U. Schwarz

Combining magnetic resonance imaging and ultrawideband radar: A new concept for multimodal biomedical imaging

Due to the recent advances in ultrawideband (UWB) radar technologies, there has been widespread interest in the medical applications of this technology. We propose the multimodal combination of magnetic resonance (MR) and UWB radar for improved functional diagnosis and imaging. A demonstrator was established to prove the feasibility of the simultaneous acquisition of physiological events by magnetic resonance imaging and UWB radar. Furthermore, first in vivo experiments have been carried out, utilizing this new approach. Correlating the reconstructed UWB signals with physiological signatures acquired by simultaneous MR measurements, representing respiratory and myocardial displacements, gave encouraging results which can be improved by optimization of the MR data acquisition technique or the use of UWB antenna arrays to localize the motion in a focused area.

Physiological signatures monitored by ultra-wideband-radar validated by magnetic resonance imaging

To validate physiological signatures acquired by ultra-wideband (UWB)-radar, like breathing and cardiac deformation, we propose the comparison with simultaneously acquired in-vivo magnetic resonance imaging (MRI). In this way it can be evaluated how physiological signals from the thoracic wall and internal structures, e.g., the heart, monitored by UWB-radar correlate with the physiological reality displayed by MR-imaging.

Preliminary investigations of chest surface identification algorithms for breast cancer detection

Ultra-wideband sensing and imaging provides perspectives for early-stage breast cancer detection. This paper deals with problems related to the accurate identification of the breast surface. The applicability of the published and recently extended boundary scattering transform (BST) is investigated. In order to reconstruct the whole breast region, the so far planar scanning of the antennas is extended to a spatial scanning. The experimental study is carried out based on metallic test objects and a female dressmaker torso.

Design and application of dielectrically scaled double-ridged horn antennas for biomedical UWB radar applications

Ultra-wideband sensing begins to play an important role in biomedical diagnostic systems. Promising and relevant applications include remotely monitored vital functions as well as the characterization of tissues and organs. The acquisition of such physiological signatures requires small and radiation-efficient antennas, designed for ultra-wideband frequency operation. We have developed physically small and adjustable double-ridged horn antennas with which we could demonstrate the specific advantages of miniaturized, dielectrically matched sensor elements in a direct mode compared to remote sensor applications. As a logical consequence of these results, we have considered to replace the lossy high-permittivity liquid by low-loss high-permittivity solid ceramic material to improve the degree of miniaturization and the radiation efficiency further. Some unexpected peculiarities related to this approach are discussed.

Physically small and adjustable double-ridged horn antenna for biomedical UWB radar applications

Biomedical applications of ultra-wideband radar promise a very important means to remotely characterise tissues and organs. The acquisition of such physiological signatures requires small and efficient antennas, designed for ultra-wideband frequency operation. We have designed and characterised physically small and adjustable double-ridged horn antennas for frequencies from 1 to 10 GHz. The miniaturisation of the radiating elements was accomplished by immersion into a high permittivity liquid dielectric. The effect of dielectric scaling on size, input matching, radiation patterns, and gain has been evaluated by comparison with a double-ridged horn antenna designed for operation in air.

Improved Breast Surface Identification for UWB Microwave Imaging

Electromagnetic ultra-wideband sensing and imaging provides perspectives for early-stage breast cancer detection. This paper deals with problems related to the accurate three-dimensional identification of the breast surface. The SEABED algorithm based on the Inverse Boundary Scattering Transform (IBST) represents a powerful basic approach for surface detection problems.

Experimental validation of high-permittivity ceramic double-ridged horn antennas for biomedical ultra-wideband diagnostics

We have presented a complete characterization of a miniature ceramic double-ridged horn antenna. The input matching, radiation pattern, and impulse response revealed a performance promising for biomedical diagnostics. A further improvement and miniaturization will become accessible by optimized manufacturing processes and feed impedance, respectively. Preliminary volunteer measurements showed the suitability of the antennas for the envisaged applications and justify our approach. This work has been funded by the German Research Foundation (priority programme UKoLoS, project acronym “ultraMEDIS”).

Ultra-wideband antennas for combined magnetic resonance imaging and UWB radar applications

Magnetic resonance imaging (MRI) is one of the most highly appreciated medical diagnostic techniques worldwide. Recent developments aim at adding the capability of creating focused images of moving objects. Among the potential navigator techniques required for such an improved MRI is ultra-wideband (UWB) radar. We have studied the performance of UWB antennas for biomedical imaging inside the 3-Tesla MRI system at PTB Berlin. The strong static and time variant magnetic fields give rise to severe mechanical and electrical interactions due to the induced electromagnetic forces. On the other side, the high magnetic field homogeneity required for MR scans can also be affected adversely by the presence of the UWB antennas. The requirements resulting for the design of MRI compatible antennas have been identified and implemented in terms of a novel type of double-ridged horn antenna. We describe the design of the antenna and its performance for magnetic resonance imaging.

Fusion of magnetic resonance imaging and ultra-wideband-radar for biomedical applications

Due to the recent advances in ultra-wideband (UWB)-radar technologies, there has been widespread interest in medical applications of this technology. We propose the multimodal combination of magnetic resonance (MR) and UWB-radar for improved functional diagnosis and imaging. A demonstrator was established to prove the feasibility of simultaneous acquisition of physiological events by magnetic resonance imaging and UWB-radar.

Miniature double-ridged horn antennas composed of solid high-permittivity sintered ceramics for biomedical ultra-wideband radar applications

Ultra-wideband (UWB) radar sensors are attracting more and more attention, e.g., for biomedical applications. In contrast to established techniques like X-ray tomography or invasive diagnostic approaches, UWB radar offers the potential for remote access and ultra-low power signal intensities. Inspired by promising studies of breast tumor imaging [1], we are continuing and extending our previous work on biomedical M-sequence radar and antenna techniques [2]. We describe the development and the potential of innovative double-ridged horn antennas, based on high-permittivity sintered ceramics, which have been adapted to the envisaged biomedical applications. In this context, the miniaturization of UWB antennas, due to the restriction to small examination areas, without compromising the electromagnetic fidelity is the overall challenge. For the dielectric scaling of antennas with the potential to operate over wide bandwidths, we focus on nearly frequency independent, high-permittivity and low-loss materials. In what follows, we describe the arduous path from the first idea to functional laboratory versions of double-ridged horn antennas based on solid sintered ceramics. In this way, the paper illustrates the successful interdependence between microwave engineering and mechanical and material engineering.