CN106859685B - Image reconstruction method, device and equipment - Google Patents
Image reconstruction method, device and equipment Download PDFInfo
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- CN106859685B CN106859685B CN201710008446.2A CN201710008446A CN106859685B CN 106859685 B CN106859685 B CN 106859685B CN 201710008446 A CN201710008446 A CN 201710008446A CN 106859685 B CN106859685 B CN 106859685B
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/58—Testing, adjusting or calibrating apparatus or devices for radiation diagnosis
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/02—Devices for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
- A61B6/03—Computerised tomographs
Abstract
The application provides an image reconstruction method, an image reconstruction device and image reconstruction equipment, wherein the method comprises the following steps: determining a crystal efficiency factor and a geometric factor of a single crystal in a crystal pair, wherein the crystal pair is a crystal pair on a crystal ring in the PET equipment; determining the sensitivity of the crystal pair according to the crystal efficiency factor and the geometric factor of the single crystal in the crystal pair; acquiring data of a patient scanned by the crystal pair; correcting data by using the sensitivity of the crystal pair; and reconstructing an image according to the corrected data. According to the method and the device, the sensitivity of the crystal pair is determined according to the crystal efficiency factor and the geometric factor of a single crystal, the scanned data is effectively corrected by utilizing the sensitivity, and the accuracy of image reconstruction is improved. In addition, the background radiation of the crystal is corrected, a radioactive source does not need to be purchased, a radioactive source device does not need to be manufactured, the geometric factors of the crystal pair are simply and efficiently calculated, the cost is reduced, and the radiation danger of operators is avoided.
Description
Technical Field
The present application relates to the field of medical equipment technologies, and in particular, to an image reconstruction method, apparatus, and device.
Background
Positron Emission Tomography (PET) equipment is one of the most advanced large medical scientific research and clinical diagnosis equipment currently recognized, and has excellent performance in the aspect of diagnosing diseases such as tumors, cardiovascular diseases and the like. In the process of acquiring the patient data by the PET equipment, the sensitivity (efficiency) of the crystal pair is inconsistent due to the polygonal geometric structure of the PET equipment, so that the acquired data number is different from the data number actually sent out in the patient, and the reconstructed image can not correctly reflect the distribution condition of the activity of the radioactive elements in the patient.
To solve this problem, geometric correction of the data acquired by the PET device is proposed in the prior art. The method for ensuring the sensitivity consistency of the crystal specifically comprises the following steps: an external uniform radioactive source device is arranged at the center of a visual field of a PET device, photon pairs emitted by radioactive sources (such as a rotating rod source, a plane source, a ring source, a moving line source and the like) are collected, then a corresponding correction algorithm is designed by means of collected data, and a geometric correction factor of each pair of crystals is calculated.
In the prior art, although the accuracy of image reconstruction can be improved by correcting the geometric factors of the crystal pairs and ensuring the consistency of the sensitivity of the crystal pairs, in the existing mode, on one hand, a transmission source device needs to be placed, an external radioactive source device is complex in design, a radioactive source is not easy to store and shield, and the price is high; on the other hand, the calibration process requires the operator to handle the radiation source device, and the radiation emitted by the radiation source poses radiation risks to the operator's body.
Disclosure of Invention
In view of the above, the present application provides an image reconstruction method, apparatus and device, so as to improve the accuracy of image reconstruction by reducing the cost of geometric factor correction in the PET device and the radiation hazard caused by the geometric factor correction.
Specifically, the method is realized through the following technical scheme:
in a first aspect, an image reconstruction method is provided, the method including:
determining a crystal efficiency factor and a geometric factor of a single crystal in a crystal pair, wherein the crystal pair is a crystal pair on a crystal ring in a PET device;
determining the sensitivity of the crystal pair according to the crystal efficiency factor and the geometric factor of the single crystal in the crystal pair;
acquiring data of a patient scanned by the crystal pair;
correcting the data using the sensitivity of the crystal pair;
and reconstructing an image according to the corrected data.
A second aspect provides an image reconstruction apparatus, the apparatus comprising:
a first determining unit, which is used for determining the crystal efficiency factor and the geometric factor of a single crystal in a crystal pair, wherein the crystal pair is a crystal pair on a crystal ring in the PET equipment;
a second determination unit for determining the sensitivity of the crystal pair according to the crystal efficiency factor and the geometric factor of the single crystal in the crystal pair;
an acquisition unit for acquiring data of a patient scanned by the crystal pair;
a correction unit for correcting the data using the sensitivity of the crystal pair;
and the reconstruction unit is used for reconstructing an image according to the corrected data.
