Collimator

Abstract

To provide a collimator used for half-value layer measurement by a rotating irradiation method, which allows a dosimeter to be smoothly attached and detached. [Solution] The collimator 10 includes a box-shaped housing 11 formed of plate members 11A, with the plate member 11A on the upper surface side provided with a slit 11b that allows vertically downward X-rays emitted from an X-ray source of a CT device to pass through, and a tray 12 that is installed so as to be able to be inserted and removed within the housing 11 and on which a dosimeter 4 is detachably placed. The tray 12 includes a tray body 13 that is installed within the housing 11, and a positioning frame 14 that is provided on the tray body 13 and serves to guide the dosimeter 4 when it is moved relative to the tray body 13 and to position the dosimeter 4.

Description

[Technical field]

[0001] The present invention relates to a collimator. [Background technology]

[0002] In CT examinations, radiation quality evaluation of CT devices is performed to obtain images suitable for diagnosis and to reduce the radiation dose to patients. To perform radiation quality evaluation, it is advisable to measure the half-value layer using a dosimeter and calculate the effective energy based on the half-value layer measurement value. There are two methods for half-value layer measurement: the fixed irradiation method, in which the X-ray source of the CT device is fixed directly above the bed, and the rotational irradiation method, in which the X-ray source is rotated by a rotating ring. By using the rotational irradiation method, half-value layer measurement can be performed even if the facility does not have access to the mode for fixing the X-ray source.

[0003] In the rotational irradiation method, a collimator is required to shield a part of the dosimeter so that X-rays emitted from the X-ray source in directions other than vertically downward do not enter the dosimeter. For example, Patent Document 1 discloses an example of such a collimator, which includes a housing made of an X-ray shielding material and provided with a slit through which the X-rays emitted from the X-ray source pass, and a tray that is installed in the housing so as to be removable and to which the dosimeter is detachably attached. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Registered Utility Model No. 3198259 Summary of the Invention [Problem to be solved by the invention]

[0005] The collimator of Patent Document 1 is extremely useful because it can prevent the dosimeter from being irradiated with X-rays emitted in any direction other than vertically downward by simply placing a tray with a dosimeter attached in a housing. However, in the collimator of Patent Document 1, the dosimeter needs to be accommodated without any gaps between a front fixing frame and a rear fixing frame that are provided apart from each other on a plate constituting the tray. This creates a problem in that the only way to attach and detach the dosimeter to and from the front fixing frame and the rear fixing frame is to move the dosimeter vertically.

[0006] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a collimator that is used for half-value layer measurement using the rotating irradiation method and that allows a dosimeter to be smoothly attached and detached. [Means for solving the problem]

[0007] In order to achieve the above object, the collimator according to the present invention comprises: A collimator used in half-value layer measurement in a CT scanner using a rotating irradiation method, a box-shaped housing formed of an X-ray shielding member, the box-shaped housing having a slit on an upper surface side thereof for passing vertically downward X-rays emitted from an X-ray source of the CT device; a tray that is removably installed in the housing and on which a dosimeter is detachably placed, The tray includes a tray body that is placed in the housing, and a positioning frame that is provided on the tray body, guides the dosimeter when it is moved relative to the tray body, and positions the dosimeter.

[0008] The positioning frame may include a pair of vertical members extending in the longitudinal direction of the tray body and extending parallel to each other with a space therebetween that corresponds to the width of the dosimeter.

[0009] The positioning frame may further include a front member connected to a front end of each vertical member, extending perpendicular to each vertical member, and contacting the dosimeter to position the dosimeter in the longitudinal direction of the tray.

[0010] The positioning frame may further include a rear member connected to the rear end of each vertical member, extending perpendicular to each vertical member, and having a height lower than that of the front member so that the dosimeter can be placed on the tray body with a connector connected to the dosimeter.

[0011] The tray body and the pair of vertical members may both extend to the outside of the housing when the tray is installed inside the housing.

