JP4424911B2 - Apparatus and method for single photon emission computed tomography - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to single photon emission computed tomography (SPECT).
[0002]
[Prior art]
While therapies for various tissue regeneration including gene therapy have been proposed, establishment of a method to evaluate the physiological functions of tissues and cells in a three-dimensional and quantitative manner in a state where an individual animal is utilized. It is desired. In Europe and the United States, positron emission tomography (PET) devices dedicated to small animals have been developed and applied research in the fields of genome drug discovery and protein science.
[0003]
On the other hand, an apparatus called a single photon emission computed tomography apparatus (SPECT apparatus) is known as one used for this. In this method, a drug labeled with a radioisotope is administered to a subject, and the distribution in the body is imaged. The radiopharmaceutical used in the SPECT apparatus has a long life and can be obtained from other facilities. Also, higher resolution than PET can be obtained by devising the collimator used. Sensitivity is inferior to PET (about one-hundredth), but many tests such as blood flow imaging are possible, and it is possible to evaluate the function of small animals, as nuclear medicine clinical diagnosis is actually widely practiced. Its application range is considered wide.
[0004]
In a SPECT device, a collimator is mounted on the surface of a single position detection type radiation detector, rotated along the outside of the subject, collected radiation data over the entire circumference, and analyzed for signals synchronized with the rotation. Estimate the distribution of the radiopharmaceutical inside the subject. As a collimator, a honeycomb parallel beam collimator and a fan beam collimator having a single linear focus are generally used for clinical devices.
[0005]
On the other hand, a SPECT apparatus equipped with a collimator having a single hole, that is, a pinhole collimator, has been developed, and many prototypes have been manufactured. In such a pinhole SPECT apparatus (micro SPECT apparatus), a position detection type radiation detector provided with a pinhole collimator is provided near a subject on a pedestal (bed). It is rotated. The radiation from the subject passes through the hole and becomes a cone beam shape and is detected by the radiation detector. By using a pinhole collimator, the hole diameter can be reduced and imaging can be performed close to the subject, so that the spatial resolution can be improved. Further, the pinhole SPECT apparatus has an advantage that its design structure is simple. Actually, a prototype having a resolution of about 1 mm has been manufactured, and there has been a track record of tomographic imaging of small animals such as rats and mice. In cone beam computed tomography, the Feldkamp method (J. Opt, Soc. Am., A1, 612-619 (1984)), which is an extension of the filter back projection method, is used for image reconstruction.
[0006]
The paper by Iida et al. (J. Nucl. Cardiol. 5: 313-31 (1998)) shows that the local tissue blood flow of the myocardium can be measured with a SPECT apparatus, which was conventionally possible only with PET. It is outlined. A paper by Meikle et al. (Curr. Pharm. Des. 7, 1939-1960 (2001)) reviewed currently developed PET devices for animals and SPECT devices, and summarized their roles in preclinical trials. ing.
[0007]
[Non-Patent Document 1]
LA Feldkamp, LC Davis and JW Kress, Practical cone-beam algorithm, J. Opt, Soc. Am., A1, 612-619 (1984)
[Non-Patent Document 2]
H. Iida and S. Eberl, Quantitative assessment of regional myocardial blood flow with thallium-201 and SPECT, J. Nucl. Cardiol. 5, 313-31 (1998)
[Non-Patent Document 3]
S. Meikle, S. Eberl and H. Iida, Instrumentation and Methodology for Quantitative Pre-Clinical Imaging Studies, Curr. Pharm. Des. 7, 1939-1960 (2001)
[Non-Patent Document 4]
HK Tuy, An inversion formula for cone-beam reconstruction, SIAM J. APPL. MATH. 1983, vol. 43, No. 3, 546-552
[Non-Patent Document 5]
Hiroyuki Kudo, Optics, 29, 354 (2000) (Fig. 1 (f))
[0008]
[Problems to be solved by the invention]
High-resolution SPECT imaging can be realized by combining a pinhole collimator and a position detection type gamma camera, and several papers have already been reported. In Japan, several medical device manufacturers have designed and manufactured collimators dedicated to clinical devices to realize small animal imaging. However, these reports are limited to the performance evaluation of prototypes at the laboratory level, and have not been applied to pathophysiology or medical research.
