JP2007232685A - Mammography unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To photograph an RI distribution image of a mammary area of a subject with sufficient sensitivity. <P>SOLUTION: In this mammography unit of the present invention, the RI distribution image of the mammary area of the subject is photographed with the sufficient sensitivity, as a result capable of enhancing the γ-ray detection sensitivity of a γ-ray detection mechanism 3 by increase of a γ-ray quantity detected by the γ-ray detection mechanism 3, since the γ-ray detection mechanism 3 for detecting the γ-ray generated by a radioactive isotope element dosed in the subject to arrive at the mammary area can be moved along a direction approaching to the subject by a detection system approach and separation moving mechanism 24 to approach to the mammary area of the subject. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a mammography apparatus that performs breast cancer screening using a radioisotope (RI) that is a radioisotope, and more particularly to a technique for taking an RI distribution image of a breast region of a subject.

In the case of an X-ray imaging mammography apparatus that has been used in medical institutions such as hospitals for breast cancer screening, an X-ray transmission image that provides anatomical information about the breast area of the subject is acquired and transmitted through the X-ray transmission system. Breast cancer screening is performed by checking the image for abnormalities.
However, it is not always possible to perform sufficient breast cancer screening using only anatomical information provided by X-ray transmission images.

  Therefore, breast cancer screening is performed by taking an RI distribution image of the breast area of the subject using a PET (positron emission tomography) device that can take an RI distribution image corresponding to the distribution of the RI administered to the subject. Can be considered. This is because the RI distribution image photographed by the PET apparatus provides biofunctional information that is different from the anatomical information, so that there is a possibility that a breast cancer missed on the X-ray transmission image can be found.

  As shown in FIG. 13, the conventional PET apparatus has a top plate 91 on which the subject m is placed, and an opening (tunnel) 92A through which the top plate 91 enters and exits while the subject m is placed. A large gantry 92 is provided, and a ring-type γ-ray detector 93 shown in FIG. 14 or a flat-type γ-ray detector 94 shown in FIG. The γ-ray detectors 93 and 94 are composed of a scintillator and a photomultiplier (photomultiplier tube) or the like (see, for example, Non-Patent Documents 1 and 2).

When taking a RI distribution image with a conventional PET apparatus, the energy of 511 keV generated by the RI administered to the subject m that has entered the opening 92 </ b> A of the gantry 92 while the subject m is placed on the top 91. Γ rays (annihilation γ rays) are detected by the γ ray detector 93 or the γ ray detector 94. The γ-ray detection signals output from the γ-ray detector 93 and the γ-ray detector 94 are collected as emission data for acquiring the RI distribution image, and a reconstruction process is performed based on the collected emission data to obtain a tomogram. An RI distribution image of image type or plane image type is acquired. In the case of a PET apparatus, two annihilation γ-rays that are simultaneously generated by the disappearance of an RI positron such as ¹¹ C administered to the subject m and proceed in the opposite direction are converted into a γ-ray detector 93 or a γ-ray detector 94. Emission data is collected when they are detected at the same time (when γ rays are counted simultaneously).

Seminars in Nuclear Medicine, vol.XXXIV, No.2,2004: 87-111 J Nucl Med 2003; 44: 756-769

However, the conventional PET apparatus has a problem in that it cannot capture an RI distribution image of the breast region of the subject m with sufficient sensitivity.
This is because the gantry 92 into which the subject m enters has a large opening 92A, and the γ-ray detector 93 or the γ-ray detector 94 is far from the subject m and cannot detect γ-rays with sufficient sensitivity. .

  The present invention has been made in view of such circumstances, and an object thereof is to provide a mammography apparatus that can capture an RI distribution image of a breast region of a subject with sufficient sensitivity.

In order to achieve such an object, the present invention has the following configuration.
That is, the mammography apparatus according to the invention described in claim 1 includes: (A) γ-ray detection means for detecting γ-rays generated by a radioisotope administered to a subject and arriving at a breast region; and (B) the γ A detection system contact / separation moving means for moving at least a part of the line detection means in a direction in contact with and away from the subject; and (C) a γ ray detection signal output from the γ ray detection means Emission data collection means for collecting emission data, and (D) RI distribution image acquisition means for acquiring an RI distribution image based on the emission data collected by the emission data collection means. is there.

  [Operation / Effect] When an RI distribution image is taken by the mammography apparatus according to the first aspect of the present invention, gamma rays generated by RI which is a radioisotope that is administered to the subject and arrives at the breast region by the gamma ray detection means. Is detected, and the emission data collection means collects the γ-ray detection signal output from the γ-ray detection means as emission data for acquiring the RI distribution image. Then, an RI distribution image of the breast region of the subject is acquired by the RI distribution image acquisition unit based on the emission data collected by the emission data collection unit.

