THREE-DIMENSIONALLY HETEROGENEOUS PET SYSTEM

Abstract

The application provides a three-dimensionally heterogeneous PET system comprising at least two heterogeneous detector modules, each comprising at least two kinds of crystal strips closely arranged to form different detection performances levels for different kinds of crystal strips and same detection performances levels for same kind of crystal strips. Parameters of detection performances of crystal strips comprise energy resolution, density, size and light output, wherein different detection performances levels for crystal strips comprise one or more of parameters of detection performances of crystal strips being in different levels. Compared with a high spatial resolution PET system, the application effectively reduces manufacturing costs of a PET system without significantly reducing spatial resolution thereof. Compared with an ordinary spatial resolution PET system, it improves spatial resolution of a PET system by slightly increasing its cost, and can also provide imaging field of view with high spatial resolution in radial direction.

Claims

1. A three-dimensionally heterogeneous PET system comprising at least two heterogeneous detector modules each of which includes at least two kinds of crystal strips; the crystal strips are closely arranged and are provided with different detection performances levels for different kinds of crystal strips and same detection performances levels for same kind of crystal strips; parameters of detection performances of crystal strips comprise energy resolution, density, size and light output, wherein different detection performances levels for crystal strips comprise one or more of the parameters of detection performances of crystal strips being in different levels.

2. The three-dimensionally heterogeneous PET system according to claim 1, wherein the heterogeneous detector module includes several cuboids first crystal strips and second crystal strips which are closely arranged in sequence to construct a cuboids and divide the heterogeneous detector module into two parts one of which is constituted by the first crystal strips another of which is constructed by the second crystal strips.

3. The three-dimensionally heterogeneous PET system according to claim 2, wherein the first strips crystal and the second crystal strips are in different sizes, wherein the size of the first crystal strips is 4.25 mm×4.25 mm×10 mm and the size of the second crystal strips is 2.125 mm×2.125 mm×10 mm.

4. The three-dimensionally heterogeneous PET system according to claim 2, wherein the first crystal strips amount to 80 and are arranged by 8 columns and 10 lines; the second crystal strips amount to 320 and are arranged by 16 columns and 20 lines.

5. The three-dimensionally heterogeneous PET system according to claim 1, wherein the heterogeneous detector modules form an annular structure in the space.

6. The three-dimensionally heterogeneous PET system according to claim 5, wherein the crystal strips are provided with wedge-shape and different kinds of crystal strips are closely arranged in sequence to constitute an arc-shaped heterogeneous detector module, multiple heterogeneous detector modules constitute an annular three-dimensionally heterogeneous PET system.

7. The according to claim 5, comprising 16 heterogeneous detector modules, which constitute an annular three-dimensionally heterogeneous PET system with the inner diameter being about 213.66 mm and the axial length being about 68 mm that is the length perpendicular to the direction of cross section of the annular structure.

8. The three-dimensionally heterogeneous PET system according to claim 1, wherein the heterogeneous detector modules amount to two and are arranged parallel and aligned to each other in the vertical direction so as to form a flat three-dimensionally heterogeneous PET system.

9. The three-dimensionally heterogeneous PET system according to claim 1, wherein the material of crystal strips is one or more selected from the group consisting of LaBr.sub.3, LSO, LYSO, LuYAP, BaF.sub.2, GSO, LFS and LuI.sub.3.

10. The three-dimensionally heterogeneous PET system according to claim 1, wherein a prosthesis is provided which includes a chassis and several first targets and second targets with different sizes distributed on the two sides of chassis respectively and oppositely.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] These and other features and advantages of this application will become more apparent to those skilled in the art from the detailed description of preferred embodiment. The drawings that accompany the description are described below.

[0024] Wherein, FIG. 1 is a structure schematic drawing of the detector modules of a three-dimensionally heterogeneous PET system according to an embodiment of the present application.

[0025] FIG. 2 is a general perspective view of the detector modules of the three-dimensionally heterogeneous PET system according to FIG. 1.

[0026] FIG. 3 is a schematic view of the prosthesis of the three-dimensionally heterogeneous PET system according to a preferred embodiment of the present application.

[0027] FIG. 4 is a flow diagram of use of the three-dimensionally heterogeneous PET system according to a preferred embodiment of the present application.