[0009]
One reason that SPECT imaging applied research has not been developed so far is the problem that the obtained image has poor quantitative reliability, and the image is distorted particularly in the peripheral region of the visual field. Conventionally, a method in which the filter back projection method is extended for image reconstruction (Feldkamp method, 1984) has been used. Complete image reconstruction in a parallel beam collimator satisfies the geometric condition called Orlov's condition, that is, an arbitrary great circle (unit circle centered at the origin) is used for reconstruction. It is necessary to intersect the direction vector (trajectory). For complete image reconstruction in a pinhole collimator, Tuy's condition (HK Tuy. An inversion formula for cone-beam reconstruction. SIAM J. APPL. MATH. 1983, vol. 43, No. 3, 546-552 ) Is presented. However, in the geometric design of the conventional pinhole SPECT apparatus, this precondition is not satisfied in a cross section other than the rotating surface, so that the image on the rotating surface including the hole can be accurately reconstructed in principle. There is a drawback that accurate radioactivity concentration cannot be measured on a fault plane that does not contain. In addition, there is a drawback that the image on the rotating surface including the hole is distorted by non-uniform resolution. Therefore, there is a limit to quantitativeness in image reconstruction due to incomplete data. This is partly due to the limitations of mathematical theory for reconstructing images, but more essentially, in the acquisition of cone-beam imaging data, mathematically ideal acquisition data cannot be captured. Because. Therefore, it is desired to develop a pinhole SPECT apparatus that can provide uniform and quantitative imaging data.
[0010]
A similar problem is the use of a cone beam in X-ray CT. When a cone beam is used in X-ray CT, projection data is measured by irradiating a subject with a conical X-ray beam from an X-ray source. Therefore, data is collected in the shape of a cone beam, similar to a SPECT apparatus using a pinhole collimator. Here, Kudo (Optics, Vol. 29, page 354 (2000)) collects measurement data capable of exact image reconstruction in X-ray CT, that is, all planes intersecting the subject are X-ray sources. In order to satisfy the condition of intersecting with the trajectory, two orthogonal circular trajectories, circular and straight trajectories, or a spiral trajectory have been proposed as easy-to-implement X-ray source trajectories.
[0011]
An object of the present invention is to enable uniform and quantitative imaging data to be collected in pinhole SPECT.
[0012]
[Means for Solving the Problems]
A first single photon emission computed tomography apparatus according to the present invention includes a pedestal capable of supporting a subject, one or more detector blocks combining a pinhole collimator and a position detection type radiation detector, and the detection described above. The detector block is mounted on a rotation surface including the center of the field of view while fixing the center of the field of view of the radiation detector at one point, and a rotation mechanism for rotating the detector block around the pedestal and the rotation of the rotation mechanism are controlled. Receives and stores radiation measurement data detected by the detector from the control block, a swing mechanism that periodically swings the pedestal relative to the rotation axis while synchronizing with the rotation of the rotation mechanism, and the detector block. And a storage device.
[0014]
A second single photon emission computed tomography apparatus according to the present invention includes a pedestal capable of supporting a subject, a plurality of detector blocks combining a pinhole collimator and a position detection type radiation detector, and the detector block described above. , While fixing the center of the field of view of the radiation detector to one point, it is also mounted on the rotation surface including the center of the field of view and outside the rotation surface, and a rotation mechanism for rotating the detector block around the pedestal, and rotation of the rotation mechanism And a storage device that receives and stores radiation measurement data detected by the detector from the detector block. The third single photon emission computed tomography apparatus according to the present invention further includes a moving mechanism for moving the pedestal in a direction parallel to the rotation axis while synchronizing with the rotation of the rotation mechanism.