[0012] At least one side surface of the housing may be provided with an opening through which the tray can be inserted and removed. Effect of the Invention

[0013] According to the present invention, it is possible to provide a collimator that is used for half-value layer measurement using the rotating irradiation method and that allows the dosimeter to be smoothly attached and detached. [Brief description of the drawings]

[0014] [Figure 1] 1 is a diagram for explaining a state in which half-value layer measurement is performed using a collimator according to an embodiment of the present invention. FIG. [Diagram 2] 1 is a perspective view showing a configuration of a collimator according to an embodiment of the present invention; [Diagram 3] 3 is an exploded perspective view showing the components of the collimator in FIG. 2. FIG. [Figure 4] 1 is a side view showing a state in which a dosimeter is slidably mounted on a tray installed in a housing of a collimator according to an embodiment of the present invention; FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a collimator according to an embodiment of the present invention will be described in detail with reference to the drawings. In each drawing, the same or equivalent parts are designated by the same reference numerals.

[0016] The collimator according to the embodiment is a collimator that blocks X-rays emitted from an X-ray source in a direction other than vertically downward from being irradiated onto a dosimeter installed on a bed in half-value layer measurement using a rotating irradiation method in a CT device. The rotating irradiation method is a half-value layer measurement method performed in a state where an X-ray source rotates around a rotation axis by a rotating ring. The vertically downward X-rays are X-rays emitted toward the center of a gantry from an X-ray source placed at the highest position by the rotating ring of the CT device.

[0017] 1, the CT device 1 in which the collimator 10 is installed includes a gantry 2 and a bed 3 arranged inside the gantry 2. The gantry 2 includes an X-ray source 21 that emits X-rays, an X-ray detector 22 that detects the X-rays emitted from the X-ray source 21, and a rotating ring 23 that supports the X-ray source 21 and the X-ray detector 22 rotatably around a rotation axis. The collimator 10 is installed on the bed 3 with a dosimeter 4 set therein, and in this state, half-value layer measurement is performed by the rotation irradiation method.

[0018] Next, the configuration of the collimator 10 according to the embodiment will be described with reference to FIGS. The collimator 10 is formed in a box shape using a material that blocks X-rays, and includes a box-shaped housing 11 that allows vertically downward X-rays emitted from the X-ray source 21 of the CT device 1 to pass through the upper member, and a tray 12 that is installed so as to be removable within the housing 11 and on which the dosimeter 4 is detachably placed. The dosimeter 4 is a unit formed in a long plate shape, and an area for detecting X-rays is provided on the upper side of the dosimeter 4. The dosimeter 4 is, for example, a semiconductor dosimeter.

[0019] The housing 11 is a box-like housing formed in a rectangular parallelepiped shape. An opening 11a is formed on one of the sides of the housing 11 to allow the tray 12 to be inserted and removed. The tray 12 inserted into the housing 11 through the opening 11a is pushed to the back of the housing 11 and placed on the bottom surface of the housing 11. A slit 11b is formed on the top surface of the housing 11 through which the vertically downward X-rays emitted from the X-ray source 21 can pass while the housing 11 is placed on the bed 3 of the CT device 1. The slit 11b is preferably formed to have substantially the same size and shape as the horizontal size and shape of the detector of the dosimeter 4 installed in the housing 11, and is formed, for example, in a rectangular shape.

[0020] A pair of guide members 11c are provided on the inside of both side surfaces of the housing 11, sandwiching the tray 12 between the bottom surface of the housing 11 and positioning the tray 12 in the up-down direction of the housing 11. The pair of guide members 11c extend in the front-rear direction of the housing 11 and are formed, for example, of an acrylic square rod. Each guide member 11c may be adhered to the inside of the side surface of the housing 11 with an adhesive.

[0021] The housing 11 is composed of, for example, a plurality of plate members 11A. The plate members 11A are an example of a member that blocks X-rays. Each plate member 11A has a three-layer structure in which an X-ray shielding plate 11B is sandwiched between a pair of cover plates 11C. The X-ray shielding plate 11B is, for example, a lead plate having a thickness of 3 mm. The cover plate 11C is a member that reinforces the X-ray shielding plate 11B so that it is not easily deformed by an external force, and is, for example, an acrylic plate having a thickness of 3 mm. An acrylic plate painted in a matte black color may be used as the outer cover plate 11C. This makes it easier to visually recognize the positioning laser beam in the visible wavelength range irradiated from the CT device 1 to the outer surface of the housing 11.

[0022] Linear markers L1 to L4 are provided on the outer surfaces of the top surface and both opposing side surfaces of the housing 11, and serve as reference lines used to align the detection sensitivity center of the dosimeter 4 installed in the collimator 10 with the isocenter of the CT device 1. The line marker L1 extends in the width direction of the slit 11b, and the line marker L2 extends in the longitudinal direction of the slit 11b, and they are perpendicular to each other at the center point of the slit 11b. The line marker L3 extends in the horizontal direction so as to coincide with the height of the detection sensitivity center of the dosimeter 4 set in the housing 11, and the line marker L4 extends downward from both ends of the line marker L1. The line markers L3 and L4 are also perpendicular to each other.

