JP2012147949A - X-ray ct apparatus, and control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate high S/N image data based on projection data collected by synchronous photography.SOLUTION: An X-ray CT apparatus 100 for generating image data based on a projection data of an object to be tested collected by synchronous photography using a biological signal includes: an input section 10 for setting a topological section in the biological signal; a data synthesizing section 42 for generating high S/N image data having high S/N by adding and synthesis processing of a plurality of the image data corresponding to a different time including the topological section; and a display section 5 for displaying the high S/N image data.

Description

  Embodiments of the present invention generate image data having a high S / N based on time-series image data collected by X-ray CT imaging in a synchronous imaging mode using an electrocardiogram waveform, a respiratory waveform, and the like. The present invention relates to an X-ray CT apparatus and a control program.

  Medical image diagnosis has made rapid progress with an X-ray CT apparatus and the like put into practical use with the development of computer technology, and is indispensable in today's medical care. In particular, in recent X-ray CT apparatuses, an X-ray tube and an X-ray detector arranged opposite to each other around a patient or a test subject (hereinafter referred to as a subject) are rotated at a high speed and the subject is removed. Image data and three-dimensional data (multi-slice cross-sections) are obtained by practical use of a so-called helical scan method that collects projection data in a plurality of slice cross-sections by continuously moving in the body axis direction and reconstructs the projection data. Volume data) is generated in a short time. In addition, the time required for collecting projection data in a three-dimensional region has been further shortened by applying the multi-slice method, which is made possible by using an X-ray detection unit in which minute detection elements are two-dimensionally arranged.

  On the other hand, when collecting a wide range of image data and volume data in the body axis direction of the subject using the above-described helical scan method or multi-slice method, in order to eliminate the effects of organ pulsatile movement and respiratory movement ECG-synchronized imaging (ECG-synchronized scanning) and respiratory-synchronized imaging (respiratory-synchronized scanning) that collects image data based on the ECG waveform and respiratory waveform of the subject measured in parallel with the collection of projection data It is done.

JP 2010-046212 A

  By applying the above-mentioned electrocardiogram synchronization method and respiratory synchronization imaging method, it is possible to collect high-quality image data and volume data that are not affected by pulsatile movement and respiratory movement in a wide area in the body axis direction. Become. However, in such electrocardiogram synchronous imaging and respiratory synchronous imaging, it is necessary to perform X-ray irradiation on a subject for a long time. For this reason, it is important to suppress the increase in the exposure dose to the subject by reducing the irradiation dose in one X-ray irradiation as much as possible. However, the noise mixed in the projection data or the like is relatively reduced due to the reduction in the irradiation dose. In other words, it is difficult to obtain high-quality image data and volume data.

  The present disclosure has been made in view of the above-described problems, and a purpose thereof is a time-series image of a predetermined phase section collected by synchronous imaging using a biological signal such as a respiratory waveform or an electrocardiographic waveform. To provide an X-ray CT apparatus and a control program capable of generating image data having a high S / N (hereinafter referred to as high S / N image data) by performing an additive synthesis process on the data. is there.

  In order to solve the above-described problem, an X-ray CT apparatus according to the present disclosure is an X-ray CT apparatus that generates image data based on projection data of a subject collected by synchronous imaging using a biological signal. A phase interval setting means for setting a phase interval in the image and a high S / N ratio by adding and combining a plurality of the image data corresponding to different times included in the phase interval set by the phase interval setting means A data synthesizing unit that generates high S / N image data and a display unit that displays the high S / N image data are provided.

1 is a block diagram showing the overall configuration of an X-ray CT apparatus in the present embodiment. The figure for demonstrating the X-ray detection part with which the projection data generation part of this embodiment is provided. The figure for demonstrating "data bundling" in the projection data generation part of this embodiment. The figure which shows the imaging position, image data thickness, and image data space | interval of image data by the "data bundling" of this embodiment. The block diagram which shows the specific structure of the data synthetic | combination part with which the image data generation part of this embodiment is provided. The figure which shows the specific example of the weighting function used for the weighting addition synthetic | combination process of this embodiment. The figure for demonstrating the setting of the addition synthetic | combination phase area in this embodiment, and the weighted addition synthetic | combination process of the image data collected in this addition synthetic | combination phase area. The figure which shows the specific setting method of the addition synthetic | combination phase area with respect to the biomedical signal displayed on the display part of this embodiment. 6 is a flowchart showing a procedure for generating high S / N image data in the present embodiment. The block diagram which shows the whole structure of the X-ray CT apparatus in the modification of this embodiment. The figure for demonstrating the setting method of the addition synthetic | combination phase area in the modification of this embodiment.

  Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

  In the X-ray CT apparatus of the present embodiment described below, first, an addition synthesis start phase and an addition synthesis end phase are set based on a respiratory waveform measured from a subject. Next, a phase interval (addition synthesis phase interval) set by the above-described addition synthesis start phase and addition synthesis end phase from time-series image data collected by X-ray CT imaging in the respiratory synchronization imaging mode for the subject. A high S / N image data having a high S / N is generated by adding and synthesizing a plurality of image data corresponding to different times (phases) included in.