  In the mammography apparatus according to the first aspect of the present invention, when the RI distribution image is taken, at least a part of the γ-ray detection means is moved in the direction approaching the subject by the detection system contact / separation movement means. Approach the breast area of the specimen. If at least a part of the γ-ray detection means approaches the breast region of the subject, the amount of γ-rays detected by the γ-ray detection means increases and the detection sensitivity of γ-rays increases.

That is, in the case of the mammography apparatus according to the first aspect of the present invention, at least a part of the γ-ray detection means for detecting γ-rays generated by the radioisotope that is administered to the subject and arrives at the breast region is detected by the detection system contact / separation movement means Since it moves closer to the subject and approaches the breast region of the subject, the amount of γ-rays detected by the γ-ray detection means increases and the γ-ray detection sensitivity of the γ-ray detection means increases.
Therefore, according to the mammography apparatus of the first aspect of the invention, an RI distribution image of the breast region of the subject can be taken with sufficient sensitivity.

  According to a second aspect of the present invention, in the mammography apparatus according to the first aspect, the radioisotope administered to the subject is a positron type radioisotope, and the emission data collecting means is arranged in the opposite direction. Only the γ-ray detection signals when the annihilation γ-rays traveling are simultaneously detected by the γ-ray detector are collected as emission data.

  [Operation / Effect] In the case of the apparatus of the invention of claim 2, the annihilation γ-rays generated by the emission data collection means accompanying the annihilation of the positron emitted from the radioisotope administered to the subject and traveling in the opposite direction are γ Since only the γ-ray detection signals simultaneously detected by the line detector are collected as emission data, an RI distribution image of the positron-type radioisotope administered to the subject can be taken.

  The invention described in claim 3 is the mammography apparatus according to claim 1 or 2, wherein the γ-ray detection means includes a first γ-ray detector and a second γ-ray detection that face each other with the breast region of the subject interposed therebetween. The detection system contact / separation moving means moves the first and second γ-ray detectors.

  [Operation / Effect] In the case of the apparatus of the invention of claim 3, the first γ-ray detector and the second γ-ray detector facing each other with the breast region of the subject in between are moved toward the subject by the detection system contact / separation moving means. Gamma rays are detected with high sensitivity in a state where the gamma ray detection means is moved closer to the subject.

  According to a fourth aspect of the present invention, in the mammography apparatus according to the first or second aspect, the γ-ray detection means includes a plurality of γ-ray detectors surrounding the breast region of the subject, and a detection system connection. The separating / moving means moves all the γ-ray detectors.

  [Operation / Effect] In the case of the apparatus of the invention of claim 4, a plurality of γ-ray detectors surrounding the breast region of the subject are moved toward the subject by the detection system contact / separation moving means, and the γ-ray detection means is moved. Gamma rays are detected with high sensitivity in the state of being close to the subject.

  The invention according to claim 5 is the mammography apparatus according to claim 4, wherein the plurality of γ-ray detectors are moved in a direction orthogonal to the direction in which the γ-ray detector is in contact with and away from the subject. A moving means is further provided.

  [Operation / Effect] In the case of the apparatus of the invention of claim 5, the detection system contact / separation moving means moves the plurality of γ-ray detection means toward the subject, and the detection system slide movement means has a plurality of γ-rays. Since the detection means is moved in a direction perpendicular to the direction of contact with and away from the subject, the plurality of γ-ray detection means can be brought closer to the subject while avoiding mutual interference.

  According to a sixth aspect of the present invention, in the mammography apparatus according to the first or second aspect, the γ-ray detection means includes a concave γ-ray detector that receives the breast region of the subject in a prone posture, and a breast region of the subject. And a detecting system contact / separation moving means moves the flat γ-ray detector.

  [Operation / Effect] In the case of the apparatus of the invention of claim 5, the flat γ-ray detector for receiving the breast region of the subject in the prone posture and the flat γ-ray detector facing the back of the breast region of the subject is flat. The γ-ray detector is moved toward the subject, and the γ-ray is detected with high sensitivity in a state where the γ-ray detection means is close to the subject.

In the case of the mammography apparatus according to the present invention, at least a part of the γ-ray detection means for detecting γ-rays generated by the radioisotope that is administered to the subject and arrives at the breast region is detected with respect to the subject by the detection system contact / separation moving means. Since it is moved closer to the breast area of the subject, the amount of γ-rays detected by the γ-ray detection means increases and the γ-ray detection sensitivity of the γ-ray detection means increases.
Therefore, according to the mammography apparatus of the present invention, an RI distribution image of the breast region of the subject can be captured with sufficient sensitivity.

