JP2013011509A - Nuclear medicine diagnosis device and spect photographing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nuclear medicine diagnosis device suitable for photographing an organ existing at a position decentered from a center of a body cross section, and a SPECT photographing method.SOLUTION: A nuclear medicine diagnosis device for detecting radiation rays emitted from a radioactive isotope administered inside a patient's body and for obtaining image data inside the patient's body is provided with: first and second gamma cameras each including an asymmetric fan beam type collimator which limits the incident direction of the radiation rays and a detector for detecting the radiation rays having passed through the collimator; a rotary ring to which the first and second gamma cameras are attached rotatably around the patient's body axis in such a manner that they are combined by a set angle based on 90 degrees so that the collimators are directed toward an observation object of the patient's body; and a rotation control part for rotating the first and second gamma cameras around the patient's body axis within a preset range.

Description

  Embodiments described herein relate generally to a nuclear medicine diagnostic apparatus and a SPECT imaging method suitable for SPECT imaging (Single Photon Emission Computed Tomography) in which a gamma camera is rotated around a subject.

  Conventionally, there is a nuclear medicine diagnostic apparatus as a medical image diagnostic apparatus. The nuclear medicine diagnostic device images a RI distribution in a subject by administering a drug labeled with a radioisotope (RI) into the subject and detecting gamma (γ) rays emitted from the RI. To do. As a detector, imaging is performed using a gamma camera (a camera that detects gamma rays and captures a two-dimensional distribution of RI). As a main method for nuclear medicine examination, a SPECT imaging method is widely known in which a gamma camera is rotated around a subject to obtain a predetermined tomographic image.

  The gamma camera has a flat plate shape as a whole, includes a collimator arranged two-dimensionally and a detector that converts gamma rays into an electrical signal, and is supported by a rotating ring and can rotate around the subject. The electrical signal from the detector is collected by a data collection device (DAS).

  FIG. 10 is an explanatory diagram showing the parallel beam collimator 101A, and FIG. 11 is an explanatory diagram showing the fan beam collimator 101B. 10 and 11, collimators 101 </ b> A and 101 </ b> B give the detector 102 directivity, and allow gamma rays from a certain direction to enter the detector 102. The detector 102 receives gamma rays that have arrived through the collimators 101A and 101B and converts them into electrical signals.

  The parallel beam collimator 101A shown in FIG. 10 has a wide effective field of view but low sensitivity. On the other hand, the fan beam collimator 101B in FIG. 11 has a symmetrical fan beam shape, and can improve the sensitivity due to the effect of enlarging the object to be photographed, but the effective field of view is narrowed. In the conventional SPECT inspection, the symmetrical fan beam collimator 101B (FIG. 11) has been used to improve the sensitivity. However, the fan beam collimator 101B has a drawback that the measurement field of view is smaller than that of the parallel beam collimator 101A. .

  When a transverse layer image is captured, the entire organ to be imaged needs to be within the field of view in all projection directions (detector positions). If it does not fit within the field of view, artifacts will occur, resulting in degradation of image quality and quantitativeness. In particular, when the organ to be measured is not at the center of the field of view (for example, measurement of the left ventricle of the heart), the fan beam collimator 101B often does not fit in the field of view.

  FIG. 11 shows an example in which the heart 103 is imaged using the fan beam collimator 101B. However, a part of the left ventricle 104 protrudes from the effective field of view of the fan beam. Therefore, further improvement is demanded in imaging when the organ to be measured is not in the center of the imaging field of view.

JP 2001-59872 A

  The problem to be solved by the invention is to provide a nuclear medicine diagnostic apparatus and a SPECT imaging method suitable for imaging an organ existing at a position eccentric from the center of the body cross section such as the heart (left ventricle).

