Patent Description:
Nuclear medical imaging, one of the most important technical means for disease diagnosis in modem medicine, is capable of acquiring diagnostic information of diseases by observing metabolism in an organ of organisms non-invasively on a basis of distribution of radiopharmaceutical, obtained by detecting, outside a patient's body, X-rays or gamma photons emitted from radionuclides, which are labeled on molecules involving in physiological metabolism in the organisms, and by image reconstruction. In the field of nuclear medical imaging, the two most important imaging systems are Positron Emission Tomography (PET) and Single-Photon Emission Computed Tomography (SPECT), which are now widely used in clinical examination and diagnosis of diseases, including cancers, neurological diseases and cardiovascular diseases.

Core components of PET consist of several gamma photon detector modules with time measurement functions and corresponding time coincidence modules. The basic principle of PET involves electronic collimation technology and the radionuclides used therein are positron nuclides. The positrons, emitted by the positron nuclides, annihilates in the body of the organisms, generating a pair of gamma photons in almost opposite directions each with an energy of <NUM> keV. With time coincidence measurement, i.e., if a pair of gamma photons each with an energy of <NUM> keV are detected by two gamma photon detector modules within a very short period of time (usually within a few nanoseconds) respectively, the two photons are regarded as annihilation photons and it is possible to determine a line of response (LOR) where positron annihilation occurs (approximate to where decay of positron nuclides takes place). With record of a large number of such LORs, a distribution of locations where positron annihilations occur (approximate to the distribution of positron nuclides in the organisms) can be obtained through the image reconstruction. As emission directions of the pair of gamma photons generated by the positron annihilation are almost opposite, it is only possible to determine that the positron annihilation occurs along the corresponding LOR, but impossible to determine a specific location where the positron annihilation takes place at the corresponding LOR. Although it is possible to preliminary determine a position range where the positron annihilation occurs at the corresponding LOR through Time-of-Flight (TOF) measurement technology, the gamma photon detector modules are required to have extremely high time resolution. As the location where the positron annihilation occurs at the corresponding LOR is uncertain, the signal-to-noise ratio (SNR) of the reconstructed image showing the distribution of the positron nuclides in the organisms is often low, which adversely affects the diagnostic effect. In order to improve the image SNR, it is usually required to accumulate a large number of LORs, which needs a patient to intake a relatively high dose of positron nuclides, thereby increasing irradiation risk to the patient.

Core components of SPECT include a collimator, a gamma photon detector module and the like. SPECT involves a physical collimation technique and nuclides used therein are gamma photon nuclides. The collimators are usually arranged in front of the gamma photon detector module to limit the angle at which a gamma photon emitted by the gamma photon nuclides reaches the detector module, such that the gamma photon emitted only along a series of specific directions can pass through the collimator and be detected by the detector module. Every time a gamma photon is detected by the gamma photon detector, it is possible to determine a projection line where the gamma photon is initially emitted. Accordingly, distribution of initial emission locations of gamma photons (i.e., distribution of nuclides emitting gamma photon in the organisms) can be determined by accumulation of a large number of such projection lines and image reconstruction. Similar to PET, SPECT cannot determine a specific location where the gamma photon is emitted at the projection line, and thus the SNR of the reconstructed image is poor. Further, as the collimator is used in SPECT, which limits the angle at which the gamma photon emitted can be detected by the gamma photon detector, resulting in a low detection efficiency, which further deteriorates the SNR of the reconstructed image.

<CIT> relates to systems and methods for determining an approximate location of a radionuclide at a time of its radioactive decay are described. The method comprises introducing into a target region a radionuclide that, at the time of its radioactive decay, emits a positron and a primary photon, detecting the primary photon at a first one of a plurality of photon detectors and detecting at least one secondary photon emitted from an annihilation of the position at least a second one of the plurality of photon detectors, and determining the approximate location of the radionuclide at the time of its radioactive decay based on a location of the first one of the plurality of photon detectors, a location of the second one of the plurality of photon detectors, and a presumed common point of origin of the detected primary photon and the detected at least one secondary photon.

Preferred embodiments are included as dependent claims.

In embodiments of the present disclosure, there are provided an imaging system based on multiple-gamma photon coincidence events, a device and a non-transitory computer storage medium, aiming at improving detection efficiency of the imaging system and the SNR of a reconstructed image.

