CN118285820A - SPECT system with extended axial FOV - Google Patents

Abstract

SPECT systems with an extended axial FOV are provided. A system comprising: a housing having a first end and a second end; a SPECT detector disposed in the housing; a first bracket; a first coupling coupled to the first end of the housing and the first bracket; a second bracket defining a hole; and a second coupling coupled to the second end of the housing and the second bracket, wherein the housing is disposed between the first bracket and the second bracket.

Description

SPECT system with extended axial FOV

Cross Reference to Related Applications

The present application claims priority from U.S. provisional patent application No. 63/478,512, filed on 1/5/2023, the contents of which are incorporated herein by reference for all purposes.

Background

In Single Photon Emission Computed Tomography (SPECT) imaging, a radioactive material is administered to a subject, and the resulting gamma radiation emitted from the subject is detected by a SPECT detector. Gamma radiation is detected at various locations of the detector and the detector generates a dataset representing the detected gamma radiation and its two-dimensional distribution. The dataset may be considered as a planar projection image.

Tomographic reconstruction techniques enable the generation of three-dimensional images of a subject from a set of planar projection images of the subject. Planar projection images are acquired from several angular positions around the subject by placing the subject near a gantry to which one or more detectors are attached and rotating the gantry to move the detectors to each desired angular position. The tomographic reconstruction unit reconstructs a three-dimensional image based on the projection image.

Conventional SPECT detectors (e.g., using NaI scintillators and multi-channel collimators) provide an axial field of view (FOV) of 40 cm. However, dosimetry, treatment planning, and monitoring typically require images with much longer axial FOV (e.g., 75cm, 125 cm). Currently, such images are obtained by acquiring projection images of various projection angles within one axial FOV and then acquiring projection images of various projection angles within an adjacent axial FOV. Three-dimensional images are reconstructed from the projection images for each axial FOV range, and the three-dimensional images are stitched together to generate a three-dimensional image exhibiting a long axial FOV. In a typical clinical setting, such collection may be over 30 minutes. In the case where three axial FOV ranges are required, the acquisition time may be increased by an additional 50%.

In theory, large axial FOV images can be acquired quickly using a detector with a large axial FOV. However, such detectors present cost and engineering issues. Larger detectors require larger scintillators, which require a significant amount of retooling and design effort. Larger detectors also require increased shielding from stray gamma radiation. In addition, the increased detector weight caused by the increased detector size can overwhelm current gantry systems and cause detector deflection (sagging) that can compromise image accuracy.

A SPECT imaging system that effectively provides acquisition of high quality long axis FOV images in a suitable time frame is desired.

Drawings

FIG. 1A is a side view of a single-head imaging system according to some embodiments;

FIG. 1B is a perspective view of a single-head imaging system according to some embodiments;

FIG. 2A is a side view of a dual head imaging system according to some embodiments;

FIG. 2B is a perspective view of a dual head imaging system according to some embodiments;

FIG. 3 is a side cross-sectional view of a detector according to some embodiments;

FIG. 4 is a side cross-sectional view of a detector according to some embodiments;

FIG. 5 is a side cross-sectional view of a detector according to some embodiments;

FIG. 6 is a side cross-sectional view of a detector including two different collimators, according to some embodiments;

FIG. 7 is a side cross-sectional view of a detector including two different collimators, according to some embodiments;

FIG. 8 is a side cross-sectional view of a detector including two different collimators, according to some embodiments;

FIG. 9 is a side cross-sectional view of a detector including two different collimators, according to some embodiments;

FIG. 10A is a perspective view of a dual head imaging system according to some embodiments;

FIG. 10B is a side view of a dual head imaging system according to some embodiments; and

Figure 11 illustrates components of a SPECT/CT imaging system in accordance with some embodiments.

Detailed Description

The following description is provided to enable any person skilled in the art to make and use the described embodiments and sets forth the various modes contemplated for carrying out the described embodiments. However, various modifications will remain apparent to those skilled in the art. Independent of the use of grammatical terminology, individuals having male, female, or other gender identities are included in the term.

Some embodiments facilitate rapid acquisition of long axial FOV images using an axially extended SPECT detector. Such a SPECT detector may be supported by a first support at a first axial end and a second support at a second axial end. The second scaffold may define an aperture in which the subject resides during imaging. Providing a support at either axial end of the SPECT detector allows the use of a heavy SPECT detector without introducing significant sagging or other geometric anomalies. The shielding may contribute to the weight of the SPECT detector, and the need for shielding depends on detector characteristics such as energy resolution and the ability to determine the depth of interaction (DOI) for each detection event. Typically, naI scintillator-based detectors require shielding, but CZT-based detectors may not. Some embodiments also provide a non-enclosed volume between the two stents in which the subject resides, thereby facilitating access to the subject prior to and during imaging.

