JPH07313501A - X ray computed tomographic device - Google Patents

Abstract

PURPOSE:To provide an X ray computed tomographic device which helically- scans a test area precisely and by which a tomographic image of an arbitrary position in the test area can be obtained preisely. CONSTITUTION:An image photographing controlling part 41 gives respective controls of a top board movement, rotation of an X ray duct 14. X ray radiation or the like and an indication of initiating/terminating data collection to a data collection controlling part 42 and the top board position collecting part 44. Then, the data collection controlling part 42 collects data and makes the data stored in a collected data memory 45 and the top board position collecting part 44 makes the top board position at the time of data collection stored in a top board position memory 46, during the time from the beginning to the end of data collection. A preprocessing part 47, a corrected data enumerating part 48, and an image reconstructing part 49 reconstruct a tomographic image of an arbitrary position in the test area based on the collected data stored in each of memories 45, 46 and the top board position. Here, the image photographing controlling part 41 controls the image photographing in the preset test area based on top the board position during the image photographing.

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 for performing a helical scan.

[0002]

2. Description of the Related Art A helical scan by an X-ray CT apparatus of this type is used for a top plate on which an object is mounted at a predetermined speed (for example,
While moving at 10 mm / sec), the X-ray tube and the X-ray detector, which are opposed to each other with the top plate (subject) interposed therebetween, are rotated at a predetermined rotation speed (for example, one rotation (360 °) / second), Data acquisition (spiral scan) is performed at a predetermined number of times (for example, 800 times / revolution) per one rotation of the X-ray tube and the X-ray detector, and a tomographic image is reconstructed based on the collected data.

In order to reconstruct a tomographic image at a certain position, this tomographic image reconstruction is performed by collecting collected data for one rotation before and after the position (in the above, obtained by collecting 800 times). Since it is performed by using the data, it is necessary to obtain the collected data for one rotation before and after the inspection region in order to reconstruct the tomographic images at the first and last positions of the set desired inspection region. Therefore, in this type of helical scan, the top plate is moved so that the scanning can be performed over the imaging area including the additional imaging area for collecting one rotation of data before and after the set inspection area, The X-ray tube and X-ray detector are rotating.

Further, in order to obtain necessary amount of collected data in this image pickup area (inspection area + additional image pickup areas before and after), the conventional apparatus is configured to perform image pickup control based on the number of times of data collection. That is, the imaging is ended when the data collection for the number of times of collection in the imaging region is completed from the start of the imaging. The collected data is sequentially stored in the memory in the order of collection. Then, when a tomographic image at a predetermined position is reconstructed, the tomographic image at that position is reconstructed based on the acquired data for one rotation before and after the acquired data corresponding to the position. There is.

[0005]

However, the conventional example having such a structure has the following problems. That is, the conventional apparatus performs imaging control and image reconstruction of the apparatus on the assumption that the moving speed of the top plate and the rotation speeds of the X-ray tube and the X-ray detector are set to ideal speeds set in advance. However, in reality, due to the mechanical error of the mechanism for moving the top plate and the mechanical error of the mechanism for rotating the X-ray tube and the X-ray detector, the top plate is not always moved or moved at the ideal speed.
The tube and X-ray detector do not rotate.

Therefore, for example, when the rotation speed of the X-ray tube or the X-ray detector is slower than the ideal rotation speed, the imaging time becomes longer than that in the ideal state, so that the X-ray of the object is longer than the ideal time. There is a problem of irradiating. In addition, as a result of the long imaging time, the actual imaging area becomes longer than the ideal imaging area, and there is a problem that the imaging area is displaced.

On the contrary, when the rotation speed of the X-ray tube and the X-ray detector is higher than the ideal rotation speed, the imaging time becomes shorter than that in the ideal state. Although it becomes shorter than the imaging area, in this case, in order to secure a desired imaging area, the conventional apparatus deals with this by collecting data more times than the number of times of data acquisition in ideal imaging. However, since the actual error is not known accurately, the number of times of extra data collection is set to be large, and as a result, the imaging time becomes longer than the ideal time, and the subject is exposed to X-rays for a longer time than the ideal time. There is a problem.