A third aspect provides a medical device comprising: a processor; and a memory for storing the processor-executable instructions; wherein the content of the first and second substances,
the processor is configured to:
determining a crystal efficiency factor and a geometric factor of a single crystal in a crystal pair, wherein the crystal pair is a crystal pair on a crystal ring in a PET device;
determining the sensitivity of the crystal pair according to the crystal efficiency factor and the geometric factor of the single crystal in the crystal pair;
acquiring data of a patient scanned by the crystal pair;
correcting the data using the sensitivity of the crystal pair;
and reconstructing an image according to the corrected data.
In the embodiment of the application, the crystal efficiency factor and the geometric factor of a single crystal in a crystal pair are determined firstly, the sensitivity of the crystal pair is determined according to the crystal efficiency factor and the geometric factor of the single crystal in the crystal pair, then, the data acquired by a patient are corrected by utilizing the sensitivity of the crystal pair, and image reconstruction is performed according to the corrected data. That is to say, in the embodiment of the present application, the sensitivity of the crystal pair is determined according to the crystal efficiency factor and the geometric factor of a single crystal, and the scanned data is effectively corrected by using the sensitivity, so that the accuracy of image reconstruction is improved. In addition, the background radiation of the crystal is corrected, a radioactive source does not need to be purchased, a radioactive source device does not need to be manufactured, the geometric factors of the crystal pair are simply and efficiently calculated, the cost is reduced, and the radiation danger of operators is avoided.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.
Drawings
Fig. 1 is a flowchart of an image reconstruction method provided in an embodiment of the present application;
FIG. 2 is a flow chart for determining the sensitivity of a crystal pair provided by an embodiment of the present application;
FIG. 3 is a schematic diagram of a crystal background coincidence event provided by an embodiment of the present application;
FIG. 4 is a schematic diagram of a calculation of a crystal efficiency factor provided by an embodiment of the present application;
fig. 5 is a hardware structure diagram of an image reconstruction device in which a crystal pair image reconstruction apparatus is provided in an embodiment of the present application;
fig. 6 is a schematic structural diagram of an image reconstruction apparatus provided in an embodiment of the present application;
fig. 7 is another schematic structural diagram of an image reconstruction apparatus according to an embodiment of the present application;
fig. 8 is another schematic structural diagram of an image reconstruction apparatus provided in an embodiment of the present application;
fig. 9 is another schematic structural diagram of an image reconstruction apparatus according to an embodiment of the present application;
fig. 10 is another schematic structural diagram of an image reconstruction apparatus according to an embodiment of the present application.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.
It is to be understood that although the terms first, second, third, etc. may be used herein to describe various information, such information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present application. The word "if" as used herein may be interpreted as "at … …" or "when … …" or "in response to a determination", depending on the context.
Please refer to fig. 1, which is a flowchart illustrating an image reconstruction method according to an embodiment of the present disclosure; the method comprises the following steps:
step 101: determining a crystal efficiency factor and a geometric factor of a single crystal in a crystal pair, wherein the crystal pair is a crystal pair on a crystal ring in a PET device;
in this step, one process for determining the crystal efficiency factor and the geometry factor of a single crystal in a crystal pair is:
collecting a plurality of background coincidence events on a crystal pair; dividing the plurality of background coincidence events into a first class of background coincidence events and a second class of background coincidence events; then, determining a first crystal efficiency factor for a first type of background coincidence event and a second crystal efficiency factor for a second type of background coincidence event; correcting the first type of background coincidence events by using the first crystal efficiency factor to obtain corrected first type of background coincidence events, and correcting the second type of background coincidence events by using the second crystal efficiency factor to obtain corrected second type of background coincidence events; and finally, determining a first geometric factor and a second geometric factor corresponding to a single crystal on each pair of crystals by using the sum of the corrected first type background coincidence event and the corrected second type background coincidence event on each pair of crystals.
The detailed process of determining the crystal efficiency factor and the geometric factor of a single crystal in the crystal pair is described in the following fig. 2 to 4, and is not described in detail here.
Step 102: determining the sensitivity of the crystal pair according to the crystal efficiency factor and the geometric factor of the single crystal in the crystal pair;
in this step, the first crystal efficiency factor, the second crystal efficiency factor, the first geometric factor, and the first geometric factor obtained in step 101 are multiplied respectively to obtain the sensitivity of the crystal pair. Which may also be referred to as a sensitivity model for the crystal pair.
That is, the sensitivity of the crystal to i-j can be modeled by equation (1):
ηij＝εiεjgigj(1)
wherein eta isijThe sensitivity of the crystal pair i-j is shown, i-j respectively shows the single crystal in the crystal pair, epsiloni(or εj) The crystal efficiency factor, g, of the individual crystals i (or j) showni(or g)j) Representing the geometrical factor of the single crystal i (or j), reflecting the effect of the tilt angle of the single crystal on its acceptance of a single photon.
Step 103: acquiring data of a patient scanned by the crystal pair;
in this step, while scanning a patient using a PET device, the PET device acquires data of the patient scanned by the crystal pair.
