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Temperature monitoring during thermal therapies is used to regulate the amount of heat distributed to the cancerous tissue and therefore improve the clinical outcome of the oncological treatment. For the development of a hybrid hyperthermia system with non-invasive temperature monitoring by means of ultra-wideband (UWB) imaging, the optimal configuration of sensing antennas and heating applicators has to be investigated. In this paper we present the results of numerical simulations of several possible antenna arrangements, which are then validated by experiments with the radar system. The performance of each channel configuration was analyzed and benefits for the different clinical scenarios were specified.

The temperature dependence of the dielectric parameters of tissues and tissue-mimicking phantoms is very important for non-invasive temperature measurement in medical applications using microwaves. We performed measurements of this dependence in the temperature range of 25–50°C using distilled water as a reference liquid commonly used in dielectric property studies. The results were compared with the literature model in the frequency range of 150–3000 MHz. Using this method, the temperature dependence of dielectric parameters of a new muscle tissue-mimicking phantom based on agar, polyethylene powder, and polysaccharide material TX-151 was measured in the temperature range of 25–50°C. The temperature dependence of the dielectric properties of this new muscle phantom was fitted to that of the two-pole Cole–Cole model and the deviation of the results between measured and modeled data was quantified.

Microwave sensors have recently been introduced as high-temporal resolution sensors, which could be used in the contactless monitoring of artery pulsation and breathing. However, accurate and efficient signal processing methods are still required. In this paper, the matrix pencil method (MPM), as an efficient method with good frequency resolution, is applied to back-reflected microwave signals to extract vital signs. It is shown that decomposing of the signal to its damping exponentials fulfilled by MPM gives the opportunity to separate signals, e.g., breathing and heartbeat, with high precision. A publicly online dataset (GUARDIAN), obtained by a continuous wave microwave sensor, is applied to evaluate the performance of MPM. Two methods of bandpass filtering (BPF) and variational mode decomposition (VMD) are also implemented. In addition to the GUARDIAN dataset, these methods are also applied to signals acquired by an ultra-wideband (UWB) sensor. It is concluded that when the vital sign is sufficiently strong and pure, all methods, e.g., MPM, VMD, and BPF, are appropriate for vital sign monitoring. However, in noisy cases, MPM has better performance. Therefore, for non-contact microwave vital sign monitoring, which is usually subject to noisy situations, MPM is a powerful method.

Monitoring of the temperature distribution inside the tissue to be treated plays the key role in success and safety of thermal therapies. Active microwave imaging represents a promising approach for non-invasive tissue temperature monitoring during hyperthermia treatment. In the present paper, an approach for quantitative non-invasive tissue temperature estimation via UWB imaging is described. Two types of imaging algorithms are considered - Delay and Sum beamforming and Truncated Singular Value Decomposition scheme. The capabilities of the proposed imaging algorithms are demonstrated by experiments with liquid phantoms. The results of our investigation show that both imaging algorithms can be applied for detection and estimation of the temperature induced dielectric property changes.

This contribution deals with the detection and imaging of magnetic modulated nanoparticles by means of ultra-wideband sensing. We performed phantom measurements in a practical measurement setup where the magnetic nanoparticles are modulated by a static and a low periodic changing external magnetic field. We investigated the influence of the modulation type of the polarizing magnetic field on both, detectability and imaging of magnetic nanoparticles. We can conclude that both modulations generate a sufficient contrast in order that the nanoparticles were detected at the correct position in a three-dimensional volume. The imaging results, including 32 channels, indicate that the two state (ON/OFF) modulation of the magnetic field under constant environmental conditions shows better results compared to a sinusoidal excitation of the magnetic field.

