CN113440154A

CN113440154A - CT system device for ROI scanning

Info

Publication number: CN113440154A
Application number: CN202110806723.0A
Authority: CN
Inventors: 赵俊; 周玉府; 邓子恒; 张伟康
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2021-07-16
Filing date: 2021-07-16
Publication date: 2021-09-28
Anticipated expiration: 2041-07-16
Also published as: CN113440154B

Abstract

The invention discloses a CT system device aiming at ROI scanning, which comprises: one or more X-ray collimators, one or more anti-scatter grids, and one or more CT detector arrays. The one or more X-ray collimators are provided with openings, and the positions and the sizes of the openings can be designed according to specific scanning requirements; the one or more anti-scatter grids comprise a plurality of X-ray channel arrays whose positions and sizes match the corresponding X-ray collimator opening distributions; the one or more CT detector arrays include a plurality of CT detectors positioned to match a size and corresponding distribution of X-ray collimator openings. The invention has the advantages that high-quality and high-precision imaging of a local area is realized, and compared with the traditional grid, the grid matched with the X-ray collimator provided by the invention reduces the use amount of lead strips, reduces the weight of equipment and reduces the production cost.

Description

CT system device for ROI scanning

Technical Field

The invention relates to the field of CT scanning systems, in particular to a CT system device aiming at ROI scanning.

Background

The Computed Tomography (CT) technique has the characteristics of convenient operation, rapid scanning and the like, can obtain high-resolution images of internal tissue structures of human bodies under the condition of no wound, and is widely applied to the aspects of clinical disease diagnosis, focus screening, emergency treatment, follow-up examination and the like at present. For screening Of many diseases, CT scanning often focuses on a local Region (ROI), and does not require a full-area CT scan. In recent years, ROI scanning has been effective in diagnosing diseases such as pulmonary and gastric lesions, pancreatic diseases, and coronary atherosclerosis. However, current ROI scans only enable imaging of a single ROI region, such as the heart, isolated lung nodules, etc., and do not enable imaging and diagnosis of multiple ROI regions, such as multiple lung nodules, multiple renal cysts, etc. In addition, in the prior art, the purpose of limiting the field angle and the direction of the X-ray is achieved only by adjusting the X-ray collimator, and the anti-scatter grid is not correspondingly adjusted, so that the cost of the CT scanning equipment cannot be further reduced.

Accordingly, those skilled in the art are directed to developing a CT system apparatus for ROI scanning, which overcomes the above drawbacks.

Disclosure of Invention

In view of the above-mentioned defects in the prior art, the technical problem to be solved by the present invention is how to implement a CT system apparatus for ROI scanning, and the apparatus has the advantages of realizing high-quality and high-precision imaging of a local region, reducing the amount of lead bars used, reducing the weight of the apparatus, reducing the production cost, and the like.

To achieve the above object, the present invention provides a CT system apparatus for ROI scanning.

The invention is realized by the following technical scheme, and the CT system device for ROI scanning is characterized by comprising one or more X-ray collimators, one or more anti-scattering grids and one or more CT detector arrays, wherein X-rays sequentially pass through the one or more X-ray collimators and the one or more anti-scattering grids to reach the one or more CT detector arrays; the one or more X-ray collimators present an opening comprising a primary opening and a secondary opening; the one or more anti-scatter grids comprise a plurality of X-ray channel arrays including a primary array and a secondary array, the primary array having a position and size matching the primary opening distribution of the X-ray collimator and the secondary array having a position and size matching the secondary opening distribution of the X-ray collimator; the one or more CT detector arrays include a plurality of CT detectors including a primary CT detector and a secondary CT detector, the primary CT detector having a position and size matching the primary opening distribution of the X-ray collimator, and the secondary CT detector having a position and size matching the secondary opening distribution of the X-ray collimator.

Furthermore, the position of the main opening on the X-ray collimator corresponds to the position of the ROI under projection, so that X-rays can be transmitted to irradiate the ROI; the position of the sub-aperture on the X-ray collimator corresponds to the position of the region around the ROI region under the projection, and the X-ray can be transmitted to irradiate the region around the ROI region.

Further, the area of the main opening is larger than that of the sub opening, and the number of X-ray photons transmitted by the main opening is larger than that of the sub opening.