  In the embodiment described below, the respiration waveform of the subject is measured in parallel with the X-ray CT imaging of the subject, and a predetermined phase interval (added synthesized phase interval) collected in time series by the X-ray CT imaging. ) Will be described. However, the above-described addition synthesis processing may be performed based on the phase information of the electrocardiogram waveform measured from the subject instead of the respiratory waveform.

(Device configuration)
The configuration and function of the X-ray CT apparatus according to the embodiment of the present disclosure will be described with reference to FIGS. FIG. 1 is a block diagram showing the overall configuration of the X-ray CT apparatus in the present embodiment, and FIG. 5 shows a specific configuration of a data synthesis unit included in the image data generation unit of the X-ray CT apparatus. It is a block diagram.

  An X-ray CT apparatus 100 shown in FIG. 1 includes an X-ray irradiation control unit 1 that generates an irradiation control signal based on an X-ray irradiation condition of a scan parameter supplied from an input unit 10 described later, and the X-ray irradiation control unit. An X-ray generator 2 that irradiates the subject 150 with X-rays according to the irradiation control signal supplied from 1, a projection data generator 3 that detects X-rays transmitted through the subject 150 and generates projection data; A plurality of time-series image data are generated by reconstructing projection data in a predetermined respiratory phase interval (additional synthesis phase interval) extracted from the projection data generated by the projection data generation unit 3, and These image data are added and synthesized to generate high S / N image data having a high S / N, and the high S / N image data generated by the image data generation unit 4. And a display unit 5 for displaying the respiration waveform, etc. have been the subject 150 measured by the data and later of the biological signal measurement section 11.

  In addition, the X-ray CT apparatus 100 includes a part of the X-ray generation unit 2 and the projection data generation unit 3 and rotates at a predetermined speed around the subject 150 at a predetermined speed, and an upper surface of a bed (not shown). A top plate 8 that is slidably mounted on the subject 150 and moves in the body axis direction (z direction in FIG. 1), and movement of the top plate 8 based on scan parameters supplied from the input unit 10 A moving mechanism unit 9 that performs high-speed rotation of the rotating gantry unit 6; and further, selection of an imaging mode, setting of scan parameters, setting of reconstruction parameters including addition synthesis conditions, selection of weighting functions, input of subject information, An input unit 10 that inputs various instruction signals, a biological signal measurement unit 11 that measures the respiratory waveform of the subject 180, and a system control unit 13 that controls the above-mentioned units in an integrated manner are provided.

  Note that, as scan parameters that are initially set in the input unit 10 described above, an imaging position (a position in the slice direction (z direction) where image data and high S / N image data are collected), an imaging position interval, and a high S / N There are the number of image data, image data thickness (slice thickness of image data), X-ray irradiation conditions such as tube voltage and tube current, and the rotation speed of the rotating gantry 6. As reconstruction parameters, there are a reconstruction method, a reconstruction area size, a reconstruction matrix size, an addition composition condition, and the like. The addition composition condition includes a phase section (addition composition phase section) of image data used for addition composition processing. Alternatively, the addition / combination start phase and the addition / combination end phase for determining the phase interval and the phase interval of image reconstruction are included.

  Next, the configuration and function of each of the units included in the X-ray CT apparatus 100 will be described in more detail.

  The X-ray irradiation control unit 1 shown in FIG. 1 receives imaging mode selection information and scan parameters supplied from the input unit 10 via the system control unit 13, and receives the X-ray irradiation conditions included in the scan parameters. An irradiation control signal generated based on the imaging mode selection information is supplied to the X-ray generator 2. For example, when the respiratory synchronization imaging mode is selected in the input unit 10, the X-ray irradiation control unit 1 performs irradiation control corresponding to the low exposure dose based on the selection information of the respiratory synchronization imaging mode supplied from the system control unit 13. Generate a signal.

  Next, the X-ray generator 2 includes an X-ray tube 21 that irradiates the subject 150 with X-rays, and a high voltage generator 22 that generates a high voltage to be applied between the anode / cathode of the X-ray tube 21. The X-ray diaphragm unit (collimator) 23 for setting the irradiation range of the X-rays emitted from the X-ray tube 21 to the subject 150 and the high voltage generated by the high voltage generation unit 22 are provided in the rotary mount unit 6. A slip ring 24 for supplying to the X-ray tube 21 is provided.

  The X-ray tube 21 is a vacuum tube that generates X-rays, and collides electrons accelerated by a high voltage supplied by the high-voltage generation unit 22 based on an irradiation control signal in the breathing synchronization imaging mode with a tungsten target. Radiate. The X-ray diaphragm 23 is provided between the X-ray tube 21 and the subject 150, has a function of narrowing X-rays emitted from the X-ray tube 21 to a predetermined irradiation range, and an X-ray irradiation intensity distribution with respect to the irradiation range. Has a function to set. For example, the X-ray beam emitted from the X-ray tube 21 is shaped into a cone beam-like or fan-beam-like X-ray beam corresponding to the imaging region.

