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Objectives Grating-interferometry-based mammography (GIM) might facilitate breast cancer detection, as several research works have demonstrated in a pre-clinical setting, since it is able to provide attenuation, differential phase contrast, and scattering images simultaneously. In order to translate this technique to the clinics, it has to be adapted to cover a large field-of-view within a clinically acceptable exposure time and radiation dose. Methods We set up a grating interferometer that fits into a standard mammography system and fulfilled the aforementioned conditions. Here, we present the first mastectomy images acquired with this experimental device. Results and conclusion Our system performs at a mean glandular dose of 1.6 mGy for a 5-cm-thick, 18%-dense breast, and a field-of-view of 26 × 21 cm2. It seems to be well-suited as basis for a clinical-environment device. Further, dark-field signals seem to support an improved lesion visualization. Evidently, the effective impact of such indications must be evaluated and quantified within the context of a proper reader study. Key Points • Grating-interferometry-based mammography (GIM) might facilitate breast cancer detection, since it is sensitive to refraction and scattering and thus provides additional tissue information. • The most straightforward way to do grating-interferometry in the clinics is to modify a standard mammography device. • In a first approximation, the doses given with this technique seem to be similar to those of conventional mammography.

Grating interferometry mammography (GIM) is an experimental breast imaging method at the edge of being clinically implemented. Besides attenuation, GIM can measure the refraction and scattering of x-rays resulting in differential phase contrast (DPC) and dark-field (DF) images. In this exploratory study, we assessed the feasibility of using microbubbles as a contrast agent in GIM. Two millilitres of microbubbles and iodine were respectively injected into ex vivo breast phantoms, consisting of fresh chicken breasts. Native and postcontrast images were acquired with a clinically compatible GIM setup, operated at 38 kVp, 14-s acquisition time, and with a dose of 1.3 mGy. The visibility of the contrast agents was analysed in a side-by-side comparison by three radiologists. The contrast-to-noise-ratio (CNR) was calculated for each contrast agent. We found that both contrast agents were judged to be visible by the readers. The mean CNR was 3.1 ± 1.9 for microbubbles in DF and 24.2 ± 6.5 for iodine in attenuation. In conclusion, this is a first proof-of-mechanism study that microbubbles could be used as a contrast agent in clinically compatible GIM, due to their scattering properties, which implies the potential use of a contrast agent with a high safety profile in x-ray-based breast imaging. ISSN:2509-9280

We present a concept for a combined selection and focus field generator for whole-body magnetic particle imaging (MPI). Predictions for field of view, gradient field strength, slew rate, and power consumption are calculated and discussed with the help of finite-element simulations.

Grating-interferometry-based mammography (GIM) might facilitate breast cancer detection, as several research works have demonstrated in a pre-clinical setting, since it is able to provide attenuation, differential phase contrast, and scattering images simultaneously. In order to translate this technique to the clinics, it has to be adapted to cover a large field-of-view within a clinically acceptable exposure time and radiation dose.We set up a grating interferometer that fits into a standard mammography system and fulfilled the aforementioned conditions. Here, we present the first mastectomy images acquired with this experimental device.Our system performs at a mean glandular dose of 1.6 mGy for a 5-cm-thick, 18%-dense breast, and a field-of-view of 26 × 21 cm2. It seems to be well-suited as basis for a clinical-environment device. Further, dark-field signals seem to support an improved lesion visualization. Evidently, the effective impact of such indications must be evaluated and quantified within the context of a proper reader study.• Grating-interferometry-based mammography (GIM) might facilitate breast cancer detection, since it is sensitive to refraction and scattering and thus provides additional tissue information. • The most straightforward way to do grating-interferometry in the clinics is to modify a standard mammography device. • In a first approximation, the doses given with this technique seem to be similar to those of conventional mammography.