Further, since the collection position of each collection data deviates from that in the ideal case, there is a problem that a tomographic image at a desired position in the examination region cannot be obtained accurately, which hinders diagnosis. Moreover, the displacement of the position is accumulated as the imaging progresses, and as a result, the tomographic image reconstructed at the position after the imaging is largely displaced from the set position.

Further, since the movement of the top plate and the rotation of the X-ray tube and the X-ray detector are performed independently, if an error in the moving speed of the top plate is added, the deviation of the data acquisition position and the imaging The relationship of the displacement of the regions becomes more complicated, and it becomes impossible to make a diagnosis according to a predetermined plan.

The present invention has been made in view of the above circumstances, and it is possible to accurately scan an inspection area and accurately obtain a tomographic image at an arbitrary position within the inspection area. An object of the present invention is to provide an X-ray CT apparatus that can reduce unnecessary X-ray exposure to a subject.

[0011]

The present invention has the following constitution in order to achieve such an object. That is, according to the present invention, the X-axis is arranged so as to face each other while sandwiching the top plate while moving the top plate for mounting the subject over the imaging region obtained by adding the additional imaging regions before and after the set inspection region.
The X-ray detector and the X-ray tube are rotated, and data is collected from the X-ray detector a predetermined number of times per rotation,
X-ray CT for spiral scan (helical scan)
In the apparatus, (a) a top position detecting means for detecting the position of the top during movement of the top, and (b) rotating the X-ray tube and the X-ray detector in advance for each rotation. Collected data storage means for storing the data collected from the X-ray detector a predetermined number of times, and (c) when collecting all collected data stored in the data collection storage means or collecting data at a fixed number of times. A top position collecting means for collecting the top positions by the top position detecting means, and (d) a top position storing means for storing the top positions collected by the top position collecting means, ) X-ray irradiation control from the X-ray tube in the imaging region, control (imaging control) including a data collection instruction are performed, and the top position detected by the top position detecting means in at least the inspection region. Control based on the image And (f) reconstructing a tomographic image at an arbitrary position in the inspection region based on the collected data stored in the collected data storage means and the top position stored in the top position storage means. And image reconstructing means.

[0012]

The operation of the present invention is as follows. The top position detecting means detects the position of the top during movement of the top.
In the additional imaging area in front of the inspection area, the position where the data can be collected a predetermined number of times is determined, and the imaging control means starts imaging from there. Then, when it is known that the top position has reached the start position of the inspection area during imaging, the top position recognizes whether or not the top moves from that position to the end position of the inspection area. Then, when the end position of the inspection area is reached, the imaging is ended when the collection of the data for the number of times of collection of the data collected in the additional imaging area after the inspection area is completed.

That is, the imaging control in the inspection area is
The inspection is performed based on the detected top position (absolute position) regardless of the moving speed of the top and the rotation speed of the X-ray tube and X-ray detector. There is no deviation from the area.

Further, during the image pickup, the data collected is stored in the collected data storage means, and the tabletop position at the time of each data collection is collected by the tabletop position collection means and stored in the tabletop position storage means. Remembered. That is, each collected data has position information at the time of the collection. In addition,
When the top position at the time of collecting the collected data for every fixed number of times is collected, the top position at the time of collecting the collected data during that period is obtained by interpolation calculation. When reconstructing a tomographic image at an arbitrary position within the examination region, the image reconstructing unit reconstructs a tomographic image at that position from a plurality of collected data before and after centering on the data collected at that position. Therefore, it is possible to accurately obtain a tomographic image at an arbitrary position within the examination region.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a diagram showing a schematic configuration of an X-ray CT apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of a processing control unit.

