xii New Patents

detectors in chain-like sequences across the detector array 10 by successive pair-wise common-path sensitivity comparisons starting from a terminal detector 25, 26, each sequence normally involves 30 or more successive com- parisons, and consistent but unpredictable er- rors are found to occur, leading to incorrect Houndsfield values in the computed image matrix (24). The improvement comprises locating at least one radiation transparent detec- tor 27 of high stability in front of the array 10 at an intermediate point and using the output to further correct the chain-corrected detector sensitivity values. A detector 27 comprising a plastics scintillator optically coupled to a photo- multiplier is described, whose output pulses are counted (36) during a rotational scan and com- pared with the mean corresponding measure- ment from detectors 28 lying behind the detector 27, to form a sensitivity ratio (43). From a cor- responding ratio and data derived during calibration, a measured sensitivity value for detectors 28, is determined for each scan and is compared with the corresponding chain- corrected sensitivity value to generate a further sensitivity correction value which is then dist- ributed among the detectors of the comparison sequence (44).

4475396

METHOD OF DETERMINING ULTRASONIC ATTENUATION OF

TISSUE USING REFLECTIVE TOMOGRAPHIC

RECONSTRUCTION

Stephen W Flax, Gary H Glover assigned to General Electric Company

Ultrasonic wave attenuation is determined for a plurality of limited volumes of tissue comprising a body under examination by directing ul- trasonic waves through each limited volume along a plurality of vectors, determining a measure of attenuation of the limited volume by detecting the frequency shift of reflections of the ultrasonic wave along each vector, and averaging the attenuation of each limited volume from each vector intersecting the limited volume.

4476389

EMISSION TYPE COMPUTED TOMOGRAPHY APPARATUS

Akihid Ueyama, Nobuo Kumano, Hidetomo Takase, Tochigi, Japan assigned to Tokyo Shibaura Denki Kabushiki Kaisha

An emission type computed tomography ap- paratus comprises a mechanism for rotating a detector along a circle centered at a human body to whom radioisotope is previously given, and a circuit for reconstructing a tomogram in ac- cordance with an output signal from said detec- tor. The rotating mechanism further has a member for slanting the detector with respect to a tangential line of the circle, a member for slan- ting said detector with respect to the body axis, and a member for changing the radius of the rotating circle of the detector.

4477728

RADIATION DETECTOR

Toshihiro Rifu, Ootawara, Japan assigned to Tokyo Shibaura Denki Kabushiki Kaisha

A radiation detector adapted to be used with a computerized tomographic apparatus, wherein filters prepared from a radiation-absorbing material are provided on the outside of a radiation-permeable window in the positions facing radiation-detecting cells. The filters com- pensate for differences between the radiation- detecting properties of the detection cells, thereby equalizing said radiation-detecting pro- perties.

4477922

TOMOGRAPHIC X-RAY APPARATUS FOR THE

PRODUCTION OF TRANSVERSE LAYER IMAGES

Reiner Liebetruth, Erlangen, Federal Republic Of Germany assigned to Siemens Aktiengesel- lschaft

In an extension of the utility of rotary scan tomographic x-ray apparatus, the apparatus is locked in a fixed angular relationship and the patient support is automatically advanced in small longitudinal increments relative to the