Microwave sensing represents a promising approach for non-invasive tissue temperature monitoring during hyperthermia treatment. Tissue mimicking phantom materials with corresponding dielectric properties and suitable for heating experiments are essential for preliminary methodical investigations as well as for the development of the measurement hardware. In the present paper, a fat tissue mimicking phantom material is investigated depending on the temperature in the range between 30 °C and 50 °C and the frequency range between 0.5 GHz and 7 GHz. The measured data are modeled by means of a two-pole Cole-Cole model and the temperature dependence of the Cole-Cole parameters is fitted by means of a second-order polynomial. The results show that this material imitate the dielectric properties of real fat tissue as well as its very low temperature dependence appropriately and can be used for practical experiments.

The temperature dependency of the dielectric properties of tissues is very important for the development of novel microwave systems intended for non-invasive temperature monitoring. This paper deals with the measurement and optimization of the temperature dependence of the dielectric parameters of a muscle tissue mimicking phantom. The measurements were performed in the frequency band 0.1 – 3 GHz and in the temperature range 25 – 45 °C. The differences in the dielectric parameters caused by temperature change were analyzed and compared with the reference.&nbsp

This paper deals with the detection of magnetic modulated nanoparticles by means of ultra-wideband sensing. Magnetic nanoparticles are modulated by an external magnetic field. The resulting scattering changes of the magnetic nanoparticles are analyzed depending on the mass, the magnetic field strength and the surrounding medium in which the particles are embedded. The experiments are carried out on phantom measurements and the results show a linear behavior of the measured radar signal depending on the mass. Furthermore, the experiments show that the optimal choice of the magnetic field strength can increase the detectability of the magnetic nanoparticles. This applies both to particles that are diluted in distilled water and to particles that are embedded in a solid surrounding medium.

Non-invasive differential temperature monitoring by means of ultra-wideband sensing is a promising approach concerning temperature controlling during thermotherapy. In this paper the principal of temperature difference detection by UWB radar is explained and appropriate phantom measurements are discussed. In a first step, temperature dependent dielectric properties of the phantom materials (sunflower oil and distilled water) are analyzed. Subsequently, temperature dependent phantom measurements are conducted where the temperature dependent signal changes of the received UWB signals are investigated. Results show a linear behavior between the received differential radar signals and the temperature differences of the target in the considered temperature range. Furthermore, investigations show that temperature changes of the target, which are common in thermal therapy (e.g., hyperthermia), are detectable by means of UWB radar.

UWB microwave imaging has proven to be a promising technique for early-stage breast cancer detection. The extensive image reconstruction time can be accelerated by parallelizing the execution of the underlying beamforming algorithms. However, the efficiency of the parallelization will most likely depend on the grade of parallelism of the imaging algorithm and of the utilized hardware. This paper investigates the dependencies of two different beamforming algorithms on multiple hardware specification of several graphics boards. The parallel implementation is realized by using NVIDIA’s CUDA. Three conclusions are drawn about the behavior of the parallel implementation and how to efficiently use the accessible hardware.

The temperature dependency of dielectric properties of tissue mimicking materials and tissues is a crucial factor for non-invasive temperature monitoring in microwave thermotherapy. This contribution deals with temperature dependent dielectric spectroscopy measurements by means of ultra-wideband sensing. Beside the standard three term calibration, a temperature dependent calibration approach is supposed. Both methods are validated by measuring the dielectric properties of distilled water in the frequency range of 0.5 GHz up to 7 GHz and in the temperature range of 26 ° Ο up to 50 °C. Compared with the Ellison model as reference, the temperature dependent calibration approach shows better results than the standard calibration at room temperature. Furthermore, the temperature dependent dielectric properties of a tumor mimicking agar phantom in the same frequency and temperature range are presented.

This paper investigates the potential of magnetic modulated iron oxide nanoparticles in terms of a contrast enhancement for Ultra-wideband (UWB) breast imaging. The work is motivated by the low dielectric contrast between tumor and normal glandular/fibroconnective tissue. The influence of an external polarizing magnetic field on pure and coated magnetite nanoparticles is investigated in this contribution. Measurements were conducted using M-sequence UWB technology and an oil-gelatin phantom. It is shown that a coating, which is necessary for clinical use, results in a lower signal response, and thus leads to a lower detectability of magnetic modulated nanoparticles.

