JP6749757B2 - Radiation tomography system - Google Patents

Description

The present invention relates to a radiation tomography system for calculating an estimated value of radiation exposure dose and a control program therefor.

BACKGROUND ART As one of treatments on a subject in a medical institution, puncture under an X-ray CT guide (X-ray Computed Tomography guide) called CT fluoro (CT fluoro) is known (for example, refer to Patent Document 1). ). In the puncture, the operator operates the X-ray CT system to take a single or continuous image around the affected area of the subject at a necessary timing. The tomographic image obtained by the imaging is displayed on a monitor installed in the examination room facing the operator. The operator inserts the puncture needle into the subject and guides it to the affected area while referring to the tomographic image displayed on the monitor.

JP, 2005-84800, A

In the above-mentioned puncture under the X-ray CT guide, the operator wears protective clothing, for example, in order to reduce the amount of exposure of the operator to scattered X-rays. However, the finger or hand holding the puncture needle may be exposed. Therefore, there is a need to know the radiation dose of the operator.

The invention made to solve the above problems is based on the data of the radiation tomographic image obtained by scanning the subject with radiation, and the radiation tomographic image of the human body existing outside the region of the subject is obtained. Based on the radiation dose in the subject obtained in advance before the scan, and the detection unit to detect in the slice plane to be created, the estimated value of the radiation dose in the human body detected by the detection unit is calculated. The radiation tomography system is characterized by comprising: a calculating unit and a notifying unit that gives notification based on the estimated value of the radiation exposure dose calculated by the calculating unit.

According to the invention of the above aspect, the calculation unit calculates, for example, an estimated value of a radiation exposure dose in a human body such as an operator, and the notification based on the estimated value of the radiation exposure dose is performed. You can know the radiation dose.

FIG. 1 is a diagram schematically showing a hardware configuration of an X-ray CT system according to an embodiment. It is a figure which shows the outline of an examination room. It is a functional block diagram of the operation console of the X-ray CT system shown in FIG. It is a flow chart which shows a flow of processing of an X-ray CT system concerning an embodiment. It is a figure explaining the area|region where the corresponding pixel continues in the tomographic image data of the value of a required range, and a tomographic image. It is a figure which shows the tomographic image of a subject, and is a figure explaining the method of specifying the area|region which has a required area. It is a figure which shows the tomographic image of a subject, and is a figure explaining another method of pinpointing the area|region which has a required area. It is a figure which shows the measurement position of the CTDI value memorize|stored in the memory|storage device. It is a figure explaining an example of calculation of the estimated value of the X-ray exposure dose of a detection target. It is a figure explaining the other example of calculation of the estimated value of the X-ray exposure dose of a detection target. It is a figure which shows the screen of the inspection room display device in which the X-ray exposure dose was displayed. It is a figure which shows the screen of the examination room display device in which the X-ray exposure dose and the warning message were displayed.

Hereinafter, embodiments of the present invention will be described. FIG. 1 shows an X-ray CT system 1 which is an example of an embodiment of a radiation tomography system according to the present invention. As shown in FIG. 1, the X-ray CT system 1 includes a gantry 2, an imaging table 4, and an operation console 6. Further, the X-ray CT system 1 includes an examination room display device 100 and a foot switch 102, which will be described later, shown in FIG.

The gantry 2 includes an X-ray tube 21, an aperture 22, a collimator device 23, an X-ray detector 24, a data acquisition unit 25, a rotation unit 26, a high voltage power supply 27, an aperture drive unit 28, and a rotation drive. It has a device 29 and a gantry table controller 30.

The X-ray tube 21 and the X-ray detector 24 are arranged so as to face each other with the opening 2B in between.

The aperture 22 is arranged between the X-ray tube 21 and the opening 2B. The X-rays emitted from the X-ray focal point of the X-ray tube 21 toward the X-ray detector 24 are shaped into a fan beam or a cone beam.

The collimator device 23 is arranged between the opening 2B and the X-ray detector 24. The collimator device 23 removes scattered rays that enter the X-ray detector 24.

