Medical system and recording medium

Abstract

To provide techniques capable of shortening a time required for calibration.SOLUTION: A medical system is a CT system for performing imaging to obtain CT images of a subject, the CT system including one or a plurality of processors, the one or plurality of processors performing, each time imaging is performed, selection of a calibration dataset to be used to reconstruct an image from a plurality of calibration datasets C1 to C3, and determination of an update frequency of each calibration dataset based on both the number of times each calibration dataset is used and a weighting coefficient according to an imaging purpose of the executed imaging.SELECTED DRAWING: Figure 19

Description

[Technical Field]

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

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

[0003] A CT system applies a predetermined 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 generating X-rays by applying a predetermined voltage (e.g., 120 kV) to the cathode-anode tube of an X-ray tube, thereby obtaining a CT image of the subject. However, with SECT, different substances can have similar CT values, making it difficult to identify the different substances.

[0006] Therefore, research and development has been conducted on DECT (Dual Energy CT) technology. 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, so it is beginning to be widely used. DECT technology is known for its kV switching technology, 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 time as it is used for a long period of time, and as a result, the calibration data used to calibrate the CT system deviates from the ideal values. Therefore, CT systems perform calibration scans periodically to obtain the calibration data necessary to calibrate the CT system.

[0008] For example, the material decomposition accuracy of kV switching by DECT depends on the gantry rotation speed, cone angle, tube current, etc. Therefore, in calibration, multiple combinations of 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 a 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 acquire 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; The update frequency of each calibration data is determined 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] In addition, a 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; The update frequency of each calibration data is determined 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 is. [Effects 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 purpose of the executed shooting. Therefore, when calibration data is used less frequently or when calibration data is used for shooting with a small weighting coefficient, the update frequency of the calibration data can be reduced, thereby shortening the time required for one calibration. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a block diagram of a CT system 10 according to the present embodiment. [Figure 2] FIG. 10 is an explanatory diagram of calibration. [Figure 3] FIG. 1 is an explanatory diagram of steps performed on clinic day 1. [Figure 4] FIG. 10 is a diagram showing how photography 1 is performed. [Figure 5] FIG. 1 is a flow diagram of a method for determining the update frequency of calibration data D1, D2, and D3. [Figure 6] FIG. 6 is a table for explaining steps ST1 to ST4 of FIG. 5. [Figure 7] FIG. 10 is a diagram showing index values ​​and update frequencies of calibration data D1, D2, and D3 stored in association with Photo 1. [Figure 8] FIG. 10 is a diagram showing a state in which photographing 2 is performed. [Figure 9] 6 is a table for explaining each step in FIG. 5 when photographing 2 is performed. [Figure 10] FIG. 10 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. 10 is a diagram showing a state in which photographing 3 is performed. [Figure 12] FIG. 6 is a table illustrating the steps of FIG. 5 when photographing 3 is performed. [Figure 13] FIG. 10 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. 10 is a diagram showing a state in which photographing 4 is performed. [Figure 15] FIG. 6 is a diagram showing a table for explaining each step in FIG. 5 when photographing 4 is performed. [Figure 16] FIG. 10 is a diagram showing index values ​​and update frequencies of calibration data D1, D2, and D3 stored in association with photography 4. [Figure 17] FIG. 10 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]10 is a diagram showing index values ​​and update frequencies of calibration data D1, D2, and D3 stored in association with photograph 5. FIG. [Figure 20] FIG. 10 is an explanatory diagram of treatment day 2. [Figure 21] FIG. 10 is an explanatory diagram of step ST22. [Figure 22] FIG. 6 is a table illustrating the steps of FIG. 5 when a sixth photograph is taken. [Figure 23] 10 is a diagram showing index values ​​and update frequencies of calibration data D1, D2, and D3 stored in association with photograph 6. FIG. [Figure 24] FIG. 10 is a diagram showing the index values ​​and update frequencies obtained in the last imaging p on clinic day 2. [Figure 25] FIG. 10 is an explanatory diagram of treatment day 3. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a description will be given of an embodiment of the invention, but the present invention is not limited to the following embodiment.