This paper presents the hardware and software design of a massive MIMO system for fast UWB Imaging. The RF hardware is based on pseudo noise code (M-sequence) technology. The digital data acquisition is realized by means of a PXIe data streaming solution. This device includes in summary 24 transmitter and 48 receiver ports and, therefore, supports measurements of 1152 independent signal channels without any switch matrix. The maximum measurement rate for 48 channels in parallel is 500 IRF per second, for all 1152 channels 10 IRF per second are achievable. This performance makes it suitable for multichannel static imaging purposes as well as for very fast dynamic measurements.

This paper presents the results of a first self-experiment of one healthy volunteer by means of ultra-wideband sensing. Measurements are performed by M-sequence technology. First, we investigate the reproducibility of single measurement trials using a MIMO ultra-wideband breast imaging system. Results show that variations caused by a repositioning of the breast are higher than expected tumor responses, derived from phantom measurements. In a second scenario we use a two-channel ultra-wideband system with a sufficient measurement rate to consider the influence of human body vital signs. Investigations clearly show a detectability of breathing as well as heart activity.

Microwave imaging of weak scattering objects within a strong multi-path environment is a challenging task. Differential imaging is used when the wanted targets are subjected to induced or inherent changes while the surrounding keeps stable. The paper illustrates the approach of differential imaging, discusses the performance limitations by random signal perturbations, and shows some examples from medical engineering.

Magnetic modulated nanoparticles are a promising approach to enhance microwave breast cancer detection and imaging. Assuming that functionalized magnetic nanoparticles are able to accumulate selectively within tumorous tissue, this approach can increase the diagnostic reliability. This contribution deals with detecting and imaging of magnetic nanoparticles by means of ultra wideband sensing. Magnetic nanoparticles are modulated by means of an external magnetic field and the resulting scattering changes of the magnetic nanoparticles are measured using M-sequence radar technology. Investigations are based on phantom measurements and the detection of the response caused by magnetic nanoparticles is realized by a differential measurement between ON- and OFF-state of the polarizing magnetic field. Results show a detectability of magnetic nanoparticles in a realistic measurement scenario. Based on this, 3D images for different amounts of magnetic nanoparticles are realized using a delay-and-sum beamforming algorithm.

Practical as well as theoretical aspects of medical microwave imaging require short antennas with short impulse response function for transmission and reception of the sounding fields. Since usually antenna design goals are targeted to good feed point matching, one runs into unsolvable problems in case of wideband measurements. The paper will introduce a radar channel model based on electrically short antennas and it will discuss how to circumvent the mismatch problems.

The vitality of a human being is closely connected to temporal variations of its body geometry. This is quite obvious in the case of walking. But also when resting, the motion of inner organs such as lung or heart causes geometric alterations which may be registered by high-resolution ultra-wideband radar. Since the radio waves radiated by such radars are absolutely harmless, they may be deployed for monitoring of resident activities helping to ensure health, safety, and well-being of aged or needy people. These waves may also penetrate most of building materials and snow which makes them useful to detect earthquake and avalanche survivors, too. The most challenging task is the registration of respiration activity of an unconscious person. The principle of breathing motion detection by radar is explained and the major handicaps as well as appropriate counter measures are discussed. The possible structure of a survivor and residential injury detection radar system is considered and some results from field trials are summarized.

This paper presents setup and preliminary investigations of simultaneous electrical and mechanical heart activity measurements. The ECG is registered by a commercial amplifier in connection with a developed synchronization unit including AD conversion. The mechanical heart movement is recorded by means of a two-channel UWB M-sequence radar system. The sensor position dependent signals reflect physiological issues in a reproducible way. Future research has to figure out to what extent UWB microwave sensing can be established in cardiovascular diagnostics.

