Abstract: A gradient coil system for a magnetic resonance imaging apparatus is described which has a capability of high-speed switching and high intensity for a certain pulse sequence, for example, a rapid imaging or an angiographic imaging. The gradient coil system comprises multiple coil elements which reduce a load of a gradient amplifier. Each of the coil patterns of the coil elements is formed on an individual substrate and the coil elements are radially superposed. This enables each coil turn to be wide and thin.

Abstract: A method for the production of a two or three-dimensional image with the assistance of magnetic resonance. The measuring data are taken according to the projection method by means of a sequential rotation of projection gradients. The image, however, is generated with 2dFT or 3dFT methods. The projection gradient is advantageously not only rotated between high frequency excitation pulses, but its strength is also changed in such fashion that the measuring points in k-space lie on squares or parallelepipeds.

Abstract: The instruments of a pulsed nuclear magnetic resonance (NMR) device are included in a drill collar for evaluating earth formations. The resulting tool makes NMR measurements while the formation is being drilled.

Abstract: In a turbo-spin echo sequence, nuclear magnetic resonance signals lying chronologically closer to an excitation phase are entered into a first raw data matrix for the acquisition of a proton-density-weighted image and nuclear magnetic resonance signals lying farther from the excitation phase are entered into a second raw data matrix for the acquisition of a T2-weighted image. Fewer rows are acquired for the first raw data matrix after every excitation phase than are acquired for the second raw data matrix. This avoids nuclear magnetic resonance signals that are already relatively strongly T2-weighted from being employed for the acquisition of a proton-density-weighted image.

Abstract: A high-conductivity ceramic coil form with an internal water jacket is used to simplify water cooling for 3-axis MRI gradient coil configurations on a single cylindrical coilform. Crescent-shaped, axially aligned coils are symmetrically employed on either side of the axial symmetry plane to increase transversely the region of field linearity. These crescent coils may be used in conjunction with Golay-type coils for improved switching efficiency. Lead-filled copper tubing may be used to reduce acoustic noise from pulsed coils in high external magnetic fields.

Abstract: Magnetic resonance imaging includes a system of gradient coils (3) for generating gradient fields in a measuring space (35), a power supply source (7) for the gradient coils, and a communication system for transferring acoustic information from at least a first region (39) in which the level of gradient noise generated by the gradient coils (3) is comparatively high to at least a second region (41). The communication system includes a reference signal generating device for generating a reference signal which is dependent on the gradient noise, a microphone (43) which is arranged in the first region (39) so as to pick up a mixture of sound information and gradient noise, and a sound reproduction device (65, 67), at least a part of which is situated in the second region (41).

Abstract: An RF probe including: two coils for detecting MR signals which are arranged at positions which face each other at a predetermined distance; an apparatus for changing a distance between those coils; and an apparatus for reducing a high frequency coupling between the two coils which is caused due to a change in distance between the coils, in accordance with the distance between the coils.

Abstract: In a diagnostic magnetic resonance apparatus having a housing in which a patient is disposed for conducting a magnetic resonance examination, a cable is provided for connecting the antenna which receives the high-frequency magnetic resonance signals and forwards those signals to the processing electronics. One end of the cable is guided into the housing which surrounds the patient, and an opposite end of the cable is connected to the antenna by a plug-type connector. A part of the plug-type connector at the cable side contains at least one pre-amplifier for amplifying the received magnetic resonance signals.

Abstract: An apparatus for detecting a misfire in an internal combustion engine that is capable of preventing erroneous detection in a period in which the discharged voltage on a secondary ignition coil is charged. The apparatus having a capacitor, which is supplied with bias voltage from a primary side of an ignition coil to be electrically charged to apply the charged voltage to the spark plug at the time of discharge of the spark plug to cause an ionic current to flow and a misfire detection circuit for determining whether or not a misfire has taken place in accordance with detection of the ionic current flowing from the capacitor.

Abstract: A missing phase detector circuit which monitors the ac three-phase output voltages of power equipment or sources and produces an output signal in the event a missing ac phase is detected. The circuit reduces the monitored phase voltages to low values and produces an ac ripple voltage waveform where each ripple represents a phase. An analyzer circuit examines the ac ripple voltage waveform for its zero crossings and produces a pulsed dc waveform where the width of the pulses is normally small. If any of the pulses is found to be wide, indicating a missing phase, a positive high signal is output by an AND gate. This output signal may be used to initiate illumination of a "Missing Phase" indicator or it may be used for equipment control purposes. Provision is made to prevent a false output signal when there is no input power. The circuit is not sensitive to frequency, power factor or unbalanced loads.

