Patent Description:
A CT system mainly comprises an X-ray tube, an X-ray detector array, a gantry and a patient bed. The X-ray tube and the X-ray detector array are disposed on the gantry rotating around the patient bed. Usually, the patient bed can move relative to the gantry. The X-ray tube generates a sector X-ray beam, and the X-ray beam passes one slice of an object (for example, a patient) which is being imaged and irradiates on the X-ray detector array. During CT imaging, the included angle between the X-ray beam and the body slice of the patient and the position of the patient bed relative to the gantry change continuously.

The angular position (AP) of the X-ray tube is a very important parameter of the CT system and affects the imaging quality of the CT system. Especially, if the patient needs to use CT for X-ray interventional therapy, it is necessary to precisely position the X-ray tube.

<CIT> discloses radiation therapy systems and methods, wherein these radiation therapy systems comprise two or more independent communication interfaces that provide redundant feedback data for verification of gantry rotation and signal synchronization based on a first position sensor mounted to the rotatable ring, and a second position sensor mounted to the stationary frame. The rotatable ring comprises a plurality of index markers located around the circumference of the ring and detectable by the second position sensor, and the stationary frame comprises a plurality of index markers located around the circumference of the frame and detectable by the first position sensor. The systems further comprise a controller configured to receive and compare the first and second plurality of signals of the two sensors to identify a difference in the first and second plurality of signals and, if the difference exceeds a predetermined threshold, generating a position sensor fault signal.

In order to obtain a precise angular position of the X-ray tube, a high-cost AP measurement system and a motor are adopted for a high-end CT system (for example, Definition system). Although a DC motor which can precisely position a sensor is used to acquire the precise position of the X-ray tube in a high-end CT system, it will take a lot of time and cost because the bearing needs to be assembled by use of DC driving. Usually, the minimum step of the position of the X-ray is <NUM> degrees and the accuracy is <NUM> degrees because of the limited number of check points in a low-end CT system. It is difficult to apply the interventional therapy in a low-end CT system because the low-end CT system cannot guarantee that the X-ray tube stops, with a step of <NUM> degree.

No valid solution has been proposed for the above-mentioned problem.

The present invention is defined by the enclosed claims.

According to one example, a method of controlling the position of the X-ray tube of a CT system may be provided, and the method may comprise: acquiring an AP signal output by an AP sensor of the CT system, an IP signal output by an IP sensor and encoder data output by a motor, determining a homing positioning signal AP<NUM> of the AP signal based on the AP signal and the IP signal, wherein the homing positioning signal AP<NUM> is used to determine the starting point of the period of rotation of the X-ray tube, utilizing the encoder data to calculate the encoder data containing AP signal based on the determined homing positioning signal AP<NUM>, wherein the encoder data containing AP signal is the AP signal calibrated by use of the encoder data, and controlling the position of the X-ray tube based on the encoder data containing AP signal.

Through the above-mentioned exemplary method, the technical problem that the CT system cannot precisely control the position of the X-ray tube in the related technology may be solved and the position of the X-ray tube could precisely be controlled.

In one example, the AP signal is an angular position signal acquired after the AP sensor detects a plurality of check points arranged at even intervals on the outer circumferential surface of the gantry of the CT system, and/or the IP signal is an IP signal acquired after the IP sensor detects a reference check point arranged on the outer circumferential surface of the gantry of the CT system, and the IP signal is used to determine the period of rotation of the X-ray tube, and/or the encoder data is data output by the encoder of the motor and is used to control the speed of rotation of the X-ray tube.

Through the above-mentioned exemplary method a positioning calculation error caused by a belt slip may be eliminated, and thus the positioning accuracy of the X-ray tube may be improved.

In one example, determining a homing positioning signal AP<NUM> of the AP signal based on the AP signal and the IP signal comprises: detecting whether the current IP signal is a high-level signal, and determining the high-level signal of the AP signal in the period in which the current IP signal is continuously a high-level signal to be the homing positioning signal AP<NUM> if the current IP signal is a high-level signal.

Through the above-mentioned exemplary method, the step positioning precision of the X-ray tube may be increased to <NUM> degree, without any new component added.

In one example, utilizing the encoder data to calculate the encoder data containing AP signal based on the determined homing positioning signal AP<NUM> comprises: detecting each high-level signal APi of the AP signal in the period from the homing positioning signal AP<NUM> to when the IP signal is a high-level signal again, respectively calculating the pulse count of the encoder data in the time segment between the homing positioning signal AP<NUM> and each high-level signal APi, and saving the correspondence between the calculated pulse count of the encoder data and the AP signal as an encoder data containing AP signal.