  On the other hand, the projection data generation unit 3 includes an X-ray detection unit 31 that detects X-rays transmitted through the subject 150, and a switch that bundles a plurality of channels of detection signals output from the X-ray detection unit 31 into a predetermined number of channels. A group 32 and a data acquisition unit (hereinafter referred to as a DAS (Data Acquisition System) unit) that generates projection data by performing current / voltage conversion and A / D conversion on detection signals of a plurality of channels output from the switch group 32. 33), a data transmission unit 34 for performing parallel / serial conversion, electrical / optical / electrical conversion and serial / parallel conversion on the projection data output from the DAS unit 33, and a projection output from the data transmission unit 34 A projection data storage unit 35 for storing data is provided.

  Next, the X-ray detection unit 31 of the projection data generation unit 3 will be described with reference to FIG. FIG. 2 is a development view of the X-ray detection unit 31 in which minute detection elements 311 are two-dimensionally arranged. Each of the detection elements 311 includes a scintillator that converts irradiated X-rays into light, It is composed of a photodiode that converts this light into an electrical signal.

  That is, the X-ray detection unit 31 includes a plurality (N1) of slices (z direction) that is the body axis direction of the subject 150 and a channel direction (x direction) orthogonal to the slice direction. A plurality (N2) of detection elements 311 are two-dimensionally arranged. However, the detection elements 311 arranged in the channel direction are actually attached to the rotating gantry 6 along an arc centered on the focal point of the X-ray tube 21. Then, for example, N11 detection elements 311 are arranged at intervals of 0.5 mm in the central portion of the slice direction in the X-ray detection unit 31, and N12 detection elements 311 are provided at both ends of the N11 detection elements 311. They are arranged at intervals of 1.0 mm.

  Returning to FIG. 1, the switch group 32 of the projection data generation unit 3 includes a multiplexer (not shown), and when the detection signal from the X-ray detection unit 31 is supplied to the DAS unit 33, if necessary (set scan is set). The detection signals of a plurality of channels in the slice direction output from the detection element 311 (in accordance with parameters) are “data bundled” to the number of channels M corresponding to imaging positions S1 to SM described later, and supplied to the DAS unit 33.

  The DAS unit 33 has an M channel receiving unit (not shown), and performs current / voltage conversion and A / D conversion on the detection signal supplied from the X-ray detection unit 31 to generate M channel projection data. To do. On the other hand, the data transmission unit 34 includes a parallel / serial converter (not shown), an electrical / optical / electrical converter, and a serial / parallel converter, and the M-channel projection data output from the DAS unit 33 is a rotating gantry unit. 6 is converted to time-series 1-channel projection data by the parallel / serial converter provided in 6 and serial / parallel conversion provided in the fixed gantry 7 by optical communication using the electrical / optical / electrical converter. Supplied to the vessel.

  Next, the 1-channel projection data is returned to the M-channel projection data by the above-described serial / parallel converter, and the M-channel projection data obtained in time series includes the array position information and rotation of the detection elements 311 in the channel direction. The angle information, the position information (imaging position) of the projection data in the slice direction, and the phase information of the respiratory waveform supplied from the biological signal measurement unit 11 are stored in the projection data storage unit 35 as supplementary information.

  It should be noted that the data transmission method by the data transmission unit 34 is another method as long as data transmission between the DAS unit 33 provided in the rotating gantry unit 6 and the projection data storage unit 35 provided in the fixed gantry unit 7 is possible. For example, a device such as the slip ring described above may be used.

  The X-ray tube 21 and the X-ray diaphragm 23 of the X-ray generator 2 and a part of the projection data generator 3 are mounted on the rotating gantry 6 so as to face each other with the subject 150 interposed therebetween, and the moving mechanism unit For example, a continuous movement at a speed of 1 rotation / second to 2 rotations / second with an axis parallel to the body axis direction (z direction) of the subject 150 as a center of rotation is performed by a later-described top plate / base movement mechanism 91. Rotate.

  Next, “data bundling” in the above-described projection data generation unit 3 will be described with reference to FIG. However, FIG. 3 describes a case where twelve detection elements 311-1 to 311-12 are arranged in the slice direction for the sake of simplicity.

  That is, in the X-ray detection unit 31 illustrated in FIG. 3, for example, eight detection elements 311-3 to 311-10 are arranged at intervals of 0.5 mm in the central portion in the slice direction, The detection elements 311-1 and 311-2 and the detection elements 311-11 and 311-12 are arranged at 1 mm intervals.

  On the other hand, the DAS unit 33 includes, for example, M = 8 channel current / voltage converters 331-1 to 331-M and A / D converters 332-1 to 332-M, and the switch group 32 including a multiplexer includes: The detection signals of 12 channels obtained by the detection elements 311-1 to 311-12 are “data bundled” into 8 channels. Such “data bundling” makes it possible to set the photographing position, the image data thickness (slice thickness), the image data interval, and the like in a multi-slice scan to a desired size.