The X-ray detector 24 has a plurality of two-dimensionally arranged in a spreading direction (referred to as a channel direction) and a thickness direction (referred to as a column direction) of a fan-shaped X-ray beam emitted from the X-ray tube 21. It has an X-ray detection element. Each X-ray detection element detects each transmitted X-ray of the subject 5 arranged in the opening 2B and outputs an electric signal according to its intensity. The subject 5 is, for example, a living body such as a human being or an animal.

The data collection unit 25 receives the electric signal output from each X-ray detection element of the X-ray detector 24, converts it into X-ray data, and collects it.

The rotating portion 26 is rotatably supported around the opening 2B. An X-ray tube 21, an aperture 22, a collimator device 23, an X-ray detector 24, and a data acquisition unit 25 are mounted on the rotating unit 26.

The imaging table 4 has a cradle 41 and a cradle drive device 42. The subject 5 is placed on the cradle 41. The cradle drive device 42 moves the cradle 41 into and out of the opening 2B of the gantry 2, that is, the photographing space.

The high voltage power supply 27 supplies a high voltage and current to the X-ray tube 21.

The aperture driving device 28 drives the aperture 22 and deforms its opening.

The rotary drive device 29 drives the rotary unit 26 to rotate.

The gantry/table control unit 30 controls each device/unit in the gantry 2, the imaging table 4, and the like.

The gantry 2 and the imaging table 4 are provided in the examination room R as shown in FIG. Further, in the examination room R, an examination room display device 100 is provided near the imaging table 4. Various images are displayed on the inspection room display device 100 as described later.

In FIG. 2, the inspection room display device 100 is indicated by an arm 101 attached to a ceiling C of the inspection room R. The arm 101 is movable (detailed configuration is not shown), and the orientation and position of the examination room display device 100 can be adjusted so that the operator can easily see it. The inspection room display device 100 is connected to the operation console 6.

A foot switch 102 is provided in the examination room R. In this example, the foot switch 102 is placed on the floor F of the examination room R and is connected to the operation console 6.

The operation console 6 is provided in an operation room (not shown) adjacent to the examination room R. The operation console 6 receives various operations from the operator. The operation console 6 has an input device 61, a display device 62, a storage device 63, and an arithmetic processing device 64. In this example, the operation console 6 is composed of a computer.

The input device 61 includes buttons and keyboards for receiving instructions and information input from the operator, and further includes a pointing device and the like. The display device 62 is an LCD (Liquid Crystal Display), an organic EL (Electro-Luminescence) display, or the like.

The storage device 63 is a hard disk drive (HDD), a semiconductor memory (Memory) such as a RAM (Random Access Memory), a ROM (Read Only Memory), or the like. The operation console 6 may include the HDD, the RAM, and the ROM as the storage device 63. The storage device 63 may include a portable storage medium such as a CD (Compact Disk) or a DVD (Digital Versatile Disk).

The arithmetic processing unit 64 is a processor such as a CPU (central processing unit).

Here, as shown in FIG. 1, the body axis direction of the subject 5, that is, the transport direction of the subject 5 by the imaging table 4 is the z direction. The vertical direction is the y direction, and the horizontal direction orthogonal to the y and z directions is the x direction.

As shown in FIG. 3, the operation console 6 includes a scan control unit 71, an image reconstruction unit 72, a detection unit 73, a calculation unit 74, and a display control unit 75 as functional blocks. The arithmetic processing unit 64 causes the functions of the scan control unit 71, the image reconstruction unit 72, the detection unit 73, the calculation unit 74, and the display control unit 75 to be executed by a predetermined program (program). The predetermined program is stored in, for example, a non-transitory storage medium such as an HDD or a ROM that constitutes the storage device 63. Further, the program may be stored in a portable, non-transitory storage medium such as a CD or a DVD that constitutes the storage device 63.

The scan control unit 71 controls the gantry/table control unit 30 so that scanning is performed according to the operation of the operator.

