JP2005118257A - Method for supporting setting of localization information in x-ray ct tomography, and x-ray ct apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for supporting setting of localization information in X-ray CT tomography and an X-ray CT apparatus by which CT tomography is performed efficiently with a reduced exposed dose. <P>SOLUTION: By recognizing the image of a prescribed section (such as the bone collar) based on the scout image data of a subject, the coordinates zp in a body axial direction about a prescribed featured point (such as the lateral extremity) is detected and held. Based on the coordinates zq in the body axial direction of a lesion section inputted based on the CT tomogram diagnostic result of the subject, relative position information (zd=zq-zp) from the featured point to the lesion section (such as a tumor) is calculated and held. Thus, in the next CT tomography, the position of the tumor is estimated nearly precisely only by detecting the position of the lateral extremity of the patient without regard to the size of the subject or which part of an imaging table the subject is placed on. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a localization information setting support method and an X-ray CT apparatus in X-ray CT imaging, and more specifically, includes an X-ray tube and an X-ray detector facing each other with a subject interposed therebetween, and a body axis direction by an imaging table. The present invention relates to a localization information setting support method and an X-ray CT apparatus in X-ray CT imaging for reconstructing a CT tomographic image of a subject based on the X-ray projection data of the subject conveyed to the X-ray CT.

  In the X-ray CT apparatus, comparative imaging and follow-up imaging are often performed for the purpose of knowing the patient's past and current situation changes. In these imaging, imaging at the same position as the location where the imaging was performed in the past is necessary, but conventionally, information on CT imaging acquired in the past (for example, location information of the diseased part) is effectively used for this CT imaging. Therefore, CT imaging is often performed in a useless range exceeding a necessary range (region of interest including a diseased part) in the subject body axis direction, resulting in an increase in subject exposure.

Conventionally, an X-ray CT apparatus that supports graphical input of recon parameters performed this time by regenerating scout image data of a required view angle based on past scan data of a subject and displaying it on a screen. Known (Patent Document 1).
JP 2002-186612 A (summary, figure).

  However, the above-described conventional technique is merely a technique for using scan data acquired in the past for parameter setting input at the time of subsequent image reconstruction (retro-recon), and efficiently performing CT imaging at this time with a small exposure dose. It is not about.

  The present invention has been made in view of the above-described problems of the prior art, and the object of the present invention is to provide localization information setting support method in X-ray CT imaging capable of efficiently performing the current CT imaging with a small exposure dose. And providing an X-ray CT apparatus.

  The above problem is solved, for example, by the configuration shown in FIG. That is, the localization information setting support method of the present invention (1) includes an X-ray tube and an X-ray detector that are opposed to each other with the subject interposed therebetween, and the subject information associated with the position information in the subject body axis direction. A localization information setting support method in X-ray CT imaging for reconstructing a CT tomographic image of a subject based on X-ray projection data, and recognizing an image of a predetermined part (for example, clavicle) based on the scout image data of the subject And detecting and holding the body axis direction coordinate zp for a predetermined feature point (for example, the acromion end) and the body axis direction coordinate zq of the diseased part input based on the CT tomographic image diagnosis result of the subject. And calculating and holding relative position information (zd = zq−zp) from the feature point to the diseased part.

In the present invention (2), in the present invention (1), as shown in, for example, FIG. 1B, the image of the predetermined part (clavicle) is recognized based on the current scout image data of the subject, and the predetermined Detecting a body axis direction coordinate zp ′ for the feature point (acromial end) of the patient, and the relative position information z from the detected coordinate zp ′ and the feature point calculated and held in the previous CT imaging to the diseased part
generating localization information (for example, z160 to z220) for the current CT scan that can cover the diseased site based on d.

  In the present invention (3), in the present invention (1), the step of recognizing the image of the predetermined part based on the current scout image data of the subject and detecting the body axis direction coordinates of the predetermined feature point And localization information for the current image reconstruction that can cover the diseased part based on the detected coordinates and the relative position information from the feature point calculated and held in the previous CT imaging to the diseased part Steps.

  In the present invention (4), in the present invention (2) or (3), the width information in the body axis direction covering the diseased part is input together with the body axis direction coordinate of the diseased part, and based on these information, It generates localization information that can cover a disease site.