Further, the secondary openings are distributed at intervals of rows and columns, and the farther away from the primary openings, the smaller the area of the secondary openings, the more sparsely distributed.

Further, the X-ray channel array is formed by enclosing a plurality of detachable sheets, the position of the primary array on the anti-scatter grid corresponds to the position of the ROI under the projection, the primary array can pass the X-rays passing through the primary opening of the X-ray collimator and filter the scattered rays, the position of the secondary array on the anti-scatter grid corresponds to the position of the region around the ROI under the projection, and the secondary array can pass the X-rays passing through the secondary opening of the X-ray collimator and filter the scattered rays.

Further, the area of the primary array is larger than that of the secondary array, and the number of X-ray photons passed by the primary array is larger than that of the secondary array.

Further, the X-ray channels in the primary array are smaller in size than the X-ray channels in the secondary array, and the arrangement of the X-ray channels in the primary array is tighter than the arrangement of the X-ray channels in the secondary array.

Further, the secondary arrays are distributed at intervals of rows and columns, and the farther away from the primary array, the smaller the area of the secondary array, the more sparsely the distribution.

Further, the position of the primary CT detector on the detector array corresponds to the position of the ROI area under the projection, the primary CT detector receives the X-rays filtered through the primary array of the anti-scatter grid, the secondary CT detector is located elsewhere on the detector array, and the secondary CT detector receives the X-rays filtered through the secondary array of the anti-scatter grid.

Further, the size of the main CT detector is smaller than that of the sub-CT detectors, and the arrangement of the main CT detectors is more compact than that of the sub-CT detectors.

In a preferred embodiment of the present invention, when the X-ray collimator is used in a stationary CT system, there are a plurality of X-ray collimators corresponding to a plurality of X-ray sources one to one, and according to different positions of the ROI region at each projection angle, the area sizes of the main opening and the sub opening at the projection angle and the distribution pattern on the X-ray collimator are respectively designed, so that the positions and sizes of the main opening and the sub opening meet the requirements of local high-precision imaging.

In another preferred embodiment of the present invention, when the X-ray collimator is used in a general medical CT system, the position and size of the primary opening and the secondary opening of only one of the X-ray collimators are kept unchanged, and the position of the ROI needs to be moved before scanning so that the geometric relationship between the ROI and the imaging center is unchanged at each projection angle.

In another preferred embodiment of the present invention, when the anti-scatter grid is used in a stationary CT system, there are a plurality of anti-scatter grids corresponding to the plurality of X-ray sources and the plurality of X-ray collimators, and the positions and sizes of the primary array and the secondary array of the anti-scatter grid at each projection angle are respectively designed according to different structures of the X-ray collimators at the projection angle, so that scattered rays are sufficiently filtered, and the imaging quality is improved.

In another preferred embodiment of the invention, when the anti-scatter-grid is used in a general medical CT system, only one of the anti-scatter-grid, the primary array and the secondary array are positioned and dimensioned before scanning according to the configuration of the X-ray collimator in particular used.

In another preferred embodiment of the present invention, when the CT detector array is used in a stationary CT system, there are a plurality of different CT detector arrays corresponding to the plurality of X-ray sources, the plurality of X-ray collimators, and the plurality of anti-scatter grids, and the positions and the sizes of the primary CT detector and the secondary CT detector at each projection angle are respectively designed according to different structures of the X-ray collimators at the projection angle, so as to realize high resolution imaging of the ROI region.

In another preferred embodiment of the present invention, when the CT detector array is used in a general medical CT system, only one of the CT detector arrays is used, and the positions and sizes of the primary CT detector and the secondary CT detector are determined according to the structure of the X-ray collimator used specifically before scanning.

Compared with the prior art, the invention has the following advantages:

the invention provides a CT system aiming at single or multiple ROI scanning, which uses a matched X-ray collimator, an anti-scatter grid and a CT detector array to realize high-quality and high-precision imaging of a local area; compared with the traditional grid, the grid matched with the X-ray collimator provided by the invention reduces the usage amount of lead strips, reduces the weight of equipment and reduces the production cost.

The conception, the specific structure and the technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, the features and the effects of the present invention.

