JP6537906B2 - Planar imaging device - Google Patents

Description

  The present invention relates to a planar imaging device.

  There are SPECT devices, PET devices, and planar imaging devices as devices capable of acquiring an image of the radioactivity concentration distribution in the measurement object (living body).

  A single photon emission computed tomography (SPECT) device detects gamma rays generated by a measurement object to which a single photon emission type radiopharmaceutical (SPECT radiopharmaceutical) is administered by a gamma ray detector rotated around the measurement object. The SPECT device comprises one or more detectors, which can be rotated like an X-ray CT device to acquire tomographic images.

  A PET (positron emission tomography) apparatus detects gamma rays generated in a measurement object to which a positron-emitting radioactive drug (PET radiopharmaceutical) is administered, by a large number of gamma ray detectors arranged around the measurement object. The PET apparatus can acquire a tomographic image without rotating the detector. Patent Document 1 discloses an invention for controlling the administration of a radioactive drug in a measurement object in a PET device.

  The planar imaging apparatus detects gamma rays generated in a measurement object to which a positron-emitting radioactive drug (PET radioactive drug) is administered, by a pair of gamma ray detector arrays disposed opposite to each other across the measurement object. The planar imaging device can acquire not a tomographic image but a projection image.

  The planar imaging device can measure and observe in real time the radiation distribution of a radioactive drug having a positron-emitting nuclide administered to the inside of a living body (animal, plant) to be measured. Since the planar imaging device measures a two-dimensional projection image by arranging a pair of detector arrays in which a plurality of photomultipliers are arranged as a gamma ray detector, the number of photomultipliers in each detector array The measurement area can be easily widened by changing. Therefore, the planar imaging apparatus is capable of high throughput measurement capable of measuring a plurality of living bodies simultaneously.

Patent No. 4408162

  The SPECT device needs a collimator (shielded slit plate) in front of the detector to limit the incident direction of photons (gamma rays) to the light receiving surface of the detector in a substantially vertical direction, so the mechanism becomes heavy Cheap. Moreover, SPECT radiopharmaceuticals are preferable in that they have a long physical half life and are easy to handle. It is difficult and its application range to living body is narrow.

  PET devices use PET radiopharmaceuticals as well as planar imaging devices. Although PET radiopharmaceuticals have short physical half-lives and are difficult to handle, they can be introduced into various biomolecules because they contain carbon equivalent to the atoms that constitute biomolecules and fluorine close to them, etc. The range is wide. However, the PET apparatus is large in size and expensive because it is necessary to dispose a large number of detectors around the entire circumference of a living body.

  The planar imaging apparatus can capture a two-dimensional projection image of a measurement object, but can not capture a three-dimensional tomographic image. In addition, in planar imaging devices, PET radiopharmaceuticals with short physical half-lives are used, and there are many types of PET radiopharmaceuticals that have the property of being excreted from the living body by metabolism etc. Since the three-dimensional distribution of the activity concentration of the radiation changes every moment, the accuracy of the tomographic image is low even if the tomographic image of the object to be measured can be taken.

  The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a planar imaging device capable of acquiring a high-precision tomographic image.

  The planar imaging apparatus according to the present invention comprises: (1) a first detector array and a second detector array each having a plurality of gamma ray detectors arranged, wherein the first detector array and the second detector array are measured A detection unit which is disposed opposite to each other with a space interposed therebetween and which is rotatable about a predetermined axis passing through the measurement space, and (2) a drug administration unit which administers a radiopharmaceutical to the measurement object arranged in the measurement space And (3) a control unit that controls the operation of each of the detection unit and the drug administration unit.

  In the planar imaging device of the present invention, the control unit (a) arranges the detection unit in a predetermined orientation, and acquires the value of the radioactivity concentration of the monitor area in the measurement object in the planar projection image obtained by the detection unit. In addition, the administration of the radioactive drug to the object to be measured by the drug administration unit is controlled, and (b) when the temporal change of the obtained radioactivity concentration becomes equilibrium (hereinafter referred to as "primary equilibrium"), The rate of administration of the radioactive drug to the measurement object by the unit is constant, and the detection unit is arranged in each of a plurality of orientations around a predetermined axis while maintaining primary equilibrium over the first period, and measurement data by the detection unit And (c) based on the measurement data collected in the first period, create a tomographic image of the radioactivity concentration distribution in the measurement object.

  In addition, the control unit arranges the detection unit in a predetermined orientation after the (d) first period, and the measurement object in the planar projection image obtained by the detection unit with respect to the measurement object to which the evaluation target drug is administered. When the value of radioactivity concentration in the monitor area is acquired and (e) the temporal change of the acquired radioactivity concentration becomes equilibrium (hereinafter referred to as "secondary equilibrium"), secondary equilibrium is determined over the second period. In the maintained state, the detection unit is arranged in each of a plurality of orientations around a predetermined axis to collect measurement data by the detection unit, and (f) radioactivity in the measurement object based on the measurement data collected in the second period It is preferable to create a tomographic image of the concentration distribution.

  In addition, the control unit determines the time required for the change of state from the primary equilibrium to the secondary equilibrium by administration of the drug to be evaluated, the difference in the radioactivity concentration in the monitoring area in each of the primary equilibrium and the secondary equilibrium, or It is preferable to evaluate the effect of the evaluation target drug administered to the measurement object based on the tomographic image of the radioactivity concentration distribution in the measurement object in each of the period and the second period.

  When the control unit arranges the detection units in each of a plurality of orientations around a predetermined axis and collects measurement data by the detection unit, it is preferable that the data be collected over a predetermined time in each of the plurality of orientations. . Moreover, it is also preferable that the control unit makes the time for collecting measurement data different for each of a plurality of azimuths so as to equalize the statistical accuracy of the measurement data of each azimuth. In addition, it is also preferable that the control unit sets the azimuth in each direction by repeatedly swinging the detection unit around a predetermined axis to equalize statistical accuracy of measurement data of each azimuth.