  The X-ray CT apparatus of the present invention (5) includes an X-ray tube and an X-ray detector facing each other across the subject, and X-ray projection data of the subject associated with position information in the subject body axis direction In the X-ray CT apparatus for reconstructing the CT tomographic image of the subject based on the above, the image of the predetermined part is recognized based on the scout image data of the subject, and the body axis direction coordinates of the predetermined feature point are detected and held. A detection unit; and a calculation unit that calculates and holds relative position information from the feature point to the diseased part based on body axis direction coordinates of the diseased part input based on a CT tomographic diagnosis result of the subject. is there.

  In the present invention (6), in the present invention (5), the detecting means recognizes the image of the predetermined part based on the current scout image data of the subject, and coordinates in the body axis direction regarding the predetermined feature point Current CT scan and / or image reconstruction that can cover the diseased part based on the detected coordinates and the relative position information from the feature point calculated and held in the previous CT imaging to the diseased part. And generating means for generating localization information.

  In the present invention (7), in the present invention (6), the generating means covers the diseased part based on the width information in the body axis direction covering the diseased part input together with the body axis direction coordinate of the affected part. It generates possible localization information.

  According to the present invention (8), in the present invention (6), there is provided a notifying means for performing a predetermined notification when the current CT scan approaches an area covering the diseased part of the subject.

  By the way, in general, in X-ray CT imaging, the X-ray projection data of the subject is obtained by moving the imaging table on which the subject is mounted, or conversely, by moving the gantry on which the X-ray imaging system is mounted. It is closely associated with the axial position information, which enables accurate scanning and image reconstruction (recon).

  However, in general, the size of the subject varies, and the subject is not always mounted at a reference position in the body axis direction (a fixed position on the imaging table, etc.) managed by the system. The association between the projection data and the position information in the body axis direction differs for each CT imaging. For this reason, in conventional comparative imaging and follow-up imaging, CT imaging is often performed in a range that greatly exceeds the region of interest including the diseased part, leading to an increase in subject exposure.

In this respect, in the present invention (1), the position information of the diseased site that is important in CT imaging is obtained, and the relative position information from the feature point (shoulder edge) integral with the subject to the diseased site (tumor) is obtained. Because of the configuration to find and hold, in the next CT scan, the location of the tumor can be determined almost accurately by simply detecting the ridge end of the subject, regardless of the size of the subject or where it is mounted on the imaging table. Can be estimated.

  According to the present invention (2), based on the coordinate zp ′ of the feature point (shoulder end) detected this time and the relative position information zd to the diseased site (tumor) calculated and held in the previous CT imaging, The localization support information for the current CT scan that can cover the diseased part without waste can be generated appropriately, and the exposure dose of the subject can be greatly reduced.

  According to the present invention (3), the relative position information zd calculated and held in the previous CT scan is used not only for the current CT scan but also for image reconstruction (recon) processing that eliminates the current waste. Can be used effectively.

  In the present invention (4), the width information in the body axis direction covering the diseased part together with the body axis direction coordinate zq of the diseased part based on the previous CT image is input, so that the CT photography of this time is more useless. It is possible to generate accurate localization support information.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. Note that the same reference numerals denote the same or corresponding parts throughout the drawings.

  FIG. 2 is a block diagram of the X-ray CT apparatus according to the embodiment. The apparatus is roughly divided into a scanning gantry unit 30 for performing axial / helical scanning / reading of the subject 100 by the X-ray fan beam XLFB, and a target. An imaging console 20 on which the specimen 100 is placed and moved in the direction of the body axis CLb, and the remote control of the scanning gantry unit 30 and imaging table 20, and an operation console for various settings and operations by an X-ray imaging technician and doctor Part 10.

In the scanning gantry 30, 40 is a rotary anode type X-ray tube, 40 A is an X-ray tube controller for controlling the tube voltage kV, tube current mA, etc. of the X-ray tube, and 50 is a collimator for limiting the slice thickness of the X-ray. , 50A is a collimator control unit, 90 is an X-ray detector (multi-detector) in which a large number (n = 1000) of X-ray detection elements arranged in the channel CH direction are arranged in, for example, two rows L1 and L2 in the body axis CLb direction. ), 91 is a data collection unit (DAS) for generating and collecting projection data g ₁ (X, θ), g ₂ (X, θ) of the subject 100 based on the detection signal of the X-ray detector 90, 35 A gantry 35A is a rotation control unit for the gantry 35. The gantry 35A rotatably supports the devices related to the X-ray imaging system around the body axis CLb.