Through the above-mentioned exemplary method, the correspondence between an AP signal and encoder data could more precisely be calculated, and thus making it possible to precisely position the X-ray tube.

In an example, controlling the position of the X-ray tube based on the encoder data containing AP signal comprises: reading the saved encoder data containing AP signal during the rotation of the gantry of the CT system, and utilizing the encoder data containing AP signal to calibrate the position of the X-ray tube so as to control the position of the X-ray tube.

Through the above-mentioned exemplary method, without any sensing device or component added, the position of the X-ray tube may be calibrated by use of the pre-adjustment mode during the subsequent operation, and thus the precision of positioning the X-ray tube may be improved.

According to another example, a device of controlling the position of the X-ray tube of a CT system may be provided, and the device may comprise: an acquisition module, configured to acquire an AP signal output by an AP sensor of the CT system, an IP signal output by an IP sensor and encoder data output by a motor, a determination module, configured to determine a homing positioning signal AP<NUM> of the AP signal based on the AP signal and the IP signal, wherein the homing positioning signal AP<NUM> is used to determine the starting point of the period of rotation of the X-ray tube, a calculation module, configured to utilize the encoder data to calculate the encoder data containing AP signal based on the determined homing positioning signal AP<NUM>, wherein the encoder data containing AP signal is the AP signal calibrated by use of the encoder data, and a control module, configured to control the position of the X-ray tube based on the encoder data containing AP signal.

Through the above-mentioned exemplary structure, the technical problem that the CT system cannot precisely control the position of the X-ray tube in the related technology may be solved and the position of the X-ray tube could precisely be controlled.

In one example, the determination module is further configured to detect whether the current IP signal is a high-level signal, and determine the high-level signal of the AP signal in the period in which the current IP signal is continuously a high-level signal to be the homing positioning signal AP<NUM> if the current IP signal is a high-level signal.

Through the above-mentioned exemplary structure, the step positioning precision of the X-ray tube may be increased to <NUM> degree, without any new component added.

In one example, the calculation module is further configured to detect each high-level signal APi of the AP signal in the period from the homing positioning signal AP<NUM> to when the IP signal is a high-level signal again, respectively calculate the pulse count of the encoder data in the time segment between the homing positioning signal AP<NUM> and each high-level signal APi, and save the correspondence between the calculated pulse count of the encoder data and the AP signal as an encoder data containing AP signal.

Through the above-mentioned exemplary structure, the correspondence between an AP signal and encoder data could more precisely be calculated, and thus making it possible to precisely position the X-ray tube.

In one example, the control module is further configured to read the saved encoder data containing AP signal during the rotation of the gantry of the CT system, and utilize the encoder data containing AP signal to calibrate the position of the X-ray tube so as to control the position of the X-ray tube.

Through the above-mentioned exemplary structure, without any sensing device or component added, the position of the X-ray tube may be calibrated by use of the pre-adjustment mode during the subsequent operation, and thus the precision of positioning the X-ray tube may improved.

According to a further example, a CT system may be provided and the CT system may comprise: a gantry, an AP sensor, an IP sensor, a motor and a motor controller, wherein the AP sensor is configured to detect a plurality of check points arranged at even intervals on the outer circumferential surface of the gantry to acquire an AP signal, the IP sensor is configured to detect a reference check point arranged on the outer circumferential surface of the gantry to acquire an IP signal, the motor is
configured to output encoder data of the motor, and the motor controller is implemented as the above-mentioned device.

Through the above-mentioned exemplary CT system, the technical problem that the CT system cannot precisely control the position of the X-ray tube in the related technology may be solved and the position of the X-ray tube could precisely be controlled.

According to a fourth example, a computer-readable storage medium may be provided, a computer instruction may be stored in the computer-readable storage medium, and when executed, the instruction may enable a processor to execute the above-mentioned method.

The drawings constituting a part of the disclosure are provided to help understand the disclosure, and the exemplary embodiments of the disclosure and the description thereof are used to explain the disclosure, but do not constitute improper restrictions of the disclosure. In the drawings,.

wherein the drawings comprise the following reference numerals:.

To help those skilled in the art to better understand the technical solution of the disclosure, the technical solution in the embodiments of the disclosure will be clearly and completely described below in combination with the drawings in the embodiments of the disclosure.