  The planar imaging device of the present invention can acquire a tomographic image with high accuracy.

FIG. 1 is a diagram showing the configuration of a planar imaging device 1 of the present embodiment. FIG. 2 is a view for explaining the rotation of the detection unit 10 of the planar imaging device 1 of the present embodiment. FIG. 3 is a diagram for explaining a first operation example of the detection unit 10 in the 3D measurement mode in the planar imaging device 1 of the present embodiment. FIG. 4 is a diagram for explaining a second operation example of the detection unit 10 in the 3D measurement mode in the planar imaging device 1 of the present embodiment. FIG. 5 is a diagram for explaining a third operation example of the detection unit 10 in the 3D measurement mode in the planar imaging device 1 of the present embodiment. FIG. 6 is a view for explaining a display example on the display unit 40 in the 3D measurement mode of the planar imaging device 1 of the present embodiment. FIG. 7 is a view for explaining a setting method of the monitor area in the measurement object 90 in the planar imaging device 1 of the present embodiment. FIG. 8 is a view showing a graph display example of the change of radioactivity concentration with time in the monitor area in the display unit 40 of the planar imaging device 1 of the present embodiment. FIG. 9 is a diagram for explaining control by the control unit 30 of the planar imaging device 1 of the present embodiment. FIG. 10 is a diagram for explaining a first method of obtaining control parameters used in control by the control unit 30 of the planar imaging device 1 of the present embodiment. FIG. 11 is a diagram for explaining a first method of obtaining control parameters used in control by the control unit 30 of the planar imaging device 1 of the present embodiment. FIG. 12 is a diagram for explaining a second method of obtaining control parameters used in control by the control unit 30 of the planar imaging device 1 of the present embodiment. FIG. 13 is a diagram for explaining a second method of obtaining control parameters used in control by the control unit 30 of the planar imaging device 1 of the present embodiment. FIG. 14 is a diagram for explaining a second method of obtaining control parameters used in control by the control unit 30 of the planar imaging device 1 of the present embodiment. FIG. 15 is a diagram for explaining a second method of obtaining control parameters used in control by the control unit 30 of the planar imaging device 1 of the present embodiment. FIG. 16 is a diagram for explaining a second method of obtaining control parameters used in control by the control unit 30 of the planar imaging device 1 of the present embodiment. FIG. 17 is a diagram for explaining a second method of obtaining control parameters used in control by the control unit 30 of the planar imaging device 1 of the present embodiment. FIG. 18 is a diagram for explaining the method of determining the balance of the radioactive concentration in the monitor area by the control unit 30 of the planar imaging device 1 of the present embodiment. FIG. 19 is a diagram for explaining the method of determining the balance of the radioactive concentration in the monitor area by the control unit 30 of the planar imaging device 1 of the present embodiment. FIG. 20 shows bolus dose response characteristics (BolusTAC) in the first embodiment. FIG. 21 shows time change of radioactive drug administration (Injection) in the first example, model response TAC (Bolus TAC) to bolus administration, model response TAC (Infusion TAC) to continuous administration, and a model response TAC of the sum thereof. It is a figure which shows (Bolus + Infusion TAC). FIG. 22 is a diagram showing the time change of the radioactive concentration in the monitor area measured in the first embodiment. FIG. 23 is a graph showing the temporal change of the radioactive concentration of the target portion of the cylindrical phantom in the second embodiment. FIGS. 24A and 24B are tomographic images of a cylindrical phantom obtained in the second embodiment. FIG. 25 is a view showing temporal changes in activity concentration of the target portion of the cylindrical phantom and the whole in the third embodiment. FIG. 26 is a tomographic image of a cylindrical phantom obtained in the third embodiment. FIGS. 27 (a) and 27 (b) are tomographic images of the cylindrical phantom obtained in the third embodiment. FIGS. 28 (a) and 28 (b) are tomographic images of the cylindrical phantom obtained in the third embodiment. FIG. 29 is a diagram showing the time change of the radioactivity concentration in the monitor area in the comparative example. FIG. 30A is a tomographic image created based on measurement data collected in the 3D measurement mode in each of the first period and the second period in the comparative example. FIG. 31 is a graph of quantitative values of brain radioactivity concentration obtained from tomographic images of the first period and the second period in the comparative example. FIG. 32 is a diagram showing the time change of the radioactive concentration in the monitor area in the fourth embodiment. FIG. 33A is a tomographic image created based on measurement data collected in the 3D measurement mode in each of the first period and the second period in the fourth embodiment. FIG. 34 is a graph of quantitative values of brain radioactivity concentration obtained from tomographic images of the first period and the second period in the fourth example.

  Hereinafter, with reference to the accompanying drawings, modes for carrying out the present invention will be described in detail. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. The present invention is not limited to these exemplifications, is shown by the claims, and is intended to include all modifications within the scope and meaning equivalent to the claims.

  FIG. 1 is a diagram showing the configuration of a planar imaging device 1 of the present embodiment. The planar imaging apparatus 1 includes a detection unit 10, a drug administration unit 20, a control unit 30, and a display unit 40. The detection unit 10 includes a first detector array 11 and a second detector array 12. Each of the first detector array 11 and the second detector array 12 has a plurality of gamma ray detectors arranged. The first detector array 11 and the second detector array 12 are disposed opposite to each other across the measurement space in which the measurement object 90 is disposed, and are rotatable around a predetermined axis Ax passing through the measurement space .

  The drug administration unit 20 is connected to a syringe inserted into the vein of the measurement object 90, and administers a positron-emitting radioactive drug (PET radioactive drug) to the measurement object 90 via the syringe. The display unit 40 can perform display of various data measured by the detection unit 10, display of a graph of temporal change of radioactivity concentration, display of a projection image, display of a tomographic image, and the like.