  A first embodiment of the mammography apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of a PET (positron emission tomography) type mammography apparatus according to the first embodiment, and FIG. 2 is a side view showing the configuration around the γ-ray detection mechanism of the apparatus of the first embodiment. FIG. 3 is a front view showing a configuration around the γ-ray detection mechanism of the apparatus of the first embodiment, FIG. 4 is a perspective view showing a breast cancer screening situation by the apparatus of the first embodiment, and FIG. 5 is another breast cancer by the apparatus of the first embodiment. It is a perspective view which shows the medical examination situation.

  In the mammography apparatus according to the first embodiment, as illustrated in FIGS. 1 to 5, the first γ-ray detector 1 and the second γ-ray detector 2 that are opposed to each other with the breast region ma of the subject m interposed between the subject m and the subject m. A γ-ray detection mechanism 3 that detects γ-rays generated by the radioisotope (RI) that has been administered and arrived at the breast region ma is configured. The first γ-ray detector 1 and the second γ-ray detector 2 are a scintillator that converts incident γ-rays into light, and a photomultiplier that is installed vertically and horizontally that converts the light emitted from the scintillator into electricity and outputs it. Is a flat type two-dimensional detector. In addition, an external radiation source 4 that irradiates radiation when collecting transmission data for absorption correction is installed in front of the first γ-ray detector 1 and the second γ-ray detector 2.

  The apparatus according to the first embodiment includes a fixed rail member 5 and a movable rail member 6 disposed along the ceiling UW, and a detection system that conveys the γ-ray detection mechanism 3 along the fixed rail member 5 and the movable rail member 6. A transport mechanism 7 is provided. As shown in FIG. 2, the fixed rail member 5 is directly attached to the ceiling UW in a direction in which the rail extends in a direction parallel to the horizontally extending Xa axis. As shown in FIG. 3, the movable rail member 6 is suspended below the fixed rail member 5 so as to be movable in a direction in which the rail extends in a direction parallel to the Ya axis extending horizontally in a direction orthogonal to the Xa axis. Yes.

  The detection system transport mechanism 7 suspends the first traveling unit 8 that travels while being guided by the fixed rail member 5 while the movable rail member 6 is suspended, and the detection system holding rod 10 that retains the γ-ray detection mechanism 3. And a second traveling portion 9 that travels while being guided by the movable rail member 6. And in the case of the 1st driving | running | working part 8, as the wheel drive part 8A act | operates and the wheel 8B rotates, the 1st driving | running | working part 8 is parallel to a Xa axis | shaft on the fixed rail member 5 with the movable rail member 6. Drive in the direction. In the case of the second traveling unit 9, as the wheel driving unit 9A is activated and the wheel 9B rotates, the second traveling unit 9 moves the detection system holding rod 10 on the movable rail member 6 in a direction parallel to the Ya axis. Drive to. Accordingly, the detection system holding rod 10 moves in a direction parallel to the Xa axis by traveling of the first traveling unit 8, and the detection system holding rod 10 moves in a direction parallel to the Ya axis by traveling of the second traveling unit 9.

  The γ-ray detection mechanism 3 is attached and held on the lower end side of the detection system holding rod 10. Therefore, as the detection system holding rod 10 is moved by the traveling of the first traveling unit 8, the γ-ray detection mechanism 3 is conveyed in the Xa axis direction, and the detection system holding rod 10 is moved by the traveling of the second traveling unit 9. As a result, the γ-ray detection mechanism 3 is conveyed in the Ya-axis direction. Thus, when the γ-ray detection mechanism 3 is conveyed, the imaging location changes in the horizontal direction.

  In addition, the apparatus according to the first embodiment includes a detection system lifting mechanism 11 that lifts and lowers the γ-ray detection mechanism 3. The detection system holding rod 10 is composed of a cylindrical outer rod 10A and an inner rod 10B. The upper end of the outer rod 10A is fixed to the second traveling portion 9, and the inner rod 10B can move vertically with respect to the outer rod 10A. Is interpolated. The detection system elevating mechanism 11 includes a rack 11A installed on the inner rod 10B side, a pinion 11B installed on the outer rod 10A side, and an electric motor 11C, and the pinion 11B is rotated by the rotation of the electric motor 11C. As the rack 11A meshing with the pinion 11B moves as it turns, the inner rod 10B moves up or down, and the γ-ray detection mechanism 3 rises in the direction of the Za axis extending vertically as shown in FIG. Get off. When the γ-ray detection mechanism 3 moves up and down, the imaging location changes in the vertical direction.

  On the other hand, the γ-ray detection mechanism 3 is attached to the lower end portion of the detection system holding rod 10 via the detection system rotation mechanism 12 and the detection system attachment member 13. The detection system rotating mechanism 12 includes a horizontal shaft member 12A having a central axis that matches the Xa axis, and an electric motor 12B that rotates the horizontal shaft member 12A with the central axis as a rotational axis, and is provided at the tip of the horizontal shaft member 12A. The γ-ray detection mechanism 3 is attached together with the detection system attachment member 13, and as the electric motor 12B rotates and the horizontal shaft member 12A rotates, the γ-ray detection mechanism 3 moves along with the detection system attachment member 13 together with Xa. Rotate around an axis.

