JP2008132147A - Method and device for determination of exposure dose - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly precisely determine total dose distribution of an X-ray radiation field without damaging real-time performance. <P>SOLUTION: Based on X-ray conditions set by an X-ray condition setting part 12, position information from an X-ray generating part 4 to a subject 2, and the X-ray radiation angle to the subject 2, the inside of an X-ray radiation field F is fractionated by a dose distribution operating part 13 to a plurality of fractions of a first stage (1st), a second stage (2st), ..., in order. Every time of fractionation, an X-ray dose is determined for each fraction, and the X-ray radiation doses are totalled to determine total dose distribution as the whole X-ray radiation field F to be displayed in a display 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an NDD (Non Dosimeter Dosimetry) method, and relates to an exposure dose calculation method and apparatus for calculating an exposure dose of a subject when the subject is irradiated with X-rays.

  The dose distribution of the X-rays irradiated to the patient based on the X-ray conditions of the X-ray tube that irradiates the patient with X-rays and mechanical position information such as the X-ray tube and the bed on which the patient is placed There is a technology to calculate. For example, Non-Patent Documents 1 to 5 disclose the NDD method as such a technique. In Non-Patent Document 1, the NDD method uses various factors (tube voltage, tube current, etc.) that influence the incident dose, for example, in order to estimate the patient's surface incident dose using the simple conversion formula for the patient's surface incident dose in the X-ray diagnostic region. The product mAs of the image and the imaging time, filtration, the difference between the focal point and the skin distance FSD, the apparatus) is normalized by a constant value, converted into a coefficient, and the surface dose estimation formula is derived. . In other words, in order to calculate the X-ray exposure dose to the patient with high accuracy, the X-ray exposure angle and X-ray intensity with respect to the patient and the distance between the X-ray tube and the patient are used to calculate the dose at each part of the patient. Each X-ray dose is calculated and calculated by a computer, and these X-ray doses are combined to determine the dose distribution of the entire X-ray irradiation field.

However, in order to obtain the dose distribution of the entire X-ray field with high accuracy, information such as the X-ray incident angle, X-ray intensity, and distance between the X-ray tube and the patient is used as described above. A large amount of information must be processed. For this reason, it takes time to complete the calculation of the dose distribution of the entire X-ray irradiation field, and it is difficult to obtain the dose distribution of the entire X-ray irradiation field in real time.
"About NDD method" Simple conversion formula (NDD method) of patient's surface incident dose in X-ray diagnosis area, Ibaraki X-ray Technician Association, website http://www.sunshine.ne.jp/~iart/ ndd.htm Takehiko Mori, et al. “Exposure doses based on X-ray diagnostic imaging conditions and proposal of guidance level in Japan” Journal of Japanese Medical X-ray Society Vo1.60: 389-395.2000 Takehiko Mori, et al. "Study on surface dose measurement and simple conversion method in X-ray diagnostic area" Ibaraki X-ray Engineers Association, Japan X-ray Technology Society Ibaraki Branch, Exposure Reduction Committee, 1990 Takehiko Mori, et al. “Study on fundamental factors of X-ray apparatus for deriving X-ray diagnostic area and simple conversion formula”, collection of basic data, Ibaraki Prefectural X-ray Engineers Association, Japan X-ray Technical Society Ibaraki Branch・ Exposure Reduction Committee, 1989 Takehiko Mori, Masao Tamura, Yukio Takahashi, Haruo Okamoto, Tsutomu Murata “Surface Dose Measurement and Simplified Conversion Method (1st-4th Report) in the X-ray Diagnosis Region”

  An object of the present invention is to provide an exposure dose calculation method and apparatus capable of obtaining a dose distribution of the entire X-ray irradiation field with high accuracy without impairing real-time properties.

  An exposure dose calculation method according to a main aspect of the present invention is a computer based on X-ray conditions when an X-ray is emitted from an X-ray generation source to the subject and positional information from the X-ray generation source to the subject. In the exposure dose calculation method for calculating the exposure dose of the subject by the calculation processing of X-ray, the X-ray irradiation field is subdivided into a plurality of regions sequentially in several stages, and before the X-ray irradiation field is subdivided and In each of the X-ray irradiation field and each of the plurality of regions, the X-ray irradiation dose of each specific portion is obtained, and the X-ray irradiation dose is obtained as each X-ray irradiation dose of the entire region, and before subdividing. The dose distribution of the entire X-ray irradiation field is obtained for each subdivision.