  For example, a 0.5 mm slice is obtained by connecting the detection elements 311-3 to 311-10 to the current / voltage converters 331-1 to 331-M (M = 8) of the DAS unit 33 through the switch group 32. Image data having a thickness can be collected at M imaging positions. On the other hand, when image data having an image data thickness of 1 mm is required, the detection element 311-1 is a current / voltage converter 331-1, the detection element 311-2 is a current / voltage converter 331-2, The detection elements 311-3 and 311-4 are connected to the current / voltage converter 331-3, the detection elements 311-5 and 311-6 are connected to the current / voltage converter 331-4, and the detection elements 311-7 and 311 are connected. −8 is the current / voltage converter 331-5, the detection elements 311-9 and 311-10 are the current / voltage converter 331-6, the detection element 311-11 is the current / voltage converter 331-7, and the detection element 311− 12 to the current / voltage converter 331-M.

  By such “data bundling”, it is possible to cope with both cases where a narrow area is imaged with high resolution and where a wide area is imaged with high S / N. FIG. 4 shows the image data thickness Iw and the image data interval Δd of the image data D1 to DM generated by the multi-slice scan of the present embodiment to which the above “data bundling” is applied, and the photographing position S1 of the image data D1 to DM. To SM, and these values are initially set in the input unit 10 as scan parameters.

  Next, the image data generation unit 4 shown in FIG. 1 includes a reconstruction processing unit 41 and a data synthesis unit 42, and reconstructs projection data collected in a predetermined respiratory phase interval (additional synthesis phase interval) of the imaging positions S1 to SM. It has a function of generating a plurality of time-series image data by configuration processing and a function of generating high S / N image data by weighting and adding these image data.

  In the following, a plurality of time-series image data is generated based on the projection data of the photographing position S1 collected in a preset addition synthesis phase section for the sake of simplicity, and these image data A case of performing weighted addition synthesis processing will be described.

  That is, the reconstruction processing unit 41 of the image data generating unit 4 includes a program storage unit and an arithmetic processing unit (not shown), and various arithmetic processing programs used for projection data reconstruction processing are stored in the program storage unit in advance. Yes. On the other hand, the arithmetic processing unit first extracts an arithmetic processing program corresponding to the reconstruction method of the reconstruction parameter preset in the input unit 10 from various arithmetic processing programs stored in the program storage unit, and then Based on the incidental information added to the projection data, the projection data of the photographing position S1 collected in the addition synthesis phase section from the projection data stored in the projection data storage unit 35 of the projection data generation unit 3 is used. read out. Then, the obtained projection data is reconstructed by using the above-described arithmetic processing program, thereby generating a plurality of time-series image data in the addition synthesis phase section at a predetermined reconstruction phase interval.

  Next, the data synthesis unit 42 of the image data generation unit 4 includes an image data storage unit 421, a weighting function storage unit 422, and an addition synthesis processing unit 423 as shown in FIG. The image data in the addition synthesis phase section is temporarily stored in the image data storage unit 421 using the respiratory phase as supplementary information. On the other hand, in the weighting function storage unit 422, for example, as shown in FIG. 6A to FIG. 6D, the weighting coefficient value is the maximum value in the central portion Pxo and has various widths (phase intervals) of ΔPa. A weighting function is stored in advance.

  Based on the weighting function selection information supplied from the input unit 10, the addition / synthesis processing unit 423 is a weighting suitable for the addition / synthesis processing from among the various weighting functions stored in the weighting function storage unit 422. Extract a function. Then, high S / N image data Dx1 having high S / N is generated by performing weighted addition synthesis processing on the plurality of image data read from the image data storage unit 421 using the extracted weighting function.

  The weighted addition synthesis process performed by the above-described addition synthesis processing unit 423 will be described with reference to FIG. FIG. 7A shows weighted addition synthesis processing performed on the image data D1-a1 to D1-aQ based on the projection data collected in the addition synthesis phase interval ΔP. Based on the respiration waveform Re measured from the subject 150, the input unit 10 determines the addition synthesis start phase Ps and the addition synthesis end phase Pe set in advance. For example, the addition synthesis phase interval ΔP is set by the addition synthesis start phase Ps indicating the front end portion of the phase interval whose change is relatively small in the respiratory waveform Re and the addition synthesis end phase Pe indicating the rear end portion.

  FIG. 7B shows the projection data B1-1 to B1-K of the imaging position S1 collected in the respiratory phases P1 to PK indicating the respiratory cycle of the subject 150, and the projection data B1 of the addition combined phase section ΔP. The image data D1-a1 to D1-aQ obtained by reconstructing -a1 to B1-aQ are shown, and the phase interval ΔPb of the image reconstruction with respect to the image data D1-a1 to D1-aQ is the projection data It is set to an integral multiple of the phase interval ΔPc between B1-1 to B1-K.

  On the other hand, FIG. 7C shows the weighting function Rw extracted from the weighting function storage unit 422 based on the weighting function selection information supplied from the input unit 10, and the phase interval ΔPa is the addition synthesis phase interval ΔP. Image data D1-a1 to D1-aQ by multiplying the coefficient of the weighting function Rw whose phase interval has been enlarged / reduced to be equal to the pixel value of the image data D1-a1 to D1-aQ. Is weighted. Next, high S / N image data Dx1 (not shown) is generated by adding and synthesizing the weighted image data D1-a1 to D1-aQ.