  Thus, the imaging direction can be changed when the γ-ray detection mechanism 3 rotates. For example, as shown in FIG. 4, not only can the breast area ma of the subject m be photographed from above and below, but also the γ-ray detection mechanism 3 is rotated by 90 ° to obtain the breast area of the subject m as shown in FIG. Ma can also be taken from the front-rear direction. When photographing from the front-rear direction as shown in FIG. 5, it is possible to photograph including the base of the side that is the edge of the breast region ma.

  The detection system transport mechanism 7 transports the γ-ray detection mechanism 3 while receiving transport operation data according to an operator's operation or a preset program from the transport control unit 14. The detection system elevating mechanism 11 elevates and lowers the γ-ray detection mechanism 3 while receiving elevating control data corresponding to an operator's operation and a preset program from the elevating control unit 15. The detection system rotation mechanism 12 rotates the γ-ray detection mechanism 3 while receiving rotation control data corresponding to an operator's operation or a preset program from the rotation control unit 16.

  Further, the conveyance control unit 14 sends conveyance control data for conveyance by the γ-ray detection mechanism 3 as conveyance position data indicating the conveyance position of the γ-ray detection mechanism 3. The elevation control unit 15 sends up / down control data for raising / lowering the γ-ray detection mechanism 3 as vertical position data indicating the vertical position of the γ-ray detection mechanism 3. The rotation control unit 16 sends rotation control data for rotation of the γ-ray detection mechanism 3 as rotation angle data indicating the rotation position of the γ-ray detection mechanism 3.

  In addition, as shown in FIG. 1, the apparatus of the first embodiment includes an emission data collection unit 17, a transmission data collection unit 18, an absorption correction unit 19, and an RI distribution image acquisition unit 20 that are arranged after the γ-ray detection mechanism 3. In addition, a display monitor 21 for displaying an RI distribution image, an operation menu of the apparatus, an operation unit 22 for inputting data and commands necessary for the operation of the apparatus, and the like are provided.

  The emission data collection unit 17 collects γ-ray detection signals output from both the first and second γ-ray detectors 1 and 2 as emission data for acquiring RI distribution images. In addition, in the case of the emission data collection unit 17, the annihilation γ-rays generated along with the annihilation of the positrons emitted from the radioisotope administered to the subject m and traveling in the opposite directions are the first and second γ-rays. Only the γ-ray detection signals detected simultaneously by the detectors 1 and 2 are collected as emission data.

That is, γ-ray detection when one of the annihilation γ-rays traveling in the opposite direction is detected by the first γ-ray detector 1 and at the same time the other γ-ray is detected by the second γ-ray detector 2. Only the signal is collected as emission data. Examples of positron-type RI administered to the subject m include ¹¹ C, ¹³ N, ¹⁵ O, and ¹⁸ F. That is, the apparatus according to the first embodiment is a PET mammography apparatus.

The transmission data collection unit 18 uses the radiation detection signals output from both the first and second γ-ray detectors 1 and 2 as a result of the radiation correction to the subject m by the external radiation source 4 for absorption correction. Collect as transmission data.
The absorption correction unit 19 corrects the absorption of the emission data collected by the emission data collection unit 17 using the transmission data collected by the transmission data collection unit 18.

The RI distribution image acquisition unit 20 performs reconstruction processing based on the transport position data, the vertical position data, the rotation angle data, and the like for both the first and second γ-ray detectors 1 and 2 in addition to the absorption data subjected to the absorption correction. To obtain a tomographic-type RI distribution image and a planar-image type RI distribution image. The display monitor 21 displays the RI distribution image acquired by the RI distribution image acquisition unit 20 on the screen.
The main control unit 23 is mainly composed of a computer and its operation program, and sends commands and data to each unit in accordance with the commands input from the operation unit 22 and the progress of photographing, thereby normalizing the apparatus. To play a role.

  In addition, as shown in FIG. 3, the apparatus of the first embodiment is configured so that the γ-ray detection mechanism 3 including both the first and second γ-ray detectors 1 and 2 is in contact with and away from the subject m. A detection system contact / separation moving mechanism 24 to be moved is provided. Specifically, as shown in FIG. 3, the detection system contact / separation moving mechanism 24 includes an electric motor 24 </ b> A installed on the detection system attachment member 13 and a bar screw 24 </ b> B rotated by the electric motor 24 </ b> A for each γ-ray detector 1. , 2, and the locking portions 1 a and 2 a of the γ-ray detectors 1 and 2 are screwed into the rod screws 24 B, and the rod screws 24 B rotate to lock the locking portions 1 a and 2 a. Along with moving along each rod screw 24B, both γ-ray detectors 1 and 2 move forward in the same direction at the same distance, or conversely, both γ-ray detectors 1 and 2 move away at the same distance at the same time. It is configured to retreat.

