Abstract: A method of minimizing a streaking effect found in reconstructed images obtained from high resolution CT scanning of a small scan circle that corresponds to a limited region of interest, such as portions of the spinal cord of a patient, particularly in scans that include concentrated high density material, such as bone, situated outside the small scan circle. The approximate range of view angles that will project bone from outside the limited region of interest is determined. Detectors corresponding to the determined region are selected out. The projection data acquired by the selected detectors is filtered. The filtering is accomplished by convolving the projection data with a preselected filter function or in machine implemented form by passing the electrical signal representing the projection data through a low pass filter.

Abstract: A curved faced, disc shaped transducer and an oppositely facing, circular angularly disposed mirror form the transmission and reception path of a mechanical sector scan imaging system. The transducer and mirror are mounted on a common axis, and a shaft upon which the mirror is affixed oscillates about that axis. Through a belt drive mechanism, a motor provides the oscillating motion, in turn scanning the ultrasound beams through the subject by virtue of the mirror motion. An optical encoder records positional information from the motor, for coordination of the mirror oscillation with transducer signals, and thereby for the assembly of a composite image.

Abstract: Encoded data is sequentially read into a shift register having a number of stages larger than the largest inter-scan "void" or "hole" to be filled. A priority encoder determines the length of the void to be filled, and the amplitude difference of successive scan data samples is evaluated. For each display picture element in the void, a weighting select PROM determines an appropriate weighting factor, based on the size of the void to be filled. Separate positive differential and negative differential memories are thereby energized to produce, for each display picture element in the hole, a simulated display picture data element.

Abstract: A method of preprocessing incomplete or truncated projections obtained from high resolution CT scanning of a small scan circle corresponding to a limited region of interest within the scanned object. An air calibration is performed to obtain a set of air values. The intensity values obtained during the partial area scan are subtracted from the air values to convert the intensity values to attenuation values. The approximate slope at either end of the truncated projection is then calculated. Based on the attenuation values and the slope the necessary extrapolation of the truncated projection is performed to complete the projection. No measurements, ionizing or otherwise, are required from the region outside of the small scan circle.The completed projection is ready for conventional reconstruction techniques involving convolution and back projection.

Abstract: Disclosed is a collimator for a tomographic scanner which performs the collimator function of dividing a fan of radiation into a multiplicity of finger beams and the attenuator function of causing a generally bell-shaped radiation energy distribution across a scan circle. The collimator has larger effective apertures for forming radiation into finger beams to traverse the center of the scan circle than for forming finger beams to traverse the edges of the scan circle. The width of the collimator apertures are defined by radially oriented vanes arranged along a circular arc. By offsetting the radiation source from the geometric center of the circular arc, the vanes defining the width of some apertures are more skewed than others relative to the radiation paths.

Abstract: A method of emission tomography using a gamma camera and a rotating collimator having an array of a large number of slanted, small diameter holes. A planar projection corresponding to each angular orientation assumed by the collimator is recorded. From these series of planar projections, a three-dimensional simulation model is reconstructed by an iterative algorithm which approximates the emitting object. The simulated model comprises multiple separable planes.

Abstract: Ultrasound breast scanning and diagnosis is achieved by suspending the breast in a water pool, in which is immersed a wide aperture transducer/lens assembly. The water path is defined by two separate segments, an upper one, into which the breast is suspended, contained by a flexible sonically transparent bag member, and the lower being contained in a longitudinally movable tank which is filled to contact with the bag member portion protruding into the tank.

Abstract: Images and respectively associated timing marks are arrayed, as phototransparencies, about a disk. The disk is rotated and the timing marks are sensed. Display occurs either in two-dimensional fashion, such as in a television system, or in three-dimensional fashion such as in a semitransparent full image projection. Associated logic circuitry determines whether the full 3-D transparency is to be produced, in which case all images on the disk are to be illuminated, or whether swim through will occur, either on an image at a time or on a "ham slice" projection basis.

Abstract: The invention relates to the method for constructing a representation of the variation of attenuation of penetrating radiation in a planar slice of a patient positioned in a scan circle. The patient is irradiated with a fan shaped swath of radiation which is rotated about the patient for 180.degree. plus approximately the angle of the fan. Radiation passing through the scan circle is converted to sets of data, each set representing a radiation attenuation across a fan. The sets of data are filtered with a window function to remove data from some of the sets which represent radiation passing through a point in the scan circle by more than 180.degree. relative to radiation paths through the same point. The sets of data are serially convolved and back-projected into an image memory for display on a video monitor.

Abstract: A radiation detector or detector array which has a non-constant spatial response, is disclosed individually and in combination with a tomographic scanner. The detector has a first dimension which is oriented parallel to the plane of the scan circle in the scanner. Along the first dimension, the detector is most responsive to radiation received along a centered segment of the dimension and less responsive to radiation received along edge segments. This non-constant spatial response can be achieved in a detector comprised of a scintillation crystal and a photoelectric transducer. The scintillation crystal in one embodiment is composed of three crystals arranged in layers, with the center crystal having the greatest light conversion efficiency. In another embodiment, the crystal is covered with a reflective substance around the center segment and a less reflective substance around the remainder.

Abstract: The invention comprises a shaped filter and a filter correction circuitry for computerized tomographic scanners. The shaped filter is a generally U-shaped block of filter material which is adapted to be mounted between the source of radiation and the scan circle. The U-shaped block has a parabolic recess. The filter material may be beryllium, aluminum, sulphur, calcium, titanium, erbium, copper, and compounds including oxides and alloys thereof. The filter correction circuit comprises a first filter correction profile adding circuit for adding a first scaler valve to each intensity valve in a data line. The data line is operated on by a beam hardness correction polynomial. After the beam hardness polynomial correction operation, a second filter correction circuit adds a second filter correction profile consisting of a table of scalor values, one corresponding to each intensity reading in the data line.

Abstract: In an ultrasound imaging system employing a moving or oscillating transducer, actual transducer position is detected periodically, rather than continuously. A magnet is caused to oscillate with the transducer, and periodic alignment of the magnet with a fixedly mounted Hall effect switch provides synchronization data for sonic pulse generation, pulse-echo receipt, and image assembly and display.

Abstract: A water conditioning system for maintaining and conditioning the water used in an ultrasound imaging system especially adapted to perform diagnosis of the human breast. The system includes a cabinet enclosing a main tank which contains an ultrasound transducer and associated focusing lens submerged in water. The main tank has associated with it a main reservoir. A second quantity of water which is adapted to receive the patient's breast is contained in a flexible bag having an open end supported adjacent the patient and having a closed end draped into engagement with the water in the pool and the water in the tank. The suspension pool also has a reservoir associated with it. The main tank and the suspension pool each have separate but interdependent fluid circulation circuits for conditioning the water in the tank and the suspension pool to provide a good transmission medium by filtering heating purifying and monitoring the water level of the water in the tank and in the suspension pool.

Abstract: A B-scan pulse echo ultrasound system produces a real time image of a body area under inquiry, and an aspiration needle is inserted directly into that area. The needle carries a small, omni-directional ultrasound transducer, electrically connected through the needle to transponder electronics. Incident pulses from the imaging transducer to the omni-directional transducer are sensed at the latter, and the position thereof is inserted into the image either by generation of a return signal from the needle point, or through delay logic and subsequent production of a composite.