JP4594459B2 - X-ray CT system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray CT (computed tomography) apparatus, and particularly has a real-time CT value monitoring function to monitor a CT value of a region of interest by a first scan, and when this CT value satisfies a predetermined condition. The present invention relates to an X-ray CT apparatus that executes a second scan for acquiring a clinical application image.
[0002]
[Prior art]
In recent X-ray CT apparatuses, the performance of detectors and the speed of arithmetic processing apparatuses have increased, and real-time reconstruction has been realized in which image reconstruction is performed and displayed while scanning is in progress.
[0003]
There is a system for monitoring CT values in real time by applying this real-time reconstruction technique to X-ray CT imaging using a contrast agent. The system performs a first scan after contrast agent administration to monitor the CT value of the region of interest, and performs a second scan when the contrast agent distribution is optimal and is properly imaged. Get the image.
[0004]
In this real-time CT value monitoring system, the CT value of the region of interest is monitored in real time, and an image in the optimal distribution state of the contrast agent is obtained in the second scan. For this reason, the amount of contrast medium used can be reduced to reduce the burden on the subject, and the number of scans can be reduced to reduce the radiation exposure amount of the subject.
[0005]
The X-ray CT apparatus provided with such a system designates only one region of interest in the first scan, and uses this as a target for real-time CT value monitoring.
[0006]
[Problems to be solved by the invention]
For this reason, the timing for executing the second scan is determined based on the CT value of a single region of interest, and it is necessary to always grasp the CT value with high accuracy.
[0007]
As a result, for example, a different determination may be made when a disturbance due to body movement of the subject is received during the first scan. For this reason, it is necessary to set a region of interest in a place where there is little disturbance, or to deal with it in a direction to identify the substance of the disturbance, and the computer resources allocated to this increase in a power, which in turn limits the conditions for specifying the region of interest. There was concern about the impact of being affected.
[0008]
The present invention has been made in view of the above points, and its purpose is to provide the necessary accuracy according to the situation without always grasping the CT value of the region of interest to be monitored in the first scan with high accuracy. If it grasps | ascertains by this, it is providing the X-ray CT apparatus which can perform a 2nd scan at a suitable timing.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the X-ray CT apparatus of the present invention according to claim 1 monitors the CT value of the region of interest by the first scan, and when this CT value satisfies a predetermined condition, the clinical application Region-of-interest setting means capable of setting a plurality of regions of interest to be monitored in an X-ray CT apparatus that executes a second scan for acquiring an image Determining means for determining whether the CT value of the region of interest set by the region of interest setting means satisfies the predetermined condition; and changing the CT value of another region of interest set by the region of interest setting means Monitoring means for monitoring, and control means for stopping activation of the second scan based on a result of monitoring by the monitoring means; It is characterized by having.
[0010]
In order to achieve the above object, the X-ray CT apparatus of the present invention according to claim 2 monitors the CT value of the region of interest by the first scan, and when this CT value satisfies a predetermined condition, the clinical application In a multi-slice X-ray CT apparatus that executes a second scan for acquiring an image, the multi-slice X-ray CT apparatus includes a region-of-interest setting unit that can set the region of interest to be monitored for each of a plurality of different tomographic planes. It is characterized by.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings. In the figure, elements showing the same operation are denoted by the same reference numerals to avoid duplication of explanation.
[0012]
First, a first embodiment of the present invention will be described with reference to FIGS.
[0013]
As shown in FIG. 1, the X-ray CT apparatus CT1 includes an inspection system A1 that scans a subject P in one of a plurality of X-ray scan modes and collects scan data, and a scan that is collected by the inspection system A1. Based on the data, the monitor image of the scan part of the subject P is reconstructed and displayed, and CT data of each region of interest (hereinafter often referred to as “ROI”) set in the manner described later in the display image. And a monitoring system B1 that provides numerical data (hereinafter often referred to as “representative CT value” or simply “CT value”) that represent them by region, and the numerical data composed of a plurality of CT values. From the control system C1 that recognizes a special feature in light of the relationship with the scheduled scan portion of the subject P and gives a control command CM to the examination system A1 based on the recognition result That. The overall characteristics (that is, attributes) of the numerical data to be recognized by the control system C1 and the saliency (that is, the significance) for the recognition are defined by various conditions set in the manner described later. . The control command CM includes an activation signal for the second scan when the inspection system A1 is in the scan mode for performing the first scan and the setting condition is satisfied.
[0014]
The inspection system A1 includes an X-ray tube 31 that is an X-ray source and a dose detector 33, a rotating scan base 3, and a bed apparatus 5 that includes a top plate on which the subject P is placed and moved in the body axis direction. And a projection data collection unit 7 that amplifies the detection signal of the detector 33 and performs A / D conversion to collect the signal.
