Abstract: Detection of ionizing radiation with modulation doped field effect transistors (MODFETs) is provided. There are two effects which can occur, separately or together. The first effect is a direct effect of ionizing radiation on the mobility of electrons in the 2-D electron gas (2DEG) of the MODFET. An ionizing radiation absorption event in or near the MODFET channel can perturb the 2DEG mobility to cause a measurable effect on the device conductance. The second effect is accumulation of charge generated by ionizing radiation on a buried gate of a MODFET. The conductance of the MODFET can be made sensitive to this accumulated charge, thereby providing detection of ionizing radiation. 1-D or 2-D arrays of MODFET detectors can be employed to provide greater detection area and/or spatial resolution of absorption events. Such detectors or detector pixels can be integrated with electronics, such as front-end amplification circuitry.

Abstract: A radiation imaging device (10). The radiation image device (10) comprises a subject radiation station (12) producing photon emissions (14), and at least one semiconductor crystal detector (16) arranged in an edge-on orientation with respect to the emitted photons (14) to directly receive the emitted photons (14) and produce a signal. The semiconductor crystal detector (16) comprises at least one anode and at least one cathode that produces the signal in response to the emitted photons (14).

Abstract: An apparatus for detecting ionizing radiation from a source. A detector is disposed relative to the source to receive the ionizing radiation. The ionizing radiation causes ionization and/or excitation in the detector, wherein an optical property of the detector is altered in response to the ionization and/or excitation. A source of coherent probing light is disposed relative to the detector to probe the detector. The detector outputs the probing light, wherein the output light is modulated in response to the altered optical property. A receiver receives the output light and detects modulation in the output light.

Abstract: Line segments are classified according to orientation to improve list mode reconstruction of tomography data using graphics processing units (GPUs). The new approach addresses challenges which include compute thread divergence and random memory access by exploiting GPU capabilities such as shared memory and atomic operations. The benefits of the GPU implementation are compared with a reference CPU-based code. When applied to positron emission tomography (PET) image reconstruction, the GPU implementation is 43× faster, and images are virtually identical. In particular, the deviation between the GPU and the CPU implementation is less than 0.08% (RMS) after five iterations of the reconstruction algorithm, which is of negligible consequence in typical clinical applications.

Abstract: Methods and systems for producing an image. A measurement is obtained, and a projector function is generated using the obtained measurement. The generated projector function is modified based on an a priori image. An image is reconstructed using the modified projector function.

Abstract: Methods and systems for determining a location of a photon event for an imaging system including a plurality of 3-D detectors. For one of the photons in the photon pair, an interaction in a first 3-D detector is detected. For the other of the photons in the photon pair, at least two interactions in a second 3-D detector are detected. A cone-surface projector function is produced based on the at least two interaction locations in the second 3-D detector. A projector function is produced based on the produced cone-surface projector function, the detected interaction in the first 3-D detector, and the at least two detected interactions in the second 3-D detector.

Abstract: Multiplexing for radiation imaging is provided by using optical delay combiners to provide distinct optical encoding for each detector channel. Each detector head provides an optical output which is encoded. The encoded optical signals can be optically combined to provide a single optical output for all of the detectors in the system. This single optical output can be coupled to a fast photodetector (e.g., a streak camera). The pulse readout from the photodetector can decode the arrival time of the event, the energy of the event, and which channels registered the detection event. Preferably, the detector heads provide coherent optical outputs, and the optical delay combiners are preferably implemented using photonic crystal technology to provide photonic integrated circuits including many delay combiners.

Abstract: An array of two-terminal detectors is configured to provide output signals that provide position sensitive radiation detection (e.g., outputs A and B provide vertical position and outputs C and D provide horizontal position), and which are differential (i.e., signal A+B is equal and opposite to signal C+D). Preferably, a capacitive network is employed to provide the position sensitivity. Array outputs are preferably provided to a low impedance amplifier or opto-electronic coupler.

Abstract: A method and/or device of adaptively controlling an exposure duration for a camera. A determination is made as to whether motion is present. If it is determined that motion is present, exposure duration for one or more images is automatically decreased. If it is determined that motion is not present, the frame exposure duration is automatically increased.

Abstract: Methods and systems for producing an image. A measurement is obtained, and a projector function is generated using the obtained measurement. The generated projector function is modified based on an a priori image. An image is reconstructed using the modified projector function.

