CN111551981B - PET system sensitivity measuring device, method, computer device and storage medium - Google Patents
PET system sensitivity measuring device, method, computer device and storage medium Download PDFInfo
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Abstract
The present application relates to a PET system sensitivity measuring apparatus, method, computer device and storage medium as described above, the method comprises the steps of driving a detection assembly to reciprocate in the whole axial visual field of the PET system along a straight line parallel to the Z axis of the PET system by the movement device through the detection assembly consisting of a line source and a metal sleeve, simultaneously acquiring PET data by a PET acquisition device, the acquisition duration is determined according to the line source length, the AFOV length of the PET system and the movement speed of the detection assembly, the sensitivity of the PET system is determined according to the acquisition duration and the acquired PET data, the sensitivity of the PET system is detected in a more flexible and higher-universality mode, the line source and the metal sleeve matched with the axial visual field length of the PET system are avoided being used, the sensitivity measurement efficiency is improved, and the cost of the line source matched with the axial visual field length of the PET system is reduced.
Description
Technical Field
The application relates to the technical field of medical treatment, in particular to a PET system sensitivity measuring device, a PET system sensitivity measuring method, computer equipment and a storage medium.
Background
An important performance index in Positron Emission Computed Tomography (PET) technology is the sensitivity of a PET system, which represents the detection capability of the system on a radioactive source with unit intensity, and the higher the sensitivity is, the stronger the detection capability of the system on the radioactive source is. The high-sensitivity PET system can effectively reduce the injection dose of a patient on the premise of obtaining a high-quality reconstructed image.
However, because the axial visual field lengths of the PET systems are different, different sensitivity test models need to be customized according to the axial visual field in the related art, the cost is high, and a universal PET system sensitivity detection method applicable to various types of PET systems does not exist.
Aiming at the problems of high cost and poor universality of sensitivity detection customization of a PET system in the related art, no effective solution is provided at present.
Disclosure of Invention
In view of the above, it is necessary to provide a PET system sensitivity measuring apparatus, a method, a computer device and a storage medium for solving the above technical problems.
According to one aspect of the invention, the device is characterized by comprising a detection assembly, a moving device and a PET acquisition device, wherein the detection assembly comprises a line source and a metal sleeve, the metal sleeve is sleeved outside the line source, the detection assembly is placed on the moving device, the detection assembly is driven by the moving device to linearly move parallel to the Z axis of the PET system, the PET acquisition device acquires PET data while the detection assembly linearly moves, and the sensitivity of the PET system is determined according to the length of the line source, the axial visual field length of the PET system, the moving speed of the detection assembly and the acquired PET data.
In one embodiment, the moving device comprises an extension plate and a scanning bed of the PET system, the extension plate is connected with the scanning bed, the detection assembly is placed on the extension plate, and the scanning bed drives the detection assembly to perform linear motion parallel to the Z axis of the PET system through the extension plate.
In one embodiment, the length of the metal sleeve is greater than the length of the line source.
In one embodiment, the detection assembly is driven by the movement device to perform uniform linear motion parallel to the Z axis of the PET system.
In one embodiment, the detection assembly moves at a constant speed along an axial central field of view axis of the PET system or along a straight line which is offset from the axial central field of view axis by a preset distance and parallel to a Z-axis of the PET system.
According to another aspect of the present invention, there is also provided a PET system sensitivity measuring method applied to the PET system sensitivity measuring apparatus, the method including:
acquiring the acquisition starting moment when the line source reaches a slice i, acquiring the acquisition duration according to the length of the line source and the movement speed of the detection assembly, and acquiring the counting rate within the acquisition duration;
carrying out decay correction on the counting rate of the slice i according to the acquisition starting time and the acquisition duration, and summing the count rates after the decay correction of each slice in the axial view of the PET system to obtain a count rate without decay effect in the axial view AFOV;
determining the sensitivity of the PET system according to the total thickness of the metal sleeve, the non-decay effect counting rate corresponding to the total thickness and the line source activity of the line source.
In one embodiment, after determining the sensitivity of the PET system, the method comprises:
and acquiring the ratio of the count rate after the decay correction of the slice i to the count rate without the decay effect in the axial field of view, and determining the sensitivity of the slice i according to the ratio and the sensitivity of the PET system.
