Medical system and recording medium

Abstract

To provide a technique capable of shortening the time required for calibration. [Solution] A medical system, comprising a CT system that performs imaging to obtain a CT image of a subject, the CT system including one or more processors, the one or more processors performing the following each time imaging is performed: selecting calibration data from a plurality of calibration data C1 to C3 to be used to reconstruct an image, and determining the update frequency of each calibration data based on the number of times each calibration data is used and a weighting coefficient according to the imaging purpose of the imaging performed.

Description

[Technical field]

[0001] The present invention relates to a medical system that performs beam hardening correction, and a recording medium having instructions recorded thereon for controlling the medical system. [Background technology]

[0002] CT systems are known as medical devices that capture images of subjects non-invasively. CT systems are widely used in hospitals and other medical facilities because they can obtain cross-sectional images of subjects in a short scanning time.

[0003] A CT system applies a certain voltage to the cathode-anode tube of an X-ray tube to generate X-rays. The generated X-rays pass through the subject and are detected by a detector. The CT system reconstructs a CT image of the subject based on the data detected by the detector. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6031618 Summary of the Invention [Problem to be solved by the invention]

[0005] SECT (Single Energy CT) is known as an imaging technique for CT systems. SECT is a method of applying a certain voltage (e.g., 120 kV) to the cathode-anode tube of an X-ray tube to generate X-rays and obtain a CT image of the subject. However, with SECT, different substances can have similar CT values, making it difficult to identify different substances.

[0006] Therefore, DECT (Dual Energy CT) technology is being researched and developed. DECT is a technology that can distinguish materials by using X-rays in different energy ranges, and can obtain images that are useful for diagnosis in clinical settings, and is beginning to be widely used. In DECT technology, kV switching technology is known, which switches the tube voltage of the X-ray tube between low and high tube voltages.

[0007] In addition, the parts of a CT system deteriorate over a long period of use, and as a result, the calibration data used to calibrate the CT system deviates from the ideal values. Therefore, the CT system periodically performs a calibration scan to obtain the calibration data required to calibrate the CT system.

[0008] For example, the material decomposition accuracy of kV switching by DECT depends on the rotation speed of the gantry, the cone angle, the tube current, etc. For this reason, in calibration, multiple combinations of the values ​​of these parameters (rotation speed, cone angle, and tube current) are prepared in advance as presets, and a calibration scan is performed for each preset to obtain calibration data. Therefore, multiple calibration scans must be performed for one calibration, which poses a problem of long calibration time.

[0009] Therefore, there is a demand for technology that can shorten the time required for one calibration. [Means for solving the problem]

[0010] A first aspect of the present invention is a medical system that performs imaging to obtain a medical image of a subject, comprising: the medical system includes one or more processors; The one or more processors: selecting calibration data to be used for reconstructing an image from among the plurality of calibration data each time imaging is performed; Determining the update frequency of each calibration data based on the number of times each calibration data is used and a weighting factor according to the photographing purpose of the photographing performed. This is a medical system that performs the following:

[0011] The second aspect of the present invention is 1. A non-transitory computer readable storage medium included in or in communication with a medical system, comprising: The instructions stored on the storage medium, when executed by the one or more processors, cause the one or more processors to: selecting calibration data to be used for reconstructing an image from among the plurality of calibration data each time imaging is performed; Determining the update frequency of each calibration data based on the number of times each calibration data is used and a weighting factor according to the photographing purpose of the photographing performed. A non-transitory computer-readable storage medium for causing It is. Effect of the Invention

[0012] In the present invention, The update frequency of each calibration data is determined based on the number of times each calibration data is used and a weighting coefficient according to the shooting purpose of the executed shooting. Therefore, when the calibration data is used less frequently or when the calibration data is used for shooting with a small weighting coefficient, the update frequency of the calibration data can be reduced, so that the time required for one calibration can be shortened. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a block diagram of a CT system 10 according to the present embodiment. [Diagram 2] FIG. 11 is an explanatory diagram of calibration. [Diagram 3] FIG. 1 is an illustration of the steps performed on clinic day 1. [Figure 4] FIG. 13 is a diagram showing a state in which shooting 1 is performed. [Diagram 5] FIG. 2 is a flow diagram of a method for determining the update frequency of the calibration data D1, D2, and D3. [Figure 6] FIG. 6 is a table for explaining steps ST1 to ST4 of FIG. [Figure 7] FIG. 13 is a diagram showing index values ​​and update frequencies of calibration data D1, D2, and D3 stored in association with shooting 1. [Figure 8] FIG. 13 is a diagram showing a state in which shooting 2 has been performed. [Figure 9] 6 is a table for explaining each step of FIG. 5 when shooting 2 is executed. [Figure 10] FIG. 13 is a diagram showing index values ​​and update frequencies of calibration data D1, D2, and D3 stored in association with shooting 2. [Figure 11] FIG. 13 is a diagram showing a state in which photographing 3 has been performed. [Figure 12] FIG. 6 is a diagram showing a table for explaining each step in FIG. 5 when photographing 3 is performed. [Figure 13] FIG. 13 is a diagram showing index values ​​and update frequencies of calibration data D1, D2, and D3 stored in association with shooting 3. [Figure 14] FIG. 13 is a diagram showing a state in which shooting 4 is performed. [Figure 15] FIG. 6 is a table for explaining each step in FIG. 5 when photographing 4 is performed. [Figure 16] FIG. 13 is a diagram showing index values ​​and update frequencies of calibration data D1, D2, and D3 stored in association with shooting 4. [Figure 17] FIG. 13 is a diagram showing a state in which photographing 5 is performed. [Figure 18] FIG. 6 is a diagram showing a table for explaining each step in FIG. 5 when photographing 5 is performed. [Figure 19]FIG. 13 is a diagram showing index values ​​and update frequencies of calibration data D1, D2, and D3 stored in association with shooting 5. [Figure 20] FIG. 13 is an explanatory diagram of clinic day 2. [Figure 21] FIG. 11 is an explanatory diagram of step ST22. [Figure 22] FIG. 6 is a table for explaining each step in FIG. 5 when photographing 6 is performed. [Diagram 23] FIG. 13 is a diagram showing index values ​​and update frequencies of calibration data D1, D2, and D3 stored in association with shooting 6. [Figure 24] FIG. 13 is a diagram showing the index values ​​and update frequency obtained in the last imaging p on clinical day 2. [Diagram 25] FIG. 13 is an explanatory diagram of clinic day 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, a mode for carrying out the invention will be described, however, the present invention is not limited to the following mode.

[0015] FIG. 1 is a block diagram of a CT system 10 according to the present embodiment.

[0016] The CT system 10 includes a gantry 102 and a table 116 .

[0017] The gantry 102 has a bore 107 into which a subject 112 is transferred and scanned.

[0018] The gantry 102 is equipped with an X-ray generator 104, a filter section 103, a pre-collimator 105, a detector 108, and the like.

[0019] The X-ray generating device 104 includes an X-ray tube 104A and a generator 104B. The generator 104B supplies power to the X-ray tube 104A. The X-ray tube 104A outputs X-rays by applying a predetermined voltage to the cathode-anode tube. The X-ray tube 104 is configured to be able to rotate on a path centered on a rotation axis 206 in the XY plane. Here, the Z direction represents the body axis direction, the Y direction represents the vertical direction (the height direction of the table 116), and the X direction represents a direction perpendicular to the Z direction and the Y direction. In this embodiment, the X-ray tube 104A is an X-ray tube compatible with a kV switching method in which the tube voltage applied to the X-ray tube can be alternately switched between a first tube voltage and a second tube voltage. In this embodiment, the CT system 10 includes one X-ray tube 104A, but may include two X-ray tubes 104A.

