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 method (70) of operation of a PET scanner (10) that determines the depth of interaction of the annihilation photons within the scintillator (32) in localizing a temporal photon pair along a line of response (LOR).

Abstract: Magnetic resonance (MR) imaging typically has excellent spatial resolution, but relatively poor temporal resolution. In contrast, positron emission tomography (PET) typically has excellent temporal resolution, but poor spatial resolution relative to MR. Resultantly, it is advantageous to use combined PET-MR imaging sequences to create hybrid or enhanced images that reap the benefits of both modalities. A contrast agent (80) that includes both a PET tracer (82) and MR contrast enhancement (86) can be used in such a combined modality setting. The contrast agent (80) also includes a targeting system (84) that allows the contrast agent (80) to pool in a region of interest.

Abstract: Methods and systems for signal communication in gamma ray detectors are provided. One gamma ray detector includes a scintillator block having a plurality of scintillator crystals and a plurality of light sensors coupled to the scintillator crystals and having a plurality of microcells. Each of the plurality of light sensors have a local summing point in each of a plurality of signal summing regions, wherein the local summing points are connected to the plurality of microcells. The plurality of light sensors also each include a main summing point connected to the plurality of local summing points, wherein the main summing point is located a same distance from each of the local summing points.

Abstract: A host lattice modified GOS scintillating material and a method for using a host lattice modified GOS scintillating material is provided. The host lattice modified GOS scintillating material has a shorter afterglow than conventional GOS scintillating material. In addition, a radiation detector and an imaging device incorporating a host lattice modified GOS scintillating material are provided. A spectral filter may be used in conjunction with the GOS scintillating material.

Abstract: An integrated circuit in a PET imaging system with a plurality of photo detectors is provided. A plurality of differential transimpedance amplifiers with differential inputs and differential outputs is provided, wherein differential inputs for each differential transimpedance amplifier of the plurality of differential transimpedance amplifiers are electrically connected to a photodetector.

Abstract: A multiplexing circuit for a positron emission tomography (PET) detector includes a delay circuit and a multiplexer communicating with the delay circuit. The delay circuit configured to receive a plurality of timing pickoff (TPO) signals from a plurality of positron emission tomography (PET) detector units, add a delay time to at least one of the plurality of TPO signals, and transmit the TPO signals based on the delay time to the multiplexer, the multiplexer configured to a multiplex the TPO signals and output a single TPO signal from the plurality of TPO signals to a Time-to-Digital Convertor (TDC). A method of operating a multiplexer and a imaging system including a multiplexer are also provided.

Abstract: A method for gain calibration of a gamma ray detector includes measuring signals generated by one or more light sensors of a gamma ray detector, generating one or more derived curves using the measured signals as a function of bias voltage and identifying a transition point in the one or more derived curves. The method also includes determining a breakdown voltage of the one or more light sensors using the identified transition point and setting a bias of the one or more light sensors based on the determined breakdown voltage.

Abstract: A positron emission tomography (PET) detector module includes an array of scintillation crystal elements and a plurality of photosensors arranged to at least partially cover the array of scintillation crystal elements. The photosensors are configured to receive light emitted from the array of scintillation crystal elements. The module includes a transparent adhesive arranged between the array of scintillation crystal elements and the plurality of photosensors. The transparent adhesive extends directly from a surface of at least one of the scintillation crystal elements to a surface of at least one of the photosensors and is configured to distribute the light emitted from one of the scintillation crystal elements to more than one of the photosensors. A method of manufacturing the module includes various steps utilizing a fixture. A PET scanner uses multiple modules arranged circumferentially around an area to be scanned.

Abstract: Provided is a positron emission tomography (PET) detector module using Geiger-mode avalanche photodiode (GAPD) as a photosensor. The PET detector module includes: a PET detector unit with a scintillation crystal detecting gamma rays emitted from a living body and converting them into a scintillation light and a first GAPD photosensor and a second GAPD photosensor each being connected to either end of the scintillation crystal and converting the scintillation light into an electrical signal; and a depth of interaction (DOI) decoding unit receiving the signals from the PET detector unit and comparing amplitude of the signals detected by the first GAPD photosensor and the second GAPD photosensor, thereby providing the depth information where the gamma rays are incident on the scintillation crystal (DOI). The disclosed PET detector module can provide improved energy resolution and additional DOI information while maintaining linearity.