The apparatus of this embodiment has a gantry 1 and a bed 2
It is composed of a setting board 3, a processing control unit 4, and the like. The gantry 1 is provided with an opening 11, and a rotary frame 12 is attached around the opening 11 so as to be continuously rotatable. The rotation of the rotary frame 12 is performed by a motor 13 installed inside the gantry 1.
Done by. The drive control of the motor 13 is performed by the processing control unit 4 described later. Further, the X-ray tube 14 and the X-ray detector 15 are attached to the rotary frame 12 so as to face each other, and the X-ray tube 14 is rotated by rotating the rotary frame 12.
And the X-ray detector 15 are rotated in the opening 11 so as to face each other. Irradiation control of X-rays from the X-ray tube 14 is performed by the processing control unit 4. Further, a data acquisition electronics (DAS) 16 is attached to the X-ray detector 15, and the data detected by the X-ray detector 15 is collected by the acquisition timing signal from the processing control unit 4 (a plurality of channels can be collected at one time. Data is simultaneously collected) and the collected data is given to the processing control unit 4.

The bed 2 is mounted on a pedestal 21 which is installed near the gantry 1 and which can be moved up and down.
2 is slidably mounted so that it can be inserted into and removed from the opening 11 of the gantry 1. The movement of the top plate 22 is performed by a motor 23 provided inside the base 21. The drive control of the motor 23 is performed by the processing control unit 4. Further, a rotary encoder (not shown) is attached to the motor 23 and is configured to output a pulse for each minute rotation angle of the motor 23. An absolute encoder may be attached instead of the rotary encoder to output the minute rotation angle information. Then, the output pulse (angle information) is given to the processing control unit 4.

The setting board 3 is for instructing the setting of the inspection area, the image reconstruction position information, etc., the start of imaging, and the like. The setting information and instructions are given to the processing control unit 4.

Next, the structure of the processing control unit 4 will be described with reference to FIG. The imaging control unit 41 uses the top 22 during the imaging process.
Movement control and rotating frame 12 (X-ray tube 14 and X-ray detector 15
Etc.), the irradiation control of X-rays from the X-ray tube 14, the data collection control unit 42 and the top plate position collection unit 44, which will be described later, are instructed to start and end data collection. That is, the imaging process is performed based on the setting information and instructions given from the setting board 3, the number of times of data collection obtained from the data collection control unit 42 described later, the position of the tabletop 2 detected by the tabletop position calculation unit 43 described later, and the like. The start and stop of the movement of the top plate 22 in the above are controlled by the motor 23 via a motor drive control circuit (not shown), and the X-ray tube 14 and the X-ray detector 1
Control of start and stop of rotation of 5 (hereinafter abbreviated as "rotation of X-ray tube 14 or the like") is performed by the motor 13 via a motor drive control circuit (not shown), and further X-rays from the X-ray tube 14 The start and stop of irradiation are controlled via a high voltage generator (not shown). Further, when the start position of the imaging region (previous additional imaging region) determined by the method described later based on the set inspection region is reached, the data collection control unit 42 and the tabletop position collection unit 44 are started to collect data. When the end position of the imaging region (later additional imaging region) is reached, the data collection control unit 42 and the top position collection unit 44 are instructed to end the data collection. The control of the image pickup control unit 41 will be described in detail in the operation description described later. The image pickup control unit 41 corresponds to the image pickup control means in the present invention.

The data collection control unit 42 includes an image pickup control unit 41.
From the data collection start instruction given by the to the data collection end instruction, based on the rotation angle information of the rotary frame 12,
The acquisition timing signal is output to the DAS 16.

The rotation angle information of the rotary frame 12 is, for example, as shown in FIG. 3, θ (360 ° / 1) on the outer circumference of the rotary frame 12.
A plurality of comb shapes (eg, 80) provided at equal intervals for each number of data collections per rotation (eg, 800 times)
It is composed of (0) light-shielding plate 121, slit 122 and transmission type optical sensor 123. That is, the rotating frame 1
During each rotation of 2, the optical sensor 123 outputs a detection signal corresponding to the number of data collections per rotation, and the data collection control unit 42 outputs a collection timing signal based on the detection signal. The rotation angle information of the rotary frame 12 may be configured to obtain the rotation angle information of the motor 13 by using a rotary encoder, an absolute encoder, or the like, in addition to the configuration of FIG.

The DAS 16 collects the data detected by the X-ray detector 15 when the collection timing signal output according to the predetermined number of data collections per rotation as described above is given, and the collected data is stored. It is stored in the collected data memory 45 as a means. Further, the collection timing signal is also output to the imaging control unit 41 and the top plate position collection unit 44 described later.

