Fully three-dimensional sound speed-corrected multi-wavelength photoacoustic breast tomography

Photoacoustic tomography is a contrast agent-free imaging technique capable of visualizing blood vessels and tumor-associated vascularization in breast tissue. While sophisticated breast imaging systems have been recently developed, there is yet much to be gained in imaging depth, image quality and tissue characterization capability before clinical translation is possible. In response, we have developed a hybrid photoacoustic and ultrasound-transmission tomographic system PAM3. The photoacoustic component has for the first time three-dimensional multi-wavelength imaging capability, and implements substantial technical advancements in critical hardware and software sub-systems. The ultrasound component enables for the first time, a three-dimensional sound speed map of the breast to be incorporated in photoacoustic reconstruction to correct for inhomogeneities, enabling accurate target recovery. The results demonstrate the deepest photoacoustic breast imaging to date namely 48 mm, with a more uniform field of view than hitherto, and an isotropic spatial resolution that rivals that of Magnetic Resonance Imaging. The in vivo performance achieved, and the diagnostic value of interrogating angiogenesis-driven optical contrast as well as tumor mass sound speed contrast, gives confidence in the system's clinical potential.Comment: 33 pages Main Body, 9 pages Supplementary Materia

Umkehr effect in Hall voltage of polycrystalline bismuth

The Hall effect has been measured on an isotropic polycrystalline Bi sample, from 5 K up to room temperature. It appears that the Hall voltage exhibits a strong asymmetry under sign reversal of magnetic field. This peculiar effect becomes more pronounced as the temperature decreases. It is shown that this astonishing behavior, at first glance, can be ascribed to the "Umkehr" effect, previously predicted from a phenomenological point of view, for the off-diagonal components of the magnetoresistivity tensor, for (3) over barm crystallographic point group

Performance Analysis of the Dual Cell Spacer in ATM Systems

In this paper we develop an analysis of the so-called Dual Cell Spacer. In contrast to a conventional spacer, which shapes a traffic stream only according to a given Peak Cell Rate, the Dual Cell Spacer takes into account the Peak Cell Rate as well as the Sustainable Cell Rate with the corresponding Burst Tolerance. The analysis is carried out in the discrete-time domain. Performance measures such as the cell rejection probability, the cell delay distribution and the cell inter-departure time distribution are derived. All results are of an exact nature. Numerical examples that compare the performance of the Dual Cell Spacer with that of a conventional spacer show a similar performance in terms of cell delay and cell loss for relatively small values of the Burst Tolerance. Using our analysis, both the Sustainable Cell Rate and the Burst Tolerance, which are used for traffic shaping in the Dual Cell Spacer, can be chosen adequately to achieve a given target cell rejection probability or ..