[0020] The filter section 103 includes, for example, a flat plate filter and / or a bowtie filter.

[0021] The pre-collimator 105 is a member for narrowing down the irradiation range of X-rays so that unnecessary regions are not irradiated with X-rays.

[0022] The detector 108 includes a plurality of detector elements 202. The plurality of detector elements 202 detects X-rays 106 emitted from the X-ray tube 104A and passing through a subject 112, such as a patient. Thus, the X-ray detector 108 can acquire projection data for each view.

[0023] Projection data detected by detector 108 is collected by the DAS 214. The DAS 214 performs predetermined processing, including sampling, digital conversion, etc., on the collected projection data. The processed projection data is The data is transmitted to a computer 216. The computer 216 stores the data from the DAS 214 in a storage device 218. The storage device 218 stores programs, instructions to be executed by a processor, and the like. One or more The storage medium may be, for example, One or more non-transitory computer-readable storage medium It can be said that:The storage devices 218 may include, for example, a hard disk drive, a floppy disk drive, a compact disk read / write (CD-R / W) drive, a digital versatile disk (DVD) drive, a flash drive, and / or a solid-state recording drive.

[0024] The computer 216 includes one or more processors 217. The computer 216 uses the one or more processors to output commands and parameters to the DAS 214, the X-ray controller 210, and / or the gantry motor controller 212 to control system operations such as data acquisition and / or processing. The computer 216 also uses the one or more processors to perform various processes such as signal processing, data processing, and image processing in each step of the flow described below. Although the one or more processors 217 are included in the computer 216 in FIG. 1, the one or more processors 217 may be provided distributed between the computer 216 and other components (e.g., the X-ray controller 210, the gantry motor controller 212, the table controller 118, etc.).

[0025] An operator console 220 is coupled to the computer 216. An operator can operate the operator console 220 to input certain operator inputs related to the operation of the CT system 10 to the computer 216. The computer 216 receives operator inputs, including commands and / or scan parameters, via the operator console 220 and controls system operations based on the operator inputs. The operator console 220 can include a keyboard (not shown) or a touch screen for the operator to enter commands and / or scan parameters.

[0026] The X-ray controller 210 controls the X-ray generator 104 based on instructions from a computer 216. Also, the gantry motor controller 212 controls the gantry motor based on instructions from the computer 216 so that components such as the X-ray tube 104A and the detector 108 rotate.

[0027] Although FIG. 1 shows only one operator console 220 , two or more operator consoles may be coupled to computer 216 .

[0028] The CT system 10 may also be coupled to multiple remotely located displays, printers, workstations, and / or similar devices, for example, via wired and / or wireless networks.

[0029] In one embodiment, for example, CT system 10 may include or be coupled to a picture archiving and communication system (PACS) 224. In an exemplary implementation, PACS 224 may be coupled to a remote system, such as a radiology department information system, a hospital information system, and / or an internal or external network (not shown).

[0030] The computer 216 supplies instructions to the table motor controller 118 for controlling the table 116. Based on the received instructions, the table motor controller 118 can control the table motor so as to move the table 116. For example, the table motor controller 118 can move the table 116 so that the subject 112 is positioned in a position suitable for imaging.

[0031] As described above, the DAS 214 samples and digitally converts the projection data acquired by the detector elements 202. The image reconstructor 230 then reconstructs the CT image using the sampled and digitally converted data. The image reconstructor 230 includes one or more processors that may perform the image reconstruction process. Although the image reconstructor 230 is shown in FIG. 1 as a separate component from the computer 216, the image reconstructor 230 may form part of the computer 216. The computer 216 may also perform one or more functions of the image reconstructor 230. Additionally, the image reconstructor 230 may be located remotely from the CT system 10 and operatively connected to the CT system 10 using a wired or wireless network.

[0032] The image reconstructor 230 can store the reconstructed image in the storage device 218. The image reconstructor 230 may also transmit the reconstructed image to the computer 216. The computer 216 can transmit the reconstructed image and / or the patient information to a display device 232 that is communicatively coupled to the computer 216 and / or the image reconstructor 230.

[0033] A non-transitory computer-readable storage medium included in or in communication with the CT system 10 may store instructions for performing the various methods, steps, and processes described herein. The instructions may be stored in a single storage medium or may be distributed across multiple storage media. Additionally, the instructions may be stored in an external storage device accessible by the CT system. One or more processors included in the CT system 10 perform the various methods, steps, and processes described herein in accordance with the instructions stored in the storage medium.

[0034] The CT system 10 is configured as described above. When the CT system is used for a long period of time, the parts deteriorate over time, and as a result, the characteristics of the parts used in the CT system vary. Therefore, the CT system periodically executes a calibration scan to obtain calibration data for calibrating the variation in the characteristics of the parts.

[0035] FIG. 2 is an explanatory diagram of the calibration.

[0036] In the calibration of the kV switching method, for example, z combinations P1 to Pz of values ​​of three parameters (rotation speed, cone angle, and tube current) are prepared. Then, the z combinations P1 to Pz are preset and stored in the CT system, and a calibration scan is performed for each combination. By performing the calibration scan, X-rays are detected by the detector 108. The processor generates calibration data based on the data of the X-rays detected by the detector 108. FIG. 2 shows an example in which z pieces of calibration data D1 to Dz are generated for z presets P1 to Pz.

[0037] However, as the number of presets increases, the number of calibration scans that must be performed also increases, resulting in a problem that the calibration takes a long time. For example, when three rotation speeds (r1, r2, r3) are considered as the rotation speeds, three cone angles (c1, c2, c3) are considered as the cone angles, and three tube currents (a1, a2, a3) are considered as the tube currents, 27 combinations S1 to S27 are prepared as presets, and a calibration scan is performed for each of the combinations S1 to S27. Therefore, 27 calibration scans must be performed in one calibration, i.e., 27 calibration data must be obtained, resulting in a problem that the time required for the calibration is also long.

[0038] Therefore, the CT system of this embodiment is configured to be able to shorten the time required for one calibration. This embodiment will be described below.

[0039] FIG. 3 is an illustration of the steps performed on clinic day 1.

[0040] In step ST11, calibration is performed. In the calibration, as described with reference to FIG. 2, z pieces of calibration data are generated. However, in the following, in order to facilitate understanding of this embodiment, only three pieces of calibration data D1, D2, and D3 are considered as the calibration data to be generated. The processor stores the generated calibration data D1, D2, and D3 in a storage device. After storing the calibration data D1, D2, and D3, the process proceeds to step ST12.

[0041] In step ST12, the subject is examined.

[0042] An example of imaging that was actually performed in the examination is shown in a chronological order in the box of step ST12. For convenience of explanation, FIG. 3 shows an example in which imaging 1 to imaging 5 were performed.

[0043] For shooting 1 to shooting 5, the calibration data used at the time of shooting and the weighting coefficient k according to the shooting purpose are shown.