Drawings

FIG. 1 is a schematic diagram of the geometry of various components of a CT system apparatus at a certain projection angle;

FIG. 2 is a schematic diagram of an X-ray collimator for multiple ROI scanning;

FIG. 3 is a schematic diagram of an anti-scatter grid and CT detector array for multiple ROI scanning;

FIG. 4 is a schematic diagram of an X-ray collimator for a single ROI scan;

FIG. 5 is a schematic diagram of an anti-scatter grid and CT detector array for a single ROI scan.

Description of reference numerals: the X-ray source 1, the X-ray collimator 2, the anti-scatter grid 3, the detector array 4, the scanned object 5, the first ROI region 6, the second ROI region 7, the first main opening 8a, the second main opening 8b, the first sub opening 9a, the second sub opening 9b, the third sub opening 9c, the fourth sub opening 9d, the fifth sub opening 9e, the first main array 10a, the second main array 10b, the first sub array 11a, the second sub array 11b, the third sub array 11c, the fourth sub array 11d, the fifth sub array 11e, the main CT detector 12a and the sub CT detector 12 b.

Detailed Description

The technical contents of the preferred embodiments of the present invention will be more clearly and easily understood by referring to the drawings attached to the specification. The present invention may be embodied in many different forms of embodiments and the scope of the invention is not limited to the embodiments set forth herein.

In the drawings, structurally identical elements are represented by like reference numerals, and structurally or functionally similar elements are represented by like reference numerals throughout the several views. The dimensions and thicknesses of each component shown in the drawings are arbitrarily set forth. The thickness of the components may be exaggerated where appropriate in the figures to improve clarity.

The first embodiment is as follows:

as shown in figure 1, considering the geometrical relationship of an X-ray source 1, a scanned object 5 and a detector array 4 under a single projection angle, two local ROI (regions of interest) first ROI (region of interest) regions 6 and second ROI regions 7 exist, high-precision and high-quality reconstruction is needed, the first ROI regions 6 and the second ROI regions 7 are deviated from an imaging center, and the conventional X-ray collimator cannot realize multi-ROI scanning. The X-ray collimator 2 can adjust the field angle and the direction of X-rays, so that the X-rays just penetrate through the complete first ROI area 6 and the complete second ROI area 7, and multi-center local scanning is realized. According to the local reconstruction theory, sparse projections can be added in the surrounding areas of the first ROI area 6 and the second ROI area 7, and high-precision reconstruction of the first ROI area 6 and the second ROI area 7 is guaranteed by combining prior image information. Therefore, the X-ray collimator 2 according to the present invention needs to achieve two objectives: one is full sampling of the first ROI region 6 and the second ROI region 7, and two is sparse sampling of the surrounding regions of the first ROI region 6 and the second ROI region 7.

As shown in fig. 2, the X-ray collimator 2 is made of a metal plate having a certain thickness, and is made of a metal material that can effectively shield X-rays, such as lead or tungsten alloy. The X-ray collimator 2 has a plurality of openings, which are divided into

primary openings

8a and 8b and secondary openings 9a to 9e according to the function of the openings. The

main openings

8a and 8b function as: irradiating the first ROI area 6 and the second ROI area 7 with dense X-rays; the functions of the secondary openings 9a to 9e are: the surrounding regions of the first ROI region 6 and the second ROI region 7 are irradiated with sparse X-rays. The

primary openings

8a and 8b, which are both rectangular openings, have the largest area of all openings and are arranged offset from the center of the X-ray collimator 2, the position of the primary opening 8a on the X-ray collimator 2 corresponds to the position of the first ROI area 6 under the projection, and the position of the primary opening 8b on the X-ray collimator 2 corresponds to the position of the second ROI area 7 under the projection. The secondary openings 9a to 9e, which are all rectangular openings, have smaller areas than the

primary openings

8a and 8b, are distributed at other free positions on the X-ray collimator 2, and the positions of the secondary openings on the X-ray collimator 2 correspond to the positions of the surrounding regions of the first ROI region 6 and the second ROI region 7 under the projection.