[0015]
A fourth single-photon emission computed tomography apparatus according to the present invention includes a pedestal capable of supporting a subject, a plurality of detector blocks combining a pinhole collimator and a position detection type radiation detector, and the plurality of detections. The detector block is mounted by shifting the center of the field of view of the radiation detector, the rotating mechanism for rotating the detector block around the pedestal, the control device for controlling the rotation of the rotating mechanism, and the detector block. And a storage device that receives and stores the radiation measurement data detected by.
[0016]
A fifth single photon emission computed tomography apparatus according to the present invention includes a pedestal capable of supporting a subject, a plurality of detector blocks in which a pinhole collimator and a position detection type radiation detector are combined, and radiation of the pedestal. A rotation mechanism that rotates at the center of the field of view of the detector, a mechanism that tilts the support pedestal from the rotation axis at the center of the field of view of the radiation detector, a control device that controls the rotation of the rotation mechanism, and the detector block And a storage device for receiving and storing radiation measurement data detected by the detector.
[0017]
Further, in the first single photon emission computed tomography method according to the present invention, a plurality of detector blocks each including a position detection type radiation detector equipped with a pinhole collimator are used. As shown in FIG. 4, the radiation sensor is arranged at an arbitrary position around the pedestal capable of supporting the subject so as to detect the radiation not only on one rotating surface but also outside the rotating surface . Then, the detector block is moved around the pedestal so that the detector always includes the subject in the visual field, and the radiation measurement data is collected by the detector block and recorded in the storage device.
[0018]
In the second single-photon emission computed tomography method according to the present invention, one or more detector blocks each including a position detection type radiation detector equipped with a pinhole collimator are used, and the radiation detector always detects a subject. Fix to include in the field of view. Then, the pedestal is tilted and rotated, and radiation measurement data is collected by the detector block and recorded in the storage device.
The first and second methods include imaging by the first to fifth single photon emission computed tomography apparatuses described above.
[0019]
【The invention's effect】
In the present invention, in the pinhole SPECT, the detector arrangement is designed to look at the subject from different directions as well as on the rotation surface, or the pedestal supporting the subject is swung with respect to the detector. Collect uniform and quantitative imaging data.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference symbols denote the same or equivalent.
In the pinhole SPECT apparatus, one or more position detection type radiation detectors are arranged around a pedestal capable of supporting a subject (subject), and the detector is generated inside the subject and passes through a hole of the pinhole collimator. Detecting radiation distributed in a cone. The detector is always installed so as to include the subject in the field of view, and is moved around the pedestal. In the conventional pinhole SPECT apparatus, the detector is installed only on one rotation surface. However, in the present invention, the detector is not only on one rotation surface including the center of the field of view, but also on the rotation surface. It is arranged to detect radiation even outside. The detection method of the present invention can be realized with various structures. As will be described in detail later, an arrangement of detectors, a deviation of the pinhole position, a swing of the pedestal position, and the like can be employed. Thus, by detecting the radioactivity by shifting from the plane of rotation, the integrity of the data can be guaranteed, and the imaging data mathematically satisfies the structural requirements for image reconstruction. Thereby, the resolution of the reconstructed image obtained from the imaging data is improved, and the distribution of the radioactivity concentration in the subject can be accurately measured.