Abstract: A PET or SPECT radiation detector module (50) includes an array of detectors (54, 58) and their associated processing circuitry are connected by a flexible cable having releasable connectors. A method of mounting and dismounting includes mounting a radiation detector array in a support structure in a diagnostic scanner, connecting one end of a flexible connector to the detector array, and connecting the other end of the flexible connector to its associated circuitry.

Abstract: Apparatuses, computer-readable mediums, and methods are provided. In one embodiment, a positron emission tomography (“PET”) detector array is provided which includes a plurality of crystal elements arranged in a two-dimensional checkerboard configuration. In addition, there are empty spaces in the checkerboard configuration. In various embodiments, the empty spaces are filled with passive shielding, transmission source assemblies, biopsy instruments, surgical instruments, and/or electromagnetic sensors. In various embodiments, the crystal elements and the transmission source assemblies simultaneously perform emission/transmission acquisitions.

Abstract: The subject of the invention is a strip device and method for determining the place and time of the gamma quanta interaction as well as the use of the device for determining the place and time of the gamma quanta interaction in positron emission tomography.

Abstract: To simultaneously image a plurality types of tracer molecules for a Compton image and a PET image. Provided is an imaging device comprising: a first Compton camera (10) for receiving one gamma ray emitted from an imaging target (900) administered by first probe having positron emitting nuclei and second probe having gamma ray emission nuclei; and a second Compton camera (20) which is arranged opposite to the first Compton camera (10) and receives another gamma ray emitted from the imaging target (900). The imaging device is also provided with: an imaging processor for distinguishing and reconstructing a PET image and a Compton image in accordance with the combination of the Compton cameras which detected the gamma rays; and a display for displaying the PET image and the Compton image in association respectively with the first and the second probes.

Abstract: An imaging system includes a magnetic resonance portion that produces an electric field and a second imaging portion, including a detector with a two dimensional array of detector tiles, wherein adjacent tiles along an axial direction are spaced apart by an electrically conductive material, which shields the tiles from the electric field. An imaging system includes a first imaging portion having a detector, which includes an array of scintillation crystals and a photo-sensor coupled to the array of scintillation crystals, wherein an output of the photo-sensor includes a unique ratio of information that identifies each crystal.

Abstract: The present technology describes various embodiments of positron emission tomography (PET) systems for use with mammography machines and associated devices and methods. In several embodiments, a PET system includes a tissue platform and one or more PET detection panels removably coupled to the mammography machine. The panels are configured to generally surround the tissue platform and obtain an approximately 360 degree data sample of tissue. The system can further include an output device configured to output the data sample for image reconstruction. In some embodiments, the system is configured to provide high resolution images, quantitative image accuracy, dynamic imaging, and/or biopsy guidance.

Abstract: A timing circuit that includes a first serializer/deserializer (SERDES) configured to receive a parallel rate clock signal and a system clock start signal from an imaging system and generate a first output, a second SERDES configured to receive a stop signal that is based on an output from the medical imaging system and generate a second output, and a timestamp calculator configured to utilize the first and second outputs to generate a timestamp. A medical imaging system and a method of operating a timing circuit are also described.

Abstract: A method of configuring a time-of-flight positron emission tomography (PET) system includes determining a set of parameters of a detector of the PET system. Each parameter is configured to affect photon travel within the detector. The method further includes simulating operation of the detector to generate a photon detection timing data profile for a plurality of depth of interaction (DOI) positions within the detector via a simulation model of the detector configured in accordance with the set of parameters, and determining a time-of-flight correction factor for each DOI position of the plurality of DOI positions based on the simulated operation. The correction factor is indicative of a time offset of the photon detection timing data profile.

Abstract: A continuous time-of-flight scatter simulation method is provided, with a related method of correcting PET imaging data to compensate for photon scatter. Scatter contributions from each imaging pixel in a field of view may be calculated without binning data.

Abstract: A method and apparatus for determining a coincidence window for imaging a region of interest of an object using a Positron Emission Tomography (PET) scanner. The method includes determining a diameter of a transverse field of view (FOV) for imaging the region of interest of the object; and calculating the coincidence window based on the determined diameter, a ring diameter of the PET scanner, an axial length of the PET scanner, and a time-of-flight resolution of the PET scanner.