In an embodiment of an aspect of the present disclosure, there is provided an imaging system based on multiple-gamma photon coincidence events, including:.

The imaging system of the present disclosure positions where the decay of the radionuclide takes place by determining via calculation a point to which the sum of individual distances from two or more non-parallel projection lines is minimum, and acquires the distribution of the radionuclide in the organism, which effectively overcomes shortcomings of the conventional PET or SPECT system that it is only possible to determine an LOR or a projection line where the decay of the radionuclide takes place, but impossible to determine a specific location where the decay of the radionuclide takes place at the LOR or the projection line. As the location where the decay of the radionuclide takes place can be determined via calculation based on several non-parallel projection lines, the image reconstruction algorithm is simplified and the SNR of the reconstructed image is improved. At the same time, there is no need to accumulate a large number of projection lines to reconstruct a spatial distribution of radionuclides, thereby reducing the total demand for gamma photon events, the intake amount of radiopharmaceutical by the patient, and the radiation risk to the patient to a certain extent.

These and other aspects and advantages of embodiments of the present disclosure will become apparent and more readily appreciated from the following descriptions made with reference to the drawings, in which:.

With reference to the drawings and examples, an imaging system and method based on multiple-gamma photon coincidence events will be described in detail as follows.

An overall structure of an imaging system according to an embodiment of the present disclosure is shown in <FIG>. The imaging system includes two detector assemblies, a time coincidence module <NUM>, a computer platform <NUM>, a timing signaling line and an energy and location signaling line. The two detector assemblies are arranged in such a manner that detecting planes thereof are perpendicular to each other. Each detector assembly includes a detector <NUM> configured to detect a single-gamma photon event and measure time and a parallel-hole collimator <NUM> arranged in front of the detector <NUM> such that the single-gamma photon event generated during decay of a radionuclide in a subject <NUM> to be imaged and emitted only along a set direction (such as a direction perpendicular to the detecting plane of the detector <NUM>) is detected by the detector <NUM>. The subject <NUM> to be imaged may be an organism or a standardized imaging phantom of a nuclear medical imaging system. The timing signaling line connects the detector <NUM> and the time coincidence module <NUM>. The time coincidence module <NUM> is provided with a time window (which is adjustable according to the radionuclide and generally within hundreds of nanoseconds) and configured to determine, with the time window, whether the single-gamma photon events detected by the two detectors constitute a multiple-gamma photon coincidence event and input a corresponding determination result to the computer platform <NUM>. The energy and location signaling line connects the detector <NUM> and the computer platform <NUM>. The computer platform <NUM> is configured to calculate non-parallel projection lines where gamma photons are emitted so as to determine a location where the decay of the radionuclide takes place.

The parallel-hole collimator <NUM> used in this example includes a rectangular tungsten alloy plate where the tungsten alloy has a strong absorption to the gamma photon. Several parallel collimating holes are arranged at an equal interval on the rectangular plate such that gamma photons emitted only along the hole can pass through the collimator and be detected by the detector <NUM>. In this example, the collimator is of a thickness of <NUM>, each collimating hole is of a diameter of <NUM> and a wall thickness of <NUM>.

The detector <NUM> used in this example is a NaI(Tl) scintillator detector which uses a continuous NaI(Tl) crystal, is of a size of <NUM> (length)× <NUM> (width)× <NUM> (thickness), and is coupled to <NUM> photomultipliers (PMTs) at an end of the NaI(Tl) crystal opposite to the collimator for photoelectric signal conversion so as to achieve measurement of the position, energy and time information of the gamma photon in the crystal.

In addition to indium <NUM>, a radiopharmaceutical used in the imaging system according to the present disclosure may also be labeled with other radionuclides which are capable of generating at least two gamma photons in a cascade manner within a short time during each decay, including but not limited to sodium <NUM>, iodine <NUM>, thallium <NUM>, rubidium <NUM>, yttrium <NUM>, and the like.

In addition to the parallel-hole collimator as shown in <FIG>, the collimator used in the imaging system according to the present disclosure may also be a pinhole collimator (as shown in <FIG>), a convergent collimator or a divergent collimator and the like, all of which are conventional products. In embodiments of the present disclosure, the type and parameters of the collimator can be selected according to factors such as field of view (FOV), spatial resolution and detection efficiency of the imaging system to be achieved.