In one embodiment, the determining the sensitivity of the PET system according to the total thickness of the metal sleeve, the non-decay effect count rate corresponding to the total thickness, and the line source activity of the line source comprises:
changing the total thickness of the metal sleeve by increasing or decreasing the number of the metal sleeves;
recording the total thickness and the decay-free effect count rate corresponding to the total thickness;
determining the count rate without decay effect when the total thickness is zero according to the total thickness and the count rate without decay effect;
and determining the sensitivity of the PET system according to the non-decay effect counting rate when the total thickness is zero and the line source activity.
According to another aspect of the present invention, there is also provided a computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the following steps when executing the computer program:
acquiring the acquisition starting moment when a line source reaches a slice i, acquiring the acquisition duration according to the length of the line source and the movement speed of a detection assembly, and acquiring the counting rate of the line source in the acquisition duration, wherein the detection assembly comprises the line source and a metal sleeve;
carrying out decay correction on the counting rate of the slice i according to the acquisition starting time and the acquisition duration, and summing the count rates after the decay correction of each slice in the axial view of the PET system to obtain the count rate without decay effect in the axial view AFOV;
determining the sensitivity of the PET system according to the total thickness of the metal sleeve, the non-decay effect counting rate corresponding to the total thickness and the line source activity of the line source.
In one embodiment, the processor, when executing the computer program, performs the steps of: and acquiring the ratio of the count rate after the decay correction of the slice i to the count rate without the decay effect in the axial field of view, and determining the sensitivity of the slice i according to the ratio and the sensitivity of the PET system.
In one embodiment, the processor, when executing the computer program, performs the steps of: changing the total thickness of the metal sleeve by increasing or decreasing the number of the metal sleeve;
recording the total thickness and the decay-free effect count rate corresponding to the total thickness;
determining a count rate without decay effect when the total thickness is zero according to the total thickness and the count rate without decay effect;
and determining the sensitivity of the PET system according to the non-decay effect counting rate when the total thickness is zero and the line source activity.
According to another aspect of the present invention, there is also provided a computer readable storage medium having stored thereon a computer program which, when executed by a processor, performs the steps of:
acquiring the acquisition starting moment when a line source reaches a slice i, acquiring the acquisition duration according to the length of the line source and the movement speed of a detection assembly, and acquiring the counting rate of the line source in the acquisition duration, wherein the detection assembly comprises the line source and a metal sleeve;
carrying out decay correction on the counting rate of the slice i according to the acquisition starting time and the acquisition duration, and summing the count rates after the decay correction of each slice in the axial view of the PET system to obtain a count rate without decay effect in the axial view AFOV;
determining the sensitivity of the PET system according to the total thickness of the metal sleeve, the non-decay effect counting rate corresponding to the total thickness and the line source activity of the line source.
The computer program when executed by a processor implementing the steps of:
and acquiring the ratio of the count rate after the decay correction of the slice i to the count rate without the decay effect in the axial field of view, and determining the sensitivity of the slice i according to the ratio and the sensitivity of the PET system.
The computer program when executed by a processor implementing the steps of:
changing the total thickness of the metal sleeve by increasing or decreasing the number of the metal sleeves;
recording the total thickness and the decay-effect-free count rate corresponding to the total thickness;
determining the count rate without decay effect when the total thickness is zero according to the total thickness and the count rate without decay effect;
and determining the sensitivity of the PET system according to the non-decay effect counting rate when the total thickness is zero and the line source activity.
The device comprises a detection assembly consisting of a line source and a metal sleeve, wherein the detection assembly is driven by a movement device to reciprocate in the whole axial visual field of the PET system along a straight line parallel to the Z axis of the PET system, PET data are collected by a PET collection device, the collection duration is determined according to the length of the line source, the AFOV length of the PET system and the movement speed of the detection assembly, and then the sensitivity of the PET system is determined according to the collection duration and the collected PET data.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:
FIG. 1 is a diagram of an application scenario of a sensitivity measuring device of a PET system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a PET system sensitivity measurement apparatus in accordance with one embodiment of the invention;
FIG. 3 is a schematic diagram of a sensitivity measuring device of a PET system according to another embodiment of the invention;
FIG. 4 is a schematic view of a detection assembly moving at a constant velocity in accordance with one embodiment of the present invention;
FIG. 5 is a first flowchart of a method for measuring sensitivity of a PET system according to an embodiment of the invention;
FIG. 6 is a schematic view of a line source passing through slice i in accordance with one embodiment of the present invention;
FIG. 7 is a flow chart of a second method for slice sensitivity measurement in a PET system according to an embodiment of the invention;
FIG. 8 is a schematic diagram of a PET system sensitivity measuring computer device in accordance with one embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments provided in the present application without any inventive step are within the scope of protection of the present application.
