Abstract: A scanner (A), such as a CT or MR scanner, non-invasively examines a region of interest of subject and generates a plurality of views indicative thereof which are reconstructible into an image representation. A filter control (14) generates a bandwidth scaling factor (BWF.sub..theta.) and a bandwidth offset (BWO) for each view. Preferably, the selected bandwidth scaling factor is the maximum of a plurality of bandwidth scaling factors based on different criteria including noise, missing views, material surrounding the region of interest, or noise texture. The bandwidth scaling factor is then used to address a filter curve look up table (18) to select from a plurality (N.sub.T) of filter values. The digital filter values are interpolated (20) or extrapolated as necessary to match the number of values (N.sub.S) in each sampled view.

Abstract: A first image (20) and a second image (22) are taken through the patient's heart region at small time displaced intervals. The first and second images are subtracted (24) to generate a difference image which is indicative of the tissue which has moved during the short time interval, i.e. the boundary of the ventricles. Voxels from regions outside the boundary are adjusted to remove lung tissue (40), and ventricle boundary or edge voxels (48) and analyzed to generate a non-blood tissue histogram (62). Voxels within the boundary are analyzed to generate a blood tissue histogram (60). The histograms are fit (66, 74) to smooth curves which represent the probability distribution or confidence that each voxel value represents blood or non-blood tissue. Contiguous voxels within the boundary are counted (96) and adjusted for voxel size (98) to create an indication of left and right ventricle volume (100l, 100r).

Abstract: An x-ray tube includes an anode (A) and envelope (C) which are rotated (D) at a relatively high rate of speed. A cathode assembly (B) is supported in the envelope on a bearing (32). In order to hold the cathode assembly stationary, a magnetic susceptor (40) having periodic projections (44) is disposed with the projections closely adjacent an outer peripheral wall (20) of the envelope. A plurality of permanent magnets (52) are mounted on a stationary keeper (50), each magnet adjacent one of the susceptor projections. Preferably, the magnets have alternating polarity such that magnetic flux lines (54) flow between adjacent magnets through the magnetic susceptor.

Abstract: A toroidal x-ray tube housing (A) has an evacuated interior. An annular anode (B) is connected with the housing closely adjacent the window such that a cooling fluid passage (12) is defined in intimate thermal communication with the anode. A cathode assembly (32) is mounted within the evacuated housing or an annular ring (30) that rotates an electron beam (22) around the large diameter annular anode. In the embodiment of FIGS. 1 and 2, the annular ring is magnetically levitated (40) and rotated by a motor (50). A collimator (62) and filter (64) are rotated with the cathode assembly closely adjacent an electron emitter or cathode cup (32) such that the generated x-rays are collimated and filtered within the x-ray tube. Preferably, a plurality of cathode cups (120) are provided, whose operation is selected by a series of magnetically controlled switches (76). The cathode cup is insulated (106) from the annular ring and isolated by a transformer (104, 112) from the filament current control switches.

Abstract: A target track (20) of an anode (14) of an x-ray tube becomes heated adjacent a focal spot (18) to temperatures on the order of 1100.degree.-1400.degree. C. To protect the anode, a body portion (34) is coated (46) with a thermal energy emissive oxide layer (48). In order to prevent carbon from the body portion from migrating out to the oxide layer and forming carbon monoxide gas, a carbide forming barrier layer (36) is formed (38,40) between the body and the oxide coating. The barrier layer is a dense, substantially pore-free coating of a metal that has a free energy of carbide formation of at least 100 KJ/mole at 1200.degree. C. Preferably, the barrier layer material is zirconium, although hafnium, titanium, vanadium, uranium, tantalum, niobium, chromium, and their alloys also provide acceptable barriers to carbon atom migration.

Abstract: A CT scanner (10) non-invasively examines a region of interest of a patient to create an image representation that is stored in an image memory (14). Each pixel of the image representation has a relatively large number of bits of radiation intensity resolution, e.g. 14 bits or 16k levels, which is larger than the gray scale resolution of a conventional video monitor (24), e.g. 8 bits or 256 levels. A look-up table (38) digitally filters each pixel value with digital filter values to reduce the number of levels of each pixel value to the number of gray scale levels displayable by the video monitor. While the image is being displayed, the operator selectively adjusts the digital filtering to optimize the displayed image for the intended diagnostic purpose. During the vertical flyback or other non-display periods of the video monitor, a central processor (30) generates most significant bits of addresses that read digital filter longwords from a filter memory (44).