In addition to two detector assemblies used in the imaging system in this example, in other examples, the imaging system may include more than two detector assemblies, the more than two detector assemblies are arranged in such a manner that at least two detecting planes thereof are non-parallel one another, such as in circular, square or polygonal manner. The number and arrangement manners of the detector assemblies may be selected according to the detection efficiency of the imaging system to be achieved. The detection efficiency of the imaging system is higher with the number of probes increases.

A flow chart of an imaging method of the imaging system according to an embodiment of the present disclosure is shown in <FIG>. Referring to <FIG>, an implementation of the imaging method includes:.

It should be appreciated that, the number of the non-parallel projection lines may be at least <NUM> but not more than the number of the gamma photons cascade-emitted by the radionuclide in each decay, and each single-gamma photon event can determine a projection line where the decay of the radionuclide takes place.

With the imaging system according to embodiments of the present disclosure, the location where the decay of the radionuclide takes place can be determined via a direct calculation, thus, the image reconstruction algorithm is simplified and the SNR of the reconstructed image is improved. At the same time, there is no need to accumulate a large number of projection lines to reconstruct a spatial distribution of radionuclides, thereby reducing the total demand for gamma photon events, the intake amount of radionuclide by the patient, and the irradiation risk to the patient to a certain extent.

The imaging method according to embodiments of the present disclosure can be programmed (which can be realized by a programmer through conventional programming techniques) and input to the computer platform <NUM>. A desired effect can be achieved when the imaging method is executed in accordance with the steps.

In embodiments of the present disclosure, there is further provided a device, including:.

In embodiments of the present disclosure, there is further provided a non-transitory computer storage medium having stored therein one or more procedures that, when executed by a device, causes the device to perform imaging method mentioned above.

Furthermore, a method and system for batch production of multi-layer microfluidic chips, other configurations and functions of the non-transitory computer storage medium are known to those skilled in the art, and will not be elaborated herein.

Reference throughout this specification to "an embodiment," "some embodiments," "one embodiment", "another example," "an example," "a specific example," or "some examples," means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. Thus, the appearances of the phrases such as "in some embodiments," "in one embodiment", "in an embodiment", "in another example," "in an example," "in a specific example," or "in some examples," in various places throughout this specification are not necessarily referring to the same embodiment or example of the present disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

Claim 1:
An imaging system based on multiple-gamma photon coincidence events, comprising:
a plurality of detector assemblies each comprising:
a detector (<NUM>), configured to detect a single-gamma photon event and measure time; and
a collimator (<NUM>), arranged in front of the detector (<NUM>) such that the single-gamma photon event generated during decay of a radionuclide and emitted only along a set direction is detected by the detector (<NUM>);
a time coincidence module (<NUM>), provided with a time window;
a computer platform (<NUM>);
a timing signaling line, connecting the detector (<NUM>) and the time coincidence module (<NUM>); and
an energy and location signaling line, connecting the detector (<NUM>) and the computer platform (<NUM>),
wherein the time coincidence module (<NUM>) is configured to determine, with the time window, whether a plurality of single-gamma photon events detected by the detectors (<NUM>) constitute a multiple-gamma photon coincidence event and input a determination result to the computer platform (<NUM>),
wherein the computer platform (<NUM>) is configured to determine validity of the multiple-gamma photon coincidence event and determine a location where the decay of the radionuclide takes place according to non-parallel projection lines where gamma photons are emitted,
characterised in that the computer platform (<NUM>) is further configured to:
determine whether energies of the plurality of single-gamma photon events in the multiple-gamma photon coincidence event each are within a corresponding preset energy window, according to energy information of the plurality of single-gamma photon events, if no, discarding the multiple-gamma photon coincidence event, if yes, calculate a plurality of non-parallel projection lines where the decay of the radionuclide takes place according to position information of the plurality of single-gamma photon events;
determine via calculating a point to which the sum of individual distances from the plurality of non-parallel projection lines is minimum;
determine whether a distance from the point to each projection line is lower than or equal to a preset length threshold, if yes, record the point as the location where the decay of the radionuclide takes place, if no, discard the multiple-gamma photon coincidence event; and
obtain a distribution of the radionuclide according to the location where the decay of the radionuclide takes place.