Step 104: correcting the data using the sensitivity of the crystal pair;
the process of correcting the data using the sensitivity of the crystal pair in this step is well known to those skilled in the art and will not be described in detail herein.
Step 105: and reconstructing an image according to the corrected data.
In this step, the image reconstruction process based on the corrected data is well known to those skilled in the art, and will not be described herein.
In the embodiment of the application, the crystal efficiency factor and the geometric factor of a single crystal in a crystal pair are determined firstly, the sensitivity of the crystal pair is determined according to the crystal efficiency factor and the geometric factor of the single crystal in the crystal pair, then, the data acquired by a patient are corrected by utilizing the sensitivity of the crystal pair, and image reconstruction is performed according to the corrected data. That is to say, in the embodiment of the present application, the sensitivity of the crystal pair is determined according to the crystal efficiency factor and the geometric factor of a single crystal, and the scanned data is effectively corrected by using the sensitivity, so that the accuracy of image reconstruction is improved. In addition, the background radiation of the crystal is corrected, a radioactive source does not need to be purchased, a radioactive source device does not need to be manufactured, the geometric factors of the crystal pair are simply and efficiently calculated, the cost is reduced, and the radiation danger of operators is avoided.
Please refer to fig. 2, which is a flowchart illustrating a method for correcting a crystal pair geometry factor according to an embodiment of the present application; the method comprises the following steps:
step 201: collecting a plurality of background coincidence events on the crystal pair;
in this step, the PET device collects a plurality of background coincidence events on the crystal pair, each background coincidence event comprising: a first type of background coincidence event and a second type of background coincidence event.
in this embodiment, a ring of crystals is included in the PET device, wherein each crystal on the ring of crystals may be a crystal with background radiation, such as a lutetium (Lu) -containing crystal (e.g., LYSO crystal, etc.), wherein the Lu element undergoes β -decay in a natural state accompanied by emission of γ photons of three different energy levels, 307KeV, 202KeV, 88KeV, respectively, and the β particles emitted by the decay undergo ionization in the crystal to release energy around 590KeV, which is detected by the crystal in which it is located, i.e., the β particles are "absorbed" by the crystal, and the emitted γ photons escape from the crystal, fly in the field for a period of time, and are detected by another crystal in a ring detector in the PET device, as shown in fig. 3, which is a schematic diagram of one of the crystal coincidence events provided in this embodiment of the present application, as shown in the figure 202, the β element is "absorbed" by the crystal i "and the γ photons are received by the crystal j, 201 is the opposite process of 202, and m, n represents two additional background crystals on the ring of crystals.
In order to simply and conveniently process the gamma photons with three different energy levels emitted by Lu element decay, the gamma photons with the energy of 202kev and 88kev are removed by setting an energy threshold, and only the gamma photon with the energy of 307kev is collected.
In this embodiment, an energy threshold Δ E is preset for the PET device, a coincidence time window Δ T, and events satisfying the following conditions are referred to as local radiation coincidence events.
Two particles are said to be a background coincidence event if the energy of the two particles as measured by the crystal pair satisfies the energy threshold Δ E and the time interval in which the two particles are detected by the crystal is within the coincidence event window Δ T. Whenever a background coincidence event occurs on a crystal pair i-j (where i and j respectively represent the individual crystals of the crystal pair), the count of the crystal pair i-j at a corresponding location in the circuit is incremented by 1, at which point the PET device collects and saves the background coincidence event.
Step 202: dividing the plurality of background coincidence events into a first class of background coincidence events and a second class of background coincidence events;
in this step, one of the dividing methods is: dividing the plurality of background coincidence events into a first type of background coincidence events and a second type of background coincidence events according to an energy threshold, wherein the energy threshold is preset, and dividing the background coincidence events according to the energy threshold is well known to those skilled in the art and will not be described herein.
Step 203: determining a first crystal efficiency factor for a first type of background coincidence event and a second crystal efficiency factor for a second type of background coincidence event;
in this step, since it is collected that one of the background coincidence events is a gamma particle and one is β particles, the beta particle is absorbed by the single crystal i (or j) with probability 1, as shown in fig. 2 in particular, and the gamma particle flies out of the single crystal i (or j) and hits the opposite single crystal j (or i) and is received by the single crystal j (or i), the background coincidence event reflects the efficiency of the single crystal j (or i) to receive the gamma particle (the beta particle has the effect of determining its corresponding gamma photon by means of it).
That is, the efficiency of any pair of crystal pairs at the time of receiving a coincidence event is affected by both the crystal intrinsic efficiency, which is removed prior to calculating the geometric correction factor for the crystal pair, and the annular geometry of the apparatus.
