Uptake of hypoxia-sensitive PET tracers is dependent on tissue transport properties, specifically, distribution volume. Variability in tissue transport properties reduces the sensitivity of static PET imaging to hypoxia. When tissue transport (v.sub.d) effects are substantial, correlations between the two methods of determining hypoxic fractions are greatly reduced—that is, trapping rates k.sub.3 are only modestly correlated with tumour-to-blood ratio (TBR). In other words, the usefulness of dynamic- and static-PET based hypoxia surrogates, trapping rate k.sub.3 and TBR, in determining hypoxic fractions is reduced in regions where diffusive equilibrium is achieved slowly. A process is provided for quantifying hypoxic fractions using a novel biomarker for hypoxia, hypoxia-sensitive tracer binding rate k.sub.b, based on PET imaging data. The same formalism can be applied to model the kinetics of non-binding CT and MT contrast agents, giving histopathological information about the imaged tissue.

An X-ray detector is positioned relative to an X-ray source such that at least a part of a region between the X-ray source and the X-ray detector is an examination region for accommodating an object. The X-ray source and X-ray detector are controlled by a processing unit in order to operate in a first imaging operation mode, a second imaging operation mode, and/or a third imaging operation mode. The detector comprises a first scintillator, a second scintillator, a first sensor array, and a second sensor array. The first scintillator is disposed over the second scintillator such that X-rays emitted from the X-ray source first encounter the first scintillator and then encounter the second scintillator.

A non-transitory computer-readable medium stores instructions readable and executable by a workstation (18) including at least one electronic processor (20) to perform an image reconstruction method (100) to reconstruct list mode data acquired over a frame acquisition time using a plurality of radiation detectors (17) in which the events of the list mode data is timestamped. The method includes: for the sub-frame bins of a plurality of sub-frame bins into which the frame acquisition time is divided, determining a sub-frame singles rates map for the plurality of radiation detectors from the list mode data whose time stamps reside in the sub-frame bin; determining a singles rate for the singles events of the list mode data using the sub-frame singles rates maps wherein the singles rates for the singles events are determined at a temporal resolution that is finer than the frame acquisition time; determining correction factors for the list mode data using the determined singles rates for the singles events of the list mode data; and reconstructing the list mode data of the frame acquisition time using the determined correction factors to generate a reconstructed image for the frame acquisition time.

The invention relates to a system for imaging an object in an x-ray imaging mode and in a gamma imaging mode. A radiation detector (1) of the system comprises a conversion unit (202) including a plurality of detector pixels (206.sub.1, . . . ,M) and generating for each detection event a detection signal indicative of an energy of the event, and a counting unit (203) including for each detector pixel (206.sub.1, . . . ,M) a plurality of comparators (209.sub.i; 1, . . . ,N) and associating each detection event to one of a plurality of predetermined energy bins based on the detection signals using the comparators (209.sub.i; 1, . . . ,N). In the x-ray imaging mode, the comparators (209.sub.i; 1, . . . ,N) of one pixel (206.sub.1, . . . ,M), and in the gamma imaging mode, the comparators (209.sub.i; 1, . . . ,N) of several pixels (206.sub.1, . . . ,M) are available for the association so that more energy bins are available in the gamma imaging mode than in the x-ray imaging mode.

The invention relates to a combined detector (660) comprising a gamma radiation detector (100) and an X-ray radiation detector (661). The gamma radiation detector (100) comprises a gamma scintillator array (101.sub.x, y), an optical modulator (102) and a first photodetector array (103.sub.a, b) for detecting the first scintillation light generated by the gamma scintillator array (101.sub.x, y). The optical modulator (102) is disposed between the gamma scintillator array (101.sub.x, y) and the first photodetector array (103.sub.a, b) for modulating a transmission of the first scintillation light between the gamma scintillator array (101.sub.x, y) and the first photodetector array (103.sub.a, b). The optical modulator (102) comprises at least one optical modulator pixel having a cross sectional area (102′) in a plane that is perpendicular to the gamma radiation receiving direction (104). The cross sectional area of each optical modulator pixel (102′) is greater than or equal to the cross sectional area of each photodetector pixel (103′.sub.a, b).

