JP2624927B2 - X-ray CT system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray CT apparatus,
In particular, the present invention relates to an X-ray CT apparatus that performs a dynamic scan.

[0002]

2. Description of the Related Art Conventionally, in an X-ray CT apparatus, an imaging method called a dynamic scan has been actively performed.

[0003] The dynamic scan is a method of continuously performing scanning for a predetermined time according to the speed of the contrast agent flowing in the subject after administering the contrast agent.

Generally, the sensitivity of X-ray projection data obtained by dynamic scanning is highest immediately after a contrast agent is injected into a subject, and thereafter decreases with time. Therefore, the scan is usually performed so-called "early phase" immediately after the injection of the contrast agent.

Recently, however, diagnostically useful and characteristic images can be obtained not only at an early stage immediately after the administration of a contrast agent but also at a relatively “late phase” after a predetermined time has elapsed. know.

[0006] This is because there is a characteristic in how the contrast agent is stained depending on the organ, the kind of the disease, and the like. For example, when a large amount of the contrast agent is administered for diagnosis of hepatocellular carcinoma, a useful image can be obtained at a late time. ("CT diagnosis of hepatocellular carcinoma by administration of a large amount of a contrast agent: especially about phase", Japanese Radiological Society Academic Conference, 1992, 3.R52.
07, S239).

Scanning at such a late time is
It is performed in the following procedure.

First, an early scan is performed.

After a lapse of the early period, a period required to monitor the timing of entering the late period is referred to as a transition period in the period until the next late period is entered (this is referred to as a transition period in this specification). The scanning operation is continued under the X-ray irradiation condition of, and the operator monitors the timing of entering a late time while watching the X-ray image displayed on the monitor.

[0010] Whether the operator has entered the late period is determined by the operator based on whether or not the density of the image displayed on the monitor has increased.

Next, if it is confirmed on the monitor that the time has entered late, a predetermined scan is performed at the late time.

[0012]

However, it is not easy to predict in advance the timing of entering a later period because the length of the transition period varies greatly from individual to individual.

[0013] In addition, since it is up to the operator who monitors the monitor to judge whether it is late or not, the burden on the operator increases.

Further, since the density resolution of the operator's eyes varies from person to person, the judgment by the operator has a limit in terms of accuracy.

For these reasons, it has been difficult to reliably capture an image at a later time, although an image at a later time is known to be effective for diagnosis.

In addition, since it takes a certain period of time from the injection of the contrast medium to the staining of a predetermined organ, there is a limit in terms of precision in empirically capturing the rising timing at an early stage.

The present invention has been made in view of the above circumstances, and has as its object to provide an X-ray CT apparatus capable of automatically starting or stopping a scan in accordance with how a contrast agent is stained. And

[0018]

In order to achieve the above-mentioned object, an X-ray CT apparatus according to the present invention, as described in claims 1 to 3, uses a contrast agent injected into the subject to determine whether or not the subject is desired. X-ray C to be used for diagnosis by observing a change in the contrast agent concentration value at a site to be increased at an early stage immediately after injection and at a later stage after a lapse of a predetermined time after this early stage.
In the T device, RO is set at a desired portion in a predetermined image.
An ROI setting unit for setting I, and a threshold setting unit for setting a threshold value for a CT value necessary to capture at least one of the beginning and end of the later period of the concentration value increasing period due to the injected contrast agent. , The threshold set by the threshold setting unit and the R set by the ROI setting unit.
A comparison unit that compares the contrast agent concentration value that changes within the OI with time and outputs a comparison result indicating at least one of the beginning and the end, and the comparison unit that outputs the comparison result from the later period according to the comparison result from the comparison unit A scan command unit for commanding at least one of start and stop of scanning, and controls scanning of the subject by X-rays based on a command from the scan command unit.

Preferably, the scan parameters of the scan are at least one of an X-ray tube voltage, an X-ray tube current, and a sampling interval, and the early time, the late time, and the early and late times. A different amount of the scan parameter was set at each of the periods between. For example, the scan is a helical scan.

In order to achieve the above object, the present invention provides
An X-ray CT apparatus for performing a diagnosis by observing a change in a contrast agent concentration value at a desired portion of the subject by a contrast agent injected into the subject, as described in claim 4 to 8, In the apparatus, an ROI setting unit that sets an ROI at a desired site in a predetermined image, and a threshold setting unit that sets a threshold value related to a CT value for detecting a density value that changes according to an injected contrast agent A comparing unit that compares the threshold value set by the threshold setting unit with the contrast agent concentration value that changes within the ROI set by the ROI setting unit over time, and outputs the comparison result And a scan command unit for commanding at least one of a scan start and a stop in accordance with a comparison result from the comparison unit, and scans the subject with X-rays based on a command from the scan command unit. It is obtained so as to control the emissions.

For example, the threshold value is a CT value capable of detecting the rising edge of a change in the contrast agent concentration and instructing the start of the scan. Further, for example, the threshold value is a CT value that can detect a falling edge of a change in contrast agent concentration and instruct the stop of the scan. Further, for example, the threshold value is a CT value capable of instructing the start of the scan by detecting a rising edge of a change in the contrast agent concentration, and the scan command unit sets the CT value after the contrast agent concentration exceeds the threshold value. It is means for instructing the start of the scan after a lapse of a predetermined time. For example, the scan is a helical scan.