Abstract: A calibration procedure for correcting geometric errors in MRI images due to gradient field non-linearities and magnetic field inhomogeneities includes performing a 3D scan on a calibration phantom. The calibration phantom contains an array of tapered rods that produce an array of spots in reconstructed slice images. Spot sizes and positions enable position errors to be measured throughout the bore of the imaging system. Corrective coefficients are produced from these 3D error measurements that enable subsequent patient images to be corrected for warping errors in object position.

Abstract: An object is repeatedly excited by a 90-degree pulse and a plurality of spin echoes are obtained by a 180-degree pulse each time the excitation is repeated. The spin echoes are differently phase-encoded and the spin echoes thus generated are assigned to a substantial half portion of a raw image data space in a phase-encoding direction, the remaining substantial half of data being estimated from the data in that portion. The data covering the raw image data space are used to produce a corresponding image of the object.

Abstract: In a steady-state pulse sequence having a repetition time and a flip angle .alpha. with alternating polarity for operating a magnetic resonance imaging apparatus, the excursion of the magnetization in the steady-state condition moves between a first value +.alpha./2 and a second value -.alpha./2. Before the beginning of the pulse sequence, a radiofrequency pulse having a flip angle .alpha./2 is emitted before the first excitation pulse. The steady-state condition is thus reached earlier and a spin preparation can be implemented which is still effective when imaging data are acquired.

Abstract: An improved rapid acquisition relaxation enhanced (RARE) imaging method for measuring nuclear magnetic resonance in selected regions of a body is disclosed. The improved RARE imaging method includes introducing an evolution phase of time duration t.sub.2 between the excitation pulse and the first refocusing pulse of the multi-echo train. The evolution phase is introduced to influence the magnetization of the observed nuclei in such a fashion that the intensity and/or phase of the subsequent signals are influenced as a function of this evolution phase. This allows the effects of flow, motion, diffusion and local magnetic field inhomogenities to be measured.

Abstract: A method and apparatus for eliminating baseline error artifacts in NMR images produced using ultrafast pulse sequences including alternating the phase of a reference signal during the reception of NMR echo signals to invert alternate views in the acquisition. The inverted views are re-inverted prior to image reconstruction such that any dc levels introduced during acquisition are converted to a high spacial frequency which moves the resulting artifacts to the borders of the image reconstructed using a Fourier transformation.

Abstract: An NMR image data set is acquired along with interleaved navigator signals. The navigator signals are acquired while two, orthogonal readout gradients are applied such that a circular orbit in k-space is sampled. The navigator signals are analyzed to detect object motion and to produce corrective values for the NMR image data to reduce artifacts caused by object rotation and displacement along two axes.

Abstract: A nuclear magnetic resonance cross polarization probe uses a dual-coil arrangement in which a single-turn inner coil is surrounded by a solenoid coil. The inner coil is tuned to the frequency of a relatively high Larmor frequency nuclei type, such as proton. The solenoid coil is tuned to a lower Larmor frequency nuclei type. An inner sample region surrounded by the inner coil has a first magnetic field component induced by an electrical signal at the relatively high frequency in the inner coil. An electrical signal at the lower frequency is input to the solenoid coil and results in the generation of a magnetic field alternating at the lower frequency. This field induces a current in the inner coil at the lower frequency that, in turn, induces a magnetic field component in the inner region at the lower frequency.

Abstract: In an apparatus and method for magnetic resonance imaging, an imaging field (B.sub.p) and a pre-polarization field (B.sub.p) are generated by means of electromagnetic coils ALC in an air gap between pole pieces of a magnet core. The pole pieces are designed such that, as the current in the coils is increased, the field strength increases only in the central area between pole pieces up to the strength (B.sub.p) of the pre-polarization field. This is due to the saturation of the edge zones of pole pieces that restricts the increase of field strength in the edge zones of the air gap.

Abstract: Nuclear or electron spin magnetic resonance method using multiple radial scans through frequency-space. The problem of insufficient sample density at the higher image frequencies is solved by deriving an edge image, determining a correction image therefrom by using a priori knowledge about the pixel value distribution and using the correction image after Fourier transformation to frequency-space.

Abstract: A sample changer for a spectrometer of the type having a generally vertical sample loading air shaft in which an upflowing air stream is present. The sample changer includes a support for positioning at the spectrometer and a carriage movably supported by the support which carriage has an array of generally vertical passages extending entirely through the carriage, those passages being adapted to contain sample holders. The sample changer also includes an actuator for moving the carriage relative to the support to position each passage over the air shaft so that that passage becomes an extension of the air shaft whereby the sample holder in that shaft may be buoyed up and supported in its passage by the air stream from the airshaft.