JP2003319934A - X-ray computer tomography apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reset the scan condition of main-scan to the variation of the physiological phenomenon of an object in a bolus tracking method operated by an X-ray computer tomography apparatus. <P>SOLUTION: The X-ray computer tomography apparatus comprises: a determination unit configured to determine, on the basis of data of a physiological phenomenon of the object measured in a period between the start of injection of the contrast medium or the pre-scan and the end of the pre-scan, the necessity of resetting a scan condition for the main-scan which is initially set on the basis of data of the physiological phenomenon of the object measured before injection of the contrast medium; and a scan condition setting unit configured to reset, when the determination unit determines that it is necessary to reset the scan condition, the scan condition for the main-scan from the initially set scan condition to a scan condition corresponding to the data of the physiological phenomenon measured in the period between the start of injection of the contrast medium or the pre-scan and the end of the pre-scan. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray computed tomography apparatus having a function of allowing a contrast agent to flow into a region to be imaged in a prescan before a main scan.

[0002]

2. Description of the Related Art In imaging a contrast medium, it is important to start a scan (main scan) at the timing when the contrast medium administered to a subject flows into a region of interest. Therefore, the scan (pre-scan) is performed before the main scan. In order to suppress the exposure dose, X-rays lower than those in the main scan are used in the prescan. The projection data collected by the prescan is used for real-time reconstruction processing. The image (tomographic image) reconstructed in real time is displayed immediately. The radiographer visually recognizes the contrast agent concentration (shading degree) of the region of interest on the image. The radiographer presses the trigger button of the main scan when it is determined that the concentration of the contrast agent in the region of interest has reached the planned concentration. When the trigger button is pressed, the prescan is stopped and the main scan preparation (setup) is started. The preparation for the main scan includes the work of moving the bed to the scheduled scan range, the work of accelerating the bed to the scheduled speed, the work of accelerating the rotating frame to the scheduled scan speed, heating the filament, and the like. The main scan is started when the preparation for the main scan is completed.

A technique called a bolus tracking method has been developed which automates the work of the photographer pressing the trigger button of the main scan. In the bolus tracking method, the CT value or average value of the region of interest from the prescan image is compared against a threshold value. Region of interest C
When the T value or the average value exceeds the threshold value, the prescan is stopped and the preparation for the main scan is started.

By the way, in the X-ray computed tomography apparatus, there is known an electrocardiographic gated scanning method in which scanning is performed in synchronization with an electrocardiogram waveform to obtain one or a series of images of a specific time phase. In this method, in order to reduce motion artifacts due to the movement of the heart, the time required for the X-ray tube to make one rotation (scan speed) is required to be sufficiently shorter than the heartbeat cycle.

In electrocardiographic gated scanning, a short scan speed of, for example, 500 msec is required to reduce motion artifacts to some extent and maintain diagnostic value. It is not easy to realize the condition that the scan speed is 500 msec.

Therefore, the scan speed is 1 second or 0.
A technique called ECG gated reconstruction (segment scan) was developed as a technique for reducing motion artifacts with a relatively popular machine such as 5 seconds. In this segment scan, ECG data is acquired in parallel with the acquisition of projection data. Based on the electrocardiogram data, data (segment) within a partial period centered on a specific heartbeat time phase is cut out from the projection data set of each heartbeat cycle. A plurality of segments cut out from a plurality of heartbeat cycles are joined together. As a result, 36 required for image reconstruction
The projection data for 0 ° is aligned.

In segment scanning, the number of segments to be collected is often preset. When the time width of the segments is short, the number of segments that need to be collected increases, but the time resolution of the image increases. That is, the number of images with different heartbeat time phases increases. Conversely, when the time width of the segments is long, the number of segments that need to be collected decreases, but the time resolution of the image decreases. If the number of segments to be collected is less than the expected number, it is impossible to obtain an image with the expected time resolution. In order to obtain an image with a scheduled time resolution, at least projection data for the heart rate corresponding to the planned number of segments to be collected is required.

Segment scans are susceptible to motion artifacts. Therefore, the sigh is held. There is a limit to how long you can hold your breath. In segment scanning, it is necessary to collect projection data for the required heart rate within a limited breath-hold period. Therefore, in the segment scan, it is necessary to measure the heart rate (heart rate) of the subject in advance and adjust the scan speed, that is, the time required for the X-ray tube to make one rotation, according to the heart rate. To be done.

