Ohio Nuclear, Inc.

Technicare Corporation

Koninklijke Philips Corporation N.v.

Picker International, Inc.

Thomas R McBride

Joseph B Richey

John Covic

Wayne R Dannels

Robert H Wake

Russell A Compton

Arthur B Braden

Samuel K Taylor

David M Kramer

John T Keller

Donald J Styblo

Daniel T Trabbic

Robert H McCarthy

Leonard J Cikotte

A controlled power supply () drives a magnetic field gradient coil () of a magnetic resonance imaging apparatus (). A gradient amplifier () includes a plurality of switching power regulators () which are electrically connected in series. A bipolar circuit () receives power from the series connected switching power regulators () and delivers the power at a selected polarity to the gradient coil (). A control circuit () delivers phase staggered pulse width modulated control signals (A, B, C, D) to the switching power regulators ().

Precision gradient amplifier with multiple output voltage levels

A magnetic field gradient system includes a magnetic field gradient coil () and a magnetic field gradient amplifier () that operatively communicates with the magnetic field gradient coil (). A pre-emphasis digital circuit () receives a digital magnetic field gradient control signal and outputs pre-emphasis correction terms. The preemphasis digital circuit includes a delay circuit () that delays the digital magnetic field gradient control signal by a selected time interval to produce a delayed digital magnetic field gradient control signal. A plurality of digital filters () each have selected time constant and amplitude parameters. The digital filters () receive the delayed digital magnetic field gradient control signal and output the pre-emphasis correction terms. A parameter memory () stores at least the time constant and amplitude parameters of the digital filters ().

Digital magnetic resonance gradient pre-emphasis

A magnetic resonance imaging magnet, gradient coil, and RF coil assembly is controlled by a workstation (40). The workstation (40) includes an operator input (46, 48) and a display system (58) including a video monitor (44) for displaying human-readable images reconstructed from magnetic resonance data. A scan/reconstruction rack (50) includes a scan processor (60) which controls scan parameters and a reconstruction processor (64) and associated hardware for reconstructing received magnetic resonance signals into the image representation. A scan sequencer (52) includes a master microcode board (90) which controls the scan sequencer in accordance with instructions received from the scan processor (60). The scan processor loads a series of codes describing gradient and RF waveform profiles into memories (130) of each of a plurality of profile channels (100, 102, 104, 106, 110, 112, 114). Associated state machines (126) of each channel under control of a clock (138) step the pulse information from the memory (130) to respective output registers. The outputs from four of the channels for controlling the magnetic field gradients are connected to an obliquer (94) which processes the four outputs with a matrix to generate x, y, and z gradient components. The gradient components are connected through digitally controlled pre-emphasis circuits (150) to the gradient coils. The rest of the channels are connected to a frequency synthesizer (116) which provides frequency information for driving the radio frequency coil.

Magnetic resonance scan sequencer

In a magnetic resonance imaging system, the same reference signal is used for both radio frequency transmission and phase sensitive detection. The use of the same reference signal for both transmission and reception prevents phase unlock between the two events. However, this technique results in variation in the demodulated, frequency encoded information, which is corrected by digitally filtering the received signal information as a function of the demodulation frequency used.

Phase sensitive detection in multislice magnetic resonance imaging

A source of radiation irradiates an area of interest of a patient. An image intensifier receives the x-rays which have traversed the patient and provides an optical image of an x-ray shadowgraph through the examined area of the patient. A television camera converts the optical image into a video signal. A signal processor operates on the video signal by adding an offset signal to the gray scale signal and by logarithmically compressing the gray scale portion of the video signal. An automatic zero circuit is provided which readjusts the offset signal between each horizontal sweep of the television camera. The logarithmically compressed gray scale portion of the video signal and the synchronization portion are received by an image processor. The image processor digitally stores a mask image or shadowgraph of the patient before being injected with an x-ray opaque contrast agent. The image processor also stores in a post contrast image or shadowgraph of the same area of the patient after the patient has been injected with an x-ray opaque contrast agent. The image processor subtractively combines the mask image with the post contrast image to produce a difference image. A video monitor displays the difference image.

