JP2011163966A - Medical imagery diagnostic apparatus and control program for radiation dose calculation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To capture radiation dose in surrounding of a radioactive isotope administered subject in real time. <P>SOLUTION: When PET imaging is performed to a radioactive isotope administered subject 150, a living body dose calculating section of a dose calculating section 42 extracts out a body shape model corresponding to weight of the subject 150 among various body shape models beforehand kept in a body shape model storage section 41 and computes continuously radiation dose in the living body at the time when the radioactive isotope is distributed uniformly inside the body shape model. Then, an extracorporal dose calculating section of the total dose calculating section 42 computes extracorporal radiation dose in a predetermined domain of surrounding of the subject, based on the calculation result of the intracorporal radiation dose, whereas a distribution data generating section 43 generates the radiation dose distribution data based on the extracorporeal radiation dose computed in a plurality of domains by the extracorporal radiation dose calculating section. Finally, a displaying section 5 displays the value of extracorporal radiation dose in the predetermined domain and the radiation dose distribution data on a self-monitor. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a medical image diagnostic apparatus and a radiation dose calculation control program capable of estimating a radiation dose around a subject to which a drug labeled with a radioisotope is administered.

  Medical image diagnosis using an X-ray diagnostic apparatus, an MRI apparatus, an X-ray CT apparatus, a nuclear medicine imaging apparatus, etc. has made rapid progress along with the development of computer technology and has become indispensable in today's medical care. Yes.

  The above-mentioned X-ray diagnostic apparatus and X-ray CT apparatus are intended for so-called morphological diagnosis in which an outline of an organ, a tumor, or the like is drawn, whereas a nuclear medicine imaging apparatus is selected as a living tissue. Γ-rays emitted from a radioactive isotope or a labeled compound that is taken in automatically are measured from outside the body, and the dose distribution is imaged to enable functional diagnosis on the subject.

  As nuclear medicine imaging devices, gamma cameras, single photon emission CT devices (SPECT (Single Photon Emission Computed Tomography) devices), positron emission CT devices (PET (Positron Emission Computed Tomography) devices), etc. are used in clinical settings. .

  The gamma camera is a flat detector in which γ rays emitted from the inside of a subject to which a drug labeled with a radioisotope (hereinafter referred to as a radioisotope) is administered are arranged facing the subject. Is a device that generates the distribution of the radioisotope projected onto the flat detector as two-dimensional image data (gamma image data). The collimator attached to the front surface of the flat detector detects γ rays. The incident direction is specified.

  The SPECT apparatus moves a flat detector similar to a gamma camera around a subject to which a radioisotope is administered, or arranges a plurality of flat detectors, and detects γ-ray information detected from a plurality of directions with respect to the subject. The image data (SPECT image data) is generated by performing a reconstruction process similar to that of the X-ray CT apparatus.

  The PET device, on the other hand, administers a radioisotope labeled with a nuclide that emits positrons (positrons) to the subject, and detects this ring-shaped detection around the subject when these positrons combine with the electrons and disappear. Image data (PET image data) is generated by reconstructing a pair of gamma ray information detected by the instrument.

  In recent years, a so-called X-ray CT combined positron CT apparatus (PET-CT apparatus) in which an X-ray CT apparatus and a PET apparatus are integrated has also been developed. According to this PET-CT apparatus, it is possible to efficiently perform morphological diagnosis and functional diagnosis on the same subject, and when reconstructing projection data collected by PET imaging to generate PET image data Then, by correcting the projection data using attenuation correction data (attenuation map) generated based on the pixel values of the X-ray CT image data, good quality PET image data can be obtained (see, for example, Patent Document 1). .)

  By the way, a medical worker (hereinafter referred to as an operator) such as a doctor or an inspector who performs an examination on a subject using a medical image diagnostic apparatus that emits X-rays such as an X-ray CT apparatus or an X-ray diagnostic apparatus. ), Or an operator who performs various medical treatments on a subject that emits γ-rays by administration of a radioisotope in an examination using the above-described nuclear medicine imaging apparatus, a fluorescent glass dosimeter that detects radiation, The exposure dose received during the inspection is managed by always wearing a dosimeter such as a thermoluminescence dosimeter or a film badge (see, for example, Patent Document 2).

JP 2009-47602 A JP 2007-327864 A

  An operator who performs an examination using an X-ray CT apparatus or an X-ray diagnostic apparatus on the subject gives instructions to the subject or operates the apparatus on a console or the like placed outside the shielded examination room. Therefore, it is extremely unlikely that the operator who is inspecting will receive an exposure dose that exceeds the allowable value determined by law. On the other hand, an operator who performs an examination using the above-described nuclear medicine imaging apparatus or PET-CT apparatus on a subject to which a radioisotope has been administered is guided to the laboratory, placed on the top, Therefore, there is a possibility of receiving a relatively large exposure dose because it is necessary to perform a medical act such as the explanation in the vicinity of the subject as a radiation source.

  In such a case, the operator must minimize the exposure dose received during the examination by performing the above-mentioned medical practice in an area where the radiation dose is low, but a conventional dosimeter such as a film badge. The statistical count data obtained by the above method has a problem that the radiation dose in a predetermined area in the examination room cannot be grasped in real time.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a medical image diagnostic apparatus and radiation capable of grasping in real time a radiation dose around a subject to which a radioisotope is administered. It is to provide a control program for quantity calculation.

  In order to solve the above-described problem, the medical image diagnostic apparatus according to the first aspect of the present invention detects γ-rays emitted from a subject administered with a radioisotope, and generates image data based on the detected data. The medical diagnostic imaging apparatus includes a radiation dose estimation unit that estimates a radiation dose emitted from the subject, and a display unit that displays a radiation dose estimation result by the radiation dose estimation unit. .