The image reconstructing unit 72 reconstructs a scout image based on projection data obtained by a scout scan that is preliminarily performed. The image reconstruction unit 72 also performs image reconstruction processing based on the projection data obtained by scanning the subject 5 with X-rays, and obtains tomographic image data. The tomographic image data is an example of an embodiment of data of a radiation tomographic image in the present invention. The scan includes a helical scan and a puncture scan, which will be described later.

The detection unit 73 detects, based on the tomographic image data, a human body existing outside the region of the subject 5 in a slice plane in which a tomographic image based on the tomographic image data is image-reconstructed. The detection unit 73 detects a human body different from the subject 5, such as an operator performing a puncture procedure. Details will be described later. The detector 73 is an example of an embodiment of the detector in the present invention. The function of the detection unit 73 is an example of the embodiment of the detection function of the present invention.

The calculation unit 74 calculates the X-ray exposure dose in the human body detected by the detection unit 73 as an estimated value based on the X-ray exposure dose in the subject obtained in advance before the puncture scan. Details will be described later. The X-ray exposure dose obtained in advance in the subject before the puncture scan is, for example, the X-ray exposure dose obtained in advance in a CTDI phantom or a human body simulation phantom. The calculator 74 is an example of an embodiment of the calculator in the present invention. The function of the calculation unit 74 is an example of the embodiment of the calculation function of the present invention.

The display control unit 75 causes the display device 62 and the examination room display device 100 to display various images and texts (text) including a scout image and a tomographic image. For example, the display control unit 75 causes the display device 62 and the inspection room display device 100 to display the X-ray exposure dose calculated by the calculation unit 74, a warning message described below, and the like as text. The display control unit 75 is an example of an embodiment of the notification unit in the present invention. Further, the display function of the X-ray exposure dose and the warning message by the display control unit 75 is an example of the embodiment of the display control function in the present invention.

Next, the flow of processing in the X-ray CT system according to this embodiment will be described based on the flowchart of FIG. First, in step S1, the subject 5 is placed on the imaging table 4 to prepare for imaging. Next, in step S2, a scout scan and a helical scan for setting conditions for puncture scan (CT fluorography) and confirming the puncture position are performed. The scout scan and the helical scan are performed by the scan control unit 71 controlling the gantry/table control unit 30.

Next, in step S3, based on the projection data obtained by the scout scan and the helical scan performed in step S2, the operator or the like sets the conditions for the puncture scan or the position at which the puncture needle is inserted (puncture needle). Position). The surgeon or the like sets the conditions for the puncture scan and determines the puncture position based on the scout image or tomographic image created based on the projection data obtained by the scout scan and the helical scan. ..

Next, in step S4, a puncture scan is started. The puncture scan is started when the operator operates the foot switch 102, for example. More specifically, when the operator steps on the foot switch 102, the scan control unit 71 controls the gantry/table control unit 30 to start the puncture scan. The puncture scan is performed on the slice plane SP including the puncture position.

Further, in step S4, a tomographic image I created based on tomographic image data obtained by image reconstruction of projection data obtained by the puncture scan is displayed on the examination room display device 100 and the display device 62. May be done. When the tomographic image I is displayed on the examination room display device 100, the operator in the examination room R performs a puncture procedure on the subject 5 while watching the displayed tomographic image I. The tomographic image I is an example of the embodiment of the radiation tomographic image in the present invention.

Next, in step S5, based on the tomographic image data obtained by performing image reconstruction processing on the projection data obtained by the puncture scan, the detection unit 73 slices the human body existing outside the region of the subject. Detect at SP. The human body existing outside the region of the subject to be detected by the detection unit 73 is the finger and hand of the operator who performs the puncture procedure.

The detection of the operator's finger and hand by the detection unit 73 will be described in detail. When one frame of tomographic image data is obtained on the slice plane SP by the puncture scan, the detection unit 73 performs detection based on this tomographic image data. The tomographic image data of one frame is obtained by, for example, so-called half scan in which the view angle range is 180 degrees+the fan angle α of the X-ray beam.

In the tomographic image data, the detection unit 73 identifies tomographic image data having a value in a required range set as a value that can be taken by a finger and a hand that are detection targets. Here, a range of CT values that can be taken by a finger and a hand is set as a required range. For example, a CT value range of -100 or more and 1500 or less is set as the required range. The CT value in the required range is stored in the storage device 63.