An MR-electrophysiology (EP) catheter is presented that provides full diagnostic EP functionality and a high level of radiofrequency safety achieved by custom-designed transmission lines. Highly resistive wires transmit intracardiac electrograms and currents for intracardiac pacing. A transformer cable transmits the localization signal of a tip coil. Specific absorption rate simulations and temperature measurements at 1.5 T demonstrate that a wire resistance > 3 kΩ/m limits dielectric heating to a physiologically irrelevant level. Additional wires do not increase tip specific absorption rate significantly, which is important because some clinical catheters require up to 20 electrodes. It is further demonstrated that radiofrequency-induced and pacing-induced resistive heating of the wires is negligible under clinical conditions. The MR-EP catheters provided uncompromised recording of electrograms and cardiac pacing in combination with a standard EP recorder in MR-guided in vivo EP studies, and the tip coil enabled fast and robust catheter localization. In vivo temperature measurements during such a study did not detect any device-related heating, which confirms the high level of safety of the catheter, whereas unacceptable heating was found with a standard EP catheter. The presented concept for the first time enables catheters with full diagnostic EP functionality and active tracking and at the same time a sufficient level of radiofrequency safety for MRI without specific absorption rate-related limitations.

X-ray emission spectra from thin targets show significant directional effects that have their origin in the polar dependence of the atomic bremsstrahlung cross section. This fact has led to the idea of enhancing the characteristic lines from an electron-impact X-ray source by observing X-rays from optically thin (foil) targets in a direction antiparallel to that of the incident electron beam. Efficiency considerations dictate the use of foils of maximum possible thickness consistent with the desired degree of characteristic line enhancement. Foil thickness and electron energy are crucial parameters determining the angular divergence of the electron beam within the foil and hence the extent of characteristic line enhancement. The aim of this article is to find a relationship between electron energy and foil thickness that preserves a high characteristic to bremsstrahlung X-ray ratio while maximizing efficiency. This is achieved by relating the root mean square electron deflection angle, derived from the mass scattering power, to the angular width of the “valley”, centered on 180°, within which bremsstrahlung emission can be neglected. Representative spectra are presented and conclusions for applications and for further work are briefly presented.

A clinical MPI demonstrator system is being built [1] that will enable fast 3D imaging with 3D drive field excitation and rapid 3D focus fields. To date, all components have been realized only once, i.e., a 1D drive field coil (x direction), a 1D fast focus field (y direction), and a 1D selection and focus field (z direction). To test the respective components, a 3D image is acquired using a linear drive field trajectory.

Conventional electron impact X-ray sources invariably use solid state anodes. In this article a novel type of X-ray source is described in which X-rays are produced in a turbulently flowing liquid metal separated from the vacuum region of the X-ray source by a thin foil. The three diffusion processes (electron diffusion, heat conduction and turbulent mixing) which, together with convection, are responsible for thermal transport in liquid anode sources are briefly discussed and their relative importance is quantitatively assessed. When the mean lengths of these three diffusion processes are combined into a single parameter, σ, a simple Gaussian model of the spatial dependence of the temperature profile can be used to predict the loadability (W m−2 K−1) of the LIMAX arrangement. This model suggests that a DC load of several tens of kW can be maintained on a focus of 1 mm2 effective area and this estimate is confirmed by results from an experimental LIMAX apparatus. As a natural extension of this work, the combination of a LIMAX source with a secondary fluorescence target is proposed to yield a high radiance source of quasimonochromatic radiation for X-ray scatter imaging applications. A brief discussion of this proposal is given in connection with its potential applications in the fields of industrial and medical X-ray scatter imaging.