  The radiation dose calculation control program of the present invention according to claim 11 detects a γ-ray emitted from a subject administered with a radioisotope, and generates image data based on the detected data. A body model setting function for setting a body model based on the object information of the subject for the apparatus, and estimating a radiation dose around the object based on the radioisotope distributed inside the body model And a display function for displaying the radiation dose estimation result.

  According to the present invention, it is possible to easily grasp the radiation dose around the subject to which the radioisotope is administered. For this reason, the operator can perform a medical practice on the subject in a region where the radiation dose is small, and the exposure dose received during the examination can be reduced.

1 is a block diagram showing the overall configuration of a medical image diagnostic apparatus in an embodiment of the present invention. The block diagram which shows the specific structure of the X-ray CT imaging part with which the medical image diagnostic apparatus of the Example is provided. The block diagram which shows the specific structure of the PET imaging part with which the medical image diagnostic apparatus of the Example is provided. The figure which shows the specific structure of the detector module provided in the PET imaging part of the Example. The figure which shows the specific example of the radiation dose distribution data which the distribution data generation part of the Example produces | generates. The figure for demonstrating the X-ray CT frame part and PET frame part which are moved by the movement mechanism part of the Example. The flowchart which shows the estimation procedure of the radiation dose in the Example. The block diagram which shows the whole structure of the medical image diagnostic apparatus in the modification of the Example.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the medical image diagnostic apparatus of the present embodiment described below, when PET imaging is performed on a subject to which a radioisotope has been administered, body models corresponding to the body weight of the subject are stored in advance. The internal radiation dose at the current time when the radioisotope is uniformly distributed within the body shape model is continuously calculated. Next, calculation of the external radiation dose in a predetermined region around the subject based on the calculation result of the internal radiation dose and generation of radiation dose distribution data based on the external radiation dose calculated in a plurality of regions, and the obtained external radiation The amount value and radiation dose distribution data are displayed on the display unit.

  In the following embodiments, a medical image diagnostic apparatus capable of generating X-ray CT image data for morphological diagnosis and PET image data for functional diagnosis will be described. It may be a medical image diagnostic apparatus capable of generating data, gamma image data, etc., or a medical image diagnostic apparatus capable of generating MRI image data, X-ray image data, etc. for morphological diagnosis. Also good.

(Device configuration)
The configuration of the medical image diagnostic apparatus according to the embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing the overall configuration of the medical image diagnostic apparatus according to the present embodiment. FIGS. 2 and 3 are specific examples of the X-ray CT imaging unit and the PET imaging unit included in the medical image diagnostic apparatus. It is a block diagram which shows a structure.

  As shown in FIG. 1, the medical image diagnostic apparatus 100 of this embodiment generates X-rays that are emitted from the X-ray tube of the X-ray generator 11 that rotates at high speed around the subject 150 and transmitted through the subject 150. X-ray CT imaging unit 1 that generates projection data (first projection data) detected by the X-ray detector of unit 12 and a pair emitted from subject 150 to which a radioisotope (RI) is administered A PET imaging unit 2 that generates projection data (second projection data) by detecting the γ-rays of the γ-rays by a detector module 21 arranged around the γ-ray, and a first projection generated by the X-ray CT imaging unit 1 The image data generation unit 3 that reconstructs the data and the second projection data generated in the PET imaging unit 2 to generate X-ray CT image data and PET image data, and the subject 150 to which the radioisotope is administered. From And a radiation dose estimation unit 4 performs a calculation of the amount of radiation Isa generation of radiation dose distribution data based on the calculation result.

  In addition, the medical image diagnostic apparatus 100 includes the X-ray CT image data and the PET image data generated by the image data generation unit 3 and the radiation dose value and the radiation dose in a predetermined region obtained in the radiation dose estimation unit 4. The display unit 5 for displaying the distribution data, the top plate 6 placed on a bed (not shown) on which the subject 150 is placed, and the rotating gantry unit on which the above-described X-ray tube and X-ray detector are mounted are provided on the subject 150. A moving mechanism unit 7 that rotates at high speed around and moves the X-ray CT gantry having the X-ray CT imaging unit 1 and the PET gantry having the PET imaging unit 2 in the body axis direction (z-axis direction) of the subject 150; An input unit 8 for inputting specimen information, setting imaging conditions in X-ray CT imaging and PET imaging, setting image data generation conditions and image data display conditions, inputting various command signals, and the like, and a medical image diagnostic apparatus And a system controller 9 centrally controls each unit of the above-described 100.

  Next, the configuration and function of each of the units included in the medical image diagnostic apparatus 100 will be described in more detail.

  As shown in FIG. 2, the X-ray CT imaging unit 1 shown in FIG. 1 includes an X-ray generation unit 11, a projection data generation unit 12, a rotary gantry unit 13, and a fixed gantry unit 14. The X-ray tube 111 that irradiates the subject 150 with X-rays, the high-voltage generator 112 that generates a high voltage applied between the anode and the cathode of the X-ray tube 111, and the X-ray tube 111 An X-ray restrictor 113 that controls the irradiation range of the X-ray subject 150 and a slip ring 114 that supplies electric power to the rotary mount unit 13 are provided.

  The X-ray tube 111 is a vacuum tube that generates X-rays, and emits X-rays by colliding electrons accelerated by a high voltage supplied from the high-voltage generator 112 with a tungsten target. On the other hand, the X-ray restrictor 113 is provided between the X-ray tube 111 and the subject 150 and has a function of narrowing the X-rays emitted from the X-ray tube 111 to a predetermined imaging region and X-ray irradiation to the subject 150. It has a function to set the intensity distribution. For example, the X-ray beam radiated from the X-ray tube 111 is shaped into a cone beam or fan beam X-ray beam corresponding to the imaging region.