Abstract: A method and system for nuclear imaging normally involves detection of energy by producing bursts of photons in response to interactions involving incident gamma radiation. The detector sensitivity is increased by as much as two orders of magnitude, so that some excess sensitivity can be exchanged to achieve unprecedented spatial resolution and contrast-to-noise (C/N) ratio comparable to those in CT and MRI. Misplaced pileup events due to scattered radiation are rejected for each of the central groups to reduce image blurring, thereby further improving image quality. The reduction in detector thickness minimizes depth-of-interaction (DOI) blurring as well as blurring due to Compton-scattered radiation. The spatial sampling of the detector can be further increased using fiber optic coupling to reduce effective photodetector size. Fiber-optic coupling also enables to increase the packing fraction of PMTs to 100% by effectively removing the glass walls.

Abstract: A method is disclosed for generating a PET or SPECT image dataset. In an embodiment, the method includes acquiring a plurality of PET or SPECT measurement signals from an examination region; acquiring a plurality of anatomy image datasets that show the examination region using a second imaging modality at the same time as acquiring the PET or SPECT measurement signals; determining the similarity of a reference anatomy image dataset acquired at a time point t? using the second imaging modality to at least one anatomy image dataset acquired at a different time point and/or predetermining a temporal weighting function; and generating a PET or SPECT image dataset taking into account the similarity of the anatomy image datasets and/or weighting the PET measurement signals temporally. A hybrid imaging modality is also disclosed.

Abstract: A method for using lutetium-based scintillator crystals' background beta decay emission in a positron emission tomography (PET) scanner as a transmission scan source for generating attenuation maps is disclosed.

Abstract: An apparatus for generating an image may include a plurality of scintillator layers configured to convert an incident beam into an optical signal; a plurality of micro cells configured to turn on or off depending on whether or not the micro cells detect the optical signal; a reaction depth determining unit configured to detect a decay pattern of the optical signal, on the basis of on/off signals of the micro cells, and configured to determine a type of the scintillator layers with which the incident beam has reacted; and/or a reading unit configured to decide an occurrence location of the incident beam and then generates a photographed image.

Abstract: Timing is determined in positron emission tomography (PET). Two or more different types of timing detection are used for each event. The difference in time from the different types of timing detection may indicate whether or not an error has occurred. An average difference or other typical offset difference may be used to correct the error. During pile up, the difference information may be used to create a missing time, such as using an average difference between second derivative and constant fraction discrimination as an offset to determine constant fraction timing from second derivative timing.

Abstract: A method of correcting a timing signal that represents an arrival time of a photon at a positron emission tomography (PET) detector includes receiving a timing signal that represents an arrival time of a photon at a PET detector, receiving an energy signal indicative of an energy of the photon, calculating a timing correction using the energy signal, modifying the timing signal using the timing correction, and generating an image of an object using the modified timing signal. A system and non-transitory computer readable medium are also described herein.

Abstract: A radiation detector module for use in nuclear medical imagers employing radiation transmission or radiopharmaceuticals includes a rigid, optically opaque grid defined around a plurality of scintillator crystals. The grid defines a plurality of cells in which each scintillator crystal is completely disposed within in such a manner that an air layer exists between the scintillator crystal and the walls of the grid. A plurality of photoelectric detectors, each of which is associated with a corresponding scintillator crystal, are optically coupled to corresponding scintillator crystals by an optical coupling layer disposed within the cell.

Abstract: An apparatus that can measure images of at least a portion of an eye and record data sets indicative of a neurological condition. A method interrelates an image and a data set to provide an interpretive result. The apparatus and method thereby provide guidance as to the presence of a medical condition in a patient. The apparatus and method can be used in an iterative measurement process, in which the apparatus attempts to discern normal health from a state of health that is not normal health. If the interpretive result is consistent with normal health, the process terminates, information is recorded, and an optional report is given. If the interpretive result is not consistent with normal health, the apparatus and method attempts to distinguish which condition is consistent with the data and images used, and can iterate with additional measurements and information to attempt to provide a useful interpretive result.