It is obvious that the drawings in the following description are only examples or embodiments of the present application, and that it is also possible for a person skilled in the art to apply the present application to other similar contexts on the basis of these drawings without inventive effort. Moreover, it should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another.
Reference in the specification to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the specification. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is to be expressly and implicitly understood by one of ordinary skill in the art that the embodiments described herein may be combined with other embodiments without conflict.
Unless defined otherwise, technical or scientific terms referred to herein shall have the ordinary meaning as understood by those of ordinary skill in the art to which this application belongs. Reference to "a," "an," "the," and similar words throughout this application are not to be construed as limiting in number, and may refer to the singular or the plural. The present application is directed to the use of the terms "including," "comprising," "having," and any variations thereof, which are intended to cover non-exclusive inclusions; for example, a process, method, system, article, or apparatus that comprises a list of steps or modules (elements) is not limited to the listed steps or elements, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus. Reference to "connected," "coupled," and the like in this application is not intended to be limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The term "plurality" as referred to herein means two or more. "and/or" describes an association relationship of associated objects, meaning that three relationships may exist, for example, "A and/or B" may mean: a exists alone, A and B exist simultaneously, and B exists alone. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. Reference herein to the terms "first," "second," "third," and the like, are merely to distinguish similar objects and do not denote a particular ordering for the objects.
Fig. 1 is a view of an application scenario of a PET system sensitivity measuring device according to an embodiment of the present invention, and as shown in fig. 1, the PET system sensitivity measuring device and method provided in the present application can be applied to the application environment shown in fig. 1. Wherein, the axial field-of-view (AFOV) length of the PET system 100 may range from 0.75 m to 2 m, and may even exceed 2 m, for example, the axial length of the whole body scan PET with an ultra-long axial view is close to 2 m, wherein, AFOV means the maximum length along the Z-axis of the PET system 100, which can effectively detect the coincidence event. The acquisition device 108 may include one or more detector modules. The detector module may comprise one or more detector tiles. In some embodiments, the detector blocks may be mounted to an inner wall of a support assembly of the PET system 100 in a number of rings. Alternatively, the collection device 108 may have a second transverse diameter, or referred to as the transverse diameter of the collection device, and a second axial length, or referred to as the axial length of the collection device. The axial length of the acquisition device 108 may be the length of the acquisition device in the Z-axis direction. The transverse diameter of the acquisition device 108 may be defined as the diameter of the detection ring in a transverse plane perpendicular to the Z-axis direction. In some embodiments, the axial length of the detector assembly is related to the axial field of view AFOV of the PET system 100. As used herein, axial field of view AFOV can refer to the direction along the Z-axis of the acquisition device that is effective to detect the maximum length of a coincidence event. The greater the axial length of the acquisition device 108, the greater the AFOV of the PET system 100. For example, the axial length of the acquisition device 108 may be greater than 0.75 meters, or greater than 1 meter, or greater than 1.5 meters, or greater than 2 meters. Accordingly, the axial length of the axial field of view AFOV may be greater than 0.75 meters, or greater than 1 meter, or greater than 1.5 meters, or greater than 2 meters. Multiple organs of the subject (e.g., head, heart, lung, liver, stomach, pancreas, bladder, knee, etc.) may be scanned in a single scan. As another example, the axial length of the acquisition device 108 may range from 0.75 meters to 1.25 meters, such that the area between the head and the thigh of an object under examination, such as an adult patient, may be scanned in a single scan, or a full body scan of an object under examination having a smaller size, such as a child, may be performed in a single scan. The transverse diameter of the acquisition device 108 may be related to the Field of view (FOV) of the PET system 100. The PET system 100 may include a plurality of acquisition devices 108, the plurality of acquisition devices 108 being arranged in an approximately cylindrical configuration, generally speaking, the greater the number of acquisition devices 108 included in the PET detector assembly, the more radiation that can be received by the PET detector assembly, and the greater the sensitivity of the PET imaging system.