  In the operation console unit 10, 11 is a central processing unit for performing main control / processing (scan control, automatic localization support processing according to the present invention, CT tomographic reconstruction processing, etc.) of the X-ray CT apparatus, 11a is its CPU, 11b Is a main memory (MM) composed of RAM, ROM, etc. used by the CPU 11a, 12 is an input device for commands and data including a keyboard and a mouse, 13 is a display of scan plan information, recon plan information, and various information related to CT tomograms A display device (CRT) 14 for performing the control interface for exchanging various control signals CS and monitor signals MS between the CPU 11a, the scanning gantry unit 30, the imaging table 20, and the like, and 15 a projection from the data collecting unit 91. Data collection buffer for temporarily storing data, 16 for scan (projection) data and CT A secondary storage device (hard disk device, etc.) that stores and stores layer image data, and stores various application programs necessary for the operation of the X-ray CT apparatus and various calculation / correction data files. is there.

Next, an X-ray CT imaging process using the X-ray CT apparatus will be described in detail. FIG. 3 is a flowchart of the X-ray CT imaging process according to the embodiment. In step S11, an engineer or the like sets scan parameters (tube voltage kV, tube current mA, etc.) for the scout scan of the subject. In step S12, a scout scan of the subject 100 is performed. In the scout scan, the imaging table 20 is moved in the direction of the subject body axis CLb at a constant speed while the gantry 35 is fixed at a predetermined view angle (for example, θ = 0 °), and the subject 100 is seen through X-ray. Scanning that obtains an image (ie, an X-ray image). In step S13, the obtained scout image is displayed on the screen. FIG. 4 shows an example scout image.

  In step S14, the image of the characteristic part (for example, clavicle) is recognized based on the scout image data, and the position information in the body axis direction of the reference point (for example, the caudal end) is extracted and stored in the memory. This process will be specifically described with reference to FIG. In FIG. 5A, projection data of a target portion (for example, a portion from the neck to the upper chest half) is extracted from the scout image data. The projection data of this part corresponds to the position information zi to zj in the subject body axis direction. Further, the projection data of the extracted part is binarized with a predetermined threshold suitable for extracting the bone part, and noise images scattered on a two-dimensional plane are removed by filtering. In FIG. 5B, an edge emphasis process is further performed by a filter process to emphasize the bone contour.

  In FIG. 5C, the clavicle image is recognized by extracting its characteristic shape, and the position information of the predetermined reference point is extracted. Here, the clavicle is a rod-like bone that develops approximately horizontally between the sternum and the scapula at the upper edge of the front chest, and is lightly bent in an S shape. The inner end is called the sternum end, and the outer end is called the acromion end, both of which have joint surfaces. Therefore, for example, the image of the caudal end portion of the clavicle 101R is recognized, and the coordinates zp of the approximate center point are extracted and stored in the memory. Note that the end of the sternum may be recognized. Alternatively, the left and right clavicles 101L and 101R may be recognized, and their feature point coordinates may be extracted and averaged. This can reduce the possibility of erroneous recognition.

  Returning to FIG. 3, in step S15, it is determined whether or not the localization range automatic generation mode is selected. At first (that is, when the previous CT imaging information cannot be used), the automatic generation mode cannot be set. Proceed to S18. In step S18, an engineer or the like sets scan parameters (localization, etc.) for the subsequent axial / helical scan while referring to the scout image on the display screen.

FIG. 4 shows an image of the scan parameter setting process. An example scan parameter for acquiring a CT tomographic image Q is as follows:
Scan type [Scan Type] = Axial scan Scan start position on body axis [Start Loc] = z100
Scan end position on the body axis [End Loc] = z280
Number of scans [NO. Of Scan] = 180
Thickness of specimen [Thick] = 1mm
Scan time [Sec] = 1 second / one gantry rotation X-ray tube voltage [kV] = 120 kV
X-ray tube current [mA] = 280 mA
It is. In the first scan, a sufficiently wide scan range is manually set by an engineer or the like so as not to miss an unknown disease site. Further, when the operator clicks the [Show Localizer] icon on this screen, a line (cut line) indicating each slice position is superimposed on the scout image 100A. The solid bold lines in the figure represent the scan start position and end position, and the dotted lines represent the intermediate slice positions (however, every 20 lines in the figure). The operator can check the scan range and the axial scan position of the subject on the cut line, and freely change them with a mouse or keyboard if necessary.