Abstract: A photon detector (10) includes a detector array (12) comprising single photon avalanche diode (SPAD) detectors (14) configured to break down responsive to impingement of a photon. Trigger circuitry (34) is configured to generate a trigger signal responsive to break down of a SPAD detector of the detector array. Latches (20, 22) are configured to store position coordinates of SPAD detectors of the detector array that are in break down. The latches are configured to latch responsive to a trigger signal generated by the trigger circuitry. The latches may include row latches (22) each connecting with a logical “OR” combination of SPAD detectors of a corresponding row of the detector array, and column latches (20) each connecting with a logical “OR” combination of SPAD detectors of a corresponding column of the detector array. Time to digital converter (TDC) circuitry (28) may generate a digital time stamp for the trigger signal.

Abstract: A method for imaging is providing, including administering a teboroxime species to an adult human subject, administering TI-201-thallous chloride to the subject, performing a teboroxime species SPECT imaging procedure of the teboroxime species on a region of interest (ROI) of the subject, and, after administering the teboroxime species, performing a TI-201-thallous chloride SPECT imaging procedure of the TI-201-thallous chloride on the ROI. Administering the teboroxime species and the TI-201-thallous chloride and performing the teboroxime species and the TI-201-thallous chloride SPECT imaging procedures comprise administering the teboroxime species and the TI-201-thallous chloride and performing the teboroxime species and the TI-201-thallous chloride SPECT imaging procedures during a time period having a duration of no more than 30 minutes. Other embodiments are also described.

Abstract: Systems, devices, processes, and algorithms for adapting and/or adjusting a reflectivity of a reflector in a radiation detector. The reflectivity can be changed by a reflectivity control signal that is generated based on an estimated count rate of events so as to adjust a probability of a photosensor detecting light resulting from the event via, for example, a scintillation event. By adjusting the probability, an energy resolution of the radiation detector can be optimized. The reflectivity of a reflector can be changed by changing a state of a thin film, a liquid crystal layer, or a suspended magnetic particle layer.

Abstract: A mobile PET imager and method for the same is provided. The mobile PET imager includes a plurality of detector modules forming a ring detector, each for nuclear radiation detection. The imager may include a plurality of attenuation source housings including sources for attenuation such that each attenuation source housing is placed between two of the detector modules. A plurality of channel cards for processing data from the plurality of detector modules may be in the imager so that each channel card is shared by more than one of the detector modules. The imager may include at least one channel card for processing data from the detector modules and at least one resistor network acting as preamplifier, coupling to the detector modules and the channel card such that the channel card is mounted on the detector module in layer.

Abstract: Using standard or “off the shelf” cable to interconnect between the PET block detector and the detector circuit may save substantial costs given the number of PMTs in a PET system. Given space constraints, simple maintenance with reduced risk of disturbing cabling is desired, making ongoing use of standard cabling without adding further cabling desired. To implement digital gain control, a further communication is provided between the PET detector block and the detector circuit. Since the standard cable may not have additional wires for such communications and to reduce timing degradation, the PMT signals are combined, such as generating position and energy signals at the PET detector block. The four PMT signals are reduced to three signals without reduction in function, allowing a fourth twisted pair of wires in a CAT5 cable to be used for digital gain control.

Abstract: Disclosed herein are a system, method, and computer-readable storage medium for determining a time pickoff for both digital and analog photomultiplier circuits. Rather than basing time pickoff on the leading edge of a photomultiplier signal crossing a threshold or the first signal from a digital photomultiplier, a method for more accurate time calculations is disclosed. The system searches for peak values associated with the signal using differentiation, peak hold searching, and Gaussian distributions. Based on these calculations and comparisons, a more accurate time pickoff is determined.

Abstract: A data processing unit for an integrated magnetic resonance (MR) and positron emission tomography (PET) system includes an RF shield housing, a first input port in the RF shield housing configured to receive a PET detector signal, a first filter disposed in the RF shield housing, in communication with the first input port, and configured to remove MR noise from the PET detector signal, a second input port in the RF shield housing configured to receive DC power, a second filter disposed in the RF shield housing, in communication with the second input port, and configured to remove the MR noise from the DC power, and a signal processing circuit disposed in the RF shield housing and powered by the DC power, the signal processing circuit including an analog-to-digital converter to digitize the PET detector signal.