[0022]

The X-ray CT according to the present invention according to any one of claims 1 to 8.
According to the apparatus, a diagnosis is made by injecting a contrast medium into a subject.
First, an ROI is set at a desired site in a predetermined X-ray image,
Next, a threshold value for the CT value for detecting a change in the contrast agent density value is set. The CT value in the ROI is compared with the threshold value over time, and the start and / or stop of a predetermined scan is commanded according to the comparison result.

In particular, in the first to third aspects of the present invention,
The threshold value is set in order to capture a late time that appears after a predetermined time has elapsed after administration of the contrast agent. Therefore CT
The start and / or end of the later period is accurately determined according to the determination that the value is above or below the threshold value, and the start and / or stop of the scan for the later period is reliably controlled. .

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the X-ray CT apparatus according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the X-ray CT apparatus of this embodiment.

The X-ray CT apparatus according to the present embodiment includes a gantry 1 equipped with an X-ray tube and an X-ray detector, a data collection unit 2 for collecting X-ray projection data from the X-ray detector, and a collected X-ray. An image reconstruction unit 3 for reconstructing an image using projection data, an image memory 4 for storing a reconstructed image, a keyboard 5 for inputting various operation parameters, a monitor 6 for displaying a reconstructed image, and the like. And a control unit 7 for controlling them.

The X-ray CT apparatus according to the present embodiment also includes a scan plan setting unit 11 for setting scan parameters, an ROI setting unit 12 for setting an ROI in a predetermined X-ray image,
A threshold value setting unit 13 for setting a threshold value for a CT value in the ROI, a CT value comparing unit 14 for calculating a CT value in the ROI and comparing the calculated CT value with a threshold over time; A scan instruction unit 15 for instructing start or stop of a predetermined scan according to the comparison result.

The threshold value is set in order to capture a late time appearing after a predetermined time has elapsed after the administration of the contrast agent.
When the T value exceeds this threshold value, it is determined that a later time has been entered, and scanning for the later time is started.

The X-ray CT apparatus according to the present embodiment also includes an ROI information storage file 16 for storing the set positions and dimensions of the ROI, and a scan parameter storage file 17 for storing the set scan parameters.

FIG. 2 is a flowchart showing a procedure for performing a scan at a later time using the X-ray CT apparatus of the present embodiment.

First, scan parameters for an early period, a transition period, and a late period are set using the acquired scanograms.

The scan parameters are set by the scan plan setting unit 11, and the tube voltage, tube current, sampling interval, and the like of the X-ray tube are set for each of the early, transition, and late periods.

Here, the set scan parameters are stored in the scan parameter storage file 17.

The scan parameters at the transition time are set in consideration of a sampling period required to monitor whether the operation has entered a later time.

Next, the ROI setting section 12 sets an ROI on a predetermined image.

A predetermined image can be obtained by performing a single scan, and the ROI is set using a mouse, for example, at a site having a contrast effect.

FIG. 3 shows the ROI 21 set to a predetermined image displayed on the monitor 6.

Here, the set position and size of the ROI are stored in the ROI information storage file 16.

Referring to FIG. 2 again, threshold value detecting section 13 sets a threshold value for detecting a rising time point which determines the beginning of a later time with respect to the CT value in the set ROI.

FIG. 4 is a graph showing R changing with the injection of the contrast agent.
The change of the CT value in the OI is shown with time on the horizontal axis and CT value on the vertical axis, and the contrast agent injection speed is also shown.

As can be seen in FIG. 4, the threshold is denoted by α.

Referring again to FIG. 2, after setting the threshold value,
The scan command section 15 sends a control signal to the control section 7 requesting the start of scanning at an early stage.

Upon receiving the control signal, the control section 7 reads out the scan parameters for the early period from the scan parameter storage file 17, and controls these sections so that the gantry 1, the data collection section 2 and the like operate according to the scan parameters. Then, a dynamic scan at an early stage is performed.

After the end of the scan at an early stage, the scan command section 15 sends a control signal requesting the start of the scan at the transition time to the control section 7.

The control unit 7 reads out the scan parameters for the transition time from the storage file 17, controls each unit according to the scan parameters, and performs a monitor scan.

During this monitor scan, the CT value comparing section 14 reads out the position and size of the ROI from the ROI information storage file 16 and calculates the CT value in the ROI.
The calculated CT value is compared with a threshold value to determine whether or not the calculated CT value has exceeded the threshold value.

When the CT value comparing section 14 determines that the CT value has exceeded the threshold value, it sends a predetermined signal to the scan command section 15, and the scan command section 15 controls the control section 7 to start the scan at a later time. Request to.

The control section 7 reads out the scan parameters for the late time from the storage file 17, controls each section according to the scan parameters, and performs the dynamic scan at the late time.

As described above, the X-ray CT of this embodiment
The apparatus sets an ROI on a predetermined image as a monitoring area, and by monitoring a change in the CT value within the ROI, can automatically capture the timing of transition from the transition time to a later time.

