JP6797620B2 - X-ray CT device - Google Patents

Description

Embodiments of the present invention relate to an X-ray CT apparatus.

The X-ray CT apparatus collects data based on X-rays transmitted through the subject by a detector, reconstructs the collected data, and acquires CT image data. At this time, the X-ray CT apparatus optimizes the detector settings based on the thickness of the subject and the tube current value of the X-ray tube, and carries out the main scan. For example, the X-ray CT apparatus acquires the thickness of the subject from the positioning image (scano image) collected before the main scan, and the detector collects the thickness based on the thickness of the subject and the tube current value. The detector settings are optimized by adjusting the gain that determines the amplification factor when outputting data.

Japanese Unexamined Patent Publication No. 2014-108173 JP-A-2002-306468 Japanese Unexamined Patent Publication No. 2009-131563

An object to be solved by the present invention is to provide an X-ray CT apparatus capable of optimizing the setting of the detector even when the positioning image is not collected.

The X-ray CT apparatus of the embodiment includes a detector, a reconstruction unit, an estimation unit, and an adjustment unit. The detector detects the X-rays irradiated from the X-ray tube and transmitted through the subject, and collects the data derived from the detected X-rays. The reconstructing unit reconstructs the data collected by the detector to acquire CT image data. The estimation unit estimates the thickness of the subject. The adjusting unit adjusts the setting of the detector based on the thickness estimated by the estimating unit and the tube current value of the X-ray tube.

FIG. 1 is a block diagram showing an example of the configuration of the X-ray CT apparatus according to the first embodiment. FIG. 2A is a flowchart for explaining a series of flow of photography according to the first embodiment. FIG. 2B is a diagram for explaining adjustment of the setting of the detector according to the first embodiment. FIG. 3A is a flowchart for explaining a series of shooting flows according to the first embodiment. FIG. 3B is a diagram for explaining adjustment of the setting of the detector according to the first embodiment. FIG. 4A is a flowchart for explaining a series of flow of photography according to the first embodiment. FIG. 4B is a diagram for explaining adjustment of the setting of the detector according to the first embodiment. FIG. 5A is a diagram for explaining the thickness of the subject according to the first embodiment. FIG. 5B is a diagram for explaining the thickness of the subject according to the first embodiment. FIG. 6 is a flowchart for explaining a series of processes of the X-ray CT apparatus according to the first embodiment. FIG. 7 is a diagram for explaining adjustment of the setting of the detector according to the second embodiment. FIG. 8 is a flowchart for explaining a series of processes of the X-ray CT apparatus according to the second embodiment.

Hereinafter, the X-ray CT apparatus according to the embodiment will be described with reference to the drawings.

(First Embodiment)
First, an example of the configuration of the X-ray CT apparatus 100 according to the first embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing an example of the configuration of the X-ray CT apparatus 100 according to the first embodiment. As shown in FIG. 1, the X-ray CT apparatus 100 includes a gantry 110, a sleeper apparatus 120, and a console 130.

The gantry 110 is a device that irradiates the subject P (subject) with X-rays, detects the X-rays transmitted through the subject P, and outputs the X-rays to the console 130. The X-ray irradiation control circuit 111 and the X-ray generator It has a device 112, a detector 113, a rotating frame 114, and a gantry drive circuit 115. Further, the detector 113 includes an X-ray detector 113a and a data acquisition circuit (DAS: Data Acquisition System) 113b.

The rotating frame 114 supports the X-ray generator 112 and the X-ray detector 113a so as to face each other with the subject P in between, and rotates at high speed in a circular orbit centered on the subject P by the gantry drive circuit 115. It is an annular frame. The X-ray irradiation control circuit 111 controls a high voltage generator (not shown) to supply a high voltage to the X-ray tube 112a. Here, the X-ray irradiation control circuit 111 adjusts the X-ray dose to be irradiated to the subject P by adjusting the tube current value supplied to the X-ray tube 112a under the control of the scan control circuit 133. .. Further, the X-ray irradiation control circuit 111 switches the wedge 112b. Further, the X-ray irradiation control circuit 111 adjusts the X-ray irradiation range (fan angle and cone angle) by adjusting the opening degree of the collimator 112c.

The X-ray generator 112 is a device that generates X-rays and irradiates the subject P with the generated X-rays, and has an X-ray tube 112a, a wedge 112b, and a collimator 112c. The X-ray tube 112a is a vacuum tube that generates X-rays by using a high voltage supplied from a high voltage generator (not shown) under the control of the X-ray irradiation control circuit 111, and is a vacuum tube that generates X-rays with the rotation of the rotating frame 114. The subject P is irradiated with an X-ray beam. The wedge 112b is an X-ray filter for adjusting the X-ray dose of X-rays exposed from the X-ray tube 112a under the control of the X-ray irradiation control circuit 111. Specifically, the wedge 112b transmits the X-rays exposed from the X-ray tube 112a so that the X-rays emitted from the X-ray tube 112a to the subject P have a predetermined distribution. It is a filter that attenuates. The wedge 112b is also called a wedge filter or a bow-tie filter.

The collimator 112c is a slit for narrowing down the X-ray irradiation range in which the X-ray dose is adjusted by the wedge 112b under the control of the X-ray irradiation control circuit 111. The gantry drive circuit 115 rotates the rotating frame 114 to rotate the X-ray generator 112 and the X-ray detector 113a on a circular orbit centered on the subject P. The X-ray detector 113a is a two-dimensional array type detector (surface detector) that detects X-rays that have passed through the subject P, and a sequence of detection elements in which X-ray detection elements for a plurality of channels are arranged. A plurality of rows of the gantry 110 are arranged along the rotation center axis direction (Z-axis direction shown in FIG. 1) of the rotation frame 114 in the non-tilted state.

The data collection circuit 113b is a DAS and collects CT projection data from the X-ray detection data detected by the X-ray detector 113a. For example, the data acquisition circuit 113b performs amplification processing with a predetermined gain, A / D conversion processing, sensitivity correction processing between channels, and the like on the X-ray intensity distribution data detected by the X-ray detector 113a. CT projection data is generated, and the generated CT projection data is transmitted to the console 130. For example, when X-rays are continuously exposed from the X-ray tube 112a during the rotation of the rotating frame 114, the data acquisition circuit 113b collects the CT projection data group for the entire circumference (360 degrees). Further, the data collection circuit 113b associates the tube position with each of the collected CT projection data and transmits the data to the console 130. The tube position is information indicating the projection direction of the CT projection data.

The sleeper device 120 is a device on which the subject P is placed, and has a sleeper drive device 121 and a sleeper 122. The sleeper drive device 121 moves the sleeper 122 in the Z-axis direction to move the subject P into the rotating frame 114. The sleeper 122 is a plate (top plate) on which the subject P is placed. In the present embodiment, a case where the relative position change between the gantry 110 and the sleeper 122 is realized by controlling the position of the sleeper 122 will be described, but the embodiment is not limited to this. For example, when the gantry 110 is self-propelled, the relative position of the gantry 110 and the sleeper 122 can be changed by controlling the traveling of the gantry 110.