The top position calculating unit 43 detects the top position of the top 22 during movement, based on the reference position sensor and a pulse signal from the rotary encoder attached to the motor 23. The reference position sensor is a sensor for detecting that the top plate 22 is located at a reference position (position at the right end of the moving range of the top plate 22 shown by the solid line in FIG. 1A) KP. And is composed of, for example, a limit switch. The top position calculation unit 43 is provided with a counter (not shown), and when the reference position sensor detects that the top 22 is located at the reference position, this counter is cleared.
Further, while the top plate 22 is moving, pulse signals from the rotary encoder are counted by the counter. Since the movement amount of the top plate 22 per one rotation of the motor 23 is known, the position of the top plate 22 with respect to the reference position can be known from the count value of the counter. Even when an absolute encoder is attached to the motor 23 and the rotation angle information is obtained, the position of the top plate 22 with respect to the reference position is known by counting the total rotation angle of the motor 23 from the reference position in the counter. be able to. Further, the encoder attached to the top plate position calculating section 43 and the motor 23 corresponds to the top plate position detecting means in the present invention.

The top position collecting unit 44 corresponds to the top position collecting means of the present invention, and controls the data collection from the data collection start instruction given from the imaging control unit 41 to the data collection end instruction. Each time the collecting timing signal is given from the unit 42, the top position at that time is taken out from the top position calculating unit 43 and stored in the top position memory 46 as a top position storing means. That is, the table position memory 46 stores the table position at the time of data collection.

The preprocessing unit 47 collects the collected data,
Preprocessing for image reconstruction, such as offset processing, reference processing, and calibration processing, is performed, the correction data calculation unit 48 calculates correction data necessary for image reconstruction, and the image reconstruction unit 49 uses the setting board. According to the image reconstruction position information set from 3, the reconstruction of the tomographic image is performed based on the preprocessed collection data, correction data, etc.,
Output (for example, display on a monitor not shown). In addition,
Each processing of each of the units 47 to 49 will be described in detail in the operation description described later.

The collected data memory 45 is composed of an image memory, and the tabletop position memory 46 is a RAM (random
Access memory). The preprocessing unit 47,
The correction data calculation unit 48 and the image reconstruction unit 49
It is composed of a PU (Central Processing Unit). The preprocessing unit 47, the correction data calculation unit 48, and the image reconstruction unit 49
This corresponds to the image reconstruction season in this invention.

Next, the operation at the time of helical scanning by the apparatus of this embodiment will be described. First, in a state where the tabletop 22 is positioned at the reference position KP (at this time, the counter of the tabletop position calculation unit 43 is cleared), the subject is placed on the tabletop 2.
Place on top of 2. Then, the operator sets the inspection region of the subject and the image reconstruction position information from the setting panel 3.

The inspection area to be set is, for example, as shown in FIG.
It may be set by the distance KRL between the start position KRS and the KR of the KR (inspection region) shown in (1) or the start position KRS and the end position KRE of the KR. The start position KRS or / and the end position KRE of the KR are set by the distances LS and LE from the position RP at which the X-ray tube 14 or the like rotates while the top plate 22 is located at the reference position KP. It

Also, with the X-ray tube 14 or the like being rotated by RP, the top plate 22 is moved, and X is moved from the start position KRS being located at RP to the end position KRE being located at RP. When the data is collected from the line detector 15, the data is collected along the spiral locus as shown by the chain line in FIG. As the image reconstruction position information,
For example, as shown in FIG. 6A, the position Ii may be designated in the inspection region KR at each predetermined interval d (for example, every 1 mm), or in FIG. 6B. As shown, arbitrary positions Ia, Ib, I in the inspection region KR
The position of c, Id, Ie, ... May be designated.

By the way, the start position KR in the inspection region KR
In order to perform the image reconstruction of S and the end position KRE, as described in the related art, the additional imaging regions before and after that (the number of times of acquisition in one rotation of the X-ray tube 14 or the like (for example, 800 times, respectively). It is necessary to perform data collection for the imaging area to which the area for collecting (1) minute data) is added. That is, as shown in FIG.
Data collection is started from the start position BRS of R, and the data collection is ended at the end position ARE of the additional imaging area AR later. Therefore, in the imaging control unit 41 (see FIG. 2), in order to control the data collection in this way,
Based on the set inspection area KR, the additional imaging area BR before
Start position BRS and end position A of the subsequent additional imaging area AR
Need to decide RE.