  When performing breast cancer screening using the apparatus of the first embodiment, the first and second γ-ray detectors 1 and 2 are retracted in the direction away from each other, as shown in FIG. After setting both the second γ-ray detectors 1 and 2 to face each other with the breast region ma of the subject m in between, the detection system contact / separation moving mechanism 24 is operated to connect both the γ-ray detectors 1 and 2. Advancing in a direction approaching the subject m. When the first and second γ-ray detectors 1 and 2 are brought close to the subject m, the detection range of γ-rays expands, and the γ-rays of the γ-ray detection mechanism 3 that substantially consists of the γ-ray detectors 1 and 2. Detection sensitivity increases.

The detection system contact / separation moving mechanism 24 moves the γ-ray detection mechanism 3 while receiving proximity control data according to an operator's operation or a preset program from the proximity movement control unit 25, and the proximity movement control unit 25 Proximity control data is sent as position variation data of the γ-ray detection mechanism 3.
In the case of the apparatus of the first embodiment, the movement of the γ-ray detection mechanism 3 by the detection system contact / separation movement mechanism 24 is electric, but the movement of the γ-ray detection mechanism 3 by the detection system contact / separation movement mechanism 24 is manually performed. It may be.

As described in detail above, in the case of the apparatus of Example 1, the γ-ray detection mechanism 3 that detects γ-rays generated by the radioisotope that has been administered to the subject m and arrived at the breast region ma is moved in and out of the detection system. Since the mechanism 24 is moved in the direction approaching the subject m to be brought close to the breast region ma of the subject m, the amount of γ rays detected by the γ ray detection mechanism 3 increases and the γ ray detection mechanism 3 Γ-ray detection sensitivity increases.
Therefore, according to the mammography apparatus of the first embodiment, an RI distribution image of the breast region ma of the subject m can be captured with sufficient sensitivity.

  In the case of the apparatus of the first embodiment, the position and orientation of the γ-ray detection mechanism 3 with respect to the mechanical origin of the apparatus are determined by the transfer position data sent from the transfer control unit 14 and the vertical position sent from the elevation control unit 15. It is determined according to the data, the rotation angle data sent from the rotation control unit 16, and the position variation data sent from the proximity movement control unit 25.

  That is, in the apparatus according to the first embodiment, since the imaging proceeds while the position and orientation of the γ-ray detection mechanism 3 with respect to the mechanical origin of the apparatus are changed, γ-ray detection with respect to the mechanical origin of the apparatus will be described below. A reconstruction algorithm when the position and orientation of the mechanism 3 change will be described.

  As shown in FIGS. 6 and 7, each of the first and second γ-ray detectors 1 and 2 constituting the γ-ray detection mechanism 3 is an assembly of minute γ-ray detection elements a and b. An image reconstruction area S having a center coordinate OC defined by a vector VC starting from the mechanical origin OM of the apparatus is set between the γ-ray detectors 1 and 2. Vectors VA and VB from the mechanical origin OM of the apparatus to the center coordinates OA and OB of the respective γ-ray detectors 1 and 2 are obtained based on the above-described transport position data, rotation angle data, and position variation data. The vectors WA and WB from the center coordinates WA and WB of the γ-ray detectors 1 and 2 to the γ-ray detection elements a and b are based on the addresses (coordinates) of the γ-ray detection elements a and b in the γ-ray detectors 1 and 2. Is required.

Accordingly, when a phenomenon occurs in which γ rays emitted from the subject m are simultaneously counted (hereinafter abbreviated as “event” as appropriate), a γ ray detecting element a that simultaneously detects γ rays from the mechanical origin OM of the apparatus. , B, the vectors uA and uB are also obtained according to the following equations (1) and (2).
uA = VA + WA (1)
uB = VB + WB (2)

On the other hand, when a phenomenon (event) in which γ rays emitted from the subject m are simultaneously counted occurs, address pair data of the γ ray detection elements a and b that detect γ rays, and γ that detects γ rays. Address pair data of vectors uA and uB for the line detection elements a and b are collected and stored as list mode type data for each event.
On the other hand, a straight line LOR (Line of Response) connecting γ-ray detection elements a and b that simultaneously detect γ-rays is obtained for each event from address pair data of vectors uA and uB collected and stored as list mode type data. The positron emitting species is above the straight line LOR.