Sensitivity refers to the count rate of coincidence events acquired by the PET acquisition device 108 for a given radiation source intensity by the PET system. Because positron annihilation emitted by the radiation source generates a pair of gamma rays, the acquisition device 108 acquires information such as energy, position, time information and the like of the gamma rays for image reconstruction. Therefore, a large amount of material enclosure is required outside the radiation source to ensure the annihilation process. However, the material surrounding the radiation source also attenuates the gamma rays produced by annihilation, thus making it difficult to measure without decay effects during detection. In order to obtain measured data without decay effects, it is necessary to deduce the sensitivity of the PET system without absorber from the count rate of the standard line source when setting absorbers of different thicknesses, by surrounding the standard line source with controllably measurable absorbers. In order to measure the sensitivity of the PET system, according to the NEMA2012 standard, a line source corresponding to the axial visual field length of the PET system needs to be poured, sleeves with the same length are sequentially added and subtracted, data acquisition is respectively carried out at the center and the eccentric position, and then the sensitivity index of the system is obtained through calculation. For most PET systems with a short axial field of view, the above method can be used to measure the sensitivity of the system over its entire axial field of view. Whereas PET is scanned for the whole body with an ultra-long axial field of view. If the 70cm line source in the NEMA2012 standard is still used, the sensitivity of the system in a partial axial view can only be measured, and if the sensitivity of the system in the whole axial view needs to be measured, the line source and the sleeve with the length exceeding 2 meters are needed, and the processing, the storage, the transportation, the perfusion, the placement, the operation and the like of the line source are very inconvenient.
In accordance with an aspect of the present invention, fig. 2 is a schematic diagram of a PET system sensitivity measuring apparatus according to an embodiment of the present invention, and as shown in fig. 2, a PET system sensitivity measuring apparatus is provided, which is applied to the application scenario of fig. 1 as an example, the PET system sensitivity detecting apparatus includes a detecting assembly 102, a moving apparatus 106, and a PET acquiring apparatus 108. The detecting assembly 102 comprises a line source 103 and a metal sleeve 104, wherein the metal sleeve 104 is the absorber and is sleeved outside the line source 103, and the thickness of the metal sleeve 104 is X. The line source may be a plastic tube sealed at both ends and filled with water, in which a certain amount of radioactive source is thoroughly mixed, optionally a 70cm line source of NEMA2012 standard. In one embodiment, the length of the metal sleeve 104 is significantly greater than the length of the line source 103, such that at various positions of the detection assembly 102 during motion, all of the radiation collected by the PET collection device 108 is attenuated by the metal sleeve 104, thereby making the detection of sensitivity more accurate. The metal sleeve 104 completely wraps the line source 103, so that no gamma photon can be directly detected by the PET system without penetrating through the metal sleeve in the whole movement process, otherwise, part of the counts is directly counts with zero thickness of the metal sleeve, which affects the accuracy of fitting in the subsequent fitting and extrapolation processes and affects the final result of sensitivity. The detection assembly 102 is placed on the moving device 106, the detection assembly 102 is driven by the moving device 106 to perform linear motion parallel to the Z axis of the PET system, wherein the PET acquisition device 108 performs PET data acquisition while the detection assembly 102 performs linear motion. The motion device 106 may be a scanning bed device of a PET system, or may be another motion device for moving the detection assembly 102.
After the measurement is started, acquiring the acquisition starting time of the j-th acquisitionThe time when the line source 103 enters the AFOV is denoted as T j Acquiring the acquisition duration of the j acquisition, namely the time from the time that the line source 103 enters the AFOV to the time that the line source 103 completely leaves the AFOV, which is recorded as T j,acq Furthermore, the count number acquired by the acquisition means 108 is acquired. Determining the count rate R as a quotient of the count and the acquisition duration j For the counting rate R j Carrying out decay correction to obtain a count rate R without decay effect CORR，j Then through R CORR，j And the thickness X of the metal sleeve 104 j Non-decay count rate R when determining casing thickness as zero CORR,0 Finally through a non-decaying counting rate R CORR,0 And the activity of the line source 103.
Above-mentioned PET system sensitivity measuring device, detection element 102 through line source 103 and metal sleeve 104 constitution, utilize telecontrol equipment 106 to drive detection element 102 along the straight line that is on a parallel with PET system Z axle in the whole AFOV of PET system reciprocating motion, simultaneously gather the PET data through PET collection system 108, length according to the line source 103, PET system AFOV length and detection element 102's velocity of motion confirm the collection duration, confirm the sensitivity of PET system 100 according to gathering duration and the PET data of gathering again, the realization is through the line source and the metal sleeve that match with PET system axial field of vision length, sensitivity measuring's efficiency has been improved, the cost of the line source that custom length and PET system axial field of vision length match has been reduced.
