JP2005287949A - Method of generating ct tomogram, and apparatus of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reliably and safely perform necessary scanning by utilizing a breath holding time without excess and shortage even in the case of a patient who moves irregularly and periodically. <P>SOLUTION: This method is provided with: a step of measuring a time passing after the start of breath holding of the patient; a step of scanning the patient while synchronizing with a prescribed signal and collecting data necessary for reconstituting a CT tomogram; a step of obtaining the passing time of breath holding required until the completion of scanning of the next time based on the passing time after the start of breath holding until the finish of scanning of this time; and a step of comparing the obtained passing time of breath holding with a prescribed breath holding threshold and controlling scanning of the next time according to the comparison result. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and apparatus for generating a CT tomogram, and more specifically, a CT that scans a subject a plurality of times while holding the subject in breath and generates a CT tomogram of the subject based on collected data. The present invention relates to a tomographic image generation method and apparatus.

  A typical scan of a subject that moves periodically is a cardiac scan. Cardiac scans capture a moving heart, so motion artifacts always occur. In order to reduce this, a method of acquiring an image having a predetermined cardiac phase synchronized with a heartbeat (R wave) is known.

  One is called a retrospective ECG-synchronized scan (or cardiac gating helical scan). Here, a helical scan of the heart region is performed, and at the same time, an electrocardiogram is separately measured by an electrocardiograph. Recording is performed, and later, projection data having a constant cardiac phase is extracted from each R-wave signal to reconstruct a CT tomographic image having a predetermined cardiac phase. However, this method is not suitable for obtaining a plurality of X-ray CT images continuous in the body axis direction, and in the helical scan in which X-rays are irradiated at all cardiac phases, it is a wasteful exposure to the subject. Therefore, the purpose of use is limited.

  The other is called a prospective ECG-synchronized scan (or cardiac gating cine scan). Here, an axial scan of a predetermined cardiac phase is performed in synchronization with the R wave signal, and X is adjusted accordingly. Line ON / OFF control is also performed. Therefore, useless exposure of the subject can be eliminated. However, since the average human breath-holding time is said to be about 30 seconds, if the scan spacing is short or the number of multi-detector columns is small (1 column, 2 columns, etc.), The entire heart cannot be scanned with a single breath hold, so it must be divided into several scans while breathing in.

Conventionally, when imaging moving parts such as the chest and abdomen, the total number of scans required for CT imaging of the subject is divided by the number of scans possible per breath holding time to generate multiple scan clusters. It is known that the obtained scan plan can be evaluated and adjusted on the preview screen (Patent Documents 1, 2, etc.). In the chest and abdominal scans, the required number of scans can be performed reliably while holding the breath, so a series of cluster scans can be executed reliably and safely.
JP 2002-066561 (FIG. 7, “0012” to “0016”, etc.) JP 05-137714 (summary, figure)

However, in the cine scan synchronized with the heartbeat (R-pulse), since the heartbeat interval of the person is not constant, it is impossible to know in advance how many breaths should be inserted after the start of breath holding. Therefore, the scan plan cannot be evaluated and adjusted on the preview screen. If the total number of scans is divided into cluster scans every predetermined number as in the past, if the heart rate interval is long, the required number of scans cannot be performed during the breath holding time, and the heart rate If the interval is short, the required number of scans will be completed early in the breath holding time, and the breath holding time will remain.

  The present invention has been made in view of the above-described problems of the prior art. The object of the present invention is to use a breath holding time without excess or deficiency even for a subject that performs irregular periodic movement. An object of the present invention is to provide a CT tomographic image generation method and apparatus capable of reliably and safely performing a scan.

  The above problem is solved by the configuration of FIG. That is, the CT tomogram generation method of the present invention (1) scans the subject a plurality of times while holding the subject breathing, and generates a CT tomogram of the subject based on the collected data. Of measuring the elapsed time after the start of breath holding of the subject and scanning the subject in synchronization with a predetermined signal and collecting data necessary for reconstructing a CT tomogram A step of calculating a breath holding elapsed time required until the end of the next scan based on an elapsed time after the start of the breath holding until the end of the current scan, and a predetermined breath holding And a step of comparing the threshold value and controlling the next scan according to the comparison result.

  In the present invention (1), the next breath-holding elapsed time is obtained and compared with a predetermined breath-holding threshold value every time, so that the breath-holding time can be reduced even when scanning a subject with irregular periodic motion. It is possible to perform a required scan reliably and safely by using without excess or deficiency.