  The control unit 30 controls the operation of each of the detection unit 10 and the drug administration unit 20. The control unit 30 can send a control signal for controlling the operation of the detection unit 10 to the detection unit 10 through the communication line provided between the detection unit 10 and the measurement unit 10. It can be received. Further, the control unit 30 can send a control signal to the drug administration unit 20 through a communication line provided between the control unit 30 and the drug administration unit 20. The control unit 30 can instruct start and stop of the drug administration by sending a control signal to the drug administration unit 20, and can also instruct change of the drug dose or the drug administration rate. The drug administration unit 20 can start and stop the drug administration according to the control signal received from the control unit 30, and can change the drug dose or the drug administration rate.

  The control unit 30 arranges the detection unit 10 in a predetermined orientation, and acquires the value of the radioactivity concentration of the monitor area in the measurement object 90 in the planar projection image obtained by the detection unit 10. The administration of the radiopharmaceutical to the measurement object 90 is controlled. When the temporal change of the acquired radioactivity concentration is in equilibrium (primary equilibrium), the control unit 30 subsequently makes the dose rate of the radioactive drug to the measurement object 90 by the drug administration unit 20 constant, for the first period. The detection unit 10 is arranged in each of a plurality of orientations around a predetermined axis while maintaining primary balance over all, and measurement data by the detection unit 10 is collected.

  In addition, after the first period, the control unit 30 arranges the detection unit 10 in a predetermined orientation, and the measurement object 90 in the planar projection image obtained by the detection unit 10 for the measurement object 90 to which the evaluation target drug is administered. Acquire the value of radioactivity concentration in the monitor area in the middle. When the temporal change of the acquired activity concentration is in equilibrium (secondary equilibrium), the control unit 30 maintains a plurality of detection units 10 around a predetermined axis in a state where the secondary equilibrium is maintained for the second period. It arrange | positions to each azimuth | direction, and the measurement data by the detection part 10 are collected.

  The control unit 30 creates a tomographic image of the radioactivity concentration distribution in the measurement object 90 based on the measurement data collected in the first period, and the radioactivity in the measurement object 90 based on the measurement data collected in the second period Create tomographic images of concentration distribution. In addition, the control unit 30 determines the time required for the state change from the primary equilibrium to the secondary equilibrium due to the administration of the drug to be evaluated, the difference in the radioactivity concentration in the monitor area in each of the primary equilibrium and the secondary equilibrium, or The effects of the evaluation target drug administered to the measurement object 90 are evaluated based on the tomographic images of the radiation concentration distribution in the measurement object 90 in each of the first and second periods.

  The planar imaging apparatus 1 of the present embodiment confirms that the radioactivity concentration of the monitor area in the measurement object 90 in the planar projection image obtained by the detection unit 10 has become equilibrium (primary equilibrium or secondary equilibrium). Later, the detection unit 10 is arranged in each of a plurality of orientations around a predetermined axis while maintaining its equilibrium, and measurement data by the detection unit 10 is collected, so that a high-precision tomographic based on the collected measurement data. Images can be acquired. Further, the planar imaging apparatus 1 of the present embodiment can evaluate the effect of the evaluation target drug administered to the measurement object 90 with high accuracy.

  Hereinafter, the planar imaging device 1 of the present embodiment will be described in more detail.

  FIG. 2 is a view for explaining the rotation of the detection unit 10 of the planar imaging device 1 of the present embodiment. The detection unit 10 is pivotable about a predetermined axis Ax passing through the measurement space in which the measurement object 90 is disposed, and may be disposed in any orientation about the predetermined axis Ax. In the arrangement of FIG. 7B, the detection unit 10 is inclined by 45 ° with respect to the arrangement of FIG. The detection unit 10 is further inclined by 45 ° in the arrangement of FIG.

  The planar imaging apparatus 1 arranges the detection unit 10 in a predetermined direction (for example, the detector arrays 11 and 12 in the vertical direction as shown in FIG. 6A) and collects the measurement data to obtain the collected measurement data. A two-dimensional projection image can be acquired based on it. Hereinafter, this measurement mode is referred to as "planar measurement mode". In the planar measurement mode, although a planar projection image of the measurement object 90 can be acquired, information in the depth direction can not be acquired.

  The planar imaging apparatus 1 arranges the detection unit 10 in each of a plurality of azimuths around the predetermined axis Ax and collects measurement data, thereby acquiring a three-dimensional tomographic image based on the acquired measurement data of each azimuth. can do. Below, this measurement mode is called "3D measurement mode."

  FIGS. 3-5 is a figure explaining the operation example of the detection part 10 at the time of 3D measurement mode in the planar imaging device 1 of this embodiment. In these figures, a graph of the time change of the activity concentration of the monitor area in the measurement object 90 to which the radiopharmaceutical is administered is shown, and the orientation of the detection unit 10 in each period is illustrated. . Further, in these graphs, the solid line represents the measured value of the radioactivity concentration, and the broken line represents the estimated value of the radioactivity concentration.

In the first operation example shown in FIG. 3, in the 3D measurement mode in which the detection unit 10 is arranged in each of a plurality of azimuths around the predetermined axis Ax and the measurement data by the detection unit 10 is collected, Data are collected for a fixed time in each of a plurality of orientations. Period _t 0 in ~t ₁ is planar measurement of the measurement mode is performed, measurements are taken of the time period _t 1 ~t ₅ in 3D measurement mode, the measurement time period _t 5 ~t ₆ in planar measurement mode is performed. In the planar measurement mode, the detection unit 10 is disposed in a predetermined direction (the detector arrays 11 and 12 in the vertical direction).

Of period _t 1 ~t ₅ to measure the 3D measurement mode is performed, the detection unit 10 in the period _t 1 ~t ₂ is disposed (the same orientation as the planar measurement mode) azimuth 0 °, the period _t 2 ~t _{In 3} , the detection unit 10 is disposed at an azimuth angle of 45 °, the detection unit 10 is disposed at an azimuth angle of 90 ° in a period t _{3 to} t ₄ , and the detection unit 10 is disposed at an azimuth angle 135 ° in a period t _{4 to} t ₅ Be done. Each of the period t _{1 to} t ₂ , the period t _{2 to} t ₃ , the period t _{3 to} t ₄ and the period t _{4 to} t ₅ is set as a preset constant time. The 3D measurement mode, it is not possible to measure the time variation of the activity concentration in the measurement object 90, after all by 3D measurement mode measurement of azimuth ended, the period t ₅ ~t ₆ again, planar measurement Mode measurement is performed to interpolate and estimate the change in radioactivity concentration over time in the 3D measurement mode.