The console 130 is a device that accepts an operation of the X-ray CT apparatus 100 by an operator and reconstructs CT image data (volume data) using the CT projection data collected by the gantry 110. As shown in FIG. 1, the console 130 includes an input circuit 131, a display 132, a scan control circuit 133, a preprocessing circuit 134, a storage circuit 135, and a processing circuit 136.

The input circuit 131 has a mouse, keyboard, trackball, switch, button, joystick, etc. used by the operator of the X-ray CT device 100 to input various instructions and various settings, and information on the instructions and settings received from the operator. Is transferred to the processing circuit 136. The display 132 is a monitor referred to by the operator, and under the control of the processing circuit 136, a part of the CT image data is displayed to the operator, and various instructions and various instructions are given from the operator via the input circuit 131. A GUI (Graphical User Interface) for accepting settings etc. is displayed.

The scan control circuit 133 controls the operations of the X-ray irradiation control circuit 111, the gantry drive circuit 115, the data acquisition circuit 113b, and the sleeper drive device 121 under the control of the processing circuit 136, thereby performing CT projection data on the gantry 110. Control the collection process of. The preprocessing circuit 134 performs logarithmic conversion processing and correction processing such as offset correction, sensitivity correction, and beam hardening correction on the CT projection data generated by the data acquisition circuit 113b, and corrects the CT projection. Data is generated and stored in the storage circuit 135.

The storage circuit 135 stores standard body shape information used by the processing circuit 136 when estimating the thickness of the subject P and information related to the subject. The standard body shape information and the information related to the subject will be described later. Further, the storage circuit 135 stores the corrected CT projection data generated by the preprocessing circuit 134 and the CT image data reconstructed by the processing circuit 136.

The processing circuit 136 executes the reconstruction function 136a, the estimation function 136b, the adjustment function 136c, and the control function 136d. In the embodiment shown in FIG. 1, each processing function performed by the component reconstruction function 136a, estimation function 136b, adjustment function 136c, and control function 136d is recorded in the storage circuit 135 in the form of a program that can be executed by a computer. ing. The processing circuit 136 is a processor that realizes a function corresponding to each program by reading a program from the storage circuit 135 and executing the program. In other words, the processing circuit 136 in the state where each program is read out has each function shown in the processing circuit 136 of FIG. Although it has been described in FIG. 1 that the processing functions performed by the reconstruction function 136a, the estimation function 136b, the adjustment function 136c, and the control function 136d are realized by a single processing circuit, a plurality of independent processors are used. The processing circuit may be configured by combining the above, and the function may be realized by each processor executing the program.

The word "processor" used in the above description means, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an integrated circuit for a specific application (ASIC), or a programmable logic device (for example, a programmable logic device). It means a circuit such as a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPLD). The processor realizes the function by reading and executing the program stored in the storage circuit 135. Instead of storing the program in the storage circuit 135, the program may be directly incorporated in the circuit of the processor. In this case, the processor realizes the function by reading and executing the program embedded in the circuit. It should be noted that each processor of the present embodiment is not limited to the case where each processor is configured as a single circuit, and a plurality of independent circuits may be combined to form one processor to realize its function. Good. Further, the plurality of components in FIG. 1 may be integrated into one processor to realize the function.

The reconstruction function 136a in the first embodiment is an example of the reconstruction unit within the scope of claims. Further, the estimation function 136b in the first embodiment is an example of an estimation unit within the scope of claims. Further, the adjustment function 136c in the first embodiment is an example of an adjustment unit within the scope of claims.

The processing circuit 136 controls the entire processing by the X-ray CT apparatus 100. That is, the processing circuit 136 controls the entire operation of the X-ray CT apparatus 100 by controlling the operations of the gantry 110, the sleeper apparatus 120, and the console 130. For example, the processing circuit 136 controls the scan control circuit 133 to control the CT scan performed on the gantry 110. Further, for example, the processing circuit 136 reconstructs the CT image data by using the CT projection data collected by the CT scan.

Here, as the reconstruction method, there are various methods, and examples thereof include a back projection process. Further, as the back projection process, for example, a back projection process by the FBP (Filtered Back Projection) method can be mentioned. Alternatively, the processing circuit 136 can reconstruct the CT image data by using the successive approximation method. Then, the processing circuit 136 stores the reconstructed CT image data in the storage circuit 135.

Further, the processing circuit 136 performs various image processing on the reconstructed CT image data to generate a CT image for display, and stores it in the storage circuit 135. Further, the processing circuit 136 controls the display 132 to display the CT image for display stored in the storage circuit 135. Further, the processing circuit 136 estimates the thickness of the subject P prior to the CT scan, and adjusts the setting of the detector 113 based on the estimated thickness and the tube current value of the X-ray tube 112a. The adjustment of the setting of the detector 113 by the processing circuit 136 will be described later.

The overall configuration of the X-ray CT apparatus 100 according to the first embodiment has been described above. Under such a configuration, the X-ray CT apparatus 100 according to the first embodiment optimizes the setting of the detector 113 even when the positioning image is not collected.

Here, first, a series of flow of photographing the subject P by the X-ray CT apparatus 100 when the positioning image is collected will be described with reference to FIG. 2A. FIG. 2A is a flowchart for explaining a series of flow of photography according to the first embodiment.

As shown in FIG. 2A, after the subject P is aligned on the bed 122, the X-ray CT apparatus 100 performs a CT scan on the subject P and collects a positioning image. Next, as shown in FIG. 2A, the X-ray CT apparatus 100 calculates the thickness of the subject P based on the collected positioning image, and from the thickness of the subject P, the exposure mA (X-ray tube 112a). (Tube current value) is calculated. For example, the X-ray CT apparatus 100 calculates the exposure mA of X-rays to be exposed to the scan range from the thickness of the subject P by AEC (Auto Exposure Control).

Next, the X-ray CT apparatus 100 optimizes the hardware (detector 113) setting based on the exposure mA and the thickness of the subject P, as shown in FIG. 2A. For example, the X-ray CT apparatus 100 adjusts the gain when the detector 113 amplifies and collects data derived from X-rays as a setting of the detector 113. Then, the X-ray CT apparatus 100 executes the imaging of the subject P by using the detector 113 whose settings are optimized.

