Abstract:
A radiographic imaging apparatus (10) comprises a primary radiation source (14) which projects a beam of radiation into an examination region (16). A detector (18) converts detected radiation passing through the examination region (16) into electrical detector signals representative of the detected radiation. The detector (18) has at least one temporally changing characteristic such as an offset B(t) or gain A(t). A grid pulse means (64) turns the primary radiation source (14) ON and OFF at a rate between 1000 and 5000 pulses per second, such that at least the offset B(t) is re-measured between 1000 and 5000 times per second and corrected a plurality of times during generation of the detector signals. The gain A(t) is measured by pulsing a second pulsed source (86, 100, 138) of a constant intensity (XRef) with a second pulse means (88). The gain A(t) is re-measured and corrected a plurality of times per second during generation of the detector signals.
Abstract:
An ionizing radiation detector module (22) includes a detector array (200), a memory (202), signal processing electronics (208), a communications interface (210), and a connector (212). The memory contains detector performance parameters (204) and detector correction algorithms (206). The signal processing electronics (208) uses the detector performance parameters (204) to correct signals from the detector array (200) in accordance with the detector correction algorithms (206).
Abstract:
A radiation detector (24) for an imaging system includes a two-dimensional array (50) of nondeliquescent ceramic scintillating fibers or sheets (52). The scintillating fibers (52) are manufactured from a GOS ceramic material. Each scintillating fiber (52) has a width (d2) between 0.1 mm and 1 mm, a length (h2) between 0.1 mm and 2 mm and a height (h8) between 1 mm and 2 mm. Such scintillating fiber (52) has a height (h8) to cross-sectional dimension (d2, h2) ratio of approximately 10 to 1. The scintillating fibers (52) are held together by layers (86, 96) of a low index coating material. A two-dimensional array (32) of photodiodes (34) is positioned adjacent and in optical communication with the scintillating fibers (52) to convert the visible light into electrical signals. A grid (28) is disposed by the scintillating array (50). The grid (28) has the apertures (30) which correspond to a cross-section of the photodiodes (34) and determine a spatial resolution of the imaging system.
Abstract:
An x-ray tube assembly (16) includes a vacuum envelope (52) and an x-ray permeable exit window (58). An anode (50) is positioned within the vacuum envelope (52) such that a near side is adjacent to the exit window (58) and a far side is opposite thereof. A cathode assembly (66) is also mounted within the vacuum envelope (52) which directs an electron beam (72) toward a focal spot or point (62) on the far side of the anode (50). The anode further includes a central cavity or indentation (70) which provides a location for mounting a set of radiation attenuating vanes (64) in addition to a shaped x-ray filter or compensator (68). Close placement of the vanes (64) and the filter (68) relative to the focal spot of the anode desirably reduce off focal radiation and allow beam shaping. An externally located collimator (18) further shapes the output x-ray beam.
Abstract:
A CT scanner (10) includes a reconstruction processor (32) for reconstructing an image from digital signals from detector arrays (20). Each detector array includes scintillation crystals (22) arranged in an array for converting x-ray radiation into light. An array of back-illuminated photo diodes (24) is mounted beneath the scintillation crystal array for converting the light emitted from the scintillation crystals into electrical charge. The electrical charge from the back-illuminated photodiodes is transmitted via a path orthogonal to the detector array (20, 40) to signal processing circuitry (66). The back-illuminated photodiode has a backside (26) which is in optical communication with the crystal array (22) and which is optically transmissive to photons of light emanating from the crystal. The converted electrical charge leaves the photodiode via electrical connections (28) or bump bonds (62, 72) on the front side of the photodiode. This arrangement allows a plurality of paths (46) through the substrate (42, 64) supporting the photodiode to provide electrical connectivity (44) from the array to processing circuitry (66), reducing or eliminating the bottleneck of electrical leads from conventional arrays.
Abstract:
An x-ray source (30) transmits a beam of x-rays through an examination region (E). A detector (28), in an initial spatial orientation relative to the source, receives the beam and generates a view of image data indicative of the intensity of the beam received. A first accelerometer (40), capable of generating acceleration data in at least one dimension, is associated with the detector. A second accelerometer (42), capable of generating acceleration data in at least one dimension is associated with the source. A position calculator (60) mathematically calculates a position of both the source and detector based on the acceleration data generated by the accelerometers. An image reconstructor (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.
Abstract:
An improved method for computed tomographic scanning is disclosed. A beam of electromagnetic radiation subtending an angle .phi. is alternately translated and rotated past a patient. The intensity of the beam is detected by an array after the radiation passes the patient and a reconstructed image created from the detected intensities. Each rotation of the array is through an angle less than the angle .phi. subtended by the array producing redundant intensity readings for similarly oriented beam paths through the patient. This redundant intensity data is modified according to a scheme which tends to reduce motion and misalignment artifacts within the patient.
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 one-dimensional multi-element photo detector (120) includes a photodiode array (122) with a first upper row of photodiode pixels and a second lower row of photodiode pixels. The photodiode array (122) is part of the photo detector (120). A scintillator array (126) includes a first upper row and a second lower row of scintillator pixels. The first upper and second lower rows of scintillator pixels are respectively optically coupled to the first upper and second lower rows of photodiode pixels. The photo detector (120) also includes readout electronics (124), which are also part of the photo detector (120). Electrical traces (512) interconnect the photodiode pixels and the readout electronics (124).
Abstract:
A radiation detector module includes a scintillator (62, 62′, 162, 262) arranged to receive penetrating radiation of a computed tomography apparatus (10). The scintillator produces optical radiation responsive to the penetrating radiation. A detector array (66, 66′, 166, 266) is arranged to convert the optical radiation into electric signals. Electronics (72, 72′, 172, 272) are arranged on a side of the detector array opposite from the scintillator in a path of the penetrating radiation. A radiation shield (86, 86′, 100, 100′, 100″, 186, 210, 210′, 286, 286′) is disposed between the detector array and the electronics to absorb the penetrating radiation that passes through the scintillator. The radiation shield includes openings (90, 90′) that communicate between the detector array and the electronics. Electrical feedthroughs (88, 88′, 102, 102′, 102″, 188, 212, 212′, 288, 288′) pass through the radiation shield openings and electrically connect the detector array and the electronics.