[0015]
The monitoring system B1 includes a storage memory 35 that stores projection data, a reconstruction calculation device 37 that reconstructs a scanogram and a tomographic image from the projection data read from the storage memory 35, and calculates a representative CT value of the region of interest. A reconstruction device 9 having an ROI position information memory 39 for storing coordinate data of the set region of interest, an image memory 11 for storing a scanogram, a tomographic image, and CT values of a plurality of regions of interest, and the image memory 11 And a display device 13 that functions as an output device to the operator by displaying the image stored in the screen.
[0016]
The control system C1 includes a console including a CPU (central processing unit) 15 that controls the entire X-ray CT apparatus CT1, the position and shape of a plurality of regions of interest, the CT value condition for each region of interest, and an arithmetic expression between the CT value conditions. And an input device including a keyboard 17 and a mouse 19 capable of inputting other necessary items, and an ROI condition memory 21 for storing setting conditions such as CT value conditions for each region of interest and arithmetic expressions between CT value conditions. ing.
[0017]
The display device 13 of the monitoring system B1 is disposed in the display unit of the console, and is configured to be able to interact with the console operator via the display screen and the input device of the control system C1.
[0018]
In the gantry 3, the X-ray tube 31 and the detector 33 are arranged to face each other, and are driven by a rotation driving mechanism to rotate around the body axis of the subject P, thereby causing X-ray projection from around the subject P. The intensity distribution is detected.
[0019]
In the reconstruction device 9, the projection data memory 35 stores the projection data sent from the data collection unit 7, and the ROI position information memory 39 includes the positions of a plurality of regions of interest input from the input device including the keyboard 17 and the mouse 19. Then, the reconstruction calculation device 37 reconstructs a tomographic image using data in the projection data memory 35 and calculates a representative CT value of the region of interest stored in the ROI position information memory 39.
[0020]
The CPU 15 includes a scan control unit 41 and a condition determination unit 43, and serves as a console that controls the entire X-ray CT apparatus CT1. The scan control unit 41 can rotate the X-ray tube 31 and the detector 33 of the gantry 3 to the rotational drive mechanism via the control command CM, and at the same time, a high voltage for supplying a high voltage to the X-ray tube 31. Controlling the voltage power supply and the couch device 5, a scan image of the subject P, a reference image acquisition scan, a first scan, a normal scan, an actual scan, or a second scan may be called a second scan. It is possible to correspond to a plurality of scan modes including a plurality of scans.
[0021]
The first scan is a scan for monitoring the CT value of the region of interest, and this monitoring is performed to determine the execution timing of the second scan. For this reason, the first scan is usually performed with a low X-ray dose, and is performed intermittently or continuously after contrast medium administration. In this regard, the second scan is a scan for acquiring CT images that are as diverse and effective as possible for the purpose of clinical application. For example, at the timing immediately before the contrast medium is optimally distributed. It needs to be taken into consideration so that as much information as possible to be examined can be pulled out and the X-ray dose is relatively high.
[0022]
The first scan may be executed as a pilot scan in which relative motion between the gantry 3 and the subject P does not occur in the body axis direction. In this case, if the detector 33 is a single slice detector, One tomographic image is obtained. In a system in which the detector 33 is a multi-slice detector and the X-ray tube 31 generates a cone beam corresponding to the detector 33, a multi-slice tomographic image is obtained.
[0023]
The condition determination unit 43 of the CPU 15 calculates the representative CT values of the plurality of regions of interest calculated by the reconstruction device 9 and stored in the image memory 11, and the CTs of the plurality of regions of interest stored in the ROI condition memory 21. The value condition is read out, and it is determined whether or not the former satisfies the latter. If arithmetic expressions between CT value conditions for a plurality of regions of interest are stored, they are also read and calculated, and if all the conditions are satisfied, it is allowed to shift from the first scan to the second scan Make a decision.
[0024]
Here, with reference to FIG. 2 and FIG. 3, the setting point of the region of interest and the determination condition will be described.
[0025]
FIG. 2 shows setting icons 71 to 79 displayed on the screen of the display device 13. These icons 71 to 79 are used for setting positions and shapes of a plurality of regions of interest and setting thresholds for determining the significance of representative CT values for each region of interest. These icons can be configured as console panel switches. In this embodiment, for convenience of explanation, the number of regions of interest that can be set is three, but may be four or more.
[0026]
FIG. 3 shows a condition setting window 80 displayed on the screen of the display device 13.
This window 80 has an upper area 80a displayed with condition setting (1), an intermediate area 80b displayed with condition setting (2), and a lower area 80c. In the condition setting (1) area 80a, the comparison condition (inequality) between the threshold value for each region of interest set by the icon 76 and the representative CT value, and the determination result for each region of interest for this condition are displayed for all interests. It is used for setting an arithmetic expression indicating a logical condition (AND / OR) for comprehensive determination over a region. Note that the threshold value, the comparison condition, and the combination thereof are all considered to be CT value conditions.