In one embodiment, fig. 3 is a schematic diagram of a PET system sensitivity measuring device according to another embodiment of the present invention, and as shown in fig. 3, the moving device 106 includes an extension board 302 and a scanning bed 304 of the PET system, and the extension board 302 is connected to the scanning bed 304, and the connection may be a detachable connection or a rotatable connection, a sliding connection, or the like. The detecting element 102 is disposed on the extension board 302, and the scanning bed 304 drives the detecting element 102 to perform a linear motion parallel to the Z-axis of the PET system through the extension board 302. The extension plate 302 may be in the same plane as the scanning bed 304, or in a plane parallel to the plane of the scanning bed 304, and the shape of the extension plate 302 is not limited to a regular rectangular parallelepiped, for example, the extension plate 302 may be configured in a V shape in order to make the line source more stable during the movement. In addition, the extension plate 302 is also used to adjust the position of the detector assembly 102 within the AFOV, for example, by adjusting the relative position of the extension plate 302 and the scan bed 304 such that the detector assembly 102 is centered within the AFOV. In the case that the moving distance of the scanning bed 304 is limited, if the scanning bed 304 is directly selected as the moving device, the moving trace of the detecting assembly 102 cannot cover the entire AFOV, so in the present embodiment, the existing scanning bed 304 and the extension board 302 of the PET system are utilized, so that the moving trace of the detecting assembly 102 can cover the entire AFOV of the PET system 100. Through the movement device composed of the scanning bed 304 and the extension plate 302, on one hand, the existing scanning bed movement device in the PET system is used as a power source, so that the cost of additionally increasing the power device is reduced, and on the other hand, the position of the detection component 102 is adjusted through the extension plate, so that the sensitivity detection result of the PET system is more accurate.
In one embodiment, the detection assembly 102 is driven by a motion device to perform uniform linear motion parallel to the Z axis of the PET system. Under the condition that the detection assembly 102 moves at a constant speed, the acquisition starting time T j And acquisition duration T j，acq I.e. obtainable by the relative position of the line source 103 and the AFOV of the PET system. It should be noted that the uniform linear motion refers to the detection assembly 102 performing uniform motion within the AFOV range, and performing variable motion when the detection assembly is out of the AFOV range. FIG. 4 is a schematic diagram of a detection assembly moving at a constant speed according to an embodiment of the present invention, and as shown in FIG. 4, the detection assembly 102 reaches the constant speed at a time T mov At this time, the distance from the line source 103 to the AFOV is L, the constant velocity moving speed of the detecting assembly 102 is constant V, the line source is required to completely leave the system AFOV at the moment of departing from the constant velocity moving state, and the length of the AFOV is L AFOV . The acquisition start time can be calculated according to equation 1:
the acquisition duration of this time can be calculated according to equation 2:
and then, combining the collected count value, and determining the counting rate R through the quotient of the count value and the collection duration j For the counting rate R j Carrying out decay correction to obtain a count rate R without decay effect CORR，j Then through R CORR，j And the thickness X of the metal sleeve 104 j Non-decay count rate R when determining casing thickness as zero CORR,0 Finally through a non-decaying counting rate R CORR,0 And the activity of the line source 103.
In the embodiment of the embodiment, the detection assembly always moves linearly at a constant speed in the AFOV, and the acquisition starting time and the acquisition duration can be converted through the position information of the line source, so that the sensitivity measurement process of the PET system is higher in efficiency, more efficient in calculation and more accurate in detection result.
In one embodiment, the detector assembly 102 moves at a uniform speed along the AFOV central axis of the PET system 100 or along a straight line offset a predetermined distance from the AFOV central axis and parallel to the Z axis of the PET system. In order to make the detection result more accurate and comprehensive, the AFOV central axis of the PET system 100 and a straight line spaced from the AFOV central axis by a preset distance are selected as the motion trajectory of the detection assembly 102. Alternatively, the above-described measurement of the sensitivity of the PET system was performed at a distance AFOV center and 10cm off-center, selected according to NEMA NU 2-2012.