Returning to FIG. 3, in step S19, it is determined whether the setting is confirmed (CONFIRM). If not confirmed, the process returns to step S18. In this case, if image reconstruction (ie, prospective recon) is performed at the same time as this CT imaging, the engineer clicks on the prospective recon “P-RECON” tag on the display screen 13a to The selective recon parameters (slice position for image reconstruction, slice thickness, number of slices, reconstruction algorithm, image filter, etc.) can be set and input.

FIG. 6 shows an image of the recon parameter setting process. An example of the recon parameters for acquiring the CT tomographic image Q is as follows:
Recon start position on the body axis [Start Loc] = z120
Recon end position on the body axis [End Loc] = z260
Number of images [NO. Of Images] = 140
Recon slice thickness [Thick] = 1mm
Matrix size = 256
It is. In the first recon, a sufficiently wide recon range is manually set by an engineer or the like so as not to miss an unknown disease site.

  Returning to FIG. 3, when the setting confirmation button is finally pressed in the determination in step S19, the subject is scanned in step S20, and projection data is collected and accumulated in step S21. In step S22, it is determined whether or not all scans for a predetermined imaging area are completed. If not, the process returns to step S20. When all the scans are completed in this way, image reconstruction processing is performed in step S23, and the reconstructed CT tomographic image is displayed on the screen in step S24.

  Simultaneously with this display or separately at a later date, when these CT tomograms are diagnosed by a doctor and the slice plane of a diseased part including a tumor or the like is specified, preferably the position information of the central point in the body axis direction Information on the range in the body axis direction that sufficiently covers the diseased part is determined and added to the diagnostic information for acquiring the CT tomographic image Q. In addition, instead of the position information of the center point of the diseased part, position information of a start point and an end point that sufficiently include the diseased part may be input. In step S25, the input of the information is waited. When the information is input, in step S26, necessary dimension information is obtained and stored together with the position information in a location corresponding to the CT tomographic image Q in the memory.

  FIG. 6 shows an image of processing for obtaining the dimension information. Now, assuming that the position information in the body axis direction of the diseased part 105 is zq, the distance information zd from the reference position zp to the diseased part 105 is obtained by zd = zq−zp. In this case, the width information in the body axis direction that sufficiently covers the diseased part 105 is, for example, zq ± 30 mm.

  Returning to FIG. 3, CT imaging processing when acquiring the CT tomographic image R for the second and subsequent days for the same patient will be described next. However, description of the same processing as the previous time is omitted. FIG. 7 shows the processing image. In step S14, based on the current scout image data of the subject 100, the position information zp 'of the clavicle cusp is detected and stored in the memory. Since the subject 100 is not always mounted at the same position on the imaging table 20 every time imaging is performed, generally zp ≠ zp ′.

  In the subsequent determination in step S15, since the previous CT imaging information can be used after the second time, the process proceeds to step S16. In step S16, relative position information zd from the reference position zp of the previous diseased part 105 is acquired from the storage location corresponding to the previous CT tomographic image Q in the memory. In step S17, localization information for acquiring the current CT tomographic image R is automatically generated and displayed on the screen.

  In FIG. 7, the position zq ′ of the diseased part 105 in the body axis direction is obtained by zq ′ = zp ′ + zd. Furthermore, the current scan start position = z160 and the scan end position = z220 can be automatically generated according to the range information Δ = ± 30 mm for sufficiently covering the diseased part 105.

  For example, in the application of comparative imaging for diagnosing whether a specific diseased part 105 is enlarged or reduced after that, by automatically generating the minimum necessary scanning range of this time based on the previous CT imaging information Unnecessary exposure received by the subject 100 can be minimized. It should be noted that this scan range generation information is for supporting the judgment of an engineer or the like, and it goes without saying that the engineer or the like can arbitrarily set / change the actual scan range (or recon range) in the subsequent step S18. .

  Thereafter, the process proceeds in the same manner as the previous time, and in step S20, the subject 100 is scanned. In this case, it is preferable that a buzzer (not shown) is sounded when the scan has approached the region of interest (that is, zq ′ ± Δ) to capture the attention of the patient or technician. Preferably, the patient performs breath holding or the like accordingly. Furthermore, in step S24, preferably, the CT tomogram of the previous corresponding part is displayed on the screen in parallel with the display of the current CT tomogram, so that the doctor, the engineer, etc. It becomes easy to compare with. In step S26, necessary dimension information zd 'is obtained based on the imaging information of the current CT tomographic image R and stored together with the position information in a location corresponding to the image R of the memory. Since the physique of the subject may change gradually, it is useful to retain dimensional information related to the previous CT scan.