[0015] FIG. 1 is a block diagram of a CT system 10 according to this 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 unit 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 when a predetermined voltage is applied to the cathode-anode tube. The X-ray tube 104 is configured to be rotatable on a path centered on a rotation axis 206 within 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 the 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 system, 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. Note that although the CT system 10 includes one X-ray tube 104A in this embodiment, it may also 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 areas 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 an object 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 The projection data is collected by the DAS 214. The DAS 214 performs predetermined processing on the collected projection data, including sampling, digital conversion, etc. 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 include, 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] Computer 216 includes one or more processors 217. Using the one or more processors, computer 216 outputs commands and parameters to DAS 214, X-ray controller 210, and / or gantry motor controller 212 to control system operations such as data acquisition and / or processing. 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 FIG. 1 shows one or more processors 217 included in computer 216, one or more processors 217 may be distributed between computer 216 and other components (e.g., X-ray controller 210, gantry motor controller 212, table controller 118, etc.).

[0025] An operator console 220 is coupled to the computer 216. An operator can operate the operator console 220 to enter predetermined operator inputs related to the operation of the CT system 10 into the computer 216. The computer 216 receives operator inputs, including commands and / or scan parameters, via the operator console 220 and controls system operation 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 the 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 , more than one operator console 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 appropriately for imaging.

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

[0032] Image reconstructor 230 can store the reconstructed image in storage device 218. Image reconstructor 230 may also transmit the reconstructed image to computer 216. Computer 216 can transmit the reconstructed image and / or patient information to a display device 232 communicatively coupled to computer 216 and / or 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 on a single storage medium or may be distributed across multiple storage media. Additionally, the instructions may be stored on 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 on 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 components deteriorate over time, and as a result, the characteristics of the components used in the CT system change. Therefore, the CT system periodically performs calibration scans to obtain calibration data for correcting the changes in the components' characteristics.

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

[0036] In calibration using 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. 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 X-ray data detected by the detector 108. FIG. 2 shows an example in which z pieces of calibration data D1 to Dz are generated for the 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 of longer calibration times. For example, if three rotation speeds (r1, r2, r3) are considered, three cone angles (c1, c2, c3) are considered, and three tube currents (a1, a2, a3) are considered, 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 pieces of calibration data must be obtained, resulting in a problem of longer calibration times.

[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 a diagram illustrating the steps performed on clinic day 1.

[0040] In step ST11, calibration is performed. In the calibration, z pieces of calibration data are generated as described with reference to FIG. 2. However, in the following, to facilitate understanding of this embodiment, only three pieces of calibration data D1, D2, and D3 will be considered as the generated calibration data. 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] In the box of step ST12, examples of imaging that were actually performed in the examination are shown in chronological order. For the sake of convenience, 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 purpose of shooting are shown.

[0044] For example, "D1" is written in the box for Shooting 1. This means that, for Shooting 1, the processor selected calibration data D1 from calibration data D1 to D3 as the calibration data to be used for image reconstruction. Also, "k=1.5" is written in the box for 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 reflects the shooting purpose. For example, high image quality may be required depending on the shooting purpose, in which case the weighting coefficient k is set to a high value. On the other hand, image quality required depending on the shooting purpose may not be so high, in which 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. For Shooting 1, the weighting coefficient k is k=1.5.

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

[0046] Referring to the box for Image 3, "D1" is written in the box for Image 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 for Image 3. Therefore, the weighting coefficient k for Image 3 is k=0.5.

[0047] Referring to the box for Image 4, "D3" is written inside the box for Image 4. This means that in Image 4, the processor selected 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 inside the box for Image 4. Therefore, the weighting coefficient k in Image 4 is k=0.5.

[0048] Referring to the box for image 5, "D1" is written in the box for image 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 for image 5. Therefore, the weighting coefficient k for image 5 is k=1.5.