  6 and 7, the weighted addition synthesis process has been described. However, a simple addition synthesis process or an addition averaging (averaging) process may be used. When the respiration cycle is 3000 msec (100%), the addition synthesis start phase Ps is set to 1500 msec (50%), for example, and the addition synthesis end phase Pe is set to 1800 msec (60%). In this case, the addition / combination start phase Ps and the addition / combination end phase Pe may be set in units of msec as described above, or may be set as a percentage with the respiratory cycle being 100%.

  The case where the high S / N image data Dx1 is generated based on the time-series image data D1-1 to D1-K collected at the photographing position S1 has been described above, but the high S / N at the photographing positions S2 to SM has been described. N image data Dx2 to DxM are also generated by the same procedure.

  Next, the display unit 5 illustrated in FIG. 1 includes a display data generation unit, a conversion processing unit, and a monitor (not shown), and the high S / N image data Dx1 to DxM generated by the data synthesis unit 42 of the image data generation unit 4. And a function of displaying a respiratory waveform of the subject 150 measured by the biological signal measuring unit 11. In particular, when displaying the high S / N image data Dx1 to DxM, the display data generation unit performs the subject information of the subject 180, the scan parameters, and the like on the high S / N image data supplied from the data synthesis unit 42. Display data is generated by adding reconstruction parameters and the like as necessary. Then, the conversion processing unit performs conversion processing such as D / A conversion and television format conversion on the display data described above and displays it on the monitor.

  FIG. 8 shows the respiration waveform Re of the subject displayed on the display unit 5, the marker Ms of the addition synthesis start phase Ps that determines the addition synthesis phase section set for the respiration waveform Re, and the addition synthesis end phase Pe. Further, the marker Me is shown, and further, the respiratory cycle PK (= 3000 msec), the addition synthesis start phase Ps (= 1500 msec), the addition synthesis end phase Pe (= 1800 msec), the phase interval ΔPb (= 20 msec) of image reconstruction, and the like An addition synthesis condition display field Ax or the like indicated by is added as necessary.

  The moving mechanism unit 9 includes a top / pedestal moving mechanism unit 91 and a mechanism control unit 92. The couchtop / pedestal moving mechanism unit 91 is configured so that the rotating gantry unit 6 on which the X-ray tube 21 and the projection data generating unit 3 are mounted is predetermined around the subject 150 in accordance with the gantry rotation control signal supplied from the mechanism control unit 92. The top plate 8 on which the subject 150 is placed is slid in the body axis direction according to a top plate movement control signal supplied from the mechanism control unit 92 in the same manner.

  On the other hand, the mechanism control unit 92 generates a gantry rotation control signal and a top plate movement control signal based on the gantry rotation instruction signal and the top plate movement instruction signal supplied from the input unit 10, and uses these obtained control signals. By supplying to the top plate / base movement mechanism 91, the rotation base 6 is rotated and the top 8 is moved.

  Next, the input unit 10 includes input devices such as a display panel, a keyboard, various switches, and a mouse, and forms an interactive interface when used in combination with the display unit 5. It has functions for selecting a breathing synchronization imaging mode and a normal imaging mode, setting scan parameters, setting reconstruction parameters including addition synthesis conditions, selecting a weighting function, and the like. Also, setting of image data display conditions, input of object information, input of various instruction signals, etc. are performed by the above-described display panel and input device.

  The biological signal measuring unit 11 detects the position information of the chest body surface that changes with breathing as a respiratory waveform (see FIG. 7A), and converts the detected respiratory waveform into a digital signal. An A / D converter (both not shown) is provided. However, when measuring the electrocardiogram waveform and the respiration waveform, the impedance of the chest tissue may be measured using an electrode for electrocardiogram waveform measurement (not shown), and the respiration waveform may be estimated based on this impedance.

  The system control unit 13 includes a storage circuit (not shown) and a CPU, and the above-described input information, setting information, and selection information supplied from the input unit 10 are stored in the storage circuit. On the other hand, the CPU is based on the above-mentioned input information, setting information, and selection information stored in the storage circuit, the irradiation condition control unit 1, the projection data generation unit 3, the image data generation unit 4, the display unit 5, and the movement mechanism unit 9. Etc. are controlled in an integrated manner to generate high S / N image data based on the image data collected in the addition / synthesis phase section in which the change of the respiratory waveform is relatively small.

(Procedure for generating high S / N image data)
Next, a procedure for generating high S / N image data in the present embodiment will be described with reference to the flowchart of FIG. Prior to the X-ray CT imaging of the subject 150, the operator of the X-ray CT apparatus 100 inputs the subject information at the input unit 10, and further selects the respiratory synchronization imaging mode and scan parameters (imaging positions S1 to SM, imaging). Position interval Δd, high S / N number of image data M, image data thickness Iw, tube voltage and tube current, rotation speed of rotating gantry 6 and the like, and reconstruction parameters (reconstruction method, reconstruction region size, reconstruction matrix) Setting of size, addition synthesis condition, etc.), selection of weighting function, setting of image data display condition, and the like. These pieces of information are temporarily stored in the storage circuit of the system control unit 13 (step S1 in FIG. 9).