It should be noted that the terms "comprise" and "have" and their variants are intended to cover non-exclusive inclusions. For example, the process or method comprising a series of steps or the system, product or device comprising a series of modules or units are unnecessarily limited to those clearly-listed steps or modules or units, but may comprise other steps or modules or units which are not clearly listed or are intrinsic to the process, method, product or device.

According to one exemplary embodiment of the disclosure, a CT system is provided. As shown in <FIG>, the CT system <NUM> comprises: an AP sensor <NUM>, an IP sensor <NUM>, an X-ray tube <NUM>, a motor controller <NUM>, a motor <NUM>, a gantry <NUM>, a plurality of check points <NUM>, a reference check point <NUM> and a tension pulley <NUM>.

The gantry <NUM> consists of two parts: a rotary component and a static component, wherein the rotary component can rotate around the central axis of the gantry <NUM> in the X-Y plane of the X, Y and Z axes of the rectangular coordinate system shown in <FIG>, a plurality of check points <NUM> and a reference check point <NUM> are arranged on the outer circumferential surface of the rotary component, an X-ray tube <NUM> and a detector array are oppositely mounted on the inner circumference surface, an AP sensor <NUM> and an IP sensor <NUM> are arranged on the inner circumferential surface of the static component, and the two sensors are separated at a certain distance. A patient bed (not shown) is provided in the gantry <NUM>, a patient can lie on the bed, and the bed can move in the Z-axis direction of the rectangular coordinate system. The rotary component of the gantry <NUM> can continuously rotate around the patient bed.

The X-ray tube <NUM> is disposed on the inner circumferential surface of the rotary component of the gantry <NUM> and emits a sector X-ray beam to the detector array (not shown) which is opposite to the X-ray tube <NUM> and is located on the other side of the inner circumferential surface of the rotary component. The X-ray beam emitted from the X-ray tube <NUM> hits the detector array after passing through a patient and attenuating. The strength of the attenuated radiation beam received at the detector array depends on the patient caused energy attenuation of the X-ray beam. Each detector element of the detector array generates an independent electrical signal, and the electrical signal represents the measured strength of the X-ray beam after the attenuation. After that, the measured strength of each detector of the detector array is collected, and the measured strength is an analog electrical signal. Therefore, it is usually necessary to further send the measured strength to an analog-to-digital converter which digitalizes analog signals for an analog-digital conversion. The image re-constructor (not shown) receives the sampled digital X-ray data from the analog-to-digital converter and performs a high-speed image reconstruction.

The AP sensor <NUM> and the IP sensor <NUM> are adjacently disposed on the inner circumferential surface of the static component of the gantry <NUM>. The plurality of check points <NUM> are arranged at even intervals on the outer circumferential surface of the rotary component. In one exemplary embodiment of the disclosure, the AP sensor <NUM> and the IP sensor <NUM> are proximity switches, the check points <NUM> are metal heads, and the reference check point <NUM> is a metal groove. The proximity switch is a position switch which can be operated without any direct mechanical contact with a moving component. When an object (for example, check points <NUM> and reference check point <NUM>) approaches the sensing surface of the switch to a detectable distance, the switch can act without any mechanical contact or any pressure exerted, and thus the position and stroke of a moving mechanism can accurately be reflected.

During the rotation of the gantry <NUM>, when the distance between a check point <NUM> and the AP sensor <NUM> reaches a preset detectable distance, the AP sensor <NUM> will sense the check point <NUM>, and the switch of the AP sensor <NUM> is in the ON state and outputs a high-level signal as a response signal; when the check point <NUM> departs from the AP sensor <NUM> and the distance away from the AP sensor <NUM> is greater than the preset detectable distance, the AP sensor <NUM> will fail to sense the check point and output a low-level signal. Alike, when the distance between the reference check point <NUM> and the IP sensor <NUM> is less than a preset reference detectable distance, the IP sensor <NUM> outputs a high-level signal, and otherwise outputs a low-level signal all the time.