[0021]
1 to 4 show a pinhole SPECT apparatus according to a first embodiment. In this pinhole SPECT apparatus, the subject is supported on a pedestal (bed) 10. A detection block in which the pinhole collimator 12 is mounted on a position detection type radiation detector (NaI or the like) 14 is arranged around the base 10. Specifically, a plurality of detection blocks are attached to the gantry 16. A rotation drive device 18 provided adjacent to the gantry 16 incorporates a stepping motor (not shown) and rotationally drives the gantry 16. By adjusting the mounting position on the gantry 16, the detector rotation diameter is changed depending on the size of the subject. The pedestal 10 is fixed by a support portion 20 installed on the opposite side of the pedestal 10 from the rotation drive device 18. The gantry 16, the rotational drive device 18, and the support portion 20 are fixed to the base portion 22 of the device. When the gantry 16 is rotated during data collection, the detector 14 detects radiation around the base 10 along with the rotation. The number of detectors 14 is preferably as many as possible, but as shown in FIG. 2, this apparatus has six. 1 shows the AA cross section of FIG. 2, and the detector is located in the plane of rotation. The rotation plane is a plane that is perpendicular to the rotation axis of the gantry 16 and includes the center of the visual field. 3 and 4 show the BB cross section and the CC cross section of FIG. 2, and show the detector 14 positioned on a plane inclined by 15 ° and 30 ° from the rotation plane, respectively.
[0022]
The arrangement of the detection block will be described. The visual field centers of the pinhole collimators 10 of the plurality of detectors are matched. That is, the center of the field of view expected by the detector 14 is always fixed at one point. The center of rotation of the base 10 also coincides with this point. Some of the plurality of detectors 14 are not in the plane of rotation, is installed outside the rotating surface.
[0023]
FIG. 5 shows the overall configuration of the pinhole SPECT apparatus. A computer 40 that controls the apparatus includes an imaging control program 42 for collecting data and an image reconstruction program 44 that reconstructs an image based on the imaging data. The imaging control program 42 sets parameters in the sequencer 46 at the start of imaging data collection, and then instructs the start of data collection. Correspondingly, the sequencer 46 controls the operation of the drive system 48 such as the rotary drive device 18 and the radiation detector 14 and the data collection circuit 50 according to the sequence control program, and collects projection data for each angle. To do. The rotation drive device 18 rotates the gantry 16 according to the instruction. The position and energy data detected by the detector 14 passes through the data processing circuit 50 and is sequentially transferred and stored in the memory 52 at every angle end. The image reconstruction program 44 performs image reconstruction using the imaging data fetched into the memory 52.
[0024]
Note that in an existing program for image reconstruction from a captured image, an image is reconstructed based on an image passing through the center of rotation. Matching the field centers is to use this image reconstruction program, not necessarily. Generally, it is sufficient that one or more detectors are installed so as to include the subject in the field of view and the position with respect to the subject is known.
[0025]
Next, a modification of the pinhole SPECT apparatus according to the first embodiment will be described. In this modification, a moving mechanism (not shown) that moves the base 10 in a direction parallel to the rotation axis while synchronizing with the rotation of the gantry 16 is provided. As the moving mechanism, a conventional CT apparatus used for moving the pedestal may be used. Since this apparatus is otherwise the same as the SPECT apparatus of the first embodiment, a description thereof will be omitted.
[0026]
Next, a pinhole SPECT apparatus according to a second embodiment will be described. In this pinhole SPECT apparatus, the respective visual field centers of the plurality of detectors are made to coincide with each other, but the positions of the holes include those out of the rotation plane including the visual field center.
[0027]
In the example shown in FIG. 6, the pinhole SPECT apparatus includes a ring-shaped radiation detector 14 ′ and a ring-shaped collimator 12 ′. The detector 14 ′ is installed in the gantry 16. In other respects, it is the same as the pinhole SPECT apparatus of the first embodiment. Two holes 13 are provided in the collimator 12 ′. One hole 13 (upper hole in FIG. 6) is in the rotation plane including the center of the visual field, while the other hole 13 (upper hole in FIG. 7) is outside the rotation plane.
[0028]
In the example shown in FIG. 7, the pinhole SPECT apparatus includes two flat radiation detectors 14 ″ and corresponding collimators 12 ″. The detector 14 "is attached to the gantry 16 up and down with respect to the pedestal. In other respects, the detector 14" is the same as the pinhole SPECT apparatus of the first embodiment.