  Next, the projection data generation unit 12 supplies an X-ray detector 121 that detects X-rays that have passed through the subject 150 and a plurality of channels of detection signals (projection data) output from the X-ray detector 121. / Voltage conversion and A / D conversion data acquisition unit (hereinafter referred to as DAS (Data Acquisition System) unit) 122, parallel / serial conversion, electrical / optical / electrical conversion for the output signal of DAS unit 122 And a data transmission circuit 123 for performing serial / parallel conversion.

  The X-ray detector 121 of the projection data generation unit 12 includes, for example, a plurality of X-ray detection elements (not shown) that are two-dimensionally arranged. Each of the X-ray detection elements is a scintillator that converts X-rays into light. It is composed of a photodiode that converts light into an electrical signal. These X-ray detection elements are attached to the rotating gantry 13 along an arc centered on the focal point of the X-ray tube 111.

  On the other hand, the DAS unit 122 performs current / voltage conversion and A / D conversion on the projection data supplied from the X-ray detector 121. The data transmission circuit 123 includes a parallel / serial converter, an electrical / optical / electrical converter, and a serial / parallel converter (not shown). The projection data output from the DAS unit 122 is attached to the rotating gantry 13. The serial / parallel converter which is converted into time-series projection data of one channel in the parallel / serial converter and is attached to the fixed base 14 by optical communication using the electric / optical / electric converter. To be supplied.

  Next, in the serial / parallel converter, the projection data of one channel is returned to the projection data of the plurality of channels and supplied to the image data generation unit 3. This data transmission method is another method as long as signal transmission is possible between the projection data generation unit 12 provided on the rotary gantry unit 13 and the image data generation unit 3 provided outside the fixed gantry unit 14. For example, a device such as the slip ring described above may be used.

  Then, the X-ray tube 111 and the X-ray diaphragm 113 of the X-ray generation unit 11 and the X-ray detector 121 and the DAS unit 122 of the projection data generation unit 12 face each other so as to sandwich the subject 150 therebetween. Mounted on the unit 13, the moving mechanism unit 7 rotates at a high speed around an axis parallel to the body axis direction (z-axis direction) of the subject 150.

  Next, as shown in FIG. 3, the PET imaging unit 2 in FIG. 1 is arranged concentrically around the subject 150 and emits a pair of γ rays emitted from the subject 150 to which a radioisotope is administered. Detector module 21 for detecting γ-rays and noise, detection time and detection position of γ-rays, and detection of γ-ray incident direction based on a pair of γ-ray detection positions measured simultaneously A detection data processing unit that performs calculation, and further generates projection data (second projection data) by sequentially storing the count value of γ rays in a predetermined period corresponding to the γ ray detection position and the γ ray incident direction. 22.

  A plurality of detector modules 21 (21-1 to 21-Nm) are arranged concentrically around the subject 150 placed on the top plate 6, and the γ rays emitted from the subject 150 are these. After being converted into visible light by the detector module 21, it is converted into an electric signal (detection signal).

  FIG. 4 shows a specific configuration of the detector module 21, and each of the detector modules 21-1 to 21 -Nm detects γ-rays radiated from the subject 150 to make visible light. A strip-shaped scintillator 211 for conversion, a photomultiplier tube 212 for converting the visible light converted by the scintillator 211 into an electrical signal and amplifying the weak electrical signal that has been converted, and the visible light output from the scintillator 211 as photoelectrons A light guide 213 that transmits to the multiplier tube 212 is provided.

The scintillator 211 is made of a material such as bismuth germanide (BGO: (Bi ₄ Ge ₃ O ₁₂ )), thallium activated sodium iodide (NaI (Tl)), barium fluoride (BaF ₂ ), and in particular, PET. For imaging, bismuth germanide having a high γ-ray photoelectric absorption per unit volume and barium fluoride having a high response speed are suitable.

For example, the photomultiplier tube 212 amplifies several hundred photons into 10 ⁷ to 10 ¹⁰ electrons, collects the electrons in an anode as an output stage, and converts them into an electrical signal. And an electron multiplier. For the photocathode, a multi-alkali material whose wavelength characteristic is substantially equal to the emission wavelength of the scintillator 211 or a bi-alkali material activated with oxygen or cesium is used, and the number of generated photoelectrons with respect to the number of incident photons is usually 20% to 30%. %. On the other hand, the electron multiplier is composed of multi-stage electrodes arranged along an electron propagation path and an anode for collecting amplified electrons based on the secondary electron emission phenomenon. The tube voltage for amplification factor per stage in the case of 200V to 300V is about 5-fold, 10-stage approximately electrode is provided in order to obtain a ¹⁰⁷ amplification factor of the above.

  The light guide 213 is for optically coupling the scintillator 211 and the photomultiplier tube 212, and is light transmissive in order to efficiently transmit visible light output from the scintillator 211 to the photomultiplier tube 212. Excellent plastic material is used.

  Returning to FIG. 3, the detection data processing unit 22 of the PET imaging unit 2 includes Nm-channel data processing units 221-1 to 221-Nm connected to each of the detector modules 21-1 to 21-Nm. An incident direction calculation unit 222 that calculates the incident direction of the γ-ray based on the detected position information of the γ-ray output from the data processing units 221-1 to 221-Nm, and the count value of the detection signal as the γ-ray detection position. And a projection data generation unit 223 that generates projection data (second projection data) by sequentially storing the corresponding γ-ray incident directions. Here, it is assumed that a pair of γ rays emitted from the radioisotope S administered to the subject 150 is detected by the detector modules 21-a and 21-b, and these detector modules 21 Only the data processing units 221-a and 221-b connected to -a and 21-b are shown.