A novel type of electron-impact X-ray source is described in which X-rays are produced in a turbulently flowing liquid metal that is separated from the vacuum region of the X-ray source by a thin membrane. Following a summary of the physics of electron and photon transport applicable to the liquid metal anode X-ray (LIMAX), the three diffusion processes responsible for thermal transport in (electron diffusion, heat conduction and turbulent mixing) are briefly discussed and their relative importance is quantitatively assessed. A simple Gaussian model is presented allowing the characteristic ranges of the three diffusion processes to be combined into a mean total diffusion range. The extent to which heat diffuses in the time taken for the liquid metal stream to pass the electron focus permits the loadability (electron beam power density per unit maximum anode temperature rise) of the turbulently flowing liquid metal target to be assessed. A description of an experimental LIMAX facility constructed in these laboratories is given. Preliminary experimental results from the LIMAX facility are presented and satisfactory agreement is found between these results and the predictions of the Gaussian model for the mean total diffusion range. The suitability of the LIMAX proposal for X-ray scatter imaging investigations is briefly considered.

Supraleitende Quanteninterferenz-Detektoren, SQUIDs, registrieren kleinste Magnetfelder. Im Bereich der zerstorungsfreien Werkstoffprufung und des Biomagnetismus halten sie zunehmend Einzug. Ihre hohe Empfindlichkeit macht sie jedoch gleichzeitig anfallig fur ausere Storeinflusse.

Three concepts of integrated magnetometers intended for biomagnetic multichannel systems are investigated: The Ketchen-type magnetometer, the multiloop magnetometer and the magnetometer with integrated multiloop pickup coil (IMPUC). The devices are fabricated from YBa 2 Cu 3 O 7 -SrTiO 3 -YBa 2 Cu 3 O 7 thin-film multilayers, and step-edge grain-boundary Josephson junctions as well as ramp-edge junctions with PrBa 2 Cu 3 O 7 barriers are employed. The magnetometers are compared regarding their effective flux collecting area, inductance and noise performance. With an optimized layout for the multiloop device, we achieve an effective flux collecting area of 2.3 mm 2 at an inductance of 145 pH. At 77 K we measure a magnetic flux density noise down to √ S B =60 fT/√Hz at 1 Hz and of 17 fT/√Hz in the white noise regime. Due to the low noise levels of the magnetometers high quality magnetocardiograms were recorded inside a magnetically shielded room without signal averaging. The noise performance of the magnetometers is also analyzed in unshielded environment and in static magnetic fields.

A modular, 9-channel high-T/sub c/ SQUID system for magnetocardiography (MCG) was developed and tested in an unshielded environment. Galvanically-coupled magnetometers made from Y-Ba-Cu-O films, with intrinsic white noise levels as low as 70 fT//spl radic/Hz, are used as SQUID sensors. In an unshielded environment, a noise level of about 1 pT//spl radic/Hz for each channel was achieved using an active noise compensation system. A new digital planar gradiometer is proposed. First magnetocardiograms recorded in an unshielded environment are presented.

In order to identify suitable operating conditions for future clinical Magnetic Particle Imaging, peripheral nerve stimulation (PNS) and specific absorption rate (SAR) experiments have been performed by exposing volunteers to sinusoidally time-varying magnetic fields along and transverse to the body axis at frequencies from 24 kHz to 162 kHz. The findings show that future clinical MPI can advantageously be performed at elevated drive-field frequencies, with PNS restriction actually relaxed at higher frequencies, and with still acceptable SAR exposure.

We have designed and fabricated three types of high- SQUID (superconducting quantum interference device) magnetometers based on step-edge Josephson junctions using three different concepts of coupling magnetic flux into the SQUID: (i) a single pickup loop galvanically coupled to the SQUID, (ii) a flux transformer inductively coupled to the SQUID and (iii) a multiloop pickup loop used directly as the SQUID inductance. On a substrate we achieved an effective flux capture area of and for the inductively coupled and multiloop devices, respectively. Due to the low white noise levels of for the inductively coupled magnetometer and for the multiloop device high quality magnetocardiograms were recorded inside a magnetically shielded room without signal averaging.