Therefore, one way to calculate the crystal efficiency factor (the first crystal efficiency factor is taken as an example in this embodiment) is:
as FIG. 3 illustrates the characteristics of the background coincidence events, the background coincidence events (i.e., data, i.e., data consisting of a plurality of background coincidence events) collected by the crystal pair i-j are of two types, 201 and 202, and 201 is referred to herein as a first type of background coincidence event and 202 is referred to herein as a second type of background coincidence event. Where 201 denotes a background coincidence event in which crystal i receives a gamma photon and 202 denotes a background coincidence event in which crystal j receives a gamma photon. Assuming that the total count of background coincidence events collected on a crystal pair i-j is n, n comprises a number 201 of background coincidence events and a number 202 of background coincidence events.
since the energy of the beta particles is different from that of the gamma particles, it can be determined whether the particles detected by the crystal i is β or gamma by the energy threshold of the particles detected by the crystal i, i.e. whether the background coincidence event is 201 or 202ijFor the counted 202 total number of background coincidence events, the 201 total number of background coincidence events is nij＝n-nji。
The intrinsic efficiency of crystal i is calculated, and for background coincidence events collected on crystal pair i-j, this embodiment exemplifies a background coincidence event of the type 201. According to the collected 201 background coincidence event nijThe fan beam algorithm is used to calculate the efficiency correction factor (i.e. the first crystal efficiency factor) of a single crystal i on the crystal pair, and the formula of the fan beam algorithm is as follows:
where N denotes the total number of crystals on the ring detector, jminDenotes the starting crystal number of the fan beam, jmaxEnd crystal number, n, representing fan beamijA first total count, ε, representing background coincidence events of a first typeiRepresenting a first crystal efficiency factor.
Similarly, a second total count n of second background coincidence events is countedjiAccording to said second count total njiThe fan beam algorithm is used to calculate the efficiency correction factor (i.e., the second crystal efficiency factor) for a single crystal j on the crystal pair, and the formula of the fan beam algorithm is:
where N denotes the total number of crystals on the ring detector, jminDenotes the starting crystal number of the fan beam, jmaxEnd crystal number, n, representing fan beamjiA second total count, ε, representing a second background coincidence eventjRepresenting a second crystal efficiency factor.
Wherein j isminAnd jmaxSpecifically, as shown in fig. 4, fig. 4 is a schematic diagram for calculating a crystal efficiency factor according to an embodiment of the present application.
In addition, the calculation of the efficiency factor of crystal j (i.e., the second crystal efficiency factor) needs to be based on the 202 type of background coincidence event on crystal pair i-j, and the data type for calculating other crystal efficiency factors is either the same as the type of background coincidence event adopted by crystal i or the same as that of crystal j, and the calculation process is similar and will not be described again.
Step 204: correcting the first type of background coincidence events by using the first crystal efficiency factor to obtain corrected first type of background coincidence events, and correcting the second type of background coincidence events by using the second crystal efficiency factor to obtain corrected second type of background coincidence events;
in the step, the corresponding background coincidence events are respectively corrected by utilizing the crystal efficiency factors,
since the efficiency correction factor epsilon of each crystal on the crystal ring is obtainedi(i is 1 to N), then the efficiency correction factor epsilon is also usediAnd (3) carrying out crystal efficiency correction on the background coincidence events on the crystal pairs i-j, wherein the correction aims to remove the influence caused by the inherent efficiency of the crystal, and then calculating a geometric correction factor.
Considering that the background coincidence event is only affected by one crystal, when crystal efficiency correction is carried out on the total count n of the background coincidence events collected on the crystal pairs i-j, the 201 and 202 events contained in the crystal pairs are required to be respectively corrected by epsiloniAnd εjCorrected individually, i.e. n'ji＝nji*εjOf which is n'jiDenotes 202 events, n 'after correction of crystal efficiency'ji＝nji*εj，n’ij＝nij*εiAt this point, the total number of coincidence events on crystal pair i-j is n ═ n'ij+n'ji。
Step 205: determining a first geometric factor and a second geometric factor corresponding to a single crystal on each pair of crystals by using the sum of the corrected first type background coincidence event and the corrected second type background coincidence event on each pair of crystals;
in this step, unlike the existing method of directly calculating the geometric factors of each pair of crystal pairs, the present embodiment proposes to separately calculate the geometric factors of each crystal in consideration of the characteristics of the background coincidence event, and then combine the geometric factors to obtain the geometric factors of the crystal pairs.
As can be seen in FIG. 3, assuming there are a total of M crystal pairs along the direction of crystal pair i-j (e.g., crystal pair M-n is a crystal pair having the same direction as crystal pair i-j), respectively: xtali1Xtalj1，Xtali2Xtalj2，…XtaliMXtaljMTotal count of background coincidence events corrected by crystal efficiency factor on each pair of crystals is n'1，n'2，…n'MThen a single crystal Xtalik(or Xtaljk) The geometric correction factor (k 1 to N) can be obtained by a normalization algorithm, wherein the formula of one normalization algorithm is:
wherein due to the crystal Xtaljk(or Xtalik) Geometric influence and Xtal on receiving dataik(or Xtaljk) Same, therefore, gjkThe geometric correction factor (c) can also be obtained by a normalization algorithm, wherein a calculation formula of the normalization algorithm is shown in formula (4), and the calculation process is combined with gikThe calculation process of the geometric correction factor is similar, and is described in detail above, and is not described herein again.
