JPH0626546B2 - X-ray CT system - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention belongs to the technical field of CT apparatus, and in particular, obtains a CT image of a region to be examined, such as the heart, which is periodically moving. A CT device capable of

[Technical Background of the Invention and Problems Thereof] A conventional CT apparatus is, for example, a heartbeat-linked X-ray CT apparatus, in which the X-ray of the heart as a site to be examined that performs periodic body movements
The line CT image was obtained as follows. That is, US
As shown in P4182311, while intermittently rotating the X-ray tube around the subject around the body axis of the subject, for example, the patient, irradiate X-rays at predetermined rotation angles, for example, every 0.6 °. In addition to obtaining a large number of projection data, the electrocardiographic data of the patient is collected at the same time. After the completion of multiple scans, out of all the obtained projection data, select the projection data in the same phase of each heartbeat, rearrange the selected projection data as projection data at a predetermined rotation angle, and For non-rotational angles, projection data of adjacent rotation angles are supplemented by interpolation, and the resulting 360 / rotational angle projection data can be reconstructed to obtain a CT image of the heart. There is.

However, if the scan is performed without controlling the relationship between the heartbeat phase and the rotation phase, in the worst case, the two will be completely coincident, and no matter how many times the scan is performed, the data of a certain heartbeat phase will show a certain rotation angle. Therefore, there is a problem that heartbeat phase data at different angles cannot be obtained.

By the way, even if the control is performed such that the heartbeat phase and the rotation phase do not initially match with each other by some method, there is a problem that the heartbeat phase and the rotation phase match again when the heartbeat changes.

[Object of the Invention] The present invention has been made in view of the above circumstances, and a first object thereof is to provide an X-ray CT apparatus capable of performing scanning by differentiating a heartbeat phase and a rotation phase. The purpose of 2 is to control so that when the heartbeat phase and the rotation phase coincide with each other during scanning, the phases of the both can be made different X
A line CT apparatus is provided.

[Summary of the Invention] A first aspect of the invention for achieving the above object is to continuously rotate an X-ray tube around a subject a plurality of times while rotating a body motion phase of the subject and the X-ray tube. In an X-ray CT apparatus that collects a large number of scan data in association with a phase, the measured rotational speed of the X-ray tube is adjusted so as to be a rotational phase different from the measured physical movement phase. According to a second aspect of the present invention, a control means for controlling the X-ray tube is continuously rotated a plurality of times around the subject while the body motion phase of the subject and the X-ray tube are controlled. In an X-ray CT apparatus that collects a large number of scan data in association with a rotation phase of a X-ray tube, the X-ray tube is referred to a measured body movement phase so that the rotation phase is different from the body movement phase. Controls the rotation speed of the body and changes the body movement phase during data acquisition At this time, a control means for controlling the rotation speed of the X-ray tube is provided so as not to coincide with the change phase.

[Examples of the Invention] Hereinafter, the present invention will be described specifically with reference to Examples.

The X-ray CT apparatus according to the present invention is configured as shown in FIG. In the figure, reference numeral 1 denotes an arithmetic control unit, which, when the operator operates the console 15, starts the operation of each unit of the device described later and outputs a control signal 2 for controlling the operation, and the projection data 8 And various data such as the electrocardiogram signal 11 are input and these are temporally associated with each other, and the associated data is output as scan data to an auxiliary storage device 13 described later, and further required from the auxiliary storage device 13. It is configured to read out scan data and rearrange it to reconstruct an X-ray CT image. Reference numeral 3 denotes a gantry, which is equipped with an X-ray source 5 and which receives the control signal 2 to set the X-ray source 5 at a constant rotation angle at a constant rotation angle, for example, at every 0.6 °. The rotation angle (phase) signal 12 is supplied to the arithmetic and control unit 1 while being configured to rotate around. 4 is an X-ray generation controller, which receives the control signal 2
A high voltage is applied to the X-ray source 5 at fixed time intervals in synchronization with the rotation of the gantry 3 so that the X-ray source 5 irradiates the subject 7 with X-rays. The X-ray source 5 irradiates the subject 7 with X-rays in a fan shape. 6 is a detector,
The X-ray source 5 is arranged so as to face the X-ray source 5 and rotates together with the X-ray source 5, or is fixedly arranged on a concentric circle outside the circular locus around which the X-ray source 5 rotates. It is configured to detect all transmitted X-rays transmitted through the subject 7 and output the projection data 8 to the arithmetic and control unit 1. Reference numeral 9 denotes an electrocardiogram monitor, which collects an electrocardiogram signal 11 by a pair of electrodes 10 attached to the subject 7, and detects a R wave from the electrocardiogram signal 11 to transmit a heartbeat phase signal 11a to perform arithmetic control. It is configured to output to the unit 1. Reference numeral 14 denotes a display device, which displays an X-ray CT image reconstructed by the arithmetic and control unit 1 for example in C
It can be displayed on the RT monitor.
Reference numeral 13 denotes an auxiliary storage device, which is a memory for temporarily storing scan data obtained by the arithmetic and control unit 1 in a temporally associated manner.

Here, the function of the arithmetic control unit 1 will be described. This device first receives the heartbeat phase signal 11a from the electrocardiogram monitor 9 in response to a start signal from the console 15 to obtain the heartbeat phase, and refers to this heartbeat phase to rotate the X-ray source 5 and the detector 6. After the (scan) phase is calculated, a signal for operating the X-ray generation controller 4 is output by the rotating layer based on this calculation result. The calculation reference at this time is that the measured heartbeat phase and the rotational phase at the time of scanning do not match (be different). or,
The arithmetic control unit 1 always refers to the heartbeat phase signal 11a from the electrocardiogram monitor 9 and the rotation phase based on the rotation angle signal 12 of the rotating system even during the scan, and the heartbeat phase changes during the scan, If there is a possibility that the rotation phase coincides with the rotation phase, a rotation phase that does not match the changed heartbeat phase is calculated, and the calculation result signal is output to the X-ray generation control unit 4, so that the rotation phase is changed. It has become.