The thickness of the subject P in FIG. 2A is the thickness of the portion of the subject P to be imaged. In other words, the thickness of the subject P is the thickness of the portion through which the X-rays irradiated from the X-ray tube 112a pass. For example, when the thickness of the subject P is large, the X-rays irradiated from the X-ray tube 112a and transmitted through the subject P will reach the detector 113 after being greatly attenuated. On the other hand, when the thickness of the subject P is small, the X-rays reach the detector 113 without being attenuated so much. That is, even when X-ray irradiation is performed at a constant tube current value, the intensity of X-rays detected by the detector 113 changes depending on the thickness of the subject P. Therefore, the X-ray CT apparatus 100 estimates the intensity of the X-rays detected by the detector 113 based on the thickness of the subject P, and optimizes the setting of the detector 113.

Here, the optimization of the setting of the detector 113 will be described in detail with reference to FIG. 2B. FIG. 2B is a diagram for explaining adjustment of the setting of the detector 113 according to the first embodiment. The graph shown in FIG. 2B is an X-ray detector that emits X-rays emitted from the X-ray tube 112a with a tube current value calculated based on the positioning image and transmitted through the subject P having a thickness calculated based on the positioning image. The X-ray CT apparatus 100 predicts the distribution of the count value when each X-ray detection element of 113a detects it and the data acquisition circuit 113b amplifies and collects it with a predetermined gain.

The horizontal axis of FIG. 2B indicates the number of channels (number of channels), and corresponds to each X-ray detection element included in the X-ray detector 113a. That is, the horizontal axis indicates the position coordinates on the X-ray detector 113a. The numbers on the vertical axis in FIG. 2B indicate count values. Here, the count value is a value after the data acquisition circuit 113b amplifies the data with a predetermined gain. For example, the maximum value (Peak) of the graph shown in FIG. 2B changes depending on the gain setting in the data acquisition circuit 113b.

In FIG. 2B, the position of the subject P is conceptually displayed. That is, FIG. 2B shows that the X-ray detection element at the position corresponding to the subject P among the positions shown on the horizontal axis detects the X-rays that have passed through the subject P. The solid line portion of the graph of FIG. 2B shows the predicted value of the count value. Further, the broken line portion of the graph of FIG. 2B supplementarily shows the predicted value of the count value when it is assumed that the subject P is not in the field of view (FOV).

Note that FIG. 2B predicts the distribution of count values on the assumption that the subject P is located at the center of the FOV at the time of scanning. Here, the X-ray CT apparatus 100 calculates the distribution of the thickness of the subject P in the FOV based on the position of the subject P in the FOV and the thickness of the subject P calculated based on the positioning image. be able to. Then, the X-ray CT apparatus 100 is a detector when the X-ray is irradiated with the tube current value calculated based on the positioning image as shown in FIG. 2B based on the distribution of the thickness of the subject P in the FOV. The distribution of the count values collected by 113 can be calculated.

In FIG. 2B, a part of the broken line portion of the graph is in the overflow (OverFlow; OF) region. Here, the overflow means that the count value exceeds the range (dynamic range) that the data collection circuit 113b can collect. In FIG. 2B, the dynamic range is in the range of “0” to “50,000”, and when the count value exceeds “50,000”, an overflow occurs. When an overflow occurs, the magnitude of the count value outside the dynamic range cannot be evaluated. Therefore, the reconstructed CT image data is expressed in, for example, one color (white, etc.) in the overflow range. Will be done.

The broken line portion of the graph is the count value when the subject P is not in the FOV, and when the subject P is included in the FOV, the X-rays are attenuated according to the thickness of the subject P. Here, the X-ray CT apparatus 100 determines the distribution of the thickness of the subject P in the FOV based on the thickness of the subject P acquired based on the positioning image and the position of the subject P (the center of the FOV). It is possible to calculate and predict the attenuation of X-rays based on the calculated thickness distribution, and calculate that the count value at the time of scanning becomes the shape of the solid line portion of the graph of FIG. 2B.

As shown in the solid line portion of the graph of FIG. 2B, the X-ray CT apparatus 100 calculates the count value at the time of scanning based on the distribution of the thickness of the subject P, and the maximum value (Peak) does not enter the overflow region. As described above, the gain of the detector 113 is adjusted. Further, as shown in FIG. 2B, the X-ray CT apparatus 100 adjusts the gain so that the maximum value of the count value is close to the upper limit value “50,000” of the dynamic range.

Here, the X-ray CT apparatus 100 reconstructs the CT image data by taking a picture under a condition that the count value becomes larger while preventing the maximum value of the count value from entering the overflow region. Images due to circuit noise can be reduced. The circuit noise is noise generated in various data processing, and the smaller the count value, the larger the influence of the circuit noise. That is, the X-ray CT apparatus 100 minimizes the influence of circuit noise and optimizes the setting of the detector 113 while avoiding overflow.

As described above, the X-ray CT apparatus 100 calculates the distribution of the thickness of the subject P in the FOV based on the thickness of the subject P and the position of the subject P at the time of photographing the subject P. The maximum value of the count value in is estimated, and the gain is adjusted to reduce the influence of circuit noise while preventing the estimated maximum value from entering the overflow region. Then, the X-ray CT apparatus 100 executes the imaging of the subject P by using the detector 113 whose settings are optimized.

However, in the clinical setting, the positioning image may not be collected and the thickness of the subject P may be unknown. For example, in photographing the head and limbs, the positioning image may not be collected because the individual difference of the part is small and the subject size is also small. Here, a series of steps of photographing the subject P by the X-ray CT apparatus 100 when the positioning image is not collected will be described with reference to FIG. 3A. FIG. 3A is a flowchart for explaining a series of shooting flows according to the first embodiment.

As shown in FIG. 3A, first, the subject P is aligned on the bed 122. Here, even when the positioning image is not collected, the exposure mA (tube current value of the X-ray tube 112a) is input by the operator who visually observes the subject P based on the approximate size of the subject P. be able to. Then, the X-ray CT apparatus 100 uses the detector 113 to take an image of the subject P.

Here, the adjustment of the setting of the detector 113 when the positioning image is not collected and the information on the thickness of the subject P cannot be used will be described with reference to FIG. 3B. FIG. 3B is a diagram for explaining adjustment of the setting of the detector 113 according to the first embodiment. Here, in the graph shown in FIG. 3B, each X-ray detection element of the X-ray detector 113a detects the X-rays emitted from the X-ray tube 112a with the input tube current value, and the data acquisition circuit 113b determines. The distribution of the count value when amplified by the gain of is shown. Further, the horizontal axis of FIG. 3B indicates the number of channels, and corresponds to each X-ray detection element included in the X-ray detector 113a. That is, the horizontal axis indicates the position coordinates on the X-ray detector 113a. The vertical axis in FIG. 3B shows the count value after the data acquisition circuit 113b amplifies with a predetermined gain.