Further, on the basis of the above embodiment, it is also possible to: the first geometric factor and the second geometric factor are combined to obtain a geometric factor of the crystal pair, and the first crystal efficiency factor and the second crystal efficiency factor can also be combined to obtain a crystal efficiency factor of the crystal pair.
In this step, one combination is to multiply the first geometric factor by the second geometric factor to obtain the geometric factor of the crystal pair.
I.e. the crystal pair XtalikXtaljkThe geometric correction factors (k 1 to N) are:
gikjk＝gik*gjk(5)
thus, according to equations (2A), (2B) and (5), the sensitivity of the crystal to i-j can be obtained by means of equation (1) of the above-established model.
In the embodiment of the application, a plurality of collected background coincidence events are divided into different types of background coincidence events, corresponding crystal efficiency factors are respectively calculated according to the corresponding background coincidence events, then the corresponding background coincidence events before correction are corrected by the calculated crystal efficiency factors, the geometric factors of a single crystal are calculated by the background coincidence events corrected on each pair of crystals, then the sensitivity of the crystal pair is determined according to the crystal efficiency factors and the geometric factors of the single crystal in the crystal pair, the acquired data of a patient are corrected by the sensitivity of the crystal pair, and image reconstruction is performed according to the corrected data. That is to say, in the embodiment of the present application, the sensitivity of the crystal pair is determined according to the crystal efficiency factor and the geometric factor of a single crystal, and the scanned data is effectively corrected by using the sensitivity, so that the accuracy of image reconstruction is improved. In addition, the background radiation of the crystal is corrected, a radioactive source does not need to be purchased, a radioactive source device does not need to be manufactured, the geometric factors of the crystal pair are simply and efficiently calculated, the cost is reduced, and the radiation danger of operators is avoided.
Corresponding to the embodiment of the image reconstruction method, the application also provides an embodiment of an image reconstruction device.
The embodiment of the image reconstruction device provided by the application can be applied to image reconstruction equipment, and the image reconstruction equipment can be an upper computer. As shown in fig. 5, a hardware structure of an image reconstruction apparatus in which the image reconstruction device provided in the embodiment of the present application is located may include a processor 501 and a machine-readable storage medium 502, where the processor 501 and the machine-readable storage medium 502 are generally connected with each other by an internal bus 503. In other possible implementations, the device may also include an external interface 504 to enable communication with other devices or components. Further, the machine-readable storage medium 502 has stored thereon a control logic 505 for image reconstruction, and the control logic 505 is functionally divided into logic modules, which may be the structure of the image reconstruction apparatus shown in fig. 6.
Referring to fig. 6, a schematic structural diagram of an image reconstruction apparatus according to an embodiment of the present application is shown, where the apparatus includes: a first determining unit 61, a second determining unit 62, an obtaining unit 63, a correcting unit 64 and a reconstructing unit 65, wherein,
a first determining unit 61, configured to determine a crystal efficiency factor and a geometry factor of a single crystal in a crystal pair, wherein the crystal pair is a crystal pair on a crystal ring in a PET apparatus;
a second determination unit 62 for determining the sensitivity of the crystal pair according to the crystal efficiency factor and the geometric factor of the single crystal in the crystal pair;
an acquisition unit 63 for acquiring data of a patient scanned by the crystal pair;
a correction unit 64 for correcting the data using the sensitivity of the crystal pair;
and a reconstruction unit 65 for performing image reconstruction according to the data corrected by the correction unit.
Optionally, in another embodiment, on the basis of the above embodiment, the first determining unit 61 includes: the acquisition unit 71, the dividing unit 72, the efficiency factor determining unit 73, the event correcting unit 74 and the geometric factor determining unit 75 are schematically shown in fig. 7, wherein,
an acquisition unit 71 for acquiring a plurality of background coincidence events on the crystal pair;
a dividing unit 72, configured to divide the plurality of background coincidence events into a first type of background coincidence event and a second type of background coincidence event;
an efficiency factor determination unit 73 for determining a first crystal efficiency factor for a first type of background coincidence event and a second crystal efficiency factor for a second type of background coincidence event;
an event correcting unit 74, configured to correct the first type of background coincidence event by using the first crystal efficiency factor to obtain a corrected first type of background coincidence event, and correct the second type of background coincidence event by using the second crystal efficiency factor to obtain a corrected second type of background coincidence event;
a geometry factor determining unit 75 for determining a first geometry factor and a second geometry factor corresponding to a single crystal on each pair of crystals by using the sum of the corrected first type background coincidence event and the corrected second type background coincidence event on the pair of crystals.
