Abstract: A method of PET image reconstruction is provided that includes obtaining intra-patient tissue activity distribution and photon attenuation map data using a PET/MRI scanner, and implementing a Maximum Likelihood Expectation Maximization (MLEM) method in conjunction with a specific set of latent random variables, using an appropriately programmed computer and graphics processing unit, wherein the set of latent random variables comprises the numbers of photon pairs emitted from an electron-positron annihilation inside a voxel that arrive into two given voxels along a Line of Response (LOR), where the set of latent random variables results in a separable joint emission activity and a photon attenuation distribution likelihood function.

Abstract: We provide improved maximum likelihood expectation maximization (MLEM) joint estimation of emission activity and photon attenuation from positron emission tomography (PET) data. Lines of response (LOR) are divided along their length into cells having equal length. MLEM computations assume all intersections between LOR cells and voxels have an intersection length of the LOR cell length. This way of discretizing the problem has the significant advantage of leading to MLEM update equations that have a closed form exact solution, which is important for fast, accurate and robust estimation.

Abstract: We provide improved maximum likelihood expectation maximization (MLEM) joint estimation of emission activity and photon attenuation from positron emission tomography (PET) data. Lines of response (LOR) are divided along their length into cells having equal length. MLEM computations assume all intersections between LOR cells and voxels have an intersection length of the LOR cell length. This way of discretizing the problem has the significant advantage of leading to MLEM update equations that have a closed form exact solution, which is important for fast, accurate and robust estimation.

Abstract: Simultaneous dual-isotope positron emission tomography (PET) is used to improve disease evaluation. Two distinct molecular probes are simultaneously provided to the imaging target. One of the probes is labeled with a radionuclide that emits positrons to provide double coincidence events in PET. The other probe is labeled with a radionuclide that emits positrons+prompt gammas to provide triple coincidence events in PET. One of the probes is a metabolic probe, and the other probe is a selective probe that includes a ligand or antibody that is biologically responsive to receptor/antigen status. A PET system is employed that can provide simultaneous double coincidence and triple coincidence PET images. The resulting images provide simultaneous metabolic imaging and receptor/antigen imaging. Applications include disease evaluation, such as cancer staging (e.g., for breast cancer, prostate cancer, etc.).

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: Positron emission tomography (PET) systems suitable for use with dirty (positron+prompt gamma) emitters are provided. One or more prompt gamma detectors are added to the PET system, where the prompt gamma detectors are responsive to the prompt gammas provided by the dirty emitter, but are not responsive to 511 keV annihilation photons. The prompt gamma detectors can surround the imaging PET detector array and/or be disposed as end caps relative to a generally cylindrical PET detector array. The prompt gamma detectors need not provide spatial resolution, because coincidence events in the PET detector array are classified as 2-photon or 3-photon events depending on whether or not there is a time-coincident signal from the prompt gamma detectors. One application of this approach is dual isotope PET where distinct tracers labeled with clean and dirty positron emitters are simultaneously imaged.

Abstract: A method of PET image reconstruction is provided that includes obtaining intra-patient tissue activity distribution and photon attenuation map data using a PET/MRI scanner, and implementing a Maximum Likelihood Expectation Maximization (MLEM) method in conjunction with a specific set of latent random variables, using an appropriately programmed computer and graphics processing unit, wherein the set of latent random variables comprises the numbers of photon pairs emitted from an electron-positron annihilation inside a voxel that arrive into two given voxels along a Line of Response (LOR), where the set of latent random variables results in a separable joint emission activity and a photon attenuation distribution likelihood function.

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: 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: Compressed sensing (CS) estimation approaches rely on a priori sparsity to significantly reduce the number of samples needed to provide high sampling fidelity, relative to the normal Shannon-Nyquist limit. Accordingly, CS approaches are of considerable interest for detector multiplexing in applications which have inherently sparse signals (e.g., the two correlated photon detection events in PET imaging). However, CS approaches also tend to fare poorly in the presence of noise, which has limited their applicability in practice. In this work, we show that CS estimation can be used to provide an estimate of the support of an image. This estimated support is then used as a constraint for maximum likelihood image reconstruction. This approach has robust noise performance and provides high reconstruction fidelity.

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: Simultaneous dual-isotope positron emission tomography (PET) is used to improve disease evaluation. Two distinct molecular probes are simultaneously provided to the imaging target. One of the probes is labeled with a radionuclide that emits positrons to provide double coincidence events in PET. The other probe is labeled with a radionuclide that emits positrons+prompt gammas to provide triple coincidence events in PET. One of the probes is a metabolic probe, and the other probe is a selective probe that includes a ligand or antibody that is biologically responsive to receptor/antigen status. A PET system is employed that can provide simultaneous double coincidence and triple coincidence PET images. The resulting images provide simultaneous metabolic imaging and receptor/antigen imaging. Applications include disease evaluation, such as cancer staging (e.g., for breast cancer, prostate cancer, etc.).

Abstract: Positron emission tomography (PET) systems suitable for use with dirty (positron+prompt gamma) emitters are provided. One or more prompt gamma detectors are added to the PET system, where the prompt gamma detectors are responsive to the prompt gammas provided by the dirty emitter, but are not responsive to 511 keV annihilation photons. The prompt gamma detectors can surround the imaging PET detector array and/or be disposed as end caps relative to a generally cylindrical PET detector array. The prompt gamma detectors need not provide spatial resolution, because coincidence events in the PET detector array are classified as 2-photon or 3-photon events depending on whether or not there is a time-coincident signal from the prompt gamma detectors. One application of this approach is dual isotope PET where distinct tracers labeled with clean and dirty positron emitters are simultaneously imaged.

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: 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: Compressed sensing (CS) estimation approaches rely on a priori sparsity to significantly reduce the number of samples needed to provide high sampling fidelity, relative to the normal Shannon-Nyquist limit. Accordingly, CS approaches are of considerable interest for detector multiplexing in applications which have inherently sparse signals (e.g., the two correlated photon detection events in PET imaging). However, CS approaches also tend to fare poorly in the presence of noise, which has limited their applicability in practice. In this work, we show that CS estimation can be used to provide an estimate of the support of an image. This estimated support is then used as a constraint for maximum likelihood image reconstruction. This approach has robust noise performance and provides high reconstruction fidelity.

Abstract: The present invention provides a method of reconstructing a tomographic image. In a first step, a tomographic image is forward-projected along a list of geometrical lines in a GPU. This list of geometrical lines may be list-mode event data acquired from a tomographic scanner. Alternatively, the list may be a list of weighted lines derived from a sinogram, a histogram, or a timogram acquired from a tomographic scanner. Next, the list of geometrical lines is back-projected into a 3-dimensional volume using the GPU. The results of the forward- and back-projection are then used to reconstruct the tomographic image, which is then provided as an output, e.g. to make the image available for further processing. Examples of output include storage on a storage medium and display on a display device.

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: 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.