In the second operation example shown in FIG. 4, in the 3D measurement mode in which the detection unit 10 is arranged in each of a plurality of azimuths around the predetermined axis Ax and the measurement data by the detection unit 10 is collected, The statistical accuracy of the measurement data of each azimuth is made uniform by varying the time for collecting the measurement data in each of the plurality of azimuths. As compared with the first operation example, in the second operation example, the time is not constant for each of the periods t _{1 to} t ₂ , the periods t _{2 to} t ₃ , the periods t _{3 to} t ₄ and the periods t _{4 to} t ₅ The time of each period becomes longer as time passes from the start of measurement.

When setting the time of each period, extrapolation of the activity concentration time change obtained by the measurement of the planar measurement mode in the period t _{0 to} t ₁ to obtain the activity concentration time change prediction, and this activity concentration time change Based on the prediction and the physical half life of the radiopharmaceutical, it is possible to equalize the statistical accuracy of the measurement data of each orientation. In the 3D measurement mode, it is not possible to measure the time change of the radioactivity concentration in the measurement object 90. Therefore, after the measurement in all directions in the 3D measurement mode is finished, the measurement in the planar measurement mode is performed again.

In the third operation example shown in FIG. 5, in the 3D measurement mode in which the detection unit 10 is arranged in each of a plurality of azimuths around the predetermined axis Ax and the measurement data by the detection unit 10 is collected, The detection unit 10 is repeatedly rocked around the predetermined axis Ax to set each azimuth, and uniform the statistical accuracy of the measurement data of each azimuth. In the third operation example, the measurement in the planar measurement mode is performed in the period t _{0 to} t ₁ , and the measurement in the 3D measurement mode is performed in the period after time t ₁ . In the planar measurement mode, the detection unit 10 is disposed in a predetermined direction (the detector arrays 11 and 12 in the vertical direction).

Of the time _{t 1} after the period in which measurements of 3D measurement mode is performed, the detection unit 10 in the period _t 1 ~t ₂ is disposed (the same orientation as the planar measurement mode) azimuth 0 °, the period _t 2 ~t _{In 3} , the detection unit 10 is disposed at an azimuth angle of 45 °, in the period t _{3 to} t ₄ the detection unit 10 is disposed at an azimuth angle of 0 °, and in the period t _{4 to} t ₅ the detection unit 10 is at an azimuth angle of −45 ° In the period t _{5 to} t ₆ , the detection unit 10 is disposed at an azimuth angle of −90 °, and in the period t _{6 to} t ₇ , the detection unit 10 is disposed at an azimuth angle of −45 °, and in the period t _{7 to} t ₈ The detection unit 10 is disposed at an azimuth angle of 0 °. Thereby, statistical accuracy of measurement data of each direction can be made uniform.

In the 3D measurement mode, it is not possible to measure the time change of the radioactivity concentration in the measurement object 90, so the same azimuth angle 0 ° period (t _{1 to} t ₂ , t _{3 to} t ₄ , as in the planar measurement mode) The statistical accuracy of the measurement data of each direction can be estimated by using the time-dependent change in radioactivity concentration designated from the measurement data of t _{7 to} t ₈ ). After measurement in all directions in the 3D measurement mode is completed, measurement in the planar measurement mode is performed again.

FIG. 6 is a view for explaining a display example on the display unit 40 in the 3D measurement mode of the planar imaging device 1 of the present embodiment. FIG. 6 is a display example of periods t _{1 to} t _{2 in} the case of the third operation example shown in FIG. 5 (FIG. 6 (a)), and a display example of periods t _{2 to} t ₃ (FIG. 6 (b)) , and shows a display example of a time period _t 3 ~t ₄ (FIG. (c)). Further, in each of FIGS. 6A to 6C, a graph of the temporal change of the radioactivity concentration of the monitor area in the measurement object 90 to which the radioactive drug has been administered is shown. The azimuth angle etc. are shown. Also in this graph, the solid line represents the measured value of the radioactivity concentration, and the broken line represents the estimated value of the radioactivity concentration.

  In the figure (a), the display of "tomographic imaging is possible" shows that it is 3D measurement mode, and the display of "No. 1/4 x 1" is the first direction among the four directions of the detection unit 10. The first measurement is shown for (0 °), and the "1 min" indication indicates that the measurement data is collected for 1 minute at that azimuth angle. The display example of FIG. 6B shows that the first measurement is performed in the second direction (45 °), and measurement data is collected for one minute at the azimuth angle. The display example of FIG. 6C shows that the second measurement is performed at the first azimuth (0 °), and measurement data is collected for one minute at the azimuth. The display unit 40 can notify the operator of the timing of changing the direction of the detection unit 10 by displaying such information.

  FIG. 7 is a view for explaining a setting method of the monitor area in the measurement object 90 in the planar imaging device 1 of the present embodiment. As described above, the control unit 30 can send a control signal to the drug administration unit 20 through the communication line provided between the control unit 30 and the drug administration unit 20. The control signal sent from the control unit 30 to the drug administration unit 20 is determined based on the radioactivity concentration of the monitor area in the measurement object 90 in the plane projection image shown in FIG.