  In the present invention (2), in the present invention (1), there is provided a step of controlling the breathing of the subject according to a comparison result between the obtained breath holding elapsed time and a predetermined breath holding threshold. Therefore, the breathing control can be appropriately performed together with the scan control of the subject.

  In the present invention (3), in the present invention (2), the breath-holding control of the subject is performed without performing the next scan control when the obtained breath-holding elapsed time exceeds a predetermined breath-holding threshold value. . Therefore, after making full use of the breath-holding time and performing the required scan reliably and safely, the necessary breathing is entered without delay.

  In the present invention (4), in the present invention (1), the next scan control is continued when the obtained breath holding elapsed time does not exceed a predetermined breath holding threshold. Therefore, the next scan can be reliably performed within the breath holding time.

  In the present invention (5), in the present invention (1), the predetermined signal is an electrocardiogram signal. The present invention is suitable for application to cardiac scanning.

  In the present invention (6), in the above-mentioned present invention (5), the elapsed breath holding time required until the end of the next scan is expressed as “the elapsed breath holding time until the end of the current scan” + “movement of the subject in the body axis direction” It is obtained by calculation of “time” + “maximum value of heartbeat interval” + “delay time from detection of predetermined signal to start of scanning” + “scanning time”.

  Further, the CT tomogram generation device of the present invention (7) scans the subject a plurality of times while holding the subject in breath, and generates a CT tomogram of the subject based on the collected data. A measuring device for measuring an elapsed time after the start of breath holding of the subject, and data necessary for reconstructing a CT tomogram by scanning the subject in synchronization with a predetermined signal. Based on the scanning means to be collected, the elapsed time after the start of the breath holding until the end of the current scan, the calculating means for obtaining the elapsed time of the breath holding required until the end of the next scan, and the determined breath holding elapsed time are predetermined. And a control means for controlling the next scan according to the comparison result.

  In the present invention (8), in the present invention (7), the control means controls the breathing of the subject in accordance with a comparison result between the obtained breath holding elapsed time and a predetermined breath holding threshold.

  In the present invention (9), in the above-mentioned present invention (8), the control means performs breath connection control of the subject without performing the next scan control when the obtained breath holding elapsed time exceeds a predetermined breath holding threshold. Is what you do.

  In the present invention (10), in the present invention (7), the control means continues the next scan control when the obtained breath holding elapsed time does not exceed a predetermined breath holding threshold.

  In the present invention (11), in the present invention (7), the predetermined signal is an electrocardiogram signal.

  According to the present invention (12), in the present invention (7), there is provided a display means for indicating the progress of the scan control, the bar graph for updating the display mode of the unit section every time the unit scan is executed, and the breathing of the subject. And a message having an inside message and an icon for instructing the subject to hold his / her breath. Accordingly, it is possible to easily guide and display the progress of the scan during the scan execution in an easy-to-understand manner.

  In the present invention (13), in the above-mentioned present inventions (7) to (12), an imaging table mounted with a subject and movable in the body axis direction, and an interface means for connecting to an external electrocardiograph are provided. Further, the computing means calculates the breath holding elapsed time required until the end of the next scan as “the breath holding elapsed time until the end of the current scan” + “the movement time of the subject in the body axis direction” + “the maximum heartbeat interval” The value is obtained by calculating “value” + “delay time from detection of predetermined signal to start of scanning” + “scan time”.

  In the present invention (14), in the present invention (13), the maximum value of the heartbeat interval is a fixed value. The fixed value means a default value or a set value of the system. As a default value, for example, a maximum value of 3 seconds between heartbeats is conceivable. This corresponds to a heartbeat of 20 beats / minute and cannot normally occur. Of course, other values other than 3 seconds can be arbitrarily set.

  In the present invention (15), in the present invention (13), the maximum value of the heartbeat interval is a value obtained by adding a predetermined amount of margin to the average value of a plurality of immediately preceding heartbeat intervals. Since the heartbeat interval does not change abruptly, obtaining an average value of a plurality of immediately preceding heartbeat intervals is convenient for more accurately estimating the maximum value of the heartbeat interval at that time. Further, taking into account a predetermined margin includes adding a predetermined margin value to the average value, and multiplying the average value by a predetermined margin ratio (1.1, 1.2, etc.).

  In the present invention (16), in the present invention (7), the scanning means includes an X-ray tube and an X-ray detector facing each other with the subject interposed therebetween, and these X-ray imaging systems are connected to the subject body axis. And a scanning gantry means for obtaining projection data of the subject by rotating around. The present invention is suitable for application to an X-ray CT apparatus.