This paper deals with detection and imaging of magnetic modulated nanoparticles by means of ultra-wideband sensing. Investigations base on ON/OFF modulation of the external polarizing magnetic field. Measurements were conducted using M-sequence technology and a phantom consisting of a skin layer and cream as healthy tissue surrogate. The detection of the magnetic nanoparticles is realized by a differential measurement between the ON- and OFF-state of the polarizing magnetic field. Furthermore, a calibration approach is introduced to reduce the influence of the magnetic field in the measured radar response. Results show the detectability of different amounts of magnetic nanoparticles for a realistic measurement scenario. Based on this, a first imaging of the magnetic nanoparticles is realized using a delay-and-sum beamforming algorithm.

In this paper we present a preliminary experimental investigation of detection of very low dielectric parameter changes caused by temperature inside a phantom. The detection measurements were performed using the M-sequence UWB radar device and homogenous gelatin breast phantom. The results show the potential of UWB sensing for noninvasive temperature determination.

In the framework of medical applications of microwaves, magnetic nanoparticles enhanced microwave imaging represents a promising diagnostic modality. As a matter of fact, it merges the safety, low-cost and portability of microwave technology with the increased specificity enabled by the selective targeting capability of magnetic nanoparticles. In particular, a key ingredient of this technique is the possibility of modulating the response of nanoparticles in the microwave range by means of an external polarizing magnetic field. To this end, the amplitudes of the polarizing field have to be properly set, in order to achieve optimal performances. In this communication, we present an experimental study aimed at optimizing the working conditions in terms of field strength of a ultra-wide band radar system for detecting a magnetic nanoparticle induced contrast.

Zusammenfassung Robuste Sensoren für die zerstörungsfreie Materialcharakterisierung im Labor und unter rauen industriellen Bedingungen sind von zunehmendem technischen und ökonomischen Interesse. Dieser Artikel behandelt die Entwicklung und Anwendung eines prozesstauglichen, modularen und breitbandigen impedanzspektroskopischen Hard- und Softwarekonzepts für den Feld- und Laboreinsatz. Besondere Beachtung finden weiterhin auch technische und biophysikalische Aspekte der Bio-Impedanzspektroskopie.

The paper reports from first trials of remote heartbeat and breathing monitoring of milk cows. An UWB M-sequence device is used as high-resolution short-range radar sensor. Breathing and heart motion could be detected and well separated by their rates as well as the depth of their origin.

The heart rate variability (HRV) can be taken as an indicator of the coordination of the cardio-respiratory rhythms. Bispectral analysis using a direct (fast Fourier transform based) and time-invariant approach has shown the occurrence of a quadratic phase coupling (QPC) between a low-frequency (LF: 0.1 Hz) and a high-frequency (HF: 0.4-0.6 Hz) component of the HRV during quiet sleep in healthy neonates. The low-frequency component corresponds to the Mayer-Traube-Hering waves in blood pressure and the high-frequency component to the respiratory sinus arrhythmia (RSA). Time-variant, parametric estimation of the bispectrum provides the possibility of quantifying QPC in the time course. Therefore, the aim of this work was a parametric, time-variant bispectral analysis of the neonatal HRV in the same neonates used in the direct, time-invariant approach. For the first time rhythms in the time course of QPC between the HF component and the LF component could be shown in the neonatal HRV.

UWB microwave imaging has been investigated as an alternative approach for early-stage breast cancer detection. In this paper we present preliminary experimental results towards contrast agent enhanced imaging in order to overcome the problem of the low dielectric contrast between healthy and tumorous tissue. The measurements were done based on M-sequence UWB radar devices and oil-gelatin breast phantoms. Our results confirm the outcome of recently published numerical studies, claiming to detect contrast agent accumulations of clinical applicable doses by electromagnetic sensing.