The detection unit 73 identifies the tomographic image data having a CT value of −100 or more and 1500 or less, and as illustrated in FIG. , As the detection target. Then, the detection unit 73 detects a region in which the size of the region CR satisfies the condition set as the size in the tomographic image of the detection target hand and finger. For example, as the condition, the range S1≦S≦S2 of the area S of the hand and fingers in the tomographic image is set. S1≦S≦S2 is a range smaller than the cross section of the abdomen or the like of the subject 5. The range S1≦S≦S2 of the sectional area S is stored in the storage device 63. The detection unit 73 identifies a region CR in which the area S is S1≦S≦S2 as a hand or a finger as a detection target.

Here, as shown in FIG. 6, in the tomographic image I created based on the tomographic image data, the puncture needle N is present near the detection target T which is the operator's finger or hand. Therefore, the detection unit 73 may refer to the position of the puncture needle N in the tomographic image I to specify the position for detecting the region CR. Specifically, the detection unit 73 first detects the puncture needle N based on the tomographic image data. Since the CT value of the puncture needle N is different from the CT value of the human body, the detection unit 73 detects the puncture needle N by specifying tomographic image data having the value set as the CT value of the puncture needle. The value set as the CT value of the puncture needle is, for example, a CT value of 3000 HU or more. Then, the detection unit 73 specifies a region CR having an area S of S1≦S≦S2 in the vicinity of the detected puncture needle N as a finger or hand as a detection target. The detection unit 73 may set a region having a required area including the puncture needle N and perform detection in the region.

Instead of detecting the puncture needle N, as shown in FIG. 7, the detection region DR is set on the screen 100a of the inspection room display device 100 on which the tomographic image I is displayed, and the detection unit 73 detects the inside of the detection region DR. In, the area CR in which the area S is S1≦S≦S2 may be specified as the detection target T.

For example, the detection region DR is set by the operator's input on the screen 100a of the examination room display device 100. In this case, for example, the operator sets the detection region DR using the operation device 103 in the examination room R. Although the operation device 103 is provided on the imaging table 4 in FIG. 2, the operation device 103 is not limited to this. The operation device 103 is an example of an embodiment of an input device that receives an input designating a detection area in the present invention.

The detection region DR may be set using the operation console 6. In this case, the operation console 6 is an example of an embodiment of an input device that receives an input designating a detection area in the present invention.

Next, in step S6, the calculation unit 74 calculates the estimated value of the X-ray exposure dose of the finger or hand detected in step S5. The X-ray exposure dose here is the X-ray exposure dose in the puncture scan.

The calculation of the estimated value of the X-ray exposure dose in step S6 will be specifically described. The calculation unit 74, based on the X-ray exposure dose in the subject obtained in advance by, for example, the CTDI phantom or the human body simulation phantom before the puncture scan, the X-ray exposure dose in the finger or hand detected in step S5. Calculate the estimated value of. The X-ray exposure dose of the subject obtained in advance before the puncture scan is the X-ray exposure dose of a plurality of points on one slice plane, and is a measurement value obtained by measurement in advance. A CTDI (CT dose index) value can be given as an example of the measurement value obtained by measuring in advance. The CTDI value is stored in the storage device 63. As the CTDI value, for example, as shown in FIG. 8, measured values in a plurality of portions Ap, Bp, Cp, Dp, Ep on the slice plane SPc are stored. Corresponding positions in the tomographic images of the plurality of portions Ap, Bp, Cp, Dp, Ep are specified. Incidentally, for convenience of explanation, the slice plane SPc is shown by a circle having a predetermined radius centered on an isocenter (ISO) IS which is an intersection of dashed lines in FIG. The distance between each of the plurality of portions Ap, Bp, Cp, Dp, Ep and the isocenter IS is equal.