As described above, in the bolus tracking method, the prescan is executed before the main scan. When the segment scan is applied to the main scan, the time difference between setting the scan speed and starting the main scan becomes long. Therefore, the heart rate during the main scan may fluctuate greatly with respect to the heart rate when the scan speed is set. Therefore, there may arise a problem that the scan speed of the main scan is not appropriate for the actual heart rate at that time. This problem becomes more prominent in contrast examination. The reason is that the heart rate often fluctuates greatly due to the injection of the contrast medium.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to enable resetting of scan conditions for main scan in response to changes in biological phenomena of a subject in a bolus tracking method using an X-ray computed tomography apparatus. It is in.

[0011]

According to a first aspect of the present invention, a prescan is performed on a contrast-injected subject using relatively low x-rays, and thereafter:
In an X-ray computed tomography apparatus that executes a main scan for collecting data on the subject using relatively high X-rays, from injection of the contrast agent or start of the prescan to end of the prescan. Based on the biological phenomenon data of the subject measured within the period,
Judgment configured to judge whether it is necessary to reset the scan condition of the main scan that is initially set based on the biological phenomenon data of the subject measured before the injection of the contrast agent Section and the determination section determines that the scan condition needs to be reset, the scan condition of the main scan is changed from the initially set scan condition to the injection of the contrast medium or the scan condition. A scan condition setting unit configured to reset the scan condition corresponding to the biological phenomenon data measured within a period from the start of the prescan to the end of the prescan. The second aspect of the present invention is
Performing a pre-scan on a subject injected with a contrast agent using relatively low X-rays, and then collecting data using a relatively high X-ray on the subject In an X-ray computed tomography apparatus that executes a main scan, the main scan is performed based on biological phenomenon data measured within a period from the injection of the contrast agent or the start of the prescan to the end of the prescan. And a scan condition setting unit configured to set the scan condition. A third aspect of the invention is to perform a pre-scan on a subject injected with a contrast agent using relatively low x-rays, and then to a relatively high x-ray for the subject. In an X-ray computed tomography apparatus that executes a main scan for collecting data using lines, the measured biological phenomenon data is displayed as a time graph and numerical values, and an input field relating to scan conditions of the main scan is displayed. A display unit configured to display, an input unit configured to input a scan condition of the main scan in the input field, the contrast agent injection or the prescan from the start to the end of the prescan Scans configured to set the scan conditions of the main scan according to the scan conditions entered within the period between ; And a matter setting unit.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An X-ray computed tomography apparatus according to the present invention will be described below with reference to the accompanying drawings with reference to the accompanying drawings. The X-ray computed tomography apparatus includes a rotation / rotation (ROTATE / ROTATE) type in which an X-ray tube and a radiation detector rotate as a unit around the subject, and a large number of ring-shaped detection elements arranged in an array. Fixed / rotation (STATIONARY / ROTAT) in which only the X-ray tube rotates around the subject.
There are various types such as E) type, and the present invention can be applied to any type. Here, the rotation / rotation type which is currently the mainstream will be described.

Further, the image reconstruction method mainly requires projection data of 360 ° for one round around the subject 360.
There is a ° method and a half scan method which requires projection data for 180 ° + fan angle. The present invention can be applied to any reconstruction method. Here, the 360 ° method will be described as an example.

The mechanism for converting incident X-rays into electric charges is an indirect conversion type in which X-rays are converted into light by a phosphor such as a scintillator and the light is further converted into electric charges by a photoelectric conversion element such as a photodiode. The mainstream is the direct conversion type utilizing the generation of electron-hole pairs in the semiconductor by X-rays and their movement to the electrode, that is, the photoconductivity phenomenon. Any of these methods may be adopted as the X-ray detection element, but here, the former indirect conversion type will be described.

Further, in recent years, commercialization of a so-called multi-tube type X-ray CT apparatus in which a plurality of pairs of an X-ray tube and an X-ray detector are mounted on a rotating ring has been advanced, and development of peripheral technologies thereof has been advanced. I'm out. In the present invention, the conventional one-tube type X-ray CT is used.
It is applicable to both the apparatus and the multi-tube type X-ray CT apparatus. Here, the one-tube type will be described.