[0029]
Next, a pinhole SPECT apparatus according to the third embodiment will be described. This pinhole SPECT apparatus uses a swing mechanism 22 that swings the pedestal 10 left and right (or up and down, etc.) around its rotation center while synchronizing with the rotation of the detector 14. In the apparatus shown in FIG. 8, it is shaken in a horizontal plane passing through the pedestal (as indicated by a broken line in the vertical direction in FIG. 8). In the example shown in FIG. 9, the swing mechanism 22 includes a disc 22 a having a center corresponding to the swing center of the pedestal 10, and a drive motor 22 b that swings the disc at a predetermined cycle. The support part 20 that supports the is fixed to the disc 22a. A plurality of (for example, six) detectors 14 each equipped with a pinhole collimator 12 are arranged in the rotation plane. The swing center of the pedestal 10 is in the plane of rotation of the detector 14 and coincides with the center of the visual field of each pinhole collimator 12. The rotation of the detector 14 and the swing of the base 10 are synchronized. This pinhole SPECT apparatus is otherwise the same as the pinhole SPECT apparatus of the first embodiment. Imaging data is collected while swinging the pedestal 10 in synchronization with the rotation of the detector 14 so as to anticipate one point of the rotation axis.
[0030]
The radioactivity concentration distribution inside the subject can be accurately measured by any of the imaging devices described above. Therefore, for example, since the distribution of the radiopharmaceutical in the body can be measured quantitatively, an imaging system that can evaluate the physiological function of the local tissue of the subject as a numerical value can be constructed. This makes it possible to accurately estimate physiological functions (such as blood flow) in the body based on accurate measurement of the pharmacokinetics of the radiopharmaceutical. Furthermore, by analyzing the pharmacokinetics based on a mathematical model, it is possible to image physiological functions such as blood flow.
[0031]
Next, a pinhole SPECT apparatus according to the fourth embodiment will be described. In this SPECT apparatus, the detector block is fixed so that the detector 14 always includes the subject in the field of view, and the pedestal 10 that supports the subject is disposed in the field of view of the detector. The pedestal 10 is tilted and rotated . In this state, radiation measurement data is collected by the detector block and recorded in the storage device. As shown in FIG. 10, this SPECT apparatus is provided with a mechanism 24 for tilting the pedestal 10 that supports the subject, and the pinhole collimator 12 is mounted so that the tilted pedestal 10 is in the field of view of the detector 14. A detector block including a position detection type radiation detector is fixed. Furthermore, a rotation mechanism 26 that rotates the pedestal 10 at the center of the field of view of the detector 14 is provided as indicated by an arrow in FIG. Since this apparatus is otherwise the same as the SPECT apparatus of the first embodiment, a description thereof will be omitted. However, the gantry rotational drive device 18 is not used. The tilted pedestal 10 is rotated by the rotation mechanism 26 and the radiation measurement data is collected by the detector 14.
[0032]
FIG. 11 shows an example of measurement data obtained by a pinhole SPECT apparatus. The mice were administered Tl-201 labeled thallium chloride (a radiopharmaceutical), placed on the pedestal of the SPECT device, tomographically imaged, and the time curve of the radiation concentration in the myocardium was measured. The graph of FIG. 11 shows the radiation count value obtained by SPECT and the count value of arterial blood.
[0033]
The development of a SPECT device dedicated to animals can provide pioneering therapies such as gene therapy and tools that provide objective evaluation guidelines in drug discovery research, and can be expected to create new markets in this field. Many treatments have been developed recently, but the development of a method that can monitor the improvement of the physiological function in the state where the treated animals are utilized is expected, and many contributions can be expected.