The auxiliary openings 9a are distributed between the

main openings

8a and 8b and keep a certain distance with the

main openings

8a and 8b, and the auxiliary openings 9a are distributed at intervals of rows and columns and arranged in a 3 x 3 grid shape; the auxiliary openings 9b are distributed on the right side of the main opening 8b and keep a certain distance with the main opening 8b, and the auxiliary openings 9b are also distributed at intervals in rows and columns and are arranged in a 4 x 4 grid shape; the area of the secondary openings 9b is smaller than that of the secondary openings 9a, and the intervals between the rows of the secondary openings 9b are larger than those between the rows of the secondary openings 9a, so that the secondary openings 9b transmit more sparse X-rays than the secondary openings 9 a. The

auxiliary openings

9c, 9d and 9e are distributed on the left side of the main opening 8a and keep a certain distance with the main opening 8a, the areas of the three are gradually reduced from the right side to the left side, and the distribution intervals are gradually increased. The number of the auxiliary openings 9c is two, the number of the auxiliary openings 9d is three, the number of the auxiliary openings 9e is four, and the auxiliary openings are staggered in the vertical direction, so that the coverage rate of the X-ray in the vertical direction is guaranteed.

For adapting the X-ray collimator 2, the invention also provides a corresponding anti-scatter grid 3. In the CT scanning process, after the X-ray passes through the X-ray collimator 2, the field angle and direction thereof are modulated, but inevitably, the scattered X-ray generated by the scattering phenomenon affects the image quality. The anti-scattering grid 3 of the invention uses a thin plate made of metal materials such as lead, tungsten alloy and the like to surround and form a ray channel in a specific direction, and absorbs and shields scattered X rays, thereby improving the imaging quality. Because the X-ray radiation dose is low and the distribution is concentrated in local CT scanning, the anti-scattering grid 3 only needs to surround a ray channel above part of detection crystals, so that the weight of equipment is reduced, and the hardware cost is reduced.

As shown in fig. 3, the anti-scatter grid 3 is mounted on the detector array 4, and its base is made of a lightweight, low-cost composite material, such as high-temperature resistant plastic polyphenylene sulfide. The anti-scatter grid 3 is provided with the detachable X-ray channel array formed by enclosing a metal thin plate, and the X-ray channel array can be divided into

main arrays

10a and 10b and auxiliary arrays 11a to 11e according to the corresponding relation with the opening of the X-ray collimator 2. The

main arrays

10a and 10b function as: receives the dense X-rays passing through the

primary openings

8a and 8b of the X-ray collimator 2 and filters the scattered rays. The functions of the sub-arrays 11a to 11e are: receive the sparse X-rays passing through said secondary openings 9a to 9e of the X-ray collimator 2 and filter the scattered rays. The

main arrays

10a and 10b are both rectangular structures, have the largest total area, and are respectively formed by regularly arranging a certain number of X-ray channels, and the passing area of a single X-ray channel is certain. The secondary arrays 11a to 11e are all rectangular structures, the areas of the secondary arrays are smaller than those of the

primary arrays

10a and 10b, the secondary arrays are respectively formed by regularly arranging a certain number of X-ray channels, and the passing areas of the single X-ray channels are fixed. Wherein the size of the single X-ray channel in the main array is smaller than that of the single X-ray channel in the secondary array, and the arrangement of the X-ray channels in the main array is tighter than that of the X-ray channels in the secondary array.

Fig. 3 also shows the CT detector array 4 associated with the X-ray collimator 2 of fig. 2, wherein the primary CT detector 12a corresponds to the first and second ROI areas 6, 7 and the secondary CT detector 12b corresponds to the region surrounding the first and second ROI areas 6, 7. The primary CT detector 12a is smaller in size than the secondary CT detector 12b and is more closely spaced. Therefore, the reconstructed images of the first ROI region 6 and the second ROI region 7 have higher resolution and better quality.

From the viewpoint of CT scanning, considering that the position relationship between the first ROI region 6 and the second ROI region 7 and the imaging center is always changed at each projection angle, the embodiment is suitable for a stationary CT system, and the X-ray collimator 2 in front of each X-ray source 1 needs to be individually designed according to the positions of the first ROI region 6 and the second ROI region 7 at each projection angle, so that the positions and sizes of the

main openings

8a and 8b and the auxiliary openings 9a to 9e meet the requirements of local high-precision imaging. In addition, the design of the matched anti-scatter-grid 3 and the CT detector array 4 is also required. The