Optionally, in another embodiment, on the basis of the foregoing embodiment, the dividing unit 72 is specifically configured to divide the plurality of background coincidence events into a first type of background coincidence events and a second type of background coincidence events according to an energy threshold.
Optionally, in another embodiment, on the basis of the above embodiment, the efficiency factor determining unit 73 includes: a statistical unit 731 and a calculation unit 732, which are schematically shown in fig. 8, wherein,
a counting unit 731, configured to count a first count total of the first type of background coincidence events and a second count total of the second type of background coincidence events;
a calculating unit 732 for calculating a first crystal efficiency factor and a second crystal efficiency factor by using a fan beam algorithm according to the first count total and the second count total.
Wherein a formula can be utilized based on the first count total
Calculating a first crystal efficiency factor; and utilizing a formula according to the second count total
Calculating a second crystal efficiency factor;
where N denotes the total number of crystals on the ring detector, jminDenotes the starting crystal number of the fan beam, jmaxEnd crystal number, n, representing fan beamijA first total count, n, representing background coincidence events of a first typejiIndicating a second background matchSecond total count n of piecesji，εiDenotes the first crystal efficiency factor, εjRepresenting a second crystal efficiency factor.
Alternatively, in another embodiment, on the basis of the above embodiment, the event correction unit 74 includes: a schematic diagram of the first syndrome unit 741 and the second syndrome unit 742 is shown in fig. 9, wherein,
a first syndrome unit 741, configured to multiply the first crystal efficiency factor by the first type background coincidence event, so as to obtain a corrected first type background coincidence event;
a second correcting subunit 742, configured to multiply the second crystal efficiency factor by the second type of background coincidence event to obtain a corrected second type of background coincidence event.
Optionally, in another embodiment, on the basis of the above embodiment, the geometry factor determining unit 75 includes: a first determination subunit 751 and a second determination subunit 752, whose structural schematic is shown in fig. 10, wherein,
a first determining subunit 751 for calculating a first geometric factor of a last crystal of each pair of crystals by using a normalization algorithm according to the sum of the first type of background coincidence event and the second type of background coincidence event on each pair of crystals after correction;
a second determining subunit 752, configured to calculate a second geometric factor of another crystal on each pair of crystals by using a normalization algorithm according to a sum of the first type background coincidence event and the second type background coincidence event on each pair of crystals after correction.
Optionally, in another embodiment, on the basis of the above embodiment, the efficiency factor determining unit 76 may further include: a first combination unit and/or a second combination unit (not shown), wherein,
the first combination unit is used for combining the first geometric factor and the second geometric factor to obtain a geometric factor of the crystal pair;
and the second combination unit is used for combining the first crystal efficiency factor and the second crystal efficiency factor to obtain the crystal efficiency factor of the crystal pair.
The implementation process of the functions and actions of each unit in the above device is specifically described in the implementation process of the corresponding step in the above method, and is not described herein again.
In different examples, the machine-readable storage medium 502 may be: a RAM (random Access Memory), a volatile Memory, a non-volatile Memory, a flash Memory, a storage drive (e.g., a hard drive), a solid state drive, any type of storage disk (e.g., an optical disk, a dvd, etc.), or similar storage medium, or a combination thereof.
In the embodiment of the application, the crystal efficiency factor and the geometric factor of a single crystal in the crystal pair are determined firstly, then the sensitivity of the crystal pair is determined according to the crystal efficiency factor and the geometric factor of the single crystal in the crystal pair, the data obtained by a patient are corrected by using the sensitivity of the crystal pair, and finally the corrected data are used for image reconstruction, so that the accuracy of image reconstruction is improved. That is to say, in the embodiment of the present application, the sensitivity of the crystal pair is determined according to the crystal efficiency factor and the geometric factor of a single crystal, and the scanned data is effectively corrected by using the sensitivity, so that the accuracy of image reconstruction is improved. In addition, the background radiation of the crystal is corrected, a radioactive source does not need to be purchased, a radioactive source device does not need to be manufactured, the geometric factors of the crystal pair are simply and efficiently calculated, the cost is reduced, and the radiation danger of operators is avoided.
In addition, this application embodiment still provides a medical equipment, includes: a processor; and a memory for storing the processor-executable instructions; the memory may be a machine-readable storage medium in which,
the processor is configured to:
determining a crystal efficiency factor and a geometric factor of a single crystal in a crystal pair, wherein the crystal pair is a crystal pair on a crystal ring in a PET device;
determining the sensitivity of the crystal pair according to the crystal efficiency factor and the geometric factor of the single crystal in the crystal pair;
acquiring data of a patient scanned by the crystal pair;
correcting the data using the sensitivity of the crystal pair;
and reconstructing an image according to the corrected data.