  The addition synthesis start phase Ps and the addition synthesis end phase Pe included in the above-described addition synthesis conditions are usually set based on the respiratory waveform of the subject 180 measured by the biological signal measurement unit 11 and displayed on the display unit 5. The imaging positions S1 to SM of the image data included in the scan parameters, the imaging position interval Δd, the number of high S / N image data M, the image data thickness Iw, and the like are based on scanograms of the subject 180 collected in advance. Is set. When the above initial setting is completed, the operator moves the top 8 on which the subject 150 is placed to a predetermined position, and then inputs an imaging start instruction signal at the input unit 10 (FIG. 9 step S2).

  On the other hand, the X-ray irradiation control unit 1 that has received the X-ray irradiation conditions included in the above-described imaging start instruction signal, imaging mode selection information, and scan parameters via the system control unit 13 is based on these information. The generated irradiation control signal is supplied to the high voltage generation unit 22 of the X-ray generation unit 2, and the high voltage generation unit 22 supplies power (tube voltage and tube current) necessary for X-ray irradiation in the breathing synchronization imaging mode to X-rays. By supplying to the tube 21, the subject 150 is irradiated with X-rays. Then, the X-ray irradiated from the X-ray tube 21 and transmitted through the subject 150 is converted into a charge (current) signal proportional to the transmitted dose in the X-ray detection unit 31 of the projection data generation unit 3, and is transmitted via the switch group 32. To the DAS unit 33.

  Next, the DAS unit 33 performs current / voltage conversion and A / D conversion on the current signal to generate M-channel time-series projection data, and the obtained projection data of the photographing positions S1 to S1 are: Additional information such as array position information and rotation angle information of the detection element 311 in the channel direction, position information (imaging position information) of projection data in the slice direction, and phase information of the respiratory waveform supplied from the biological signal measurement unit 11 Is stored in the projection data storage unit 35 (step S3 in FIG. 9).

  On the other hand, the reconstruction processing unit 41 of the image data generation unit 4 reads out an arithmetic processing program corresponding to the reconstruction parameter set in step S1 described above from its own program storage unit, and is further supplied from the input unit 10. Projection data in the addition synthesis phase section ΔP set by the information of the addition synthesis start phase Ps and the addition synthesis end phase Pe is read from the projection data storage unit 35. Then, the projection data is reconstructed using the above-described arithmetic processing program, whereby the image data Dm-a1 to Dm-aQ (m = 1 to M) in the addition synthesis phase section ΔP are reconstructed in a predetermined image. The data is generated at the phase interval ΔPb and temporarily stored in the image data storage unit 421 of the data synthesis unit 42 (step S4 in FIG. 9).

  Next, the addition synthesis processing unit 423 of the data synthesis unit 42 reads the above-described image data Dm-a1 to Dm-aQ stored in the image data storage unit 421 and selects a weighting function supplied from the input unit 10. High S / N image data Dxm (m = 1 to M) is generated by performing weighted addition synthesis processing of the image data Dm-a1 to Dm-aQ using the weighting function extracted from the weighting function storage unit 422 based on the information. (Step S5 in FIG. 9). Then, all or a part of the obtained high S / N image data Dxm is displayed on the display unit 5 (step S6 in FIG. 9).

(Modification)
Next, a modification of the present embodiment will be described with reference to FIGS. FIG. 10 is a block diagram showing the overall configuration of the X-ray CT apparatus 200 in the present modification. Differences from the X-ray CT apparatus 100 in the above-described embodiment shown in FIG. A phase interval setting unit 12 that automatically sets the addition synthesis phase interval ΔP based on the breathing waveform to be performed. In FIG. 10, units having the same configuration and function as those of the unit shown in FIG.

  That is, the X-ray CT apparatus 200 of the present modification shown in FIG. 10 includes an X-ray irradiation control unit 1 that generates an irradiation control signal based on an X-ray irradiation condition of a scan parameter supplied from an input unit 10a described later, An X-ray generation unit 2 that irradiates the subject 150 with X-rays according to the irradiation control signal supplied from the X-ray irradiation control unit 1, and a projection that generates projection data by detecting the X-rays transmitted through the subject 150 The data generation unit 3 and the projection data in the addition synthesis phase section generated by the projection data generation unit 3 are reconstructed to generate time-series image data, and these image data are added and synthesized to increase the S An image data generation unit 4 that generates high S / N image data having / N and a display unit 5a that displays the high S / N image data generated by the image data generation unit 4 are provided.

  The X-ray CT apparatus 200 includes a part of the X-ray generation unit 2 and the projection data generation unit 3 and rotates at a predetermined speed around the subject 150 at a predetermined speed, and an upper surface of a bed (not shown). A top plate 8 that is slidably mounted on the subject 150 and moves in the body axis direction (z direction in FIG. 8), and the movement of the top plate 8 based on the scan parameters supplied from the input unit 10a A moving mechanism unit 9 that performs high-speed rotation of the rotating gantry unit 6; and further, selection of an imaging mode, setting of scan parameters, setting of reconstruction parameters including addition synthesis conditions, selection of weighting functions, input of subject information, An input unit 10a for inputting various instruction signals, a biological signal measuring unit 11 for measuring a respiration waveform of the subject 180, a phase interval setting unit 12 for setting the above-described addition synthesis phase interval based on this respiration waveform, and , And a system control unit 13a that collectively controls each unit of the predicate.