[0028] FIG. 5 is a schematic perspective view of the detector module of the three-dimensionally heterogeneous PET system according to another embodiment of the present application.

[0029] FIG. 6 is a schematic perspective view of the detector module of the three-dimensionally heterogeneous PET system according to yet another embodiment of the present application.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The followings are used to further illustrate the present application with specific embodiments. It should be understood that the following embodiments is only used to explain the present application but not to limit the scope of the present application.

[0031] FIG. 1 is a layout diagram of a detector module of a three-dimensionally heterogeneous PET system according to an embodiment of the present application. As shown in FIG. 1, the three-dimensionally heterogeneous PET system 1 is provided with at least three heterogeneous detector modules 10. In order to simplify the description, the embodiment showed in FIG. 1 only illustrates one heterogeneous detector modules 10 at the top of the three-dimensionally heterogeneous PET system 1. The heterogeneous detector modules 10 are arranged in a ring in space and each of them can either contact with each other or keep separating from each other. The skilled person in the art can determine whether the heterogeneous detector modules 10 need to be contact with each other based on actual requirements of use. Preferably, as shown in FIG. 1, the three-dimensionally heterogeneous PET system 1 of the present application includes eight heterogeneous detector modules 10, which contact with each other and form a closed annular structure in space; FIG. 1 only shows one heterogeneous detector module 10. Specifically, when a three-dimensional coordinate system is established using the center of the ring as the point O, each heterogeneous detector module 10 includes a top surface arranged far away from the center point O and an opposite bottom surface arranged adjacent to the center point O. The bottom surfaces of two adjacent heterogeneous detector modules 10 contact with each other to form an annular structure. In the embodiment shown in FIG. 1, the eight heterogeneous detector modules 10 are divided into two symmetrical annular structures by the plane XOY, one of which is a high resolution detection ring and another one is an ordinary resolution detection ring. The positions of the annular structure in the positive and negative direction of the Z-axis can be changed according to the requirements. The alternate arrangement of annular structures can also be designed, such as, high resolution detection ring-ordinary resolution detection ring-high resolution detection ring.

[0032] It should be noted that the performances of the crystal strips in the three-dimensionally heterogeneous PET system 1 are exactly the same as for any arbitrary cross section that parallels to the plane XOY. That is to say, the whole three-dimensionally heterogeneous PET system 1 can be divided into multiple rings along the different planes XOY in the Z-axis. Wherein, the performance parameters of the crystal strips are exactly the same within each of rings. However, the performance parameters of the crystal strips between each of rings can have one or more with differences.

[0033] The heterogeneous detector module 10 of the present PET system 1 includes at least two kinds of crystal strips with detection performances in different levels. The detection performance parameters include energy resolution, density, size and light output, etc. Since the detection performances of the crystal strips are divided into several levels according to the relevant indexes, the above mentioned detection performances on different levels means specifically that one or more of the performance parameters of the crystal strips are on different levels. It should be noted that the crystal strips are usually cut into cuboids, but other shapes, such as wedges, are also available in some certain situations. Actually, the skilled person in the art can choose different shapes of crystal strips as desired.

[0034] FIG. 2 is a general perspective view of the heterogeneous detector modules 10 of the three-dimensionally heterogeneous PET system 1 according to FIG. 1. In the embodiment of FIG. 2, the heterogeneous detector module 10 includes several first crystal strips 11 and second crystal strips 12 in the shape of cuboids. The detection performances of the first crystal strips 11 and the second crystal strips 12 are on different levels. Particularly, multiple first crystal strips 11 with the same detection performance are provided along the positive direction of Z-axis and multiple second crystal strips 12 with the same detection performance are provided along the negative direction of Z-axis. The first crystal strips 11 and the second crystal strips 12 are closely arranged in sequence to form a heterogeneous detector module 10 with the shape of a cuboids.

[0035] The material of the crystal strips used by the present heterogeneous detector modules 10 can be selected from the group consisting of LaBr.sub.3, LSO, LYSO, LuYAP, BaF.sub.2, GSO, LFS, LuI.sub.3 and the like. The crystal strips of the present heterogeneous detector modules 10 are provided with different sizes which result in different performance levels. Furthermore, the crystal strips with different size can be made of crystals of either same material or different materials in order to make the crystal strips have different performance levels because different performance levels of the crystal strips can be obtained by changing the parameters of the crystal strips.