The vector uA is obtained according to the following equation (3) and information on the position and orientation of the γ-ray detectors 1 and 2 as the γ-ray detection mechanism 3 stored as list mode type data. The position and orientation data of the γ-ray detectors 1 and 2 may be stored as tag information only when there is a change.
uA = R _X , R _Y , R _Z , T, WA (3)
However, as shown below, R _X , R _Y , R _Z are rotations of the γ-ray detectors 1, 2 around the X, Y, and Z axes orthogonal to each other with the mechanical origin OM of the apparatus as the origin, T Is the position in each direction of the X axis, Y axis, and Z axis (ie, VA).
Further, the vector uB can be obtained in the same manner as the vector uA.

  In this way, when a straight line LOR (Line of Response) connecting γ-ray detection elements a and b that simultaneously detect γ-rays is obtained for each event, a successive approximation list mode reconstruction algorithm is applied [ For example, see J Reader et al 1998 Phys. Med Bial. 43 835-846 (non-patent literature). The image update formula of this list mode reconstruction algorithm is as shown in formula (4). The RI distribution image is obtained by repeating the updating formula (4).

Here, f ^k _j is the pixel value of the pixel j in the k-th iteration, a _ij is the probability that the γ-ray emitted from the pixel j is detected by LORi, M is the number of measured events, and I is the main imaging condition It is the number of all LORs in (detector arrangement).
Note that the update formula used in the image reconstruction algorithm applied to the apparatus of the first embodiment is not limited to the formula (4).

Further, in the case of the apparatus according to the first embodiment, the center coordinate OC of the image reconstruction area S is set to the midpoint between the first and second γ-ray detectors 1 and 2. Since the γ-ray detection mechanism 3 only rotates about one axis of the Xa axis, β = 0 and γ = 0. As a result, R _Y and R _Z in the equation (3) are In either case, the following equation (5) is obtained.

Next, a second embodiment of the mammography apparatus of the present invention will be described with reference to the drawings. FIG. 8 is a front view showing a configuration around the γ-ray detection mechanism of the PET mammography apparatus according to the second embodiment, and FIG. 9 is a perspective view showing a breast cancer screening situation by the apparatus of the second embodiment.
In the mammography apparatus of the second embodiment, as shown in FIGS. 8 and 9, first to fourth four γ-ray detectors 27 to 30 surrounding the breast region ma of the subject m are administered to the subject m. Since the apparatus is the same as that of the first embodiment except that the γ-ray detection mechanism 26 for detecting γ-rays generated by the radioisotope (RI) that has arrived at the breast region ma is used, only the differences are described. A description of common points will be omitted.

  Each of the first to fourth γ-ray detectors 27 to 30 has a shape in which a cylinder is vertically divided into four equal parts, and each γ-ray detector 27 to 30 has a shape as indicated by an arrow in FIG. When the γ-ray detectors 27 to 30 are moved to the position closest to the subject m, as shown by the solid lines in FIG. As shown in FIG. 9, the entire γ-ray detection mechanism 26 has a cylindrical shape.

  Therefore, the apparatus according to the second embodiment has a detection system contact / separation moving mechanism 31 that moves the γ-ray detection mechanism 26 including the first to fourth γ-ray detectors 27 to 30 in a direction in which the γ-ray detection mechanism 26 is in contact with and away from the subject m. It has. Specifically, as shown in FIG. 8, the detection system contact / separation moving mechanism 31 includes an electric motor 31A installed on the detection system attachment member 13 and a bar screw 31B rotated by the electric motor 31A. The locking portions 27a to 30a of the γ-ray detectors 27 to 30 are screwed into the rod screws 31B, and the rod screws 31B are rotated by the rotation of the electric motor 31A. As the stop portions 27a to 30a move along the respective rod screws 31B, all the γ-ray detectors 27 to 30 simultaneously move toward the same distance, or conversely, all the γ-ray detectors 27 to 30 move. At the same time, it is configured to move away from each other by an equal distance.

  When breast cancer is screened by the apparatus of Example 2, the first to fourth γ-ray detectors 27 to 30 are moved away from each other as shown by the one-dot chain line in FIG. After the detection mechanism 26 is applied to the breast area ma of the subject m, all the γ-ray detectors 27 to 30 are moved toward the subject m, and an RI distribution image is taken as close as possible.

  FIG. 10 is a front view illustrating the movement of the γ-ray detector of the mammography apparatus according to the modification of the second embodiment. In the second embodiment, the γ-ray detectors 27 to 30 interfere with each other when the γ-ray detectors 27 to 30 are brought closer to the subject m (breast region), so the state shown by the solid line in FIG. The subject cannot be closer than the (cylindrical state). On the other hand, in the modified example shown in FIG. 10, in addition to the detection system approaching / separating mechanism for moving the γ-ray detectors 27 to 30 in the direction of approaching / separating from the subject (breast region), γ-rays are used. A detection system slide moving mechanism (not shown) that moves the detectors 27 to 30 in a direction orthogonal to the contact / separation direction when viewed from the front is provided. The detection system slide movement mechanism is, for example, a detection system contact / separation movement mechanism in which the detection system contact / separation movement mechanism 31 shown in FIG. 8 is mounted on a base plate, and the base plate is disposed in a direction orthogonal to the contact / separation direction. It can be easily realized by driving with a screw feed mechanism similar to 31. By configuring in this way, as shown in FIG. 10B from the cylindrical state of FIG. 10A, the γ-ray detectors 27 to 30 are avoided while avoiding mutual interference of the γ-ray detectors 27 to 30. The subject can be brought closer to the subject.

