Siemens Gammasonics, Inc.

Siemens Medical Systems, Inc.

Dennis E Persyk

Everett W Stoub

Raymond P DeVito

Albrecht H Enders

Ivan Jazbec

Keith A Ritter

Hamill James J

William White

A photomultiplier uses an avalanche photodiode as a position-sensitive anode. The envelope of the photomultiplier has a flat input end. Electrically conductive regions mounted to the input end are configured to produce at the input end a potential distribution characteristic of a photomultiplier with a spherical-type input end as measured in a transverse plane immediately adjacent the spherical-type input end. A photocathode is located inside the photomultiplier and is electrically connected to the electrically conductivew regions. Advantageously, the envelope has flat sides and a square cross-section; in this instance, conductors are run along the sides to produce within the envelope a potential distribution characteristic of a photomultiplier which is cylindrical in cross-section, as measured at flat surfaces having the same shape as the envelope.

Photomultiplier tube with an avalanche photodiode, a flat input end and

Light emitting diodes (LEDs) at fixed locations are placed at the entrance face of the scintillator within the detector head of a scintillation camera system. By energizing the LEDs, surrogate scintillation events may be generated and processed by the scintillation camera system. Information thus acquired can be used to maintain the photodetectors in a well-tuned state, to identify baseline shifts in the preamplifier channels and to determine system deadtime.

Method and apparatus for producing and utilizing flashes of light which

A scintillation crystal module of the type having a crystal housed in a backcap which is closed off by a glass window and sealed by an internal seal located between the window and the backcap is modified to include an external seal. The external seal is of moisture-impervious material and is attached to the outer surface of the backcap and the window and bridges over the boundary therebetween. The external seal may be made of an epoxy polyamid or a blocked urethane epoxy copolymer. The outer surface of the module may be sandblasted before the external seal is attached to the module, as by casting the adhesive in a suitable mold.

Improved seal scintillation camera module and method of making it

Photomultiplier tubes are bonded using silicone gel, which cures to a soft state. Small glass or plastic spheres are placed in the gel before it has cured so as to weaken it and make it easier to shear when the photomultiplier tubes are twisted or tipped. The resulting bond is mechanically and optically adequate but not so strong as to make it impossible to remove a photomultiplier tube which must be replaced.

Frangible bonding of photomultiplier tubes for use in scintillation

A detector module for use in scintillation cameras utilizes a plurality of elongated scintillator strips. A temperature gradient is established along the length of each strip. By identifying the particular strip in which a scintillation event has taken place and by measuring the decay time of the scintillation event, two-dimensional information can be developed. This permits a scintillation camera detector to be modularized and largely eliminates the problems of edge packing.

Detector module for scintillation cameras

A scintillation crystal is heated. A temperature gradient is established across a scintillation crystal inside a scintillation camera system. The decay time of a scintillation flash is related to the temperature of the site at which the corresponding scintillation event takes place. By monitoring the decay time of detected scintillation flashes, as by differentiation, the depth of the scintillation event within the scintillation crystal is determined, thereby leading to improved spatial resolution and improved energy resolution.

Heated scintillator

A thick layer of CsI(Na) is heated to or slightly below its melting point. The CsI(Na) is held at that temperature for 7 to 10 hours and is cooled to room temperature, preferably in two steps. The resulting scintillation crystal is translucent or transparent.

Scintillation crystal and method of making it

A scintillation crystal is provided for a radiation detector, which comprises a first layer of a crystal material having relatively poor mechanical properties, however having a high energy resolution; and a second layer of a crystal material having relatively good mechanical and optical properties. Both layers are arranged in sandwich form.

Scintillation crystal for a radiation detector

A dynodes arrangement for an electron multiplier. It comprises a first dynode having a first voltage input; a second dynode having a second voltage input; and a control grid positioned between the first and second dynodes and having a control voltage input separate from the first and second voltage inputs of the first and second dynodes.

Dynodes arrangement for an electron multiplier

An imaging dynodes arrangement for an electron multiplier, which comprises a first and a second imaging dynodes having dynode cones with a cone tip and a cone base, said dynode cones being connected with each other such that they form free cavities therebetween. Furthermore, there are needle-shaped extraction points arranged at the cone tips of at least the dynode cones of the second imaging dynode. The second imaging dynode is mounted beneath the first imaging dynode in a staggered position such that the cone tips of the dynode cones of the second imaging dynode are seated beneath the cavities of the first imaging dynode, directing the needle-shaped extraction points closely to the cavities. In a preferred embodiment the needle-shaped extraction points protrude into the cavities.

Imaging dynodes arrangement

A radiation detector circuit, which comprises a radiation detector containing a scintillation crystal and a photomultiplier tube for real time photon measurement having a pulse output, and which also includes a plurality of pulse counters each having a pulse input and a count signal output. Between the pulse output of the photomultiplier tube and the pulse inputs of the pulse counters a time multiplexer is provided for connecting each pulse input of each counter in succeeding time periods with the pulse output of the photomultiplier tube. Furthermore, an evaluation circuit is connected with the count signal outputs of the counters for evaluating each count signal of each counter measured during each of said succeeding time periods in the sense of error estimates and trend analysis.

Radiation detector circuit with real time photon counting

A method and device for stabilizing photomultiplier tubes of a radiation image device against drift by illuminating the photomultiplier tubes with light. A certain number of the photomultiplier tubes are arranged in an array for final application. Then the complete array is illuminated for a certain time period with light having an intensity to produce an average anode current in the photomultiplier tubes which is in the range of 1 to 50 .mu.A.

Method and device for stabilizing photomultiplier tubes of a radiation

A method and device are provided for demounting in a radiation detector a photomultiplier tube the bottom of which is solely bonded with a scintillation crystal assembly by means of an elastic light transparent adhesive. A shearing tool is placed at the bond between photomultiplier tube and scintillation crystal assembly which is operated such that it shears the bond. Especially as a shearing tool a thread is placed around the bond such that it forms a noose. The thread ends have been wrapped around a rod. When twisting the rod the thread continues to wind around the rod thereby making the loop smaller and shearing the bond.

Method and device for demounting in a radiation detector a

The radiation detecting apparatus contains at least one photomultiplier tube for the detection of light. It has been found that the photomultiplier tube will emit erroneous output signals when exposed to a perturbing magnetic field. This is particularly true for photomultiplier tubes used in scintillation cameras and in emission computed tomography systems where the detector head containing photomultipliers changes position during operation. In order to reduce the magnetic field sensitivity, the radiation detection apparatus contains means for superimposing an artificial magnetic field on the perturbing magnetic field at the location of the photomultiplier tube. This artificial field may either be a compensating field or, preferably, an enhancing field which is larger than the perturbing field. The artificial field may be either generated by coils, such as Helmholtz coils, or by a permanent magnet. The coil(s) may be arranged inside or outside the camera head.

Radiation detecting apparatus with reduced magnetic field sensitivity

An attenuation zone plate for coded-aperture imaging of a radiation source has mercury contained within a wedge-shaped chamber in a plastic housing. Reservoir and relief cavities facilitate filling the housing with mercury and accommodate changes in mercury volume. Lead plates positioned on the perimeter of the housing provide a field of view mask. In one embodiment, the housing cover pivots to vary the wedge angle. Advantages include greater facility in precision manufacturing and greater attenuation pattern flexibility.

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Barrington, IL, United States of America

Dennis E Persyk