[0049] Each time photography 1 to 5 is performed, the processor determines the update frequency of each calibration data in consideration of the usage status of the calibration data used in the photography. The update frequency of the calibration data represents the degree to which the calibration data is repeatedly updated. For example, in this embodiment, the following three types of update frequencies 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 two days) 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] The 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 multiple protocols. Each protocol has a weighting coefficient corresponding to the purpose of shooting, and the processor can read out the value of the weighting coefficient as needed. After the protocol is selected, shooting 1 is performed as shown in FIG. 4. When shooting 1 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.

[0052] Fig. 5 is a flow diagram of a method for determining the update frequency of the calibration data D1, D2, and D3 when photographing 1 is performed, and Fig. 6 is a diagram showing a table for explaining steps ST1 to ST4 of 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, which is a criterion 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, the 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 Q1=0 to the score Q1. 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 Q1=0 to the score Q1.

[0058] After determining the score Q1, the processor determines an index value B1, which is a criterion 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, B1=0 is determined. 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, the 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, which is a criterion for determining the update frequency of the calibration data D3, based on the score R1. In the photograph 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 is determined to be 1.5, the index value B1 is determined to be 0, and the index value C1 is determined to be 0. After determining these index values ​​A1, B1, and C1, the process proceeds to step ST4.

[0063] (Regarding 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 index value A1=1.5, index value B1=0, and 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 index value A1 and 0% for index values ​​B1 and C1. Then, the processor compares the ratio of each index value with a threshold. In this embodiment, two thresholds are considered: a threshold TH1 and a threshold TH2 that is smaller than TH1. For ease of explanation, the thresholds TH1=60% and TH2=20% are assumed below. Then, the processor determines which of the following conditions 1 to 3 the ratio P of each index value satisfies with respect to the thresholds TH1 and 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 daily; 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 should 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 should be updated every two days. After determining the update frequency, the flow in FIG. 5 ends.

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

[0069] Next, the operator operates the console to input a signal to select a protocol corresponding to the purpose of photography 2. When this signal is input, the processor selects a protocol corresponding to the purpose of photography 2 from among a plurality of protocols. After the protocol is selected, photography 2 is executed as shown in FIG. 8. When photography 2 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 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 photographing 2 is performed. Note that Fig. 9 shows not only the table for photographing 2 but also the table for photographing 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 was not used in shooting 2, the processor assigns P2=0 to the score P2. On the other hand, if the calibration data D1 was used in shooting 2, the processor assigns the value of the weighting coefficient k to the score P2. Since the calibration data D1 was 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 serves as a reference for determining the update frequency of the calibration data D1 based on the score P2. Specifically, the processor adds the score P2 to the index value A1 determined in the photograph 1 to calculate the index value A2 (=A1+P2). 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 was not used in shooting 2, the processor assigns Q2=0 to the score Q2. On the other hand, if the calibration data D2 was used in shooting 2, the processor assigns the value of the weighting coefficient k to the score Q2. Since the calibration data D2 was 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 Q2=1.5 to the score Q2.

[0077] After determining the score Q2, the processor determines an index value B2 that serves as a reference for determining the update frequency of the calibration data D2 based on the score Q2. Specifically, the processor adds the score Q2 to the index value B1 determined in the photograph 1 to calculate the index value B2 (=B1+Q2). 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 serves as a reference for determining the update frequency of the calibration data D3. Specifically, the index value is determined 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 R2=0 to the score R2. On the other hand, if the calibration data D3 was used in shooting 2, the processor assigns a weighting coefficient value to the score R2. Since the calibration data D3 was not used in shooting 2, the processor determines the score R2 to be R2=0.

[0081] After determining the score R2, the processor determines an index value C2 that serves as 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 index value A2 = 1.5, index value B2 = 1.5, and index value C2 = 0. After determining these index values ​​A2, B2, and C2, the process proceeds to step ST4.

[0084] (Regarding 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 index value C2 is L=0%. Therefore, the proportion L of index value B2 satisfies condition 3, so the processor determines that calibration data D2 should be updated every two days. After determining the update frequency, the flow in FIG. 5 ends.