  Next, a third embodiment of the mammography apparatus of the present invention will be described with reference to the drawings. FIG. 11 is a front view showing the configuration around the γ-ray detection mechanism of the PET mammography apparatus according to the third embodiment, and FIG. 12 is a perspective view showing a breast cancer screening situation by the apparatus of the third embodiment.

  In the mammography apparatus of the third embodiment, as shown in FIG. 11 and FIG. 12, a concave γ-ray detector 33 that receives the breast region ma of the subject m in the prone posture and the back of the breast region of the breast region ma of the subject m. The flat γ-ray detector 34 facing each other constitutes a γ-ray detection mechanism 32 that detects γ-rays generated by the radioisotope (RI) that is administered to the subject m and arrives at the breast region ma, Since the configuration is substantially the same as that of the apparatus of the first embodiment, only different points will be described, and description of common points will be omitted.

  As shown in FIG. 12, the bed BD on which the subject m rides on his / her face when undergoing breast cancer screening is discontinuous at the portion corresponding to the breast region ma of the subject m, and is between the gaps in the bed BD. The concave γ-ray detector 33 is fixed, and when the subject m is lying on the bed BD, the breast region ma of the subject m is naturally fitted into the concave γ-ray detector 33 and received. .

  On the other hand, the flat γ-ray detector 34 constituting the upper part of the γ-ray detection mechanism 32 is positioned above the concave γ-ray detector 33 by an inverted L-shaped support arm 35 whose base end is fixed to the bed BD. It is installed on the lower end side of the detection system holding rod 36 that is held vertically, and is movable in a direction in which it is in contact with and away from the subject m. Therefore, the apparatus according to the third embodiment includes the detection system contact / separation moving mechanism 37 that moves the flat γ-ray detector 34, which is an upper part of the γ-ray detection mechanism 32, in a direction in which the flat γ-ray detector 34 is in contact with and away from the subject m. .

  Specifically, as shown in FIG. 11, the detection system holding rod 36 includes a cylindrical outer rod 36A and an inner rod 36B, and the inner rod 36B is inserted into the outer rod 36A so as to be movable in the vertical direction. Yes. The outer rod 36A is attached to the inverted L-shaped support arm 35, and the flat γ-ray detector 34 is attached to the lower end of the inner rod 36B. The detection system contact / separation moving mechanism 37 includes a rack 37A installed on the inner rod 36B side, a pinion 37B installed on the outer rod 36A side, and an electric motor 37C. By the rotation of the electric motor 37C, When the rack 37A meshing with the pinion 37B moves as the pinion 37B rotates, the inner rod 36B moves up or down, and the flat γ-ray detector 34 approaches or separates from the subject m. .

When performing breast cancer screening using the apparatus of Example 3, the flat γ-ray detector 34 is moved upward, the subject m is placed on the bed BD in a lying position, and then the flat γ-ray detector 34 is moved. The RI distribution image is taken after moving down and approaching the subject m.
In addition, if the dent suitable for the shape of the subject m is formed on the surface of the bed BD, the stability of the subject m placed on the bed BD is lowered.

The present invention is not limited to the above embodiment, and can be modified as follows.
(1) Although the apparatuses of Examples 1 to 3 are PET mammography apparatuses, the present invention can also be applied to systems other than PET, such as the SPECT system.

  (2) The apparatus according to the first embodiment is a ceiling traveling type in which the γ-ray detection mechanism 3 is conveyed along a rail member disposed on the ceiling. However, in the present invention, the γ-ray detection mechanism 3 is placed on the floor. The present invention can also be applied to a floor traveling type that is transported along a rail member that is disposed.

  (3) In the case of the apparatus of the first embodiment, the position and orientation of the γ-ray detection mechanism 3 is transport position data sent from the transport control unit 14, vertical position data sent from the elevation control unit 15, and rotation control unit 16 is determined in accordance with the rotation angle data sent from 16 and the position variation data sent from the proximity movement control unit 25. The position and orientation of the γ-ray detection mechanism 3 are determined by a magnetic sensor or an optical sensor. The structure which utilizes and measures may be sufficient.