Abstract: The radiation source (22) rotates around a patient on a patient couch (30) as the couch is advanced through an examination region (14). Radiation detectors (24) detect radiation that has passed through the patient along rays of a plurality of fan shaped views. Each view is identifiable by its angular position around the examination region and its longitudinal position in the spiral and each ray is identifiable by its angular position in the fan. An interpolator (46) interpolates views collected over more than two revolutions of spiral path using an interpolation function (FIGS. 1A-1D). A set of interpolated views is reconstructed (54) into a series of image representations representing parallel planar slices through the imaged volume. In some reconstructions, particularly reconstructions in which a 180.degree. based reconstruction algorithm is used or the energy of the x-ray beam is varied, the filter function is varied from ray to ray within each view.

Abstract: A magnetic resonance imaging sequence (FIG. 2 ) is applied with a phase encode gradient (60) between an RF excitation pulse (50) and a refocusing pulse (54) such that out-of-slice artifacts are collapsed into a single line or column (64) in a resultant image display (38). A digital radio frequency transmitter (20) adds an adjustable RF phase component (70) to the excitation pulse and digital radio frequency receiver (26) adds the inverse or negative of the phase component (72) to a received magnetic resonance echo (56). The RF phase increment is adjusted such that the artifact line is displayed at the edge or other selected portion of the resultant image away from a region (74) of primary interest. An operator control (80) enables the field of view to be shifted in the phase encode direction to view different portions of the patient along the phase encode axis.

Abstract: Radiation from an x-ray source (14) is collected by radiation detectors (16) to generate an original set of CT line integral data (18). The original CT data is subject to a first order correction and reconstructed (20) to generate a first order corrected image representation (22). A first artifact image representation (26) is generated (24) from the first order corrected image. The artifact image representation and the first order corrected image representation are subtractively combined (28) to generate a second order corrected image representation (30). A bone and high density clip image representation (142) is generated from the second order corrected image. The bone and clip image representation is forward projected (144) to generate a first high contrast line integral data set (146). High contrast model line integral data corresponding to rays which traverse the high density clip are topologically transposed (148) for corresponding rays of the original CT data.

Abstract: An anode (A) closes one end of an evacuated envelope (C) and a cathode end plate (22) closes the other. A cathode assembly (B) is mounted on a bearing (40) in the evacuated envelope such that the envelope and cathode can undergo relative rotation. A motor (38) rotates the anode and envelope while a pair of magnets (44, 46) hold the cathode assembly stationary. Bearing (40) functions as a current path from a current source (72) to the primary windings of a transformer (58). Another bearing (94) provides a return current path from the transformer to the current source. The secondary windings of the transformer are connected with a cathode filament (52). The transformer enables a relatively low ampere current to pass through the bearings to limit cathodic damage to the bearings, yet provides sufficient amperage to the filament to cause thermionic emission.

Abstract: A trackball (10) is rotatably mounted on rollers (12, 14). The rollers are connected with rotational encoders (16, 18) for producing a series of pulses. Up/down counters (20, 22) convert the pulses into an indication of translation along two axes. Downward, non-rotational pressure on the trackball causes a transducer (B) to output an electrical signal which is recognizable as a selection signal. In some embodiments, the transducer is a strain gauge or other transducer (50) which provides an output whose magnitude varies with the amount of force. A comparitor (54) compares the output of the transducer with a selectable threshold to indicate whether a selection signal is to be issued. In other embodiments, the transducer has two states, e.g. a mechanical switch (70). The transducer changes states in response to the force on the trackball exceeding a preselected minimum.

Abstract: A CT or other radiographic scanner (A) generates data that is arranged into sets (32). Each set is convolved (40) with a convolution function (42) and backprojected (44) into an image memory (46) along a corresponding one of a plurality of rays. A corresponding gradient image (52) in which each pixel value has either a one or a zero value is forward projected (54) and compared (60) with a standard. The comparison indicates along which rays data sets including bad data were projected. To subtract the bad data contribution from the image, the image representation is forward projected (90) along the identified rays, convolved (40) with a negative of the convolution function (84), and backprojected (44) along the identified ray into the image memory (46). Further correction may be obtained by replacing the subtracted data with interpolated data.

Abstract: An x-ray source (20) rotates about a fixed cylinder (16) within which a subject of non-uniform cross-section is received. Radiation from the x-ray source passes through the subject and impinges on an arc of radiation detectors (28). Because the subject is of non-uniform cross-section, the average x-ray energy fluence impinging on the detectors across the arc varies with the relative angular position of the x-ray source and the subject. In one embodiment, a motor (18) which rotates the x-ray tube relative to the subject is controlled by a digital motor control (50). The digital motor control varies the rotational speed to a preselected angular velocity indicated by a look-up table (52) at each of a multiplicity of angular positions around the subject.

Abstract: In a magnetic resonance apparatus, motion artifacts in data obtained are reduced by transmitting, during data collection, an r.f. signal of known amplitude and of a frequency different from that of the spins excited for imaging, and utilizing a signal induced by that r.f. signal in a coil (45A,45B) positioned adjacent the data signal detector means (10A,10B) to effect an alteration of the signal produced by the detector means (10A,10B) such as to reduce the motion artifacts.