  The monitor area is set as follows. First, in the projection image acquired by measurement in the planar measurement mode, an approximate range including the area to be a monitor area (the range within the rectangular frame in the same figure (b)) is set, and pixels within the rectangular range Based on the average value, the maximum value, and the minimum value, thresholds for dividing the monitor area are determined. Then, in the rectangular range, an area whose pixel value is equal to or more than the threshold value is taken as a monitor area (an area within an elliptical frame in FIG. 6C). The pixel average value in the monitor area represents the radioactivity concentration. The time change of the radioactivity concentration is calculated in real time, and this is drawn as a graph on the display unit 40. The method of determining the control signal based on the radioactivity concentration of the monitor area will be described later. FIG. 8 is a view showing a graph display example of the change of radioactivity concentration with time in the monitor area in the display unit 40 of the planar imaging device 1 of the present embodiment.

  FIG. 9 is a diagram for explaining control by the control unit 30 of the planar imaging device 1 of the present embodiment. In the figure, the display unit 40 displays the time change of the drug administration rate (Infusion rate) IR to the measurement object 90 by the drug administration unit 20, the monitor area in the measurement object 90 measured in the planar measurement mode. The time change of the actual value Am of the radioactivity concentration and the expected activity concentration equilibrium level (Target level) TL of the monitor area are shown.

When administered to the measurement object 90 by the medication unit 20 a radiopharmaceutical from time t ₀ at a preset initial dose rate is expected radioactive concentration equilibrium level TL of the monitor area in the measurement object 90 The radioactive concentration equilibrium level TL determined by calculation is displayed by the display unit 40.

  The difference d between the actual measurement value Am of the radioactivity concentration in the monitor area in the measurement object 90 and the radioactivity concentration equilibrium level TL is large immediately after the start of drug administration. The control unit 30 sends out a control signal for adjusting the rate IR of drug administration by the drug administration unit 20 so that the difference d becomes smaller. The drug administration unit 20 receives the control signal to change the drug administration rate IR. The control unit 30 performs injection control (Feedback Controlled Injection, FC-I) based on such feedback control until time te at which the measured value Am of the activity concentration reaches the activity concentration equilibrium level TL. From time te on, the drug administration rate IR is kept constant.

FIGS. 10 and 11 are diagrams for describing a first method of obtaining control parameters used in control by the control unit 30 of the planar imaging device 1 of the present embodiment. When a control parameter is to be determined for a combination of a measurement target 90 and a radioactive drug, the measurement target 90 is disposed in the measurement space of the detection unit 10 and the radioactive drug is contained in the drug administration unit 20. . Control unit 30, at time t _0, indicated with starting the measurement in planar measurement mode to the detection unit 10, instructs the drug administration unit 20, measuring a radiopharmaceutical at a constant drug administration rate Is a preset Administration to the subject 90 is initiated.

  The control unit 30 causes the display unit 40 to display the radioactive concentration Am of the monitor area in the measurement object 90 measured by the detection unit 10, as shown in FIG. The control unit 30 measures and displays the radioactivity concentration Am in such a monitor area until the time te when the activity concentration Am reaches the equilibrium level Le, ie, the temporal change of the radioactivity concentration Am Continue until time te, when equilibrium is reached.

Control unit 30, the time required from drug administration start time t ₀ to an equilibrium level arrival time te as Delta] t, with determining the ratio Ke = Le / Is the equilibrium level Le to drug administration rate Is, equilibrium level reaching time required Delta] t The ratio Kt = Le / Δt of the equilibrium level Le to. The control unit 30 obtains Ke and Kt for each type of radioactive drug and stores them as control parameters.

As shown in FIG. 11, the control unit 30 is expected in the case of administering the radiopharmaceutical to the object to be measured 90 at the initial administration rate I ₀ in the control in the actual measurement using these control parameters. The equilibrium level primary estimated value (Initial Target) T ₀ (= Ke · I ₀ ) reached by the radioactivity concentration A _{0 in the} monitor area is determined. Then, the control unit 30, at time t _0, together with starting the measurement in planar measurement mode instructs the detecting section 10 instructs the drug administration unit 20 the initial dose rate I ₀ measurement object radiopharmaceuticals 90 Start administering to.

If the time ta at which the radioactivity concentration Am in the actual monitor area reaches the equilibrium level primary estimated value T ₀ is earlier than the time te obtained above, the control unit 30 determines that the equilibrium level secondary estimated value (2nd Target ) Find T ₁ (= Kt · ta). As described above, when the radioactivity concentration Am in the actual monitor area overshoots the equilibrium level estimated value, the control unit 30 sequentially raises the target value of the equilibrium level to obtain equilibrium in a short time. Do.

  FIGS. 12-17 is a figure explaining the 2nd method of calculating | requiring the control parameter used by control by the control part 30 of the planar imaging device 1 of this embodiment. In the second determination of the control parameter, the response of the radioactivity concentration in the monitor area to the radioactive drug administration (bolus administration, continuous administration) is determined as follows.

The response characteristics of the radioactivity concentration in the monitor area to the bolus injection of the radioactive drug can be determined as follows. Bolus administration refers to intensive administration of a fixed amount of radiopharmaceutical in a short period of time. Figure As shown in 12, the control unit 30, at time t _0, the detection unit with starting the measurement in planar measurement mode instructs the 10 instructs the drug administration unit 20 radiopharmaceutical measurement object 90 Give a bolus. The control unit 30 causes the detection unit 10 to perform measurement for a sufficient time until the temporal change of the radioactivity concentration has become sufficiently small after passing the peak, and creates a projection image based on the measurement data, A monitor area is set in the measurement object 90 in the projection image.

  Then, the control unit 30 obtains a time change curve TAC (time active curve) of the radioactivity concentration in the monitor area. The monitor area at this time is used as a monitor area when controlling so that the temporal change of the radioactivity concentration is balanced. Furthermore, based on the radioactivity concentration time change curve TAC, the control unit 30 calculates the normalized concentration SUV (standardized uptake value) per kg weight of the measurement object 90 and per bolus dose radioactivity 1 Bq / mL. Radioactivity concentration time change curve TACb is determined (FIG. 13). The normalized activity concentration time change curve TACb represents the response characteristic of the activity concentration of the monitor area to the bolus administration of the radioactive drug, and is determined for each type of radioactive drug.