In the case shown in FIG. 3B, since the information on the thickness of the subject P cannot be used in the X-ray CT apparatus 100, it is assumed that the FOV does not include the subject P and the entire FOV is air (all air). Then, the distribution of the count value is predicted and the gain is adjusted. That is, the X-ray CT apparatus 100 adjusts the gain so that the maximum value does not enter the overflow region in the graph of FIG. 3B in which the center of the X-ray detector 113a is the maximum value (Peek) of the count value. For example, as shown in FIG. 3B, when a part of the graph is in the overflow region, the X-ray CT apparatus 100 adjusts a predetermined gain, lowers the data amplification factor, and sets the maximum value of the count value. Change the setting of the detector 113 so that is not entered in the overflow area.

However, in an actual scan, the FOV contains the subject P, and the X-rays are attenuated according to the thickness of the subject P. That is, when the information on the thickness of the subject P is not available, the X-ray CT apparatus 100 adjusts the gain without considering the attenuation of the X-ray, so that the gain is adjusted based on the thickness of the subject P. Compared with the case, the data amplification factor is set lower. By setting the data amplification factor low, overflow can be avoided, but artifacts due to circuit noise may occur in the reconstructed CT image data. In other words, the X-ray CT apparatus 100 cannot optimize the setting of the detector 113 when the information on the thickness of the subject P is not available.

Therefore, the X-ray CT apparatus 100 according to the first embodiment estimates the thickness of the subject P when the positioning image is not collected, and uses the estimated thickness to optimize the setting of the detector 113. To be. First, a series of steps of photographing the subject P by the X-ray CT apparatus 100 when the positioning image is not collected and the thickness of the subject P is estimated will be described with reference to FIG. 4A. FIG. 4A is a flowchart for explaining a series of flow of photography according to the first embodiment. In the following, a case where the positioning image is not collected will be described.

As shown in FIG. 4A, after the subject P is aligned on the bed 122, the X-ray CT apparatus 100 estimates the thickness of the subject P and exposes the mA (tube current value of the X-ray tube 112a). ) Is accepted from the operator. Next, the X-ray CT apparatus 100 optimizes the hardware (detector 113) setting based on the exposure mA and the thickness of the subject P, as shown in FIG. 4A. Then, the X-ray CT apparatus 100 executes the imaging of the subject P by using the detector 113 whose settings are optimized.

As described above, the X-ray CT apparatus 100 optimizes the setting of the detector 113 by estimating the thickness of the subject P even when the positioning image is not collected. That is, even when the positioning image is not collected, the X-ray CT apparatus 100 can obtain the positioning image by using the estimated thickness of the subject P instead of the thickness of the subject P calculated based on the positioning image. The settings of the detector 113 can be adjusted as if they were collected. Hereinafter, the processing performed by the X-ray CT apparatus 100 in order to estimate the thickness of the subject P and optimize the setting of the detector 113 will be described in detail.

First, the estimation function 136b estimates the thickness of the subject P. Specifically, the estimation function 136b estimates the thickness of the subject P based on the standard body shape information. Here, the standard body shape information is information held in advance by the X-ray CT apparatus 100 or information obtained by processing the information held in advance, and standard dimensions for each part are set. It is a thing. For example, standard body shape information is a three-dimensional patient model.

For example, the estimation function 136b acquires a patient model that matches the body shape of the subject P from the model data stored in the storage circuit 135. Here, the model data will be described. The model data is an image actually taken by a CT device of a human body having a standard physique according to a plurality of combinations of parameters related to physique such as age, adult / child, male / female, weight, and height. It is generated in advance and stored in the storage circuit 135.

That is, the storage circuit 135 stores a plurality of model data according to the combination of the above-mentioned parameters. Then, the estimation function 136b compares the above-mentioned parameters with the information related to the subject P, and reads out model data having a physique similar to that of the subject P from the storage circuit 135 as a patient model. The above-mentioned parameters are merely examples, and in addition to the above-mentioned examples, various parameters such as BMI (Body Mass Index), chest circumference, and sitting height can be used.

In addition, the estimation function 136b acquires information on the imaging portion. For example, the estimation function 136b receives an input for setting the imaging region from the operator via the input circuit 131. Next, the estimation function 136b estimates the thickness of the subject P using the read patient model. For example, when the imaging site of the subject P is the head, the estimation function 136b acquires a value of the head thickness from the patient model and estimates the acquired value as the thickness of the subject P.

The estimation function 136b may be a case where the patient model is corrected and the thickness of the subject P is estimated using the corrected patient model. For example, the estimation function 136b corrects the patient model according to the difference between the parameters in the read patient model and the information related to the subject P. As an example, the estimation function 136b enlarges or reduces the patient model so that the BMI of the read patient model and the BMI of the subject P match. Then, the estimation function 136b can acquire a value of the thickness of the imaging site from the patient model after enlargement or reduction, and can estimate the acquired value as the thickness of the subject P.

The estimation function 136b can acquire information related to the subject P through various systems such as RIS (Radiology Information System) and HIS (Hospital Information System). Further, when the information related to the subject P is stored in the storage circuit 135 in advance, the estimation function 136b can read the information related to the subject P from the storage circuit 135. Alternatively, the estimation function 136b may be a case where the input of the information relating to the subject P is received via the input circuit 131.

Next, the adjustment function 136c adjusts the setting of the detector 113 based on the thickness of the subject P estimated by the estimation function 136b and the tube current value of the X-ray tube 112a. Here, the adjustment of the setting of the detector 113 based on the thickness of the subject P estimated by the estimation function 136b will be described with reference to FIG. 4B. FIG. 4B is a diagram for explaining adjustment of the setting of the detector 113 according to the first embodiment. Here, in the graph shown in FIG. 4B, each X-ray detection element of the X-ray detector 113a detects X-rays emitted from the X-ray tube 112a at a predetermined tube current value, and the data acquisition circuit 113b determines the X-rays. The distribution of the count value when amplified by the gain and collected is shown. Further, the horizontal axis of FIG. 4B indicates the number of channels, and corresponds to each X-ray detection element included in the X-ray detector 113a. That is, the horizontal axis indicates the position coordinates on the X-ray detector 113a. The vertical axis in FIG. 4B shows the count value after the data acquisition circuit 113b amplifies with a predetermined gain. In the following, the tube current value of the X-ray tube 112a will be described as being a constant value. For example, the tube current value of the X-ray tube 112a is a fixed value set in advance or a value input by the operator via the input circuit 131.

For example, the adjustment function 136c first calculates the distribution of the thickness of the subject P in the FOV from the thickness of the subject P estimated by the estimation function 136b, assuming that the subject P is located at the center of the FOV at the time of scanning. To do. Next, the adjustment function 136c estimates the distribution of count values based on the calculated thickness distribution, as shown in the solid line portion of the graph of FIG. 4B. Further, the adjustment function 136c adjusts the gain so that the amplification factor when the data collection circuit 113b collects data becomes large in the range where the maximum value of the count value does not enter the overflow region. The adjustment function 136c then optimizes the settings of the detector 113 so as to avoid overflow and reduce artifacts due to circuit noise.