End position ARE of the additional imaging area AR after
(Timing of ending data collection) is, as described later, the end position KR of the inspection region KR during the helical scan.
It can be determined that the data of one rotation of the X-ray tube 14 or the like has been collected after the detection of E.

On the other hand, the start position B of the previous additional imaging area BR
RS (timing of start of data collection) is the inspection area K
When the start position KRS of R is located at RP, the X-ray tube 14
It is determined by assuming the position where data collection for one rotation (or more) will be performed. For example, when the rotation speed of the X-ray tube 14 and the like and the moving speed of the top plate 22 are assumed to operate in an ideal state, the start position BRS of the previous additional imaging region BR
Decide. However, in reality, there is a mechanical error, so X
The rotational speed of the wire tube 14 and the like and the moving speed of the top plate 22 do not always operate in the ideal state. Therefore, when each speed is determined to operate as in the ideal state, the previous additional area BR (the start position BRS thereof) is determined on the assumption that the number of data collections will decrease. This position is shown in FIG.
As shown in, RP with the top plate 22 in the reference position
Determined by the distance from LSS. Therefore, in actual operation,
Data may be collected for one rotation or more such as the X-ray tube 14 in the previous additional region BR, but this is the same in the conventional apparatus.

Next, when the operator gives an instruction to start imaging from the setting panel 3, the imaging control section 41 rotationally drives the motor 13 to rotate the rotary frame 12, while driving the motor 23 to drive the top plate 22. To move. Then, the imaging control unit 41 monitors the top position detected by the top position calculating unit 43, and the start position BRS of the previous additional area BR determined as described above is RP.
When detecting that the top plate 22 has moved from the reference position to the LSS shown in FIG. 4, the imaging control unit 41 starts X-ray irradiation from the X-ray tube 14 and performs data collection control. The data acquisition start is instructed to the unit 42 and the top plate position collection unit 44. As a result, data is collected at each collection timing determined based on the rotation angle information, the collected data is stored in the collected data memory 45, and the position of the table 22 at the time of data collection is collected by the table position collecting unit 44. Then, it is stored in the top position memory 46.

On the other hand, the imaging control unit 41 monitors the top position detected by the top position calculating unit 43 even after the data collection start instruction is given, and the start position KR of the set inspection region KR is monitored.
When S is located at RP, that is, when the top 22 moves from the reference position to LS in FIG. 4, the data acquisition in the detection region KR is controlled based on the top position based on the detection of data. For example, when the distance KRS between the start position KRS and the inspection region KR is set, the end position KRE is obtained from the distance KRS between the start position KRS and the inspection region KR, and the top plate position detected by the top plate position calculation unit 43 is calculated. Monitor and end position K
The top position is monitored until RE is located at RP, and when the start position KRS and the end position KRE are set, the top position detected by the top position calculating unit 43 is monitored and set. The top position is monitored until the end position KRE located at RP.

When it is detected that the end position KRE of the inspection area KR is located at RP, the image pickup control unit 41
The acquisition timing signal given from the data acquisition control unit 42 is counted, and when the count value matches the number of times of acquisition data for one rotation of the X-ray tube 14 or the like, that is, after the inspection region KR, the X-ray tube 14 or the like is detected. When the collection of data for one rotation is completed, the irradiation of X-rays from the X-ray tube 14 is stopped, the driving of the motors 13 and 23 is stopped, and the rotation of the X-ray tube 14 and the like and the movement of the top plate 22 are stopped. In addition, the data collection control unit 4
2 and a data acquisition end instruction are given to the tabletop position collection unit 44 to stop the data collection and the tabletop position collection, and the imaging is completed. As a result, even when the rotation of the X-ray tube 14 or the like or the movement of the top plate 15 does not operate as in the ideal state, one rotation of the X-ray tube 14 or the like (previous addition) is performed before and after the inspection region KR. In the imaging area, it may be more than that). Further, the image pickup in the inspection region KR is controlled based on the position of the top plate, that is, the start position KRS and the end position KRE of the inspection region KR are detected and the image pickup is controlled. The inspection region KR to be imaged does not shift. If the rotation of the X-ray tube 14 or the movement of the top plate 22 is not performed as in the ideal state based on the mechanical error, the number of data actually collected in the inspection region KR operates as in the ideal state. Although it is different from the number of data in the case of performing, as described in the related art, the image reconstruction need only have the collected data for one rotation before and after, and the required number of data before and after the examination region KR is collected. Therefore, it does not hinder the image reconstruction at any position in the inspection region KR.

