Abstract:
A radiation detector module (22) particularly well suited for use in computed tomography (CT) applications includes a scintillator (200), a photodetector array (202), and signal processing electronics (205). The photodetector array (202) includes a semiconductor substrate (208) having a plurality of photodetectors and metalization (210) fabricated on non-illuminated side of the substrate (208). The metalization routes electrical signals between the photodetectors and the signal processing electronics (205) and between the signal processing electronics (205) and an electrical connector (209).
Abstract:
A radiation detector (30) for a computed tomography scanner (12) includes a support structure (62). An alignment board (60) secures to the support structure (62) and includes photolithographically defined alignment openings (70) arranged to define a spatial focal point (34) relative to the alignment board (60). An anti-scatter element (32) is disposed on the support element (62) and includes one or more protrusions (86) which mate with the alignment openings (70) of the alignment board (60) to align the anti-scatter element (32) with the spatial focal point (34). A detector board (104) includes alignment structures (106) that align the detector board (104) with the anti-scatter element (32).
Abstract:
An x-ray source (30, 80, 100) transmits a beam of x-rays through an examination region (E). A receiver (28, 82, 102), in an initial spatial orientation relative to the source (30, 80, 100), receives the beam and generates a view of image data indicative of the intensity of the beam received. A sensor, such as an accelerometer, detects motion in a selected portion of a mechanical structure (M) supporting the source (30, 80, 100) and the receiver (28, 82, 102). Upon detection of motion, the sensor generates a motion signal. In one embodiment, a first accelerometer (40, 90) is associated with the receiver (28, 82) and a second accelerometer (42, 88) is associated with the source (30, 80). A position calculator (58, 60) mathematically calculates a position of both the source and receiver based on the acceleration data generated by the accelerometers. An image reconstruction processor, (62) receives the relative position data, electronically corrects for any misalignment or change in beam travel distance, and reconstructs the views into a volumetric image representation. In another embodiment, a sensor (108) detects motion of a mechanical structure (M2) and provides a motion signal to a processor (110). The processor (110) compares the detected motion with a database loaded with an empirically determined vibration model. Based on this comparison, the processor (110) then generates a cancellation signal, which controls an electromechanical actuator (106) to impart an offsetting force or motion to the mechanical structure (M2).
Abstract:
A source (A) of images, such as a CT scanner (10), a magnetic resonance imaging apparatus (12), and the like produces a plurality of basis images (I.sub.0, I.sub.1, I.sub.2, I.sub.3 . . . ). Two of the basis images are subtracted and divided (70, 72) by a number of interpolation increments (L.sub.1) to form a first differential image (I.sub..DELTA.1). The first and the third basis images are subtracted and divided (76, 78) by a number of available interpolation increments (L.sub.2) to form a second differential image (I.sub..DELTA.2). Four differential images are selectively combined and divided by a product of the first and second available increments (82, 84) to form a second order differential image (I.sup.2.sub..DELTA.12). An array of adders (D) selectively adds the first differential image to a currently displayed image stored in an image memory E each time a track ball (104) moves a cursor one increment in a horizontal position. Each time the track ball moves the cursor one increment up or down along the vertical column, the adder array adds or subtracts the second differential image to the currently displayed image. Each time the track ball steps the cursor between rows or between columns, the second order differential image is used to correct one of the first and second differential images. In this manner, only the currently displayed image, the first differential image, the second differential image, and the second order differential image need be stored to provide free interpolation among four basis images. The basis images themselves need not be stored.
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. To this end, the image representation is again forward projected (90) along the identified ray, convolved (40) with the original selected convolution function (42), and backprojected (44) into the image representation (46) along the identified ray.
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. The angular velocity is slowed when radiation is passing through thicker portions of the subject and accelerated when passing through thinner portions of the subject such that the average x-ray energy fluence received by the radiation detectors is substantially constant regardless of the angular position of the x-ray source. In another embodiment, an x-ray tube control circuit (82) alters the tube current such that the average x-ray energy fluence received by the detectors becomes angular position independent. In this manner, the signal-to-noise ratio at each angular position is the same and structural noise is eliminated in the resultant reconstructed image.
Abstract:
Detectors (20) of a CT scanner (10) have a radiation receiving face (34) which is larger than a photosensitive face (30) of a photodiode (22). Lead wires (28) connect the ends of the diode photosensitive surface to terminals (26). A scintillation crystal (32) has an overhanging portion (38) which overhangs at least the interconnection between the lead wires and the photosensitive face to protect the adjoining areas of the photosensitive face from incident radiation. This enables the radiation receiving surface to be larger than the photosensitive surface. The crystal is either undercut to define the overhanging area or a section of light pipe (60) is provided between the photosensitive surface and the crystal. Increasing the radiation receiving face decreases rotor ripple artifacts. Decreasing the photosensitive face area decreases diode capacitance and increases resistance which improves amplifier performance.