[0027]
The condition setting (2) area 80b is used to set conditions (simultaneous inequalities) for comprehensively comparing the representative CT values of a plurality of regions of interest. The comparison condition in this case is also considered as a CT value condition.
[0028]
Icons 71 to 74 are selectively used to set a region of interest having an arbitrary shape at an arbitrary position on the tomographic image 59 (FIG. 1). When setting a circular region of interest, the circle icon 71 is selected, and when setting a rectangular region of interest, a square icon 72 is selected. The icon 73 is selected when a polygonal region of interest is set, and the icon 74 is selected when an arbitrary-shaped region of interest is set.
[0029]
When using the icons 71 to 73, any one can be selected, and for example, the mouse 19 can set a region of interest having a shape corresponding to an arbitrary position on the tomographic image 59. It is also possible to change the size of the set region of interest, and it can be arbitrarily enlarged or reduced by dragging a part of the boundary line on the outer periphery of the region.
[0030]
When the icon 74 is used, a region of a desired shape is enclosed by drawing a closed curve on the image by the locus of the cursor interlocked with the mouse 19 and set as a region of interest. The region of interest set through the input device such as the keyboard 17 or the mouse 19 is stored in the ROI position information memory 39 by the CPU 15 and displayed on the tomographic image 59 simultaneously.
[0031]
Each region of interest can be input a CT value condition for each region of interest by selecting the [CT value] icon 75 after setting its position and shape.
[0032]
When this icon 75 is selected, the average CT value of the region of interest set immediately before is automatically displayed at the location of the icon 76.
[0033]
Therefore, by inputting a 4-digit numerical value from the keyboard 17 and overwriting the average CT value, or by increasing / decreasing the average CT value by using the keyboard 17 or the mouse 19, the display value of the icon 76 is appropriately changed, and the corresponding interest. This is set as a CT value condition to be compared with the representative CT value of the region.
[0034]
When the [next ROI] icon 77 is selected, the next region of interest setting mode is entered, and the position and shape of this region of interest are set as described above. Thus, the setting of the region-of-interest and region-specific CT value conditions is repeated in sequence.
[0035]
After setting the respective positions, shapes, and CT value conditions for the required number of regions of interest 61, 62, 63, the settings can be confirmed by selecting the [OK] icon 79. When the setting needs to be changed, it is possible to reset from the first region of interest by selecting the [Cancel] icon 78.
[0036]
Next, a logical operation expression for making an integrated determination on CT values of a plurality of regions of interest is set. When the rectangular icon 81 shown in FIG. 3 is selected, the condition setting (1) area 80a is selected, and when the icon 86 is selected, the condition setting (2) area 80b is selected.
[0037]
In the condition setting (1), an icon 84 or 85 is selected, an inequality sign (<,>) is selected as a comparison condition between the representative CT value of each region of interest and the CT value condition (threshold), and the condition is true. ("1"). If not established, set a logical variable for each region of interest that is false ("0") and select the icon 82 or 83 to perform a logical product (combination of ANDs) between the logical variables. Alternatively, a logical sum (OR combination) is designated, and the determination logical function F is set. The following equation (1) is an example of the logical function F.
[0038]
[Expression 1]
F = (ROI1> ct1) * (ROI2> ct2) * (ROI3> ct3) (1) where ROIi (1 ≦ i ≦ 3) is the representative CT value of the region of interest i obtained in the first scan. And cti (1 ≦ i ≦ 3) is a CT value condition (threshold value) of the region of interest i. “*” Indicates a logical product.
[0039]
The logical function F of Equation (1) is true when ROI1 is greater than ct1, ROI2 is greater than ct2, and ROI3 is greater than ct3, otherwise it is false.
[0040]
The following equation (2) shows another example of the logical function F.
[0041]
[Expression 2]
F = (ROI1> ct1) + (ROI2> ct2) + (ROI3> ct3) (2) Here, ROIi (1 ≦ i ≦ 3) is the representative CT value of the region of interest i obtained in the first scan. And cti (1 ≦ i ≦ 3) is a CT value condition (threshold value) of the region of interest i. “+” Indicates a logical sum.
[0042]
The logical function F in Expression (2) is true if any of the condition that ROI1 is greater than ct1, the condition that ROI2 is greater than ct2, and the condition that ROI3 is greater than ct3 is satisfied. Is false only if
[0043]
The truth value of the logical function F is a criterion for determining whether to continue the first scan or shift to the second scan, as will be described later (step S33).