After realizing the worlds' first preclinical magnetic particle imaging (MPI) demonstrator, Philips is now realizing the worlds' first whole-body clinical prototype to prove the feasibility of MPI for clinical imaging. After a brief introduction of the basic MPI imaging process, this contribution presents an overview on the determining factors for key properties, i.e., spatial resolution, acquisition speed, sensitivity, and quantitativeness, and how these properties are influenced by scaling up from preclinical to clinical instrumentation. Furthermore, it is discussed how this scale up affects the physiological compatibility of the method as well as hardware parameters such as power requirements for drive field generation, selection and focus field generation, and the design of the receive chain of the MPI device.

We have fabricated an integrated SQUID magnetometer based on Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7/ step-edge Josephson junctions. A tight coupling between the input coil and the SQUID washer has been achieved with a coupling coefficient K of 0.9. Noise measurements on our SQUIDs showed a nearly frequency independent flux noise of 50 /spl mu//spl Phi//sub 0///spl radic/Hz at 77 K. 1/f-noise contributions at lower temperatures were always completely suppressed by bias reversal. From our measurements of the field sensitivity and the flux noise we can estimate a field resolution of the magnetometer of 60 fT//spl radic/Hz down to 1 Hz.textlesstextgreater

The inductance Ls of YBa2Cu3O7 thin‐film square washer dc superconducting quantum interference devices was measured directly from 4.2 K up to the critical temperature Tc of the film. Ls(T) diverges close to Tc. Examining the temperature dependence of Ls two contributions are distinguished: the magnetic inductance, defined by the outer device geometry, and the temperature‐dependent kinetic inductance Lk associated with the thin‐film slit structure. Lk is found to scale with the square of the magnetic penetration depth λ(T) in a broad temperature range. The specific magnetic inductance per unit length of a long slit within the washer is measured to be ∼0.3 pH/μm. The impact of Ls(T) on device performance at elevated temperature is discussed.

Magnetic particle imaging (MPI) is a new medical imaging technique which performs a direct measurement of magnetic nanoparticles, also known as superparamagnetic iron oxide. MPI can acquire quantitative images of the local distribution of the magnetic material with high spatial and temporal resolution. Its sensitivity is well above that of other methods used for the detection and quantification of magnetic materials, for example, magnetic resonance imaging. On the basis of an intravenous injection of magnetic particles, MPI has the potential to play an important role in medical application areas such as cardiovascular, oncology, and also in exploratory fields such as cell labeling and tracking. Here, we present an introduction to the basic function principle of MPI, together with an estimation of the spatial resolution and the detection limit. Furthermore, the above-mentioned medical applications are discussed with respect to an applicability of MPI.

Current sources in the human body can be localized by measuring the biomagnetic fields with multichannel SQUID systems. Important system aspects are the noise level, the ambient field suppression, the dynamic range, the reliability, the number of channels, and the arrangement of gradiometers. From the user’s point of view the most important quality factor is the accuracy with which a current dipole can be localized. A test procedure is proposed to determine the localization power of the system. A 31‐channel‐SQUID system is presented together with the results of the test. The crucial parts of the system determining the accuracy are pointed out.

A modular multichannel SQUID-system, in which every single channel can be optimized or replaced individually, is presented. The DC-SQUIDs based on the materials NbN/MgO are prepared by thin film technology and show noise values below 10μΦ0/√Hz. A simplified way of coupling the modulation and feedback current directly to the coupling coil is realized The complete SQUID module including the superconducting shield was miniaturized down to a diameter of 5mm. The gradiometers are wire wound and an as made balancing better than 10−3 is achieved. The cryogenic system was optimized with respect to low vibrations and low helium boil off rate. Simple conductive paint with precisely adjusted surface resistivity is used for RF-shielding. The complete SQUID-electronic of one channel has been realized on one single board and uses a new bias modulation scheme to completely suppress intrinsic 1/f noise. The noise level of the complete system is below 10fT/√Hz. Biomagnetic measurements of the human heart and brain are presented. Single current dipole reconstructions and current density imaging techniques can be used to find the underlying sources. Using a special coil positioning system an overlay of the functional current images with morphological MR-images can be carried out.