  As described above, according to the present invention, it is possible to reliably and safely perform a required scan by using a breath holding time without excess or shortage even when scanning a subject that performs irregular periodic movements. This greatly contributes to reducing the burden on patients and improving the reliability of imaging in cardiac scanning.

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 shows an X-ray CT according to the embodiment.
FIG. 2 is a configuration diagram of the main part of the apparatus. The apparatus includes a scanning gantry unit 30 that scans and scans the subject 100 with an X-ray fan beam XLFB, an imaging table 20 that places the subject 100 and moves it in the direction of the body axis CLb. The operation console unit 10 is provided for performing remote control of the units 30 and 20 and for an engineer to operate.

  In the scanning gantry 30, 40 is a rotary anode X-ray tube, 40 A is an X-ray controller, 50 is a collimator for limiting the X-ray slice width, 50 A is a collimator controller, and 90 is a large number aligned in the channel CH direction ( X-ray detectors in which X-ray detection elements of about n = 1000) are arranged in, for example, two rows L1 and L2 in the direction of the body axis CLb, 91 is the projection data of the subject based on the detection signal of the X-ray detector 90 A data acquisition unit (DAS: Data Acquisition System) 35 for generating and collecting gantry 35 that supports the X-ray imaging system so as to be rotatable around the subject body axis, 35A is a rotation control unit for gantry 35, 14 Is a control interface for exchanging various control signals and detection signals between the CPU 11a and the scanning gantry unit 30. Here, the control interface 14 has a function of receiving a heartbeat signal from an electrocardiograph 60 which will be described later and transmitting an X-ray irradiation timing to the X-ray control unit 40A and a function of transmitting a heartbeat signal to the central processing unit 11.

  The imaging table 20 includes a top plate (cradle) 21 on which the subject 100 is placed and put into and out of a bore (cavity) of the scanning gantry unit 30. The top plate 21 is moved up and down and linearly moved by the motor built in the imaging table 20.

  In the operation console unit 10, reference numeral 11 denotes a central processing unit that performs main control / processing (scan control, CT tomographic image reconstruction processing, etc.) of the X-ray CT apparatus, 11a denotes its CPU, 11b denotes RAM, ROM, etc. used by the CPU 11a A main memory (MM) comprising 12 a command and data input device including a keyboard and a mouse, 13 a display device (CRT) for displaying scan plan / progress information, CT tomogram, and the like, 15 a data collection A data collection buffer for temporarily accumulating projection data from the unit 91, and 16 for accumulating and storing projection data from the data collection buffer 15, as well as various application programs and various calculations / corrections necessary for the operation of the X-ray CT apparatus. Secondary storage device (hard disk device or the like) for storing data files for use.

Next, the operation of X-ray CT imaging with such a configuration will be described. The subject 100 is irradiated with the X-ray beam XLFB from the X-ray tube 40 in a state where the subject 100 is positioned in the cavity of the scanning gantry unit 30. In this state, the X-ray fan beam XLFB from the X-ray tube 40 passes through the subject 100 and enters the detector rows L1 and L2 of the X-ray detector 90 all at once. The data collection unit 91 generates projection data g ₁ (X, θ), g ₂ (X, θ) corresponding to each detection row output of the X-ray detector 90 and stores them in the data collection buffer 15. Here, X represents the channel number of the detector, and θ represents the projection (view) angle.

  Further, X-ray projection similar to the above is performed at each view angle θ where the scanning gantry 35 is slightly rotated, and thus projection data for one rotation of the scanning gantry is collected and accumulated. At the same time, the imaging table 20 is intermittently moved in the direction of the body axis CLb in accordance with the axial scan method, thus collecting and accumulating all projection data for the required imaging area of the subject, and storing them in the secondary storage device 16. To do. Then, the CPU 11a reconstructs a CT tomographic image of the subject 100 based on the projection data obtained after the end of all the scans or in parallel with the scans, and displays this on the display device 13.

  When performing cardiac cine scan, an electrocardiograph 60 is attached to the subject 100, the detection signal (electrocardiogram waveform) HBS is taken into the apparatus via the control interface 14, and is synchronized with the R wave signal. Then, cardiac cine scan control described later is performed.