[0044] For example, "D1" is written in the box of shooting 1. This means that in shooting 1, the processor selected the calibration data D1 of the calibration data D1 to D3 as the calibration data to be used for image reconstruction. Also, "k=1.5" is written in the box of shooting 1. Here, k represents a weighting coefficient according to the shooting purpose. The weighting coefficient k is a value set for each shooting protocol, and is a value that reflects the shooting purpose. For example, high image quality may be required depending on the shooting purpose, and in this case, the weighting coefficient k is set to a high value. On the other hand, the image quality required depending on the shooting purpose may not be so high, and in this case, the weighting coefficient k is set to a low value. In this embodiment, for convenience of explanation, two values, namely "1.5" and "0.5", are considered as the weighting coefficient k, and the weighting coefficient k is set to 1.5 or 0.5 depending on the shooting purpose. In shooting 1, the weighting coefficient k is k=1.5.

[0045] Referring to the box of Shooting 2, "D2" is written in the box of Shooting 2. This means that in Shooting 2, the processor selected the calibration data D1 of the calibration data D1 to D3 as the calibration data to be used for image reconstruction. Also, "k=1.5" is written in the box of Shooting 2. Therefore, the weighting coefficient k in Shooting 2 is k=1.5.

[0046] Referring to the box of Shooting 3, "D1" is written in the box of Shooting 3. Therefore, the calibration data D1 is selected as the calibration data to be used for image reconstruction. Also, "k=0.5" is written in the box of Shooting 3. Therefore, the weighting coefficient k in Shooting 3 is k=0.5.

[0047] Referring to the box of Shooting 4, "D3" is written in the box of Shooting 4. This means that in Shooting 4, the processor selected the calibration data D3 from the calibration data D1 to D3 as the calibration data to be used for image reconstruction. Also, "k=0.5" is written in the box of Shooting 4. Therefore, the weighting coefficient k in Shooting 4 is k=0.5.

[0048] Referring to the box of Shot 5, "D1" is written in the box of Shot 6. Therefore, the calibration data D1 is selected as the calibration data to be used for image reconstruction. Also, "k=1.5" is written in the box of Shot 5. Therefore, the weighting coefficient k in Shot 5 is k=1.5.

[0049] Each time each of the photographing operations 1 to 5 is performed, the processor considers the usage status of the calibration data used in the photographing and determines the update frequency of each calibration data. The update frequency of the calibration data indicates the degree to which the calibration data is repeatedly updated. For example, in this embodiment, the following three types of update frequency of the calibration data are considered.

[0050] (1) Update the calibration data daily (2) Update the calibration data every other day (3) Update the calibration data every two days Therefore, the processor determines the update frequency (whether to update every day, every other day, or every third day) for each of the calibration data D1, D2, and D3. A method for determining the update frequency of the calibration data will be specifically described below.

[0051] An operator operates the console to input a signal to select a protocol corresponding to the purpose of shooting 1. When this signal is input, the processor selects a protocol corresponding to the purpose of shooting 1 from among a plurality of protocols. A weighting factor corresponding to the purpose of shooting is set for each protocol, and the processor can read out the value of the weighting factor as necessary. After the protocol is selected, shooting 1 is executed as shown in FIG. 4. When shooting 1 is executed, the processor determines the update frequency of the calibration data D1, D2, and D3. A method for determining the update frequency will be described below.

[0052] Fig. 5 is a flow diagram of a method for determining the update frequency of the calibration data D1, D2, and D3 when shooting 1 is performed, and Fig. 6 is a diagram showing a table for explaining each step ST1 to ST4 in Fig. 5. Each step will be explained below.

[0053] (About step ST1) In step ST1, an index value is determined as a reference for determining the update frequency of the calibration data D1. Specifically, the index value is determined as follows.

[0054] In step ST1, first, a score P1 of the calibration data D1 for shooting 1 is determined. If the calibration data D1 is not used in shooting 1, the processor assigns P1=0 to the score P1. On the other hand, if the calibration data D1 is used in shooting 1, the processor assigns the value of the weighting coefficient k set for the selected protocol to the score P1. Since the calibration data D1 is used in shooting 1, the processor assigns the value of the weighting coefficient k to the score P1. In shooting 1, the weighting coefficient k for the shooting purpose is k(=1.5). Therefore, the processor assigns P1=1.5 to the score P1.

[0055] After determining the score P1, the processor determines an index value A1 that is a reference for determining the update frequency of the calibration data D1 based on the score P1. In shooting 1, the value of the score P1 is adopted as the initial value of the index value A1. Therefore, A1=1.5 is determined. After calculating the index value A1, the process proceeds to step ST2.

[0056] (About step ST2) In step ST2, an index value is determined as a reference for determining the update frequency of the calibration data D2. Specifically, the index value is determined as follows.

[0057] In step ST2, first, a score Q1 of the calibration data D2 for shooting 1 is determined. If the calibration data D2 was not used in shooting 1, the processor assigns the score Q1 as Q1=0. On the other hand, if the calibration data D2 was used in shooting 1, the processor assigns the value of the weighting coefficient k to the score Q1. Since the calibration data D2 was not used in shooting 1, the processor assigns the score Q1 as Q1=0.

[0058] After determining the score Q1, the processor determines an index value B1 that is a reference for determining the update frequency of the calibration data D2 based on the score Q1. In shooting 1, the value of the score Q1 is adopted as the initial value of the index value B1. Therefore, it is determined that B1=0. After calculating the index value B1, the process proceeds to step ST3.

[0059] (About step ST3) In step ST3, an index value is determined as a reference for determining the update frequency of the calibration data D3. Specifically, the index value is determined as follows.

[0060] In step ST3, first, a score R1 of the calibration data D3 for shooting 1 is determined. If the calibration data D3 was not used in shooting 1, the processor assigns R1=0 to the score R1. On the other hand, if the calibration data D3 was used in shooting 1, the processor assigns the value of the weighting coefficient k to the score R1. Since the calibration data D3 was not used in shooting 1, the processor assigns R1=0 to the score R1.

[0061] After determining the score R1, the processor determines an index value C1 that is a reference for determining the update frequency of the calibration data D3 based on the score R1. In shooting 1, the value of the score R1 is adopted as the initial value of the index value C1. Therefore, C1=0 is determined.

[0062] Therefore, in shooting 1, the index value A1 = 1.5, the index value B1 = 0, and the index value C1 = 0 are determined. After determining these index values ​​A1, B1, and C1, the process proceeds to step ST4.

[0063] (About step ST4) In step ST4, the processor determines the update frequency of the calibration data D1, D2, and D3 based on the index values ​​A1, B1, and C1. Specifically, the processor determines the update frequency of the calibration data D1, D2, and D3 as follows.

[0064] First, the processor calculates the ratio L (%) of each index value to the total value of the index values ​​A1, B1, and C1. Here, since the index value A1=1.5, the index value B1=0, and the index value C1=0, the total value of the index values ​​is 1.5. Therefore, the ratio L of each index value is 100% for the index value A1, and 0% for the index values ​​B1 and C1. Then, the processor compares the ratio of each index value with a threshold value. In this embodiment, two threshold values ​​are considered as the threshold value, that is, a threshold value TH1 and a threshold value TH2 smaller than the threshold value TH1. In the following, for convenience of explanation, the threshold value TH1=60% and the threshold value TH2=20%. Then, the processor determines which of the following conditions 1 to 3 the ratio P of each index value satisfies with respect to the threshold value TH1 and the threshold value TH2.

