JP5269495B2 - X-ray CT system - Google Patents

Description

  The present invention relates to a function for measuring not only CT value information in the XYZ plane but also a change in CT value in the time direction and automatically defining a substance on the image from the measured value. The present invention relates to an X-ray CT apparatus for aligning a beam hardening correction and a defined area in the time direction using the obtained area.

In specifying the contrast agent region in the conventional X-ray CT value, the time-direction CT value change in all pixels is calculated using the time-direction volume data. At this time, since the volume is the same, the region such as the bone always has a constant CT value in the time direction, but the region into which the contrast medium flows has a CT value that changes in the time direction. A pixel having this amount of change is defined as a contrast agent region.
Japanese Patent Application Laid-Open No. 07-204197

  However, in the conventional beam hardening correction of such an X-ray CT apparatus, for example, a bone having a high CT value and a contrast medium cannot be separated, and the correction is performed by defining the same substance. It was.

  That is, conventionally, the CT value of each pixel in one image (XY plane) is measured, and the subject image is classified and defined into two substances, water and bone, by a threshold setting hand. In this case, it was impossible to separate the bone and the contrast medium exceeding the high threshold value even though they are different substances in the subject. As a result, a contrast agent having a different composition is mistaken as a bone and the image quality is corrected, and appropriate correction cannot be performed.

  Accordingly, the present invention has been made in view of the above circumstances, and an object thereof is an X-ray CT apparatus capable of performing appropriate correction without mistaking a contrast agent having a different composition as a bone and correcting image quality. Is to provide.

  That is, the present invention is for taking a tomographic image for diagnosis using a contrast agent, and detects an X-ray tube that irradiates a subject with X-rays and an X-ray that has passed through the subject to detect an electrical signal. An X-ray detector that converts the data of the subject into a back projection process based on the X-rays detected by the X-ray detector, and a reconstruction unit that reconstructs a first image; An X-ray CT apparatus comprising: a display device that displays a first image reconstructed by a configuration unit; a region detection unit that detects a region into which the contrast medium flows; and a detection by the region detection unit Based on the contrast agent region thus obtained, a beam hardening correction is performed on the contrast agent region in the subject and correction components obtained for regions other than the contrast agent region to obtain a second image. Correction means, and the reconstruction means includes the first image. Characterized in that it constitutes the reconstructed image after the correction by combining the second image.

  The present invention also provides a diagnostic tomographic image using a contrast agent. An X-ray tube that irradiates a subject with X-rays and an X-ray transmitted through the subject to detect an electrical signal. An X-ray detector for converting to X, a reconstruction means for reprojecting the data of the subject based on the X-rays detected by the X-ray detector, and reconstructing an image; and the reconstruction means In an X-ray CT apparatus comprising a display device for displaying a reconstructed image, a region detecting means for detecting a region into which the contrast agent flows based on the state of the contrast agent that changes in time series And the reconstruction means reconstructs an image by performing a back projection process on the data of the subject based on the area of the contrast agent detected by the area detection means.

  ADVANTAGE OF THE INVENTION According to this invention, the X-ray CT apparatus which can perform appropriate correction | amendment, without misidentifying the contrast agent from which a composition differs as a bone and correcting image quality can be provided.

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

  FIG. 1 is a block diagram showing the overall configuration of an X-ray CT apparatus according to an embodiment of the present invention.

  In FIG. 1, the X-ray CT apparatus according to this embodiment includes a gantry device 1, a bed device 3, and an operation console unit 2.

  The gantry device 1 includes a gantry controller 11, an X-ray tube 12, an X-ray detector 13, a rotating gantry 14, a high voltage generator 15, a data collection unit (DAS) 16, and a rotation driving unit 17. And the second input unit 18 are installed in the examination room.

  The couch device 3 includes a couch driving unit 31, a couch base 32, and a couch top plate 33, and is installed in the examination room together with the gantry device 1.

  On the other hand, the operation console unit 2 includes a console control unit 21, a first input unit 22, a preprocessing unit 23, a projection data storage unit 24, a reconstruction processing unit 25, an image storage unit 26, and image processing. The unit 27, the display device 28, the inspection condition storage unit 29, and the correction processing unit 30 are configured and installed in the operation room.

  The console control unit 21 controls each unit in the operation console unit 2, and constitutes a setting unit together with the first input unit 22. The first input unit 22 includes a mouse, a keyboard, and the like.