The present disclosure relates to a new positron emission tomography (PET) scanning method that generates images with improved spatial resolution. The method includes placing a plurality of radiation-attenuating rods in a parallel arrangement near the target region of a patient, where the rods are in a first orientation with respect to the patient and conducting one or more PET scans of the target region generating a projection data that includes the radiation-attenuating rods, and reconstructing an image of the target region from the projection data.

Detector systems for enhanced radiographic imaging incorporate x-ray CT imaging capabilities. The detector designs employ a layer of detector modules comprised of edge-on or face-on detectors, or a combination of edge-on and face-on detectors, and may employ structured detectors. The detectors can operate in a non-coincidence or coincidence detection mode.

The invention relates to a combined imaging detector for detection of gamma and x-ray quanta comprising an x-ray detector (31) for generating x-ray detection signals in response to detected x-ray quanta and a gamma detector (32) for generating gamma detection signals in response to detected gamma quanta. The x-ray detector (31) and the gamma detector (32) are arranged in a stacked configuration along a radiation-receiving direction (33). The gamma detector (32) comprises a gamma collimator plate (320) comprising a plurality of pinholes (321), and a gamma conversion layer (322, 324) for converting detected gamma quanta into gamma detection signals.

The present invention relates to a system for X-ray imaging It is explained to position (210) an X-ray detector (10) relative to an X-ray source such that at least a part of a region between the X-ray source and the X-ray detector is an examination region for accommodating an object. The X-ray source and X-ray detector are controlled (220) by a processing unit in order to: operate (230) in a first imaging operation mode; or operate (240) in a second imaging operation mode; or operate (250) in the first imaging mode and in the second imaging mode; or operate (260) in a third imaging operation mode. The detector comprises a first scintillator (20), a second scintillator (30), a first sensor array (40), and a second sensor array (50). The first sensor array is associated with the first scintillator. The first sensor array comprises an array of sensor elements configured to detect optical photons generated in the first scintillator. The second sensor array is associated with the second scintillator. The second sensor array comprises an array of sensor elements configured to detect optical photons generated in the second scintillator. The first scintillator is disposed over the second scintillator such that X-rays emitted from the X-ray source first encounter the first scintillator and then encounter the second scintillator. The first scintillator has a thickness equal to or greater than 0.6 mm. The second scintillator has a thickness equal to or greater than 1.1 mm. In the first imaging operation mode the first scintillator and the first sensor array are configured to provide data useable to generate a low energy X-ray image. In the second imaging operation mode the second scintillator and the second sensor array are configured to provide data useable to generate a high energy X-ray image. In the third imaging operation mode the first scintillator, the first sensor array, the second scintillator and the second sensor array are configured to provide data useable to generate a combined energy X-ray image.

A non-transitory computer-readable medium stores instructions readable and executable by a workstation (18) including at least one electronic processor (20) to perform an image reconstruction method (100) to reconstruct list mode data acquired over a frame acquisition time using a plurality of radiation detectors (17) in which the events of the list mode data is time stamped. The method includes: for the sub-frame bins of a plurality of sub-frame bins into which the frame acquisition time is divided, determining a sub-frame singles rates map for the plurality of radiation detectors from the list mode data whose time stamps reside in the sub-frame bin; determining a singles rate for the singles events of the list mode data using the sub-frame singles rates maps wherein the singles rates for the singles events are determined at a temporal resolution that is finer than the frame acquisition time; determining correction factors for the list mode data using the determined singles rates for the singles events of the list mode data; and reconstructing the list mode data of the frame acquisition time using the determined correction factors to generate a reconstructed image for the frame acquisition time.