  The display unit 5a includes a display data generation unit, a conversion processing unit, and a monitor (not shown), and has a function of displaying the high S / N image data Dx1 to DxM generated in the data synthesis unit 42 of the image data generation unit 4. Have. That is, the display data generation unit adds the subject information, scan parameters, reconstruction parameters, and the like of the subject 180 to the high S / N image data supplied from the data synthesis unit 42 as necessary. Is generated. Then, the conversion processing unit performs conversion processing such as D / A conversion and television format conversion on the display data described above and displays it on the monitor.

  The input unit 10a includes input devices such as a display panel, a keyboard, various switches, and a mouse, and forms an interactive interface when used in combination with the display unit 5a. It has functions for selecting a breathing synchronization imaging mode and a normal imaging mode, setting scan parameters, setting reconstruction parameters including addition synthesis conditions, selecting a weighting function, and the like. Also, setting of image data display conditions, input of object information, input of various instruction signals, etc. are performed by the above-described display panel and input device.

  On the other hand, the phase interval setting unit 12 is configured to detect, as a reference phase, a respiration phase having a minimum change rate in the respiration waveform, and a respiration waveform value of the reference phase by setting a threshold value for the respiration waveform. On the other hand, a threshold value setting unit (none of which is shown) is provided that sets a phase section of a respiratory waveform having a displacement amount within a predetermined range as an addition synthesis phase section.

  The additive synthesis phase interval automatically set by the above-described phase interval setting unit 12 will be described with reference to FIG. 11 is set based on the respiration waveform Re shown in FIG. 11, the reference phase detection unit of the phase interval setting unit 12 performs, for example, the respiration waveform Re supplied from the biological signal measurement unit 11. Differentiation is performed, and the respiratory phase whose absolute value is zero or minimum is detected as the reference phase Po. Next, the threshold value setting unit of the phase interval setting unit 12 sets a threshold value Δα based on the respiratory waveform value αo in the reference phase Po, and is based on the respiratory phase Ps and the respiratory phase Pe at which the threshold value Δα and the respiratory waveform Re intersect. To set the addition synthesis phase section ΔP.

  Next, the system control unit 13a shown in FIG. 9 includes a storage circuit and a CPU (not shown), and the input information, setting information, and selection information supplied from the input unit 10a are stored in the storage circuit. On the other hand, the CPU is based on the above-described input information, setting information, and selection information stored in the storage circuit, the irradiation condition control unit 1, the projection data generation unit 3, the image data generation unit 4, the display unit 5a, and the movement mechanism unit 9. In addition, each unit such as the phase interval setting unit 12 is comprehensively controlled to generate high S / N image data based on the image data collected in the addition synthesis phase interval ΔP in which the change in the respiratory waveform is relatively small. .

  According to the present embodiment described above, the image data in the addition synthesis phase section with little respiratory movement extracted from the time-series image data collected by the respiratory synchronization imaging using the X-ray CT apparatus is added and synthesized. By processing, high S / N image data D having high S / N can be generated. In particular, it is possible to further reduce the influence of respiratory movement by performing weighted addition synthesis processing on the plurality of image data collected in the addition synthesis phase interval.

  On the other hand, according to the above-described modification, the above-described addition / synthesis phase section is automatically set based on the respiration waveform obtained from the subject, so that it is suitable for any respiration waveform. Can be set easily. For this reason, it is possible to always obtain high-quality high S / N image data with high diagnostic ability, and the automatic setting of the addition / synthesis phase section not only improves the examination efficiency in the X-ray CT examination but also the operation. The burden on the person is greatly reduced.

  As mentioned above, although embodiment of this indication and its modification were described, this indication is not limited to the above-mentioned embodiment and its modification, and it can change and implement it further. For example, in the above-described embodiment and its modified example, the respiration waveform of the subject 150 is measured in parallel with the X-ray CT imaging of the subject 150, and additive synthesis is less affected by the respiratory movement set based on the respiration waveform. Although the case where the phase interval is set has been described, the addition / synthesis phase interval may be set based on another biological signal such as an electrocardiogram waveform instead of the respiratory waveform.

  Further, the case where the high S / N image data Dxm is generated by adding and synthesizing the image data Dm-a1 to Dm-aQ in one addition cycle phase ΔP of one breathing cycle has been described. High S / N image data may be generated by adding and synthesizing image data collected in the synthesis phase interval.

  Further, the time-series image data Dm-a1 to Dm-aQ (m = 1 to M) in the addition synthesis phase section of the imaging positions S1 to SM collected by the multi-slice scanning X-ray CT imaging of the subject. Although the case where high S / N image data Dxm is generated based on the above is described, the present invention is not limited to this, and time-series image data collected by multi-helical scan type or single scan type X-ray CT imaging. The high S / N image data may be generated based on the above.