Further, in the X-ray computed tomography apparatus, a single-slice type X-ray detector having a single detection element array in which a plurality of X-ray detection elements are arranged along the channel direction, and a plurality of detection element arrays are provided. There is a multi-slice type X-ray detector provided in parallel with each other in the slice direction, but any of these types may be adopted in the present invention. Here, the former single-slice type X-ray detector will be described as an example. .

FIG. 1 shows the configuration of the main part of the X-ray computed tomography apparatus according to this embodiment. The gantry 5 houses an X-ray tube and an X-ray detector. The X-ray tube is mounted together with the X-ray detector on a rotating frame having a ring shape. The X-ray tube faces the X-ray detector across the imaging space. The subject placed on the bed 7 is placed in the imaging space of the gantry 5. The bed 7 moves in the longitudinal direction. Generally, the body axis of the subject is substantially parallel to the longitudinal axis of the bed and the rotation axis of the X-ray tube. The direction parallel to the rotation axis of the X-ray tube is called the slice direction. X-ray tube
In order to generate X-rays, a tube voltage is applied from the high voltage generator and a filament current is supplied. The X-rays that have passed through the subject generate charges in each X-ray detection element of the X-ray detector. This charge is extracted as a current signal. This current signal is converted into a voltage signal by the data acquisition unit (DAS),
It is amplified and converted into a digital signal. The digital signal is stored in the storage device as projection data via the slip ring and the preprocessing unit together with the electrocardiogram data.
The image reconstruction unit reconstructs the image data based on the projection data for 360 °. The image reconstruction unit has an ECG gated reconstruction function. In the electrocardiographic synchronization reconstruction function, data (segments) within a partial period centered on a specific heartbeat time phase is cut out from the projection data set of each heartbeat cycle based on the electrocardiogram data. A plurality of segments cut out from a plurality of heartbeat cycles are joined together. As a result, the projection data for 360 ° necessary for image reconstruction is aligned. Image data corresponding to a specific heartbeat time phase is reconstructed based on the aligned 360 ° projection data. The reconstructed image data is displayed on the display 8 via the display control unit 10.

The biological phenomenon measuring device 4 measures the biological phenomenon of a subject. The biological phenomenon includes heartbeat (movement of the heart), respiration, and the like. Here, the biological phenomenon will be described as “heartbeat”. The electrocardiograph 4 detects an electrical phenomenon of the heart via an electrode attached to the subject, and outputs electrocardiogram data representing a time change of the electrical phenomenon. The biological phenomenon monitoring unit 2 is connected to the electrocardiograph 4. The biological phenomenon monitoring unit 2 calculates the heart rate per minute, that is, the heart rate based on the electrocardiogram data. In addition, the biological phenomenon monitoring unit 2 determines, based on the calculated heart rate, the current time for the heart rate at a specific time point, specifically, when measuring the heart rate referred to when the main scan condition is initially set. It is determined whether or not the fluctuation of the heart rate exceeds a predetermined value. When the fluctuation of the heart rate exceeds a predetermined value, the biological phenomenon monitoring unit 2 outputs a signal urging the resetting of the main scan condition to the scan condition selecting unit 1 together with a signal indicating the heart rate. That is, the biological phenomenon monitoring unit 2 determines whether it is necessary to reset the main scan condition based on the heart rate of the subject. The fluctuation of the heart rate is calculated as a difference or a change rate of the current heart rate with respect to the heart rate referred to when the main scan condition is initially set before the injection of the contrast agent.

When the scan condition selection unit 1 receives from the biological phenomenon monitor unit 2 a signal prompting the resetting of the scan condition, the scan condition selection unit 1 selects the optimum or approximate scan condition for the heart rate received together with the signal. decide. Actually, the scan condition selection unit 1 selects the scan condition corresponding to the heart rate from the table that is previously written in the storage medium such as the semiconductor memory, the magnetic disk, or the magneto-optical disk included in the data storage unit 6.

In the table, for example, as shown in FIG. 2, a plurality of sections are set for the heart rate (HR), and a plurality of helical pitches (HP) and scan speeds are associated with the plurality of sections. There is. In Figure 2,
Although the tables are organized so that the division regarding the heart rate (HR) is different between the helical pitch and the scan speed, they may be divided into the same division. The helical pitch is a scanning condition used in helical scanning, and can be defined as a moving distance (mm) of the bed 5 that moves during one rotation of the X-ray tube. The scan speed can be defined as the time (sec) required for the X-ray tube to make one rotation.

