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► Fully automated approach for a 2D/3D breast image registration. ► Two-step simulation of the mammographic compression by the finite element method. ► Patient-specific biomechanical ...model of the breast. ► FEM-based registration optimized by image similarity metric. ► Evaluation with 79 clinical datasets: clinically relevant registration accuracy.
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.
3D ultrasound computer tomography for medical imaging Gemmeke, H.; Ruiter, N.V.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2007, Letnik:
580, Številka:
2
Journal Article
Recenzirano
Our 3D ultrasound computer tomograph (USCT) is an device method aimed at early breast cancer diagnosis. It is capable of producing images with sub-millimeter resolution and high signal-to-noise ...ratio. This method is universally useable for the 3D analysis of sufficient small bodies similar to the size of a breast, which may be immersed in a liquid coupling medium. In this paper, an overview of the developed method and the first results for static test examples (phantoms) and the perspective of our 3D-USCT at Forschungszentrum Karlsruhe are presented.
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.
We present a new approach for automatic registration of X-ray mammograms and MR images. Multimodal breast cancer diagnosis is supported by automatic localization of small lesions, which are only ...visible in the mammograms or in the MR image. To cope with the huge deformation of the breast during mammography, a finite element model of the deformable behavior of the breast is applied during the registration. An evaluation of the registration with six clinical data sets resulted in an accurate localization with a mean displacement of 4.3 mm (/spl plusmn/1 mm) and 3.9 mm (/spl plusmn/1.7 mm) for predicting the lesion position in mammograms and in the MR images, respectively.
LOPES was a digital antenna array operating for approximately 10 years until spring 2013 at the Karlsruhe Institute of Technology (KIT). Triggered by the co-located KASCADE-Grande air-shower ...experiment, it measured the radio signal of around 1000 cosmic-ray air showers with energies E 1017 eV in an effective band of 43 - 74 MHz. Using the interferometric technique of cross-correlation beamforming, LOPES could reconstruct the shower direction with an accuracy < 0.7°, the shower energy with a precision < 20%, and the atmospheric depth of the shower maximum, Xmax, with a precision < 95g cm2. In particular the reconstruction of the shower maximum suffers from significant measurement uncertainties due to the radio-loud environment of the site. This article summarizes our latest results on the reconstruction of the shower maximum, using two independent methods: the steepness of the hyperbolic radio wavefront and the slope of the lateral distribution of the radio amplitude. Moreover, we show vectorial measurements of the electric field with the tripole antennas of the latest LOPES setup. Finally, we discuss open questions as well as the potential impact of the lessons learned at LOPES for future antenna arrays.
Azathioprine (AZA) is widely used in the treatment of autoimmune inflammatory diseases. AZA is normally rapidly and almost completely converted to 6-mercaptopurine (6-MP) in the liver, which is ...further metabolized into a variety of pharmacologic active thiopurine metabolites. 6-MP is catabolized by xanthine oxidase (XO) to the inactive metabolite 6-thiouric acid. The authors report the case of a woman with chronic autoimmune pancreatitis unable to form active thiopurine metabolites. The 55-year-old woman presented with weight loss, progressive elevation of liver transaminases, and serum amylase. She was treated with prednisolone 30 mg/day (1 mg/kg) and AZA was increased to 75 mg/day (2.5 mg/kg); this was later increased to 150 mg/day (5 mg/kg). Despite good patient compliance, the active metabolites of AZA, 6-thioguanine nucleotides (6-TGN), and 6-methylmercaptopurine ribonucleotides (6-MMPR) could not be detected in the erythrocytes (RBC). Subsequently, AZA was switched to high-dose 6-MP (2.5 mg/kg) and the XO inhibitor allopurinol was added. After 1 week, this combination led to a high 6-TGN level of 616 pmol/8 x 10(8) RBC and a 6-MMPR level of 1319 pmol/8 x 10(8) RBC. Three weeks after starting treatment, 6-TGN and 6-MMPR even reached toxic levels (1163 pmol/8 x 10(8) RBC and 10015 pmol/8 x 10(8) RBC, respectively) so that 6-MP treatment was discontinued. To elucidate this finding, 6-MP (1.7 mg/kg) was prescribed for 3 days without allopurinol. The woman was not able to form active thiopurine metabolites. According to the authors, this is the first report of a patient unable to form detectable active thiopurine metabolites on AZA and 6-MP therapy despite good patient compliance. High XO activity led to an inability to form detectable levels of active thiopurine metabolites 6-TGN and 6-MMPR. This finding emphasizes the important role of XO in the biotransformation of thiopurines.