main apertures

8a and 8b transmit the same X-ray as that of the conventional CT scan, or the X-ray generated by using higher tube current and tube voltage only passes through the first ROI region 6 and the second ROI region 7, so that the first ROI region 6 and the second ROI region 7 are irradiated normally or at higher intensity, and high-quality and high-precision imaging of the first ROI region 6 and the second ROI region 7 can be obtained. The secondary apertures 9a to 9e have smaller areas than the

primary apertures

8a and 8b and have spaces between rows, and the secondary apertures 9a to 9e transmit more sparse X-rays than the

primary apertures

8a and 8b and transmit more sparse X-rays farther away from the

primary apertures

8a and 8b, so that the surrounding areas of the first ROI region 6 and the second ROI region 7 are irradiated with low intensity and the surrounding areas have lower imaging quality. As the invention focuses on the requirement of local CT scanning, the imaging mode ensures high reconstruction quality of the first ROI area 6 and the second ROI area 7, enables the image quality of other adjacent areas to assist medical diagnosis, and simultaneously realizes low radiation dose of CT scanning by sparse projection of the surrounding areas.

Example two:

the X-ray collimator 2, the anti-scatter grid 3 and the CT detector array 4 can be adapted to the existing medical CT system. Because the existing medical CT system generally has a single X-ray source structure, the imaging center of the medical CT system is always kept at the center of the stand in the rotating process, and therefore the position of the ROI needs to be moved, and the geometric relationship between the medical CT system and the imaging center under each projection angle is not changed.

Considering the general scenario in disease diagnosis, common single ROI regions are organs or tissues such as heart, lung nodules, blood vessels, liver, etc., and the ROI regions need to be moved to the center of the gantry before scanning. The location of the ROI region should be aided by a priori knowledge, such as the image of the previous scan, a universally applicable human anatomy model, the doctor's empirical judgment, etc. After the ROI is moved to the imaging center, the invention provides the following embodiments aiming at the problem of local high-precision imaging of a single ROI:

as shown in fig. 4, the X-ray collimator 2 has a plurality of openings, which are divided into the main opening 8a and the sub-openings 9a to 9d according to the opening function. The main openings 8a are rectangular openings, and the number of the main openings is two, and the main openings are located in the center of the X-ray collimator 2. The auxiliary openings 9a are rectangular openings, four in number, distributed on the right side of the main opening 8a, and keep a certain distance from the main opening 8 a. The secondary openings 9a are arranged in a grid pattern of 2 × 2, and are spaced in rows and columns. The auxiliary openings 9b are rectangular openings, the number of the auxiliary openings is nine, the auxiliary openings are distributed on the right side of the auxiliary opening 9a, and a certain distance is kept between the auxiliary openings and the auxiliary opening 9 a. The secondary openings 9b are arranged in a 3 × 3 grid pattern at intervals of rows and columns. The auxiliary openings 9c are rectangular openings, sixteen in number, distributed on the right side of the auxiliary openings 9b, and keep a certain distance from the auxiliary openings 9 b. The secondary openings 9c are arranged in rows and columns at intervals, and are arranged in a 4 × 4 grid. The auxiliary openings 9d are rectangular openings, are eighteen in number, are distributed on the left side of the main opening 8a, and keep a certain distance from the main opening 8 a. The secondary apertures 9d are spaced in rows and columns, and unlike the arrangement of the secondary apertures 9a to 9c on the right, there is a staggering between the rows of the secondary apertures 9d, i.e. four apertures in each of the first and third rows and five apertures in each of the second and fourth rows. The areas of the openings decrease in order from the main opening 8a to the sub-openings 9a, 9b, 9d, 9c in view of the areas of the openings. In view of the arrangement of the openings, the

secondary openings

9a, 9b, 9c on the right side of the primary opening 8a have successively increasing row-to-row spacings.