In the table, a relatively high scan rate is associated with a relatively high heart rate, and a low scan rate is associated with a low heart rate. Further, in the table, a relatively long helical pitch is associated with a relatively high heart rate, and conversely, a short helical pitch is associated with a low heart rate. With such correspondence, the main scan (helical scan) completes a predetermined scan range within a predetermined time, secures the necessary number of segments in the ECG gated reconstruction method, and has an excessive time resolution. It is realized to reset the main scan condition so as to prevent the deterioration.

In addition to the helical pitch and the scan speed, the scan conditions include the scan range, the maximum scan time that allows breath-holding (the upper limit of the scan time), and the minimum required segment for the ECG gated reconstruction method. It includes the number, a specific heartbeat time phase (delay time from the R wave of the electrocardiogram), the tube voltage, the tube current, the slice width, and the like. Among these scanning conditions, the helical pitch and scanning speed are sensitive to the heart rate. For example, if the heartbeat slows down and the heart rate decreases, scan speed must be slowed down and helical pitch must be shortened.
ECG gated reconstruction does not have the required number of segments. On the other hand, when the scan speed is excessively slowed and the helical pitch is excessively shortened, the projection data collection is not completed over the entire planned scan range within the upper limit of the scan time. Conversely, when the heart beats faster and the heart rate rises, the scan speed is shortened, and even if the helical pitch is lengthened, the segment required for ECG-synchronous reconstruction is short in scan time. The number of projection data can be aligned and the collection of projection data over the entire scan range can be completed. However, if the scan speed is excessively high and the helical pitch is excessively long, there is room for improving the time resolution. In order to balance such a relationship, the helical pitch and the scan speed are appropriately determined for the heart rate in the above table.

Returning to FIG. The main scan condition data selected by the scan condition selection unit 1 is supplied to the scan control unit 3. The scan control unit 3 controls the rotation speed of the X-ray tube according to the supplied scan conditions, and the bed 7
Control the moving speed of. For example, the scan controller 3
The rotating frame reaches the set scan speed within the specified time, and the gantry 5 is set to maintain that speed.
Of the X-ray tube is controlled by controlling the rotary frame driving section of the X-ray tube to control the high voltage generating section so that the filament of the X-ray tube reaches the temperature according to the tube current condition in a predetermined time. The bed is controlled to adjust the opening according to the slice thickness condition, and the bed driving unit is controlled to start the bed movement so as to reach the speed according to the helical pitch in a predetermined time.

FIG. 3 shows an operation procedure of the bolus tracking method according to the present embodiment. FIG. 4 shows a time chart of the bolus tracking method. As a preparatory work for the bolus tracking method, measurement of an electrocardiogram is started by the biological phenomenon measuring device 4 (S1). This measurement is continued through the injection of the contrast agent and the prescan until the main scan is completed.

The prescan is performed at a relatively low dose in order to monitor the CT value (reflecting the concentration of the contrast agent) of the blood vessel of interest in the region upstream or downstream of the region of interest (region for examination) of the subject. X-ray is defined as a scan for collecting data by scanning the relevant site upstream or downstream of the region of interest of the subject. A main scan is defined as a scan that scans a region of interest of a subject with higher doses of X-rays than a pre-scan to collect data.

Based on the measured electrocardiogram, an electrocardiograph 2
Heart rate is calculated. The main scan condition is set based on the heart rate, but in reality,
Since the heart rate fluctuates slightly, as shown in FIG. 4, the heart rate is averaged over a predetermined time width such as the immediately preceding 5 seconds, or a median value within the predetermined time width is specified, and the average value or the median value is set. It is preferable to set the main scan conditions based on the above. Here, for convenience of explanation, it is assumed that the main scan condition is set based on the heart rate. The calculated heart rate is displayed on the display 8 via the display control unit 10 together with the electrocardiogram data.

At time T1, the operator operates the input operation unit 9 with reference to the displayed electrocardiogram and heart rate to input the prescan condition, the main scan condition, and the reset condition of the main scan condition ( S2). In addition,
Many of the pre-scan conditions have almost fixed values, so relatively low tube voltage and current to suppress exposure, thin slice width, fast scan speed and immediacy to increase time resolution. A small reconstruction matrix is set to increase. Further prescan position,
The contrast density monitoring region, the transition condition from the pre-scan to the main scan (threshold for contrast density), etc. are manually set.