[0023] The distance between the slit 11b and the detector of the dosimeter 4 is preferably set so that the scattered ray components of the X-rays irradiated from the X-ray source 21 do not affect the half-value layer measurement value. Specifically, it is preferable to set the distance so that the relative error of the effective energy calculated based on the half-value layer measurement by the rotating irradiation method using the collimator 10 to the effective energy calculated based on the half-value layer measurement by the fixed irradiation method is preferably less than 3%, more preferably less than 2%, and further preferably less than 1%.

[0024] The tray 12 includes a tray body 13 that is placed in the housing 11 so as to be in contact with the lower plate member 11A of the housing 11, and a positioning frame 14 that is provided on the tray body 13 and guides the dosimeter 4 when the dosimeter 4 is moved relative to the tray body 13 and positions the dosimeter 4. The tray body 13 and the positioning frame 14 are bonded together, for example, with an adhesive.

[0025] The tray body 13 is a plate-like member having a rigidity such that it does not bend even when the dosimeter 4 is placed on it. The tray body 13 is formed of, for example, an acrylic plate. The tray body 13 is formed so that the width in the left-right direction decreases from the middle part toward the rear. The width of the tray body 13 is approximately the same as the width of the opening 11a of the housing 11, and the length in the longitudinal direction is longer than the depth in the front-rear direction inside the housing 11. Therefore, the tray body 13 extends to the outside of the housing 11 when the tray 12 is placed inside the housing 11, making it easy to pull out the tray 12 from inside the housing 11. Linear markers L5 and L6 that intersect with each other are provided on the surface of the upper surface part of the tray body 13. The linear markers L5 and L6 are for checking whether the detector of the dosimeter 4 is in the correct position when the dosimeter 4 is set in the positioning frame 14.

[0026] The positioning frame 14 includes a pair of vertical members 14a extending in the longitudinal direction of the tray body 13 and extending parallel to each other with a gap therebetween, a front member 14b connected to the front end of each vertical member 14a and extending in a direction perpendicular to each vertical member 14a, and a rear member 14c connected to the rear end of each vertical member 14a and extending in a direction perpendicular to each vertical member 14a. Each part of the positioning frame 14 has a rectangular cross section and is formed, for example, by cutting an acrylic square bar. In addition, in consideration of ease of attachment and detachment of the dosimeter 4, it is preferable that the height of each part of the positioning frame 14 is lower than the height of the dosimeter 4 within a range in which the dosimeter 4 can be positioned.

[0027] The pair of vertical members 14a are members for positioning the dosimeter 4 therebetween. The distance between the pair of vertical members 14a is set according to the width of the dosimeter 4, and this allows the dosimeter 4 to be positioned in the width direction of the tray main body 13. The pair of vertical members 14a are set so that the longitudinal length within the frame of the positioning frame 14 is the same length as the dosimeter 4, and the dosimeter 4 is prevented from shaking when placed within the frame by being sandwiched between the front member 14b and the rear member 14c. The pair of vertical members 14a extend to the outside of the housing 11 when the tray 12 is placed within the housing 11.

[0028] The front member 14b is a member with which the tip of the dosimeter 4 comes into contact to position the dosimeter 4 in the longitudinal direction of the tray 12. The front member 14b is installed so that the dosimeter 4 is set at a correct position in the longitudinal direction of the tray 12 with the tip of the tray 12 coming into contact with the plate member 11A at the rear side inside the housing 11.

[0029] The rear member 14c is provided so as to prevent the dosimeter 4 from falling off backward. The height of the rear member 14c is made lower than the front member 14b so that the dosimeter 4 can be set in the positioning frame 14 with a connector (not shown) connected to the dosimeter 4. The connector is, for example, a Universal Serial Bus (USB) connector. This allows half-value layer measurement to be performed while power supply and data communication are performed via the connector connected to the dosimeter 4. The above is the configuration of the collimator 10.

