4644281 Coil arrangement for producing a homogeneous magnetic field

VII

New Patents frequency of the Fourier spectrum of the FID signal, i.e., the Larmor frequency. The primary magnetic field is controlled or the observed data is corrected, according to the measured value of the primary magnetic field intensity.

4644280 MAGNETIC

Zvi Paltiel, Ltd

RESONANCE ZOOMING

Rehovot,

Israel

assigned

IMAGE

to Elscint

A slice selection arrangement for MRI systems uses a psuedo-spin echo procedure by applying a 90 degree RF pulse in the presence of gradient pulse, applied in the direction of the encoding pulses; applying the 180 degree RF pulse in the presence of a gradient in another orthogonal direction and reading out the echo in the presence of the third orthogonal gradient pulse. Aliasing artifacts are avoided even though the section imaged is smaller than the object size, allowing zooming and/or a reduced number of encoding cycles for single slice imaging.

4644281 COIL ARRANGEMENT FOR PRODUCING A HOMOGENEOUS MAGNETIC FIELD Matti Savelainen, Espoo, Instrumentation Corp

Finland

distance (Z 1) from the center point of the outermost solenoids (2) to the center point of the middlemost solenoid (1) is 1.80 . . . 1.95, preferably 1.858 . . 1.868 times the mean radius (rl) of the middlemost solenoid (1) and the electric current density of the middlemost solenoid (1) per unit length in the direction of the axial winding width is 0.250.. .0.275, preferably 0.2646. . . 0.2666 times the electric current density of the outermost solenoids (2) measured in a corresponding manner.

assigned

to

The invention relates to a coil arrangement for producing a homogeneous magnetic field especially for application to so-called NMRimaging. An object of the invention is in terms of the size of a coil arrangement to expand the homogeneous area produced by a coil arrangement and, at the same time, to maintain the design of a coil arrangement simple and its manufacturing costs low. According to the invention, a coil arrangement includes three solenoids having a common axis, of which the axial winding width (Wl) of the middlemost solenoid (1) is 2.75 . . 2.95, preferably 2.835 . . . 2.855 times the mean radius (rl) of the middlemost solenoid (1) and the mean radius (r2) of the outermost solenoids (2) is 1.05 . . . 1.07, preferably 1.055 . . . 1.06 1 times the mean radius (r 1) of the middlemost solenoid (1) and the axial winding width (W2) thereof is 0.32 . . . 0.38, preferably 0.340. . _0.342 times the mean radius (rl) of the middlemost solenoid (1). In addition, the

4644282 APPARATUS FOR THE FORMATION OF IMAGES OF AN EXAMINATION SUBJECT WITH NUCLEAR MAGNETIC RESONANCE Joachim Kestler, Pretzfeld, Federal Republic Of Germany assigned to Siemens Aktiengesellschaft Magnetic fields are applied to the examination subject, and the deflection of the atomic nuclei of the examination subject from their state of equilibrium by means of a high frequency magnetic excitation pulse is detected. There is at least one gradient coil for the purpose of generating a linear magnetic field gradient. The gradient coil is connected, in series with an additional inductance, to a current source. Connected in series with the gradient coil is a first switch. Connected in parallel with the series of connection of gradient coil and first switch is a second switch actuatable to open condition approximately simultaneously with the closure of the first switch.

4644313 CYLINDRICAL MAGNET APPARATUS Go Miyajima, Hitachi Ltd

Katsuta,

Japan

assigned

to

A cylindrical permanent magnet apparatus and electromagnet apparatus used with a nuclear magnetic resonance imaging system are disclosed, in which a magnetic path of ferromagnetic material is arranged around a predetermined Z axis, magnetic field source are arranged at the ends of the magnetic path, a cylindrical magnetic flux conductor is interposed between the magnetic field sources, and an ob-