In addition, many items of the main scan condition,
For example, the tube voltage, the tube current, the slice width, the reconstruction matrix, and the field of view (FOV) are almost determined according to the purpose of the examination, the sex and physique of the subject, and the like. Further, the scan range in which data is collected by the helical scan is set to a range that covers the entire area of the heart, for example. In addition, the patient-specific upper limit of breath-holding time and the required minimum number of segments in the ECG gated reconstruction method are set. "Helical pitch (HP)" and "scan speed" are stored in the data storage unit 6
Is set by the scan condition selection unit 1 to a value according to the heart rate or manually input by the imaging engineer.

The reset condition of the main scan condition is based on the heart rate when the main scan condition is initially set in the preparation stage of the above-mentioned bolus tracking method, just before the main scan, actually at the end of the prescan, or When the heart rate at that time changes, how much the main scan condition will be reset from the initially set main scan condition to the main scan condition corresponding to the heart rate at the end of pre-scan, It represents the rule.

For example, in the table of FIG. 2, when the heart rate at the time of initial setting is "60", the heart rate is included in the section of "60 to 70" on the table, and therefore the helical pitch of that section. HP “0.9” is set. However, when the heart rate measured at the end of the pre-scan deviates from the “60 to 70” category at the time of initial setting, the helical pitch HP should be originally set according to the heart rate. On the other hand,
The heart rate that fluctuates due to the injection of the contrast agent may recover to a steady value over time. That is, even if the heart rate fluctuates greatly at the end of the prescan, it may show a stabilizing tendency after that, and may recover to a steady value during the main scan. Of course, there is a case where the value remains changed and does not recover to the steady value. There are individual differences in the fluctuation of the heart rate. Therefore, the judgment as to whether or not the heart rate has recovered to the steady value during the main scan should be left to the judgment of the doctor or the radiographer.
This judgment is reflected in the resetting condition. The doctor or the radiographer resets the main scan conditions or arbitrarily sets the number of steps in which the section corresponding to the heart rate immediately before the main scan deviates from the heart rate section at the initial setting. It is possible.

After the above initial setting is completed, at time T2, when the start button of the operation unit 9 is pressed, the contrast agent is automatically injected into the subject from the injector device. The pre-scan is started after waiting for the time required for the name of the contrast agent to reach the monitoring position from the injection of the contrast agent (S3). That is, while the X-ray tube and the X-ray detector continuously rotate around the subject at high speed with respect to the positioned slice, X-rays are continuously generated at a low dose, and the data acquisition is periodically repeated. . Then, in parallel with the prescan, the image reconstructing unit immediately reconstructs the image data from the projection data (S2), extracts the CT value in the preset region of interest from the image data, and extracts the CT value. Alternatively, the average value of CT values of a plurality of pixels in the region of interest is compared with the threshold value for main scan transition. During this prescan, the biological phenomenon measuring apparatus 4 continues to measure the heart rate and displays the heart rate as a time graph and numerical values as shown in FIG. 7 (S4).

As shown in FIG. 7, the heart rate referred to when the scan conditions are initially set is displayed together with the current heart rate. Also, the initially set scan speed and helical pitch are displayed numerically. An emergency stop button is displayed together with this information. The heart rate of the subject may change rapidly due to the influence of injection of a contrast agent. In that case, the technician can stop the prescan and the main scan by clicking the emergency stop button.

When the CT value reaches the threshold for main scan shift, or when the technologist manually presses the main scan shift trigger button (T3), the prescan ends (S5). The biological phenomenon monitoring unit 2 determines whether or not the fluctuation of the heart rate measured at the end of the prescan satisfies the reset condition of the main scan condition within a short time until time T4 (S6). ). That is, the absolute value of the difference between the heart rate referred to at the time of initial setting of the scan conditions and the heart rate measured at the end of the prescan is compared with the threshold value of the reset condition.

When the absolute value of the difference does not reach the threshold value of the reset condition, the fluctuation of the heart rate is considered to be relatively small to the extent that the reset condition is not satisfied, and the biological phenomenon monitoring unit 2 , No signal is sent to the scan condition selection unit 1 to urge the resetting of the main scan condition. As a result, as shown in FIG.
Is instructed to send the initially set main scan condition or to start the setup under the initially set main scan condition. As a result, the scan controller 3
Starts the main scan setup at time T4 according to the initial set main scan conditions sent (S7). Then, the setup is completed by the time T5, and the main scan is started at the time T5 (S8). Then, at the time T6 when data collection is completed from the entire scan range, the main scan ends (S
9).