[0044]
In the condition setting (2), by selecting the icon 87 or 88, an integrated comparison condition (magnitude relation) between representative CT values of a plurality of regions of interest is set as a simultaneous inequality G. An example of this conditional expression is shown in the following expression (3).
[0045]
[Equation 3]
G = ROI1 <ROI2 <ROI3 (3)
Here, ROIi (1 ≦ i ≦ 3) is a representative CT value of the region of interest i based on the projection data collected in the first scan.
[0046]
The setting contents of the condition setting (1) and the condition setting (2) can be confirmed or canceled by the icon in the lower area 80a of the window 80.
[0047]
FIG. 4 is a flowchart for explaining the operation of the real-time CT value monitoring system of the X-ray CT apparatus CT1 shown in FIG.
[0048]
First, the position of the subject P is set on the bed apparatus 5 (step S11), and the X-ray tube 31 is fixed to the upper part of the gantry 3 and the subject P is moved in the body axis direction to perform scanography ( Step S13). A scanogram 51 (see FIG. 1) obtained by this scanography is displayed on the display device 13.
[0049]
Next, with reference to this scanogram 51, scan plans for the reference image collection scan, the first scan, and the second scan for performing the first scan are created. At that time, scan conditions such as slice position 55, slice thickness, scan start position 53, scan end position 57, tube voltage, tube current and the like are set (step S15).
[0050]
Next, a reference image collection scan is performed (step S17), data is reconstructed by the reconstruction calculation device 37 (step S19), and a tomographic image 59 by the reference image collection scan is displayed on the display device 13 (step S21). ).
[0051]
Next, with reference to the scanogram 51 and the tomographic image 59, a plurality of regions of interest are set on the tomographic image 59, and a CT value condition for each region of interest and a logical operation expression between the CT value conditions for each region of interest are obtained. Is set. Further, a relative CT value condition among a plurality of regions of interest is set as necessary (step S23).
[0052]
After the setting in step S23 is performed and stored in the ROI condition memory 21, a contrast agent corresponding to the region to be contrasted is administered to the subject P (step S25), and the first scan is performed (step S27). Then, the image reconstruction of the tomographic image by the reconstruction device 9 and the update of the tomographic image 59 displayed on the display device 13 are performed (step S29).
[0053]
Next, the ROI position and shape stored in the ROI position information memory 39 are referred to by the reconstruction calculation device 37, and a representative CT value for each region of interest is calculated and stored in the image memory 11 (step S31).
[0054]
As this representative CT value, an average value for all the pixels in the region of interest is usually adopted, but it may be a median in the form of the distribution of CT data values in the region of interest. Depending on the application, the maximum value, minimum value, or extreme value in the region of interest may be used.
[0055]
Next, it is determined whether or not a logical function indicating an operation between CT value conditions of a plurality of regions of interest or a relative CT value condition between regions of interest is satisfied (step S33). If the condition is satisfied, the second scan is executed (step S37), and the process ends.
[0056]
If the condition is not satisfied in the determination of step S33, it is determined whether or not a predetermined time has elapsed since the start of the first scan or the administration of the contrast agent. If not, the CT of the region of interest is again determined. In order to monitor the value, the process branches to step S27 (step S35). If the predetermined time has elapsed, it is determined that a timeout has occurred, an error is reported, and error processing is performed as appropriate.
[0057]
The meaning of the determination of the elapse of the predetermined time in step S35 is to prevent meaningless repetition of the first scan when there is an error in contrast agent administration or an error in setting CT value conditions.
[0058]
Thus, the CT values of a plurality of regions of interest are monitored by the first scan, and a condition determination as to whether or not the representative CT value of each region of interest satisfies the set CT value condition, and an operation between these condition determinations Since the transition from the first scan to the second scan is determined by the result or by the relative CT value condition between a plurality of regions of interest, accurate contrast agent distribution is detected by determining the flexible CT value condition In addition, it is possible to perform scanning at the optimal contrast medium distribution timing.
[0059]
It should be noted that the condition determination as to whether or not the representative CT value of each region of interest satisfies the set CT value condition, or the relative CT value condition between a plurality of regions of interest uses not only mere size comparison but also fuzzy logic. Also good.
[0060]
FIG. 5 illustrates membership functions 91 to 95 when fuzzy logic is used for comparison between the representative CT value (ROI1) of the region of interest 1 and the representative CT value (ROI2) of the region of interest 2.
[0061]
In the above-described embodiment, the number of regions of interest may be two or more, and any logic can be set in a logical operation expression (logic function) between CT value conditions of a plurality of regions of interest.
[0062]
The above embodiments can be applied to both single-slice X-ray CT apparatuses and multi-slice X-ray CT apparatuses. In the latter case, it is possible to set a plurality of regions of interest to be subjected to CT value monitoring by dispersing them in multi-slice tomographic images.