Abstract:
A phantom (FIG. 1) has a bone mineral standard (B) surrounded by tissue equivalent material (A) with a plurality of different cross sections. The phantom is disposed in an image region (44) of a tomographic scanner (FIG. 2). Scans are conducted through a plurality of different cross sections of the phantom to reconstruct a plurality of phantom image representations (62). The plurality of phantom image representations are stored by size in a correction memory (70). Thereafter, a patient is disposed on a patient table (50) in the image region and an image is taken through the patient's mid-section between the L2 and L5 vertebrae. A patient image representation is reconstructed and stored in an image memory (64). A slice size calculation circuit (72) determines the size of the patient slice. The correction memory is addressed with the calculated size to retrieve the phantom image representation of the most similar size. An image correction circuit (74) calibrates the patient image representation in accordance with the retrieved phantom image representation.
Abstract:
An improved method and apparatus for transaxial tomographic scanning of a patient. A scanning system is provided having a rotatably mounted X-ray radiation source/detector pair which orbits and radially scans the patient in the plane of orbit. The source provides a plurality of beams of radiation having axes in the orbital plane. The beams pass through the patient to an array of detectors each of which is aligned with one of the beams. Radiation intensity data is collected at predetermined orientations of each beam/detector pair as the assembly orbits about the patient. In a preferred embodiment the rotatably mounted source-detector pair is rotated as a unit through a preselected rotation angle .phi. about an axis effectively passing through the source. The axis and the source-detector pair connected to it are then orbited around the patient through an orbit angle .gamma. while maintaining the preselected rotation angle .phi.. The axis is orbited about an origin lying in the orbital plane. A set of measurements is taken during the orbit as the beams from the X-ray source sweep through substantially uniformly spaced, coplanar points [t(k), .phi.(n)] defined about the origin. After an orbit, the rotation angle .phi. is incremented, and the source detector pair re-orbits the patient for providing a new set of measurement data corresponding to the incremental rotation angle .phi.. Exact reconstruction is achieved after several orbit cycles when measurements are taken at the angles .phi., .gamma. characterized substantially as ##EQU1## WHERE D REPRESENTS THE DISTANCE BETWEEN THE ORIGIN AND THE CENTER OF ROTATION, AND K, N ARE INTEGERS.
Abstract:
An improved method and apparatus for transaxial tomographic scanning of a patient. A scanning system is provided having a rotatably mounted X-ray radiation source/detector pair which orbits and radially scans the patient in the plane of orbit. The source provides a plurality of beams of radiation having axes in the orbital plane. The beams pass through the patient to an array of detectors each of which is aligned with one of the beams. Radiation intensity data is collected at predetermined orientations of each beam/detector pair as the assembly orbits about the patient. In a preferred embodiment the rotatably mounted source-detector pair is rotated as a unit through a preselected rotation angle .phi. about an axis effectively passing through the source. The axis and the source-detector pair connected to it are then orbited around the patient through an orbit angle .gamma. while maintaining the preselected rotation angle .phi.. The axis is orbited about an origin lying in the orbital plane. A set of measurements is taken during the orbit as the beams from the X-ray source sweep through substantially uniformly spaced, coplanar points [t(k), .theta.(n)] defined about the origin. After an orbit, the rotation angle .phi. is incremented, and the source detector pair re-orbits the patient for providing a new set of measurement data corresponding to the incremental rotation angle .phi.. Exact reconstruction is achieved after several orbit cycles when measurements are taken at the angles .phi., .gamma. characterized substantially as ##EQU1## OF ROTATION, AND K, N ARE INTEGERS.
Abstract translation:一种用于患者的横断层扫描的改进的方法和装置。 提供扫描系统,其具有可旋转地安装的X射线辐射源/检测器对,其在轨道平面中轨道和径向扫描患者。 源提供多个在轨道平面中具有轴的辐射光束。 光束通过患者到一组检测器,每个检测器与一个光束对准。 随着组件围绕患者轨道,辐射强度数据被收集在每个束/检测器对的预定取向处。 在优选实施例中,可旋转地安装的源 - 检测器对作为一个单元通过围绕有效地穿过源的轴的预选旋转角度φ1旋转。 然后连接到其上的轴和源 - 检测器对绕着患者通过轨道角γ,同时保持预选的旋转角度phi。 轴围绕位于轨道平面中的原点绕轨道运动。 在轨道期间进行一组测量,因为来自X射线源的光束扫描基于原点定义的基本均匀间隔的共面点[t(k),θ(n)]。 在轨道之后,旋转角度phi增加,并且源检测器对重新轨道到患者,以提供对应于增量旋转角度phi的一组新的测量数据。 在几个轨道周期之后实现精确的重建,当以角度phi进行测量时,γ基本上表示为k DELTA t phi = sin 1和γ= phi + n DELTAθ,旋转角,和K,N为整数 。