[0065] (Condition 1) P≧TH1, i.e., P≧60% (Condition 2) TH1>P≧TH2, i.e., 60%>P≧20% (Condition 3) TH2>P, i.e., 20%>P If condition 1 is met, the processor determines to update the calibration data every day; if condition 2 is met, the processor determines to update the calibration data every other day; and if condition 3 is met, the processor determines to update the calibration data every two days.

[0066] Here, the proportion L of the index value A1 is L = 100%. Therefore, the proportion L of the index value A1 satisfies condition 1, and the processor determines that the calibration data D1 is to be updated every day.

[0067] On the other hand, the ratio L of the index values ​​B1 and C1 is L=0%. Therefore, the ratio L of the index values ​​B1 and C1 satisfies condition 3, so the processor determines that the calibration data D2 and D3 are to be updated every two days. After determining the update frequency, the flow of FIG. 5 is terminated.

[0068] After determining the update frequency, the processor stores in the storage device the index value and the update frequency calculated by the flow of Fig. 5. Fig. 7 shows the index values ​​and update frequencies of the calibration data D1, D2, and D3 stored in association with the shooting 1.

[0069] Next, the operator operates the console to input a signal to select a protocol corresponding to the purpose of shooting 2. When this signal is input, the processor selects a protocol corresponding to the purpose of shooting 2 from among a plurality of protocols. After the protocol is selected, shooting 2 is executed as shown in FIG. 8. When shooting 2 is executed, the processor determines the update frequency of the calibration data D1, D2, and D3. A method of determining the update frequency will be described below with reference to FIG. 9 along with the flow of FIG. 5.

[0070] Fig. 9 is a table for explaining each step in Fig. 5 when shooting 2 is performed. Note that Fig. 9 shows not only the table for shooting 2 but also the table for shooting 1.

[0071] (About step ST1) In step ST1, an index value is determined as a reference for determining the update frequency of the calibration data D1. Specifically, the index value is determined as follows.

[0072] In step ST1, first, a score P2 of the calibration data D1 for shooting 2 is determined. If the calibration data D1 is not used in shooting 2, the processor assigns P2=0 to the score P2. On the other hand, if the calibration data D1 is used in shooting 2, the processor assigns the value of the weighting coefficient k to the score P2. Since the calibration data D1 is not used in shooting 2, the processor assigns P2=0 to the score P2.

[0073] After determining the score P2, the processor determines an index value A2 that is a criterion for determining the update frequency of the calibration data D1 based on the score P2. Specifically, the processor calculates the index value A2 (=A1+P2) by adding the score P2 to the index value A1 determined in the shooting 1. A2 is a value expressed by the following formula.

[0074] A2=A1+P2 =1.5+0 =1.5 Therefore, the index value A2 is calculated as A2 = 1.5 After calculating the index value A2, the process proceeds to step ST2.

[0075] (About step ST2) In step ST2, an index value is determined as a reference for determining the update frequency of the calibration data D2. Specifically, the index value is determined as follows.

[0076] In step ST2, first, a score Q2 of the calibration data D2 for shooting 2 is determined. If the calibration data D2 is not used in shooting 2, the processor assigns the score Q2 as Q2=0. On the other hand, if the calibration data D2 is used in shooting 2, the processor assigns the value of the weighting coefficient k to the score Q2. Since the calibration data D2 is used in shooting 2, the processor assigns the value of the weighting coefficient k to the score Q2. In shooting 2, the weighting coefficient k for the shooting purpose is k(=1.5). Therefore, the processor assigns the score Q2 as Q2=1.5.

[0077] After determining the score Q2, the processor determines an index value B2 that is a criterion for determining the update frequency of the calibration data D2 based on the score Q2. Specifically, the processor calculates the index value B2 (=B1+Q2) by adding the score Q2 to the index value B1 determined in the shooting 1. B2 is a value expressed by the following formula.

[0078] B2=B1+Q2 =1.5+0 =1.5 Therefore, the index value B2 is calculated as B2 = 1.5 After calculating the index value B2, the process proceeds to step ST3.

[0079] (About step ST3) In step ST3, the processor determines an index value that is a criterion for determining the update frequency of the calibration data D3. Specifically, the processor determines the index value as follows.

[0080] In step ST3, the processor determines a score R2. If the calibration data D3 was not used in shooting 2, the processor assigns the score R2 as R2=0. On the other hand, if the calibration data D3 was used in shooting 2, the processor assigns the value of the weighting coefficient to the score R2. Since the calibration data D3 was not used in shooting 2, the processor determines the score R2 as R2=0.

[0081] After determining the score R2, the processor determines an index value C2 that is a reference for determining the update frequency of the calibration data D3 based on the score R2. Specifically, the processor adds the score R2 to the index value C1 determined in the shooting 1 to calculate the index value C2 (=C1+R2). C2 is a value expressed by the following formula.

[0082] C2=C1+R2 =0+0 =0 Therefore, the index value C2 is calculated as C2=0.

[0083] Therefore, when shooting 2 is completed, the latest index values ​​are determined to be A2=1.5, B2=1.5, and C2=0. After determining these index values ​​A2, B2, and C2, the process proceeds to step ST4.

[0084] (About step ST4) In step ST4, the processor determines the update frequency of the calibration data D1, D2, and D3 based on the index values ​​A2, B2, and C2. Specifically, the processor determines the update frequency of the calibration data D1, D2, and D3 as follows.

[0085] First, the processor calculates the ratio L (%) of each index value to the total value of index values ​​A2, B2, and C2. Here, index value A2=1.5, index value B2=1.5, and index value C2=0, so the total value of the index values ​​is 3.0. Therefore, the ratio L of each index value is 50% for index value A2, 50% for index value B2, and 0% for index value C2. Then, the processor compares the ratio of each index value with a threshold value, and determines which of conditions 1 to 3 the ratio P of each index value satisfies with respect to threshold values ​​TH1 and TH2.

[0086] Here, the proportion L of the index value A2 is L = 50%. Therefore, the proportion L of the index value A2 satisfies condition 2, and the processor determines that the calibration data D1 should be updated every other day.

[0087] Furthermore, the proportion L of the index value B2 is L = 50%. Therefore, the proportion L of the index value B2 satisfies condition 2, and the processor determines that the calibration data D2 should be updated every other day.

[0088] Furthermore, the proportion L of the index value C2 is L=0%. Therefore, the proportion L of the index value B2 satisfies condition 3, so the processor determines that the calibration data D2 is to be updated every two days. After determining the update frequency, the flow of FIG. 5 is terminated.

[0089] After determining the update frequency, the processor stores in the storage device the index values ​​and update frequencies calculated by the flow in Fig. 5. Fig. 10 shows the index values ​​and update frequencies of the calibration data D1, D2, and D3 stored in association with Shooting 2. Note that the index values ​​and update frequencies obtained in the previous Shooting 1 are discarded as they are old information.

[0090] Next, the operator operates the console to input a signal to select a protocol corresponding to the purpose of shooting 3. When this signal is input, the processor selects a protocol corresponding to the purpose of shooting 3 from among a plurality of protocols. After the protocol is selected, shooting 3 is executed as shown in FIG. 11. When shooting 3 is executed, the processor determines the update frequency of the calibration data D1, D2, and D3. A method of determining the update frequency will be described below with reference to FIG. 12 along with the flow of FIG. 5.

[0091] Fig. 12 is a diagram showing a table for explaining each step in Fig. 5 when photographing 3 is performed. Note that Fig. 12 shows not only the table for photographing 3 but also the table for photographing 2.