Abstract: In the nuclear medicine imaging apparatus according to the one embodiment, the ADC converts the output data of each of the photodetectors to digital data. The counting information collecting unit collects counting results from the digital data, and the counting information storage unit stores the counting result in association with the digital data. The coincidence counting information generating unit generates coincidence counting information. The image reconstructing unit reconstructs a PET image, based on the coincidence counting information. The time correction data stores a correction time for each of the photodetectors. The system controlling unit controls to correct the detection time of the gamma rays in the digital data associated with each piece of the counting information by use of the correction time, and to generate new coincidence counting information. The system controlling unit controls to reconstruct a new nuclear medicine image, based on the new coincidence counting information generated.

Abstract: A method for estimating a line or response in a positron emission tomography scanner having depth of interaction estimation capability. The method utilizes information from both detector modules detecting a coincident event. A joint probability density function combining factors accounting for intermediate Compton scattering interactions and/or a final interaction that may be either a Compton scattering interaction or photoelectric absorption is calculated. In a preferred embodiment, a Bayesian estimation scheme is used to integrate the PDF for all permutations of the measured signal pairs, and the permutation with the largest joint probability is selected to construct the estimated line of response.

Abstract: A photosensor gain detection apparatus that includes a detector including a photosensor configured to output a signal. Also included in the apparatus is an after-pulse/dark-pulse detector device that detects an after-pulse or a dark-pulse in the signal output by the photosensor, and outputs an indication signal when the after-pulse or the dark-pulse is detected, the after-pulse and the dark-pulse representing after-events in the photosensor triggered from a previous photon generating event. The apparatus additionally includes an integrator device that integrates the signal output by the photosensor and to output an integrated signal, a histogram device connected to the integrator and the after-pulse/dark-pulse detector device, and that generates a histogram from the integrated signal and the indication signal, a gain determination device that determines a gain of the photosensor based on the generated histogram, and a memory configured to store the determined gain.

Abstract: A method of arranging detector modules within a gamma ray detector apparatus, each detector module including an array of scintillation crystals to convert light into electrical signals, the light being generated in response to incident gamma rays generated by an annihilation event, the method including obtaining performance information of each of the detector modules, and determining a relative location for each of the detector modules within the gamma ray detector based on the obtained performance information of the detector modules.

Abstract: Described herein are adaptors and other devices for radiation detectors that can be used to make accurate spectral measurements of both small and large bulk sources of radioactivity, such as building structures, soils, vessels, large equipment, and liquid bodies. Some exemplary devices comprise an adaptor for a radiation detector, wherein the adaptor can be configured to collimate radiation passing through the adapter from an external radiation source to the radiation detector and the adaptor can be configured to enclose a radiation source within the adapter to allow the radiation detector to measure radiation emitted from the enclosed radiation source.

Abstract: An optical device (102) configured for concentrating light towards a target element (104) is provided. The optical device (102) comprises a waveguide element (106) configured for guiding light towards the target element (104), and a wavelength conversion element (108) configured for converting incoming light of a first wavelength into outgoing light of a second wavelength. The wavelength conversion element (108) extends adjacent to the waveguide element (106). An interface (114) between the waveguide element (106) and the wavelength conversion element (108) comprises a surface roughness. The latter may provide for an in creased efficiency and low manufacturing costs of the optical device (102).

Abstract: A positron emission tomography (PET) detector module includes an array of scintillation crystal elements and a plurality of photosensors arranged to at least partially cover the array of scintillation crystal elements. The photosensors are configured to receive light emitted from the array of scintillation crystal elements. The module includes a transparent adhesive arranged between the array of scintillation crystal elements and the plurality of photosensors. The transparent adhesive extends directly from a surface of at least one of the scintillation crystal elements to a surface of at least one of the photosensors and is configured to distribute the light emitted from one of the scintillation crystal elements to more than one of the photosensors. A method of manufacturing the module includes various steps utilizing a fixture. A PET scanner uses multiple modules arranged circumferentially around an area to be scanned.

Abstract: Provided are time-of-flight positron emission tomography devices comprising a detector array having at least two segments configured to accommodate a body part and to acquire tracer emission signals from a target within an imaging situs with a timing resolution of less than about 600 ps and a processor that receives the acquired signals from the detector array and converts the signals into a three dimensional image reconstruction of the target.