When using a magnetic sensor, for example, a transmitter that transmits radio waves in three orthogonal directions is attached to the γ-ray detection mechanism 3, and one receiver is disposed at each of three locations on the floor side. The configuration is such that the position and orientation of the γ-ray detection mechanism 3 are obtained in accordance with reception signals output from three receivers.
When using an optical sensor, for example, a mark piece is attached to the γ-ray detection mechanism 3, optical cameras are arranged at three locations on the floor side, and a first signal is output according to video signals output from the three optical cameras. The positions and orientations of the second gamma ray detectors 1 and 2 are determined.

1 is a block diagram illustrating a configuration of a PET mammography apparatus according to Embodiment 1. FIG. It is a side view which shows the structure around the gamma ray detection mechanism of the apparatus of Example 1. FIG. It is a front view which shows the structure around the gamma ray detection mechanism of the apparatus of Example 1. FIG. It is a perspective view which shows the breast cancer screening situation by the apparatus of Example 1. FIG. It is a perspective view which shows another breast cancer examination situation by the apparatus of Example 1. FIG. FIG. 3 is a schematic diagram illustrating an arrangement relationship between first and second γ-ray detectors and an image reconstruction area in the apparatus according to the first embodiment. 3 is a graph showing a coordinate system of both the first and second γ-ray detectors and the image reconstruction area in the apparatus of Example 1; 6 is a front view showing a configuration around a γ-ray detection mechanism of the mammography apparatus of Embodiment 2. FIG. It is a perspective view which shows the breast cancer screening situation by the apparatus of Example 2. FIG. FIG. 10 is a front view showing the movement of a γ-ray detector of a mammography apparatus according to a modification of Example 2. FIG. 6 is a front view illustrating a configuration around a γ-ray detection mechanism of a mammography apparatus according to a third embodiment. It is a perspective view which shows the breast cancer screening situation by the apparatus of Example 3. FIG. It is a front view which shows the structural example of the gantry of the conventional PET apparatus. It is an elevational view showing a configuration example of a gantry of a conventional PET apparatus. It is an elevation view which shows the other structural example of the gantry of the conventional PET apparatus.

Explanation of symbols

1 ... 1st gamma ray detector (gamma ray detector)
2 ... Second γ-ray detector (γ-ray detector)
3 ... γ-ray detection mechanism (γ-ray detection means)
17 ... Emission data collection unit (Emission data collection means)
20 ... RI distribution image acquisition unit (RI distribution image acquisition means)
24 ... Detection system contact / separation movement mechanism (detection system contact / separation movement means)
26 ... γ-ray detection mechanism (γ-ray detection means)
27 ... 1st γ-ray detector 28 ... 2nd γ-ray detector 29 ... 3rd γ-ray detector 30 ... 4th γ-ray detector 31 ... Detection system contact / separation movement mechanism (detection system contact / separation movement means)
32 .gamma. Ray detection mechanism (gamma ray detection means)
33 ... concave γ-ray detector 34 ... flat γ-ray detector 37 ... detection system contact / separation movement mechanism (detection system contact / separation movement means)
m ... subject ma ... breast area

Claims (6)

  (A) γ-ray detection means for detecting γ-rays generated by radioisotopes that have been administered to the subject and arrived at the breast region; and (B) at least a part of the γ-ray detection means is in contact with or separated from the subject. (C) an emission data collecting means for collecting a γ-ray detection signal output from the γ-ray detection means as emission data for acquiring an RI distribution image; and (D) an emission. A mammography apparatus comprising RI distribution image acquisition means for acquiring an RI distribution image based on emission data collected by the data collection means.   2. The mammography apparatus according to claim 1, wherein the radioisotope administered to the subject is a positron-type radioisotope, and the emission data collection means causes the annihilation gamma rays traveling in the opposite direction to be simultaneously produced by the gamma ray detection means. A mammography device that collects only γ-ray detection signals at the time of detection as emission data.   3. The mammography apparatus according to claim 1, wherein the γ-ray detection means includes a first γ-ray detector and a second γ-ray detector facing each other with the breast region of the subject therebetween, and a detection system contact / separation moving means. Is a mammography apparatus for moving the first and second γ-ray detectors.   3. The mammography apparatus according to claim 1, wherein the γ-ray detection means includes a plurality of γ-ray detectors surrounding the breast region of the subject, and the detection system contact / separation moving means includes all γ-ray detectors. Mammography device that moves the camera.   5. The mammography apparatus according to claim 4, further comprising a detection system slide moving means for moving a plurality of γ-ray detectors in a direction orthogonal to a direction in which the γ-ray detector is in contact with and away from the subject. 3. The mammography apparatus according to claim 1, wherein the γ-ray detection means includes a concave γ-ray detector that receives the breast region of the subject in a prone posture, and a flat γ-ray detector that faces the back of the breast region of the subject. A mammography apparatus in which the detection system contact / separation moving means moves the flat γ-ray detector.

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