Alternatively, the adjustment function 136c can select a gain from a plurality of gains for which the data amplification factor is set in advance so that the count value does not overflow and an artifact due to circuit noise does not occur. For example, the adjustment function 136c first sets the lower limit of the thickness of the subject P from which data can be collected without causing overflow for each of the plurality of gains for which the amplification factor is set, and the artifact due to circuit noise. The upper limit of the thickness of the subject P from which CT image data can be acquired is determined according to the tube current value of the X-ray tube 112a. Then, the adjustment function 136c compares the thickness of the subject P estimated by the estimation function 136b with the upper and lower limit values determined for each gain, and gains that can avoid both overflow and artifacts due to circuit noise. Select. The adjustment function 136c sets the gain with the least possibility of overflow or the gain with the least influence of circuit noise when there are a plurality of gains that can avoid both overflow and artifacts due to circuit noise. select. Alternatively, the adjustment function 136c accepts a selection operation from the operator as to which of the plurality of gains to select when there are a plurality of gains capable of avoiding both overflow and artifacts due to circuit noise.

When the cross section of the subject P is not circular, the thickness of the subject P changes depending on the X-ray irradiation direction as shown in FIGS. 5A and 5B. Here, FIGS. 5A and 5B are diagrams for explaining the thickness of the subject P according to the first embodiment. As shown in FIGS. 5A and 5B, the X-ray generator 112 at the time of scanning moves around the subject P as the rotating frame 114 rotates. Here, the estimation function 136b estimates the thickness of the subject P for each position of the X-ray generator 112, that is, for each angle at which X-rays are applied to the subject P.

For example, when the positional relationship between the subject P having an elliptical cross-sectional shape and the X-ray generator 112 is in the state shown in FIG. 5A, the estimation function 136b performs the cross section of the subject P as shown in FIG. 5A. The length corresponding to the minor axis of the subject P is defined as the thickness of the subject P. Further, for example, when the positional relationship between the subject P and the X-ray generator 112 is in the state shown in FIG. 5B, the estimation function 136b corresponds to the long axis of the cross section of the subject P as shown in FIG. 5B. Let the length be the thickness of the subject P. Then, the adjustment function 136c can adjust the setting of the detector 113 for each X-ray irradiation angle based on the thickness of the subject P for each X-ray irradiation angle and the predetermined tube current value. ..

Further, in the above-mentioned example, the tube current value of the X-ray tube 112a has been described as being a constant value, but as shown in FIGS. 5A and 5B, the estimation function 136b has a thickness for each X-ray irradiation angle. When estimating, the tube current value may be set differently for each X-ray irradiation angle. For example, when the positional relationship between the subject P and the X-ray generator 112 is in the state shown in FIG. 5A, the thickness of the subject P through which the irradiated X-rays pass is smaller than that in the case of FIG. 5B. Therefore, the attenuation of X-rays by passing through the subject P is small. Therefore, in FIG. 5A, the tube current value of the X-ray tube 112a is set to a small value because a sufficient X-ray dose reaches the detector 113 even if the irradiated X-ray dose is small. Further, for example, when the positional relationship between the subject P and the X-ray generator 112 is in the state shown in FIG. 5B, the thickness of the subject P through which the irradiated X-rays pass is compared with the case of FIG. 5A. X-rays are greatly attenuated by passing through the subject P. Therefore, in FIG. 5B, since a sufficient X-ray dose does not reach the detector 113 unless the irradiated X-ray dose is increased, the tube current value of the X-ray tube 112a is set to a large value. Then, the adjustment function 136c is based on the thickness of the subject P for each X-ray irradiation angle and the tube current value set so as to be different for each X-ray irradiation angle, for each X-ray irradiation angle. Adjust the settings of the detector 113.

After estimating the thickness of the subject P by the estimation function 136b and adjusting the setting of the detector 113 by the adjustment function 136c, the X-ray CT apparatus 100 executes an imaging and reconstruction process. Specifically, when the control function 136d receives a request to start shooting, the control function 136d controls the scan control circuit 133 to control the X-ray irradiation control circuit 111, the gantry drive circuit 115, the data acquisition circuit 113b, and the sleeper drive device 121. The operation is controlled, and the subject P is photographed on the gantry 110. Then, the X-ray detector 113a detects the X-rays irradiated from the X-ray tube 112a and transmitted through the subject P, and the data acquisition circuit 113b collects the CT projection data derived from the detected X-rays. Further, the reconstruction function 136a reconstructs the CT projection data collected by the data collection circuit 113b to acquire CT image data.

Next, an example of the processing procedure by the X-ray CT apparatus 100 will be described with reference to FIG. FIG. 6 is a flowchart for explaining a series of processes of the X-ray CT apparatus 100 according to the first embodiment. Step S160 is a step corresponding to the reconstruction function 136a. Step S120 is a step corresponding to the estimation function 136b. Step S130 is a step corresponding to the adjustment function 136c. Step S110, step S140, step S150 and step S170 are steps corresponding to the control function 136d.

First, the processing circuit 136 determines whether or not the inspection start request has been received from the operator (step S110). When the inspection start request is not accepted (step S110 is denied), the processing circuit 136 is in the standby state. On the other hand, when the test start request is received (step S110 affirmative), the processing circuit 136 estimates the thickness of the subject P (step S120), and the estimated thickness of the subject P and the tube current of the X-ray tube 112a. The setting of the detector 113 is adjusted from the value (step S130).

Here, the processing circuit 136 determines whether or not a shooting start request has been received from the operator (step S140). When the shooting start request is not accepted (step S140 is denied), the processing circuit 136 is in the standby state. On the other hand, when the imaging start request is received (step S140 affirmative), the processing circuit 136 executes detection of X-rays transmitted through the subject P and collection of CT projection data in the adjusted detector 113 settings (step S140 affirmation). Step S150).

Then, the processing circuit 136 reconstructs the CT projection data collected from the subject P to acquire the CT image data (step S160), and determines whether or not the end command has been received from the operator (step S170). When the end command is not accepted (step S170 is denied), the processing circuit 136 goes into a standby state. On the other hand, when the end command is received (step S170 affirmative), the processing circuit 136 ends the processing.

The processing circuit 136 may notify the operator when the setting of the detector 113 cannot be optimized in step S130. For example, the processing circuit 136 can notify the operator that no matter how the gain is adjusted, at least one of the artifacts due to overflow and circuit noise will occur. In this case, the processing circuit 136 may receive the setting of the tube current value of the X-ray tube 112a from the operator after step S130, and may shift to step S130 again.