A modular multichannel superconducting quantum interference device (SQUID) system, in which every channel can be optimized or replaced individually, was further improved. The number of channels was increased to 31. The noise level is better than 10 fT/ square root Hz. A novel way of RF shielding using conductive paint avoids degradation of the SQUID characteristics due to RF interference without introducing significant extra noise, so that the system works without any Faraday cage. A simplified way of coupling the modulation and feedback signal directly to the SQUID was developed and tested successfully. The SQUID module with superconducting connections to the gradiometer and its superconducting shield was miniaturized to an outer diameter of 5 mm, so that it can be placed near the gradiometer without introducing significant unbalance. Tests have demonstrated that the accuracy of the system with respect to the localization of a single current dipole is better than 2 mm. >

An MR-electrophysiology (EP) catheter is presented that provides full diagnostic EP functionality and a high level of radiofrequency safety achieved by custom-designed transmission lines. Highly resistive wires transmit intracardiac electrograms and currents for intracardiac pacing. A transformer cable transmits the localization signal of a tip coil. Specific absorption rate simulations and temperature measurements at 1.5 T demonstrate that a wire resistance > 3 kΩ/m limits dielectric heating to a physiologically irrelevant level. Additional wires do not increase tip specific absorption rate significantly, which is important because some clinical catheters require up to 20 electrodes. It is further demonstrated that radiofrequency-induced and pacing-induced resistive heating of the wires is negligible under clinical conditions. The MR-EP catheters provided uncompromised recording of electrograms and cardiac pacing in combination with a standard EP recorder in MR-guided in vivo EP studies, and the tip coil enabled fast and robust catheter localization. In vivo temperature measurements during such a study did not detect any device-related heating, which confirms the high level of safety of the catheter, whereas unacceptable heating was found with a standard EP catheter. The presented concept for the first time enables catheters with full diagnostic EP functionality and active tracking and at the same time a sufficient level of radiofrequency safety for MRI without specific absorption rate-related limitations.

NbN/MgO/NbN Josephson tunnel junctions have been prepared using various barrier preparation conditions. The energy of the sputtered MgO particles arriving at the substrate was found to be the most important parameter. Tunnel junctions (10*10 mu m2) with Vm values of up to 23 mV have been fabricated. The optimized NbN/MgO/NbN junction process is extended to a reliable whole-wafer process for DC SQUID fabrication.

A modular low-noise seven-channel SQUID-magnetometer for biomagnetic measurements was developed. The DC-SQUIDs are prepared by thin film technology based on the materials NbN-MgO-NbN, and show a flux noise below 10 mu Phi /sub 0// square root Hz. The signal is picked up with first-order wire-wound gradiometers of 2-cm diameter and coupled to the SQUIDs by integrated coupling coils. Individual channels can be replaced from the system, and various gradiometers can be used giving a flexible modular system. The electronics are based on the flux-locked-loop method extended by a bias modulation technique to reduce 1/f noise. The overall system noise is below 20 fT/ square root Hz. Biomagnetic measurements on auditory evoked fields have been carried out.

The noise of two integrated YBa2Cu3O7-SrTiO3-YBa2Cu3O7 multilayer magnetometers in static magnetic fields up to 110 μT is investigated: An inductively coupled magnetometer with integrated flux transformer and a multiloop magnetometer. In both samples, only a moderate increase of the low frequency flux noise is found in high fields, due to the high epitaxial quality of the involved multilayer films. So for moderately shielded or unshielded applications in the earth’s magnetic field, high-quality integrated YBa2Cu3O7 magnetometers can be operated with low excess noise.