<FIG> shows the pulse signals generated by the IP sensor <NUM> and the AP sensor <NUM>. When the X-ray tube <NUM> rotates once around the central axis of rotation of the gantry <NUM> along with the gantry <NUM>, the IP sensor <NUM> generates only one pulse signal, namely, one high-level signal, while the AP sensor <NUM> generates a pulse train with a period T and the pulse train contains pulse signals whose number corresponds to the number of check points <NUM>. The angle between every two check points <NUM> is determined by the number of check points <NUM>. Supposing the number of check points <NUM> is n, the angle between every two check points <NUM> is <NUM>/n degrees. From <FIG>, it can be seen that the pulse width of an AP signal is different from that of an IP signal. Because the number of check points <NUM> is different from the number of reference check points <NUM>, the durations of response signals are different.

In addition, since only one reference check point <NUM> is provided, there is only one chance that the distance between the reference check point <NUM> and the IP sensor <NUM> reaches the preset reference detectable distance when the gantry <NUM> rotates once. Thus, the preset reference detectable distance can be used as a flag indicating the gantry <NUM> or the X-ray tube <NUM> rotating once. Therefore, a response signal from the IP sensor <NUM> can be expressed by use of IP. In <FIG>, when the X-ray tube <NUM> rotates clockwise from the <NUM>° position, a response signal output from the AP sensor <NUM> is AP<NUM>, and a response signal output from the IP sensor <NUM> is IP. Since the check points <NUM> are arranged at even intervals on the outer circumferential surface of the rotary component of the gantry <NUM>, the check points <NUM> move toward the AP sensor <NUM> one by one at certain intervals. Therefore, the AP sensor <NUM> will generate n high-level signals in turn, wherein n is the number of the check points <NUM>. Only a part of AP is shown in <FIG>.

The motor <NUM> is configured to control the speed of rotation and direction of rotation of the gantry <NUM> under the control of the motor controller <NUM>, and thus further control the position of the X-ray tube <NUM> disposed on the gantry <NUM>. The motor <NUM> has an encoder. The encoder is usually an incremental encoder and the encoder data output by the encoder is mainly the pulse count per rotation. The pulse count of the encoder data is shown by ED in <FIG>. The tension pulley <NUM> is configured to control the degree of tightness of the belt connecting the gantry <NUM> and the motor <NUM>.

The motor controller <NUM> controls the running of the motor <NUM> to control the position of the X-ray tube <NUM> based on the AP signal acquired from the AP sensor <NUM>, the IP signal acquired from the IP sensor <NUM> and encoder data of the motor <NUM>. The motor controller <NUM> may be a PC, a workstation or a central processing unit (CPU) embedded in the CT system. In other embodiments of the disclosure, the motor controller <NUM> may also be a more advanced processing system, for example, a distributed processing system.

The motor controller <NUM> utilizes the IP signal acquired from the IP sensor <NUM> and the AP signal acquired from the AP sensor <NUM> to calculate the homing positioning signal of the X-ray tube <NUM>, that is to say, to find the AP<NUM> signal. After determining the AP<NUM> signal, the motor controller <NUM> utilizes the encoder data to calculate the pulse count of encoder data between AP signals, starting from AP<NUM>. As shown in <FIG>, the pulse count of encoder data between AP<NUM> and AP<NUM> is <NUM>, the pulse count of encoder data between AP<NUM> and AP<NUM> is <NUM>, and the pulse count of encoder data between AP<NUM> and AP<NUM> is <NUM>. Since the speed of rotation in encoder data is stable and is free from influence of external factors such as a belt slip, it can be considered that no positioning error exists if the pulse count of corresponding encoder data of an AP signal is utilized to position the X-ray tube <NUM>. The calculated pulse counts are fine-tuned according to practical experience (for example, <NUM> is fine-tuned to <NUM>, <NUM> to <NUM> and <NUM> to <NUM>. ) and are saved in a table as table data, as indicated by TD in Table <NUM>. During the positioning of the X-ray tube <NUM>, the motor controller <NUM> utilizes the AP signals recorded in the data table and the corresponding pulse count of encoder data to calibrate the actual position of the X-ray tube <NUM>.

The motor controller <NUM> is further configured to communicate with a storage device or memory (not shown). The storage device is used to store encoder data containing AP signals calculated by the motor controller <NUM>. The storage device includes various computer memories for storing data. The storage device may be an independent component relative to the motor controller <NUM>. However, it should be understood that the storage device may be an integrated part of the motor controller <NUM>. The motor controller <NUM> is further configured to utilize encoder data containing AP signals stored in the storage device to control the running of the motor <NUM> so as to control the position of the X-ray tube <NUM>.