As described above, according to the first embodiment, the detector 113 detects the X-rays irradiated from the X-ray tube 112a and transmitted through the subject P, and collects the data derived from the detected X-rays. In addition, the reconstruction function 136a reconstructs the data and acquires CT image data. In addition, the estimation function 136b estimates the thickness of the subject P. Further, the adjustment function 136c adjusts the setting of the detector 113 based on the thickness of the subject P estimated by the estimation function 136b and the tube current value of the X-ray tube 112a. Therefore, the X-ray CT apparatus 100 according to the first embodiment can optimize the setting of the detector 113 even when the positioning image is not collected.

Further, the X-ray CT apparatus 100 according to the first embodiment is a count collected by the detector 113 when X-rays are irradiated at a predetermined tube current value based on the distribution of the thickness of the subject P in the FOV. The maximum value of the value is estimated, and the predetermined gain of the detector 113 is adjusted so that the estimated maximum value does not enter the overflow region. Therefore, the X-ray CT apparatus 100 according to the first embodiment can acquire CT image data in which the gain is set so that the count value becomes large while avoiding overflow, and the occurrence of artifacts due to circuit noise is suppressed. it can.

Further, the X-ray CT apparatus 100 according to the first embodiment acquires CT image data after optimizing the setting of the detector 113 without performing a scan for collecting a positioning image. Therefore, the X-ray CT apparatus 100 according to the first embodiment can reduce the exposure dose of the subject P.

(Second Embodiment)
In the first embodiment described above, the case where the setting of the detector 113 is adjusted assuming that the subject P at the time of scanning is located at the center of the FOV has been described. On the other hand, in the second embodiment, a case where the setting of the detector 113 is adjusted in consideration of the deviation amount (offset amount) of the subject P from the FOV center will be described. The X-ray CT apparatus according to the second embodiment has the same configuration as the X-ray CT apparatus 100 according to the first embodiment shown in FIG. 1, and the processing in the adjustment function 136c is partially different. .. Therefore, the points having the same functions as those described in the first embodiment are designated by the same reference numerals as those in FIG. 1, and the description thereof will be omitted.

Hereinafter, the adjustment function 136c according to the second embodiment will be described with reference to FIG. 7. FIG. 7 is a diagram for explaining adjustment of the setting of the detector 113 according to the second embodiment. The horizontal axis of FIG. 7 indicates the number of channels and corresponds to each X-ray detection element included in the X-ray detector 113a. That is, the horizontal axis indicates the position coordinates on the X-ray detector 113a. The numbers on the vertical axis in FIG. 7 indicate count values. Further, FIG. 7 shows an X that is irradiated from the X-ray tube 112a with a predetermined tube current value under the condition that the subject P is in the X-ray irradiation range, and has passed through the subject P having the thickness estimated by the estimation function 136b. The adjustment function 136c predicts the distribution of the count value when each X-ray detection element of the X-ray detector 113a detects the line and the data collection circuit 113b amplifies and collects the line with a predetermined gain.

First, when there is no subject P, the position where the count value becomes the maximum value (Peek) corresponds to the center of the FOV. Here, the position of the subject P at the time of scanning may deviate from the position of the center of the FOV depending on the scanning content. For example, in the case of examining the right lung, in order to acquire high-quality CT image data for the right lung, the scan is performed so that the right lung is the center of the FOV. In this case, since the right lung, which is the site of interest, is located at a position deviated from the body axis of the subject P, the position of the center of the subject P (chest) at the time of scanning and the position of the center of the FOV are deviated.

The maximum value of the count value changes according to the deviation of the position of the subject P from the center of the FOV. For example, as shown in FIG. 7, when the subject P is located off the center of the FOV as compared with the case where the subject P is located at the center of the FOV, the maximum value of the count value becomes larger. Therefore, the adjustment function 136c calculates the position of the subject P, and the thickness of the subject P in the FOV is based on the calculated position of the subject P and the thickness of the subject P estimated by the estimation function 136b. Calculate the distribution. Then, the adjustment function 136c calculates the maximum value of the count value based on the calculated distribution of the thickness of the subject P, and adjusts the gain of the detector 113.

Specifically, first, the adjustment function 136c acquires the position information of the sleeper 122 on which the subject P is placed. The position information of the sleeper 122 is information indicating the position of the sleeper 122 with respect to the gantry 110 at the time of scanning. Here, the sleeper 122 is moved by the sleeper drive device 121 controlled by the scan control circuit 133 under the control of the control function 136d according to the photographing plan. Therefore, the adjustment function 136c can acquire the position information at the time of scanning the sleeper 122 based on the shooting plan. The adjustment function 136c may acquire only the position information in the Y-axis direction shown in FIG. 1 as the position information of the sleeper 122, or further acquire the position information in the X-axis direction and the Z-axis direction. It may be the case.

Next, the adjustment function 136c calculates the position of the subject P using the position information of the sleeper 122. For example, the adjustment function 136c calculates the position of the subject P from the amount of movement of the sleeper 122, assuming that the subject P is placed in the substantially central portion of the sleeper 122. For example, the adjustment function 136c calculates the position of the subject P in the Y-axis direction by using the position information of the sleeper 122 in the Y-axis direction. Further, for example, the adjustment function 136c can calculate the positions of the subject P in the X-axis direction and the Z-axis direction by using the position information of the sleeper 122 in the X-axis direction and the Z-axis direction.

Then, the adjustment function 136c acquires the distribution of the thickness of the subject P in the FOV from the position and the thickness of the subject P. Here, in FIG. 7, the maximum value (Peak) of the count value is in the overflow region. Therefore, if shooting is executed with the gain setting in FIG. 7, an overflow occurs. Therefore, the adjustment function 136c adjusts a predetermined gain so that the maximum value (Peak) of the count value shown in FIG. 7 does not enter the overflow region. Reduce the data amplification factor.

That is, by calculating the position of the subject P, the adjustment function 136c is collected by the detector 113 when the detector 113 irradiates X-rays with a predetermined tube current value based on the distribution of the thickness of the subject P in the FOV. The maximum value of the count value to be used is estimated more appropriately, and the setting of the detector 113 is adjusted so that the estimated maximum value does not enter the overflow region. Then, the adjustment function 136c reduces artifacts due to circuit noise of the reconstructed CT image data while preventing overflow during shooting.

Next, an example of the processing procedure by the X-ray CT apparatus 100 according to the second embodiment will be described with reference to FIG. FIG. 8 is a flowchart for explaining a series of processes of the X-ray CT apparatus 100 according to the second embodiment. Step S270 is a step corresponding to the reconstruction function 136a. Step S220 is a step corresponding to the estimation function 136b. Step S230 and step S240 are steps corresponding to the adjustment function 136c. Step S210, step S250, step S260 and step S280 are steps corresponding to the control function 136d.