Optionally, the radionuclide used in the measurement of the PET system sensitivity measuring device may be sufficiently low in activity 18 F, the length of the line source 103 is L meas Typically 700 + -20 mm in length, the activity of the line source 103 being A cal，Meas The unit is MBq, and the time of activity measurement is T cal This time is also considered as the initial time. After the measurement is started, acquiring the acquisition starting time of the j acquisition, namely a line source103 entering AFOV, is recorded as T j Acquiring the acquisition duration of the j acquisition, namely the time from the time that the line source 103 enters the AFOV to the time that the line source 103 completely leaves the AFOV, which is recorded as T j,acq Furthermore, the count number acquired by the acquisition means 108 is acquired. It should be noted that in the case where the acquisition device 108 of the PET system needs to move back and forth to acquire the complete count, the acquisition duration must include the time during which the acquisition device 108 moves. Determining a count rate R j I.e. the quotient of the count and the acquisition duration. Then gradually increasing or gradually decreasing the thickness of the metal sleeve, and repeatedly recording the parameter T j And R j And according to formula 3 for the counting rate R j Carrying out decay correction to obtain a count rate R without decay effect CORR，j ：
Wherein, T 1/2 Is the half-life of the radionuclide.
Then according to formula 4 to R CORR，j And the thickness X of the metal sleeve 104 j Fitting and extrapolating to determine the non-decay count rate R when the casing thickness is zero CORR,0 ；
R CORR,j ＝R CORR,0 exp(-μ M 2X j ) Equation 4
Wherein, mu M Are parameters of coefficients that need to be determined in the fitting, which coefficients are allowed to be adjusted appropriately in the fitting process to compensate for small amounts of scatter that are difficult to avoid during testing.
Finally, the sensitivity of the PET system is determined according to equation 5:
according to another aspect of the present invention, there is also provided a PET system sensitivity measuring method applied to the PET system sensitivity measuring apparatus, fig. 5 is a flowchart of a PET system sensitivity measuring method according to an embodiment of the present invention, and as shown in fig. 5, the method includes:
step S510, acquiring the acquisition starting time when the line source 103 reaches the slice i, acquiring the acquisition duration according to the length of the line source and the movement speed of the detection assembly 102, and acquiring the counting rate in the acquisition duration;
step S520, decay correction is carried out on the counting rate of the slice i according to the acquisition starting time and the acquisition duration, the counting rates after decay correction of all slices in the axial view of the PET system are summed, and the counting rate without decay effect in the axial view is obtained;
and step S530, determining the sensitivity of the PET system according to the total thickness of the metal sleeve, the count rate without decay effect corresponding to the total thickness and the line source activity of the line source.
In steps S510 to S530, the AFOV is segmented into a plurality of slices, and the count rate acquired each time is the sum of the count rates of the slices. The moving speed of the detecting component 102 may be constant or variable, and preferably, for increasing the calculation efficiency, the detecting component 102 moves at a constant speed when passing through the slice i. FIG. 6 is a schematic diagram of the line source passing through slice i in accordance with one embodiment of the invention, as shown in FIG. 6, during the j acquisition, the i slice is at a distance Li from one end of the AFOV and the time t is when the line source has just reached slice i ia The moment when the line source just leaves slice i is t ib The moving speed of the line source 103 is V. Then for slice i in the j-th acquisition, the acquisition start time can be calculated as follows according to equation 6:
the acquisition duration can be calculated according to equation 7:
combining the formula 3, the counting rate R of the slice i in the j acquisition can be obtained j,i Carry out decayEquation 8 for variable correction:
summing the slices in the j acquisition, and obtaining the count rate of the j acquisition without decay effect according to formula 9:
replacing the metal casing 104 with different thicknesses, repeating the collecting process, fitting and extrapolating based on formula 4, and determining the counting rate R when the casing thickness is zero CORR,0 And calculating the sensitivity S of the PET system by equation 5 tot 。
The PET system sensitivity measuring method comprises the steps of forming a detection assembly by a line source and a metal sleeve, driving the detection assembly to reciprocate in the whole axial visual field of a PET system along a straight line parallel to the Z axis of the PET system by utilizing a movement device, simultaneously collecting PET data by a PET collecting device, determining the collection duration according to the line source length, the AFOV length of the PET system and the movement speed of the detection assembly, determining the sensitivity of the PET system according to the collection duration and the collected PET data, realizing the detection of the sensitivity of the PET system in a more flexible mode, avoiding the use of the line source and the metal sleeve matched with the axial visual field length of the PET system, improving the sensitivity measuring efficiency, and reducing the cost of the line source matched with the axial visual field length of the PET system.