We report on new magnetization studies on a two-dimensional electron system (2DES) revealing spin splitting of the Landau levels. For this, we have built a high-sensitive susceptometer consisting of a low-noise thin-film dc superconducting quantum interference device (SQUID) with a multiturn input coil and a wire-wound first-order gradiometer. The system noise level is only 40×10 −6 Φ 0 /√ (Hz) down to a frequency of a few Hz in unshielded environment. In background fields up to 10 T, the system exhibits significant low-frequency noise. At frequencies above 1 kHz, however, the SQUID sensitivity is barely affected and we have reached a value of about 10 −14 J/T at 1 T and better than 10 −13 J/T at 10 T. With this, we have studied the de Haas–van Alphen effect for a tunable 2DES starting from zero carrier density.

We used the Monte Carlo code EGSnrc to simulate electron energy loss profiles as well as angle resolved x-ray spectra for metal-layer/substrate combinations in the primary electron energy range of 60-160 keV. We were furthermore able to separate the bremsstrahlung fraction originating in the substrate from that of the metal layer. The simulations were accompanied by experimental investigations. High-energetic electrons of 60-160 keV were directed onto 1-2 μm thin tungsten layers on top of 500 μm diamond substrates. The spectra were recorded by an energy resolved detector positioned in backward direction. We compared the experimental data with the simulation results and found good agreement. An enhanced monochromaticity in backward direction however, as expected from thin film theory, has not been observed due to the influence of the substrate.

Three magnetometers based on dc superconducting quantum interference devices (SQUIDs) fabricated from YBa2Cu3O7−x have been operated in a magnetically shielded room using a flux‐locked loop involving additional positive feedback with bias current reversal. Two of these devices, integrated multiloop dc SQUIDs with outer diameters of 7 mm, achieved white noise levels of 10 fT/√Hz for bicrystal junctions and 30 fT/√Hz for step‐edge junctions. The third magnetometer involved a flux transformer with a 10×10 mm2 pickup coil connected to a 16‐turn input coil which was inductively coupled to a bicrystal SQUID. This device achieved a white noise of 16.2 fT/√Hz. High quality magnetocardiograms were obtained without signal averaging.

This paper presents simulated and measured spectra of a novel type of x-ray tube. The bremsstrahlung generating principle of this tube is based on the interaction of high energetic electrons with a turbulently flowing liquid metal separated from the vacuum by a thin window. We simulated the interaction of 50-150 keV electrons with liquid metal targets composed of the elements Ga, In, Sn, as well as the solid elements C, W and Re used for the electron windows. We obtained x-ray spectra and energy loss curves for various liquid metal/window combinations and thicknesses of the window material. In terms of optimum heat transport a thin diamond window in combination with the liquid metal GaInSn is the best suited system. If photon flux is the optimization criteria, thin tungsten/rhenium windows cooled by GaInSn should be preferred.

A novel type of electron-impact x-ray source based on the interaction of energetic electrons with a turbulently flowing liquid metal target is presented. The electrons enter the liquid through a thin (several microns thick) window, separating the liquid from the vacuum region in which the cathode is situated. Several electron window materials including diamond, tungsten and molybdenum were tested in combination with the liquid metal GaInSn. Satisfactory agreement has been obtained between the predictions of thermal transport models and the measured dependence of the loadability on fluid velocity. The liquid metal technology appears to represent a significant improvement in continuous loadability relative to stationary anode x-ray tubes.

We have fabricated ramp‐type Josephson junctions and SQUIDs (superconducting quantum interference devices) using an ultrathin barrier layer of NdGaO3 as weak contact between the YBa2Cu3O7 electrodes. The junctions operate up to 82 K, exhibiting current‐voltage characteristics of the resistively‐shunted‐junction type. A normal‐state resistance of up to 30 Ω at a junction width of 5 μm and a characteristic voltage in excess of 100 μV at 77 K are obtained. We find hysteretic behavior below 70 K and an intrinsic junction capacitance of about 0.15 μF/cm2 at 4 K. SQUIDs show a transfer function δ V/δ Φ of 50 μV/Φ0 at an inductance of 40 pH at 77 K. Thus we observe excellent Josephson properties at a thickness of the NdGaO3 barrier of 2 nm.