  When scanning is performed by helical scan, the gantry controller 11 stores helical scan conditions such as slice thickness and rotation speed input by the first input unit 22 in the inspection condition storage unit 29 (selection of inspection conditions). Is done. Among them, the rotation speed, slice thickness, fan angle, and the like are output to the gantry control unit 11 and the couch driving unit 31 as a gantry / couch control signal.

  In addition, the gantry controller 11 receives an input (information on the selected inspection condition) from the second input unit 18, and an X-ray beam generation control signal for controlling X-ray beam generation is sent to the high voltage generator 15. Are output. Further, the gantry controller 11 outputs a detection control signal indicating the detection timing of the X-ray beam to the data acquisition device 16.

  The second input unit 18 is a display panel having a touch sensor function installed on the surface of the gantry device 1 in the form of an “operation panel”. Patient information associated with the patient identification information using the network by inputting without patient identification information such as patient ID to a third input means (not shown) provided on the display panel Can be displayed.

  The second input unit 18 is transmitted from the couch device 3 or the first input unit 22 after the setting of the subject on the gantry device 1 and the selection of the examination conditions by the first input unit 22 are completed. The second input unit 18 can be input in response to the signal. At this time, it is desirable that the second input unit 18 itself is lit so that the examiner can recognize that the input is possible.

  Furthermore, a detection unit (not shown) for detecting that an examiner has entered the operation room is provided on a door of the operation room (a door separating the inspection room and the operation room) or the like. Until the entry of the examiner is detected, the gantry control unit 11 may not make the second input unit 18 ready for input. With such a configuration, the subject P is scanned (X-ray irradiation) in a state in which it is detected that the examiner has moved from the examination room to the operation room. Can be avoided from exposure.

  The detection unit includes, for example, one detection unit provided in the vicinity of the door and provided in the examination room, and another detection unit provided in the operation room. Is detected, it is detected that the examiner has moved from the examination room to the operation room due to the detection of the examiner by another detection unit.

  The high voltage generator 15 supplies a high voltage for exposing the X-ray beam from the X-ray tube 12 to the X-ray tube 12 according to a control signal from the gantry controller 11. The X-ray tube 12 exposes the X-ray beam with the high voltage supplied from the high voltage generator 15. The X-ray beam exposed from the X-ray tube 12 is a fan-shaped or cone-shaped beam.

  The X-ray detector 13 detects an X-ray beam that has been exposed from the X-ray tube 12 and transmitted through the subject. In the case of a single-slice CT apparatus, the X-ray detector 13 is configured by arranging, for example, 1000 channels of X-ray detection elements in a row in a fan shape or a linear shape. In the case of a multi-slice CT apparatus, the X-ray detector 13 includes a plurality of X-ray detector elements arranged in an array in two orthogonal directions (slice direction and channel direction). It constitutes an X-ray detector.

  A rotary mount (gantry) 14 holds the X-ray tube 12 and the X-ray detector 13 therein. Further, the rotating gantry 14 is rotated by a gantry driving unit 17 around a rotation axis passing through an intermediate point between the X-ray tube 12 and the X-ray detector 13.

  The data acquisition unit (DAS) 16 includes data acquisition elements arranged in an array similar to the X-ray detection elements of the X-ray detector 13, and the X-ray beam (actually detected by the X-ray detector 13). Is detected in correspondence with the data collection control signal output by the gantry control unit 11. This collected data becomes X-ray projection data.

  When the rotating mount 14 rotates once, X-ray projection data is collected 1000 times, for example, and an image is reconstructed by a predetermined method based on the X-ray projection data. The gantry driving unit 17 rotates the rotating gantry 14 based on the gantry control signal output by the gantry control unit 11.

  The couch driving unit 31 obtains the movement amount of the couch top plate 33 per rotation of the rotating gantry 14 based on the couch movement signal output from the gantry control unit 11, and moves the couch top plate 33 by this movement amount. . The bed base 32 moves the bed top plate 33 in the vertical direction by the bed driving unit 31. The couch top 33 carries the subject P and can move in the body axis direction (Z-axis direction: slice direction) of the subject P.