Abstract: Methods and systems for determining a sequence of energy interactions in a detector. A plurality of discrete energy interactions is received in a plurality of detector voxels. A plurality of possible sequences of interaction is formed based on the received plurality of discrete energy interactions. For each of the plurality of possible sequences of interaction, an a posteriori probability is computed, where the a posteriori probability is based on a likelihood that the possible sequence of interaction is consistent with the received plurality of discrete energy interactions. Additionally or alternatively, the a posteriori probability may be based on an a priori probability. One of the formed plurality of possible sequences of interaction is selected based on the computed a posteriori probability.

Abstract: Methods and systems for processing an analog signal that is generated by a high energy photon detector in response to a high energy photon interaction. A digital edge is generated representing the time of the interaction along a first path, and the energy of the interaction is encoded as a delay from the digital edge along a second path. The generated digital edge and the delay encode the time and energy of the analog signal using pulse width modulation.

Abstract: Improved position estimation for a square photodetector having terminals at its corners is provided by first estimating an event position in a coordinate system aligned with the diagonals of the square, and then performing a coordinate rotation to provide an estimated position in a coordinate system aligned with the sides of the square. These two steps can also be mathematically combined. It is believed that the improved accuracy of this position determination approach is a result of a greater degree of linearity in charge division between terminals along diagonal axes than along orthogonal axes of a square detector. Flood images provided by this method have been compared to flood images provided by the conventional Anger method, and substantially less image distortion is observed with the present method than with the Anger method.

Abstract: Improved position estimation for a square photodetector having terminals at its corners is provided by first estimating an event position in a coordinate system aligned with the diagonals of the square, and then performing a coordinate rotation to provide an estimated position in a coordinate system aligned with the sides of the square. These two steps can also be mathematically combined. It is believed that the improved accuracy of this position determination approach is a result of a greater degree of linearity in charge division between terminals along diagonal axes than along orthogonal axes of a square detector. Flood images provided by this method have been compared to flood images provided by the conventional Anger method, and substantially less image distortion is observed with the present method than with the Anger method.

Abstract: A front end for an imaging system. The front end comprises at least one magnetically-insensitive high-energy photon detector and an interface for converting an output of the at least one high-energy photon detector to an optical signal and transmitting the optical signal. A receiver is optically coupled to the interface to receive the optical signal and convert the optical signal into a voltage signal.

Abstract: Methods and systems for determining a location of a photon event for an imaging system including a plurality of 3-D detectors. For one of the photons in the photon pair, an interaction in a first 3-D detector is detected. For the other of the photons in the photon pair, at least two interactions in a second 3-D detector are detected. A cone-surface projector function is produced based on the at least two interaction locations in the second 3-D detector. A projector function is produced based on the produced cone-surface projector function, the detected interaction in the first 3-D detector, and the at least two detected interactions in the second 3-D detector.

Abstract: Methods and systems for producing an image. Measurement data is obtained for a coincidence photon event, and a line projector function is generated based on the obtained measurement data. Additional measurement data is obtained for a single photon event, and a cone-surface projector function is generated based on the additional measurement data. An image is reconstructed using the generated line projector function and the generated cone-surface projector function. In another example method for producing an image, a measurement is obtained, and a projector function is generated using the obtained measurement. The generated projector function is modified based on an a priori image. An image is reconstructed using the modified projector function.

Abstract: A charge multiplexed position sensing apparatus and method for measuring an incident radiation with the aid of an array of solid-state photosensitive detectors such as an array of avalanche photodiodes (APDs). The solid-state photosensitive detectors multiplex sum terminal(s) and a number of correspondent spatial terminals separately. Sum signal busses are provided to establish separate connections to the sum terminals of each solid-state photosensitive detector. Spatial signal busses interconnect correspondent spatial terminals of all of the solid-state photosensitive detectors such that correspondent spatial terminals are all connected to the same spatial signal bus. The multiplexing circuit triggers on electrical signals corresponding to sum or total voltages generated by the incident radiation.

Abstract: A radiation imaging device includes scintillation crystal sheets arranged in parallel to each other. Semiconductor photodetector positional detectors read light from large faces of the scintillation crystal sheets to detect interactions in the scintillation crystal sheets and independently provide positional information concerning the interactions relative to at least one axis. The structures of the photodetectors and crystal sheets provide for very small spaces between the sheets.

Abstract: A radiation imaging device includes scintillation crystal sheets arranged in parallel to each other. Semiconductor photodetector positional detectors read light from large faces of the scintillation crystal sheets to detect interactions in the scintillation crystal sheets and independently provide positional information concerning the interactions relative to at least one axis.