Wherein determining the crystal efficiency factor and the geometry factor for a single crystal in the crystal pair comprises:
collecting a plurality of background coincidence events on the crystal pair;
dividing the plurality of background coincidence events into a first class of background coincidence events and a second class of background coincidence events;
determining a first crystal efficiency factor for a first type of background coincidence event and a second crystal efficiency factor for a second type of background coincidence event;
correcting the first type of background coincidence events by using the first crystal efficiency factor to obtain corrected first type of background coincidence events, and correcting the second type of background coincidence events by using the second crystal efficiency factor to obtain corrected second type of background coincidence events;
and determining a first geometric factor and a second geometric factor corresponding to each crystal on each crystal pair by using the sum of the corrected first type background coincidence event and the corrected second type background coincidence event on each crystal pair.
In the embodiment of the application, a plurality of collected background coincidence events are divided into different types of background coincidence events, corresponding crystal efficiency factors are respectively calculated according to the corresponding background coincidence events, then the corresponding background coincidence events before are corrected by using the calculated crystal efficiency factors, finally, the geometric factors of single crystals are calculated by using the corrected background coincidence events on each pair of crystal pairs, and then the geometric factors of the single crystals are combined to obtain the aggregation factors of the crystal pairs. That is to say, in the embodiment of the present application, according to the characteristics of the device crystal, a corresponding crystal pair sensitivity model is established, a radioactive source does not need to be purchased, a radioactive source device is not needed to be manufactured, the geometric factors of the crystal pair are simply and efficiently calculated, the cost is reduced, and the radiation risk of the operating personnel is avoided.
For the device embodiments, since they substantially correspond to the method embodiments, reference may be made to the partial description of the method embodiments for relevant points. The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the scheme of the application. One of ordinary skill in the art can understand and implement it without inventive effort.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the scope of protection of the present application.
Claims (15)
1. An image reconstruction method, comprising:
determining a crystal efficiency factor and a geometric factor of a single crystal in a crystal pair, wherein the crystal pair is a crystal pair on a crystal ring in a PET device;
determining the sensitivity of the crystal pair according to the crystal efficiency factor and the geometric factor of the single crystal in the crystal pair;
acquiring data of a patient scanned by the crystal pair;
correcting the data using the sensitivity of the crystal pair;
and reconstructing an image according to the corrected data.
2. The method of claim 1, wherein determining the crystal efficiency factor and the geometry factor for an individual crystal in the pair of crystals comprises:
collecting a plurality of background coincidence events on the crystal pair;
dividing the plurality of background coincidence events into a first class of background coincidence events and a second class of background coincidence events;
determining a first crystal efficiency factor for a first type of background coincidence event and a second crystal efficiency factor for a second type of background coincidence event;
correcting the first type of background coincidence events by using the first crystal efficiency factor to obtain corrected first type of background coincidence events, and correcting the second type of background coincidence events by using the second crystal efficiency factor to obtain corrected second type of background coincidence events;
and determining a first geometric factor and a second geometric factor corresponding to a single crystal on each pair of crystals by using the sum of the corrected first type background coincidence event and the corrected second type background coincidence event on each pair of crystals.
3. The method of claim 2, wherein dividing the plurality of background coincidence events into a first class of background coincidence events and a second class of background coincidence events comprises:
the plurality of background coincidence events is divided into a first class of background coincidence events and a second class of background coincidence events according to an energy threshold.
4. The method of claim 2, wherein determining a first crystal efficiency factor for a first type of background coincidence event and a second crystal efficiency factor for a second type of background coincidence event comprises:
counting a first count total number of the first type of background coincidence events and a second count total number of the second type of background coincidence events;
and respectively calculating a first crystal efficiency factor and a second crystal efficiency factor by using a fan-beam algorithm according to the first total count and the second total count.
5. The method of claim 2, wherein correcting the first type of background coincidence events using the first crystal efficiency factor to obtain corrected first type of background coincidence events, and correcting the second type of background coincidence events using the second crystal efficiency factor to obtain corrected second type of background coincidence events comprises:
multiplying the first crystal efficiency factor by the first class of background coincidence events to obtain corrected first class of background coincidence events, and multiplying the second crystal efficiency factor by the second class of background coincidence events to obtain corrected second class of background coincidence events.
6. The method of claim 2, wherein calculating the first geometry factor and the second geometry factor using the sum of the corrected first type background coincidence event and the second type background coincidence event on each pair of crystals, respectively, comprises:
calculating a first geometric factor of a crystal on each pair of crystals by utilizing a normalization algorithm according to the sum of the first type background coincidence event and the second type background coincidence event on each pair of crystals after correction; and
and calculating a second geometric factor of the other crystal on each pair of crystals by utilizing a normalization algorithm according to the sum of the first type background coincidence event and the second type background coincidence event on each pair of crystals after correction.