  FIG. 3 is a flowchart of an X-ray CT imaging process according to the embodiment, and shows a case where a cardiac cine scan is performed in synchronization with a heartbeat signal. This process is executed by the CPU 11a. Preferably, after performing a scout scan of the subject 100 in advance, this process is input. In step S <b> 11, a scan plan screen for the subsequent axial scan of the subject 100 is displayed on the display unit 13. In step S12, an engineer or the like sets scan plan information.

FIG. 4 shows an example cardiac gating parameter setting screen. In the default state, the “scan” tag 13a is selected, which includes a “cardiac gating” button along with various scan parameters. When an engineer or the like presses the “cardiac gating” button, a cardiac gating parameter setting screen 13c is obtained. An example setting is
Trigger delay time from heartbeat signal to scan start (Trigger Delay) = 70%
Number of CT tomographic images to be reconstructed at each heartbeat interval (Images Per RtoR Interval) = 3 Time interval between CT tomographic images (Time Between Images) = 50 ms
It is. Any other combination can be selected for these settings. Other scan parameters are as illustrated.

Next, when the engineer or the like selects the “timing” tag 13b, the breath holding time setting screen of FIG. 5 is obtained, which includes setting icons for “breath holding time” and “breathing time”. The setting value is indicated by a bold line icon in the figure. An example setting is
Breath Hold Time = 30sec
Breath time = 20 sec
It is.

  Returning to FIG. 3, in step S13, an engineer or the like sets the recon plan information. In step S14, input of the setting confirmation button “CONFIRM” is awaited, and when it is input, scanning of the subject 100 is started in step S15 according to the set scan parameter. In step S16, it waits for the subject to be transported to a predetermined scan start position (in this example, the scan start position of the heart), and when transported, in step S17, the subject is voiced (auto voice) and / or displayed. Provide guidance on breath holding. Although not shown, at the same time, the breath holding monitoring timer is started. In step S18, a cine scan is performed in synchronization with the R wave.

  FIG. 6 shows a timing chart of cardiac cine scan control. Here, the electrocardiogram waveform will be briefly described. In the upper part of FIG. 6, assuming that the heart rate is 75 / min, the heart cycle is 800 ms, and an electrocardiogram waveform (P wave to U wave) as shown in this period appears. At the timing of the P wave, the atrium is excited (contracted), and blood flow from the vena cava and pulmonary vein flows into the ventricle. At the timing of the subsequent QRS wave, the atrium is subtracted from the excitement (contraction) and the ventricle is excited (contraction), whereby the blood flow stored in the ventricle is pushed out toward the aorta and the pulmonary artery. At the timing of the subsequent T-wave, the ventricle stops from excitement (contraction). And at the timing of the following U wave, the movement of the heart is the slowest. In a normal heart, such an electrocardiographic waveform is repeated almost regularly. However, even if the heart is normal, the heart rate varies depending on the physical condition of the subject. For example, if the heart rate is 120 / min, the heart cycle is 500 ms, and P waves to U waves as shown in the figure appear within this period.

In the illustrated example, R wave signals R1, R2, R3, etc. are observed with a period of 0.8 sec. In this cine scan, a total of three CT tomographic images of the center position and ± 50 ms before and after the center position are reconstructed (half-reconversion) around the cardiac phase of 70% of the cardiac cycle by detecting the signal R1. Scan the required viewing angle. X-rays are ON only during scanning, and other sections are OFF, so that unnecessary exposure of the subject can be avoided.

  The position of the 70% cardiac phase is preferably obtained as an average period for a plurality of immediately preceding periods and as a position delayed by an average period × 70/100 from the detection of the signal R1. If this center position is obtained, the scan time width necessary for performing the scan of the view angle necessary for reconstructing (half-reconstructing) a total of three CT tomographic images up to ± 50 ms before and after that center position (ie, scan Time) can be easily obtained. Therefore, the delay time (Xray On Delay) from the detection of the signal R1 to the start of scanning can be easily obtained.

  In this example, after the scan is completed, the subject is conveyed by a predetermined pitch (for example, 6 mm) in the body axis direction, and this movement takes about 0.7 sec. After the subject is transported, the next cine scan is performed after detection of the next signal R3.

  Returning to FIG. 3, it is determined in step S19 whether or not the required number of all scans has been completed. If not, the next breath holding elapsed time is predicted (calculated) in step S20. The lower part of FIG. 6 shows the continuation of the timing chart. Now, when the cine scan synchronized with the R wave signal Rn is finished, the breath holding elapsed time until the next cine scan is finished is predicted.

