General Electric Company

Kai Lange

Ernest J Wiesen

Robert R Lijewski

Eric M Woronowicz

Jo slashedrn-Erik Jensen

Verner Toefting

Jorgen Jeppesen

To acquire tomographs, two detectors (,) are secured together in a support structure (,) in such a manner that their detection fields are inclined relative to each other. The angle of inclination between them is preferably 90&deg;. This pair of detectors is then placed in such a manner that the plane (,) bisecting the two detection fields includes the axis of rotation (,) around which the pair of detectors is to rotate to perform tomography on a subject. For fat subjects, the pair is moved away (,) from the axis, and for thin subjects it is moved towards it. It is shown that to avoid detector displacement interfering with tomography computation, it suffices merely to change computation parameters in the reconstruction algorithm.

Tomograph acquisition apparatus having a pair of rotatable scintillation detectors which form detection fields at an angle of inclination relative to each other

An apparatus for generating gamma transmission and gamma emission images simultaneously including two emission cameras disposed on opposite sides of an imaging area so as to oppose each other, a gamma line transmission source and a line detector positioned between the two emission cameras on opposite sides of the imaging area, at least one of the source or line detector being movable along a path that substantially traverses the distance between the two emission cameras. The two emission cameras, line source and line detector are all secured to the same gantry for rotation about the imaging area so that transmission and emission images can be generated simultaneously.

Imaging attenuation correction mechanism

In a gamma camera, to improve resolution, primary scintillations resulting from absorption of gamma ray photons in a scintillator crystal are intercepted by the input face of a channel amplifier plate in which the primary scintillations excite a photocathode to emit electrons which are multiplied in the respective channels and reconverted to secondary scintillations in a phosphorescent output screen from which the brighter secondary scintillations are coupled to an array of photodetectors which produce signals that are used to determine the x and y coordinates of the scintillations. The secondary scintillation positions correspond with the primary scintillations in the crystal because the channels keep them aligned.

Gamma ray camera using a channel amplifier

A supporting structure allows a conventional, counterbalanced scintillation camera to be adapted for emission tomography analysis by rotating a detector in a circular orbit about a patient. The structure includes a base having a pair of upright stanchions supporting an upright circular frame which has a central, longitudinal axis. The upright circular frame comprises an outer circular ring and a concentric inner circular ring adapted for concentric relative rotation. An elongated frame pivotally supports a detector at one end and has a counterweight at the other end is tiltably mounted within the inner circular ring of the circular frame. The structure includes a drive system for rotating the elongated frame within the circular frame whereby the detector orbits the patient to receive emission data.

Structure for emission tomography scintillation camera

In a gamma camera system, means are provided for correcting nonuniformity or lack of correspondence between the positions of scintillations and their calculated and displayed x-y coordinates. In an accumulation mode, pulse counts corresponding with scintillations in various areas of the radiation field are stored in memory locations corresponding with their locations in the radiation field. A uniform radiation source is presented to the detectors during the accumulation mode. When a predetermined maximum number of counts is reached in several memory locations, accumulation is interrupted at which time other locations have fewer counts in them. In the run mode, counts are stored in corresponding locations of a memory and these counts are compared continuously with those stored in the accumulation mode. Means are provided for injecting a number of counts during the run mode proportional to the difference between the counts accumulated during the accumulation mode in a given area increment and the counts that should have been obtained from a uniform source.

Gamma camera system with improved means for correcting nonuniformity

In a gamma camera system having an array of photomultiplier tubes for detecting scintillation events and preamplifiers connecting each tube to a weighting resistor matrix for determining the position coordinates of the events, means are provided for summing the signals from all photomultipliers to obtain the total energy of each event. In one embodiment, at least two different percentages of the summed voltage are developed and used to change the gain of the preamplifiers as a function of total energy when energies exceed specific levels to thereby obtain more accurate correspondence between the true coordinates of the event and its coordinates in a display.

Energy independent uniformity improvement for gamma camera systems

In a gamma camera system a computer calculates the x and y coordinates of scintillations and a pulse height analyzer determines if they are within the proper amplitude limits for being displayed on a cathode ray tube at corresponding coordinates. Means are provided for correcting nonuniformity or lack of correspondence between the positions of the scintillations and their calculated coordinates. In an accumulation mode, a first memory matrix stores pulse counts for incremental areas of the radiation field when a uniform source is presented to the detectors. When a predetermined maximum number of counts is reached in at least one memory location accumulation is interrupted at which time other locations have fewer counts in them. In the run mode counts are stored in corresponding locations in a second memory matrix and these counts are compared continuously with those in locations in the first memory. Means are provided for injecting a number of counts to make up for the difference between the counts for a given area increment and the counts that should have been obtained for a uniform source.

Scintillation camera system with improved means for correcting

In a scintillation camera system, the output pulse signals from an array of photomultiplier tubes are coupled to the inputs of individual preamplifiers. The preamplifier output signals are coupled to circuitry for computing the x and y coordinates of the scintillations. A cathode ray oscilloscope is used to form an image corresponding with the pattern in which radiation is emitted by a body. Means for improving the uniformity and resolution of the scintillations are provided. The means comprise biasing means coupled to the outputs of selected preamplifiers so that output signals below a predetermined amplitude are not suppressed and signals falling within increasing ranges of amplitudes are increasingly suppressed. In effect, the biasing means make the preamplifiers non-linear for selected signal levels.

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Vedbaek, Denmark

Kai Lange