[Brief description of the drawings]
FIG. 1 is a view showing the vicinity of a pedestal of the pinhole SPECT apparatus according to the first embodiment. FIG. 2 is a view showing the arrangement of detectors. FIG. 3 is a cross-sectional view taken along the line BB in FIG. FIG. 5 is a block diagram showing the entire configuration of the pinhole SPECT apparatus. FIG. 6 is a diagram showing the vicinity of a base of an example of the pinhole SPECT apparatus according to the second embodiment. 7 is a view showing the vicinity of a pedestal of another example of the pinhole SPECT apparatus according to the second embodiment. FIG. 8 is a view showing the vicinity of a pedestal of an example of the pinhole SPECT apparatus according to the third embodiment. FIG. 9 is a view showing a swing mechanism of the pinhole SPECT apparatus. FIG. 10 is a perspective view of a part of the pinhole SPECT apparatus according to the fourth embodiment. FIG. 11 is a radiation count value obtained by SPECT and arterial blood. Graph of the count value [Explanation of symbols]
10 pedestals, 12 pinhole collimator, 14 radiation detector, 16 gantry, 18 rotation drive device, 22 swing mechanism, 24 tilt mechanism, 26 rotation mechanism.

Claims (7)

A pedestal that can support the subject,
One or more detector blocks combining a pinhole collimator and a position detection type radiation detector;
A rotation mechanism for rotating the detector block around the pedestal, mounting the detector block on a rotating surface including the center of the field of view while fixing the center of the field of view of the radiation detector at one point;
A control device for controlling the rotation of the rotation mechanism;
A swinging mechanism that periodically swings the pedestal relative to the rotating shaft while synchronizing with the rotation of the rotating mechanism;
A single photon emission computed tomography apparatus comprising: a storage device that receives and stores radiation measurement data detected by the detector from the detector block. A pedestal that can support the subject,
A plurality of detector blocks combining a pinhole collimator and a position detection type radiation detector;
A rotation mechanism for rotating the detector block around the pedestal, with the detector block fixed on the center of the field of view of the radiation detector at one point, and mounted on the rotation surface including the center of the field of view and the rotation surface; ,
A control device for controlling the rotation of the rotation mechanism;
A single photon emission computed tomography apparatus comprising: a storage device that receives and stores radiation measurement data detected by the detector from the detector block. further,
The single photon emission computed tomography apparatus according to claim 2, further comprising a moving mechanism that moves the pedestal in a direction parallel to the rotation axis while synchronizing with the rotation of the rotation mechanism. A pedestal that can support the subject,
A plurality of detector blocks combining a pinhole collimator and a position detection type radiation detector;
A plurality of the detector blocks are attached by shifting the center of the field of view of the radiation detector, and a rotation mechanism for rotating the detector blocks around the pedestal;
A control device for controlling the rotation of the rotation mechanism;
A single photon emission computed tomography apparatus comprising: a storage device that receives and stores radiation measurement data detected by the detector from the detector block. A pedestal that can support the subject,
A plurality of detector blocks combining a pinhole collimator and a position detection type radiation detector;
A rotation mechanism for rotating the pedestal at the center of the field of view of the radiation detector;
A mechanism for tilting the pedestal from the rotation axis at the center of the field of view of the radiation detector;
A control device for controlling the rotation of the rotation mechanism;
A single photon emission computed tomography apparatus comprising: a storage device that receives and stores radiation measurement data detected by the detector from the detector block. A plurality of detector blocks having a position detection type radiation detector pinhole collimator is mounted such that the radiation detector comprises always an object in view, the periphery of the support can mount an object, one rotating surface Placed at any position to detect radiation not only on the rotating surface but also outside the rotating surface ,
A single-photon emission computed tomography method in which a detector block is moved around a pedestal so that the detector always includes a subject in the field of view, and radiation measurement data is collected by the detector block and recorded in a storage device. Fix one or more detector blocks equipped with a position detection type radiation detector equipped with a pinhole collimator so that the radiation detector always includes the subject in the field of view,
A single photon emission computed tomography method in which the pedestal is tilted and rotated, and radiation measurement data is collected by a detector block and recorded in a storage device.

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