  The response of the radiation concentration in the monitoring area to the injection of radioactive drug is predicted as follows. Continuous administration refers to continuous administration of a radioactive drug over a fixed period, including when the drug administration rate changes during that fixed period. As shown in FIG. 14, the response characteristic TACi of the radioactivity concentration in the monitor area to the continuous administration of the radioactive drug is the response characteristic (TACb in FIG. 13) to the bolus administration and the dose activity concentration per unit time (Bq / Expected as a superposition integral with mL / sec).

In the administration method combining bolus administration and continuous administration (bolus plus infusion method, B / I method), as shown in FIG. 15, the model response TACm of the activity concentration in the monitor area to the model administration rate is , The model response TACb for bolus administration and the model response TACi for continuous administration (initial dose rate I ₀ ).

In control at the time of actual measurement using these response characteristics as control parameters, control unit 30 instructs detection unit 10 at time t ₀ to perform measurement in the planar measurement mode as shown in FIG. And instructs the drug administration unit 20 to start injecting the radiopharmaceutical into the measurement object 90 according to the model administration rate. Then, based on the measurement data from the detection unit 10, the control unit 30 obtains an actual measurement value Am of the radioactivity concentration in the monitor area in the measurement object 90.

If a difference d occurs between the measured value Am of the radioactivity concentration in the monitor area and the model response TACm, the control unit 30 determines the rate of continuous administration by the drug administration unit 20 so that the difference d becomes smaller. a control signal for adjusting, is sent to the time t _1. Drug administration unit 20 receives the control signal, to change a sustained dose rate from an initial value I ₀ to the primary revised value I _1. As shown in Figure 17, if the measured value Am of radioactivity concentrations also monitor area after changing sustained dose rate at time t ₁ does not reach the model response TACm, the control unit 30 again, the difference d as smaller, a control signal for adjusting the speed of the continuous administration by drug administration unit 20, and sends the time t _2. Drug administration unit 20 receives the control signal, again changing the drug administration rate from the primary revised value I ₁ to the secondary revised value I _2. The control unit 30 performs such control until the measured value Am of the radioactivity concentration in the monitor area reaches the model response TACm.

  FIG. 18 and FIG. 19 are diagrams for explaining the method of determining the balance of the radioactive concentration in the monitor area by the control unit 30 of the planar imaging device 1 of the present embodiment.

The control unit 30 obtains the model response TACm of the activity concentration of the monitor area to the model administration by the B / I method combining the bolus administration and the continuous administration (initial value I _{0 of the} administration rate) by the calculation method described above. Control unit 30, at time t _0, together with starting the measurement in planar measurement mode instructs the detection unit 10, placing the radiopharmaceutical to the measuring object 90 according to the model the rate of administration instructs the drug administration unit 20 To start. Then, based on the measurement data from the detection unit 10, the control unit 30 obtains an actual measurement value Am of the radioactivity concentration in the monitor area in the measurement object 90. The control unit 30 changes the continuous administration rate from the initial value I ₀ to I ₁ and further changes it to I ₂ and I ₃ so that the measured value Am of the radioactivity concentration in the monitor area reaches the model response TACm. Thus, the measured value Am of radioactivity concentrations of the monitor region at a time t ₁ is assumed to be asymptotic model response TACm.

As shown in FIG. 18, control the control unit 30, after time t _1, the predetermined value time rate of change of the measured value Am of radioactivity concentration monitor region in case of performing a continuous infusion in the last administration rate I ₃ It is determined that the primary equilibrium has been reached when the following condition continues for a predetermined time T ₁ or more. Control unit 30 has determined to have reached the primary equilibrium, in the following, the rate of administration of the radiopharmaceutical to the measurement object by the drug administration unit 20 and constant at I _3. The control unit 30 obtains the estimated value of the radioactivity concentration in the monitor area after time t ₂ (= t ₁ + T ₁ ) by superposition of the bolus dose response characteristic described above, and the balance expected to maintain the first order balance The duration T ₂ (time t _{2 to} t ₃ ) is determined.

As shown in Figure 19, within the period of the expected equilibrium duration T _2, evaluated the agent is administered to the measurement object 90, the effect of the evaluation target drug is evaluated. In the period T ₃ (time t _{2 to} t ₃ ) of the expected equilibrium duration T ₂ (time t _{2 to} t ₅ ), measurement is performed by the detection unit 10 in the 3D measurement mode, and then the measurement object 90 is measured. The drug to be evaluated is administered, and the detection unit 10 performs measurement in the planar measurement mode. By the measurement in this planar measurement mode, the temporal change of the radioactivity concentration of the monitor area in the measurement object 90 to which the evaluation object drug is administered can be obtained.

Then, the control unit 30 determines that the secondary equilibrium has been reached when the time change rate of the measured value Am of the radioactivity concentration in the monitor area is less than or equal to a predetermined value continues for a predetermined time or more. When it is determined to have reached the second equilibrium, in the period _{T 5} (time _t 4 ~t ₅₎ of the expected equilibrium duration _{T 2} (time _t 2 ~t _5), measured in the 3D measurement mode by the detection unit 10 Is done.

  The control unit 30 creates a tomographic image of the activity concentration distribution in the measurement object 90 based on the measurement data collected in the 3D measurement mode during the primary equilibrium period, and uses the measurement data collected in the 3D measurement mode during the secondary equilibrium period. Based on the tomographic image of the radiation concentration distribution in the measurement object 90 is created. In addition, the control unit 30 determines the time required for the state change from the primary equilibrium to the secondary equilibrium due to the administration of the drug to be evaluated, the difference in the radioactivity concentration in the monitoring area in each of the primary equilibrium state and the secondary equilibrium state, or The effects of the evaluation target drug administered to the measurement object 90 are evaluated based on the tomographic image of the activity concentration distribution in the measurement object 90 in each of the equilibrium period and the secondary equilibrium period.