[0030] Next, a flow of a half-value layer measuring method executed by a user using the collimator 10 according to the embodiment will be described. First, the tray 12 is placed in the housing 11, and then the dosimeter 4 is placed on the tray 12 so as to be set in the positioning frame 14. Specifically, first, the tray 12 is slid until the front end of the tray 12 contacts the plate member 11A at the rear side of the housing 11. Next, as shown in FIG. 4, the tip of the dosimeter 4 is placed between the pair of vertical members 14a while tilting so that the tip of the dosimeter 4 contacts the tray main body 13. By sliding the dosimeter 4 in this state until the tip of the dosimeter 4 contacts the front member 14b, the dosimeter 4 can be positioned in the longitudinal direction and the width direction of the tray main body 13 without the dosimeter 4 contacting the inner surface of the housing 11. This allows the tray 12 to be attached to the housing 11 with a simple operation.

[0031] Next, the collimator 10 with the dosimeter 4 installed is placed on the bed 3 so that the detection sensitivity center of the dosimeter 4 coincides with the isocenter of the CT device 1. The collimator 10 is placed on the bed 3 so that the opening 11a of the housing 11 faces the longitudinal direction of the bed 3. To align the detection sensitivity center of the dosimeter 4 with the isocenter of the CT device 1, the linear markers L1 to L4 provided on the outer surface of the housing 11 are aligned with the positioning laser beam emitted from the CT device 1.

[0032] Next, the CT device 1 is started to measure the dose of X-rays incident on the dosimeter 4 from the X-ray source 21. At this time, the X-ray source 21 rotates by the rotating ring 23, and the direction of the X-rays emitted from the X-ray source 21 changes from moment to moment, but since the dosimeter 4 is covered by the collimator 10 having the slit 11b, only the vertically downward X-rays that can pass through the slit 11b are incident on the dosimeter 4. At this time, data communication is performed with a computer via a connector connected to the dosimeter 4, and the computer is made to read the measured dose. Then, it is preferable to use the computer to calculate a half-value layer measured value based on the measured dose.

[0033] After the dose measurement is completed, the dosimeter 4 is removed from the collimator 10. At this time, even if the tray 12 is left inside the housing 11, the dosimeter 4 can be easily removed from the collimator 10 without the dosimeter 4 coming into contact with the inner surface of the housing 11 by lifting the base end of the dosimeter 4 and sliding the dosimeter 4 backward relative to the tray 12. The above is the flow of the half-value layer measurement method.

[0034] As described above, the collimator 10 according to the embodiment includes a box-shaped housing 11 formed of plate members 11A, with the plate member 11A on the upper surface side provided with a slit 11b for passing vertically downward X-rays emitted from the X-ray source 21 of the CT device 1, and a tray 12 that is installed so as to be removable within the housing 11 and on which the dosimeter 4 is detachably placed. The tray 12 includes a tray body 13 installed within the housing 11, and a positioning frame 14 that is provided on the tray body 13 and serves to guide the dosimeter 4 when it is moved relative to the tray body 13 and to position the dosimeter 4. This allows the dosimeter 4 to be smoothly attached to and detached from the collimator 10.

[0035] The present invention is not limited to the above-described embodiment, and the following modifications are possible.

[0036] (Modification) In the above embodiment, the housing 11 is formed by assembling a plurality of plate members 11A, but the present invention is not limited to this. For example, the upper surface, the lower surface, both side surfaces, and the front surface of the housing 11 may be entirely or partially molded as a single unit.

[0037] In the above embodiment, the opening 11a is provided on one side of the housing 11, but the present invention is not limited to this. For example, an opening the same as or equivalent to the opening 11a may be provided on the side of the housing 11 opposite the opening 11a, so that the housing 11 is configured into a cylindrical shape. In this case, it is preferable to provide a stopper in either opening for positioning the tray 12 in the front-rear direction of the housing 11.

[0038] In the above embodiment, the tray 12 is inserted and removed through the opening 11a of the housing 11, but the present invention is not limited to this. For example, a hinge may be attached to the end of the side surface of the housing 11 so that the plate member 11A of the side surface can be opened and closed. Also, the plate members 11A of the top surface, both side surfaces, and the front surface of the housing 11 may be integrated, and this integrated member may be placed over the tray 12 on which the dosimeter 4 is placed. In addition, instead of the housing 11, a lid-shaped member formed by integrating the plate members 11A of the top surface, both side surfaces, the front surface, and the rear surface may be used, and this lid-shaped member may be placed over the tray 12 on which the dosimeter 4 is placed.