[0092] (About step ST1) In step ST1, an index value is determined as a reference for determining the update frequency of the calibration data D1. Specifically, the index value is determined as follows.

[0093] In step ST1, first, a score P3 of the calibration data D1 for shooting 3 is determined. If the calibration data D1 is not used in shooting 3, the processor assigns P3=0 to the score P3. On the other hand, if the calibration data D1 is used in shooting 3, the processor assigns the value of the weighting coefficient k to the score P3. Since the calibration data D1 is used in shooting 3, the processor assigns the value of the weighting coefficient k to the score P3. In shooting 3, the weighting coefficient k for the shooting purpose is k(=0.5). Therefore, the processor assigns P3=0.5 to the score P3.

[0094] After determining the score P3, the processor determines an index value A3 that is a criterion for determining the update frequency of the calibration data D1 based on the score P3. Specifically, the processor calculates the index value A3 (=A2+P3) by adding the score P3 to the index value A2 determined in the photograph 2. A3 is a value expressed by the following formula.

[0095] A3=A2+P3 =1.5+0.5 =2.0 Therefore, the index value A3 is calculated as A3 = 2.0 After calculating the index value A3, the process proceeds to step ST2.

[0096] (About step ST2) In step ST2, an index value is determined as a reference for determining the update frequency of the calibration data D2. Specifically, the index value is determined as follows.

[0097] In step ST2, first, a score Q3 of the calibration data D2 for shooting 3 is determined. If the calibration data D2 is not used in shooting 3, the processor assigns the score Q3 as Q3=0. On the other hand, if the calibration data D2 is used in shooting 3, the processor assigns the value of the weighting coefficient k to the score Q3. Since the calibration data D2 is not used in shooting 3, the processor assigns the score Q3 as Q3=0.

[0098] After determining the score Q3, the processor determines an index value B3 that is a criterion for determining the update frequency of the calibration data D3 based on the score Q3. Specifically, the processor calculates the index value B3 (=B2+Q3) by adding the score Q3 to the index value B2 determined in the photograph 2. B3 is a value expressed by the following formula.

[0099] B3=B2+Q3 =1.5+0 =1.5 Therefore, the index value B3 is calculated as B3 = 1.5 After calculating the index value B3, the process proceeds to step ST3.

[0100] (About step ST3) In step ST3, the processor determines an index value that is a criterion for determining the update frequency of the calibration data D3. Specifically, the processor determines the index value as follows.

[0101] In step ST3, the processor determines a score R3. If the calibration data D3 was not used in shooting 3, the processor assigns the score R3 as R3=0. On the other hand, if the calibration data D3 was used in shooting 3, the processor assigns the value of a weighting coefficient to the score R3. Since the calibration data D3 was not used in shooting 3, the processor determines the score R3 as R3=0.

[0102] After determining the score R3, the processor determines an index value C3 that is a reference for determining the update frequency of the calibration data D3 based on the score R3. Specifically, the processor calculates the index value C3 (=C2+R3) by adding the score R3 to the index value C2 determined in the photograph 2. C3 is a value expressed by the following formula.

[0103] C3=C2+R3 =0+0 =0 Therefore, the index value C3 is determined to be C3=0.

[0104] Therefore, when shooting 3 is completed, the latest index values ​​are determined to be A3=2.0, B3=1.5, and C3=0. After determining these index values ​​A3, B3, and C3, the process proceeds to step ST4.

[0105] (About step ST4) In step ST4, the processor determines the update frequency of the calibration data D1, D2, and D3 based on the index values ​​A3, B3, and C3. Specifically, the processor determines the update frequency of the calibration data D1, D2, and D3 as follows.

[0106] First, the processor calculates the ratio L (%) of each index value to the total value of index values ​​A3, B3, and C3. Here, index value A3=2.0, index value B3=1.5, and index value C2=0, so the total value of the index values ​​is 3.5. Therefore, the ratio L of each index value is 57% for index value A3, 43% for index value B3, and 0% for index value C3. Then, the processor compares the ratio of each index value with a threshold value, and determines which of conditions 1 to 3 the ratio P of each index value satisfies with respect to threshold value TH1 and threshold value TH2.

[0107] Here, the proportion L of the index value A3 is L = 57%. Therefore, the proportion L of the index value A3 satisfies condition 2, and the processor determines that the calibration data D1 should be updated every other day.

[0108] Furthermore, the proportion L of the index value B3 is L = 43%. Therefore, the proportion L of the index value B3 satisfies condition 2, and the processor determines that the calibration data D2 should be updated every other day.

[0109] Furthermore, the proportion L of the index value C3 is L=0%. Therefore, the proportion L of the index value C3 satisfies condition 3, so the processor determines that the calibration data D3 is to be updated every two days. After determining the update frequency, the flow of FIG. 5 ends.

[0110] After determining the update frequency, the processor stores in the storage device the index values ​​and update frequencies calculated by the flow in Fig. 5. Fig. 13 shows the index values ​​and update frequencies of the calibration data D1, D2, and D3 stored in association with Shooting 3. Note that the index values ​​and update frequencies obtained in the previous Shooting 2 are discarded as they are old information.

[0111] Next, the operator operates the console to input a signal to select a protocol corresponding to the purpose of shooting 4. When this signal is input, the processor selects a protocol corresponding to the purpose of shooting 4 from among a plurality of protocols. After the protocol is selected, shooting 4 is executed as shown in FIG. 14. When shooting 4 is executed, the processor determines the update frequency of the calibration data D1, D2, and D3. A method of determining the update frequency will be described below with reference to FIG. 15 along with the flow of FIG. 5.

[0112] Fig. 15 is a diagram showing a table for explaining each step in Fig. 5 when shooting 4 is performed. Note that Fig. 14 shows not only the table for shooting 4 but also the table for shooting 3.

[0113] (About step ST1) In step ST1, an index value is determined as a reference for determining the update frequency of the calibration data D1. Specifically, the index value is determined as follows.

[0114] In step ST1, first, a score P4 of the calibration data D1 for Shooting 4 is determined. If the calibration data D1 is not used in Shooting 4, the processor assigns P4=0 to the score P4. On the other hand, if the calibration data D1 is used in Shooting 4, the processor assigns the value of the weighting coefficient k to the score P4. Since the calibration data D1 is not used in Shooting 4, the processor assigns P4=0 to the score P4.

[0115] After determining the score P4, the processor determines an index value A4 that is a criterion for determining the update frequency of the calibration data D1 based on the score P4. Specifically, the processor calculates the index value A4 (=A3+P4) by adding the score P4 to the index value A3 determined in the previous shooting 3. Therefore, A4 is expressed by the following formula.

[0116] A4=A3+P4 =2.0+0 =2.0 Therefore, the index value A4 is calculated as A4 = 2.0 After calculating the index value A4, the process proceeds to step ST2.

[0117] (About step ST2) In step ST2, an index value is determined as a reference for determining the update frequency of the calibration data D2. Specifically, the index value is determined as follows.

[0118] In step ST2, first, a score Q4 of the calibration data D2 for Shooting 4 is determined. If the calibration data D2 is not used in Shooting 4, the processor assigns the score Q4 as Q4=0. On the other hand, if the calibration data D2 is used in Shooting 4, the processor assigns the value of the weighting coefficient k to the score Q4. Since the calibration data D2 is not used in Shooting 4, the processor assigns the score Q4 as Q4=0.