  The nuclear medicine diagnostic apparatus according to the embodiment is a nuclear medicine diagnostic apparatus that detects radiation emitted from a radioisotope administered into a subject and obtains image data in the subject. The collimator includes first and second gamma cameras, and a first and second gamma cameras, each of which includes an asymmetric fan beam type collimator that limits a direction and a detector that detects radiation that has passed through the collimator. A rotating ring attached in a rotatable manner around the body axis of the subject in combination with a set angle based on 90 degrees so as to face the observation target of the subject, and the first and second gamma cameras A rotation control unit that rotates within a preset range around the body axis of the subject.

The perspective view which shows the whole structure of the nuclear-medical-diagnosis apparatus which concerns on one Embodiment. The block diagram which shows the structure of the nuclear medicine diagnostic apparatus which concerns on one Embodiment. The block diagram which shows the collimator and detector in one Embodiment. The lineblock diagram of the gamma camera in one embodiment. Explanatory drawing which shows the rotation state of the two gamma cameras in one Embodiment. Explanatory drawing which shows the other rotation state of the two gamma cameras in one Embodiment. The block diagram which made the position of one gamma camera variable in one Embodiment. The block diagram which combined the gamma camera in the obtuse angle in 2nd Embodiment. The block diagram which combined the gamma camera with the acute angle in 2nd Embodiment. Explanatory drawing which shows the parallel beam collimator of a gamma camera. Explanatory drawing which shows the fan beam collimator of a gamma camera.

  Hereinafter, a nuclear medicine diagnosis apparatus according to an embodiment will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected about the same location.

(First embodiment)
FIG. 1 is a perspective view showing the overall configuration of one embodiment of the nuclear medicine diagnostic apparatus of the present invention. In FIG. 1, the nuclear medicine diagnosis apparatus 1 includes a bed 10 and a gantry 20. The bed 10 includes a top plate 11 on which the subject P is placed and support portions 12 and 13 that support the top plate 11. The support parts 12 and 13 can move the top plate 11 in the vertical direction by a drive mechanism (not shown), and raise and lower the top plate 11 in the vertical direction.

On the other hand, the gantry 20 includes a fixed base 21, a rotary ring 22 rotatably attached to the fixed base 21, and two gamma cameras 23 supported by the rotary ring 22. The gamma camera 23 includes a collimator 24 that limits the incident direction of radiation (gamma rays) emitted from the RI administered to the subject P, and a detector 25 that converts the incident radiation (gamma rays) into an electrical signal. Further, although not shown in the figure, it has a data collection unit (DAS) that collects electrical signals.

The detector 25 includes a scintillator provided on the radiation incident surface side and a number of photomultiplier tubes arranged on the back surface of the scintillator. The scintillator converts radiation into light, and the photomultiplier tube detects the light emitted from the scintillator and converts it into an electrical signal. The rotating ring 22 has a support member for supporting the two gamma cameras 23, and the rotating ring 22 is rotated by the drive unit so that the two gamma cameras 23 are both around the body axis of the subject P ( (α direction).

The top plate 11 of the bed 10 is movable with respect to the gantry 20, and the subject P can be inserted into the rotating ring 22. Alternatively, the gantry 20 can be moved along a rail provided on the floor surface, and the gantry 20 can be moved in the direction of the bed 10. Thereby, the gantry 20 and the bed 10 are relatively movable in the directions of arrows Y1-Y2 in FIG.

FIG. 2 is a block diagram illustrating a configuration of the nuclear medicine diagnosis apparatus 1 according to the first embodiment. In FIG. 2, two gamma cameras 23 are attached to the rotating ring 22 of the gantry 20, and the subject P placed on the top plate 11 of the bed 10 is inserted into the opening of the gantry 20. The bed 10 is provided with a drive unit 14 that controls the height position of the top plate 11 and the movement in the gantry direction.

  The gamma camera 23 includes a collimator 24 that limits the incident direction of gamma rays and a detector 25 that converts the incident gamma rays into electrical signals, and is emitted from a nuclide (radioisotope: RI) injected into the subject P. The distribution of gamma rays is detected two-dimensionally, and the detection result is sent to the data collection unit 32 described later.