In the determination of S6, when the absolute value of the difference between the heart rate referred to at the time of initial setting of the scan condition and the heart rate measured at the end of the prescan reaches the threshold of the reset condition, It is said that the fluctuation of the heart rate is relatively large as the reset condition is satisfied, and the biological phenomenon monitoring unit 2 scans a signal prompting the reset of the main scan condition together with the heart rate measured at the end of the prescan. Send to the condition selection unit 1. As a result, as shown in FIG. 6, the scan condition selection unit 1 refers to the table of the data storage unit 6 to select the helical pitch and the scan speed corresponding to the heart rate at the end of the prescan, and set the main scan condition. , Reset the helical pitch and scan speed from the initial settings to the selected helical pitch and scan speed (S
10).

When the helical pitch and the scan speed are reset, the display control unit 10 displays, as shown in FIG.
The reset helical pitch and scan speed are displayed together with the initialized helical pitch and scan speed. Depending on whether or not the reset helical pitch and scan speed are displayed,
It is possible to recognize whether or not the helical pitch and the scan speed are reset.

In the case of electrocardiographic gated scanning, the scan condition selecting section 1 determines the "delay time" from the R wave to the specific time phase,
Recalculate by multiplying the heartbeat cycle (reciprocal of heart rate) at the end of the prescan by the ratio of the time width from the R wave to the specific timephase to the heartbeat cycle when the time phase of interest (specific time phase) is set. .

In the above description, the necessity of resetting the main scan condition is determined based on the difference between the heart rate at the time of initial setting of the main scan condition and the heart rate at the end of prescan, and the heart rate at the end of prescan is determined. It has been described that the main scan condition is reset based on the rate. However, it is not limited to the heart rate at the end of the prescan, and is initially based on the heart rate measured at any time during the period from the injection of the contrast agent or the start of the prescan to the end of the prescan. Determine whether it is necessary to reset the set scan conditions,
Further, the main scan condition may be reset based on the heart rate measured at any time within the period. Of course, by determining the necessity of resetting the main scan conditions based on the heart rate at the end of the prescan, that is, the time closest to the start of the main scan, and by resetting the main scan conditions,
Although the main scan condition can be approximated to the optimum main scan condition for the actual heart rate at the time of executing the main scan, the initial scan is based on the heart rate measured at any point of the period. Even if the main scan condition is reset, it is determined whether or not it is necessary to reset the preset scan condition. Rather than running a scan
It is possible to obtain the effect of being able to approximate the optimum value.

The scan condition selection unit 1 is a scan control unit 3
To the main scan condition reset. Thereby, the scan control unit 3 sets up the gantry and the bed 7 according to the reset main scan condition (S11). Then, after the setup is completed, the main scan is executed with X-ray irradiation (S8, S9).

When the heart rate fluctuates as described above, by resetting the main scan conditions, especially the helical pitch and the scan speed, the number of segments required for the ECG gated reconstruction cannot be adjusted, and the scan time It is possible to solve the problem that the projection data collection is not completed over the entire scan range within the upper limit and to improve the time resolution.

Note that, as shown in FIG. 9, in the determination of S6, when the change of the heart rate is relatively large enough to satisfy the resetting condition, the display control unit 10 causes the heart rate and the main scan condition to be changed. May be displayed on the display 8 and a message for confirming whether or not to reset the main scan and a reset continuation / stop button may be finally displayed to confirm whether or not the main scan is reset (S1).
6). When it is instructed not to reset (S17),
In S7, setup of the gantry 5 and the bed 7 is started according to the initially set main scan condition, and the main scan is performed under the condition (S8, S
9). When instructed to reset (S17), S
At 10, the main scan condition is reset, and the gantry 5 and the bed 7 are set up accordingly (S11).

Since the operator finally determines whether or not the resetting is performed at the end of the prescan, the heart rate temporarily fluctuates for an extremely short time near the end of the prescan. Even if such a negligible event occurs, the adverse effect of resetting the main scan condition can be avoided.