7. The method of any one of claims 2 to 6, wherein determining the sensitivity of the crystal pair from the crystal efficiency factor and the geometry factor of the single crystal comprises:
and multiplying the first crystal efficiency factor, the second crystal efficiency factor, the first geometric factor and the first geometric factor respectively to obtain the sensitivity of the crystal pair.
8. An image reconstruction apparatus, comprising:
a first determining unit, which is used for determining the crystal efficiency factor and the geometric factor of a single crystal in a crystal pair, wherein the crystal pair is a crystal pair on a crystal ring in the PET equipment;
a second determination unit for determining the sensitivity of the crystal pair according to the crystal efficiency factor and the geometric factor of the single crystal in the crystal pair;
an acquisition unit for acquiring data of a patient scanned by the crystal pair;
a correction unit for correcting the data using the sensitivity of the crystal pair;
and the reconstruction unit is used for reconstructing an image according to the data corrected by the correction unit.
9. The apparatus according to claim 8, wherein the first determining unit comprises:
a collection unit for collecting a plurality of background coincidence events on the crystal pair;
a dividing unit, configured to divide the plurality of background coincidence events into a first type of background coincidence event and a second type of background coincidence event;
an efficiency factor determination unit for determining a first crystal efficiency factor for a first type of background coincidence event and a second crystal efficiency factor for a second type of background coincidence event;
the event correction unit is used for correcting the first type of background coincidence events by using the first crystal efficiency factor to obtain corrected first type of background coincidence events, and correcting the second type of background coincidence events by using the second crystal efficiency factor to obtain corrected second type of background coincidence events;
and the geometric factor determining unit is used for determining a first geometric factor and a second geometric factor corresponding to a single crystal on each pair of crystals by utilizing the sum of the corrected first type background coincidence event and the corrected second type background coincidence event on each pair of crystals.
10. The apparatus of claim 9,
the dividing unit is specifically configured to divide the plurality of background coincidence events into a first type of background coincidence event and a second type of background coincidence event according to an energy threshold.
11. The apparatus of claim 9, wherein the efficiency factor determination unit comprises:
the counting unit is used for counting the first counting total number of the first background coincidence events and the second counting total number of the second background coincidence events;
and the calculating unit is used for calculating a first crystal efficiency factor and a second crystal efficiency factor respectively by utilizing a fan-beam algorithm according to the first counting total number and the second counting total number.
12. The apparatus of claim 9, wherein the event correction unit comprises:
the first corrector subunit is used for multiplying the first crystal efficiency factor by the first type of background coincidence event to obtain a corrected first type of background coincidence event;
and the second correcting subunit is used for multiplying the second crystal efficiency factor by the second type background coincidence event to obtain a corrected second type background coincidence event.
13. The apparatus of claim 9, wherein the geometry factor determining unit comprises:
the first determining subunit is used for calculating a first geometric factor of a last crystal of each crystal pair by utilizing a normalization algorithm according to the sum of the first type of background coincidence event and the second type of background coincidence event on each corrected crystal pair;
and the second determining subunit is used for calculating a second geometric factor of another crystal on each crystal pair by utilizing a normalization algorithm according to the sum of the first type of background coincidence event and the second type of background coincidence event on each corrected crystal pair.
14. The apparatus according to any of the claims 9 to 13, wherein the second determination unit is specifically configured to multiply the first crystal efficiency factor, the second crystal efficiency factor, the first geometry factor and the first geometry factor, respectively, to obtain the sensitivity of the crystal pair.
15. A medical device, comprising: a processor; and a memory for storing the processor-executable instructions; wherein the content of the first and second substances,
the processor is configured to:
determining a crystal efficiency factor and a geometric factor of a single crystal in a crystal pair, wherein the crystal pair is a crystal pair on a crystal ring in a PET device;
determining the sensitivity of the crystal pair according to the crystal efficiency factor and the geometric factor of the single crystal in the crystal pair;
acquiring data of a patient scanned by the crystal pair;
correcting the data using the sensitivity of the crystal pair;
and reconstructing an image according to the corrected data.
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| CN107392876B (en) * | 2017-08-02 | 2020-10-02 | 上海联影医疗科技有限公司 | Method and device for acquiring normalized correction factor and medical imaging method |
| CN108186043B (en) * | 2018-02-09 | 2021-03-30 | 东软医疗系统股份有限公司 | Method and device for correcting sensitivity of PET equipment |
| CN108932740B (en) * | 2018-05-21 | 2022-06-07 | 湖北锐世数字医学影像科技有限公司 | Normalized correction factor acquisition method and medical imaging method |
| CN110301927B (en) * | 2019-07-04 | 2023-05-30 | 沈阳智核医疗科技有限公司 | Method, apparatus, storage medium and medical device for determining inherent efficiency of crystal |
| CN110301926B (en) * | 2019-07-04 | 2023-05-30 | 沈阳智核医疗科技有限公司 | Method, apparatus, storage medium and medical device for determining inherent efficiency of crystal |
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