  In the above embodiment, the case of the axial scan has been described. However, in the case of the helical scan, the axial data can be generated by interpolation and then processed by the same method as described above.

  In the above embodiment, the scanning gantry unit 30 is fixed and the imaging table 20 moves. However, the present invention is not limited to this. Conversely, the present invention can be similarly applied to the case where the scanning table 20 is fixed and the scanning gantry unit 30 moves.

  Further, in the above-described embodiment, the imaging is performed over a wide range of the subject even in the second and subsequent scout imaging, but the present invention is not limited to this. From the second time onward, if there is scout image data that includes at least a predetermined part (such as the clavicle), accurate localization support of the disease part can be performed.

  Further, although the preferred embodiment of the present invention has been described, it goes without saying that various changes in the configuration, control, processing, and combination of each part can be made without departing from the spirit of the present invention.

It is a figure explaining the principle of this invention. 1 is a block diagram of an X-ray CT apparatus according to an embodiment. It is a flowchart of the X-ray CT imaging process by embodiment. It is an image figure (1) of the scan parameter setting processing by an embodiment. It is an image figure explaining the image recognition process of the characteristic part by embodiment. It is an image figure of the recon parameter setting process by embodiment. It is an image figure (2) of the scan parameter setting processing by an embodiment.

Explanation of symbols

10 Operation console 11 Central processing unit 11a CPU
11b Main memory (MM)
12 Input device 13 Display device (CRT)
14 Control Interface 15 Data Collection Buffer 16 Secondary Storage Device (Hard Disk Device etc.)
20 Imaging table 30 Scanning gantry section 35 Gantry 40 X-ray tube 50 Collimator 90 X-ray detector (multi-detector)
91 Data Collection Unit (DAS)

Claims (8)

An X-ray tube and an X-ray detector facing each other with the subject interposed therebetween, and a CT tomographic image of the subject is reconstructed based on the X-ray projection data of the subject associated with position information in the subject body axis direction A support method for setting localization information in X-ray CT imaging,
A step of recognizing an image of a predetermined part based on scout image data of a subject and detecting / holding a body axis direction coordinate for a predetermined feature point;
Localization information comprising: calculating and holding relative position information from the feature point to the diseased part based on body axis direction coordinates of the diseased part input based on a CT tomographic image diagnosis result of the subject. Setting support method. Recognizing an image of the predetermined part based on current scout image data of the subject and detecting body axis direction coordinates for the predetermined feature point;
Generating localization information for the current CT scan capable of covering the diseased part based on the detected coordinates and relative position information from the feature point calculated and held in the previous CT imaging to the diseased part. The localization information setting support method according to claim 1, further comprising: Recognizing an image of the predetermined part based on current scout image data of the subject and detecting body axis direction coordinates for the predetermined feature point;
Generating localization information for current image reconstruction capable of covering the diseased part based on the detected coordinates and relative position information from the feature point calculated and held in the previous CT imaging to the diseased part; The localization information setting support method according to claim 1, further comprising: The body axis direction width information covering the diseased part is input together with the body axis direction coordinate of the diseased part, and localization information capable of covering the diseased part is generated based on the information. Or the setting support method of the localization information of 3 description. An X-ray tube and an X-ray detector facing each other with the subject interposed therebetween, and a CT tomographic image of the subject is reconstructed based on the X-ray projection data of the subject associated with position information in the subject body axis direction X-ray CT apparatus
Detecting means for recognizing an image of a predetermined part based on scout image data of the subject and detecting / holding a body axis direction coordinate for a predetermined feature point;
X is provided with a calculation means for calculating and holding relative position information from the feature point to the diseased part based on the body axis direction coordinates of the diseased part input based on the CT tomographic image diagnosis result of the subject. Line CT device. The detection means recognizes the image of the predetermined part based on the current scout image data of the subject and detects the body axis direction coordinates of the predetermined feature point,
Localization information for this CT scan and / or image reconstruction that can cover the diseased part based on the detected coordinates and relative position information from the feature point calculated and held in the previous CT imaging to the diseased part 6. The X-ray CT apparatus according to claim 5, further comprising generating means for generating. The generating means generates localization information capable of covering the diseased part based on width information in the body axis direction covering the diseased part inputted together with the body axis direction coordinate of the affected part. The X-ray CT apparatus described. The X-ray CT apparatus according to claim 6, further comprising notification means for performing predetermined notification when the current CT scan approaches an area covering the diseased part of the subject.

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