Abstract: The power brush block assembly (26) and a communication signal brush block assembly (28) are mounted to a rotating gantry portion (20) of a CT scanner in sliding communication with a stationary slip ring (16). The power communication brush block includes a plurality of like mounting blocks which when interconnected together in alignment define a locator aperture (64') and a shaft aperture (26') in radial alignment. A brush (70) includes a tip (72) and a shaft (76) around which a coil spring (100) is slidably received. The brush and spring assemblies are slidably received through the locator aperture until the brush tip is in sliding communication therewith and the shaft is in sliding communication with the shaft aperture. A retainer (102) prevents the spring from propelling the brush completely through the locator aperture. An electrical lead (104, 104') has a friction connector (106) which is connected to one end (78) of the brush shaft and connected at its other end with an electrical contact (88, 88' ).

Abstract: A diagnostic imaging system is comprised of a plurality of linearly adjustable functions and a plurality of binary selectable functions which are controlled by a multi-function joystick controller. The controller has a plurality of function select switches, a joystick, a mushroom cap rotatably engaged on the joystick, a microprocessor, a plurality of switches individually engageable by pivoting the joystick and a pair of switches individually engageable by clockwise or counterclockwise rotation of the mushroom cap. The switches and the microprocessor cooperate such that the selection of a first function select switches causes the operation of the joystick switches and/or mushroom cap switches to be linked to a predetermined first set of imaging system functions. Subsequently, when a second function select switches is selected the joystick switches and mushroom cap switches thereafter operate a predetermined second set of imaging system functions until another function select switch is selected.

Abstract: An x-ray source propagates radiation across an examination gap onto a intensifier tube input screen. The output screen of the intensifier tube is viewed by a video camera. A sampling means is disposed between the intensifier output screen and the video camera. The sampling means views the intensifier output screen and converts the viewed image into an electronic control signal for the x-ray source. The sampling means includes a first block pivotally secured to a second block below a receiving hole in the first block. The blocks are adjustably biased in pivoting tension about a pivot below the receiving hole. A barrel is frictionally engaged in the receiving hole. One end of the barrel is angled on one side and cutout on the other side. A mirror is fixedly disposed on the angled side such that light propagating through the cutout is reflected through the central axis of the barrel to a photo diode fixedly disposed at the other end of the barrel.

Abstract: An x-ray tube (10) of a CT scanner has a rotating anode and rotor combination which is propelled by AC currents applied to run and phase windings (42, 46) by a starter (22). A monitor (24) includes Hall effect current detectors (40, 44) which detect the actual current flowing through the run and phase windings. The detected analog current values, voltage values, and the like are multiplexed (132) and digitized in a preselected order by an analog to digital converter (60) and stored in that order in a FIFO memory (62). A microprocessor (64) performs a Fourier transform (94, 96) to convert the digital run and phase signals into frequency spectra. The run and phase frequency spectra are compared (100, 102, 104, 106) with frequency spectra indicative of rotor speed, bearing wear, anode vibration, failure of the anode to rotate, and other conditions, analyzed for symmetry or other characteristics, or the like (FIG. 5 ) to generate digital run and phase reference signals.

Abstract: A cardiac electrode (40) has a plug (48) which is frictionally received in a socket (50) of an electrical lead (56). An impedance (54) is connected in series between the electrical lead and the socket to pass ECG signals substantially unattenuated and for blocking radio frequency signals induced in the lead from reaching the socket and the electrode and heating the electrode to a sufficient temperature to burn the patient. The impedance includes an LC circuit (66, 68) which freely passes low frequency signals, such as cardiac signals, but which is tuned to resonance at radio frequencies, particularly at the frequency of resonance excitation and manipulation pulses of a magnetic resonance imager (A). Alternately, the impedance may include a resistive element for blocking the induced currents. A temperature sensor (60) is mounted in intimate contact with an electrically and thermally conductive socket portion (52) to sense the temperature of the electrode, indirectly.

Abstract: A SPECT system includes three gamma camera heads (22a), (22b), (22c) which are mounted to a gantry (20) for rotation about a subject (12). The subject is injected with a source of emission radiation, which emission radiation is received by the camera heads. A reconstruction processor (112) reconstructs the emission projection data into a distribution of emission radiation sources in the subject. Transmission radiation from a radiation source (30) passes through the subject and is received by one of the camera heads (22a) concurrently with the emission radiation. The transmission radiation data is reconstructed into a three-dimensional CT type image representation of radiation attenuation characteristics of each pixel of the subject. An attenuation correction processor (118) corrects the emission projection data to compensate for attenuation along the path or ray that it traversed. In this manner, an attenuation corrected distribution of emission sources is generated.