[0039] In the above embodiment, the tray 12 is configured to be detachable from the housing 11, but the present invention is not limited to this. For example, the tray 12 may remain fixed in the housing 11.

[0040] In the above embodiment, the plate member 11A constituting the housing 11 has a three-layer structure, but the present invention is not limited to this. For example, if there is no problem with the strength of the X-ray shielding plate 11B, either or both of the inner and outer cover plates 11C may be omitted.

[0041] In the above embodiment, the tray body 13 of the tray 12 is formed so that the width in the left-right direction decreases from the middle part toward the rear, but the present invention is not limited to this. For example, the tray body 13 may be a rectangular plate.

[0042] In the above embodiment, the longitudinal length of the positioning frame 14 within the frame is longer than the dosimeter 4, but the present invention is not limited to this. For example, the longitudinal length of the positioning frame 14 within the frame may be made equal to that of the dosimeter 4, and the dosimeter 4 may be positioned in the longitudinal direction of the tray body 13 by the front member 14b and the rear member 14c.

[0043] In the above embodiment, the vertical member 14a, the front member 14b, and the rear member 14c have a rectangular cross-sectional shape, but the present invention is not limited to this. For example, the vertical member 14a, the front member 14b, and the rear member 14c may have a circular cross-sectional shape.

[0044] In the above embodiment, the front member 14b and the rear member 14c are each a single elongated member, but the present invention is not limited to this. For example, the front member 14b and the rear member 14c may each be composed of a plurality of members, such as pins.

[0045] In the above embodiment, the height of the rear member 14c is formed to be lower than the front member 14b, but the present invention is not limited to this. For example, if there is no need to connect a connector to the dosimeter 4, the height of the rear member 14c may be the same as the height of the front member 14b.

[0046] In the above embodiment, first, the tray 12 is placed in the housing 11, and then the dosimeter 4 is placed on the tray 12 so as to be set in the positioning frame 14. However, the present invention is not limited to this. First, the dosimeter 4 may be placed on the tray 12 so as to be set in the positioning frame 14, and then the tray 12 on which the dosimeter 4 is set may be placed in the housing 11.

[0047] The above-mentioned embodiments are merely examples, and the present invention is not limited to these, and various embodiments are possible within the scope of the invention described in the utility model registration claims. The components described in the embodiments and modifications can be freely combined. In addition, the present invention also includes devices equivalent to the devices described in the utility model registration claims. [Explanation of symbols]

[0048] 1 CT device 2 Gantry 3 berths 4. Dosimeter 21 X-ray source 22 X-ray detector 23 Rotating Ring 10 Collimator 11. Cabinet 11a opening 11b Slit 11c Guide member 11A Plate member 11B X-ray shielding plate 11C Cover plate 12 Tray 13 Tray body 14 Positioning frame 14a Vertical member 14b Front member 14c Rear part 21 X-ray source 22 X-ray detector 23 Rotating Ring

Claims

1. A collimator used in half-value layer measurement using a CT scanner with a rotating irradiation method, a box-shaped housing formed of an X-ray shielding member, the box-shaped housing having a slit on an upper surface side thereof for passing vertically downward X-rays emitted from an X-ray source of the CT device; a tray that is removably installed in the housing and on which a dosimeter is detachably placed, the tray includes a tray body that is installed in the housing, and a positioning frame that is provided on the tray body, guides the dosimeter when the dosimeter is moved relative to the tray body, and positions the dosimeter. Collimator.

2. The positioning frame includes a pair of vertical members extending in the longitudinal direction of the tray body and extending parallel to each other with a space therebetween in accordance with the width of the dosimeter.

2. The collimator of claim 1.

3. the positioning frame further includes a front member connected to a front end of each vertical member, extending in a direction perpendicular to each vertical member, and contacting the dosimeter to position the dosimeter in the longitudinal direction of the tray; 3. The collimator of claim 2.

4. the positioning frame further includes a rear member connected to a rear end of each of the vertical members, extending in a direction perpendicular to each of the vertical members, and having a height lower than that of the front member so that the dosimeter can be placed on the tray body with a connector connected to the dosimeter.

4. The collimator of claim 3.

5. the tray body and the pair of vertical members each extend to the outside of the housing when the tray is installed inside the housing; 3. The collimator of claim 2.

6. At least one side surface of the housing is provided with an opening through which the tray can be inserted and removed. A collimator according to any one of claims 1 to 5.

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