  The elapsed breath holding time required until the end of the next scan is “the elapsed breath holding time until the end of the current scan” + “the movement time of the subject in the body axis direction: ISD” + “the maximum value of the heartbeat interval: Max R to R ”+“ delay time from signal Rn to scan start: Xray On Delay ”+“ scan time: Scan Time ”.

  It should be noted that the “delay time from the signal Rn to the start of scanning” can vary with the variation of the heartbeat cycle. These can be calculated based on the average period at each time point. The “maximum value of the heartbeat interval” may be a system default value (for example, 3 seconds) or an arbitrary setting value set by an engineer. Alternatively, the “maximum value of the heartbeat interval” may be a value obtained by adding a predetermined amount of margin to the average value of a plurality of immediately preceding heartbeat intervals. Since the heartbeat interval does not change abruptly, it is convenient to estimate the maximum value of the heartbeat interval at that time. Further, taking into account a predetermined margin includes adding a predetermined margin value to the average value, and multiplying the average value by a predetermined margin ratio (1.1, 1.2, etc.).

  Returning to FIG. 3, in step S21, it is determined whether or not the predicted “breath-holding elapsed time”> “set value” (in this example, 30 seconds). If NO, the process returns to step S18 to return to the next cine. Perform a scan. The fact that the next cine scan can be completed within the breath holding time of the subject is guaranteed by the determination in step S21.

  If the determination in step S21 is YES, in step S22, the start of breath connection is guided by the voice (auto voice) and the breath message displayed on the operation monitor or the display means provided in the gantry. In step S23, the elapse of the set value of the breath connection time (in this example, 20 seconds) is awaited. Then, when the breathing time has elapsed, the process returns to step S17 to perform breath holding navigation and perform the next series of cine scans.

  Thus, when all the scans are completed in the determination in step S19, the process proceeds to step S24, and breathing navigation is performed. Although not shown, CT image reconstruction and screen display are performed in parallel with scanning.

FIG. 7 shows an example of the progress display of the cardiac cine scan control. Progress bar indicating progress of cine scan control parallel to the time axis display at the top of the figure
13d is displayed. This scan begins at position I50.00 in the body axis direction and ends at I167.00. The progress bar 13d has a shape in which rectangular areas corresponding to each scan are arranged at equal intervals on a horizontal bar graph, and the total number of scans is constant (known). However, since the breathing timing is unknown, a scan sequence without breathing is displayed.

  When scanning is actually started, the display mode of the progress bar 13d is updated every time one scan is performed. This update is performed by displaying the scanned rectangular area brightly in real time or changing the color. In the figure, it is indicated by a bold line. On the contrary, during the breathing time, the progress of the scan can be easily grasped by stopping the update of the progress bar 13d and displaying a message indicating that the breathing is being performed.

  In the above embodiment, since the subject is moved in the body axis direction for each scan, the breath holding elapsed time required until the end of the next scan is expressed as “breath holding elapsed time until the end of the current scan” + “subject The calculation is not limited to this, but is calculated by calculating the movement time of the specimen in the body axis direction + “maximum value of heartbeat interval” + “delay time from signal Rn to start of scanning” + “scanning time”. When multiple scans are performed without moving the subject in the body axis direction, the breath holding elapsed time required until the end of the next scan is excluded from the above-mentioned “movement time in the body axis direction of the subject”. This is obtained by the calculation of “the breath holding elapsed time until the end of scanning” + “the maximum value of the heartbeat interval” + “the delay time from the signal Rn to the start of scanning” + “the scanning time”.

  Moreover, although the example of the cine scan of the heart was described in the said embodiment, it is not restricted to this. In addition to the heart, the present invention can be applied to general scan targets (stomach, lungs, muscles, etc.) that perform irregular periodic motion.

  Moreover, although the application example to the X-ray CT apparatus of this invention was described in the said embodiment, it is not restricted to this. It is apparent that the present invention can be applied to a so-called MRI apparatus that images a spatial nuclear magnetization distribution of a subject by a nuclear magnetic resonance (NMR) method and other PET apparatuses.