[0036] FIG. 3 is a general view of a prosthesis 40 of the three-dimensionally heterogeneous PET system according to a preferred embodiment of the present application. The prosthesis 40 includes a chassis 41 on which several first targets 42 and second targets 43 are distributed. The first targets 42 and the second targets 43 are provided with different sizes and are respectively and oppositely distributed on the two sides of the chassis. In the embodiment of FIG. 3, the size of the first targets 42 distributed in the left half is larger than that of the second targets 43 distributed in the right half as shown in the Fig. It is certainly that the shape of the prosthesis 40 and the distribution of the targets on it can be selected with other shapes or other distribution according to the requirement of researches or applications by the skilled person in the art.

[0037] FIG. 4 is a use flow diagram of the three-dimensionally heterogeneous PET system 1 of the present application. As shown in FIG. 4, the method of using the three-dimensionally heterogeneous PET system 1 according to the present application includes the following steps: establishing a detector module 51, setting up a three-dimensionally heterogeneous PET system 52, arranging a prosthesis 53 correctly, data acquisition and processing 54 and image reconstruction 55.

[0038] The step of establishing a detector module 51 is illustrated by the example of the heterogeneous detector module 10 as shown in FIG. 2. When establishing a heterogeneous detector module 10, two sizes of the crystal strips are adopted, namely, the first crystal strips 11 sized with 4.25 mm×4.25 mm×10 mm and the second crystal strips 12; the sized with 2.125 mm×2.125 mm×10 mm. It should be noted that the crystal strips of this embodiment use the same material and different sizes just in order to make the spatial intrinsic resolution of the heterogeneous detector module different. However, it is not limited to the change of the size of crystal strips, any way may cause changes in aspect of the performance parameters of the crystal strips meets the need, such as changes in the size of crystal strips or changes in the material of crystal strips, etc. When establishing a heterogeneous detector module 10 as shown in FIG. 2, in particular, the part of the heterogeneous detector module 10 distributed in the positive direction of Z-axis all uses the first crystal strips 11 in the size of 4.25 mm×4.25 mm×10 mm, and the other part of which distributed in the negative direction of Z-axis all uses the second crystal strips 12 in the size of 2.125 mm×2.125 mm×10 mm. In fact, the crystal strips in a single heterogeneous detector module 10 is provided with a large number. For the convenience of illustration, the crystal strips showed by FIG. 2 do not present the actual number of the crystal strips in a single heterogeneous detector module 10. In practice, the first crystal strips 11 are distributed along the Z-axis by 10 columns which direction is the same as the Z-axis, along the X-axis by 8 lines which direction is the same as the X-axis, and the total amount of the first crystal strips 11 is 80. While the second crystal strips 12 are distributed along the Z-axis by 20 columns which direction is the same as the Z-axis, along the X-axis by 16 lines which direction is the same as the X-axis, and the total amount of the second crystal strips 12 is 320. Thus, a single heterogeneous detector module 10 includes 80 first crystal strips 11 in a relative big size and 320 second crystal strips 12 in a relative small size. It should be understood that the number of crystal strips in FIG. 2 is used to exemplify the preferred embodiment of the present application. That means the numbers of the first crystal strips and the second crystal strips of the present application can both be changed as well as the changes on numbers of the kinds of the crystal strips.

[0039] In the step of establishing the heterogeneous PET system 52, multiple heterogeneous detector modules 10 are provided to establish an annular, flat, compact, uniformly-spaced, irregular or other form heterogeneous PET system according to the characteristics of the tested body. Preferably, 16 heterogeneous detector modules 10 are used to establish a compact three-dimensionally heterogeneous PET system 1 which is sized with the inner diameter of about 213.66 mm and the axial length of 68 mm that is the length parallel to the Z-axis as shown in FIG. 2.

