Methods and systems are provided for correcting positional errors in an image arising from gaps in a detector assembly. In one embodiment, a method comprises generating a sinogram based on a plurality of photon coincidence events, selectively inserting one or more pseudo-slices into the sinogram, and generating an image based on the sinogram including the one or more pseudo-slices. In this way, positional errors may be reduced without modifying an image reconstruction algorithm to include a full detector geometry or modifying the detector geometry itself.

The present invention relates to a Compton imaging apparatus and a single photon emission and positron emission tomography system comprising the Compton imaging apparatus and, more specifically, to a Compton imaging apparatus based on a single scintillator and a single photon emission and positron emission tomography system including the Compton imaging apparatus. The Compton imaging apparatus according to the present invention may reconstruct a Compton image based on the single scintillator composed of a plurality of scintillation cells. Thus, the Compton imaging apparatus of the present invention is cheaper than any other Compton imaging apparatuses and has an excellent time resolution such that the Compton imaging apparatus can be used even in a high-radiation area. Also, the single photon emission and positron emission tomography system using the Compton imaging apparatus can improve radiation detection efficiency and an image resolution, to thereby improve image quality.

Gamma cameras may be used to obtain two-dimensional images of an emitting object, of which the most common form is the Anger-type gamma camera. The primary components in a conventional Anger-type gamma camera include, but are not limited to: a plurality of photo-multiplier tubes, a scintillator material, and a collimator. The disclosed invention claims a novel use of a gamma camera which eliminates the collimator. The new method is a method of forming an initial image from the incident radiation, which does not depend on any mechanical or other means of restricting the incident radiation to be passed on to a position-sensitive radiation detector. This method then uses mathematical deconvolution to produce an image of the object without the need for a collimator and without reliance on a pre-existing image.

[Problem to be Solved] To improve stability of automatic normalization of a bone scintigraphy image.

[Solution] A preferred embodiment includes: creating a pixel value histogram of image data representing a bone scintigraphy image; setting a plurality of thresholds related to pixel values based on the pixel value histogram; calculating respective average pixel values for the set thresholds; arranging the calculated average pixel values in order from the largest value; and determining a reference value for normalizing the image data based on at least part of a set of the average pixel values arranged in the order. The determining the reference value includes: determining one straight line that approximates a region of small average pixel values out of the set of the average pixel values arranged in the order; and calculating the reference value based on the straight line.

A method of operation of a scintillator detector comprising a scintillator and a photodetector is described, together with a device embodying the method. The method comprises the steps of: periodically producing a light pulse; impinging at least some of the light from a successive plurality of such light pulses onto a light-receptive part of the photodetector; measuring the electrical response of the photodetector; processing the electrical response of the photodetector to determine a pulse height and a variance of pulse height; numerically processing the pulse height and variance of pulse height so determined to obtain at least a first data item characteristic of the response of the photodetector. The method additionally or alternatively comprises the steps of: periodically producing a light pulse including light in the ultraviolet spectrum; impinging at least some of the UV light from a successive plurality of such light pulses onto a light-receptive part of the scintillator; inducing photon emission in the scintillator in the visible spectrum; measuring the electrical response of the scintillator; processing the electrical response of the scintillator to obtain at least a data item characteristic of the response of the scintillator; and optionally verifying the electrical response of the scintillator by comparing at least the said data item against a predetermined reference response; and optionally additionally or alternatively outputting a control signal to the photodetector, which signal is modified in part responsive at least to the value of the said data item.

A signal detected by a photomultiplier tube is pre-amplified and converted into a digital signal. A time average value of signal components, each of which has a voltage lower than a predetermined base threshold value, is calculated as a base voltage. A signal that has been subjected to base correction processing is subjected to threshold value processing and to base correction processing in a non-incident state in which light is not incident on the photomultiplier tube. An output signal thereof is subjected to dark current calculation processing; and a light emission signal amount is calculated by subtracting, from the signal component of the detection light obtained by the threshold value processing, a time average value of the signal components of the dark current. As the result, discriminating the dark current pulse from floor noises enhances the accuracy of the base voltage, and thus the accuracy of light detection.

For calibration (24) for quantitative SPECT, a multiple energy emission source (11) is used for calibration. The planar sensitivities and/or uniformities are determined at different emission energies based on detections from the multiple energy emission source. For estimating (32) the activity concentration, sensitivities and/or uniformities based on measures (26) at different emission energies increase accuracy. The multiple energy emission source (11) may alternatively or additionally be used to calibrate (40) a dose calibrator (15).

A method for determining the position of a scintillation event in a radiation particle detector with multiple scintillator element locations which are configured to emit a burst of photons responsive to a radiation particle being absorbed at the scintillator element location and with a plurality of photosensors (5.1, 5.2, 5.3, 5.4) optically coupled to said scintillator element locations, comprising the steps of determining, for each of the photosensors (5.1, 5.2, 5.3, 5.4), a triggering probability indicative of the probability of said photosensor (5.1, 5.2, 5.3, 5.4) measuring a number of photons that exceeds a predetermined triggering threshold; measuring a photon distribution with the photosensors (5.1, 5.2, 5.3, 5.4) indicative of the number of photons incident on the individual photosensors (5.1, 5.2, 5.3, 5.4); calculating, for each of the scintillator element locations, a likelihood that a scintillation event with a predetermined energy value took place in said scintillator element location based on the measured photon distribution and the triggering probability of each of the photosensors (5.1, 5.2, 5.3, 5.4); and identifying the scintillator element location having the maximum likelihood.

Model-based scatter correction is used in SPECT with a non-parallel-hole collimator. Model-based scatter correction uses scatter kernels based on simulation to model the scatter for a given system and patient. For non-parallel-hole collimators, the measured sensitivity and measured vector maps are used in the modeling of scatter. The measured sensitivity is used to normalize the scatter kernels simulated for a parallel-hole collimator rather than attempting to simulate scatter with the complicated arrangement of holes. The measured vector maps are used to accurately project the model-based scatter sources into a data or emissions space.

A method for determining the position of a scintillation event in a radiation particle detector with multiple scintillator element locations which are configured to emit a burst of photons responsive to a radiation particle being absorbed at the scintillator element location and with a plurality of photosensors (5.1, 5.2, 5.3, 5.4) optically coupled to said scintillator element locations, comprising the steps of determining, for each of the photosensors (5.1, 5.2, 5.3, 5.4), a triggering probability indicative of the probability of said photosensor (5.1, 5.2, 5.3, 5.4) measuring a number of photons that exceeds a predetermined triggering threshold; measuring a photon distribution with the photosensors (5.1, 5.2, 5.3, 5.4) indicative of the number of photons incident on the individual photosensors (5.1, 5.2, 5.3, 5.4); calculating, for each of the scintillator element locations, a likelihood that a scintillation event with a predetermined energy value took place in said scintillator element location based on the measured photon distribution and the triggering probability of each of the photosensors (5.1, 5.2, 5.3, 5.4); and identifying the scintillator element location having the maximum likelihood.