[0089] After determining the update frequency, the processor stores the index values ​​and update frequencies calculated according to the flow in Fig. 5 in the storage device. 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 photography 3. When this signal is input, the processor selects a protocol corresponding to the purpose of photography 3 from among a plurality of protocols. After the protocol is selected, photography 3 is executed as shown in FIG. 11. When photography 3 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 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 Shooting 3 is executed. Note that Fig. 12 shows not only the table for Shooting 3 but also the table for Shooting 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 serves as a reference 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, the score Q3 of the calibration data D2 for Shooting 3 is determined. If the calibration data D2 was not used in Shooting 3, the processor assigns Q3=0 to the score Q3. On the other hand, if the calibration data D2 was used in Shooting 3, the processor assigns the value of the weighting coefficient k to the score Q3. Since the calibration data D2 was not used in Shooting 3, the processor assigns Q3=0 to the score Q3.

[0098] After determining the score Q3, the processor determines an index value B3 that serves as a reference 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 serves as a reference for determining the update frequency of the calibration data D3. Specifically, the index value is determined 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 R3=0 to the score R3. On the other hand, if the calibration data D3 was used in Shooting 3, the processor assigns a weighting coefficient value to the score R3. Since the calibration data D3 was not used in Shooting 3, the processor determines the score R3 to be R3=0.

[0102] After determining the score R3, the processor determines an index value C3 that serves as 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 index value A3 = 2.0, index value B3 = 1.5, and index value C3 = 0. After determining these index values ​​A3, B3, and C3, the process proceeds to step ST4.

[0105] (Regarding 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 percentage L (%) of each index value relative 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 percentage 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 percentage of each index value with a threshold value and determines which of conditions 1 to 3 the percentage P of each index value satisfies with respect to threshold values ​​TH1 and 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 should be updated every two days. After determining the update frequency, the flow in FIG. 5 ends.

[0110] After determining the update frequency, the processor stores the index values ​​and update frequencies calculated according to the flow in Fig. 5 in the storage device. 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 photography 4. When this signal is input, the processor selects a protocol corresponding to the purpose of photography 4 from among a plurality of protocols. After the protocol is selected, photography 4 is executed as shown in FIG. 14. When photography 4 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 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 was not used in Shooting 4, the processor assigns P4=0 to the score P4. On the other hand, if the calibration data D1 was used in Shooting 4, the processor assigns the value of the weighting coefficient k to the score P4. Since the calibration data D1 was 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, which serves as 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 was not used in Shooting 4, the processor assigns Q4=0 to the score Q4. On the other hand, if the calibration data D2 was used in Shooting 4, the processor assigns the value of the weighting coefficient k to the score Q4. Since the calibration data D2 was not used in Shooting 4, the processor assigns Q4=0 to the score Q4.

[0119] After determining the score Q4, the processor determines an index value B4 that serves as 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 serves as a reference for determining the update frequency of the calibration data D3. Specifically, the index value is determined as follows.

[0122] In step ST3, the processor determines a score R4. If the calibration data D3 was not used in Shooting 4, the processor assigns R4=0 to the score R4. On the other hand, if the calibration data D3 was used in Shooting 4, the processor assigns the value of the weighting coefficient k to the score R4. Since the calibration data D3 was 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, which serves as a reference for determining the update frequency of the calibration data D3, based on the score R4. Specifically, the processor adds the score R4 to the index value C3 determined in the photograph 3 to calculate the index value C4 (=C3+R4). 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 index value A4=2.0, index value B4=1.5, and index value C4=0.5. After determining these index values ​​A4, B4, and C4, the process proceeds to step ST4.

[0126] (Regarding 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 percentage L (%) of each index value relative 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 percentage 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 percentage of each index value with a threshold value and determines which of conditions 1 to 3 the percentage L of each index value satisfies with respect to threshold values ​​TH1 and 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, and the processor determines that the calibration data D1 should 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 in FIG. 5 ends.

[0131] After determining the update frequency, the processor stores the index values ​​and update frequencies calculated according to the flow in Fig. 5 in the storage device. 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 photography 5. When this signal is input, the processor selects a protocol corresponding to the purpose of photography 5 from among a plurality of protocols. After the protocol is selected, photography 5 is executed as shown in FIG. 17. When photography 5 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 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 Shooting 5 is performed. Note that Fig. 18 shows not only the table for Shooting 5 but also the table for Shooting 4.