Next, the operation of the device will be described with reference to the time chart of FIG.

First, when the operator operates the console 15 and gives a scan start command, the electrocardiogram monitor 9 operates, the electrocardiogram 11 is measured via the electrodes 10 attached to the subject 7, and the heartbeat phase is measured from the electrocardiogram monitor 9. The signal 11a is output. The arithmetic control unit 1 uses the heartbeat phase signal 11a to output the cycle T thereof.
₁ is obtained and the rotation period T _{3 of the} rotating system is referred to as T ₁
The rotation control unit signal 2 that satisfies the condition of ≠ T ₃ is supplied to the rotating system and is also supplied to the X-ray generation control unit 4 (time t ₀ ~
between t _1). This scan is initiated rotation and X-ray exposure to a predetermined angle is performed by (after time t _1). In this way, the scanning is performed a predetermined number of times under the condition that the heartbeat period T ₁ and the rotation period T ₃ are different (time t ₂ to.
t _4).

Then, consider a case where the heartbeat phase of the subject changes due to some cause during scanning, and becomes, for example, a cycle T ₂ which is shorter than the initial cycle T ₁ . In such a case, if the rotation phase period T ₃ is maintained, there arises a problem that it coincides with the heartbeat period T ₂ after the next time t ₅ . However, the arithmetic control unit 1 always receives the heartbeat phase signal 11a from the electrocardiogram monitor 9 and the rotation phase signal 12a.
Since both of them are monitored by inputting, the rotation control signal 2 such that the rotation cycle becomes the cycle T ₄ which does not match with reference to this cycle T ₂ when the heartbeat phase cycle changes as described above. Will be calculated and output. Therefore, after the time t _5, the heartbeat phase period T ₂ and the rotation period T ₄ do not match. After that, even if the heartbeat cycle changes again during the scan,
The rotation control as described above is automatically performed.

In this embodiment, the heartbeat and the rotation phase are made different so that the heartbeat phase and the rotation phase do not match for each scan. However, the present invention is not limited to this, and the timings of the both are shifted regardless of the cycle. It goes without saying that the heartbeat phase and the rotation phase may be controlled to be different for each scan.

When the collection of the scan data by the predetermined number of scans is completed in this way, the arithmetic control unit 1 causes the auxiliary storage device 1 to operate.
Of all the scan data stored in 3, the projection data is extracted for each phase obtained by equally dividing the heartbeat cycle into, for example, 12 and rearrangement is performed as follows. That is, for the projection data of the specific phase, for example, the second phase in the heartbeat cycle, the projection data corresponding in time to the second phase of the heartbeat cycle is extracted from the first scan data, and this is set as the first scan second phase data. Similarly, the second phase data is extracted from all the scan data such as the second scan second phase data from the second scan data and the third scan second phase data from the third scan data. Rearrange according to the rotation angle of. If the second phase data for the specific rotation angle is not obtained even by the rearrangement, the second rotation angle before and after the rotation angle is obtained.
By supplementing with the interpolation data obtained with the phase data, all projection data of the second phase for all rotation angles with respect to the heart are obtained. Phase data for other phases can be obtained in the same manner as above. An image is reconstructed for each phase data of all the obtained rotation angles to obtain an X-ray CT image for each phase of the heartbeat cycle, which is displayed on the CRT monitor of the display device.

The X-ray CT image obtained as described in detail above is an extremely preferable image because it is reconstructed based on projection data at different angles with respect to the in-body phase of the subject 7.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment and can be appropriately modified and implemented within the scope of the gist of the present invention.

〔The invention's effect〕

In the present invention, first, the measured body movement phase is referred to, and the scan is performed at a rotation phase different from that phase. Therefore, it is possible to obtain scan data of different angles at a certain body movement phase for each scan. Even if the body movement phase and the rotation phase are referenced during the next scan, the two do not match.Therefore, even if the body movement phase changes, the scan data is always collected at different angles. It is possible to provide an X-ray CT apparatus capable of performing the above.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a time chart for explaining the operation. 1 ... Arithmetic control unit, 3 ... Stand, 4 ... X-ray generation control unit, 5 ... X-ray source, 6 ... Detector, 7 ... Subject, 9 ... Electrocardiogram monitor, 10 ... Electrode , 13 ... auxiliary storage device, 14 ... display device, 15 ... console.

Claims (2)

[Claims] 1. A large number of scan data are collected by correlating a body motion phase of the subject and a rotation phase of the X-ray tube while continuously rotating the X-ray tube around the subject multiple times. X
The X-ray CT apparatus is provided with a control means for controlling the rotational speed of the X-ray tube so that the measured rotational phase of the X-ray tube is a rotational phase different from the measured physical phase of the body. CT device. 2. A large number of scan data are collected by correlating the body motion phase of the subject and the rotation phase of the X-ray tube while continuously rotating the X-ray tube around the subject multiple times. X
In the linear CT apparatus, the rotational speed of the X-ray tube is controlled so that the rotational phase is different from the measured body movement phase by referring to the measured body movement phase, and the body movement phase is changed during data acquisition. Sometimes, an X-ray CT apparatus is provided with a control means for controlling the rotation speed of the X-ray tube so as not to match the changed phase.