  Further, the case where all or part of the high S / N image data Dxm at the photographing positions S1 to SM is displayed as it is on the display unit 5 (5a) has been described. 3D data), 3D image data, MPR (multi-planar reconstruction) image data, MIP (maximum intensity projection) image data, etc. generated by performing predetermined processing on the volume data may be displayed. Absent.

  In addition, when there is a significant positional shift due to respiratory movement between image data collected at different respiratory phases, the above-mentioned processing is performed by performing inter-image processing such as cross-correlation on these image data. May be detected, and weighted addition synthesis processing may be performed on the image data that has been corrected for positional deviation based on the detection result. By applying this method, it becomes possible to add and synthesize image data in a wide range of addition and synthesis phase sections, so that high S / N image data having a higher S / N can be obtained.

  On the other hand, in the above-described embodiment, the case where the addition synthesis start phase Ps and the addition synthesis end phase Pe are set based on the respiratory waveform measured by the biological signal measurement unit 11 and displayed on the display unit 5 has been described. The setting of the start phase Ps and the addition / composition end phase Pe may be performed based on past inspection results, operator experience, and the like.

  Moreover, although the weighted addition synthesis process has been described as the image data addition synthesis process, a simple addition synthesis process or an addition averaging (averaging) process may be used.

  Note that part of the X-ray CT apparatus 100 or the X-ray CT apparatus 200 according to the embodiment of the present disclosure can also be realized by using a computer as hardware. For example, the system control unit 13 (13a) or the like can realize various functions by causing a processor such as a CPU mounted on the above-described computer to execute a predetermined control program. In this case, the system control unit 13 (13a) or the like may install the above-described control program in a computer in advance, or may be stored in a storage medium that can be read by the computer or distributed via a network. It may be installed on a computer.

  Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... X-ray irradiation control part 2 ... X-ray generation part 21 ... X-ray tube 22 ... High voltage generation part 23 ... X-ray aperture part 24 ... Slip ring 3 ... Projection data generation part 31 ... X-ray detection part 32 ... Switch group 33 ... DAS unit 34 ... data transmission unit 35 ... projection data storage unit 4 ... image data generation unit 41 ... reconstruction processing unit 42 ... data synthesis unit 421 ... image data storage unit 422 ... weighting function storage unit 423 ... addition synthesis processing unit 5, 5a ... Display unit 6 ... Rotating gantry unit 7 ... Fixed gantry unit 8 ... Top plate 9 ... Moving mechanism unit 91 ... Top plate / pedestal moving mechanism unit 92 ... Mechanism control unit 10, 10a ... Input unit 11 ... Biosignal measurement Unit 12: Phase section setting unit 13, 13a ... System control unit 100, 200 ... X-ray CT apparatus

Claims (11)

In an X-ray CT apparatus that generates image data based on projection data of a subject collected by synchronous imaging using a biological signal, a phase interval setting unit that sets a phase interval in the biological signal;
Data synthesizing means for generating high S / N image data having a high S / N by adding and synthesizing a plurality of the image data corresponding to different times included in the phase interval set by the phase interval setting means When,
An X-ray CT apparatus comprising: display means for displaying the high S / N image data.   The X-ray CT apparatus according to claim 1, further comprising a biological signal measuring unit, wherein the biological signal measuring unit measures at least one of a respiratory waveform or an electrocardiographic waveform of the subject as the biological signal.   2. The X-ray CT according to claim 1, wherein the data synthesizing unit generates the high S / N image data by performing a weighted addition synthesis process on the plurality of image data collected in the phase section. apparatus.   The data synthesis means generates the high S / N image data at the imaging position based on the image data of the phase interval collected at each of a plurality of imaging positions set in the body axis direction of the subject. The X-ray CT apparatus according to claim 1, wherein:   The data synthesizing unit generates the high S / N image data by adding and synthesizing a plurality of image data in the phase interval extracted from the time-series image data collected by the synchronous photographing. The X-ray CT apparatus according to claim 1.   The X-ray CT apparatus according to claim 1, wherein the phase section setting unit sets the phase section by setting a marker for the biological signal displayed by the display unit.   The X-ray CT apparatus according to claim 6, wherein the phase section setting unit sets an addition synthesis start phase and an addition synthesis end phase for the biological signal.   The X-ray CT apparatus according to claim 1, wherein the phase section setting unit sets a section with less respiratory movement or pulsatile movement as the phase section based on the biological signal.   The X-ray CT apparatus according to claim 8, wherein the phase section setting unit sets a section in which a fluctuation range of the biological signal is within a predetermined range as the phase section.   9. The phase section setting means sets a section that includes a phase having a minimum absolute value of a variation rate in the biological signal and has a variation range within a predetermined range as the phase section. X-ray CT system. For an X-ray CT apparatus that generates image data based on projection data of a subject collected by synchronous imaging using biological signals,
A phase interval setting function for setting a phase interval in the biological signal;
A data composition function for generating high S / N image data having a high S / N by adding and synthesizing a plurality of the image data corresponding to different times included in the phase section set by the phase section setting means When,
A control program for executing a display function for displaying the high S / N image data.

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