  The preprocessing unit 23 performs sensitivity correction, X-ray intensity correction, and the like on the X-ray projection data output from the data collection unit 16. In addition, the preprocessing unit 23 detects a region into which the contrast agent flows, as will be described later. The X-ray projection data that has been subjected to processing such as sensitivity correction by the preprocessing unit 23 is temporarily stored in the projection data storage unit 24.

  The reconstruction processing unit 25 reconstructs image data by performing a back projection process on the X-ray projection data stored in the projection data storage unit 24. This back projection method is the same as a known method. When performing interpolation processing on X-ray projection data, X-ray projection data at a target slice position is obtained by a known interpolation method such as a 360-degree interpolation method or a 180-degree interpolation method (opposite data interpolation method). Ask for.

  The reconstructed image data is temporarily stored in the image storage unit 26 and then sent to the image processing unit 27. Based on the operator's instruction input by the first input unit 22, the image processing unit 27 converts the image data into a tomographic image of an arbitrary cross section, a projection image from an arbitrary direction, or a rendering process 3 according to a known method. It is converted into image data such as a dimensional image and output to the display device 28. The display device 28 displays a tomographic image or the like output from the image processing unit 27 on a monitor.

  Further, as will be described in detail later, the correction processing unit 30 performs correction processing such as beam hardening on the reconstructed image to obtain a corrected image.

  Next, with reference to FIGS. 2 and 3, changes in the time axis direction of the bone and water of the subject and the contrast medium will be described.

  In the case of time-series image data obtained by photographing the same area of a subject with a volume, the bone 41 and water 42 of the subject have substantially the same CT value in the time axis direction as shown in FIG. Therefore, the amount of change in the time axis direction is small. On the other hand, the contrast agent (CM) 43 has a CT value that changes in the time axis direction (in time series) depending on the blood flow of the subject. Therefore, in the present embodiment, the bone 41 and the contrast agent 43 are separated using the change amount of the CT value in the time axis direction.

  For example, with only one volume of the image at time t, the CT values of the bone 41 and the contrast agent 43 are the same, so that they cannot be distinguished from each other as shown in FIG. However, by measuring the CT values of the images before and after the time axis direction and comparing the amount of change in the CT values, the regions of the bone 41 and the contrast agent 43 are obtained as shown in FIGS. Can be separated.

  Next, with reference to the flowchart of FIG. 4 and the explanatory diagram of FIG. 5, the processing operation of the beam hardening correction by the X-ray CT apparatus of one embodiment of the present invention will be described. The processing operation according to this flowchart is mainly performed in accordance with commands from the console control unit 21.

First, as shown in FIG. 5, a desired region image is obtained by a normal reconstruction process (A1, A2) as in the prior art. Next, when this sequence is started, in step S1, as shown in FIG. 2 and FIGS. 3A to 3C, an image to be corrected (Image _t ) and a time with the image as a central time are displayed. The CT value of each pixel in the front and rear images (Image _t-1 ) and (Image _{t + 1} ) in the direction is measured.

  Next, in step S2, the calculated CT value change amount is calculated using the CT value information of the image to be corrected measured in step S1 and the previous and next CT values. For example, when the same region of the subject is imaged in the time direction, the CT values of the bone 41 and the water 42 do not change in the time direction as shown in FIG. The separation of the bone 41 and the water 42 is performed by using the same CT value as in the 2 ns-pass beam hardening correction using the conventional reconstruction.

  On the other hand, since the CT value of the contrast agent 43 that flows in changes in the time direction, the CT value change amount in the time direction is calculated. By using this, it is possible to automatically separate both the bone 41 and the contrast agent 43 having the same CT value on the correction target image.

  Next, in step S3, region images of bone 41, water 42, and contrast agent 43 are created (A4) and projection data is obtained (A5). Then, the path length of each substance is calculated from each projection data (A6). Further, in step S4, correction component projection data is calculated.

  Since continuous X-rays and monochromatic X-rays have a water attenuation coefficient, a bone attenuation coefficient, and a contrast medium attenuation coefficient, projection data of bone, water, and contrast medium are acquired for each of them (A7a, A8a, A7b, A8b). Then, a difference between the acquired continuous X-ray projection data (A8a) and monochromatic X-ray projection data (A8b) is obtained. This difference is considered to be a value resulting from beam hardening. Accordingly, in step S5, the image is reconstructed based on the difference value between the continuous X-ray and the monochromatic X-ray (A9, A10). The image reconstructed in this way is an image of only the correction component (A11).