Further, the preceding additional image pickup area BR is set to an extra eye in consideration of a mechanical error, but this is the same in the conventional apparatus. However, the inspection area KR is not displaced from the set inspection area, and X is not detected in the additional imaging area AR after that.
Since only the data for one rotation of the radiation tube 14 and the like is collected, the subject is not exposed to X-rays more than necessary. In general, considering that the additional imaging region BR before the inspection region KR is shorter than the inspection region KR, the amount of unnecessary X-ray exposure to the subject due to extra eyes in anticipation of the previous additional imaging region BR is determined. Is a slight one.
In any case, useless X-ray irradiation to the subject can be reduced as compared with the conventional apparatus.

Next, the procedure of image reconstruction of the set position based on the collected data and the top position will be described. First, the set image reconstruction position (referred to as Ip) is retrieved from the top position memory 46. At this time, if the top position located at Ip is not in the top position memory 46 (that position I
If there is no data collected at p), then its position Ip
Search for the top plate position near. Then, the preprocessing unit 47
Performs preprocessing (offset processing, reference processing, calibration processing, etc.) on the collected data for one rotation before and after the searched top position, and supplies it to the image reconstruction unit 49. It should be noted that this pre-processing is a processing that has been conventionally performed, and thus its detailed description is omitted. Further, in parallel with this, the correction data calculation unit 48 calculates the correction data at the time of image reconstruction and supplies it to the image reconstruction unit 49.

In the calculation of the image reconstruction, as shown in FIG. 7, if the interval Iw between the positions where the collected data for one rotation before and after the image reconstruction position Ip is collected is different, the calculation is performed. The coefficients used are different. Note that FIG.
7A shows data collection when the rotation speed of the X-ray tube 14 or the like is Rs and the moving speed of the top plate 22 is S1, and FIG.
Indicates data collection when the rotation speed of the X-ray tube 14 or the like is Rs and the moving speed of the top plate 22 is S2 (where S1 <S2). If the rotational speed of the X-ray tube 14 and the like and the moving speed of the top plate 22 are in an ideal state, the interval Iw is always constant, so the coefficient used in the calculation of the image reconstruction should correspond to the Iw. Although it is sufficient to make one piece, in reality, there is a mechanical error, each of these speeds is different from that in the ideal state, and Iw is different from that in the ideal state. Therefore, the interval between the positions at which the collected data for one rotation before and after the searched top position Ip is centered is set as the top position memory 4
Obtained from the top position stored in 6. For example, as shown in FIG. 8, if the number of times of data collection for one rotation is 800 times and the searched top position is the 1000th time, the heavens collected at the (1000 + 800) th time are shown. Iw based on the plate position (Te) and the top position (Ts) collected at the (1000-800) th time.
Is calculated from (Te−Ts), and the coefficient and the like used for the calculation of the image reconstruction in the case of this Iw are calculated. Data correction unit 48
Then, the coefficients and the like thus obtained are given to the image reconstruction unit 49 as correction data.

The image reconstructing section 49 reconstructs a tomographic image based on the given pre-processed data and correction data and displays it on a monitor or the like. Note that this reconfiguration calculation has been performed conventionally, and thus detailed description thereof is omitted here. If the set image reconstruction position does not exist in the top position memory 46, the tomographic image of the set position is determined according to the amount of deviation between the set image reconstruction position and the searched nearby position. Is reconstructed.