In one embodiment, determining the sensitivity of the PET system based on the total thickness of the metal sleeve 104, the non-decay effect count rate corresponding to the total thickness, and the line source activity of the line source 103 comprises: changing the total thickness of the metal sleeve 104 by increasing or decreasing the number of the metal sleeve 104, and recording the total thickness and the count rate without decay effect corresponding to the total thickness; fitting and extrapolating according to the total thickness and the count rate without decay effect, and determining the count rate without decay effect when the total thickness is zero; and determining the sensitivity of the PET system according to the non-decay effect counting rate when the total thickness is zero and the activity of the line source. In this embodiment, the thickness of the metal sleeve 104 is changed by changing the number of the metal sleeves 104 around which the line source 103 is sleeved. Optionally, 5 coaxial metal sleeves 104 with different radii are used in the detection process, and 5 metal sleeves can be simultaneously sleeved outside the wire source 103, and the total thickness of the metal sleeves 104 is changed by sequentially increasing or decreasing the number of the metal sleeves. The embodiment can reduce the detection cost and increase the detection efficiency.
In one embodiment, fig. 7 is a flowchart of a PET system slice sensitivity measurement method according to an embodiment of the invention, and as shown in fig. 7, after determining the sensitivity of the PET system, the method includes:
and step S710, acquiring the ratio of the count rate after the decay correction of the slice i to the count rate without the decay effect in the axial view, and determining the sensitivity of the slice i according to the ratio and the sensitivity of the PET system. Let R 1,i For the count rate of the ith slice with the line source at the center, and R1 is the total sum count rate of all slices, the sensitivity of each slice can be calculated according to equation 10:
thereby making the sensitivity testing dimension of the PET system more complete.
It should be understood that, although the steps in the above-described flowcharts are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not limited to being performed in the exact order illustrated and, unless explicitly stated herein, may be performed in other orders. Moreover, at least some of the steps in fig. 5 and 7 may include multiple sub-steps or multiple stages, which are not necessarily performed at the same time, but may be performed at different times, and the order of performing the sub-steps or stages is not necessarily sequential, but may be performed alternately or alternately with other steps or at least some of the sub-steps or stages of other steps.
In one embodiment, a computer device is provided, which may be a terminal, and fig. 8 is a schematic diagram of a PET system sensitivity measuring computer device according to one embodiment of the present invention, and the internal structure diagram thereof may be as shown in fig. 8. The computer device includes a processor, a memory, a network interface, a display screen, and an input device connected by a system bus. Wherein the processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device comprises a nonvolatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of an operating system and computer programs in the non-volatile storage medium. The network interface of the computer device is used for communicating with an external terminal through a network connection. The computer program is executed by a processor to implement a PET system sensitivity detection method. The display screen of the computer equipment can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer equipment can be a touch layer covered on the display screen, a key, a track ball or a touch pad arranged on the shell of the computer equipment, an external keyboard, a touch pad or a mouse and the like.
It will be appreciated by those skilled in the art that the configuration shown in fig. 8 is a block diagram of only a portion of the configuration associated with the present application, and is not intended to limit the computing device to which the present application may be applied, and that a particular computing device may include more or less components than those shown, or may combine certain components, or have a different arrangement of components.
The device comprises a line source and a metal sleeve, the detection assembly is driven by the movement device to reciprocate in the whole axial visual field of the PET system along a straight line parallel to the Z axis of the PET system, PET data are collected by the PET collection device, the collection duration time is determined according to the length of the line source, the AFOV length of the PET system and the movement speed of the detection assembly, the sensitivity of the PET system is determined according to the collection duration time and the collected PET data, the sensitivity of the PET system is detected in a more flexible and higher-universality mode, the line source and the sleeve matched with the axial visual field length of the PET system are avoided, the sensitivity measurement efficiency is improved, and the cost of the line source matched with the length of the axial visual field of the PET system is reduced.
In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored, which, when being executed by a processor, carries out the PET system sensitivity measurement method described above.