  The data processing units 221-a and 221-b of the detection data processing unit 22 add and synthesize the detection signals of a plurality of channels supplied from the photomultiplier tubes 212 of the detector modules 21-a and 21-b. 231 and a signal discriminating unit 232 for discriminating a detection signal and noise caused by γ-ray emission based on the respective peak values using the detection signal synthesized in the signal synthesizing unit 231; A waveform shaping unit 233 for shaping the output detection signal after synthesis into a rectangular wave, and a γ-ray detection time is measured based on the front edge of the rectangular wave, and the γ is detected with respect to the detection signal discriminated by the signal discrimination unit 232 A detection time measuring unit 234 for adding line detection time information is provided.

  Further, the data processing units 221-a and 221-b detect the γ-ray detection positions based on the detection signals of a plurality of channels supplied from the photomultiplier tubes 212 of the detector modules 21-a and 21-b. A position measurement unit 235 and a detection position setting unit 236 that further adds the above-described γ-ray detection position information to a detection signal to which information on the γ-ray detection time by the detection time measurement unit 234 is added. The specific configuration and function of the data processing unit 221 are described in Japanese Patent Application Laid-Open No. 2007-107995 and the like, and thus detailed description thereof is omitted.

  Next, the incident direction calculation unit 222 of the detection data processing unit 22 is γ-ray that is incidental information of the detection signal supplied from the detection position setting unit 236 provided in each of the data processing units 221-1 to 221-Nm. Based on detection time information, a detection signal measured in a preset detection period (for example, a detection signal based on the radioisotope S supplied from each of the detector module 12-a and the detector module 12-b) ). Then, the γ-ray incident direction is calculated based on the information of the γ-ray detection position added to these detection signals.

  On the other hand, the projection data generation unit 223 includes a storage circuit (not shown) and associates the count value of the detection signal supplied from the incident direction calculation unit 222 with the above-described γ-ray detection position and γ-ray incidence direction in the storage circuit. save. For example, every time the detector module 21-a and the detector module 21-b detect γ rays, the count value of the detection signal is integrated at the corresponding address of the storage circuit.

  On the other hand, when a pair of γ-rays is detected in the other detector module 12, the γ-ray detection position and the γ-ray incident direction are measured by the same method as described above, and the count value of the detection signal is determined as the γ-ray detection position and The data is sequentially stored in the storage circuit in correspondence with the γ-ray incident direction. That is, in the storage circuit of the projection data generation unit 223, the count values of detection signals corresponding to a plurality of γ-ray detection positions and γ-ray incidence directions are integrated for a predetermined period to generate projection data.

  Next, the image data generation unit 3 of the medical image diagnostic apparatus 100 illustrated in FIG. 1 includes a projection data storage unit 31, a reconstruction processing unit 32, and an attenuation correction data generation unit 33, and includes an X-ray CT imaging unit 1 and a PET. It has a function of generating X-ray CT image data and PET image data based on projection data generated in each of the imaging units 2.

  The projection data storage unit 31 of the image data generation unit 3 stores the projection data (first projection data) generated by the projection data generation unit 12 of the X-ray CT imaging unit 1 and the detection data processing unit 22 of the PET imaging unit 2. Projection data (second projection data) generated in is temporarily stored.

  The reconstruction processing unit 32 includes a program storage unit in which various reconstruction processing programs are stored in advance and a calculation unit (none of which are shown). The arithmetic unit receives image data generation conditions supplied from the input unit 8 via the system control unit 9, and reads a processing program suitable for the reconstruction processing conditions of the image data generation conditions from the program storage unit. Then, X-ray CT image data is generated by reconstructing the first projection data read from the projection data storage unit 31 based on the processing program.

  Further, the reconstruction processing unit 32 corrects the second projection data read from the projection data storage unit 31 using the attenuation correction data supplied from the attenuation correction data generation unit 33, and the corrected second projection data. Reconstruction processing is performed for the above by the same procedure as described above to generate PET image data.

  On the other hand, the attenuation correction data generation unit 33 includes a correction data storage circuit (not shown), and calculates an attenuation coefficient based on the pixel value (CT value) of the X-ray CT image data generated by the reconstruction processing unit 32. Next, using the obtained attenuation coefficient, two-dimensional attenuation correction data (attenuation map) is generated and stored in the correction data storage circuit.

  Next, the radiation dose estimation unit 4 includes a body shape model storage unit 41, a dose calculation unit 42, and a distribution data generation unit 43.

  In the body model storage unit 41, various body models in which the shape of the subject is approximated by a spheroid or the like are stored in advance using, for example, the weight of the subject as a parameter. In this case, the polar radius and the equator radius of the spheroid representing the body model are determined based on the weight of the subject.

The dose calculation unit 42 includes an in-vivo dose calculation unit and an extracorporeal dose calculation unit (not shown), and the in-vivo dose calculation unit is a radiation dose (in-vivo radiation dose) at a current time t1 of a local part of the body to which a radioisotope is administered. V1 is calculated based on the following equation (1).

  However, in the formula (1), V0 represents the dose of the radioisotope to the subject 150, t0 represents the administration time of the radioisotope, τx represents the half-life of the administered radioisotope, and K represents a constant.

  On the other hand, the extracorporeal dose calculation unit receives subject information supplied from the input unit 8 via the system control unit 9, and calculates a body model corresponding to the weight of the subject 150 included in the subject information. Extracted from various body models stored in the body model storage unit 41 in advance. Then, when the radioisotope having the in-vivo radiation dose V1 calculated by the above equation (1) is assumed to be uniformly distributed inside the body model (ie, around the body model) Extracorporeal radiation dose in the predetermined calculation area is calculated. In this case, the operator of the medical image diagnostic apparatus 100 can arbitrarily set the calculation region of the extracorporeal radiation dose. For example, the operator is located when performing a medical action on the subject 150. The extracorporeal radiation dose in a region 30 cm away from the top 6 is calculated.