Further, when the heart rate fluctuates excessively, that is, when a very peculiar situation in which the corresponding division on the table changes greatly, such as 3 steps or 5 steps, the main scan is stopped. Sometimes it's better.
To cope with such a situation, as shown in FIG.
When the heart rate fluctuates more than a predetermined level such as three levels or five levels on the table, the biological phenomenon monitoring unit 2
When the determination is made, the scanning condition selection unit 1 may display a message for confirming continuation / stop of the main scan and a main scan continuation / stop button on the display 8 together with the greatly changed heart rate. (S12). When the operator (inspection engineer) instructs to continue the main scan (S13), S10.
And S11, the main scan is executed under the main scan conditions reset according to the greatly changed heart rate. On the other hand, when the operator gives an instruction to stop the main scan (S13), the system controller or the interlocking circuit (not shown) urgently stops the shift to the main scan in S14.

Further, as shown in FIG. 11, the main scan condition may be manually reset. As shown in FIG. 12, the display control unit 10 displays the measured heart rate as a time graph and / or a numerical value, and also displays an input field relating to scan conditions of the main scan. Initially set helical pitch and scan speed are displayed in the input field, and a plurality of candidates for helical pitch and a plurality of candidates for scan speed are displayed on a pull-down menu adjacent to each other. At the same time, the scan range, the lower limit of the helical pitch that satisfies the condition that the main scan can complete the predetermined scan range within the predetermined time, and the maximum time of the subject's breath-holding time, that is, the upper limit of the main scan time are Is displayed. The technician refers to the scan range, the lower limit of the helical pitch, and the upper limit of the main scan time together with the heart rate, operates the operation unit 9, and selects the helical pitch and the scan speed from the respective candidates. The helical pitch and scan speed can be reset (S15). When the main scan cannot complete the predetermined scan range within the predetermined time with the selected helical pitch or the selected scan speed, or when the required number of segments is not available, the display control unit 10 determines that, While rejecting the resetting of the scan condition input by the selection, a message prompting the reselection of the helical pitch and the scan speed is displayed on the display 8.

(Modification) The present invention is not limited to the above-described embodiment, and can be variously modified and implemented at the stage of implementation without departing from the scope of the invention.
Further, the above embodiment includes various stages,
Various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, some constituent elements may be deleted from all the constituent elements shown in the embodiment.

[0046]

According to the present invention, in the bolus tracking method by the X-ray computed tomography apparatus, it becomes possible to reset the scan condition of the main scan with respect to the variation of the biological phenomenon of the subject.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a main part of an X-ray computed tomography apparatus according to an embodiment of the present invention.

FIG. 2 is a table (heart rate / helical pitch / scan speed) stored in the data storage unit of FIG.
The figure which shows an example.

FIG. 3 is a flowchart showing a procedure of a bolus tracking method according to the present embodiment.

FIG. 4 is a time chart of the bolus tracking method of FIG.

FIG. 5 is a supplementary explanatory diagram of S6 and S7 of FIG.

6 is a supplementary explanatory diagram of S6, S10, and S11 of FIG.

FIG. 7 is a diagram showing an example of a display screen when the main scan condition is maintained as the initial condition in the present embodiment.

FIG. 8 is a diagram showing an example of a display screen when main scan conditions are reset in the present embodiment.

FIG. 9 is a flowchart showing a procedure of a bolus tracking method according to a first modified example of the present embodiment.

FIG. 10 is a flowchart showing a procedure of a bolus tracking method according to a second modification of the present embodiment.

FIG. 11 is a flowchart showing a procedure of a bolus tracking method according to a third modified example of the present embodiment.

FIG. 12 is a diagram showing an example of a display screen in a third modified example of the present embodiment.

[Explanation of symbols]

1 ... Scan condition selection unit, 2 ... Biological phenomenon monitoring unit, 3 ... Scan control unit, 4 ... Biological phenomenon measuring device (electrocardiograph), 5 ...
Gantry, 6 ... Data storage unit, 7 ... Sleeper, 8 ... Display, 10 ... Display control unit.