The calculation unit 74 calculates the estimated value based on the CTDI value selected from the CTDI values in the plurality of parts Ap, Bp, Cp, Dp, and Ep according to the finger or hand position detected by the detection unit 73. Calculate. The calculation unit 74 selects two CTDI values in ascending order of the distance to the finger or hand detected by the detection unit 73. For example, in FIG. 9, symbol T1 indicates a detection target that is a finger or a hand detected by the detection unit 73. The calculation unit 74 selects the CTDI _B value in the portion Bp having the shortest distance to the detection target T1 and the CTDI _C value in the portion Cp having the shortest distance to the detection target T1 next to the portion Bp. Further, when the detection unit 73 detects the detection target T2 at the position shown in FIG. 10, the calculation unit 74 detects the CTDI _E value in the portion Ep having the smallest distance from the detection target T2 and the detection next to the portion Ep. The CTDI _B value in the portion Bp having a small distance from the target T2 is selected.

When the detection target T1 shown in FIG. 9 is detected by the detection unit 73, the calculation unit 74 uses the CTDI _B value and the CTDI _C value as an estimated value of the X-ray exposure dose of the detection target T1, The X-ray exposure dose of Tp1 is calculated. The portion Tp1 exists on a straight line (illustrated by a dashed line in FIG. 9) that passes through the detection target T1 and the isocenter IS. The distance between the portion Tp1 and the isocenter IS is equal to the distance between the portions Bp, Cp and the isocenter IS.

The calculation unit 74 calculates the X-ray exposure dose of the portion Tp1 by performing an interpolation calculation using the CTDI _B value and the CTDI _C value. Specifically, the calculation unit 74 performs the interpolation calculation by using the CTDI _B value and the CTDI _C value to perform weighting calculation according to the magnitudes of θ1 and θ2 shown in FIG. θ1 is an angle formed by a straight line passing through the portion Bp and the isocenter IS and a straight line passing through the portion Tp1 and the isocenter IS. Further, θ2 is an angle formed by a straight line passing through the portion Cp and the isocenter IS and a straight line passing through the portion Tp1 and the isocenter IS.

When the detecting unit 73 detects the detection target T2 shown in FIG. 10, the calculating unit 74 uses the CTDI _B value and the CTDI _E value as the estimated value of the X-ray exposure dose of the detection target T2. , X-ray exposure dose of the portion Tp2 is calculated. The portion Tp2 exists on a straight line (indicated by a chain line in FIG. 10) passing through the detection target T2 and the isocenter IS. The distance between the portion Tp2 and the isocenter IS is equal to the distance between the portions Bp, Ep and the isocenter IS.

The calculation unit 74 calculates the X-ray exposure dose of the portion Tp2 by performing an interpolation calculation using the CTDI _B value and the CTDI _E value. Specifically, the calculation unit 74 performs the interpolation calculation by using the CTDI _B value and the CTDI _E value and performing a weighting calculation according to the magnitudes of θ3 and θ4 shown in FIG. θ3 is an angle formed by a straight line passing through the portion Ep and the isocenter IS and a straight line passing through the portion Tp2 and the isocenter IS. Further, θ2 is an angle formed by a straight line passing through the portion Bp and the isocenter IS and a straight line passing through the portion Tp2 and the isocenter IS.

Next, in step S7, the display control unit 75 sets the X-ray exposure dose DC of the portion Tp1 or the portion Tp2 calculated in step S6 to the X value of the finger or hand (detection target T1 or T2) detected in step S5. The estimated value of the radiation exposure dose is displayed on the examination room display device 100 as shown in FIG. The display controller 75 may cause the display device 62 to display the X-ray exposure dose DC. The display of the X-ray exposure dose DC is an example of an embodiment of visual notification based on the radiation exposure dose by the notification unit in the present invention.

When the X-ray exposure dose DC displayed in step S7 exceeds a predetermined threshold value, the display control unit 75 may cause the inspection room display device 100 to display a warning message M as shown in FIG. In FIG. 12, the warning message M is composed of the characters “WARNING!!” indicating that the X-ray exposure dose DC exceeds a predetermined threshold value. However, the warning message M is not limited to this. The display of the warning message M is another example of the embodiment of the visual notification based on the radiation exposure dose by the notification unit in the present invention.