  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. It is a principal part block diagram of the X-ray CT apparatus by embodiment. It is a flowchart of the X-ray CT imaging process by embodiment. It is a figure explaining the cardiac gating parameter setting screen by embodiment. It is a figure explaining the breath holding / breathing time setting screen by embodiment. It is a timing chart of cardiac cine scan control by an embodiment. It is a figure explaining the progress status display of the cardiac cine scan control by 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 Shooting table 21 Top board (cradle)
30 Scanning gantry unit 40 X-ray tube 50 Collimator 90 X-ray detector 91 Data collection unit 35 Gantry 60 ECG 100 Subject

Claims (16)

A CT tomogram generation method for scanning a subject a plurality of times while holding the subject in breath, and generating a CT tomogram of the subject based on collected data,
Measuring the time elapsed since the start of breath holding of the subject;
Scanning a subject in synchronization with a predetermined signal and collecting data necessary to reconstruct a CT tomogram; and
Based on the elapsed time after the start of breath holding until the end of the current scan, obtaining the elapsed time of breath holding required until the end of the next scan;
A method for generating a CT tomogram, comprising: comparing the obtained breath-hold elapsed time with a predetermined breath-hold threshold and controlling a next scan according to the comparison result. The CT tomographic image generation method according to claim 1, further comprising a step of controlling breathing of the subject according to a comparison result between the obtained breath holding elapsed time and a predetermined breath holding threshold. 3. The CT tomographic image generation method according to claim 2, wherein the breath-holding control of the subject is performed without performing the next scan control when the determined breath-holding elapsed time exceeds a predetermined breath-holding threshold value. 2. The CT tomographic image generation method according to claim 1, wherein the next scan control is continued when the obtained breath holding elapsed time does not exceed a predetermined breath holding threshold. 2. The CT tomogram generation method according to claim 1, wherein the predetermined signal is an electrocardiogram signal. The elapsed breath holding time required until the end of the next scan is “the elapsed breath holding time until the end of the current scan” + “the movement time of the subject in the body axis direction” + “the maximum value of the heartbeat interval” + “predetermined signal 6. The CT tomographic image generation method according to claim 5, wherein the CT tomographic image generation method is obtained by calculating “delay time from detection to start of scanning” + “scanning time”. A CT tomographic image generating device that scans a subject a plurality of times while holding the subject in breath and generates a CT tomographic image of the subject based on collected data,
A measuring means for measuring an elapsed time after the start of breath holding of the subject;
Scanning means for scanning a subject in synchronization with a predetermined signal and collecting data necessary for reconstructing a CT tomogram; and
Based on the elapsed time after the start of breath holding until the end of the current scan, calculating means for calculating the elapsed time of breath holding required until the end of the next scan;
A CT tomographic image generating apparatus, comprising: a control unit that compares the obtained breath holding elapsed time with a predetermined breath holding threshold and controls a next scan according to the comparison result. 8. The CT tomographic image generating apparatus according to claim 7, wherein the control means controls breathing of the subject according to a comparison result between the obtained breath holding elapsed time and a predetermined breath holding threshold. 9. The CT tomographic image according to claim 8, wherein the control means performs breath breath control of the subject without performing the next scan control when the determined breath hold elapsed time exceeds a predetermined breath hold threshold. Generator. 8. The CT tomographic image generation apparatus according to claim 7, wherein the control means continues the next scan control when the obtained breath holding elapsed time does not exceed a predetermined breath holding threshold. The CT tomogram generation device according to claim 7, wherein the predetermined signal is an electrocardiogram signal. Display means for indicating the progress of scan control, a bar graph for updating the display mode of the unit section every time a unit scan is executed, a message indicating that the subject is breathing, and instructing the subject to hold breath The CT tomogram generation device according to claim 7, further comprising: an icon. An imaging table that carries the subject and can move in the body axis direction;
Interface means for connecting to an external electrocardiograph,
The calculation means calculates the breath holding elapsed time required until the end of the next scan by “the breath holding elapsed time until the end of the current scan” + “the movement time of the subject in the body axis direction” + “the maximum value of the heartbeat interval” + 13. The CT tomographic image generation apparatus according to claim 7, wherein the CT tomographic image generation apparatus according to claim 7 is obtained by calculation of “delay time from detection of a predetermined signal to start of scanning” + “scan time”. 14. The CT tomographic image generation device according to claim 13, wherein the maximum value of the heartbeat interval is a fixed value. 14. The CT tomogram generation device according to claim 13, wherein the maximum value of the heartbeat interval is a value obtained by adding a predetermined amount of margin to an average value of a plurality of immediately preceding heartbeat intervals. The scanning means includes an X-ray tube and an X-ray detector that are opposed to each other with the subject interposed therebetween, and scans for acquiring projection data of the subject by rotating these X-ray imaging systems around the subject body axis 8. The CT tomographic image generating apparatus according to claim 7, comprising a gantry means.

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