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4374419 Device for determining a radiation attenuation distribution in a plane of a body
memory locations for correction values is present, whose input is connected to the measuring channel output following the amplifier circuit and whose output is connected to the measuring channel input in front of the amplifier circuit. Each register supplies to the associated measuring channel input a correction signal having a value in dependence upon the measuring channel output signal during a preceding signal interruption and such as to correct for any zero point drift of the amplifier circuit.
and ions produced by interaction in that region. In a preferred embodiment, a conductive electrode is placed on the inner surface of the dielectric layer and maintained at anode potential to modify and stabilize the electric field behind the window and thus stabilize the detector characteristcs.
4376893
Toshitak Suwaki; Otaro Ando assigned to Olympus Optical Company Ltd
4375818 ULTRASONIC DIAGNOSIS SYSTEM ASSEMBLED INTO ENDOSCOPE
ION CHAMBER ARRAY WITH REDUCED DEAD SPACE Whetten Nathan R assigned to General Electric Company
An ionization chamber for use in determining the spatial distribution of x-ray photons in computerized tomography systems comprises a plurality of substantially parallel, planar anodes separated by parallel, planar cathodes and enclosed in a gas of high atomic weight at a pressure from approximately 10 atmospheres to approximately 50 atmospheres. X-ray radiation enters the chamber through a thin conductive window disposed substantially perpendicular to the anodes and cathodes. A dielectric layer disposed on the inner surface of the window accumulates charge during x-ray irradiation to modify the electric field in the region between the anodes, cathodes, and window so as to permit the collection of electrons
An ultrasonic diagnosis system includes an ultrasonic wave transmitting and receiving transducer which is rockably disposed within the distal end of a portion of an endoscope which is adapted to be inserted into a coeliac cavity. The transducer emits ultrasonic wave from within the coeliac cavity and directs it toward internal tissues of a physical body, thereby enabling an ultrasonic tomographic image to be obtained. The endoscope also includes an observation optical system which permits the location of the ultrasonic transducer within the coeliac cavity to be visually recognized.
4374419 DEVICE FOR DETERMINING A RADIATION ATTENUATION DISTRIBUTION IN A PLANE OF A BODY Peter W Lux assigned to U S Philips Corporation
xi
4371976
X-RAY APPARATUS FOR DETERMINING THE ABSORPTION DISTRIBUTION IN A FLAT EXAMINATION ZONE Wagner Wolfgang assigned to U S Philips Corporation
For the backprojection of the convoluted measurement signals in a Cartesian coordinate system in a computer tomography device, it is necessary to recalculate the weighting factors for each position of the source in order to determine the contribution of a convoluted measurement signal to the attenuation value associated with a given element of the output image matrix. This is a time consuming and hence expensive form of reconstruction, and can be avoided by storing all the weighting factors required; this, however, implies a very large memory, and is also expensive. The invention relates to the use of a matrix of elements organized in polar coordinates, which is stored in the memory, the origin central coordinate of said matrix coinciding with the center of rotation of the X-ray source about the object section. The weighting factors are also stored in a polar organized memory. The angular component of the address of the weighting factors is incremented with a rotational increment in the corresponding position of the X-ray source, so that for each group of measurement values, the same weighting factors can be used. The invention enables all the weighting factors to be stored in a memory of limited capacity, the more so because all weighting factors are mirror-symmetrical with respect to a central axis connecting the Xray source to the center of rotation, so that the angular coordinates of the memory need only extend from 0 to pi instead of from 0 to 2 pi.
The invention relates to a computer tomography apparatus for determining the absorption distribution in a relevant zone of a body, this zone being irradiated by unattenuated radiation, while the part of the body which is situated outside this zone is irradiated at the most by attenuated radiation. The radiation outside the relevant zone is attenuated in accordance with the invention by means of absorber pieces which are moved to and from during an examination in a direction parallel to the rotary shaft around which the Xray source is rotated. As a result, the intensity of the radiation is modulated in the time outside the zone, so that on average it is attenuated, without giving rise to hardening effects.