[0119] After determining the score Q4, the processor determines an index value B4 that is a reference for determining the update frequency of the calibration data D3 based on the score Q4. Specifically, the processor calculates the index value B4 (=B3+Q4) by adding the score Q4 to the index value B3 determined in the photograph 3. B4 is expressed by the following formula.

[0120] B4=B3+Q4 =1.5+0 =1.5 Therefore, the index value B4 is calculated as B4 = 1.5 After calculating the index value B4, the process proceeds to step ST3.

[0121] (About step ST3) In step ST3, the processor determines an index value that is a criterion for determining the update frequency of the calibration data D3. Specifically, the processor determines the index value as follows.

[0122] In step ST3, the processor determines a score R4. If the calibration data D3 is not used in shooting 4, the processor assigns R4=0 to the score R4. On the other hand, if the calibration data D3 is used in shooting 4, the processor assigns the value of the weighting coefficient to the score R4. Since the calibration data D3 is used in shooting 4, the processor assigns the value of the weighting coefficient k to the score R4. In shooting 4, the weighting coefficient k for the shooting purpose is k(=0.5). Therefore, the processor assigns R4=0.5 to the score R4.

[0123] After determining the score R4, the processor determines an index value C4 that is a reference for determining the update frequency of the calibration data D3 based on the score R4. Specifically, the processor calculates the index value C4 (=C3+R4) by adding the score R4 to the index value C3 determined in the photograph 3. C4 is a value expressed by the following formula.

[0124] C4=C3+R4 =0+0.5 =0.5 Therefore, the index value C4 is determined to be C4=0.5.

[0125] Therefore, when shooting 4 is completed, the latest index values ​​are determined to be A4=2.0, B4=1.5, and C4=0.5. After determining these index values ​​A4, B4, and C4, the process proceeds to step ST4.

[0126] (About step ST4) In step ST4, the processor determines the update frequency of the calibration data D1, D2, and D3 based on the index values ​​A4, B4, and C4. Specifically, the processor determines the update frequency of the calibration data D1, D2, and D3 as follows.

[0127] First, the processor calculates the ratio L (%) of each index value to the total value of index values ​​A4, B4, and C4. Here, index value A4=2.0, index value B4=1.5, and index value C4=0.5, so the total value of the index values ​​is 4.0. Therefore, the ratio L of each index value is 50% for index value A4, 37% for index value B4, and 13% for index value C4. Then, the processor compares the ratio of each index value with a threshold value, and determines which of conditions 1 to 3 the ratio L of each index value satisfies with respect to threshold value TH1 and threshold value TH2.

[0128] Here, the proportion L of the index value Ae is L = 50%. Therefore, the proportion L of the index value A4 satisfies condition 2, so the processor determines that the calibration data D1 will be updated every other day.

[0129] Furthermore, the proportion L of the index value B4 is L = 37%. Therefore, the proportion L of the index value B4 satisfies condition 2, and the processor determines that the calibration data D2 should be updated every other day.

[0130] Furthermore, the proportion L of the index value C4 is L=3%. Therefore, the proportion L of the index value C4 satisfies condition 3, so the processor determines that the calibration data D3 should be updated every two days. After determining the update frequency, the flow of FIG. 5 ends.

[0131] After determining the update frequency, the processor stores in the storage device the index values ​​and update frequencies calculated by the flow in Fig. 5. Fig. 16 shows the index values ​​and update frequencies of the calibration data D1, D2, and D3 stored in association with Shooting 4. Note that the index values ​​and update frequencies obtained in the previous Shooting 3 are discarded as they are old information.

[0132] Next, the operator operates the console to input a signal to select a protocol corresponding to the purpose of shooting 5. When this signal is input, the processor selects a protocol corresponding to the purpose of shooting 5 from among a plurality of protocols. After the protocol is selected, shooting 5 is executed as shown in FIG. 17. When shooting 5 is executed, the processor determines the update frequency of the calibration data D1, D2, and D3. A method of determining the update frequency will be described below with reference to FIG. 18 along with the flow of FIG. 5.

[0133] Fig. 18 is a diagram showing a table for explaining each step in Fig. 5 when photographing 5 is performed. Note that Fig. 18 shows not only the table for photographing 5 but also the table for photographing 4.

[0134] FIG. 18 shows the update frequencies determined by executing steps ST1 to ST4 for shooting 5. The method of determining the update frequencies is as described above, so the description of FIG. 18 is omitted. For shooting 5, it is determined that the calibration data D1 is updated every day, the calibration data D2 is updated every other day, and the calibration data D3 is updated every third day. The processor saves the index values ​​A5, B5, and C5 obtained for shooting 5 and the update frequencies "every day", "every other day", and "every third day" in the storage device. FIG. 19 shows the index values ​​and update frequencies of the calibration data D1, D2, and D3 saved in association with shooting 5. The index values ​​and update frequencies obtained in the previous shooting 4 are discarded because they are old information.

[0135] Therefore, on clinic day 1, the latest index values ​​of calibration data D1, D2, and D3 are A5=3.5, B5=1.5, and Cg=0.5, respectively, and the latest update frequencies are determined to be “every day,” “every other day,” and “every third day,” respectively.

[0136] Next, treatment day 2 will be described.

[0137] FIG. 20 is an explanatory diagram of treatment day 2.

[0138] For clinic day 1, the latest index values ​​A5=3.5, B5=1.5, and Cg=0.5 obtained in capture 5 for calibration data D1, D2, and D3 are shown, along with the latest update frequencies of “daily,” “every other day,” and “every third day.”

[0139] On consultation day 2, in step ST21, the operator operates the console to input a command to execute calibration. When this command is input, the processor reads out the latest update frequency stored in the storage device. Here, the latest update frequency of the calibration data D1 is determined to be "every day." Therefore, the processor determines to update the calibration data D1 also on consultation day 2. Therefore, the processor determines to execute a calibration scan to obtain the calibration data D1.

[0140] In addition, the latest update frequency of the calibration data D2 is determined to be "every other day." Therefore, the processor checks the past update history of the calibration data D2. In this embodiment, the calibration data D2 was acquired on the consultation day 1, and therefore the calibration data D2 was updated on the day before the consultation day 2 (the consultation day 1). Therefore, the processor determines that the calibration data D2 will not be updated on the consultation day 2. For this reason, the processor decides not to execute a calibration scan to acquire the calibration data D2.

[0141] Also, the latest update frequency of the calibration data D3 is determined to be "every two days." Therefore, the processor checks the past update history of the calibration data D3. In this embodiment, the calibration data D3 was acquired on clinic day 1, and therefore the calibration data D3 was updated on the day before clinic day 2 (clinic day 1). Therefore, the processor determines that the calibration data D3 will not be updated on clinic day 2. For this reason, the processor decides not to execute a calibration scan to acquire the calibration data D3.

[0142] As a result, the processor determines to execute only the calibration scan to obtain the calibration data D1 on the medical treatment day 2. Therefore, in step ST21, only the calibration data D1 is obtained.

[0143] After the calibration data D1 is acquired, imaging of the subject is performed in step ST22.

[0144] FIG. 21 is an explanatory diagram of step ST22.