  On the other hand, the distribution data generation unit 43 includes a data storage circuit (not shown), and the calculation result of the external radiation dose in the plurality of calculation regions calculated by the extracorporeal dose calculation unit of the dose calculation unit 42 includes the position information of the calculation region. Information is sequentially stored in the data storage circuit. Then, the distribution data generation unit 43 generates the two-dimensional radiation dose distribution data around the subject 150 based on the calculation results of the extracorporeal radiation dose in the plurality of calculation areas read from the data storage circuit and the position information of the calculation areas. Generate.

  FIG. 5 is a specific example of the radiation dose distribution data generated by the distribution data generation unit 43 described above, and FIG. 5A shows the value of the extracorporeal radiation dose calculated by the extracorporeal dose calculation unit of the dose calculation unit 42. The radiation dose distribution data having the shading or color tone corresponding to is shown. On the other hand, FIG. 5B shows the radiation dose distribution data of the contour line display method generated by comparing the value of the extracorporeal radiation dose calculated by the extracorporeal dose calculation unit with a plurality of threshold values. In each case, a) and FIG. 5B are horizontal planes that are centered on the body model 151 of the subject 150 disposed on the top plate 6 and that are separated from the floor by a predetermined distance (for example, 1 m from the floor). 2 shows two-dimensional radiation dose distribution data.

  Returning to FIG. 1 again, the display unit 5 includes a display data generation unit, a conversion processing unit, and a monitor (not shown). The display data generation unit generates display data by converting the X-ray CT image data or PET image data generated by the reconstruction processing unit 32 of the image data generation unit 3 into a predetermined display format, and the conversion processing unit Performs D / A conversion and TV format conversion on the display data generated by the display data generation unit and displays the display data on the monitor. Further, the display data generation unit and the conversion processing unit are configured to apply the radiation dose distribution data generated by the extracorporeal radiation dose value calculated by the dose calculation unit 42 of the radiation dose estimation unit 4 or the distribution data generation unit 43. The same processing is performed and displayed on the monitor.

  Next, the moving mechanism unit 7 includes a gantry rotating unit, a gantry moving unit, and a mechanism control unit (not shown). The rotating gantry 13 of the X-ray CT imaging unit 1 on which the line detector 121 is mounted is rotated around the subject 150 at high speed.

  The gantry moving unit is provided with an X-ray CT gantry unit having an X-ray CT imaging unit 1 and a PET gantry unit having a PET imaging unit 2 on the floor according to a gantry movement control signal supplied from the mechanism control unit. The body 150 is moved in the body axis direction along the guide rail. On the other hand, the mechanism control unit supplies the gantry rotation control signal generated according to the X-ray CT imaging start instruction signal supplied from the input unit 8 via the system control unit 9 to the gantry rotation unit, and according to the gantry movement instruction signal. The generated platform movement control signal is supplied to the platform moving section.

  FIG. 6 is a diagram for explaining the above-described X-ray CT gantry unit and PET gantry unit that are moved by the gantry moving unit of the moving mechanism unit 7. As shown in FIG. A bed 161 having a top plate 6 on which the subject 150 is placed is installed, and a guide rail 162 is disposed in the body axis direction (z-axis direction) of the top plate 6. Then, the X-ray CT gantry unit 163 having the X-ray CT imaging unit 1 or the PET imaging so that the examination target region of the subject 150 is arranged in the imaging field of the X-ray CT imaging unit 1 or the imaging field of the PET imaging unit 2. A suitable imaging position of the subject 150 in X-ray CT imaging and PET imaging is determined by moving the PET gantry 164 having the section 2 in the body axis direction along the guide rail 162.

  Next, the input unit 8 of FIG. 1 includes an input device such as a keyboard, a selection switch, a mouse, and a display panel, and forms an interactive interface when used in combination with the display unit 5. Then, input of subject information, input of radioisotope information (hereinafter referred to as administration drug information) administered to the subject 150, imaging conditions in X-ray CT imaging and PET imaging, image data generation conditions, Setting of image data display conditions, setting of radiation dose calculation conditions, setting of radiation dose distribution data generation conditions, as well as gantry movement instruction signals for the purpose of setting imaging positions in X-ray CT imaging and PET imaging, and each imaging Input of an imaging start instruction signal for starting the image is performed using the above-described display panel and input device. The type of radioisotope, dose V0, half-life τx, administration time t1, etc. are input as the above-mentioned administration drug information.

  On the other hand, the system control unit 9 includes a CPU and a storage circuit (not shown), and the above-described input information and setting information supplied from the input unit 8 are stored in the storage circuit. Then, the CPU comprehensively controls each unit provided in the medical image diagnostic apparatus 100 based on the information read from the storage circuit, and executes X-ray CT imaging and PET imaging, and isotope. The estimation of the radiation dose emitted from the subject 150 to which is administered is executed.

(Radiation dose estimation procedure)
Next, a radiation dose estimation procedure performed in parallel with X-ray CT imaging and PET imaging in this embodiment will be described with reference to the flowchart of FIG.

Prior to X-ray CT imaging and PET imaging of the subject 150, the operator of the medical image diagnostic apparatus 100 labels the subject 150 with positron emission nuclides such as ¹¹ C, ¹³ N, ¹⁵ O, and ¹⁸ F. The resulting compound is administered as a radioisotope (RI) (step S1 in FIG. 7). Next, the operator inputs subject information at the input unit 8, input of drug information (namely, radioisotope type, dose V0, administration time t0, etc.), imaging conditions in X-ray CT imaging and PET imaging. , Setting of image data generation conditions and image data display conditions, setting of radiation dose calculation conditions including an external radiation dose calculation region, setting of radiation dose distribution data generation conditions including position information of the radiation dose distribution data, etc. 7 step S2). These input information and setting information are stored in the storage circuit of the system control unit 9.