The SPECT detector may be coupled to each of the supports in a manner that allows the SPECT detector to rotate about the aperture, and thereby acquire planar projection images of the subject from multiple projection angles. Embodiments may include a second SPECT detector also supported by the first support at a first axial end and by the second support at a second axial end. The use of a second (or third or fourth) SPECT detector allows projection images to be acquired simultaneously from multiple projection angles.

According to some embodiments, the SPECT detector includes two or more substantially independent SPECT detectors. Each substantially independent SPECT detector includes a respective portion of converter material (directly or indirectly) and a respective anode array (e.g., a matrix of photomultiplier tubes (PMTs)). In one particular example, according to some embodiments, three SPECT detectors each having an axial dimension of 40cm and a lateral dimension of 50cm may be combined into a SPECT detector having an axial dimension of 120cm and a lateral dimension of 50 cm. By providing such an axial field of view, embodiments may acquire desired images (e.g., diagnostic images) of a majority of male and female populations in a single acquisition (i.e., without requiring movement of the patient relative to the detector and "stitching" of continuously generated three-dimensional images). Embodiments are not limited to an axial dimension of 120cm, and are contemplated to span axial dimensions of up to 2m and greater.

In some embodiments, two or more substantially independent SPECT detectors are coupled to different types of collimators. In the case of two substantially independent SPECT detectors, the collimator may include a parallel-hole collimator and a bevel-hole collimator, a bevel-hole collimator and a needle-hole collimator, or any other combination of two different types of collimators.

Fig. 1A and 1B are views of a SPECT imaging system 100 according to some embodiments. Each component of system 100 and each other component described herein may be implemented using any combination of hardware and/or software. Some components may share hardware and/or software of one or more other components. Each component may also be constructed using any combination of suitable materials.

The system 100 includes a SPECT imaging system 110 and a table 160. Imaging system 110 includes a detector housing 120 coupled to a first support 130 by a coupling 135 and to a second support 140 by a coupling 145. The first bracket 130 and the second bracket 140 are substantially vertical and, in the illustrated embodiment, are rigidly coupled to each other by the lower housing 150. The second bracket 140 defines an aperture 170 through which a subject may pass to access an imaging volume 180. Advantageously, the operator can access the subject through the aperture 180 prior to and during imaging without disturbing the subject's position.

The detector housing 120 includes a SPECT detector and one or more collimators, as will be described below. Couplings 135 and 145 are coupled to opposite axial ends of detector housing 120 and include drive elements to move housing 120 (and thus the SPECT detector disposed therein) in the directions indicated by arrow 125 (i.e., toward and away from the central axial axis of volume 180). The couplings 135 and 145 are also coupled to elements of the respective brackets 130 and 145, and the brackets 130 and 145 move the couplings 135 and 145 in the direction of arrow 190 to rotate the housing 120 about the volume 180. As is known in the art, this movement allows planar projection images of a subject disposed in the volume 180 to be acquired from different projection angles.

The table 160 supports the imaging subject and may be movable to place the subject in a desired position relative to the detector within the housing 120. The desired location may be a location intended to best capture emission data emitted by a radioisotope located within a particular portion of the subject. The table 160 may include any features and mechanisms necessary to facilitate selective positioning of an imaging subject disposed on the table 160 relative to a detector within the housing 120.

Fig. 2A and 2B illustrate a dual head imaging system according to some embodiments. The components of system 200 may be implemented as described above with respect to similarly numbered components of system 200, although embodiments are not limited in this regard.

In addition to the detector housing 220, the imaging system 210 includes a detector housing 222 that includes a SPECT detector and is also coupled to a first support 230 and a second support 240. The detector housing 222 is positioned substantially opposite the housing 220 across the aperture 280.

Couplings 237 and 247 are coupled to opposite axial ends of the detector housing 222 and include drive elements to move the housing 222 and its SPECT detector toward and away from the central axial axis of the volume 280. The couplings 237 and 247 are also coupled to elements of the respective brackets 130 and 140 to move the couplings 237 and 247 in the direction of arrow 290 to simultaneously rotate the housings 220 and 222 about the volume 280. This movement allows for the simultaneous acquisition of planar projection images of a subject disposed in the volume 280 from two opposing and selectable projection angles.