First, the processing circuit 136 determines whether or not the inspection start request has been received from the operator (step S210). When the inspection start request is not accepted (step S210 is denied), the processing circuit 136 is in the standby state. On the other hand, when the test start request is received (step S210 affirmative), the processing circuit 136 estimates the thickness of the subject P (step S220). Next, the processing circuit 136 calculates the position of the subject P by using the position information of the sleeper 122 on which the subject P is placed (step S230). Then, the processing circuit 136 adjusts the setting of the detector 113 from the position of the subject P, the estimated thickness of the subject P, and the tube current value of the X-ray tube 112a (step S240).

Here, the processing circuit 136 determines whether or not a shooting start request has been received from the operator (step S250). When the shooting start request is not accepted (step S250 is denied), the processing circuit 136 is in the standby state. On the other hand, when the imaging start request is received (step S250 affirmative), the processing circuit 136 executes detection of X-rays transmitted through the subject P and collection of CT projection data in the adjusted detector 113 setting (step S250 affirmation). Step S260).

Then, the processing circuit 136 reconstructs the data collected from the subject P to acquire the CT image data (step S270), and determines whether or not the end command has been received from the operator (step S280). If the end command is not accepted (step S280 negated), the processing circuit 136 goes into a standby state. On the other hand, when the end command is received (step S280 affirmative), the processing circuit 136 ends the processing.

As described above, according to the second embodiment, the adjustment function 136c calculates the position of the subject P using the position information of the bed 122 on which the subject P is placed, and the calculated position of the subject P is calculated. The distribution of the thickness of the subject P in the FOV is calculated based on the position and the thickness of the subject P estimated by the estimation function 136b, and the maximum value of the count value is estimated and estimated based on the calculated distribution. Adjust the gain so that the maximum value is not included in the overflow area. Therefore, the X-ray CT apparatus 100 according to the second embodiment more appropriately adjusts the gain of the detector 113 in consideration of the offset amount of the position of the subject P from the FOV center to avoid overflow. , It is possible to suppress the generation of artifacts due to circuit noise.

(Third Embodiment)
In the first embodiment described above, a case where the thickness of the subject P is estimated based on the standard body shape information has been described. On the other hand, in the third embodiment, a case where the thickness of the subject P is estimated based on the medical image of the subject P captured in the past will be described. The X-ray CT apparatus according to the third embodiment has the same configuration as the X-ray CT apparatus 100 according to the first embodiment shown in FIG. 1, and the processing in the estimation function 136b is partially different. .. Therefore, the points having the same functions as those described in the first embodiment are designated by the same reference numerals as those in FIG. 1, and the description thereof will be omitted.

First, the estimation function 136b acquires a medical image of the subject P. For example, the estimation function 136b provides a medical image of the subject P such as a CT image, an MRI image generated by a magnetic resonance imaging (MRI) device, an ultrasonic image generated by an ultrasonic diagnostic device, and the like. Medical images can be obtained. The estimation function 136b can acquire a medical image of the subject P through various systems such as RIS (Radiology Information System) and HIS (Hospital Information System). Alternatively, when the medical image of the subject P is stored in the storage circuit 135 in advance, the estimation function 136b can read the medical image of the subject P from the storage circuit 135.

Next, the estimation function 136b estimates the thickness of the subject P by using the medical image of the subject P captured in the past. For example, when the imaging site of the subject P is the head, the estimation function 136b can acquire the value of the thickness of the head from the medical image and estimate the acquired value as the thickness of the subject P. The estimation function 136b may be a case where the medical image is corrected by using the information related to the subject P and the thickness of the subject P is estimated by using the corrected medical image.

As described above, according to the third embodiment, the estimation function 136b estimates the thickness of the subject P based on the medical image of the subject P imaged in the past. Therefore, the X-ray CT apparatus 100 according to the third embodiment can optimize the setting of the detector 113 without collecting the positioning image even when the standard body shape information is not available.

(Fourth Embodiment)
As described above, the estimation function 136b can estimate the thickness of the subject P. Here, the scan of the subject P may be performed a plurality of times. For example, the lung field is photographed in the first scan, and the abdomen is photographed in the second scan. In the fourth embodiment, a case where the thickness of the subject P in the second and subsequent scans is estimated when a plurality of times of imaging are performed will be described. The X-ray CT apparatus according to the fourth embodiment has the same configuration as the X-ray CT apparatus 100 according to the first embodiment shown in FIG. 1, and has a reconstruction function 136a, an estimation function 136b, and adjustment. The processing in the function 136c is partially different. Therefore, the points having the same functions as those described in the first embodiment are designated by the same reference numerals as those in FIG. 1, and the description thereof will be omitted.

First, the estimation function 136b estimates the thickness of the subject P for the first imaging target site based on the above-mentioned standard body shape information or the medical image of the subject P captured in the past. Next, in the setting of the detector 113 based on the estimated thickness, the first scan is executed, and the CT image data of the first imaging target portion of the subject P is reconstructed. Here, the estimation function 136b can estimate the thickness of the second and subsequent imaging target portions by using the CT image data of the first imaging target portion of the subject P. In the following, the first imaging target site will be referred to as the first imaging site, and the second and subsequent imaging target sites will be referred to as the second imaging site.

As an example, the estimation function 136b first acquires the thickness of the first portion based on the CT image data obtained by the first scan. Next, the estimation function 136b calculates the ratio between the thickness of the first part estimated based on the standard body shape information and the thickness of the first part acquired based on the CT image data. Then, the estimation function 136b can correct the thickness of the second portion based on the standard body shape information according to the calculated ratio, and can estimate the thickness of the second portion.

Further, for example, the estimation function 136b first acquires the thickness of the first portion "right hand" based on the CT image data obtained by the first scan. Next, the estimation function 136b assumes that the thickness of the right hand and the thickness of the left hand of the subject P are about the same, and from the thickness of the first part "right hand" to the thickness of the second part "left hand". Can be estimated.

Next, the adjustment function 136c detects data derived from X-rays transmitted through the second portion based on the thickness of the second portion estimated by the estimation function 136b and the tube current value of the X-ray tube 112a. Adjust the settings when the device 113 collects. Then, in the adjusted detector 113 setting, the control function 136d executes the second scan, and the reconstruction function 136a reconstructs the CT projection data collected in the adjusted detector 113 setting. Then, the CT image data of the second part is acquired.

As described above, according to the fourth embodiment, the estimation function 136b estimates the thickness of the second part different from the first part based on the CT image data of the first part of the subject P. To do. Further, the adjustment function 136c is used when the detector 113 collects data derived from X-rays transmitted through the second portion based on the thickness of the second portion estimated by the estimation function 136b and the tube current value. Adjust the settings of. In addition, the reconstruction function 136a reconstructs the data collected by the adjusted setting to acquire the CT image data of the second portion. Therefore, the X-ray CT apparatus 100 according to the fourth embodiment more accurately estimates the thickness of the second portion to be photographed from the second time onward when the subject P is photographed a plurality of times. can do.