<FIG> shows the closed-loop control of the rotation of the gantry according to one exemplary embodiment of the disclosure. In one exemplary embodiment of the disclosure, when the gantry rotates clockwise, the check points move toward the AP and IP sensors <NUM> one by one at certain intervals, wherein the AP sensor of the AP and IP sensors <NUM> generate n high-level signals in turn, while the IP sensor outputs one high-level signal when the distance between the reference check point and the IP sensor is greater than a preset reference detectable distance, and as the reference check point moves away, the IP sensor outputs low-level signals all the time until the current period ends. The AP and IP sensor <NUM> inputs detected AP signals and IP signals into the motor controller <NUM>. The encoder data in the motor encoder <NUM> is also input into the motor controller <NUM>. The motor controller <NUM> controls the running of the motor <NUM> to further control the positions of the belt/bearing <NUM> and the X-ray tube <NUM> based on the AP signal acquired from the AP sensor, the IP signal acquired from the IP sensor and encoder data acquired from the motor encoder <NUM>. The motor controller <NUM> also controls other operations of the CT scanner <NUM>, for example, steering.

<FIG> shows the structure of the device of controlling the position of the X-ray tube of a CT system according to one exemplary embodiment of the disclosure. As shown in <FIG>, the device <NUM> comprises an acquisition module <NUM>, a determination module <NUM>, a calculation module <NUM> and a control module <NUM>.

In one exemplary embodiment of the disclosure, the acquisition module <NUM> is configured to acquire an AP signal output by an AP sensor of the CT system, an IP signal output by an IP sensor and encoder data output by a motor, the determination module <NUM> is configured to determine a homing positioning signal AP<NUM> of the AP signal based on the AP signal and the IP signal, wherein the homing positioning signal AP<NUM> is used to determine the starting point of the period of rotation of the X-ray tube, the calculation module <NUM> is configured to utilize the encoder data to calculate the encoder data containing AP signal based on the determined homing positioning signal AP<NUM>, wherein the encoder data containing AP signal is the AP signal calibrated by use of the encoder data, and the control module <NUM> is configured to control the position of the X-ray tube based on the encoder data containing AP signal.

In one exemplary embodiment of the disclosure, the determination module <NUM> is further configured to detect whether the current IP signal is a high-level signal, and determine the high-level signal of the AP signal in the period in which the current IP signal is continuously a high-level signal to be the homing positioning signal AP<NUM> if the current IP signal is a high-level signal. The calculation module <NUM> is further configured to detect each high-level signal APi of the AP signal in the period from the homing positioning signal AP<NUM> to when the IP signal is a high-level signal again, respectively calculate the pulse count of the encoder data in the time segment between the homing positioning signal AP<NUM> and each high-level signal APi, and save the correspondence between the calculated pulse count of the encoder data and the AP signal as an encoder data containing AP signal. The control module is further configured to read the saved encoder data containing AP signal during the rotation of the gantry of the CT system, and utilizing the encoder data containing AP signal to calibrate the position of the X-ray tube so as to control the position of the X-ray tube.

Through the above-mentioned structure, without any sensing device or component added, the position of the X-ray tube is calibrated by use of the pre-adjustment mode during the subsequent operation, and thus the precision of positioning the X-ray tube is improved.

<FIG> is a flowchart of the method of controlling the position of the X-ray tube of the CT system according to one exemplary embodiment of the disclosure. As shown in <FIG>, the method comprises the following steps:
Step S502: Acquire an AP signal output by an AP sensor of the CT system, an IP signal output by an IP sensor and encoder data output by a motor.

When the distance between the AP sensor and any check point is less than a preset detectable distance, the AP sensor will sense the check point and generate a high-level signal, and when the distance is greater than the detectable distance, the AP sensor will fail to sense the check point and generate a low-level signal. When the distance between the IP sensor and the reference check point is less than a preset reference detectable distance, the IP sensor will sense the reference check point and generate a high-level signal, and when the distance is greater than the reference detectable distance, the IP sensor will fail to sense the reference check point and generate a low-level signal. The motor outputs encoder data representing the speed of rotation of the gantry. The AP signal, IP signal and encoder data are all transmitted to the motor controller.

Step S504: Determine a homing positioning signal AP<NUM> of the AP signal based on the AP signal and the IP signal, wherein the homing positioning signal AP<NUM> is used to determine the starting point of the period of rotation of the X-ray tube.