As shown in fig. 5, the anti-scatter grid 3 associated with the X-ray collimator 2 in fig. 4 comprises a plurality of the X-ray channel arrays, which are divided into the primary array 10a and the secondary arrays 11a to 11d according to the corresponding relationship with the openings of the X-ray collimator 2. The main array 10a is a rectangular array, and the number of the main array is two, and the main array is located at the center of the grid. The sub-arrays 11a are rectangular arrays, four in number, distributed on the right side of the main array 10a, and spaced from the main array 10a by a certain distance. The sub-arrays 11a are arranged in a grid of 2 × 2 rows and columns at intervals. The sub-array 11b is a rectangular array, nine in number, distributed on the right side of the sub-array 11a, and kept at a certain distance from the sub-array 11 a. The sub-arrays 11b are arranged in a 3 × 3 grid pattern at intervals of rows and columns. The sub-array 11c is a rectangular array, sixteen in number, distributed on the right side of the sub-array 11b, and keeps a certain distance from the sub-array 11 b. The sub-arrays 11c are arranged in a 4 × 4 grid pattern, and are spaced in rows and columns. The auxiliary arrays 11d are rectangular arrays, are eighteen in number, are distributed on the left side of the main array 10a, and keep a certain distance from the main array 10 a. The rows and columns of the secondary array 11d are staggered, i.e., four arrays in each of the first and third rows and five arrays in each of the second and fourth rows. From the array area, the area decreases in order from the main array 10a to the sub-arrays 11a, 11b, 11d, 11 c. In view of the array arrangement, the sub-arrays 11a, 11b, 11c on the right side of the main array 10a have sequentially increasing row-to-row intervals. In addition, the sizes of the individual X-ray channels of the sub-arrays 11a to 11d are all the same, while the size of the individual X-ray channel of the main array 10a is smaller than and more closely arranged than the size of the individual X-ray channels of the sub-arrays 11a to 11 d.

Fig. 5 also shows a CT detector array 4 associated with the X-ray collimator 2 shown in fig. 4, wherein the primary CT detector 12a corresponds to the region of the ROI and the secondary CT detector 12b corresponds to the region around the ROI. The primary CT detector 12a is smaller in size than the secondary CT detector 12b and is more closely spaced. Therefore, the reconstructed image of the ROI has higher resolution and better quality.

By means of the X-ray collimator 2, the radiation X-ray can meet the distribution requirements of overall sparseness and local density of targets. The ROI region and the ROI surrounding region in the scanned object are defined in terms of X-ray density (SUR1, SUR2, SUR 3). First, the ROI region is the scanned region, such as the heart, lung nodule, blood vessel, etc. The center of the ROI area is searched, concentric circles are sequentially drawn outwards, the boundary of the first concentric circle corresponds to the boundary of the area where the object is scanned after the X-ray passes through the main opening 8a, the boundary of the second concentric circle corresponds to the boundary of the area where the object is scanned after the X-ray passes through the auxiliary opening 9a, the boundary of the third concentric circle corresponds to the boundary of the area where the object is scanned after the X-ray passes through the auxiliary opening 9b, and the boundary of the fourth concentric circle corresponds to the boundary of the area where the object is scanned after the X-ray passes through the auxiliary opening 9 c. Thus, the ROI region is the first concentric circle; the ROI surrounding region SUR1 is a circular ring region between the first concentric circle and the second concentric circle, and surrounds the ROI region; the ROI surrounding region SUR2 is a circular ring region between the second concentric circle and the third concentric circle, and surrounds the SUR1 region; the ROI surrounding region SUR3 is a circular ring region between the third concentric circle and the fourth concentric circle, and surrounds the SUR2 region.

From the perspective of CT scanning, the X-ray transmitted through the main opening 8a is the same as that of conventional CT scanning, or the X-ray generated by high tube current and high tube voltage only passes through the ROI region, so that the ROI region is irradiated with normal intensity or higher intensity, and therefore the X-ray transmitted through the main opening 8a is normal or higher dose, and high-quality and high-precision imaging of the ROI region can be obtained. The area of the sub aperture 9a is smaller than that of the main aperture 8a, and the rows and columns of the sub aperture 9a are spaced apart from each other, so that the X-rays transmitted through the sub aperture 9a are more sparse than those transmitted through the main aperture 8a, and the SUR1 in the ROI surrounding region is irradiated with a lower intensity, whereby higher-quality and higher-precision imaging in the SUR1 region can be obtained. The area of the sub apertures 9b is smaller than that of the sub apertures 9a, and the intervals between the rows of the sub apertures 9b are larger than those of the sub apertures 9a, and the X-rays transmitted through the sub apertures 9b are more sparse than those of the sub apertures 9a, so that the SUR2 region is irradiated with a lower intensity, and imaging with medium quality and medium accuracy in the SUR2 region can be obtained. The sub apertures 9c are smaller in area than the sub apertures 9b, and the intervals between the rows of the sub apertures 9c are larger than those of the sub apertures 9b, so that the X-rays transmitted through the sub apertures 9c are more sparse than those of the sub apertures 9b, and the irradiation of the SUR3 region with the lowest intensity is achieved, and thus, low-quality and low-precision imaging of the SUR3 region can be achieved. Since the present invention focuses on the local CT scanning requirement, the above-mentioned imaging mode ensures high reconstruction quality of the ROI region, and also enables the image quality of other surrounding regions (SUR1, SUR2, SUR3 regions) to assist medical diagnosis. In addition, the closer the region is to the ROI region, the higher the imaging quality thereof, and the more effective diagnostic information can be provided. This embodiment reduces the X-ray exposure of the region around the ROI, enabling a low radiation dose for CT scanning.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims

1. A CT system apparatus for ROI scanning, comprising one or more X-ray collimators, one or more anti-scatter grids, one or more CT detector arrays, X-rays sequentially passing through the one or more X-ray collimators, the one or more anti-scatter grids to the one or more CT detector arrays; the one or more X-ray collimators present an opening comprising a primary opening and a secondary opening; the one or more anti-scatter grids comprise a plurality of X-ray channel arrays including a primary array and a secondary array, the primary array having a position and size matching the primary opening distribution of the X-ray collimator and the secondary array having a position and size matching the secondary opening distribution of the X-ray collimator; the one or more CT detector arrays include a plurality of CT detectors including a primary CT detector and a secondary CT detector, the primary CT detector having a position and size matching the primary opening distribution of the X-ray collimator, and the secondary CT detector having a position and size matching the secondary opening distribution of the X-ray collimator.

2. The CT system for scanning ROI according to claim 1, wherein a position of said primary opening on said X-ray collimator corresponds to a position of a ROI area under the projection, so as to transmit X-rays to irradiate said ROI area; the position of the sub-aperture on the X-ray collimator corresponds to the position of the region around the ROI region under the projection, and the X-ray can be transmitted to irradiate the region around the ROI region.

3. The CT system apparatus for ROI scanning according to claim 2, wherein an area of the main opening is larger than an area of the sub opening, and a number of the X-ray photons transmitted by the main opening is larger than a number of the X-ray photons transmitted by the sub opening.

4. The CT system apparatus for ROI scanning according to claim 2, wherein the secondary openings are spaced in rows and columns, and the further away from the primary openings, the smaller the area of the secondary openings, the more sparsely distributed.

5. The CT system apparatus for ROI scanning according to claim 1, wherein the X-ray channel array is formed by enclosing a plurality of detachable sheets, a position of the primary array on the anti-scatter grid corresponds to a position of the ROI area under the projection, the primary array is capable of passing the X-rays passing through the primary opening of the X-ray collimator and filtering scattered rays, a position of the secondary array on the anti-scatter grid corresponds to a position of a region around the ROI area under the projection, and the secondary array is capable of passing the X-rays passing through the secondary opening of the X-ray collimator and filtering the scattered rays.

6. The CT system apparatus for ROI scanning according to claim 5, wherein an area of the primary array is larger than an area of the secondary array, and a number of the X-ray photons passed by the primary array is larger than a number of the X-ray photons passed by the secondary array.

7. The CT system apparatus for ROI scanning according to claim 5, wherein the X-ray channels in the primary array have a smaller size than the X-ray channels in the secondary array, and wherein the arrangement of the X-ray channels in the primary array is tighter than the arrangement of the X-ray channels in the secondary array.

8. The CT system apparatus for ROI scanning according to claim 5, wherein the sub-arrays are spaced in rows and columns, and the further away from the main array, the smaller the area of the sub-arrays, the more sparsely distributed.

9. The CT system apparatus for ROI scanning of claim 1, wherein a position of the primary CT detector on the detector array corresponds to a position of the ROI region under the projection, the primary CT detector receives the X-rays filtered through the primary array of the anti-scatter grid, the secondary CT detector is located elsewhere on the detector array, and the secondary CT detector receives the X-rays filtered through the secondary array of the anti-scatter grid.

10. The CT system apparatus for ROI scanning according to claim 9, wherein a size of the main CT detector is smaller than a size of the sub-CT detector, and the main CT detector is arranged more closely than the sub-CT detector.