[0063]
According to the present embodiment, since CT values are monitored by a plurality of regions of interest, there is no need to always grasp high accuracy in a single region of interest as in the prior art, and there are fewer restrictions on specifying the region of interest. It was.
[0064]
In the present embodiment, the condition of the representative CT value of the region of interest is accurately determined with respect to disturbances such as body movement of the subject in the first scan, and the CT values of a plurality of regions of interest are monitored to detect these CT values. This is suitable for obtaining a contrast medium distribution image with a small amount of contrast medium by flexibly determining the contrast state by various calculations in between.
[0065]
Next, an X-ray CT apparatus CT2 according to the second embodiment of the present invention will be described with reference to FIGS. FIG. 6 is a block diagram of the X-ray CT apparatus CT2.
[0066]
As in the first embodiment, the X-ray CT apparatus CT2 according to the second embodiment calculates the CT value of the region of interest that has been reconstructed from the inspection system A2 that collects scan data and the monitoring image. And a control system C2 that recognizes a significant attribute of the CT value in light of setting conditions and gives a control command CM, and further has a configuration and a function described below. The reconstruction device 9 of the monitoring system B2 includes a projection data pre-processing unit 9a, and the output device 13 includes a monitor 13a that can interact as a peripheral device of the console.
[0067]
In the X-ray CT apparatus CT2, a table in which various monitoring conditions are preset is stored in the condition memory 121 via the control unit 141, and the contents of the table are necessary for the image processing apparatus 100, the determination unit 43, and the control unit 141. It can be read and set or processed appropriately according to the above.
[0068]
FIG. 7 shows an example of a table stored in the condition memory 121, where (a) is an inspection object table 150, and (b) is a parameter table 160 in a lower layer of the inspection object table 150.
[0069]
The examination target table 150 is a table listing various contrast examination targets by organ, case, etc., and is displayed on the monitor 13a. One or more items (for example, liver) in the displayed table 150 are displayed. And a cancer) are selected, a parameter table 160 in which a parameter group corresponding to or in common (for example, liver cancer parameter group 1a) is selected and displayed as a list is displayed on the monitor 13a.
[0070]
Each parameter group is displayed, for example, by classification according to imaging conditions, display conditions, trigger conditions, etc. If the imaging conditions are used, it is divided into intermittent scans, synchronous scans, etc., and is further displayed in detail according to the low dose mode, site, etc. . Display conditions include a distinction between a plurality of images, graph display, etc., and the name of an image used for applying a trigger. When a specific image name is selected, an example CT image 171 is displayed in an image window 170 as shown in FIG. 8A, for example. In the case of the trigger condition, the CT value, the CT value change rate, the number of ROIs, the calculated CT value range, the ROI region, and the like are displayed as parameters. When a specific parameter, for example, a CT value is selected, as shown in FIG. When a CT value curve 181 is shown in the CT value monitoring window 180 and the ROI region is selected, for example, the ROI display 172 or the representative CT value display 173 as shown in FIGS. 8A and 8B is made.
[0071]
In addition, a representative guide display is also provided. For example, when selecting conditions for timing of the arterial phase in liver cancer, the conditions are set, and a guide on where and when to be stained with contrast medium Display is made.
[0072]
Such conditions can be incorporated into the shooting plan.
[0073]
According to this embodiment, it is not necessary to set complicated trigger conditions for each inspection, and it is possible to save time and worry about erroneous operation at the time of setting.
[0074]
Next, an X-ray CT apparatus CT3 according to a third embodiment of the present invention will be described with reference to FIGS. FIG. 9 is a block diagram of the X-ray CT apparatus CT3.
[0075]
The X-ray CT apparatus CT3 according to the third embodiment includes an inspection system A3, a monitoring system B3, and a control system C3 having the same functions as those of the second embodiment. It has a function.
[0076]
In this embodiment, the control system C3 has a mode switching unit 210 between a single slice mode and a multi-slice mode, and a data table corresponding to the following functions is preset in the condition setting unit 221 and selected. Data is processed by the image processing apparatus 200, and a plurality of images are simultaneously displayed on the monitor 13a.
[0077]
FIG. 10 shows an example of a plurality of images displayed on the screen of the monitor 13a in the single slice mode in which the slice thickness can be switched in a short time. (A) is the same tomographic plane attribute emphasizing screen 250, (b) is the same. It is a display screen 260 when the tomographic plane is scanned at different times.
[0078]
The attribute emphasis screen 250 displays standard images 251 and 252 that are emphasized in different ways. The condition setting unit 221 can set the attribute emphasis in accordance with the attribute contents such as use of different windows, processing by different functions, juxtaposition of difference images, enlargement, zooming, and the like. As a result, the viewpoint is narrowed down, and the contrast is increased due to the difference in average level or the difference in light and shade, and it is possible to capture even a light change such as a thin blood vessel or a light stain.
