity of time-resolving techniques with respect to variations in scattering or absorption coefficients.

Zeitaufgelöste Transillumination von trüben Medien

Die nichtinvasive Diagnostik von Gewebserkrankungen mit Licht ist von grosem Interesse fur die Untersuchung von Organen, fur Vorsorge- bzw. Verlaufskontrollen [1,2]. Wegen der enormen Vielfachstreuung des Lichtes im Gewebe ist dabei die raumliche Auflosung beschrankt. Es ist jedoch moglich, durch eine Laufzeitbeschrankung vielfach gestreute Photonen, welche eine schlechte Ortsauflosung bewirken, von weniger gestreuten Photonen mit einer besseren Ortsauflosung abzutrennen. Deshalb lassen sich durch den Einsatz zeitauflosender Verfahren generell mehr Strukturdetails erkennen als mit Dauerlichtverfahren. Um quantitativ abzuklaren, welchen Nutzen ein zeitaufgelostes Durchstrahlungsverfahren bietet, wurden systematische Messungen an unterschiedlichen Phantomen (trube Medien mit eingelagerten Storobjekten) durchgefuhrt. Die reduzierte Streulange l’ s = l s/ (1- g) ist auser von der Gewebeart abhangig von der verwendeten optischen Wellenlange; typische Werte liegen zwischen l’ s =0.4 mm... 8 mm. Die im Gewebe stattfindende Absorption (Absorptionslange l A) liegt in einem Wertebereich zwischen l A =100... 1000 mm. Experimente an truben Medien mit diesen optischen Weglangen decken alle denkbaren Anwendungen ab.

Schaltungsüberprüfung eines 4 Mb DRAM mit einem Submikron-Elektronenstrahl-Meßgerät

ÜbersichtDie Elektronenoptik der Niederspannungssäule eines Submikron-Elektronenstrahl-Meßgerätes (Sub-μm-EMG) wird beschrieben. Der Durchmesser des Elektronenstrahls erreicht für eine Strahlspannung von 1 kV und einen Probenstrom von 2,5 nA einen Wert von nur 0,12 μm. Das bei internen Signalverlaufsmessungen auftretende Übersprechen durch benachbarte Leitbahnen (‘crosstalk’-Fehler) konnte für 1,1 μm breite Bahnen auf etwa 3% begrenzt werden. Für den Nachweis des Lesesignals eines 4 Mb DRAM (‘Dynamic random access memory’, d. h. dynamischer Speicher mit wahlfreiem Zugriff) ist die Spannungsauflösung des Meßsystems ausreichend. Damit kann das Sub-μm-EMG zur internen Schaltungsüberprüfung des 4 Mb DRAM eingesetzt werden, wie an ausgewählten Beispielen illustriert wird. Die insgesamt ermittelten Leistungsdaten werden aber auch der zukünftigen Speichergeneration — dem 16 Mb DRAM — gerecht. Einige noch notwendige Verbesserungen für eine insgesamt erfolgreiche Schaltungsanalyse an Sub-μm-Schaltkreisen werden kurz diskutiert.ContentsThe electron-optical low-voltage column of the submicron electron-beam tester will be described. An electron probe diameter of 0.12 μm at a probe current of 2.5 nA as well as a beam voltage of 1 kV has been realized. It is shown that in the case of waveform measurements on 1.1 μm interconnection lines, the crosstalk error is only approximately 3%. The voltage resolution is sufficient to allow the sense signal of a 4 Mb DRAM (dynamic random access memory) to be verified. Typical examples demonstrate the benefits and flexibility of the contactless e-beam probing due to the allover verification requirements of the 4 Mb DRAM. Besides this the measured performance data enable the circuit analysis of the next DRAM-generation, the 16 Mb DRAM. The improvements still necessary for such future applications are briefly discussed.