Comparison of active-set method deconvolution and matched-filtering for derivation of an ultrasound transit time spectrum.

The quality of ultrasound computed tomography imaging is primarily determined by the accuracy of ultrasound transit time measurement. A major problem in analysis is the overlap of signals making it difficult to detect the correct transit time. The current standard is to apply a matched-filtering approach to the input and output signals. This study compares the matched-filtering technique with active set deconvolution to derive a transit time spectrum from a coded excitation chirp signal and the measured output signal. The ultrasound wave travels in a direct and a reflected path to the receiver, resulting in an overlap in the recorded output signal. The matched-filtering and deconvolution techniques were applied to determine the transit times associated with the two signal paths. Both techniques were able to detect the two different transit times; while matched-filtering has a better accuracy (0.13 µs versus 0.18 µs standard deviations), deconvolution has a 3.5 times improved side-lobe to main-lobe ratio. A higher side-lobe suppression is important to further improve image fidelity. These results suggest that a future combination of both techniques would provide improved signal detection and hence improved image fidelity.

Automatic multimodal 2D/3D breast image registration using biomechanical FEM models and intensity-based optimization.

Due to their different physical origin, X-ray mammography and Magnetic Resonance Imaging (MRI) provide complementary diagnostic information. However, the correlation of their images is challenging due to differences in dimensionality, patient positioning and compression state of the breast. Our automated registration takes over part of the correlation task. The registration method is based on a biomechanical finite element model, which is used to simulate mammographic compression. The deformed MRI volume can be compared directly with the corresponding mammogram. The registration accuracy is determined by a number of patient-specific parameters. We optimize these parameters--e.g. breast rotation--using image similarity measures. The method was evaluated on 79 datasets from clinical routine. The mean target registration error was 13.2mm in a fully automated setting. On basis of our results, we conclude that a completely automated registration of volume images with 2D mammograms is feasible. The registration accuracy is within the clinically relevant range and thus beneficial for multimodal diagnosis.

Detection and imaging of atmospheric radio flashes from cosmic ray air showers.

The nature of ultrahigh-energy cosmic rays (UHECRs) at energies >10(20) eV remains a mystery. They are likely to be of extragalactic origin, but should be absorbed within approximately 50 Mpc through interactions with the cosmic microwave background. As there are no sufficiently powerful accelerators within this distance from the Galaxy, explanations for UHECRs range from unusual astrophysical sources to exotic string physics. Also unclear is whether UHECRs consist of protons, heavy nuclei, neutrinos or gamma-rays. To resolve these questions, larger detectors with higher duty cycles and which combine multiple detection techniques are needed. Radio emission from UHECRs, on the other hand, is unaffected by attenuation, has a high duty cycle, gives calorimetric measurements and provides high directional accuracy. Here we report the detection of radio flashes from cosmic-ray air showers using low-cost digital radio receivers. We show that the radiation can be understood in terms of the geosynchrotron effect. Our results show that it should be possible to determine the nature and composition of UHECRs with combined radio and particle detectors, and to detect the ultrahigh-energy neutrinos expected from flavour mixing.

Improved limits on nu(e) emission from mu+ decay.

We investigated mu(+) decays at rest produced at the ISIS beam stop target. Lepton flavor (LF) conservation has been tested by searching for nu(e) via the detection reaction p(nu(e),e(+))n. No nu(e) signal from LF violating mu(+) decays was identified. We extract upper limits of the branching ratio (BR) for the LF violating decay mu(+)-->e(+)+nu(e)+nu(-) compared to the standard model (SM) mu(+)-->e(+)+nu(e)+nu(mu) decay: BR<0.9(1.7) x 10(-3) (90% C.L.) depending on the spectral distribution of nu(e) characterized by the Michel parameter rho=0.75(0.0). These results improve earlier limits by one order of magnitude and restrict extensions of the SM in which nu(e) emission from mu(+) decay is allowed with considerable strength. The decay mu(+)-->e(+)+nu(e)+nu(mu) often proposed as a potential source for the nu(e) signal observed in the LSND experiment can be excluded.

Automatic image matching for breast cancer diagnostics by a 3D deformation model of the mamma.

X-ray mammograms and MR volumes provide complementary information for early breast cancer diagnosis. The breast is deformed during mammography, therefore the images can not be compared directly. A registration algorithm is investigated to fuse the images automatically. A finite element simulation was applied to a MR image of an underformed breast and compared to a compressed breast using different tissue models and boundary conditions. Based on the results a set of patient data was registered. To archive the requested accuracy distinguishing between the different tissue types of the breast was not necessary. A linear elastic model was sufficient. It was possible to simulate the deformation with an average deviation of approximately of the size of a voxel in the MRI data and retrieve the position of a lesion with an error of 3.8 mm in the patient data.

[Severe factor XIII-deficiency. Studies on subunits and turnover of the fibrin stabilizing factor (author's transl)]. / Ein neuer Fall von schwerem Faktor XIII-Mangel. Untersuchungen zum Verhalten der Untereinheiten und des Turnover des Fibrinstabilisierenden Faktors.

An infant with congenital homozygous factor XIII deficiency demonstrated a severe retroperitoneal and intracerebral bleeding with development of a posthemorrhagic hydrocephalus in the first months of life. Factor XIII activity was not measurable by means of enzymatic method and the antiserum inhibition test. Quantitative immunoelectrophoresis according to Laurell presented absence of the subunit A, whereas the concentration of subunit S was reduced to 47% the normal value. After replacement therapy factor XIII activity was estimated at 23% and corresponded to the concentration of the subunit A, concentration of subunit S increased by 20%. The turnover rate of fibrin stabilizing factor could be observed over a period of 39 days. The half life was estimated at 4,7 days. The child developed normally after continous substitution with 250 units of factor XIII concentrate every 6 weeks.