[0079]
The different time display screen 260 shows a current standard image 261 of a certain tomographic plane and a processed image 262 of the tomographic plane at different times, so that, for example, CT values of the region of interest to be monitored up to now can be displayed. You can see the magnitude of the change. In addition, it is possible to monitor the CT data in an effective phase by grasping the heartbeat and the respiratory state.
[0080]
FIG. 11A illustrates a plurality of slice images 271 to 274 displayed on the screen of the monitor 13a in the multi-slice mode, and FIG. 11B illustrates a slice position (detector row) corresponding to the images 271 to 274. This is a display example showing 281 to 284 in the body axis direction Z of the subject 280.
[0081]
The image processing apparatus 200 can perform the above image processing in combination.
[0082]
One or a plurality of regions of interest can be set for each tomographic image displayed on the monitor 13a. In such a multi-slice in which different slice planes are collected almost simultaneously, when setting ROI for each slice plane, if the running state of the blood vessel is inappropriate for setting ROI (eg, each first slice of different blood vessels) In this embodiment, one is clogged, the other is in good running, and the second slice plane is conversely the former in good running and the latter is clogged). The slice position tomogram is displayed, and therefore the trigger timing accuracy can be improved.
[0083]
In the above embodiment, when the region of interest is set to a relatively large blood vessel of the subject, and the contrast agent is flowed through the blood vessel to perform continuous monitoring of the average CT value, there is no movement if the subject is a phantom, Although the region of interest does not deviate, when the subject is a human body, the scan position of the region of interest deviates from the set position due to a biological phenomenon such as coughing or sneezing.
[0084]
How the CT value changes due to the deviation of the scan position depends on what is in the shifted area. Even if there is an organ similar to the one before the shift, if sufficient contrast agent does not reach there, the average CT value does not reach the threshold value even if time passes, and the second scan is automatically started. There is nothing. In this case, the presence or absence of the contrast agent is visually confirmed on the screen, and the second scan is started at the operator's discretion.
[0085]
If there is an organ with a high CT value, such as a bone, in the shifted region, the average CT value exceeds the threshold simultaneously with the shift, and the second scan is started at an inappropriate timing.
[0086]
Although it is possible to set the region of interest to be small so that it does not protrude from the desired region even if there is a slight deviation, this is not an essential solution and the average CT value is It becomes easy to be affected.
[0087]
Therefore, it is conceivable to constantly monitor the movement of the subject and correct the coordinates of the region of interest defined in the coordinate system of the inspection system according to the change in the coordinate system of the subject. Requires considerable computer resources, and if the coordinates are corrected in the body axis direction of the subject, it is difficult to interpret the CT image in the second scan, and sufficient clinical applicability cannot be maintained. Is done.
[0088]
In view of this point, an X-ray CT apparatus CT4 according to a fourth embodiment of the present invention will be described below with reference to FIGS. FIG. 12 is a block diagram of the X-ray CT apparatus CT4.
[0089]
The X-ray CT apparatus CT4 according to the fourth embodiment includes an inspection system A4, a monitoring system B4, and a control system C4 having functions equivalent to those of the above-described embodiments. It has a function.
[0090]
In the X-ray CT apparatus CT4, the control system C4 includes an average CT value monitoring unit 343 including input / output interfaces such as a scan control unit 41 and a ROI setting monitor 313. The ROI setting monitor 313 may be the same screen as the real-time reconstructed image display unit 13 of the monitoring system B4, and the average CT value monitoring unit 343 has a region of interest setting function, a monitoring condition setting function, and a determination function. Are shown as components of the control system C4, but may be included in the monitoring system B4.
[0091]
The X-ray CT apparatus CT4 is configured to detect the movement of the subject and temporarily stop activation of the second scan by CT value monitoring.
[0092]
More specifically, when setting the position and shape of the region of interest (hereinafter referred to as “normal ROI”) in the manner described above for the real-time CT value monitoring system, an additional region of interest (hereinafter “ Called “Stop ROI”). As the position of the stop ROI, a part where the average CT value does not substantially change even if time passes if a subject does not move in a predetermined tomographic image or a part with little change, such as the spine, is selected. Here, description will be made on the assumption that “normal ROI = 1, stop ROI = 1”.
[0093]
When setting each region of interest, the monitoring condition is set in the average CT value monitoring unit 343. The monitoring condition includes a threshold value of the average CT value in the case of the normal ROI, and includes a CT value condition that defines an allowable fluctuation range of the average CT value in the case of the stop ROI.