[0040] An arrangement of the prosthesis is required to be arranged correctly in the three-dimensionally heterogeneous PET system. In a three-dimensionally heterogeneous PET system, assuming the number of the types of crystal strips is m, at least m−1 planes parallel to the plane XOY divide the three-dimensionally heterogeneous PET system 1 into m−1 parts wherein the detection performance parameters of crystal strips are exactly the same in same part and are different in different parts. In the disc-shaped prosthesis as shown in FIG. 3, bounded by the X axis, the size of the first group of targets 42 of the prosthesis located in the part of positive direction of Z-axis is relatively big and the size of the second group of targets 43 of the prosthesis located in the part of negative direction of Z-axis is relatively small. Apparently, the region division is obvious. When arranging the prosthesis, the second group of targets 43 in a relative small size is placed in the view with a relatively high spatial resolution and the first group of targets 42 in a relative big size is placed in the view with an ordinary spatial resolution. In a word, the prosthesis is required to be arranged to guarantee the different targets of the prosthesis being located in the different imaging field of view of the three-dimensionally heterogeneous PET system. In addition, when imaging the prosthesis, the diameter n of prosthesis (as shown in FIG. 3) shall not exceed the axial length of the heterogeneous detector module that is the length parallel to the Z axis as shown in FIG. 2.

[0041] In the step of data acquisition and processing 54, an electronics system including front-end and a computer system for data processing and image reconstruction are provided for choosing time window and energy window and the calculating time meeting, energy meeting, time resolution, energy resolution and so on. The electronics system in the present application only needs to acquire the time information, energy information and location information of the event. Thus any electronics design if only meeting these requirements can be applied to the present application.

[0042] In the step of image reconstruction 55, the three-dimensionally heterogeneous PET system can conduct image reconstruction by using a variety of reconstruction methods including Maximum Likelihood Expectation Maximization algorithm (ML-EM algorithm), Ordered Subsets Expectation Maximization algorithm (OSEM algorithm) and relatively simple direct backprojection algorithm, such as FBP. The reconstruction method is not unique and ML-EM algorithm and OSEM algorithm are preferably used in the image reconstruction in the present application.

[0043] The present application uses heterogeneous detector module to construct a three-dimensionally heterogeneous PET system. It should be understood that the shape of the PET system is not only limited to be annular but also flat, compact, uniformly-spaced, irregular or other shape by using heterogeneous detector module according to the characteristics of the tested body. FIG. 5 is a general perspective view of the heterogeneous detector module 20 of the three-dimensionally heterogeneous PET system according to another embodiment of the present application. In the embodiment as shown in FIG. 5, the heterogeneous detector module 20 of the present three-dimensionally heterogeneous PET system includes several first crystal strips 21, several second crystal strips 22 and several third crystal strips 23 which are all cuboid-shaped with different sizes and different detection performance levels. In specifically, the first crystal strips 21, the second crystal strips 22 and the third crystal strips 23 are closely arranged in sequence and constitute a flat heterogeneous detector module 20. The two such heterogeneous detector modules 20 on top and the bottom respectively are arranged parallel to each other and aligned to each other in the vertical direction, thus a flat heterogeneous PET system is formed.

[0044] FIG. 6 is a general perspective view of the heterogeneous detector module 30 of the three-dimensionally heterogeneous PET system according to yet another embodiment of the present application. In this embodiment, the heterogeneous detector module 30 includes several first crystal strips 31 and several second crystal strips 32 both in wedge shape and with different sizes have different detection performance levels. In specifically, the first crystal strips 31 and the second crystal strips 32 are closely arranged in sequence and constitute an arc-shape heterogeneous detector module 30. Multiple such heterogeneous detector modules 30 can constitute an annular heterogeneous PET system.

[0045] The three-dimensionally heterogeneous PET system provided by the present application uses a unique way of construction, namely, uses a variety of crystal strips with different performances to construct the heterogeneous detector module. Under the condition of the same structure, the present application can effectively reduce the manufacturing cost of the whole PET system without obviously reducing the spatial resolution of the PET system compared with the high spatial resolution PET system, and can improve the spatial resolution of the PET system only by increasing relative small cost and provide part imaging field of views with high spatial resolution in radial direction compared with the ordinary spatial resolution PET system. In addition, the present application can take advantage of combining a high performance detector module with a conventional PET system based on the normal PET system, so as to restructure a new heterogeneous PET system conveniently.

[0046] Moreover, the three-dimensionally heterogeneous PET system can also flexibly adjust the placement of the living according to the imaging characteristics of different organs of the living in order to image the living and meet the requirements of the corresponding regions in aspect of spatial resolution.

[0047] The foregoing application has been described in accordance with the relevant legal standard, thus the description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and do come within the scope of the application. Accordingly, the scope of legal protection afforded this application can only be determined by studying the following claims.