4368535 TOMOGRAPHY FOR PRODUCING TRANSVERSE LAYER IMAGES Baumann Hein assigned to Siemens Aktiengesellschaft
xii
and ions produced by interaction in that region. In a preferred embodiment, a conductive electrode is placed on the inner surface of the dielectric layer and maintained at anode potential to modify and stabilize the electric field behind the window and thus stabilize the detector characteristcs.
4376893
Toshitak Suwaki; Otaro Ando assigned to Olympus Optical Company Ltd
4375818 ULTRASONIC DIAGNOSIS SYSTEM ASSEMBLED INTO ENDOSCOPE
ION CHAMBER ARRAY WITH REDUCED DEAD SPACE Whetten Nathan R assigned to General Electric Company
An ionization chamber for use in determining the spatial distribution of x-ray photons in computerized tomography systems comprises a plurality of substantially parallel, planar anodes separated by parallel, planar cathodes and enclosed in a gas of high atomic weight at a pressure from approximately 10 atmospheres to approximately 50 atmospheres. X-ray radiation enters the chamber through a thin conductive window disposed substantially perpendicular to the anodes and cathodes. A dielectric layer disposed on the inner surface of the window accumulates charge during x-ray irradiation to modify the electric field in the region between the anodes, cathodes, and window so as to permit the collection of electrons
An ultrasonic diagnosis system includes an ultrasonic wave transmitting and receiving transducer which is rockably disposed within the distal end of a portion of an endoscope which is adapted to be inserted into a coeliac cavity. The transducer emits ultrasonic wave from within the coeliac cavity and directs it toward internal tissues of a physical body, thereby enabling an ultrasonic tomographic image to be obtained. The endoscope also includes an observation optical system which permits the location of the ultrasonic transducer within the coeliac cavity to be visually recognized.
4374419 DEVICE FOR DETERMINING A RADIATION ATTENUATION DISTRIBUTION IN A PLANE OF A BODY Peter W Lux assigned to U S Philips Corporation
xi
4371976
X-RAY APPARATUS FOR DETERMINING THE ABSORPTION DISTRIBUTION IN A FLAT EXAMINATION ZONE Wagner Wolfgang assigned to U S Philips Corporation
For the backprojection of the convoluted measurement signals in a Cartesian coordinate system in a computer tomography device, it is necessary to recalculate the weighting factors for each position of the source in order to determine the contribution of a convoluted measurement signal to the attenuation value associated with a given element of the output image matrix. This is a time consuming and hence expensive form of reconstruction, and can be avoided by storing all the weighting factors required; this, however, implies a very large memory, and is also expensive. The invention relates to the use of a matrix of elements organized in polar coordinates, which is stored in the memory, the origin central coordinate of said matrix coinciding with the center of rotation of the X-ray source about the object section. The weighting factors are also stored in a polar organized memory. The angular component of the address of the weighting factors is incremented with a rotational increment in the corresponding position of the X-ray source, so that for each group of measurement values, the same weighting factors can be used. The invention enables all the weighting factors to be stored in a memory of limited capacity, the more so because all weighting factors are mirror-symmetrical with respect to a central axis connecting the Xray source to the center of rotation, so that the angular coordinates of the memory need only extend from 0 to pi instead of from 0 to 2 pi.
The invention relates to a computer tomography apparatus for determining the absorption distribution in a relevant zone of a body, this zone being irradiated by unattenuated radiation, while the part of the body which is situated outside this zone is irradiated at the most by attenuated radiation. The radiation outside the relevant zone is attenuated in accordance with the invention by means of absorber pieces which are moved to and from during an examination in a direction parallel to the rotary shaft around which the Xray source is rotated. As a result, the intensity of the radiation is modulated in the time outside the zone, so that on average it is attenuated, without giving rise to hardening effects.
4368535 TOMOGRAPHY FOR PRODUCING TRANSVERSE LAYER IMAGES Baumann Hein assigned to Siemens Aktiengesellschaft
xii