[0145] In step ST22, the operator operates the console to input a signal for selecting a protocol corresponding to the purpose of shooting 6. When this signal is input, the processor selects a protocol corresponding to the purpose of shooting 6 from among a plurality of protocols. After the protocol is selected, shooting 6 is performed. When shooting 6 is performed, the processor determines the update frequency of the calibration data D1, D2, and D3. A method for determining the update frequency will be described below with reference to FIG. 22 along with the flow of FIG. 5.

[0146] Fig. 22 is a diagram showing a table for explaining each step in Fig. 5 when imaging 6 is performed. Note that Fig. 22 shows not only the table for imaging 6, but also the table for imaging 5, which is the last imaging on consultation day 1.

[0147] (About step ST1) In step ST1, an index value is determined as a reference for determining the update frequency of the calibration data D1. Specifically, the index value is determined as follows.

[0148] In step ST1, first, a score P6 of the calibration data D1 for Shooting 6 is determined. If the calibration data D1 is not used in Shooting 6, the processor assigns P6=0 to the score P6. On the other hand, if the calibration data D1 is used in Shooting 6, the processor assigns the value of weighting coefficient k to the score P6. Since the calibration data D1 is used in Shooting 6, the processor assigns the value of weighting coefficient k to the score P6. In Shooting 6, the weighting coefficient k for the shooting purpose is k(=1.5). Therefore, the processor assigns P6=1.5 to the score P6.

[0149] After determining the score P6, the processor determines an index value A6 that is a criterion for determining the update frequency of the calibration data D1 based on the score P6. Specifically, the processor calculates the index value A6 (=A5+P6) by adding the score P6 to the index value A5 determined in the photographing 5. A6 is a value expressed by the following formula.

[0150] A6=A5+P6 =3.5+1.5 =5.0 Therefore, the index value A6 is calculated as A6 = 5.0 After calculating the index value A6, the process proceeds to step ST2.

[0151] (About step ST2) In step ST2, an index value is determined as a reference for determining the update frequency of the calibration data D2. Specifically, the index value is determined as follows.

[0152] In step ST2, first, a score Q6 of the calibration data D2 for Shooting 6 is determined. If the calibration data D2 was not used in Shooting 6, the processor assigns the score Q6 as Q6=0. On the other hand, if the calibration data D2 was used in Shooting 6, the processor assigns the value of the weighting coefficient k to the score Q6. Since the calibration data D2 was not used in Shooting 6, the processor assigns the score Q6 as Q6=0.

[0153] After determining the score Q6, the processor determines an index value B6 that is a reference for determining the update frequency of the calibration data D3 based on the score Q6. Specifically, the processor calculates the index value B6 (=B5+Q6) by adding the score Q6 to the index value B5 determined in the photograph 5. B6 is a value expressed by the following formula.

[0154] B6=B5+Q6 =1.5+0 =1.5 Therefore, the index value B6 is calculated as B6 = 1.5 After calculating the index value B6, the process proceeds to step ST3.

[0155] (About step ST3) In step ST3, the processor determines an index value that is a criterion for determining the update frequency of the calibration data D3. Specifically, the processor determines the index value as follows.

[0156] In step ST3, the processor determines a score R6. If the calibration data D3 was not used in shooting 6, the processor assigns the score R6 as R6=0. On the other hand, if the calibration data D3 was used in shooting 6, the processor assigns the value of the weighting coefficient to the score R6. Since the calibration data D3 was not used in shooting 6, the processor determines the score R6 as R6=0.

[0157] After determining the score R6, the processor determines an index value C6 that is a reference for determining the update frequency of the calibration data D3 based on the score R6. Specifically, the processor calculates the index value C6 (=C5+R6) by adding the score R6 to the index value C5 determined in the photograph 5. C6 is a value expressed by the following formula.

[0158] C6=C5+R6 =0.5+0 =0 Therefore, in shooting 6, the index value A6=5.0, the index value B6=1.5, and the index value C6=0.5 are determined. After determining these index values ​​A6, B6, and C6, the process proceeds to step ST4.

[0159] (About step ST4) In step ST4, the processor determines the update frequency of the calibration data D1, D2, and D3 based on the index values ​​A6, B6, and C6. Specifically, the processor determines the update frequency of the calibration data D1, D2, and D3 as follows.

[0160] First, the processor calculates the ratio L (%) of each index value to the total value of index values ​​A6, B6, and C6. Here, index value A6=5.0, index value B6=1.5, and index value C5=0.5, so the total value of the index values ​​is 7.0. Therefore, the ratio L of each index value is 70% for index value A6, 21% for index value B6, and 9% for index value C6. Then, the processor compares the ratio of each index value with a threshold value, and determines which of conditions 1 to 3 the ratio P of each index value satisfies with respect to threshold value TH1 and threshold value TH2.

[0161] Here, the proportion L of the index value A6 is L = 70%. Therefore, the proportion L of the index value A6 satisfies condition 1, and the processor determines that the calibration data D1 is to be updated every day.

[0162] Furthermore, the proportion L of the index value B6 is L = 21%. Therefore, the proportion L of the index value B6 satisfies condition 2, and the processor determines that the calibration data D2 should be updated every other day.

[0163] Furthermore, the proportion L of the index value C6 is L=9%. Therefore, the proportion L of the index value C6 satisfies condition 3, so the processor determines that the calibration data D3 should be updated every two days. After determining the update frequency, the flow of FIG. 5 ends.

[0164] After determining the update frequency, the processor stores in the storage device the index values ​​and update frequencies calculated by the flow in Fig. 5. Fig. 23 shows the index values ​​and update frequencies of the calibration data D1, D2, and D3 stored in association with the photograph 6. Note that the index values ​​and update frequencies obtained in the previous photograph 5 are discarded as they are old information.

[0165] Similarly, the flow of FIG. 5 is executed every time the next photographing is waited for, and the update frequency is determined.

[0166] 24 is a diagram showing the index values ​​and update frequencies obtained in the last shooting p on clinic day 2. On clinic day 2, the latest index values ​​of calibration data D1, D2, and D3 are Ap=15, Bp=6, and Cp=2, respectively, and the latest update frequencies are determined to be "every day," "every other day," and "every third day," respectively.

[0167] Next, treatment day 3 will be described.

[0168] FIG. 25 is an explanatory diagram of treatment day 3.

[0169] For clinic day 2, the latest index values ​​Ap=15, Bp=6, and Cp=2 obtained at imaging p for calibration data D1, D2, and D3, as well as the latest update frequencies “daily,” “every other day,” and “every third day” are shown.

[0170] On consultation day 3, in step ST31, the operator operates the console to input a command to execute calibration. When this command is input, the processor reads out the latest update frequency stored in the storage device. Here, the latest update frequency of the calibration data D1 is determined to be "every day." Therefore, the processor determines to update the calibration data D1 also on consultation day 3. Therefore, the processor determines to execute a calibration scan to obtain the calibration data D1.

[0171] In addition, the latest update frequency of the calibration data D2 is determined to be "every other day." Therefore, the processor checks the past update history of the calibration data D2. In this embodiment, the calibration data D2 was obtained on the consultation day 1, but was not obtained on the consultation day 2. Therefore, the processor determines that the calibration data D2 should be updated on the consultation day 3. Therefore, the processor decides to execute a calibration scan to obtain the calibration data D2.

[0172] Also, the latest update frequency of the calibration data D3 is determined to be "every two days." Therefore, the processor checks the past update history of the calibration data D3. In this embodiment, the calibration data D3 was obtained on clinic day 1, but was not obtained on clinic day 2. Therefore, the processor determines not to update the calibration data D3 on clinic day 3. For this reason, the processor decides not to perform a calibration scan to obtain the calibration data D3.