Radiographic apparatus and method with logarithmic video compression

The radiographic system includes an x-ray source for irradiating a patient with x-radiation. An image intensifier receives the x-radiation which has traversed the patient and produces an optical image of a radiation shadowgraph of the examined area of the patient. A television camera converts the optical image into a video signal. An image processor stores each frame of the video signal generated by the television camera as an electronic image of the optical image viewed on the image intensifier. Alternately, a plurality of frames from the television camera may be combined to produce a composite image. A bias light is provided adjacent the target of a television camera to illuminate the target before an optical image from the image intensifier is monitored by the television camera. This improves the linearity of the response of the television camera, particularly to low amplitude light intensities on the first few video frames generated by the camera.

Bias lighting in a radiographic apparatus and method

A CT scanner has an outer circular array of stationary radiation detectors for an inner concentrically revolving source of radiation emitted in a fan pattern subtending a number of the detectors. A number of analog signal processing channels equal to the maximum number of subtended detectors at any given time is automatically connected via switching circuitry to receive the outputs of only the detectors within the fan pattern.

Data channel multiplexing system for CT scanner with rotating source

An automatic variable collimator which controls the width and thickness of X-ray beams in X-ray diagnostic medical equipment, and which is particularly adapted for use with computerized axial tomographic scanners. A two-part collimator is provided which shapes an X-ray beam both prior to its entering an object subject to radiographic analysis and after the attenuated beam has passed through the object. Interposed between a source of radiation and the object subject to radiographic analysis is a first or source collimator. The source collimator causes the X-ray beam emitted by the source of radiation to be split into a plurality of generally rectangular shaped beams. Disposed within the source collimator is a movable aperture plate which may be used to selectively vary the thickness of the plurality of generally rectangular shaped beams transmitted through the source collimator. A second or receiver collimator is interposed between the object subject to radiographic analysis and a series of radiation detectors. The receiver collimator is disposed to receive the attenuated X-ray beams passing through the object subject to radiographic analysis. Located within the receiver collimator are a plurality of movable aperture plates adapted to be displaced relative to a plurality of fixed aperture plates for the purpose of varying the width and thickness of the attenuated X-ray beams transmitted through the object subject to radiographic analysis. The movable aperture plates of the source and receiver collimators are automatically controlled by circuitry which is provided to allow remote operation of the movable aperture plates.

Variable collimator

A versatile patient table system for transverse axial scanners employs front and rear tables with a spanning patient pallet for abdominal scans. A motorized conveyer belt on the front table increments the axial position of the patient. For brain scans the rear table and patient pallet are replaced by a head restraint assembly with a hinged headrest, check pad restraint members and a body pad which rests on the conveyer belt on the front table. In the automatic mode of operation, the belt moves either the body pad or the patient pallet out from the scanner in controlled increments triggered by the image processor. The hinged metal seam of the belt is used for indexing the extreme outward and inward positions.

Automatic patient table having means for transporting patient along a

Rotary safety shutter mechanisms for use in computerized tomographic X-ray scanners of the type wherein a source of radiation and a detector means are mounted for movement on opposite sides of a medium in order that the radiation passes through successive planar sections of medium and is attenuated and detected to give an output. The safety shutter mechanisms are arranged to be positioned adjacent the outlet aperture of the radiation source to selectively block the outlet upon occurrence of a predetermined condition. Two different embodiments of safety shutter mechanisms are disclosed. In each embodiment, the mechanism comprises a housing mounted adjacent the outlet aperture and having a through passage through which radiation from the source can pass. A cylindrical shutter member is carried in the housing transversely of the passage and mounted for rotary movement between a first position which permits the flow of radiation from the source and a second position which blocks the flow. In the first embodiment, the shutter member is moved from the second to the first position by a linear solenoid connected with the shutter member through a crank which is continually biased to move the shutter to the second position. In the second embodiment, the shutter member is actuated to the first position by a rotary solenoid aligned with the axis of rotation of the shutter member and directly coupled thereto.

Growing community of inventors

Newbury, OH, United States of America

Thomas R McBride