(First embodiment)
In the first example, a rat was used as a measurement target 90, and the rat brain was used as a monitoring region, and [ ¹¹ C] Raclopride, which binds to a dopamine D ₂ receptor in the brain striatum, was used as a radiopharmaceutical. The radioactive drug [ ¹¹ C] Raclopride was administered to rats, and measurement was performed in a planar measurement mode to measure the time change of the rat's brain radioactivity concentration. The bolus dose of radioactive drug was 1 mL and the continuous dose rate of radioactive drug was 0.8 mL / h.

  FIG. 20 shows bolus dose response characteristics (BolusTAC) in the first embodiment. FIG. 21 shows time change of radioactive drug administration (Injection) in the first example, model response TAC (Bolus TAC) to bolus administration, model response TAC (Infusion TAC) to continuous administration, and a model response TAC of the sum thereof. It is a figure which shows (Bolus + Infusion TAC).

  FIG. 22 is a diagram showing the time change of the radioactive concentration in the monitor area measured in the first embodiment. As shown in the figure, in the period of time 0 minutes to 30 minutes, the period of time 55 minutes to 65 minutes, and the period of time 90 minutes to 100 minutes, the measurement is performed in the planar measurement mode, and the radioactivity in the monitor area is measured. The concentration was measured. Thus, the observed values are in good agreement with the estimated model response TAC (Bolus + Infusion TAC). In addition, it was confirmed that the radioactivity concentration in the monitor area was in equilibrium after about 30 minutes.

Second Embodiment
In the second embodiment, using a cylindrical phantom filled with a radioactive drug as a whole, measurement was performed in a 3D measurement mode to measure the temporal change of the radioactivity concentration and create a tomographic image. Measured in 3D measurement mode when the temporal change of the radioactivity concentration in the region (target site) where the radiopharmaceutical is present in the cylindrical phantom is small and when the activity concentration of the target site decreases with the passage of time Did.

  FIG. 23 is a diagram showing the time change of the radioactive concentration of the target portion of the cylindrical phantom in the second embodiment. FIGS. 24A and 24B are tomographic images of a cylindrical phantom obtained in the second embodiment. FIG. 24 (a) shows the case where the temporal change in the radioactive concentration at the target site is small. FIG. 24 (b) shows the case where the radioactive concentration at the target site decreases with the passage of time.

  In the case where the target site is wide as in the case of a cylindrical phantom in which the radioactive drug is completely filled, artifact noise is noticeable in the tomographic image obtained by the planar imaging device when the radioactivity concentration of the target site changes with time. Figure 24 (b). On the other hand, when the radioactivity concentration at the target site is kept constant, artifact noise is not noticeable in the tomographic image obtained by the planar imaging device (FIG. 24A).

Third Embodiment
In the third embodiment, using a cylindrical phantom in which the concentration of the radioactive drug is high only in a part of the whole region (HotSpot), measurement is performed in the 3D measurement mode, and the region where the concentration of the radioactive drug is high in the cylindrical phantom The radioactivity concentration of the region is measured while decreasing with time, and the other regions of the cylindrical phantom are measured while keeping the radioactivity concentration constant, and a tomographic image is measured based on the measurement data collected at each time Created.

  FIG. 25 is a diagram showing temporal changes in radioactivity concentrations of the target region and other regions of the cylindrical phantom in the third embodiment. While the temporal change in the activity concentration of the other regions (Cylinder) of the cylindrical phantom is small, the activity concentration of the target site (HotSpot), which is a part of the whole, decreases with the passage of time.

  FIGS. 26, 27 (a) and 27 (b) and FIGS. 28 (a) and 28 (b) are tomographic images of the cylindrical phantom obtained in the third embodiment. The tomographic image of FIG. 26 is a tomographic image of a cylindrical phantom obtained immediately after the injection of the radiopharmaceutical. The respective tomographic images of FIG. 27 (a), FIG. 27 (b), FIG. 28 (a) and FIG. 28 (b) were obtained in order according to the lapse of time thereafter.

  The tomographic image immediately after the radiopharmaceutical injection in FIG. 26 shows the target area as a dark area in the figure and is accurate. As shown in FIGS. 27 and 28, as the radioactivity concentration in the target area decreases with time, artifact noise increases in the target area in the tomographic image. In the present embodiment, since the temporal change of the radioactive concentration of the target site can be reduced, an accurate tomographic image of the target site can be obtained.

Fourth Embodiment
In the fourth example, a rat was used as a measurement target 90, a rat brain was used as a monitor area, and [ ¹¹ C] Raclopride was used as a radioactive drug. Radioactive drug [ ¹¹ C] Raclopride is administered to rats, and measurement is performed in the planar measurement mode to measure the time change of the radioactivity concentration in the rat brain, and measurement is performed in the 3D measurement mode to create a tomographic image of the rat did. In the comparative example, only bolus administration of the radiopharmaceutical was performed, and continuous administration was not performed, and the bolus dose was 1 mL. In the example, the bolus dose of the radioactive drug was 1 mL and the continuous dose rate of the radioactive drug was 1.0 mL / h. 29 to 31 show the results of the comparative example, and FIGS. 32 to 34 show the results of the example.

  FIG. 29 is a diagram showing the time change of the radioactivity concentration in the monitor area in the comparative example. In the comparative example, the radioactivity concentration in the monitor area is determined by performing measurement in the planar measurement mode immediately after bolus administration, in a period of 30 minutes to 40 minutes after bolus administration, and in a period of 65 minutes to 80 minutes after bolus administration. The In addition, in the first period of 5 minutes to 25 minutes after bolus administration and in the second period of 40 minutes to 60 minutes after bolus administration, measurement was performed in the 3D measurement mode to create a tomographic image of the measurement object. As shown in the figure, the radioactivity concentration in the monitor area decreases with the passage of time, and the reduction rate is larger in the first period than in the second period.