Abstract: A method for reconstructing an image from emission data includes generating a compressed point-spread function matrix, generating an accumulated attenuation factor; and performing at least one image projection operation on an image matrix of the emission data using the compressed point-spread function matrix and the accumulated attenuation factor. The image projection operation can include rotating an image matrix and an exponential attenuation map to align with a selected viewing angle. An accumulated attenuation image is then generated from the rotated image matrix and rotated exponential attenuation map and a projection image is generated for each voxel by multiplying the accumulated attenuation image and point spread function matrix for each voxel. The rotating and multiplying operations can be performed on a graphics processing unit, which may be found in a commercially available video processing card, which are specifically designed to efficiently perform such operations.

Abstract: When employing specular reflective material in a scintillator crystal array, light trapping in the crystal due to repetitive internal reflection is mitigated by roughening at least one side (16) of each of a plurality of pre-formed polished scintillator crystals. A specular reflector material (30) is applied (deposited, wrapped around, etc.) to the roughened crystals, which are arranged in an array. Each crystal array is coupled to a silicon photodetector (32) to form a detector array, which can be mounted in a detector for a functional scanner or the like.

Abstract: In a coincidence determination of a PET device, the PET device uses a scintillator of radioactive isotope containing background noise due to intrinsic radioactivity as a radiation detector. The PET device counts a pair of annihilation radiations that is assumed to occur from a same nuclide. The annihilation radiations are detected within a predetermined coincidence time window by a plurality of radiation detectors. The method includes determining a coincidence with a wide energy window that allows detecting the background noise due to intrinsic radioactivity as multiple coincidences; removing the multiple coincidences; and using an energy window narrower than the wide energy window to limit a coincidence event to a coincidence event in a photopeak from a positron nuclide only.

Abstract: Systems and methods are described herein for performing three-dimensional imaging using backscattered photons generated from a positron-electron annihilation. The systems and methods are implemented using the pair of photons created from a positron-electron annihilation. The trajectory and emission time of one of the photons is detected near the annihilation event. Using this collected data, the trajectory of the second photon can be determined. The second photon is used as a probe photon and is directed towards a target for imaging. The interaction of the second probe photon with the target produces back scattered photons that can be detected and used to create a three-dimensional image of the target. The systems and methods described herein are particularly advantageous because they permit imaging with a system from a single side of the target, as opposed to requiring imaging equipment on both sides of the target.

Abstract: A radiation detector is provided that allows correction so as to identify incident gamma-ray positions accurately with no influence of afterglow of fluorescence. The radiation detector includes an intensity-data acquiring section for acquiring intensity data representing intensity of fluorescence outputted from a light detector for every temporally-constant sampling interval, and a correction-value acquiring section section for acquiring a correction value used for correction of variations in intensity data resulting from afterglow of the fluorescence. In addition, the radiation detector includes an integrating section for correcting the intensity data using the correction value. This allows correct calculation of the integrated value m with no influence of the afterglow of fluorescence.

Abstract: Systems and methods of generating timing triggers to determine timing resolutions of gamma events for nuclear imaging includes receiving a pulse signature representing a succession of triggers associated with a photomultiplier. When a number of triggers occurring within a predetermined time interval matches a predetermined number, an event trigger can be initiated. A delayed version of the pulse signature can be generated and compared to a predetermined timing trigger level. When the delayed version matches the predetermined timing trigger level, a timing trigger can be generated. Based on the timing trigger level, the timing trigger can be generated at the pulse of the delayed version that corresponds to the first photoelectron of a gamma event. The timing trigger can correspond to a timestamp for the first photoelectron so that a data acquisition system can identify the pulse from which to acquire energy information to generate a nuclear image.

Abstract: A detector (22) detects an event. First and second time-to-digital converters (TDCs) (70, 72) generate first and second time stamps (TS1, TS2) for the detection of the event. The first TDC and the second TDC are both synchronized with a common clock signal (62) that defines a fixed time offset between the second TDC and the first TDC. An autocalibration circuit (120) adjusts the first TDC and the second TDC to keep the time difference between the second time stamp and the first time stamp equal to the fixed time offset between the second TDC and the first TDC. The detector may be a detector array, and trigger circuitry (28) propogates a trigger signal from a trigger detector of the array of detectors to the first and second TDC's. Skew correction circuitry (132, 134, 136, 142, 60, 162) adjusts a timestamp (TS) based on which detector is the triggering detector.