Objectives : The quadratic phase-coupling (QPC) within burst patterns during electroencephalic burst suppression has been quantified. Methods : It can be shown that a QPC exists between the frequency ranges 0–2.5 and 3–7.5 Hz and between the frequency ranges 0–2.5 and 8–12 Hz. By means of time-variant bicoherence analysis, a strong phase-locking between the modulating and the modulated component can be identified. The phase-locking is demonstrable within the first 250 ms after the burst onset and comes up to the maximum between 750 and 1250 ms. Results : The effect is maintained over the whole first part of the burst (2 s) with a decreasing tendency after 1250 ms. All these effects cannot be found in the EEG before entering the burst suppression period (BSP). The transient coupling phenomena in the EEG bursts during BSP can be regarded as indicators for short-term interrelations between the underlying electrophysiologic processes. Conclusions : It can be suggested that the method introduced for the quantification of the sedation depth should be used.

The article deals with recent development steps toward monolithically integrated micro-Network Analyzer (μNA). The device will deploy M-Sequence-based single-chip transceivers with a built-in ultra-wideband wave separation unit in the receiver chains. The introduced on-chip wideband wave separation is realized using an optimized resistive directional coupler combined with a customized differential LNA as detector. The wave separation works almost down to DC, and its upper frequency limit is determined by the performance of the implemented technology (i.e., bridge resistors, transistors, etc.), the selected circuit topology, and the wirings of particular coupler components but also by the IC packaging itself. Even though the upper limit is designed to be compatible with the analog input bandwidth of the receiver circuit [which is about 18 GHz for naked die (Kmec et al., M-Sequence based single chip UWB-radar sensor. ANTEM/AMEREM 2010 Conference, Ottawa, 2010)], the packaged IC is intended for use up to 8 GHz. Finally, the discussed transceiver is a further development of the mother SiGe System-on-Chip (SoC) presented in the work cited above.

The article deals with a fully monolithically integrated single-chip M-sequence-based UWB-radar sensor, its architecture, selected design aspects and first measurement results performed on wafer and with packaged IC modules. The discussed chip is equipped with one transmitter and two receivers. The IC was designed and manufactured in commercially available high-performance 0.25 μm SiGe BiCMOS technology (f t = 110 GHz). Due to the combination of fast digital and broadband analogue system blocks in one chip, special emphasis has been placed on the electrical isolation of these functional structures. The manufactured IC is enclosed in a low-cost QFN (quad flat-pack no-leads) package and mounted on a PCB permitting the creation of MIMO-sensor arrays by cascading a number of modules. In spite of its relatively high complexity, the sensor head features a compact design (chip size of 2 × 1 mm2, QFN package size 5 × 5 mm2) and moderate power consumption (below 1 W at −3 V supply). The assembled transceiver chip can handle signals in the frequency range from near DC up to 18 GHz. This leads to an impulse response (IRF) of FWHD ≈ 50 ps (full width at half duration).

The time dynamics of the quadratic phase coupling within burst patterns during electroencephalic burst-suppression has been quantified. It can be shown that a transient quadratic phase coupling (QPC) exists between the frequency ranges 0 to 2.5 and 3 to 7.5 Hz and between the frequency ranges 0 to 2.5 and 8 to 12 Hz. The QPC can be explained by an amplitude modulation, where the slow rhythm modulates the rhythmic activities with a higher frequency. By means of time-variant bicoherence analysis, a strong phase-locking between the modulating and the modulated component can be identified. The phase-locking is demonstrable within the first 250 ms after the burst onset and comes up to the maximum between 750 and 1250 ms. The effect is maintained over the whole first part of the burst (2 s) with a decreasing tendency after 1250 ms. All these effects cannot be found in the EEG before entering the burst suppression period (BSP). The transient coupling phenomena in the EEG bursts during BSP can be regarded as indicators for short-term interrelations between the underlying electrophysiologic processes.