  Next, after placing the subject 150 on the top plate 6 attached to the bed 161, the operator inputs a gantry movement instruction signal at the input unit 8, and the diagnosis target region of the subject 150 is the X-ray CT imaging unit. The X-ray CT gantry 163 is moved in the body axis direction along the guide rail 162 so as to be arranged in one imaging field (step S3 in FIG. 7). When the movement of the X-ray CT gantry 163 is completed, an imaging start instruction signal for starting X-ray CT imaging is input at the input unit 8 (step S4 in FIG. 7).

  Receiving this imaging start instruction signal, the system control unit 9 controls each unit provided in the X-ray CT imaging unit 1 based on the imaging conditions read from its own storage circuit, and performs X-ray CT imaging on the subject 150. Do. Then, the projection data (first projection data) obtained at this time is stored in the projection data storage unit 31 of the image data generation unit 3 using the rotation angle information of the rotary mount unit 13 as supplementary information.

  On the other hand, the reconstruction processing unit 32 of the image data generation unit 3 receives the image data generation conditions supplied from the system control unit 9 and sets a processing program suitable for the reconstruction processing conditions of the image data generation conditions in its own program. Read from the storage. Next, X-ray CT image data is generated by reconstructing the projection data read from the projection data storage unit 31 based on the processing program, and the obtained X-ray CT image data is displayed on the monitor of the display unit 5. (Step S5 in FIG. 7).

  On the other hand, the attenuation correction data generation unit 33 of the image data generation unit 3 calculates an attenuation coefficient based on the pixel value (CT value) of the X-ray CT image data generated by the reconstruction processing unit 32. Next, two-dimensional attenuation correction data (attenuation map) is generated using the obtained attenuation coefficient and stored in its own correction data storage circuit (step S6 in FIG. 7).

  When the generation and display of the X-ray CT image data is completed, the operator can use the PET frame unit so that the diagnosis target region of the subject 150 is arranged in the imaging field of the PET imaging unit 2 by the same procedure as Step S3. 164 is moved in the body axis direction along the guide rail 162 (step S7 in FIG. 7), and an imaging start instruction signal for starting PET imaging is input at the input unit 8 (step S8 in FIG. 7). Next, the system control unit 9 that has received this imaging start instruction signal controls each unit provided in the PET imaging unit 2 based on imaging conditions read from its own storage circuit, and performs PET imaging on the subject 150. The projection data (second projection data) obtained at this time is stored in the projection data storage unit 31 of the image data generation unit 3.

  The reconstruction processing unit 32 of the image data generation unit 3 corrects the above-described projection data read from the projection data storage unit 31 based on attenuation correction data supplied from the attenuation correction data generation unit 33. Next, the corrected projection data is reconstructed to generate PET image data and display it on the monitor of the display unit 5 (step S9 in FIG. 7).

  On the other hand, when the input of the subject information, the input of the administration drug information, etc. is completed in the above step S2, the in-vivo dose calculation unit provided in the dose calculation unit 42 of the radiation dose estimation unit 4 is transferred from the system control unit 9. The information of the supplied current time t1 and the information of the radioisotope dose V0, half-life τx, and administration time t0 included in the administered drug information is received, and these information are substituted into the above formula (1). By doing so, the in-vivo radiation dose V1 at the current time t1 in the predetermined calculation area where the radioisotope is administered is calculated (step S10 in FIG. 7).

  Next, the extracorporeal dose calculation unit of the dose calculation unit 42 receives the subject information supplied from the system control unit 9 and converts the body model corresponding to the weight of the subject 150 included in the subject information into the body model. Extracted from various body models stored in the storage unit 41 in advance. Then, an external radiation dose in a predetermined calculation area around the subject when the radioisotope exhibiting the internal radiation dose V1 is assumed to be uniformly distributed inside the body model is calculated, and a plurality of calculation areas are calculated. The calculation result of the extracorporeal radiation dose and the position information of the calculation region obtained in step S1 are stored in the data storage circuit of the distribution data generation unit 43 (step S11 in FIG. 7).

  On the other hand, the distribution data generation unit 43 generates a two-dimensional radiation dose distribution around the subject 150 based on the calculation results of the extracorporeal radiation dose in a plurality of calculation regions read from its own data storage circuit and the position information of the calculation regions. Data is generated (step S12 in FIG. 7).

  The display unit 5 performs a predetermined conversion process on the value of the external radiation dose in the predetermined calculation area calculated by the dose calculation unit 42 of the radiation dose estimation unit 4 and the radiation dose distribution data generated by the distribution data generation unit 43. Is displayed on its own monitor (step S13 in FIG. 7).

(Modification)
Next, a modification of the present embodiment will be described with reference to FIG.

  In the above-described embodiment, a medical image diagnostic apparatus capable of generating X-ray CT image data for morphological diagnosis and PET image data for functional diagnosis has been described. A medical image diagnostic apparatus that generates only PET image data will be described.

  In the block diagram of FIG. 8 showing the overall configuration of the medical image diagnostic apparatus according to this modification, units having the same configuration and function as the unit of the medical image diagnostic apparatus 100 shown in FIG. Detailed description is omitted.