(Fifth Embodiment)
By the way, although the first to fourth embodiments have been described so far, various different embodiments may be implemented in addition to the above-described embodiments.

In the above-described embodiment, the estimation function 136b estimates the thickness of the subject P based on the standard body shape information, the medical image of the subject P taken in the past, or the information of the first main scan. explained. However, the embodiment is not limited to this, and for example, the estimation function 136b may be a case where the thickness of the subject P is estimated based on the fixed size set for each site.

Each component of each device according to the first to fifth embodiments is a functional concept, and does not necessarily have to be physically configured as shown in the figure. That is, the specific form of distribution / integration of each device is not limited to the one shown in the figure, and all or part of the device is functionally or physically distributed in arbitrary units according to various loads and usage conditions. It can be integrated and configured. Further, each processing function performed by each device may be realized by a CPU and a program analyzed and executed by the CPU, or may be realized as hardware by wired logic.

Further, the control method described in the first to fifth embodiments can be realized by executing a control program prepared in advance on a computer such as a personal computer or a workstation. This control program can be distributed via a network such as the Internet. Further, this control program can also be executed by being recorded on a computer-readable recording medium such as a hard disk, flexible disk (FD), CD-ROM, MO, or DVD, and being read from the recording medium by the computer.

According to at least one embodiment described above, the detector settings can be optimized even when the positioning image is not collected.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

100 X-ray CT device 136 Processing circuit 136a Reconstruction function 136b Estimation function 136c Adjustment function 136d Control function

Claims (12)

It is an X-ray CT device,
A detector that detects X-rays that are irradiated from an X-ray tube and have passed through the subject, and collects data derived from the detected X-rays .
Before CT scanning the designated part of the subject, the first control to execute the first imaging method in which the positioning imaging for the CT scan is performed by the detector, and the CT of the designated part. Before scanning, a control unit that performs either one of the second control that executes the second imaging method that does not perform the positioning imaging, and
When executing the first imaging method, the setting of the detector for CT scanning of the specified portion is adjusted based on the positioning image obtained by the positioning imaging, and the second imaging method is performed. When performing, an adjusting unit that adjusts the settings of the detector for a CT scan of the specified site based on at least information on the subject or the specified site .
An X-ray CT apparatus. The adjusting unit adjusts a predetermined gain as the setting, and then adjusts the gain.
The X-ray CT apparatus according to claim 1, wherein the detector amplifies and collects data with the predetermined gain adjusted by the adjusting unit. It is provided with an estimation unit that estimates the thickness of the subject.
The adjusting unit estimates the maximum value of the count value collected by the detector when the X-ray is irradiated with the tube current value of the X-ray tube based on the distribution of the thickness in the imaging field of view. The X-ray CT apparatus according to claim 2, wherein the predetermined gain is adjusted so that the maximum value does not enter the overflow region. The adjusting unit calculates the position of the subject using the position information of the bed on which the subject is placed, and based on the calculated position of the subject and the thickness estimated by the estimation unit. , The distribution of the thickness in the imaging field of view is calculated, the maximum value of the count value is estimated based on the calculated distribution, and the predetermined gain is adjusted so that the maximum value does not enter the overflow region. Item 3. The X-ray CT apparatus according to Item 3. It is provided with an estimation unit that estimates the thickness of the subject.
The X-ray CT apparatus according to any one of claims 1 to 4, wherein the estimation unit estimates the thickness based on standard body shape information indicating standard dimensions for each part. The X-ray CT apparatus according to claim 5, wherein the estimation unit corrects the standard body shape information based on the information related to the subject, and estimates the thickness based on the corrected standard body shape information. It is provided with an estimation unit that estimates the thickness of the subject.
The X-ray CT apparatus according to any one of claims 1 to 4, wherein the estimation unit estimates the thickness based on a medical image of the subject imaged in the past. It is provided with an estimation unit for estimating the thickness of the subject and a reconstruction unit for reconstructing the data collected by the detector to acquire CT image data.
The estimation unit estimates the thickness of the second part different from the first part based on the CT image data of the first part of the subject.
The adjusting unit detects data derived from X-rays transmitted through the second portion based on the thickness of the second portion estimated by the estimation unit and the current value of the X-ray tube. Adjust the above settings when the vessel collects,
The X-ray CT according to any one of claims 1 to 4, wherein the reconstructing unit reconstructs the data collected by the adjusted setting to acquire CT image data of the second portion. apparatus. It is provided with an estimation unit that estimates the thickness of the subject.
The estimation unit estimates the thickness for each angle at which the X-ray is irradiated.
The adjusting unit receives the X-rays based on the thickness of each angle and the tube current value of the X-ray tube set to be different for each angle of irradiating the subject with the X-rays. The X-ray CT apparatus according to any one of claims 1 to 8, wherein the setting is adjusted for each irradiation angle. A detector that detects X-rays that are irradiated from an X-ray tube and have passed through the subject, and collects data derived from the detected X-rays.
A reconstruction unit that reconstructs the data collected by the detector to acquire CT image data, and
An estimation unit that estimates the thickness of the subject,
A adjusting unit for adjusting a predetermined gain of the detector based on the thickness estimated by the estimating unit and the tube current value of the X-ray tube is provided.
The adjusting unit estimates the maximum value of the count value collected by the detector when the X-ray is irradiated with the tube current value based on the distribution of the thickness in the photographing field of view, and the maximum value overflows. Adjust the predetermined gain so that it does not enter the area,
The detector is an X-ray CT apparatus that amplifies and collects data with the predetermined gain adjusted by the adjusting unit. A detector that detects X-rays that are irradiated from an X-ray tube and have passed through the subject, and collects data derived from the detected X-rays.
A reconstruction unit that reconstructs the data collected by the detector to acquire CT image data, and
An estimation unit that estimates the thickness of a second site different from the first site based on CT image data of the first site of the subject, and an estimation unit.
When the detector collects data derived from X-rays transmitted through the second portion based on the thickness of the second portion estimated by the estimation unit and the tube current value of the X-ray tube. It is provided with an adjustment unit for adjusting the settings of the detector.
The reconstructing unit is an X-ray CT apparatus that reconstructs the data collected by the adjusted setting and acquires CT image data of the second portion. A detector that detects X-rays that are irradiated from an X-ray tube and have passed through the subject, and collects data derived from the detected X-rays.
A reconstruction unit that reconstructs the data collected by the detector to acquire CT image data, and
An estimation unit that estimates the thickness of the subject for each angle of X-ray irradiation,
The X-ray is based on the thickness of each angle estimated by the estimation unit and the tube current value of the X-ray tube set to be different for each angle of irradiating the subject with the X-ray. An adjustment unit that adjusts the settings of the detector for each angle of irradiation,
An X-ray CT apparatus.

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