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Claims (20)

[Claims] 1. A prescan is performed on a subject injected with a contrast agent using relatively low x-rays, and then a relatively high x-ray is used on the subject. In an X-ray computed tomography apparatus that executes a main scan to collect data, a biological phenomenon of the subject measured during a period from the injection of the contrast agent or the start of the prescan to the end of the prescan is performed. Based on the data, it is determined whether it is necessary to reset the scan condition of the main scan that is initially set based on the biological phenomenon data of the subject measured before the injection of the contrast agent. And a determination unit configured as described above, and when the determination unit determines that the scan condition needs to be reset, the scan condition of the main scan is set to the initial value. From the predetermined scan conditions, to reset the scan conditions corresponding to the data of the biological phenomenon measured within the period from the injection of the contrast agent or the start of the prescan to the end of the prescan. X comprising a configured scan condition setting unit
Line computed tomography equipment. 2. The X according to claim 1, wherein the scan condition setting unit maintains the initially set scan condition when the determination unit determines that it is not necessary to reset the scan condition. Line computed tomography equipment. 3. The X according to claim 1, wherein the scan condition setting unit resets the scan condition based on the biological phenomenon data measured at the end of the prescan.
Line computed tomography equipment. 4. The X according to claim 1, wherein the scan condition setting unit includes a storage unit configured to store a table in which a plurality of scan conditions are associated with a plurality of stages related to the biological phenomenon. Line computed tomography equipment. 5. The determination unit is within a period from the injection of the contrast agent or the start of the prescan to the end of the prescan for the biological phenomenon of the subject measured before the injection of the contrast agent. The X-ray computed tomography apparatus according to claim 1, wherein it is determined whether or not the scan condition needs to be reset based on the degree of variation of the measured biological phenomenon. 6. The X-ray computed tomography apparatus according to claim 1, wherein the biological phenomenon is a heart rate of the subject. 7. The X-ray computed tomography according to claim 1, wherein the determination unit determines whether or not the scan condition needs to be reset based on the biological phenomenon data measured at the end of the prescan. Imaging device. 8. The X according to claim 7, wherein the scan condition setting unit resets the scan condition based on the biological phenomenon data measured at the end of the prescan.
Line computed tomography equipment. 9. The X-ray computed tomography according to claim 6, wherein the determination unit determines whether or not the scan condition needs to be reset based on an average value or a median value of heart rates within a predetermined time width. apparatus. 10. The X-ray computed tomography apparatus according to claim 9, wherein the determination unit resets the scan condition based on an average value or a median value of the heart rates. 11. The X-ray computed tomography apparatus according to claim 1, further comprising a display unit that displays the measured biological phenomenon data in a time graph and / or numerical value in real time. 12. The X-ray computed tomography apparatus according to claim 11, wherein the display unit displays, together with the biological phenomenon data, information indicating whether or not the scan condition is reset. 13. The X-ray computed tomography apparatus according to claim 11, wherein the display unit displays the real-time biological phenomenon data and the biological phenomenon data referred to for the initial setting of the scan conditions. 14. The X-ray computed tomography apparatus according to claim 11, wherein the display unit displays a button for emergency stop of the pre-scan and the main scan together with the biological phenomenon data. 15. The X-ray computed tomography according to claim 1, wherein the scan condition setting unit resets the scan condition on the assumption that the main scan completes a predetermined scan range within a predetermined time. apparatus. 16. A pre-scan is performed on a subject injected with a contrast agent using relatively low x-rays, and thereafter a relatively high x-ray is used on the subject. To collect data and perform a main scan X
In a line computed tomography apparatus, scan conditions for the main scan are set based on biological phenomenon data measured during a period from the injection of the contrast agent or the start of the prescan to the end of the prescan. X-ray computed tomography apparatus including a scan condition setting unit configured as described above. 17. A pre-scan is performed on a subject injected with a contrast agent using relatively low x-rays, and then a relatively high x-ray is used on the subject. To collect data and perform a main scan X
In the line computed tomography apparatus, the measured biological phenomenon data is displayed as a time graph and numerical values, and a display unit configured to display an input field relating to scan conditions of the main scan, and the input field An input unit configured to input a scan condition of the main scan, and the main scan according to a scan condition input within a period between the start of the contrast agent injection or the prescan and the end of the prescan. An X-ray computed tomography apparatus, comprising: a scan condition setting unit configured to set a scan condition of a scan. 18. The scan condition setting unit sets a scan condition of the main scan according to a scan condition input last within a period from the injection of the contrast agent or the start of the prescan to the end of the prescan. The X-ray computed tomography apparatus according to claim 17, which is set. 19. The scan condition setting unit sets the input scan condition when the main scan cannot complete a predetermined scan range within a predetermined time under the input scan condition. 18. The X-ray computed tomography apparatus according to claim 17, which has a function of rejecting the setting. 20. The display unit displays candidates of the scan conditions that enable the main scan to complete a predetermined scan range within a predetermined time.
X-ray computed tomography apparatus described.