  That is, the medical image diagnostic apparatus 200 in the present modification detects a pair of γ-rays emitted from the subject 150 to which the radioisotope (RI) is administered by the detector module 21 arranged around it. A PET imaging unit 2 that generates projection data, an image data generation unit 3a that generates PET image data by reconstructing the projection data generated in the PET imaging unit 2, and a subject 150 to which a radioisotope is administered. The radiation dose estimation part 4 which calculates the radiation dose discharge | released from and produces | generates the radiation dose distribution data based on this calculation result is provided.

  Further, the medical image diagnostic apparatus 200 displays the PET image data generated by the image data generation unit 3a, and displays the radiation dose value and radiation dose distribution data in a predetermined region in the examination room obtained by the radiation dose estimation unit 4. A display unit 5a, a top plate 6 placed on a couch (not shown) on which the subject 150 is placed, and a PET gantry unit having the PET imaging unit 2 or the top plate 6 on which the subject 150 is placed in the body axis direction ( a moving mechanism unit 7a that moves in the z-axis direction) and an input unit that inputs subject information, sets imaging conditions in PET imaging, image data generation conditions and image data display conditions, and inputs various command signals. 8a and a system control unit 9a that comprehensively controls the above-described units of the medical image diagnostic apparatus 200.

  The image data generation unit 3a of the medical image diagnostic apparatus 200 includes a projection data storage unit 31a, a reconstruction processing unit 32a, and an attenuation correction data generation unit 33a, and PET image data based on the projection data generated in the PET imaging unit 2. It has the function to generate.

  In the projection data storage unit 31a of the image data generation unit 3a, the projection data generated in the detection data processing unit 22 of the PET imaging unit 2 is temporarily stored.

  The reconstruction processing unit 32 includes a program storage unit in which various reconstruction processing programs are stored in advance and a calculation unit (none of which are shown). The arithmetic unit receives an image data generation condition supplied from the input unit 8a via the system control unit 9a, and reads a processing program suitable for the reconstruction processing condition of the image data generation condition from the program storage unit. Then, the projection data read from the projection data storage unit 31a is corrected using the attenuation correction data supplied from the attenuation correction data generation unit 32a, and the reconstructed process is performed on the corrected projection data to obtain the PET image data. Generate.

  On the other hand, the attenuation correction data generation unit 33a includes a correction data storage circuit (not shown), and is supplied from the detection data processing unit 22 of the PET imaging unit 2 in the collection of attenuation correction data by an external source performed prior to the inspection. Two-dimensional attenuation correction data (attenuation map) is generated based on the detected signal, and is temporarily stored in the correction data storage circuit.

  Next, the display unit 5a includes a display data generation unit, a conversion processing unit, and a monitor (not shown). The display data generation unit converts the PET image data generated in the reconstruction processing unit 32a of the image data generation unit 3a into a predetermined display format to generate display data, and the conversion processing unit generates the display data generation D / A conversion and TV format conversion are performed on the display data generated by the display unit and displayed on the monitor. Further, the display data generation unit and the conversion processing unit are configured to calculate the value of the external radiation dose in the predetermined calculation area calculated by the dose calculation unit 42 of the radiation dose estimation unit 4 or the radiation dose distribution generated by the distribution data generation unit 43. The same processing is performed on the data and displayed on the monitor.

  Next, the moving mechanism unit 7a includes a moving mechanism and a mechanism control unit (not shown), and the moving mechanism has a PET gantry unit or subject having a PET imaging unit 2 in accordance with a movement control signal supplied from the mechanism control unit. The top plate 6 on which 150 is placed is moved in the body axis direction (z-axis direction). On the other hand, the mechanism control unit supplies the movement mechanism with the above-described movement control signal generated according to the gantry movement instruction signal or the top board movement instruction signal supplied from the input unit 8a via the system control unit 9a.

  Next, the input unit 8a includes an input device such as a keyboard, a selection switch, a mouse, and a display panel, and forms an interactive interface when used in combination with the display unit 5a. Then, input of subject information, input of administration drug information, imaging conditions in PET imaging, setting of image data generation conditions and image data display conditions, setting of radiation dose calculation conditions, setting of radiation dose distribution data generation conditions, and Input of a movement instruction signal for the purpose of setting an imaging position in PET imaging, an imaging start instruction signal for starting PET imaging, and the like are performed using the above-described display panel and input device.

  On the other hand, the system control unit 9a includes a CPU and a storage circuit (not shown), and the above-described input information and setting information supplied from the input unit 8a are stored in the storage circuit. Then, the CPU comprehensively controls each unit provided in the medical image diagnostic apparatus 200 based on the information read from the storage circuit, executes PET imaging, and radiates from the subject 150 in PET imaging. Estimate the radiation dose to be performed.

  Note that the radiation dose estimation procedure in this modification is the same as the procedure in steps S1 to S2 and steps S10 to S13 shown in FIG.

  According to the embodiments of the present invention described above and modifications thereof, the radiation dose around the subject to which the radioisotope is administered can be grasped in real time. For this reason, the operator can perform a medical practice on the subject in a region where the radiation dose is small, and the exposure dose received during the examination can be reduced.

  In particular, since not only the radiation dose in a predetermined area of the examination room but also the radiation dose in a wide area can be obtained as distribution data, the operator can easily know the area with a small radiation dose. In addition, since the radiation dose value and radiation dose distribution data in the predetermined area are displayed on the display unit of the medical image diagnostic apparatus, the operator can grasp the radiation dose information that changes every moment in the examination room in real time. However, it is possible to perform a medical practice on the subject.

  Furthermore, since the body weight information and administration drug information used for calculating the radiation dose are input in normal PET imaging, the radiation dose around the subject is estimated without increasing the burden on the operator. be able to.