[0094]
The average CT value monitoring unit 343 gives a monitoring signal MS for notifying the scanning control unit 41 of various monitoring results. When the average CT value of the normal ROI exceeds the threshold value, the monitoring signal MS is in a signal state that allows the output of the start command for the second scan, and the average CT value of the stop ROI deviates from the specified range. During this time, the signal state does not allow the start command to be output.
[0095]
Accordingly, it is possible to prevent as much as possible a situation in which the second scan starts at an inappropriate timing due to an unexpected movement of the subject.
[0096]
Next, the operation of the control system C4 will be described with reference to FIGS.
13 to 15 are display examples of the screen 313a of the monitor 313. FIG. Although this screen 313a is considered as a screen of the monitor 313 for convenience of explanation, it may be a screen of the real-time reconstruction display unit 13.
[0097]
As shown in FIG. 13A, the screen 313a includes a reference image window 313b and a CT value monitoring window 313c.
[0098]
The reference image window 313b displays a CT image 350 obtained by scanning for reference image collection, and the CT value monitoring window 313c displays an average CT value 360 and a monitoring condition 370 of each ROI.
[0099]
First, in step S41, a reference image 350 is obtained.
[0100]
Next, in step S42, a normal ROI and a stop ROI are set as shown in FIG. Usually, the ROI is set as a circular region of interest 352 in a position where the movement of the contrast medium can be easily grasped in the vicinity of the organ 355 to be examined, for example, the blood vessel 351 constituting the aorta, and the stop ROI is misaligned. For example, it is set as, for example, a rectangular region of interest 354 at a position where the average CT value changes significantly, for example, at a part of the spine 353 including the boundary surface with other organs.
[0101]
Monitoring conditions necessary for setting the region of interest are set, and monitoring of the average CT value starts at t = T0. As shown in FIG. 14A, the monitoring condition includes a threshold value H for the average CT value CT (n) of the normal ROI, a specified width W for the average CT value CT (s) of the stop ROI, and a continuous scan limit. Includes time.
[0102]
Thereafter, a contrast medium is injected and the completion of the injection is notified.
[0103]
In step S43, the first scan is started. In step S44, average CT values CT (n) and CT (s) of the normal ROI and the stop ROI are calculated.
[0104]
In step S45, it is determined whether the elapsed time (t−T1) of the first scan is within the set time limit. If the time limit has passed (NO), the flow proceeds to step S46, and the first scan To stop. If it is within the time limit (YES), the process proceeds to step S47.
[0105]
In step S47, as illustrated in FIG. 14A or FIG. 15A, it is determined whether the average CT value CT (n) of the normal ROI rises due to the arrival of the contrast medium or other reasons and exceeds the threshold value H. . If the average CT value CT (n) exceeds the threshold value H (YES), the flow proceeds to step S48. It should be noted that the average CT value CT (n) of the normal ROI in FIG. 15 (a) indicates that the subject moves sideways as shown in FIG. 15 (b) unexpectedly (t = T3) and the normal ROI set position The threshold value H is exceeded because the 352 is displaced from the blood vessel 351 and protrudes to the peripheral portion having a relatively high CT value.
[0106]
In step S47, if the average CT value CT (n) does not exceed the threshold value H (NO), the flow goes to step S44, and the average CT values CT (n) and CT (s) are renewed in the next clock frame. Calculate That is, the first scan is continued.
[0107]
In step S48, it is determined whether the average CT value CT (s) of the stop ROI is within the range of the specified width W. As shown in FIG. 14 (b), when the dense flow of contrast medium starts to arrive (t = T2), the setting region 354 of the stop ROI is substantially the same as the portion of the spine 353 that is the initial setting target If it is in the position, as shown in FIG. 14A, the average CT value CT (s) of the stop ROI is held in the range of the specified width W (YES), and therefore the flow proceeds to step S49, substantially. The start of the second scan is allowed at time t = T2.
[0108]
However, as shown in FIG. 15B, when the set position 354 of the stop ROI is shifted from the spine 353 and moves to the peripheral portion having a relatively low CT value, the average CT of the stop ROI is shown in FIG. Since the value CT (s) deviates from the specified width W and does not exist within the range of the specified width W (NO), the flow goes to step S44 and the first scan is continued. That is, the process cannot proceed to step S49, and the start of the second scan is not permitted.
[0109]
A plurality of normal ROIs and one stop ROI may be used.
[0110]
In this case, the first ROI and the stop ROI are monitored by the control flow of FIG. 16, and the other normal ROIs are considered as a plurality of regions of interest in the first embodiment and are monitored by the control flow of FIG. Therefore, a control method is adopted in which an affirmative (YES) flow in step S48 in FIG. 16 is interrupted between steps S31 and S33 in the control flow in FIG.