  The bed 10 and the gantry 20 are controlled by a computer system 30. The computer system 30 includes a bus line 301, and a system control unit 31, a data collection unit 32, a data processing unit 33, a data storage unit 34, an input unit 35, and a display unit 36 are connected to the bus line 301.

  The system control unit 31 controls the overall operation of the computer system 30. The data collection unit 32 generates digital projection data based on the detection signal sent from the gamma camera 23, and sends this projection data to the data processing unit 33. The data processing unit 33 processes the data collected by the data collecting unit 32 and generates a projection image (image data) when viewed from a predetermined photographing direction. The data storage unit 34 stores image data.

  The input unit 35 is operated by an operator, and gives various kinds of operation information such as rotation of the rotating ring 22, start of shooting, and stop of shooting by operation of the input unit 35. The display unit 36 displays the projection image and the like generated by the data processing unit 33 and also displays operation information and the like given by the operator via the input unit 35. The input unit 35 and the display unit 36 together with the system control unit 31 constitute a user interface.

  Further, a camera control unit 37 that controls the gamma camera 23 and a bed driving unit 38 that controls the driving unit 14 provided on the bed 10 are connected to the bus line 301. Further, a rotation control unit 39 that rotates the rotation ring 22 and rotates the gamma camera 23 around the subject P (α direction) is provided. The bed driving unit 38 controls the driving unit 14 under the control of the system control unit 31 to control the position of the top plate 11. Further, when the gantry 20 is configured to be movable, the system controller 31 controls the position of the gantry 20 in the arrow Y1-Y2 direction. A network interface 40 is connected to the bus line 301 and can communicate with an external device (for example, a computer terminal) via the network.

  The computer system 30 operates under the control of the system control unit 31 and generates image data for nuclear medicine diagnosis from detection signals of the two gamma cameras 23. In actual data collection, the rotating ring 22 is rotated and the gamma camera 23 is rotated around the subject P (α direction) to perform imaging from a plurality of imaging directions.

  FIG. 3 is a configuration diagram showing the collimator 24 and the detector 25 in the first embodiment. The collimator 24 limits the incident direction of gamma rays, and the detector 25 converts the incident gamma rays into electrical signals. The collimator 24 uses an asymmetric fan beam shape.

  That is, the collimator 24 in FIG. 3 has a fan virtual focal point 41 at a position depending from one end of the detector 25, and the partition walls 241 and 242 of the collimator 24 provided from one end to the other end of the detector 25. ... 24n is an asymmetric fan beam collimator in which the focal point 41 is directed. That is, the virtual focal point 41 is biased toward one end of the detector 25, and the fan beam shape is asymmetric. When the SPECT rotation center is 42, the SPECT rotation center 42 is positioned inside the path from the virtual focus 41 within the effective viewing angle 43 of the asymmetric fan beam toward the outermost partition 24n.

  In the first embodiment, two gamma cameras 23 including an asymmetric fan beam collimator 24 and a detector 25 as shown in FIG. 3 are combined in an L shape with a set angle based on 90 degrees (in FIG. 4). Two gamma cameras 23 are combined at an angle of 90 degrees). In the following, the symbols A and B are attached to divide the two gamma cameras.

  FIG. 4 is a configuration diagram of gamma cameras 23A and 23B in which detectors 25A and 25B are combined at an angle of 90 degrees. In the two detectors 25A and 25B, one end on the partition 241 side approaches at an angle of approximately 90 degrees so that the collimators 24A and 24B face the observation target of the subject P, and the other end on the partition 24n side There are virtual focal points 41A and 41B.

  The organ to be measured is a small organ at a position eccentric from the center of the body axis of the subject, such as the left ventricle of the heart. The two gamma cameras 23A and 23B rotate around the subject with a reference range of 90 degrees, for example, rotate by 90 degrees or an angle close to 90 degrees to perform imaging. The eccentric organ is within a region 45 that is ¼ of the effective visual field (circle 44) in the cross section. For example, in the case where the heart is imaged, the left ventricle is in the quarter region 45 in FIG.