[0173] As a result, on medical examination day 3, the processor determines to execute only a calibration scan for acquiring calibration data D1 and a calibration scan for acquiring calibration data D2. Therefore, in step ST31, only the calibration data D1 and D2 are acquired.

[0174] After acquiring the calibration data D1 and D2, imaging of the subject is performed in the same manner thereafter, and the update frequency of the calibration data is determined every time imaging of the subject is performed.

[0175] In this embodiment, when determining the update frequency, the processor assigns a weighting factor k to the score for the calibration data used during imaging, and assigns zero to the score for the calibration data not used during imaging. Then, the score and the index value obtained in the previous imaging are added to calculate the latest index value, and the update frequency is determined for each calibration data based on the latest index value. Therefore, an index value reflecting the number of times the calibration data is used can be calculated every time imaging is performed. Also, in this embodiment, the weighting factor k assigned to the score differs depending on the imaging purpose. Therefore, an index value reflecting the weighting factor k can be calculated every time imaging is performed. That is, in this embodiment, the update frequency of the calibration data is determined not only by focusing on the number of times the calibration data is used, but by considering both the number of times the calibration data is used and the weighting factor k. Therefore, when the number of times the calibration data is used and the weighting factor k of the imaging in which the calibration data is used are low, the update frequency of the calibration data is low, and the time required for one calibration of the CT system can be shortened.

[0176] In addition, in this embodiment, as described above, the purpose of imaging can be reflected in the update frequency of the calibration data. For example, in imaging that requires high image quality, such as imaging to obtain images of three time phases of the liver, the weighting coefficient k can be set to a high value, and in imaging that requires a less high image quality, such as imaging to obtain a blood vessel image, the weighting coefficient k can be set to a low value. Therefore, in imaging that requires high image quality, the update frequency of the calibration data can be increased, and in imaging that requires a less high image quality, the update frequency of the calibration data can be decreased, so that the update frequency can be determined in consideration of the balance between the time required for calibration and the required image quality.

[0177] Furthermore, even if photography requiring high image quality is not performed frequently, the weighting coefficient k can be set to a high value to increase the frequency of updating the calibration data, thereby maintaining high image quality.

[0178] Furthermore, in photography requiring a low image quality, such as photography for acquiring a blood vessel image, the weighting coefficient k is set to a low value. However, in this embodiment, as described above, when determining the update frequency of the calibration data, the number of times the calibration data is used is also taken into consideration. Therefore, even in photography requiring a low image quality, if the demand for photography is high, the update frequency of the calibration data can be increased.

[0179] In this embodiment, when the calibration data is not used in the shooting, zero is assigned to the score, but a value other than zero may be assigned. Also, when the calibration data is used in the shooting, the value of the weighting coefficient k is assigned to the score, but the value of the weighting coefficient k does not necessarily have to be assigned to the score as long as it reflects the value of the weighting coefficient k. For example, a multiple of the weighting coefficient k may be used as the score value.

[0180] In addition, in this embodiment, the update frequency of the calibration data is "every day," "every other day," or "every two days," but the update frequency is not limited to "every day," "every other day," or "every two days." For example, the update frequency can also be "half a day," "every three days," or the like.

[0181] In this embodiment, an example is shown in which the CT system 10 is used as a medical system. However, the present invention is not limited to the CT system 10, and can be applied to systems other than the CT system 10 (e.g., a PET-CT system) as long as the medical system irradiates an X-ray source onto a subject 112. [Explanation of symbols]

[0182] 10 CT system 102 Gantry 103 Filter section 104 X-ray Generator 104A X-ray tube 104B Generator 105 Collimator 106 X-ray 107 Bore 108 Detector 112 Subject 116 Table 118 Table Motor Controller 202 Detector element 210 X-ray controller 212 Gantry motor controller 214 DAS 216 Computer 218 Storage device 220 Operator Console 224 PACS 230 Image Reconstructor 232 Display device

Claims

1. A medical system that performs imaging to obtain a medical image of a subject, The medical system includes one or more processors; The one or more processors: selecting calibration data to be used for reconstructing an image from among the plurality of calibration data each time imaging is performed; Determining the update frequency of each calibration data based on the number of times each calibration data is used and a weighting factor according to the photographing purpose of the photographing performed. A medical system that performs the above.

2. The one or more processors: The medical system according to claim 1 , wherein an update frequency for each calibration data is determined each time imaging is performed.

3. The one or more processors:

3. The medical system according to claim 2, wherein an index value reflecting the number of times the calibration data has been used and a weighting coefficient according to the purpose of imaging the subject is calculated for each calibration data each time imaging is performed.

4. The one or more processors: determining a score for each calibration data each time a photograph is taken; The medical system of claim 3 , further comprising: a step of calculating the index value based on the score.

5. The one or more processors: assigning to the score a first value responsive to a weighting factor when the calibration data is used to reconstruct an image; assigning a second value to the score if the calibration data has not been used to reconstruct an image. The medical system of claim 4 .

6. The medical system of claim 5 , wherein the first value is a weighting factor value and the second value is zero.

7. The one or more processors, when one imaging is performed, determining a first score for each of the calibration data; calculating a first index value reflecting the number of times the calibration data has been used and a weighting coefficient for each calibration data based on the first score; and determining a first update frequency for each calibration data item based on the first index value; Run When a next photographing operation is performed after the one photographing operation, determining a second score for each of the calibration data; calculating, for each calibration data item, a second index value reflecting a number of times the calibration data item has been used and a weighting coefficient based on the second score and the first index value; and determining a second update frequency for each calibration data item based on the second index value; The medical system of claim 4 .

8. The one or more processors: The medical system of claim 7 , wherein when the second index value and the second update frequency are determined, the second index value and the second update frequency are stored and the first index value and the first update frequency are discarded.

9. The one or more processors: The medical system of claim 7 , wherein the second index value is calculated by adding the second score and the first index value.

10. A storage device of the medical system or a storage device accessible by the medical system stores a plurality of calibration data obtained by a plurality of calibration scans; The one or more processors: The medical system according to claim 1 , further comprising: determining an update frequency for each of the plurality of calibration data.

11. The one or more processors: Selecting a protocol corresponding to an imaging purpose from among a plurality of protocols based on a signal input from a console; The medical system according to claim 1 , wherein a weighting factor corresponding to an imaging purpose is set for each protocol.

12. The medical system according to claim 1 , wherein the calibration data is acquired by performing a calibration scan in which a tube voltage applied to an X-ray tube is switched between a first tube voltage and a second tube voltage.

13. a latest update frequency of each calibration data is stored in a storage device of the medical system or in a storage device accessible by the medical system; The one or more processors: The medical system according to claim 1 , wherein when a command to execute calibration is input from a console, it is determined whether or not to update each calibration data based on the latest update frequency stored in the storage device.

14. 1. A non-transitory computer readable storage medium included in or in communication with a medical system, comprising: The instructions stored on the storage medium, when executed by one or more processors included in the medical system, cause the one or more processors to: selecting calibration data to be used for reconstructing an image from among the plurality of calibration data each time imaging is performed; Determining the update frequency of each calibration data based on the number of times each calibration data is used and a weighting factor according to the photographing purpose of the photographing performed. A non-transitory computer-readable storage medium for causing the computer to execute

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