  As mentioned above, although the Example of this invention and its modification were described, this invention is not limited to the above-mentioned Example and its modification, It can change and implement further. For example, in the above-described embodiment, the medical image diagnostic apparatus 100 having the function of generating X-ray CT image data for the purpose of morphological diagnosis and the function of generating PET image data for the purpose of functional diagnosis has been described. As long as necessary information is input, it may be a medical image diagnostic apparatus capable of generating other nuclear medicine image data such as SPECT image data and gamma image data for function diagnosis, and for morphological diagnosis. A medical image diagnostic apparatus that can generate MRI image data, X-ray image data, and the like.

  In the above-described modification, the medical image diagnostic apparatus 200 having a function of generating PET image data has been described. However, as long as necessary information is input, other nuclear medicine such as SPECT image data and gamma image data is provided. It may be a medical image diagnostic apparatus capable of generating image data.

  On the other hand, the distribution data generation unit 43 of the radiation dose estimation unit 4 in the above-described embodiment and its modification is centered on the body model 151 of the subject 150 arranged on the top board 6 and is separated from the floor by a predetermined distance. Although the case where the two-dimensional radiation dose distribution data in the horizontal plane is generated has been described, the present invention is not limited to this. For example, the two-dimensional radiation dose distribution data in another cross section may be used. It may be quantity distribution data.

  Moreover, the case where the value of the external radiation dose in the predetermined calculation area calculated by the dose calculation unit 42 and the radiation dose distribution data generated by the distribution data generation unit 43 are displayed on the monitor of the display unit 5 (5a) has been described. However, it may be displayed on a display panel provided in the input unit 8 (8a) or a dedicated display unit provided separately. In this case, only one of the value of the external radiation dose or the radiation distribution data may be displayed, or these data may be displayed together with the X-ray CT image data and the PET image data.

  Furthermore, the body model used for calculating the radiation dose is set based on the weight information of the subject 150 included in the subject information. However, it is set based on other subject information such as age and height. It doesn't matter. The body model corresponding to the subject is set by the dose calculation unit 42 selecting from various body models stored in the body model storage unit 41 in advance. A body model setting unit that selects or generates a body model based on the specimen information may be provided independently of the dose calculation unit 42.

  In the above-described embodiment, when X-ray CT imaging and PET imaging are performed, the X-ray CT gantry 163 and the PET gantry 164 are moved in the body axis direction along the guide rail 162 as shown in FIG. As described above, the top plate 6 on which the subject 150 is placed may be moved in the body axis direction.

DESCRIPTION OF SYMBOLS 1 ... X-ray CT imaging | photography part 11 ... X-ray generation part 12 ... Projection data generation part 2 ... PET imaging part 21 ... Detector module 22 ... Detection data processing part 3, 3a ... Image data generation part 31, 31a ... Projection data storage Units 32, 32a ... reconstruction processing units 33, 33a ... attenuation correction data generation unit 4 ... radiation dose estimation unit 41 ... body shape model storage unit 42 ... dose calculation unit 43 ... distribution data generation unit 5, 5a ... display unit 6 ... sky Plate 7, 7a ... Movement mechanism unit 8, 8a ... Input unit 9, 9a ... System control unit 100, 200 ... Medical image diagnostic apparatus

Claims (11)

In a medical diagnostic imaging apparatus that detects γ rays emitted from a subject administered with a radioisotope, and generates image data based on the detection data,
A radiation dose estimating means for estimating a radiation dose emitted from the subject;
A medical image diagnostic apparatus comprising: a display unit configured to display a radiation dose estimation result by the radiation dose estimation unit.   The radiation dose estimation unit includes a dose calculation unit, and the dose calculation unit calculates a radiation dose in one or a plurality of regions set around the subject as an external radiation dose. The medical image diagnostic apparatus according to 1.   Body shape setting means for setting a body model corresponding to the subject is provided, and the dose calculation means calculates the extracorporeal radiation dose based on the administration information of the radioisotope distributed in the body model. The medical image diagnostic apparatus according to claim 2.   The said dose calculation means calculates the said external radiation dose by using at least the dose, the administration time and the half-life of the radioisotope administered to the subject as the administration drug information. Medical diagnostic imaging device.   The dose calculation means includes an in-vivo dose calculation means and an extracorporeal dose calculation means, and the in-vivo dose calculation means is based on the administered drug information of the radioisotope distributed inside the body model and is in the body of the subject. The radiation dose is continuously calculated, and the external dose calculation means calculates the external radiation dose around the subject based on the internal radiation dose calculated by the internal dose calculation means. The medical image diagnostic apparatus according to claim 3.   The radiation dose estimation means includes distribution data generation means, and the distribution data generation means generates two-dimensional or three-dimensional radiation dose distribution data based on the extracorporeal radiation dose in the plurality of regions calculated by the dose calculation means. The medical image diagnostic apparatus according to claim 2, wherein:   4. The medical image diagnostic apparatus according to claim 3, wherein the body model setting unit sets the body model based on subject information of the subject.   8. The medical image diagnosis according to claim 7, wherein the body model setting unit sets the body model based on at least one of a weight, a height, and an age of the subject included in the subject information. apparatus.   4. The medical image diagnostic apparatus according to claim 3, wherein the body model setting unit extracts a body model corresponding to the subject from various body models stored in advance based on the subject information.   The medical image diagnostic apparatus according to claim 1, wherein the display unit displays a radiation dose estimation result by the radiation dose estimation unit together with the image data. For a medical image diagnostic apparatus that detects γ-rays emitted from a subject administered with a radioisotope and generates image data based on the detection data,
A body model setting function for setting a body model based on the subject information of the subject;
A radiation dose estimation function for estimating a radiation dose around the subject based on the radioisotope distributed inside the body model;
A radiation dose calculation control program for executing a display function for displaying the radiation dose estimation result.

Images