One rotation (namely, <NUM> degrees) of the X-ray tube around the central axis of the gantry is a period. When the distance between the reference check point and the IP sensor reaches a preset reference detectable distance, the IP sensor generates a high-level response signal. At this time, the distance between the check point and the AP sensor also reaches the preset detectable distance and the AP sensor generates a high-level signal. The high-level signal generated by the AP sensor is denoted by AP<NUM> and is used as the starting point of a rotation period.

Step S506: Utilize the encoder data to calculate the encoder data containing AP signal based on the determined homing positioning signal AP<NUM>, wherein the encoder data containing AP signal is the AP signal calibrated by use of the encoder data.

After determining the AP<NUM> signal, the motor controller utilizes the encoder data to calculate the pulse count of encoder data between AP signals, starting from AP<NUM>. As shown in <FIG>, the pulse count of encoder data between AP<NUM> and AP<NUM> is <NUM>, the pulse count of encoder data between AP<NUM> and AP<NUM> is <NUM>, and the pulse count of encoder data between AP<NUM> and AP<NUM> is <NUM>.

Step S508: Save encoder data containing AP signals in a table.

The calculated pulse counts are fine-tuned according to practical experience (for example, <NUM> is fine-tuned to <NUM>, <NUM> to <NUM> and <NUM> to <NUM>. ) and are saved in the table as table data.

Steps S502 to S508 are performed in the commissioning stage.

Step S510: Control the position of the X-ray tube based on the encoder data containing AP signal.

During the positioning of the X-ray tube <NUM>, the motor controller <NUM> utilizes the AP signals recorded in the data table and the corresponding pulse count of encoder data to calibrate the actual position of the X-ray tube <NUM>. This step is performed in the formal running stage of the CT scanner.

The exemplary embodiments of the disclosure further provide a storage medium, and a computer program is stored in the storage medium. When executed, the computer program enables a processor to execute the method of controlling the position of the X-ray tube of the CT system in the embodiments of the disclosure. In the above-mentioned embodiment, the above-mentioned storage medium includes, but is not limited to a USB disk, read-only memory (ROM), random access memory (RAM), mobile harddisk, magnetic disk or optical disk and other various media which can store program codes.

It should be understood that the technical content disclosed in the embodiments of the disclosure can be realized in other ways. The above-described embodiments of the device are given only for illustrative purposes. The division of units or modules is only a logical function division, and other division methods may be used in the actual realization. For example, a plurality of units or modules or components may be combined or integrated into another system, or some features may be ignored or may not be executed. In addition, the shown or discussed couplings, or direct couplings or communication connections between them may be indirect couplings or communication connections, electrical or otherwise, through some interfaces, modules or units.

The unit or module described as a separate part may be or may not be physically separated, and the part shown as a unit or module may be or may not be a physical unit or module, that is to say, it may be located at one place or may be distributed to a plurality of network units or modules. Part or all of the units or modules may be selected to realize the solution of the embodiment according to the actual requirements.

In addition, the functional units or modules in each embodiment of the disclosure may be integrated into a processing unit or module, or each unit or module may physically exist separately, or two or more units or modules may be integrated into a unit or module. The above-mentioned integrated unit or module may be realized in the form of hardware or in the form of a software functional unit or module.

Claim 1:
A method of controlling the position of the X-ray tube (<NUM>) of a CT system (<NUM>), comprising:
acquiring an angular position (AP) signal output by an angular position (AP) sensor (<NUM>) arranged on a static component of a gantry (<NUM>) of the CT system (<NUM>), an index pulse (IP) signal output by an index pulse (IP) sensor (<NUM>) arranged on the static component of the gantry (<NUM>) and encoder data output by a motor (<NUM>), wherein the AP signal is acquired after the AP sensor (<NUM>) detects a plurality of check points (<NUM>) arranged at even intervals on a rotary component of the gantry (<NUM>), and the IP signal is acquired after the IP sensor (<NUM>) detects a reference check point (<NUM>) arranged on the rotary component of the gantry (<NUM>),
determining a homing positioning signal AP0 of the AP signal based on the AP signal and the IP signal, wherein the homing positioning signal AP0 is used to determine the starting point of the period of rotation of the X-ray tube (<NUM>), and the IP signal is used to determine the period of rotation of the X-ray tube (<NUM>),
utilizing the encoder data to calculate the encoder data containing AP signal based on the determined homing positioning signal AP0, wherein the encoder data containing AP signal is the AP signal calibrated by use of the encoder data, and
controlling the position of the X-ray tube (<NUM>) based on the encoder data containing AP signal.