[0134] FIG. 18 shows the update frequencies determined by executing steps ST1 to ST4 for shooting 5. The method for determining the update frequencies has been described above, so the description of FIG. 18 will be omitted. For shooting 5, it has been determined that calibration data D1 will be updated daily, calibration data D2 will be updated every other day, and calibration data D3 will be updated every two days. The processor saves the index values ​​A5, B5, and C5 obtained for shooting 5 and the update frequencies "daily," "every other day," and "every two days" in the storage device. FIG. 19 shows the index values ​​and update frequencies of calibration data D1, D2, and D3 stored in association with shooting 5. Note that the index values ​​and update frequencies obtained for the previous shooting 4 are discarded as 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 "daily," "every other day," and "every two days," respectively.

[0136] Next, the 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 scan 5 for calibration data D1, D2, and D3 are shown, along with the latest update frequencies of "daily," "every other day," and "every two days."

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

[0140] Furthermore, 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 consultation day 1, and therefore the calibration data D2 was updated on the day before consultation day 2 (consultation day 1). Therefore, the processor determines that the calibration data D2 will not be updated on consultation day 2. Therefore, the processor determines not to perform a calibration scan to acquire the calibration data D2.

[0141] Furthermore, 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 consultation day 1, and therefore the calibration data D3 was updated on the day before consultation day 2 (consultation day 1). Therefore, the processor determines that the calibration data D3 will not be updated on consultation day 2. Therefore, the processor determines not to perform a calibration scan to acquire the calibration data D3.

[0142] As a result, the processor determines to perform only the calibration scan to obtain the calibration data D1 on the consultation 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 to select a protocol corresponding to the purpose of photography 6. When this signal is input, the processor selects a protocol corresponding to the purpose of photography 6 from among a plurality of protocols. After the protocol is selected, photography 6 is executed. When photography 6 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 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, 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 the weighting coefficient k to the score P6. Since the calibration data D1 is used in Shooting 6, the processor assigns the value of the 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 serves as a reference 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 photograph 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 Photoshoot 6 is determined. If the calibration data D2 was not used in Photoshoot 6, the processor assigns Q6=0 to the score Q6. On the other hand, if the calibration data D2 was used in Photoshoot 6, the processor assigns the value of the weighting coefficient k to the score Q6. Since the calibration data D2 was not used in Photoshoot 6, the processor assigns Q6=0 to the score Q6.

[0153] After determining the score Q6, the processor determines an index value B6 that serves as 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 serves as a reference for determining the update frequency of the calibration data D3. Specifically, the index value is determined 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 R6=0 to the score R6. On the other hand, if the calibration data D3 was used in Shooting 6, the processor assigns the value of a weighting coefficient to the score R6. Since the calibration data D3 was not used in Shooting 6, the processor determines the score R6 to be R6=0.

[0157] After determining the score R6, the processor determines an index value C6 that serves as 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, the index value A6=5.0, the index value B6=1.5, and the index value C6=0.5 are determined for photograph 6. After determining these index values ​​A6, B6, and C6, the process proceeds to step ST4.

[0159] (Regarding 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 percentage L (%) of each index value relative 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 percentage 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 percentage of each index value with a threshold value and determines which of conditions 1 to 3 the percentage P of each index value satisfies with respect to threshold values ​​TH1 and 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 should be updated daily.

[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 therefore 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 in FIG. 5 ends.

[0164] After determining the update frequency, the processor stores in the storage device the index values ​​and update frequencies calculated according to 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 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 next photographing is awaited, and the flow of FIG. 5 is executed each time a photographing operation is performed, thereby determining the update frequency.

[0166] 24 is a diagram showing the index values ​​and update frequencies obtained in the last imaging p of treatment day 2. On treatment 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 of "daily," "every other day," and "every two days," are shown.