  FIGS. 5A to 5C show a state in which the two gamma cameras 23A and 23B are rotated 90 degrees around the subject. 5A to 5C, for the sake of convenience, the gamma camera 23A is shown in the upper stage and the gamma camera 23B is shown in the lower stage for the sake of convenience (actually as shown in FIG. 4). At an angle of 90 degrees).

  As shown in FIG. 5 (a), assuming that the detector 24A is located at the upper left and the detector 24B is located at the upper right, the rotation starting point is as shown in FIG. 5 (b). In FIG. 5 (c), it further rotates by 45 degrees, and rotates 90 degrees in total. The subject's left ventricle is always within the region 45 that is ¼ of the effective visual field of the gamma cameras 23A and 23B. Therefore, if the two gamma cameras 23A and 23B are rotated 90 times and an area of 180 degrees is photographed, the field of view is not lost in the region 45 that is 1/4 of the effective field of view (circle 44) in all projection directions. Therefore, it is possible to obtain a high-quality and highly quantitative SPECT image that does not cause artifacts due to data loss.

  The rotation start point can be set according to the organ to be imaged. For example, as shown in FIGS. 6A to 6C, when an imaging target is present in the lower left quarter region 45 ′ of the effective visual field 44, the detector 24A is used as shown in FIG. A state where the detector 24B is located at the lower right and the detector 24B is located at the lower left is defined as a rotation start point. 6B rotates 45 degrees clockwise from the starting point, and in FIG. 6C, it further rotates 45 degrees, so that it rotates 90 degrees in total. Even in FIG. 6, the observation target of the subject is always in the region 45 'that is 1/4 of the effective visual field of the gamma cameras 23A and 23B. Therefore, if the two gamma cameras 23A and 23B are rotated 90 times to capture a 180 degree region, the field of view is not lost in the region 45 'that is 1/4 of the effective field of view (circle 44) in all projection directions.

  In the first embodiment, various modifications can be made. For example, as shown in FIG. 7, the gamma cameras 23A and 23B can be combined at an angle of 90 degrees, and one of the gamma cameras 23A and 23B can be made variable. For example, in FIG. 7A, the gamma camera 23B can be moved in the direction of the observation target while maintaining an angle of 90 degrees with respect to the gamma camera 23A. The position of the moved gamma camera 23B is indicated by a dotted line.

  Further, as shown in FIG. 7B, the gamma camera 23A can be moved in the direction of the observation target while maintaining an angle of 90 degrees with respect to the gamma camera 23B. The position of the moved gamma camera 23A is indicated by a dotted line. In this way, by making the relative positions of the gamma cameras 23A and 23B variable, more accurate shooting can be performed according to the position of the observation target.

(Second Embodiment)
Next, a nuclear medicine diagnostic apparatus according to the second embodiment will be described. In the above-described first embodiment, the gamma cameras 23A and 23B are arranged at an angle of 90 degrees. However, in the second embodiment, the gamma cameras 23A and 23B are combined at a setting angle (for example, 90 degrees ± 15 degrees) with 90 degrees as a reference. It's a thing.

  FIG. 8 shows a combination of the gamma cameras 23A and 23B at an obtuse angle of about 105 degrees so that the collimators 24A and 24B face the observation target of the subject P. Speaking of the gamma camera 23A, the collimator 24A of FIG. 8 has a virtual focus 41A at a position wider than 90 degrees from one end of the detector 25A. 24n of the collimator 24 provided from one end to the other end of the detector 25A is directed toward the virtual focal point 41 to form an asymmetric fan beam collimator. The gamma camera 23B has a symmetrical configuration with respect to the gamma camera 23A, and the virtual focal points 41A and 41B are in opposite positions.