When the X-ray exposure dose DC displayed in step S7 exceeds a predetermined threshold value, a warning sound may be output instead of the warning message M or together with the warning message M. The output of the warning sound is an example of an embodiment of auditory notification by the notification unit according to the present invention.

Next, in step S8, the arithmetic processing unit 64 determines whether or not to end the processing. For example, the arithmetic processing device 64 determines to end the process when the input device 61 receives an input to end the shooting.

When it is determined in step S8 that the process is not to be ended (“NO” in step S8), the process returns to step S1. In this case, the processing from step S1 is repeated again, and the display of the tomographic image I is updated and the display of the X-ray exposure dose DC is also updated. On the other hand, if it is determined in step S8 that the process is to be ended ("YES" in step S8), the process is ended.

According to the present example described above, the X-ray exposure dose DC is displayed on the examination room display device 100, so that the operator in the examination room R is exposed to the X-ray exposure dose in the hand or finger performing the puncture procedure. You can know. Moreover, the display of the X-ray exposure dose DC is updated together with the display of the tomographic image I, so that the operator can know the X-ray exposure dose in real time.

Although the present invention has been described above with reference to the above-described embodiments, it goes without saying that the present invention can be variously modified and implemented without departing from the spirit of the invention. For example, as the X-ray exposure dose obtained in advance before the puncture scan, the X-ray exposure dose measured using a phantom simulating the subject may be used instead of the CTDI value described above. Good.

Further, the value of the X-ray exposure dose DC may be output by voice. The output of the X-ray exposure dose DC by voice is an example of the embodiment of the auditory notification by the notification unit in the present invention.

Further, the method of detecting the finger and hand of the operator by the detection unit 73 described in the above embodiment is an example, and the method is not limited to the above method.

1 X-ray CT system 6 Operation console 73 Detection unit 74 Calculation unit 75 Display control unit 103 Operation device

Claims (8)

Based on the data of the radiation tomographic image obtained by scanning the subject with radiation, a detection unit that detects a human body existing outside the region of the subject in a slice plane in which the radiation tomographic image is image-reconstructed. When,
Based on the radiation exposure dose obtained in advance before the scan, a calculation unit for calculating an estimated value of the radiation exposure dose in the human body detected by the detection unit,
An informing section for informing based on the estimated value of the radiation exposure dose calculated by the calculating section,
A radiation tomography system comprising: The radiation exposure dose obtained in advance before the scan is a radiation exposure dose for a plurality of locations in one slice plane,
The calculation unit calculates the estimated value based on a radiation exposure dose selected according to the position of the human body detected by the detection unit from among the radiation exposure doses at the plurality of locations. Item 1. The radiation tomography system according to Item 1. The radiation tomography according to claim 2, wherein the calculation unit calculates the estimated value by performing an interpolation calculation using a radiation exposure dose selected from radiation exposure doses at the plurality of locations. system. The detection unit specifies data of a radiation tomographic image having a value in a required range set as a range of values that can be taken by the human body as the detection target, and then, corresponds to the specified data in the radiation tomographic image. An area in which pixels are continuous is specified, and an area whose size satisfies a condition set as a size in the radiation tomographic image of the part of the human body to be detected is detected as the human body. The radiation tomography system according to any one of claims 1 to 3. The radiation tomography system according to claim 1, wherein the notification unit visually or audibly notifies the estimated value of the radiation exposure dose calculated by the calculation unit. .. The said alerting|reporting part alert|reports visually or auditorily that the estimated value of the radiation exposure dose calculated by the said calculation part exceeded the required threshold value, The any one of Claims 1-5 characterized by the above-mentioned. The radiation tomography system according to. The radiation tomography system according to any one of claims 1 to 6, wherein the radiation exposure dose obtained in advance before the scan is a measurement value obtained by performing a measurement in advance. 8. An input device that receives an input for designating a detection area to be detected by the detection unit in a radiation tomographic image displayed based on the data of the radiation tomographic image. The radiation tomography system according to item 1.