[0111]
【The invention's effect】
As is clear from the above, according to the present invention, an appropriate number of regions of interest are set in the first scan, and each CT value is monitored with a necessary accuracy according to the situation. By using them selectively or in combination between regions of interest, a decision base equal to or better than always grasping the CT value of a single region of interest with high accuracy can be obtained, and the second scan can be performed appropriately. Can be executed at the timing.
[Brief description of the drawings]
FIG. 1 is a block diagram of an X-ray CT apparatus according to a first embodiment of the present invention.
FIG. 2 is a display example of icons for setting a region of interest and a CT value condition of the X-ray CT apparatus of FIG. 1;
3 is a display example of a window for setting CT value conditions and arithmetic expressions between regions of interest of the X-ray CT apparatus of FIG. 1;
4 is a flowchart for explaining the operation of the X-ray CT apparatus of FIG.
FIG. 5 is a graph showing a fuzzy logic membership function applied to a CT value comparison determination between regions of interest of the X-ray CT apparatus of FIG. 1;
FIG. 6 is a block diagram of an X-ray CT apparatus according to a second embodiment of the present invention.
7 is an example of a table stored in a condition memory of the X-ray CT apparatus of FIG. 6, where (a) is an inspection object table and (b) is a parameter table.
8 is a display example of the monitor of the X-ray CT apparatus of FIG. 6, where (a) is an image window and (b) is a CT value monitoring window.
FIG. 9 is a block diagram of an X-ray CT apparatus according to a third embodiment of the present invention.
10 is an example of a monitor screen in the single slice mode of the X-ray CT apparatus of FIG. 9, in which (a) is an attribute emphasis screen and (b) is a time coordinate screen.
11A and 11B are examples of monitor screens in the multi-slice mode of the X-ray CT apparatus of FIG. 9, where FIG. 11A is a multi-slice screen, and FIG. 11B is a slice position display screen.
FIG. 12 is a block diagram of an X-ray CT apparatus according to a fourth embodiment of the present invention.
13 is a screen display example of the monitor of the X-ray CT apparatus of FIG. 12, (a) is an entire screen, and (b) is a display example of a reference image window.
14 is a screen display example of the monitor of the X-ray CT apparatus of FIG. 12, (a) is a normal display example of a CT value monitoring window, and (b) is a corresponding display example of a reference image window.
FIGS. 15A and 15B are screen display examples of the monitor of the X-ray CT apparatus of FIG. 12, in which FIG. 15A is an abnormal CT value display example of a CT value monitoring window, and FIG. 15B is a corresponding display example of a reference image window;
FIG. 16 is a flowchart illustrating a manual mode.
[Explanation of symbols]
CT1, CT2, CT3, CT4 ... X-ray CT system
A1, A2, A3, A4 ... Inspection system
B1, B2, B3, B4 ... Monitoring system
C1, C2, C3, C4 ... Control system
3 ... Scan stand, 5 ... Bed device, 7 ... Data collection unit, 9 ... Reconstruction device,
DESCRIPTION OF SYMBOLS 11 ... Image memory, 13 ... Display apparatus, 15 ... CPU, 17 ... Keyboard,
19 ... Mouse, 21 ... ROI condition memory, 31 ... X-ray tube, 33 ... Detector,
35 ... Projection data memory, 37 ... Reconstruction calculation device, 39 ... ROI position information memory, 41 ... Scan control unit, 43 ... Condition determination unit, 121 ... Condition memory, 150 ... Inspection object table, 160 ... Parameter table, 210 ... Single multi-mode switching unit, 250 ... attribute emphasis screen, 260 ... hourly screen, 270 ... multi-slice screen, 354 ... stop ROI

Claims (3)

In the X-ray CT apparatus that monitors the CT value of the region of interest by the first scan and executes the second scan for acquiring a clinical application image when the CT value satisfies a predetermined condition,
A region of interest setting means capable of setting a plurality of regions of interest to be monitored ;
Determination means for determining whether the CT value of the region of interest set by the region of interest setting means satisfies the predetermined condition;
Monitoring means for monitoring a change in CT value of another region of interest set by the region of interest setting means;
An X-ray CT apparatus comprising: control means for stopping activation of the second scan based on a result of monitoring by the monitoring means. In the multi-slice X-ray CT apparatus that performs the second scan for acquiring the clinical application image when the CT value of the region of interest is monitored by the first scan and the CT value satisfies a predetermined condition,
An X-ray CT apparatus comprising a region-of-interest setting means capable of setting a region of interest to be monitored for each of a plurality of different tomographic planes . Determination means for determining whether the CT value of the region of interest set by the region of interest setting means satisfies the predetermined condition;
Monitoring means for monitoring a change in CT value of another region of interest set by the region of interest setting means;
The X-ray CT apparatus according to claim 2 , further comprising: a control unit that stops activation of the second scan based on a result of monitoring by the monitoring unit.

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