Abstract: A method of nuclear magnetic resonance imaging of a body in which the spins of a chosen nucleus in a selected slice of the body are rotated through an angle appreciably greater than 90.degree.. Two r.f. pulses, each accompanied by a magnetic field having a gradient in a direction parallel to the equilibrium axis of magnetic alignment of the spins are applied in sequence. Each r.f. pulse is at the Larmor frequency for the nuclei in the slice in the presence of the associated field gradient and each r.f. pulse is effective to rotate the spins by not greater than 90.degree.. The r.f. pulses together are sufficient to rotate the spins through the desired angle, the gradients of the magnetic fields being in opposite directions.

Abstract: A method of exciting nuclear magnetic resonance at a particular location of a body comprises: exciting first nuclear spins in the body (A, Gx, -G'x, B, Gxd, C, Gy, -G'y, D) so that spins occurring in a first selected region of the body have their spin vectors lying in a first direction and any spins occurring elsewhere in the body have their spin vectors lying in a plane normal to the first direction; dephasing the spins in the body whose vectors lie in said plane (Gyd); and exciting nuclear spins in a second selected region of the body (E, Gz, -G'z) which intersects said first region at said particular location so that the vectors of the resultant spins in said particular location only are aligned in said plane.The method finds particular application in providing data for chemical analysis of material at a particular location of a body.Apparatus for carrying out the method is also described.

Abstract: A multi-slice method of NMR imaging wherein a number of discrete slices S.sub.1, S.sub.2, S.sub.3, S.sub.4 are excited simultaneously by using the usual field gradient Gz but an r.f. pulse B.sub.1 which is a mix of a number of pulses of different discrete frequencies, f.sub.1, f.sub.2, f.sub.3, f.sub.4, and recovering data in the presence of an alternating gradient G.sub.2 z in the same direction as used to establish the slices such that discrete spin echo signals of different frequency occur for each slice. Apparatus for use in the method is also disclosed.

Abstract: A nuclear magnetic resonance imaging apparatus associated with heat treatment means (45) and arranged to examine material subjected to heat treatment. The heat treatment means may be automatically controlled in dependence on any output produced by the imaging means, and/or manually controlled by an operator viewing a visual display (33) produced by the imaging means. The heat treatment means may be hyperthermia treatment means for treating diseased tissue of a patient.

Abstract: A method and apparatus for determining the spatial distribution of the chemical shift spectra of a chosen element across a region of a body. Where the region is a slice, nuclear magnetic resonance for the element is excited preferentially in the slice. First and second pulsed magnetic gradient fields (Gx, Gy) having magnetic field gradients in first and second mutually orthogonal directions in the plane of the slice are applied. The value of the gradient of the first field is stepped through a range of first values, for each of the first values the gradient of the second field being stepped through a range of second values.

Abstract: A magnet pole piece for an NMR imaging magnet is made of a plurality of magnetic wires (3) with one end of each wire held in a non-magnetic spacer (1), the other ends of the wires being brought to a pinch (5), and connected to a magnetic core (6). The wires are embedded in a synthetic resin (4) and the magnetization and uniformity thereof can be varied by adjusting the density of the wires at the spacer which forms the pole piece.

Abstract: A nuclear magnetic resonance imaging apparatus for medical use wherein a patient to be examined is positioned on support means (1) in a sitting posture and the required magnets (7, 11) and RF coils (13, 15) are arranged so as to allow easy movement of the patient into and out of the apparatus.

Abstract: A signal generator for generating signals to control a plurality of devices includes a digital computer and a control interface apparatus. The plurality of devices to be controlled is connected in use to the control interface apparatus. The computer has peripheral device select lines, output control lines, and a data output bus. The control interface apparatus is connected to one of the peripheral device select lines, and while it is enabled by that select line it decodes a device address on the data output bus under the control of one of the output control lines so as to select one of the plurality of devices connected to the interface apparatus, the number of the plurality of devices connected to the interface apparatus thus being limited only by the capacity of the data output bus.

Abstract: A method and apparatus for determining the rate of flow of a liquid in a selected region of a body by nuclear magnetic resonance techniques. The method includes a sequence of applying a first magnetic pulse (B.sub.1 (90.degree.)) effective to excite nuclear magnetic resonance of a chosen nucleus within the liquid preferentially in a slice of the body which includes the selected region. A period of time (t.sub.D) is waited and then a second magnetic pulse (B.sub.1 (90.degree.)) is applied which is effective to excite nuclear magnetic resonance of the nuclei preferentially in the slice, and the free induction decay signal is measured. The whole sequence is repeated for different values of the period of time (t.sub.D). The values of the period of time (t.sub.D) and the corresponding measured signals are then related to the rate of flow of the liquid through the slice.

Abstract: Method and apparatus for producing an N.M.R. picture of a plane through an object by isolating the plane using an oscillating gradient and interrogating the plane using a rotating gradient and a multiplicity of R.F. pulses which are averaged over a defined period to produce an average response which is used to produce the N.M.R. picture.

Abstract: A method of imaging a body by nuclear magnetic resonance wherein volume scanning of a region of the body is achieved by scanning a first planar slice of the region and at least one further slice of the region in the relaxation time for the scan of the first slice.