Fig. 3 is a schematic depiction of the components of a SPECT detector 310 according to some embodiments. For purposes of this description, a "detector" will refer to a system that includes one or more cathodes, a portion of the converter material, and a set of sensors. In the case of an indirect converter material such as a scintillator, the sensor is a PMT. On the other hand, direct converter based detectors use an array of conductive anodes as their sensors. The detector 310 is a direct converter-based detector, but the embodiment is not limited thereto.

The cathode 312 of the detector 310 may include a continuous layer that is generally transparent to gamma rays having energy to be detected by the detector 310. The converter 314 may include a single crystal semiconductor material, such as CZT or cadmium telluride (CdTe), that converts gamma rays into photons. The transducer 314 may be fabricated by longitudinally cutting a forged NaI (for example) ingot.

The sensor 316 may include a grid of hexagonal or other shaped conductive anodes. Each of the sensors 316 is coupled to a dedicated signal line and is not in direct electrical contact with its adjacent proximity sensor.

Collimator 320 is coupled to detector 310. Collimator 320 is depicted as a parallel hole collimator, but may include a multi-focal cone beam collimator or any other collimator type known or to become known. In general, the collimator 320 defines the response line of incident gamma rays and filters out scattered or stray gamma radiation. The detector 310 and collimator 320 may be disposed in a housing 330, which housing 330 is in turn coupled to the first and second supports as described above.

In one example of operation, the detector 310 is positioned to detect gamma rays emitted from the volume. Some gamma rays are collimated by the collimator 320, and the collimated gamma rays pass through the cathode 312 due to the transparency of the cathode 312 to the gamma rays. Gamma rays passing through the cathode 312 and penetrating the direct conversion material 314 interact with the direct conversion material 314 to generate electron-hole pairs. The cathode 312 is held at a negative bias potential while the sensor 316 is held at a small repulsive potential. Thus, positively charged holes drift toward cathode 312, while negatively charged electrons drift toward sensor 316. When an electron approaches a given sensor 316, a signal is induced on the given sensor and its neighboring sensors.

After the given sensor collects electrons, the readout electronics 340 may use the signals received from the adjacent sensors to determine the sub-pixel location of the given sensor where it will be assumed that gamma rays have been received. The sub-pixel locations that receive all gamma rays within a given time period may then be used to generate a projection image. As is known in the art, a three-dimensional image of a subject may be reconstructed from a plurality of such projection images acquired at different projection angles

In the case of an indirect-converter-based detector, the collimated gamma rays pass directly to and interact with an indirect converter (e.g., a NaI scintillator) to generate photons. Photons may pass through the light guide before being received by the PMT matrix. PMTs generate an electrical signal based on the received photons, which is used by readout electronics as described above.

Fig. 4 illustrates a detector consisting of two separate detectors according to some embodiments. Detectors 410 and 415 are coupled to collimators 420 and 425, respectively, and all of these components are disposed in housing 430. As described above, the axial ends of the housing 430 may be coupled to the first and second brackets.

Detectors 410 and 415 may be identical, but embodiments are not limited thereto. The detector 410 includes a cathode 411, a transducer 412 including a portion of the transducer material, and a sensor 413. Similarly, detector 415 includes cathode 416, transducer 417 including a portion of transducer material, and sensor 418. Collimators 420 and 425 are depicted as parallel hole collimators, but the embodiments are not limited thereto. Any mechanical "gap" between detectors 410 and 415 may be addressed using software-based and/or collimation-based solutions.

Readout electronics 440 receives signals from sensor 413 of detector 410 and readout electronics 445 receives signals from sensor 418 of detector 415. Detectors 410 and 415 may operate substantially independently to acquire corresponding axially adjacent planar projection images. In one particular example, detectors 410 and 415 have an axial dimension of between 30-50cm, and thus the detector of fig. 4 exhibits an axial dimension of 60-100 cm. In some embodiments, each of the sensors 413 and 418 may include a separate assembly of 59 PMTs.

Fig. 5 illustrates a detector consisting of two separate detectors according to some embodiments. Disposed in housing 530 are detectors 510 and 515 coupled to collimators 520 and 525, respectively. Also, the axial ends of the housing 530 may be coupled to the first and second brackets.

The detector of fig. 5 may be identical to the detector of fig. 4, except that readout electronics 540 receives signals from sensor 513 and from sensor 518. Thus, readout electronics 540 may generate a planar projection with a longer axial FOV than detectors 510 and 515 alone. Cathode 511 may be electrically coupled to cathode 516 to normalize signals received from sensor 513 and from sensor 518 to one another. In some embodiments, cathodes 511, 516 and transducers 512, 517 are part of respective detectors, and sensors 513, 518 are a single continuous matrix of sensors placed thereon.