The sensitivity measuring device and method of the PET system, the computer equipment and the storage medium utilize the detection assembly consisting of the line source and the metal sleeve, utilize the movement device to drive the detection assembly to reciprocate in the whole axial visual field of the PET system along the straight line parallel to the Z axis of the PET system, and simultaneously acquire PET data through the PET acquisition device, the acquisition duration is determined according to the line source length, the AFOV length of the PET system and the movement speed of the detection assembly, the sensitivity of the PET system is determined according to the acquisition duration and the acquired PET data, the sensitivity of detecting the whole body scanning PET with the ultra-long axial visual field through the existing standard length line source is realized, the line source and the metal sleeve matched with the axial visual field length of the PET system are avoided, the sensitivity measurement efficiency is improved, and the cost of the line source matched with the axial visual field length of the PET system in the customized length is reduced.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by hardware instructions of a computer program, which can be stored in a non-volatile computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. Any reference to memory, storage, database or other medium used in the embodiments provided herein can include non-volatile and/or volatile memory. Non-volatile memory can include read-only memory (ROM), Programmable ROM (PROM), Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms such as Static RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), Double Data Rate SDRAM (DDRSDRAM), Enhanced SDRAM (ESDRAM), Synchronous Link DRAM (SLDRAM), Rambus Direct RAM (RDRAM), direct bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (9)
1. The PET system sensitivity measuring device is characterized by comprising a detection assembly, a movement device and a PET acquisition device, wherein the detection assembly comprises a line source and a metal sleeve, the metal sleeve is sleeved outside the line source, the length of the metal sleeve is greater than that of the line source, the metal sleeve completely wraps the line source, and the axial view field length of the PET system is greater than 1.5 meters;
the detection assembly is placed on the moving device and is driven by the moving device to linearly move parallel to the Z axis of the PET system so as to reciprocate in the whole axial visual field of the PET system, the PET acquisition device acquires PET data while the detection assembly linearly moves, and all radiation acquired by the PET acquisition device at each position of the detection assembly in the moving process is attenuated by the metal sleeve;
the apparatus also includes a processor for determining the sensitivity of the PET system based on the line source length, the PET system axial field of view length, the speed of motion of the detection assembly, and the acquired PET data.
2. The apparatus of claim 1, wherein the moving device comprises an extension plate and a scanning bed of the PET system, the extension plate is connected with the scanning bed, the detection assembly is placed on the extension plate, and the scanning bed drives the detection assembly to perform linear motion parallel to the Z axis of the PET system through the extension plate.
3. The device according to claim 1, wherein the detection component is driven by the motion device to perform uniform linear motion parallel to the Z axis of the PET system.
4. The apparatus according to claim 3, wherein the detection assembly moves at a uniform speed along an axial center axis of a field of view of the PET system;
or alternatively
The detection assembly performs linear uniform motion along a Z axis which is deviated from the axial view central axis by a preset distance and is parallel to the PET system.
5. A PET system sensitivity measurement method, characterized in that the method is applied to the device of any one of claims 1 to 4, the method comprising:
acquiring the acquisition starting moment when the line source reaches a slice i, acquiring the acquisition duration according to the length of the line source and the movement speed of the detection assembly, and acquiring the counting rate within the acquisition duration;
carrying out decay correction on the counting rate of the slice i according to the acquisition starting time and the acquisition duration, and summing the count rates after the decay correction of each slice in the axial view of the PET system to obtain the count rate without decay effect in the axial view;
determining the sensitivity of the PET system according to the total thickness of the metal sleeve, the non-decay effect counting rate corresponding to the total thickness and the line source activity of the line source.
6. The method of claim 5, wherein after determining the sensitivity of the PET system, the method comprises:
and acquiring the ratio of the count rate after the decay correction of the slice i to the count rate without the decay effect in the axial field of view, and determining the sensitivity of the slice i according to the ratio and the sensitivity of the PET system.
7. The method of claim 5, wherein determining the sensitivity of the PET system based on the total thickness of the metal sleeve, the non-decay effect count rate corresponding to the total thickness, and the line source activity of the line source comprises:
changing the total thickness of the metal sleeves by increasing or decreasing the number of the metal sleeves, recording the total thickness and the count rate without decay effect corresponding to the total thickness;
determining a count rate without decay effect when the total thickness is zero according to the total thickness and the count rate without decay effect;
and determining the sensitivity of the PET system according to the non-decay effect counting rate when the total thickness is zero and the line source activity.
8. A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the steps of the method according to any of claims 5 to 7 are implemented when the computer program is executed by the processor.
9. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the method of any one of claims 5 to 7.
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