Abstract: An apparatus for holding x-ray cassettes and grids in which any grid of a specific length and width can be combined with any cassette of a corresponding length and width without regard to the cassette thickness. The apparatus includes a frame assembly having side rails with flanges and a back rail with flanges which form two channels, one for the grid and one for the cassette. The cassette channel is dimensioned to accept any thickness of cassette. Parabolic springs are located within side rail cassette channel portions to bias the cassette against selected flanges. Locater members are also provided to properly align the grid and the cassette.

Abstract: A method of examining a slice of a body by nuclear magnetic resonance in which a steady magnetic field, and a gradient field G.sub.z along the same axis define the slice to be examined. A periodic magnetic field H.sub.1 at the Larmor frequency for the slice is applied in two distinct pulses 1, 2 each in conjunction with the gradient field. The total field integral of the two pulses is chosen to be sufficient to rotate spin vectors of nuclei in the field through an angle of .pi./2 radians. Between the two pulses 1, 2, a further pulse 3 is applied in the absence of the gradient field G.sub.z, which has a field integral sufficient to rotate the spin vectors through an angle of .pi. radians.

Abstract: Nuclear magnetic resonance methods have been proposed for examination of large bodies, including medical examination of patients. These include so-called steady state free precession methods. Such methods involve alternating excitation of a region of the body in such a way that an equilibrium condition is established at which a mean resonance signal is detectable. Typically for excitation of a planar region a radio frequency excitation field is provided in the presence of a field having an alternating gradient so that equilibrium is only reached in the plane. It is now proposed to achieve the same result by the application of two radio frequency fields having opposing gradients and pulsed in alternation to balance substantially only in the plane and provide equilibrium only there. The fields are provided by respective sets of saddle shaped coils divided into pairs of unequal dimension (1a, 1b, 2a, 2b) to provide the respective gradients.

Abstract: In Nuclear Magnetic Resonance (NMR) imaging systems it is known to excite resonance in a slice of a body and to sample the resonance signals in the presence of a field gradient across the slice. The gradient field is pulsed. Where such systems analyse the signal to be for many sets of strips in the slice, each set in a different direction, for analysis by techniques used in computerized tomography (CT) X-ray systems, it is now proposed that the field gradient pulsed should reach a maximum after not more than one third of its total duration to balance the spatial frequency emphasis (FIG. 1e) in the CT processing.

Abstract: In nuclear magnetic resonance (NMR) imaging systems it is known to excite resonance in a slice of a body and then to sample the resonance signals in the presence of a field gradient across the slice. It has been proposed that the signals should be sampled at intervals such that there is equal field integral (for the field gradient) in each interval. It is now proposed to use outputs from two NMR probes in the slice and on opposite sides of the body. The phase difference between the two probes is measured and samples are taken when the phase difference reaches a predetermined value. Preferably the samples are taken when a gate detects zero-crossing of the output of a demodulator providing the phase difference. Two probes only may be rotated around the patient as the field gradient rotates or four may be used, two orthogonally disposed pairs and one or other appropriately weighted output used.

Abstract: In NMR imaging systems a pulsed field gradient may be applied across an excited slice (1) and the resonance signal detected during the field gradient pulse. It has been usual to demodulate the resonance signal at the Larmor frequency for a strip at the center of the slice, at which generally the field gradient has a zero-crossing. It has, however, been proposed to put the zero-crossing outside the slice, still demodulating at the slice Larmor frequency. In this invention demodulation is actually at the frequency for a probe (12) which is necessarily outside the patient. This makes the demodulation independent of errors in a local oscillator frequency. Demodulation may be for a probe effect to give a frequency for a strip outside the slice or the probe may be perpendicular to the gradient to give the zero-crossing frequency.

Abstract: The invention concerns the production of gradient fields for nuclear magnetic resonance apparatus particularly imaging apparatus. It has been earlier proposed that samples of the resonance signal be taken at intervals such that the field gradient integrals in each such interval are the same. This sampling is at unequal time intervals. It is now proposed to provide the gradient fields in discrete pulses with spaces in between at which samples can be taken. It is then straightforward to make the pulses of equal field integral or to provide an extra small pulse in one or both of the orthogonal gradients if the field integral should need adjusting before the next sample.

Abstract: The invention is suitable for a small nuclear magnetic resonance pulse head applicable to a part of the body in the manner of ultrasonic systems. The arrangement generates a field which varies in amplitude with distance from the head, being uniform at surfaces which intrude into the body. Resonance is excited in one such surface and a gradient restricts resonance to one line therein. The phase is then dispersed along the line and the signal sensed as a function of position therealong.

Abstract: A serial radiograph system has an improved film changer featuring reusable film pack containers. An exposure station through which X-rays are directed is virtually free of X-ray absorbing material providing a "see through" station. As a consequence of the "see through" exposure station, an image intensification tube positioned under the exposure station provides an unobstructed fluoroscopic image with minimum X-ray dosage to a patient.The film changer utilizes film packs, each of which has a semienclosed, partially sealed, pouch. Each pouch contains a sheet of radiographic film between a pair of intensifying screens. A plurality of the film packs are stacked in a novel supply magazine and are sequentially transported to the exposure station by a transport system having a plurality of pinch roll pairs.