  FIG. 30A is a tomographic image created based on measurement data collected in the 3D measurement mode of the first period in the comparative example. FIG. 30B is a tomographic image created based on measurement data collected in the 3D measurement mode of the second period in the comparative example. As shown in the figure, the tomographic image of the first period (5 minutes to 25 minutes after bolus administration) having a high radioactivity concentration immediately after bolus administration is smooth since it has good statistical accuracy. On the other hand, the tomographic image in the second period (40 minutes to 60 minutes after bolus administration) in which the radioactivity concentration is small has poor statistical accuracy and therefore has poor image quality.

  FIG. 31 is a graph of quantitative values (Str / Cere, striatal cerebellum ratio) of radioactivity concentration in the brain obtained from tomographic images of the first period and the second period in the comparative example. The quantitative value of the radioactivity concentration in the brain is lower at sites where the change in radioactivity concentration is large, so the second period (40 minutes to 60 minutes after bolus administration) compared to the first period (5 minutes to 25 minutes after bolus administration) The quantitative value of the radioactivity concentration in the brain obtained from tomographic images is rising.

  FIG. 32 is a diagram showing the time change of the radioactive concentration in the monitor area in the fourth embodiment. In the example, measurement is performed in the planar measurement mode in a period immediately after bolus administration to 15 minutes after bolus administration, a period of 40 minutes to 50 minutes after bolus administration, and a period of 75 minutes to 80 minutes after bolus administration. The radioactivity concentration in the monitor area was determined. In addition, in the first period of 20 minutes to 40 minutes after bolus administration and in the second period of 50 minutes to 70 minutes after bolus administration, measurement was performed in the 3D measurement mode to create a tomographic image of the measurement object. As shown in the figure, after 15 minutes after bolus administration, the radioactivity concentration in the monitor area is in equilibrium.

  FIG. 33A is a tomographic image created based on measurement data collected in the 3D measurement mode of the first period in the fourth embodiment. FIG. 33B is a tomographic image created based on measurement data collected in the 3D measurement mode of the second period in the fourth embodiment. As shown in the figure, the differences in the image quality of the tomographic images in the first period (20 minutes to 40 minutes after bolus administration) and the second period (50 minutes to 70 minutes after bolus administration) are compared with the comparative example. small.

  FIG. 34 is a graph of quantitative values (Str / Cere, striatal cerebellum ratio) of radioactivity concentration in the brain obtained from tomographic images of the first period and the second period in the fourth example. As shown in the figure, quantitative values of brain radioactivity concentration obtained from tomographic images of the first period (20 minutes to 40 minutes after bolus administration) and the second period (50 minutes to 70 minutes after bolus administration) Are comparable to one another. Compared with the comparative example, in the fourth embodiment, the change in quantitative value is also improved.

  DESCRIPTION OF SYMBOLS 1 ... planar imaging device, 10 ... detection part, 11 ... 1st detector array, 12 ... 2nd detector array, 20 ... drug administration part, 30 ... control part, 40 ... display part.

Claims (6)

A first detector array and a second detector array, each of which includes a plurality of gamma ray detectors arranged, wherein the first detector array and the second detector array are disposed to face each other across the measurement space, A detection unit which is rotatable around a predetermined axis passing through the measurement space;
A drug administration unit configured to administer a radioactive drug to a measurement object disposed in the measurement space;
A control unit that controls the operation of each of the detection unit and the drug administration unit;
Equipped with
The control unit
The detection unit is disposed in a predetermined orientation, and the activity concentration value of the monitor area in the measurement object in the planar projection image obtained by the detection unit is acquired, and the measurement administration object by the drug administration unit is obtained. Control the administration of radioactive drugs,
When the temporal change of the acquired radioactivity concentration is in equilibrium (hereinafter referred to as “primary equilibrium”), the administration rate of the radioactive drug to the measurement object by the drug administration unit is made constant thereafter, and the first period The detection unit is arranged in each of a plurality of orientations around the predetermined axis while maintaining the primary balance over all the time, and measurement data by the detection unit is collected;
Based on the measurement data collected in the first period, a tomographic image of the radioactivity concentration distribution in the measurement object is created.
Planar imaging device. The control unit
After the first period, the detection unit is arranged in the predetermined orientation, and the monitor region in the measurement object in the planar projection image obtained by the detection unit for the measurement object to which the evaluation target drug is administered Get the value of the radioactivity concentration of
When the temporal change of the acquired radioactivity concentration becomes equilibrium (hereinafter referred to as “secondary equilibrium”), the detection unit is maintained around the predetermined axis while maintaining the secondary equilibrium over the second period. The measurement data is collected by the detection unit by arranging each in a plurality of orientations,
Based on the measurement data collected in the second period, creating a tomographic image of the radioactivity concentration distribution in the measurement object,
The planar imaging device according to claim 1. The time taken for the control unit to change the state from the primary equilibrium to the secondary equilibrium due to administration of the evaluation target drug, and the difference in the radioactivity concentration of the monitor area in each state of the primary equilibrium and the secondary equilibrium Or, based on the tomographic image of the activity concentration distribution in the measurement object in each of the first period and the second period, the effect of the evaluation target drug administered to the measurement object is evaluated.
The planar imaging device according to claim 2. When the control unit arranges the detection unit in each of a plurality of azimuths around the predetermined axis and collects measurement data by the detection unit, the control unit collects data in each of the plurality of azimuths for a predetermined time. ,
The planar imaging device according to any one of claims 1 to 3. When the control unit arranges the detection unit in each of a plurality of azimuths around the predetermined axis and collects measurement data by the detection unit, the control data makes the time for collecting measurement data different in each of the plurality of azimuths Equalize the statistical accuracy of the measurement data of each direction,
The planar imaging device according to any one of claims 1 to 3. When the control unit arranges the detection unit in a plurality of directions around the predetermined axis and collects measurement data by the detection unit, the control unit repeatedly swings the detection unit around the predetermined axis. To set the azimuths in each direction to equalize the statistical accuracy of the measurement data of each
The planar imaging device according to any one of claims 1 to 3.