The Pierre Auger Observatory has been designed to measure the energy spectrum, the arrival direction, and the mass composition of cosmic rays above 10 18 eV with a hybrid detector system. It will ...finally consist of an array of 1600 water-Cherenkov Surface Detectors (SD) on a 1.5 km triangular grid and 24 fluorescence telescopes (FD) in four stations on the perimeter of the 3000 km 2 experimental area. The Observatory is at present under construction in the Pampa Amarilla near the town of Malarguumle - Province of Mendoza, Argentina. The construction of this Southern site will be completed in early 2006. We present the hybrid design of the Observatory (SD, FD), the current status of construction and the performance of the detector gained during regular operation in the installation phase. Since mid 2004, the first half of the FD telescopes have been installed and more than one quarter of the SD array has been deployed. The Observatory will be complemented by a Northern site in Utah or Colorado to achieve uniform full sky coverage
Radio signals emitted from cosmic ray air showers can be used as a new technique for the detection of ultra-high energetic cosmic rays or neutrinos at energies above 10 18 eV. To apply this technique ...for the detection of air showers, cost effective new antennas and on-line self-trigger systems have to be developed. In large-scale detector arrays an everywhere radio quiet region is rarely available. Therefore, a self-trigger for each radio station with effective suppression of radio interferences and transients is necessary. A FPGA based self-trigger was developed with the help of externally triggered data. A logarithmic-periodic dipole antenna was used first, but a simple crossed polarized small aperiodic loaded loop antenna turned out to be more robust and cost effective. We present studies of antenna design, analog electronics, trigger, and system design.
Radio Measurements of Air Showers with LOPES Schröder, F G; Apel, W D; Arteaga-Velazquez, J C ...
Journal of physics. Conference series,
01/2013, Letnik:
409, Številka:
1
Journal Article
Recenzirano
Odprti dostop
LOPES is a digital antenna array for the radio measurement of cosmic-ray air showers at energies around 1017 eV. It is triggered by the KASCADE-Grande air-shower array at the Karlsruhe Institute of ...Technology (KIT), Germany. Because of an absolute amplitude calibration and a sophisticated data analysis, LOPES can test models for the radio emission to an up-to-now unachieved level, thus improving our understanding of the radio emission mechanisms. Recent REAS simulations of the air-shower radio emission come closer to the measurements than any previously tested simulations. We have determined the radio-reconstruction precision of interesting air-shower parameters by comparing LOPES reconstructions to both REAS simulations and KASCADE-Grande measurements, and present our latest results for the angular resolution, the energy and the Xmax reconstruction based on the radio measurement of about 500 air showers. Although the precision of LOPES is limited by the high level of anthropogenic noise at KIT, it opens a promising perspective for next-generation radio arrays in regions with a lower ambient noise level.
Aims.The capability of radio antenna arrays to measure cosmic ray air showers with very large zenith angles is explored. This is important, since a possible neutrino detection has to fulfill two ...requirements. First: antennas should be able to detect very inclined cosmic ray air showers, and second: it should be possible to estimate the distance to the shower maximum, since neutrinos are most likely to travel far through the Earth's atmosphere without interaction and induce air showers close to the ground. Methods.LOPES (LOFAR PrototypE Station; LOFAR – LOw Frequency ARray), an array of dipole antennas, is used for the detection of inclined cosmic ray air showers. LOPES is co-located and triggered by the KASCADE (KArlsruhe Shower Core and Array DEtector) experiment, which also provides information on air shower properties such as electron and muon numbers on the ground, as well as the arrival direction. Radio emission of nearly vertical cosmic ray air showers has been detected by LOPES. Results.LOPES-10 (the first phase of LOPES, consisting of 10 antennas) detected a significant number of cosmic ray air showers with a zenith angle larger than 50°, and many of these have very high radio field strengths. The most inclined event that has been detected with LOPES-10 has a zenith angle of almost 80°. This is proof that the new technique is also applicable for cosmic ray air showers with high inclinations, which in the case that they are initiated close to the ground, can be a signature of neutrino events. Conclusions.Our results indicate that arrays of simple radio antennas can be used for the detection of highly inclined air showers, which might be triggered by neutrinos. In addition, we found that the radio pulse height (normalized with the muon number) for highly inclined events increases with the geomagnetic angle, which confirms the geomagnetic origin of radio emission in cosmic ray air showers.
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