Each of fig. 6-8 illustrates the use of two different collimator types in connection with the detector of fig. 5. Any detector according to some embodiments may be coupled to any combination of two or more types of collimators. The use of different collimator types provides flexibility in acquiring images over a large axial FOV.

Fig. 6 shows collimator 620 and collimator 625 coupled to detector 610 and detector 615, respectively. Collimator 620 and collimator 625 are inclined hole collimators with holes oriented in opposite directions. Collimator 620 and collimator 625 may cooperatively function as a single converging collimator for the detector of fig. 6.

Similarly, fig. 7 shows a pair of bevel-hole collimators 720 and 725 coupled to detector 710 and detector 715, respectively. The holes of collimators 720 and 725 are oriented in opposite directions. However, the corresponding orientation of the holes, as opposed to fig. 6, provides divergent collimation for the detector of fig. 7.

The detector of fig. 8 is coupled to a needle hole collimator 820 and a parallel hole collimator of fig. 6. Thus, anode 813 of detector 810 collects electrical signals corresponding to the hole collimated gamma radiation and anode 818 of detector 815 collects electrical signals corresponding to the parallel hole collimated gamma radiation. Thus, projection images based on these electrical systems will exhibit needle hole collimation characteristics over the axial FOV of the detector 810 and parallel hole collimation characteristics over the axial FOV of the detector 815.

Fig. 9 is a schematic view of a detector according to some embodiments. The detector of fig. 9 consists of three detectors 922, 924 and 926. For example, each of detectors 922, 924, and 926 may have an axial dimension of 40cm and a lateral dimension of 50cm, such that the detector of fig. 9 effectively has an axial dimension of 120cm and a lateral dimension of 50 cm.

Detectors 922, 924, and 926 are coupled to collimators 932, 934, and 936, respectively. As described above, collimators 932, 934, and 936 may comprise any combination of any suitable collimator types. Housing 910 houses detectors 922, 924, and 926, and collimators 932, 934, and 936. The axial ends of the housing 910 may be coupled to first and second brackets to provide support for the detector of fig. 9 and translational and rotational movement as described above.

Fig. 10A and 10B illustrate a dual-head SPECT/CT system 1000 according to some embodiments. The system 1000 may be implemented as described above with respect to the system 200, except that the CT housing 1030 is substituted for the first cradle 230 of the system 200. As is known in the art, the CT housing 1030 includes CT imaging elements (i.e., one or more X-ray tubes and one or more X-ray detectors) and defines an aperture 1090 in which a subject is placed for imaging using the CT imaging elements.

More specifically, table 1060 can be operated to move a subject into aperture 1090 to acquire CT images using CT imaging elements, and then move the subject into volume 1080 to acquire planar SPECT images using detectors 1020 and 1022. Subsequent acquisitions may include movement of detectors 1020 and 1022, as indicated by arrows 1025 and/or 1035.

The CT image may be used to segment structures within the subject and determine an attenuation map of the subject. The segmentation and attenuation map may then be used during reconstruction of the three-dimensional image based on the acquired planar SPECT image. Registration of the segmentation and attenuation map with the SPECT image is simplified because the subject's position on the table 1060 may not change significantly between CT and SPECT acquisitions.

Fig. 11 is a block diagram of components 1100 of a SPECT/CT imaging system according to some embodiments. The terminal 1110 can include a display device and an input device coupled to the control system 1120. The operator can operate the terminal 1110 to instruct the control system 1120 via the terminal interface 1124 to cause the SPECT/CT imaging system to acquire a desired image of the subject. The terminal 1110 can receive and display acquired images and images reconstructed by the control system 1120. In some embodiments, the terminal 1110 is a computing device separate from the control system 1120, such as, but not limited to, a desktop computer, a laptop computer, a tablet computer, and a smartphone.

Control system 1120 may include any general purpose or special purpose computing system. The control system 1120 includes one or more processing units 1121 and a storage device 1130 for storing program code, the one or more processing units 1121 configured to execute executable program code to cause the system 1120 to operate as described herein. The storage device 1130 may include one or more fixed disks, solid state random access memory, and/or removable media (e.g., thumb drive) mounted in a corresponding interface (e.g., USB port).