We have designed and fabricated a thin‐film flux transformer by a YBa2Cu3O7/SrTiO3 (YBCO/STO) multilayer process. The flux transformer consists of a 20‐turn input coil of 10 μm linewidth and a single‐turn pickup loop surrounding an area of 7.5 by 7.5 mm2. All device levels are patterned by standard photolithography and Ar‐ion‐beam etching. The flux transformer has been combined in flip‐chip configuration with the square washer of a low‐noise YBCO dc SQUID. The dc SQUID magnetometer exhibits a magnetic field sensitivity of 1.4 nT/Φ0. The intrinsic white flux noise level of 70μΦ0/√Hz at 77 K is mainly dominated by the SQUID corresponding to a magnetic field resolution of the magnetometer of 100 fT/√Hz for frequencies above 40 Hz. At 1 Hz we measured 200 fT/√Hz. Biomagnetic measurements were performed in a magnetically shielded chamber.

We have fabricated Y1Ba2Cu3O7−x step‐edge junction dc superconducting quantum interference devices (SQUIDs) and characterized their noise performance. The current‐voltage characteristics of our SQUIDs are of resistively shunted junction type with critical current densities jc of about 104 A/cm2 and maximum flux to voltage transfer functions δV/δΦ of 20 μV/Φ0 at 77 K. We compare model predictions for 1/f noise in dc SQUIDs with experimental data and show that the frequency dependent noise in our devices results from critical current fluctuations of the Josephson junctions. A bias current reversing technique is effective in suppressing this noise contribution. A flux noise Φn of 80 μΦ0/Hz1/2 at 1 Hz and 77 K was measured on a dc SQUID with an inductance Ls of 60 pH.

DC-SQUIDs made of refractive materials NbN-MgO-NbN were prepared using thin film preparation techniques. The noise properties of these SQUIDs were investigated. The white energy sensitivity of typical devices is 600h (8mF0/ÀHz). The measured values are compared with theoretical predictions and the standard optimization rules. The low frequency noise was measured directly and using different modulation schemes. The SQUIDs show a relatively high 1/f noise onset in the range of 100Hz. The main contribution comes from out-of-phase critical current fluctuations and can be effectively suppressed by bias modulation.

A low noise 19-channel SQUID system was developed. It is part of a complete system for functional diagnosis of human brain or heart.

A 19-channel SQUID system for biomagnetic measurements has been developed. This system differs from standard instruments in its modular approach. Various gradiometers can be coupled to the SQUIDs, the cryogenic system allows the exchange of single channels and the electronics is based on a cassette system. Problems with thermal insulation, vibrations of the gradiometers and tilted gradiometer geometries are discussed and solutions are presented.

The small signal rf impedance of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-/spl delta// step edge junction rf SQUIDs operating in a strongly nonhysteretic mode has been measured. The phase dependent inductance L/sub J/(/spl phi/) and the current phase relation I/sub p/(/spl phi/) of step-edge junctions embedded in SQUIDs are calculated from measurement data following the Vincent-Deaver approach. Two of three junctions investigated revealed a sinusoidal current phase relation. I/sub p/(/spl phi/) of the third junction seemed to be non-sinusoidal and hysteretic. A model explaining the origin of the non-sinusoidality of I/sub p/(/spl phi/) is proposed. >

A multi-layer technology, based on YBaCuO as the superconducting material and SrTiO3 as the insulating material, is described. Patterning is performed by photolithography and Ar-ion-beam etching under fiat incidence. Using a resist bake-out prior to the etching, step angles in the patterned lower film of less than 20 degrees are obtained. Superconducting 10-turn thin-film coils have been fabricated with transition temperatures of up to 83 K and critical current densities at 77 K of 2*105 A cm-2. Furthermore we have fabricated a thin-film flux transformer and combined it in flip-chip configuration with a low-noise YBCO step-edge DC SQUID. We measured a magnetic field resolution of the complete magnetometer of 200 fT Hz-1/2 at 1 Hz, dominated by the SQUID noise itself.