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

[0171] Furthermore, 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 consultation day 1, but not on consultation day 2. Therefore, the processor determines that the calibration data D2 should be updated on consultation day 3. Therefore, the processor determines to perform a calibration scan to acquire the calibration data D2.

[0172] Furthermore, 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 consultation day 1, but not on consultation day 2. Therefore, the processor determines that the calibration data D3 will not be updated on consultation day 3. Therefore, the processor determines not to perform a calibration scan to acquire the calibration data D3.

[0173] As a result, on clinic day 3, the processor determines to perform only a calibration scan to obtain calibration data D1 and a calibration scan to obtain calibration data D2. Therefore, in step ST31, only calibration data D1 and D2 are obtained.

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

[0175] In this embodiment, when determining the update frequency, the processor assigns a weighting coefficient k to the score of calibration data used during imaging, while assigning a score of zero to calibration data not used during imaging. The processor then calculates the latest index value by adding the score to the index value obtained during the previous imaging, and determines the update frequency for each calibration data item based on the latest index value. Therefore, an index value reflecting the number of times the calibration data is used can be calculated each time imaging is performed. Furthermore, in this embodiment, the weighting coefficient k assigned to the score differs depending on the imaging purpose. Therefore, an index value reflecting the weighting coefficient k can be calculated each time imaging is performed. In other words, in this embodiment, the update frequency of the calibration data is determined not by focusing only on the number of times the calibration data is used, but by taking into account both the number of times the calibration data is used and the weighting coefficient k. Therefore, when the number of times the calibration data is used and the weighting coefficient k for the imaging in which the calibration data was used are low, the update frequency of the calibration data is low, thereby shortening the time required for one calibration of the CT system.

[0176] Furthermore, 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 acquire images of three time phases of the liver, the weighting coefficient k can be set to a high value, and in imaging that does not require as high an image quality, such as imaging to acquire images of blood vessels, 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 does not require as high an image quality, the update frequency of the calibration data can be decreased. Therefore, the update frequency can be determined taking into consideration the balance between the time required for calibration and the required image quality.

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

[0178] Furthermore, in imaging that does not require a very high image quality, such as imaging to acquire 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 imaging that does not require a very high image quality, if there is a high demand for imaging, the update frequency of the calibration data can be increased.

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

[0181] In this embodiment, an example is shown in which the CT system 10 is used as the 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 (for example, 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 systems 102 Gantry 103 Filter section 104 X-ray generator 104A X-ray tube 104B Generator 105 Collimator 106 X-ray 107 Bore 108 detectors 112 Subject 116 tables 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 acquire medical images 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; The update frequency of each calibration data is determined 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 is calculated for each calibration data item each time imaging is performed, the index value reflecting the number of times the calibration data item has been used and a weighting coefficient according to the imaging purpose of the subject.

4. the one or more processors determining a score for each calibration data item each time a photograph is taken; The medical system according to claim 3 , wherein the index value is calculated based on the score.

5. the one or more processors assigning the score a first value according to a weighting factor if the calibration data has not been used to reconstruct an image; assigning a second value to the score if calibration data has not been used to reconstruct an image. The medical system according to claim 4 , wherein the medical system executes the following:

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

7. When one image is captured, the one or more processors determining a first score for each calibration data; calculating a first index value for each calibration data item based on the first score, the first index value reflecting the number of times the calibration data item has been used and a weighting coefficient; and determining a first update frequency for each calibration data item based on the first index value; Run When a next image capture is performed after the one image capture, the one or more processors determining a second score for each calibration data; calculating, for each calibration data, a second index value that reflects the number of times the calibration data 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 according to claim 4 , wherein the medical system executes the following:

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 the purpose of imaging from among a plurality of protocols based on a signal input from the 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 the X-ray tube is switched between a first tube voltage and a second tube voltage.

13. a storage device of the medical system or a storage device accessible by the medical system stores the latest update frequency of each calibration data; the one or more processors The medical system according to claim 1 , wherein when a command to perform calibration is input from a console, it is determined whether 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 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; The update frequency of each calibration data is determined 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 that causes the

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