The tomographic images are reconstructed at the respective set image reconstruction positions by the procedure as described above.

As described above, since the top plate position at the time of collecting the data is collected in each collected data, the tomographic image at the set image reconstruction position can be accurately obtained.

Further, in this embodiment, since the preprocessing, the calculation of the correction data and the reconstruction of the tomographic image are performed by the respective separate CPUs, the respective processings can be executed in parallel, and the processings can be performed. The time can be shortened.

Note that the image reconstruction may be performed sequentially in parallel with the collection (imaging) of the data and the top plate position, or may be performed collectively after the completion of the imaging. Good.

Further, in the above-mentioned operation, the image reconstruction position information is set before the start of the image pickup, but after the image pickup is finished, an arbitrary image reconstruction position is set if necessary, and You may make it reconstruct the tomographic image of a position.

Further, in the above-mentioned embodiment, the tabletop position at the time of collecting all the data collected in the imaging area is configured to be stored and stored. However, of all the data collected in the imaging area, , The top position at the time of collecting data every predetermined number of times (for example, 10 times) is collected and stored, and the top position at the time of collecting data is not stored. It may be configured to be obtained by interpolation (for example, linear interpolation) and used in the image reconstruction processing. With this configuration, the top position memory 46 can be downsized.

[0046]

As is apparent from the above description, according to the present invention, since the imaging control in the inspection area is performed based on the position of the top plate, the moving speed of the top plate, the rotation of the X-ray tube, and the rotation of the X-ray detector. It is possible to take an image of the inspection area as set regardless of the speed. Further, this can reduce unnecessary X-ray irradiation of the subject.

Further, since the position of the tabletop at the time of data acquisition is stored, it is possible to specify the data acquired at an arbitrary position within the inspection area at the time of image reconstruction. Therefore, a tomographic image at an arbitrary position can be accurately obtained, and accurate diagnosis can be performed.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an X-ray CT apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a processing control unit.

FIG. 3 is a diagram showing a mechanism for detecting rotation angle information of a rotary frame.

FIG. 4 is a diagram for explaining a positional relationship between an imaging region and an X-ray tube or the like.

FIG. 5 is a diagram showing a scan trajectory.

FIG. 6 is a diagram for explaining a method of setting an image reconstruction position.

FIG. 7 is a diagram for explaining correction data at the time of image reconstruction.

FIG. 8 is a diagram for explaining correction data at the time of image reconstruction.

[Explanation of symbols]

 13, 23 ... Motor 14 ... X-ray tube 15 ... X-ray detector 22 ... Top plate 41 ... Imaging control unit 42 ... Data collection control unit 43 ... Top plate position calculation unit 44 ... Top plate position collection unit 45 ... Collected data memory 46 ... Top plate position memory 47 ... Pre-processing unit 48 ... Correction data calculation unit 49 ... Image reconstruction unit KR ... Inspection region BR ... Previous additional imaging region AR ... Later additional imaging region M ... Subject

Claims (1)

[Claims] 1. An X-ray tube which is arranged to face a sandwiched top plate while moving a top plate for mounting a subject over an imaging region obtained by adding an additional imaging region before and after the set inspection region. And an X-ray detector are rotated, and data is collected from the X-ray detector a predetermined number of times per rotation to perform a spiral scan (helical scan). ) A top position detecting means for detecting the position of the top during movement of the top, and (b) rotating the X-ray tube and the X-ray detector by a predetermined number of times per rotation, Collection data storage means for storing data collected from the X-ray detector; and (c) the top plate position at the time of collection of all collection data stored in the data collection storage means or collection data at regular intervals. Top plate position collected by the top plate position detecting means Position collecting means, (d) a top position storage means for storing the top positions collected by the top position collecting means, and (e) X-ray irradiation control from the X-ray tube in the imaging region, data Control including collection instruction (imaging control)
And (f) the collected data stored in the collected data storage means and the image pickup control means for performing image pickup control based on the tabletop position detected by the tabletop position detection means in at least the inspection area. An X-ray CT apparatus comprising: an image reconstructing unit that reconstructs a tomographic image at an arbitrary position within the examination region based on the table position stored in the table position storage unit.