  In step S6, the image (A2) obtained by the normal reconstruction and the image (A11) having only the correction component are added. As a result, an image corrected in consideration of attenuation coefficients of water, bone, and contrast agent is obtained (A12).

  As described above, since it was impossible to separate a bone and a contrast medium conventionally, both were defined as the same substance and a correction component was calculated. In other words, since the bone attenuation coefficient was originally applied even though it was a contrast agent, the correction accuracy in contrast data was poor. However, in this embodiment, since the bone 41 and the contrast agent 43 can be separated, the correction accuracy can be improved by applying an optimum attenuation coefficient to each.

  Although the embodiment of the present invention has been described above, the present invention can be modified in various ways without departing from the gist of the present invention other than the above-described embodiment.

  Further, the above-described embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be extracted as an invention.

1 is a block diagram showing an overall configuration of an X-ray CT apparatus according to an embodiment of the present invention. It is a figure for demonstrating the change of the time-axis direction of a to-be-photographed object's bone and water, and a contrast agent. It is a figure for demonstrating the change of the time-axis direction of a to-be-photographed object's bone and water, and a contrast agent. It is a flowchart for demonstrating the processing operation | movement of the beam hardening correction | amendment by the X-ray CT apparatus of one Embodiment of this invention. It is a figure for demonstrating the processing operation of the beam hardening correction | amendment by the X-ray CT apparatus of one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Mount apparatus, 2 ... Operation console part, 3 ... Bed apparatus, 11 ... Mount control part, 12 ... X-ray tube, 13 ... X-ray detector, 14 ... Rotary mount, 15 ... High voltage generation part, 16 ... Data Collection unit (DAS), 17 ... Rotation drive unit, 18 ... Second input unit, 21 ... Console control unit, 22 ... First input unit, 23 ... Pre-processing unit, 24 ... Projection data storage unit, 25 ... Re Configuration processing unit, 26 ... image storage unit, 27 ... image processing unit, 28 ... display device, 29 ... inspection condition storage unit, 30 ... correction processing unit, 31 ... bed driving unit, 32 ... bed base, 33 ... bed top Plate, 41 ... bone, 42 ... water, 43 ... contrast agent.

Claims (5)

An X-ray tube for taking a diagnostic tomographic image using a contrast agent, and an X-ray tube that irradiates the subject with X-rays, and an X-ray that detects X-rays transmitted through the subject and converts them into electrical signals A detector, reconstruction means for reprojecting the data of the subject based on the X-rays detected by the X-ray detector to reconstruct a first image, and reconstruction by the reconstruction means An X-ray CT apparatus comprising:
A region detecting means for detecting a region into which the contrast agent flows;
Based on the contrast agent region detected by the region detection means, beam hardening correction is performed from correction components obtained for the contrast agent region in the subject and the region other than the contrast agent region. Correction means for obtaining a second image;
Further comprising
The X-ray CT apparatus characterized in that the reconstruction means composes a corrected reconstructed image by combining the first image and the second image.   The X-ray CT apparatus according to claim 1, wherein the region detection unit detects a region into which the contrast agent flows based on a CT value of the contrast agent.   The second image is an image composed of only the correction component of the first image calculated based on a difference between an attenuation coefficient in continuous X-rays and an attenuation coefficient in monochromatic X-rays. The X-ray CT apparatus according to claim 1. An X-ray tube for taking a diagnostic tomographic image using a contrast agent, and an X-ray tube that irradiates the subject with X-rays, and an X-ray that detects X-rays transmitted through the subject and converts them into electrical signals A detector, reconstruction means for reprojecting the data of the subject based on the X-rays detected by the X-ray detector, and reconstructing an image; and an image reconstructed by the reconstruction means An X-ray CT apparatus provided with a display device for displaying
Comprising region detection means for detecting a region into which the contrast agent flows based on the state of the contrast agent that changes in time series,
The reconstruction means reconstructs a beam hardening correction component image by backprojecting the data of the subject based on the region of the contrast agent detected by the region detection means. CT device.   The region detection means detects a region where the contrast agent flows from a CT value of the contrast medium at a predetermined time and a CT value of the contrast medium before and after the predetermined time. 4. The X-ray CT apparatus according to 4.

Images