The memory device 1130 stores program codes for the control program 1131. The one or more processing units 1121 can execute a control program 1131 to control the motors, servo systems, and encoders in conjunction with the SPECT system interface 1122 to rotate the SPECT detector about the subject and acquire two-dimensional projection images (i.e., SPECT data 1132) at defined projection angles during rotation. Prior to acquisition, the table may be controlled using a table interface 1125 to position the subject and an injection interface 1126 to control an injector to inject the radionuclide into the subject. Similarly, a control program 1131 can be executed to control CT imaging elements using the CT system interface 1123 to acquire CT data 1133. The control procedure 1131 can also be executed to reconstruct an image 1134 based on SPECT data 1132 and CT data 1133.

Those skilled in the art will appreciate that various adaptations and modifications of the just-described embodiments may be configured without departing from the claims. It is, therefore, to be understood that the claims may be practiced otherwise than as specifically described herein.

Claims (20)

1. A system, comprising:

a housing having a first end and a second end;

A SPECT detector disposed in the housing;

A first bracket;

A first coupling coupled to the first end of the housing and the first bracket;

a second bracket defining a hole; and

A second coupling coupled to the second end of the housing and the second bracket, wherein the housing is disposed between the first bracket and the second bracket.

2. The system of claim 1, further comprising:

A first drive element for moving the first and second couplings to cause the SPECT detector to move about the aperture, the first and second couplings including a second drive element for moving the SPECT detector toward and away from a center of the aperture.

3. The system of claim 1, wherein the SPECT detector has an axial field of view between 80cm and 120cm, including 80cm and 120cm.

4. The system of claim 1, the SPECT detector comprising:

a first SPECT detector including a first portion of converter material; and

A second SPECT detector includes a second partial converter material separate from the first partial converter material.

5. The system of claim 4:

the first SPECT detector includes a first cathode and a first sensor array; and

The second SPECT detector includes a second cathode and a second sensor array.

6. The system of claim 4, further comprising:

a first collimator of a first collimator type, operably coupled to the first SPECT detector; and

A second collimator of a second collimator type is operatively coupled to the second SPECT detector.

7. The system of claim 1, the SPECT detector comprising:

Only one continuous converter material portion;

A first sensor array coupled to the one continuous converter material portion; and

A second sensor array coupled to the one continuous converter material portion.

8. A method, comprising:

mounting the SPECT detector into a housing having a first end and a second end;

coupling a first coupling member to the first end of the housing and a first substantially vertical bracket; and

A second coupling member is coupled to the second end of the housing and a substantially vertical second bracket defining an aperture such that the housing is disposed between the first bracket and the second bracket.

9. The method of claim 8, further comprising:

moving the first coupling and the second coupling to cause the SPECT detector to move about the aperture; and

The first and second couplings are operated to move the SPECT detector toward and away from the center of the aperture.

10. The method of claim 8, wherein the SPECT detector has an axial field of view between 80cm and 120cm, including 80cm and 120cm.

11. The method of claim 10, wherein mounting the SPECT detector into the housing comprises:

mounting a first SPECT detector including a first portion of converter material into the housing; and

A second SPECT detector including a second portion of converter material separate from the first portion of direct converter material is mounted into the housing.

12. The method of claim 11, wherein the first SPECT detector includes a first cathode and a first sensor array and the second SPECT detector includes a second cathode and a second sensor array.

13. The method of claim 11, further comprising:

coupling a first collimator of a first collimator type to the first SPECT detector; and

A second collimator of a second collimator type, operatively coupled, is coupled to the second SPECT detector.

14. The method of claim 8, the SPECT detector comprising:

Only one continuous converter material portion;

A first sensor array coupled to the one continuous converter material portion; and

A second sensor array coupled to the one continuous converter material portion.

15. A system, comprising:

A SPECT detector having an axial dimension and a lateral dimension;

a first substantially vertical support coupled to a first axial end of the SPECT detector; and

A second substantially vertical support defines an aperture and is coupled to a second axial end of the SPECT detector.

16. The system of claim 15, wherein the SPECT detector has an axial field of view between 80cm and 120cm, including 80cm and 120cm.

17. The system of claim 15, the SPECT detector comprising:

a first SPECT detector including a first portion of converter material; and

A second SPECT detector includes a second portion of the converter material separate from the first portion of the direct converter material.

18. The system of claim 17:

the first SPECT detector includes a first cathode and a first sensor array; and

The second SPECT detector includes a second cathode and a second sensor array.

19. The system of claim 17, further comprising:

a first collimator of a first collimator type, operably coupled to the first SPECT detector; and

A second collimator of a second collimator type is operatively coupled to the second SPECT detector.

20. The system of claim 15, the SPECT detector comprising:

Only one continuous converter material portion;

A first sensor array coupled to the one continuous converter material portion; and

A second sensor array coupled to the one continuous converter material portion.