  FIG. 9 shows a combination of gamma cameras 23A and 23B at an acute angle of about 75 degrees so that the collimators 24A and 24B face the observation target of the subject P. Speaking of the gamma camera 23A, the collimator 24A in FIG. 9 has the virtual focal point 41A at a position narrower than 90 degrees from one end of the detector 25A. 24n of the collimator 24 provided from one end to the other end of the detector 25A is directed toward the virtual focal point 41 to form an asymmetric fan beam collimator. The gamma camera 23B has a symmetrical configuration with respect to the gamma camera 23A, and the virtual focal points 41A and 41B are in opposite positions.

  In the second embodiment, the combination angle and rotation angle of the gamma cameras 23A and 23B may be changed based on 90 degrees according to the position of the eccentric observation target.

  According to the embodiment described above, when performing the SPECT inspection, the measurement sensitivity is improved and the position resolution is improved by photographing the observation object by combining two gamma cameras having asymmetric fan beam collimators. be able to. In addition, by simply rotating the gamma camera about 90 degrees, it is possible to shoot the subject without losing the field of view.

  As mentioned above, although several embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

DESCRIPTION OF SYMBOLS 1 ... Nuclear medicine diagnostic apparatus 10 ... Bed 11 ... Top plate 20 ... Stand 22 ... Rotating rings 23A, 23B ... Gamma camera 24A, 24B ... Collimator 25A, 25B ... Detection part 30 ... Computer system 31 ... System control part 39 ... Rotation control Part 41A, 41B ... Virtual focus

Claims (10)

A nuclear medicine diagnostic apparatus for detecting radiation emitted from a radioisotope administered in a subject and acquiring image data in the subject,
First and second gamma cameras including an asymmetric fan beam type collimator that limits the incident direction of the radiation, and a detector that detects the radiation that has passed through the collimator;
The first and second gamma cameras are combined at a set angle with 90 degrees as a reference so that the collimator faces the observation target of the subject, and are attached to be rotatable around the body axis of the subject. A rotating ring,
A nuclear medicine diagnostic apparatus comprising: a rotation control unit configured to rotate the first and second gamma cameras within a preset range around the body axis of the subject.   The first and second gamma cameras set a virtual focus at a position close to one end side of the detector, and the collimator is directed from the one end portion of the detector to the virtual focus along the other end portion. The nuclear medicine diagnostic apparatus according to claim 1, comprising a plurality of partition walls formed in the manner described above.   The nuclear medicine diagnosis apparatus according to claim 1, wherein an eccentric observation target of the subject is placed in an imaging effective visual field formed by the first and second gamma cameras.   2. The nuclear medicine diagnosis apparatus according to claim 1, wherein each of the first and second gamma cameras rotates around the observation target of the subject with a reference range of 90 degrees.   5. The nuclear medicine diagnosis apparatus according to claim 4, wherein the first and second gamma cameras determine a rotation start point according to an observation target of the subject and rotate about the 90 degrees from the rotation start point. A SPECT imaging method for detecting radiation emitted from a radioisotope administered into a subject and acquiring image data in the subject,
First and second gamma cameras including an asymmetric fan beam type collimator that limits the incident direction of the radiation and a detector that detects the radiation that has passed through the collimator, and the collimator serves as an observation target of the subject. Combine at a setting angle with 90 degrees as a reference,
A SPECT imaging method in which the first and second gamma cameras are rotated around a body axis of a subject within a preset range.   The first and second gamma cameras set a virtual focus at a position close to one end side of the detector, and the collimator is directed from the one end portion of the detector to the virtual focus along the other end portion. The SPECT imaging method according to claim 6, further comprising a plurality of partition walls formed in the manner described above.   The SPECT imaging method according to claim 6, wherein an observation object in which the subject is decentered is within an imaging effective visual field formed by the first and second gamma cameras.   7. The SPECT imaging method according to claim 6, wherein each of the first and second gamma cameras rotates around the observation target of the subject with a reference range of 90 degrees.   10. The SPECT imaging method according to claim 9, wherein the first and second gamma cameras determine a rotation start point according to an observation target of the subject, and rotate with the 90 degrees as a reference range from the rotation start point.

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