Therefore, there is no variation due to the difference between operators, and it is possible to capture the transition to the later period with high accuracy.

Further, since there is no need for the operator to monitor the change in the CT value, the burden on the operator of the CT inspection is reduced.

Further, since the change in the CT value can be monitored with high accuracy, the need for frequent sampling is reduced, and the exposure dose is reduced.

In the above-described embodiment, the dynamic scan has been described. However, the X-ray CT apparatus of the present invention is not limited to such a dynamic scan, and may be applied to, for example, a helical scan.

In the above-described embodiment, the monitoring of the threshold value in the ROI is used to detect the rising timing of the late timing. However, the present invention is not limited to this. May be used.

In the above embodiment, the CT in the ROI is
Although the scan is started when the value exceeds a predetermined threshold value, the scan may be started when a predetermined time has elapsed after the predetermined threshold value is exceeded.

In the above embodiment, the CT in the ROI is
When the value exceeds a predetermined threshold value α, the scan is started assuming that the beginning of the later period is detected. However, as shown in FIG. 4, another value β that determines the end of the later period is used as the threshold value. May be set, and when the CT value in the ROI falls below a predetermined threshold value β, the end of the later period is detected and the scan is stopped.

[0057]

As described above, the X-ray CT apparatus according to the present invention is an apparatus for injecting a contrast agent into a subject and scanning the same, and setting an ROI at a desired site in a predetermined X-ray image. A threshold value for a CT value for capturing a change in the concentration of a contrast agent is set, a CT value in the ROI is calculated, and the calculated CT value is compared with the threshold value over time. By instructing the start or stop of a predetermined scan in accordance with the instruction, the start and / or stop of the scan can be automatically and stably performed in accordance with the manner of dyeing of the contrast agent. The obtained X-ray tomographic image can be reliably obtained, and the operational burden on the operator can be significantly reduced. In particular, it is possible to automatically and accurately start and / or stop scanning at a time when the concentration of the contrast agent changes late.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing a procedure for automatically performing a scan at a later time by using the X-ray CT apparatus of the embodiment.

FIG. 3 is a diagram showing an ROI set on an image on a monitor.

FIG. 4 is a graph showing a change in a CT value in an ROI.

[Description of Signs] 7 control unit 11 scan plan setting unit 12 ROI setting unit 13 threshold setting unit 14 CT value comparison unit 15 scan command unit 16 ROI information storage file 17 scan parameter storage file

Claims (8)

(57) [Claims] 1. A contrast agent injected into a subject increases a contrast agent concentration value at a desired portion of the subject at an early stage immediately after injection and at a later stage after a lapse of a predetermined time after the early stage. X for diagnosis by observing changes
In a line CT apparatus, an ROI is set at a desired site in a predetermined image.
An I setting unit, a threshold setting unit for setting a threshold value related to a CT value necessary to capture at least one of the beginning and the end of the later period of the concentration value increase time due to the injected contrast agent, A threshold value set by the value setting unit and a contrast agent concentration value that changes within the ROI set by the ROI setting unit with time, and a comparison result indicating at least one of the start and end periods And a scan instruction unit for instructing at least one of start and stop of the scan at the later time in accordance with the comparison result from the comparison unit, and based on an instruction from the scan instruction unit, An X-ray CT apparatus, which controls scanning of an object by X-rays. 2. The scan parameter of the scan is X
Setting at least one of a tube voltage, an X-ray tube current, and a sampling interval, wherein the scan parameter has a different amount at each of the early period, the late period, and the period between the early period and the late period. The X-ray CT apparatus according to claim 1. 3. The X-ray CT apparatus according to claim 1, wherein the scan is a helical scan. 4. An X-ray CT apparatus for performing a diagnosis by observing a change in a contrast agent concentration value at a desired portion of the subject by a contrast agent injected into the subject, wherein the X-ray CT apparatus includes: ROI to set ROI to the part
An I setting unit, a threshold value setting unit for setting a threshold value for a CT value for detecting a density value changed by an injected contrast agent, a threshold value set by the threshold value setting unit, A comparison unit that compares the contrast agent density value that changes within the ROI set in the ROI setting unit with time and outputs the comparison result, and starts and stops scanning according to the comparison result from the comparison unit An X-ray CT apparatus, comprising: a scan command unit for commanding at least one of the following, and controlling scanning of the subject by X-rays based on a command from the scan command unit. 5. The CT which is capable of detecting a rising edge of a change in contrast agent concentration and instructing the start of the scan.
The X-ray CT apparatus according to claim 4, which is a value. 6. The CT which is capable of instructing a stop of the scan by detecting a falling edge of a change in a contrast agent concentration.
The X-ray CT apparatus according to claim 4, which is a value. 7. The CT which is capable of instructing the start of the scan by detecting a rising edge of a change in contrast agent concentration.
5. The X-ray CT apparatus according to claim 4, wherein the scan command section is a means for instructing the start of the scan after a predetermined time has elapsed since the contrast agent concentration exceeded the threshold value. 8. The X-ray CT apparatus according to claim 4, wherein the scan is a helical scan.