  An exposure dose calculation apparatus according to another main aspect of the present invention is based on X-ray conditions when an X-ray is emitted from an X-ray generation source to the subject, and positional information from the X-ray generation source to the subject. In the exposure dose calculation apparatus for calculating the exposure dose of the subject, the X-ray irradiation field is subdivided into a plurality of regions sequentially in several stages, and the X-ray irradiation field is subdivided before and after subdividing, respectively. Each X-ray irradiation dose for each specific part in the irradiation field and in a plurality of regions is obtained, and this X-ray irradiation dose is obtained as each X-ray irradiation dose for the entire region, and is subdivided before being subdivided. And a dose distribution calculation unit for obtaining a dose distribution of the entire X-ray irradiation field.

  ADVANTAGE OF THE INVENTION According to this invention, the exposure dose calculation method and its apparatus which can obtain | require the dose distribution of the whole X-ray irradiation field with high precision, without impairing real-time property can be provided.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram of an X-ray diagnostic apparatus to which an exposure dose calculation apparatus based on the NDD method is applied. This device is used as, for example, a circulatory system diagnosis system. A subject 2 such as a patient is placed on the bed 1. An X-ray generation unit 4 and an X-ray detection unit 5 are provided at each end of the C arm 3 so as to face each other.
The C arm 3 is provided with a mechanism portion 6. For example, the mechanism unit 6 rotates the C arm 3 and moves the C arm 3 in the longitudinal direction of the bed 1.

  The X-ray generation unit 4 has an X-ray generation source such as an X-ray tube that generates X-rays. A high voltage generator 7 is connected to the X-ray generator 4. The high voltage generator 7 applies a high voltage to the X-ray generator 4. The high voltage generator 7 receives an X-ray condition command from the system controller 8 and applies a high voltage corresponding to the X-ray intensity instructed by the X-ray condition command to the high voltage generator 5. As a result, the X-ray generation unit 4 generates X-rays.

  The X-ray detection unit 5 detects the X-ray dose emitted from the X-ray tube 15 and transmitted through the subject 2. The X-ray detection unit 5 includes, for example, a flat panel detector (FPD) or an I.I. (Image Intensifier).

  The image data generation unit 9 converts each electric charge read from the X-ray detection unit 5 into a digital image signal corresponding to the detected amount of X-rays to obtain projection data, and the X-ray image of the subject 2 is obtained from the projection data. Generate data. A display unit 10 having a plurality of monitor devices is connected to the image data generation unit 9. The display unit 10 displays the image data of the subject 2 generated by the image data generation unit 9.

The system control unit 8 controls the entire X-ray diagnostic apparatus. The system control unit 8 issues a movement command to the mechanism unit 6 and controls the X-ray intensity and the like for the high voltage generation unit 7. An X-ray condition command including a radiation time of the ray is issued, an X-ray irradiation command is issued to the X-ray generation unit 4, a drive command is issued to the X-ray detection unit 5, and various image data generation unit 9 is instructed. A calculation command is issued, and a display command is issued to the display unit 10.
An operation unit 11 is connected to the system control unit 8. The operation unit 11 is, for example, a mouse, a joystick, a drag ball, or the like, and outputs an operation signal corresponding to the operation of the mouse or the like.
The system control unit 8 includes a computer having a CPU, a RAM, a ROM, an input / output port, and the like. The system control unit 8 calculates the exposure dose of the subject when the subject is irradiated with X-rays by the NDD method. Unit 12 and dose distribution calculation unit 13.
The X-ray condition setting unit 12, for example, X-ray conditions when the subject 2 is irradiated with X-rays from the X-ray generation unit 4, position information from the X-ray generation unit 4 to the subject 2, and the subject 2 And the irradiation angle of the X-rays to be irradiated. The X-ray conditions are, for example, a high voltage supplied to the X-ray generation unit 4, a current, an X-ray emission time, and the like.

The dose distribution calculation unit 13 calculates the exposure dose of the subject 2 by performing a calculation process based on, for example, the X-ray conditions set in the X-ray condition setting unit 12, the position information, and the X-ray irradiation angle. .
Specifically, the dose distribution calculation unit 13 sequentially subdivides the X-ray irradiation field emitted from the X-ray generation unit 4 into a plurality of regions in several stages, and subdivides the X-ray irradiation field before subdividing. Each X-ray irradiation dose of each specific part is obtained in each X-ray irradiation field and in each of the plurality of regions, and this X-ray irradiation dose is obtained as each X-ray irradiation dose for each of the entire regions. The dose distribution of the entire X-ray irradiation field is obtained before and every time it is subdivided.

More specifically, the dose distribution calculation unit 13 obtains an X-ray irradiation dose of a specific part in the X-ray irradiation field before subdividing the X-ray irradiation field, and this X-ray irradiation dose is uniform over the entire X-ray irradiation field. As a result, the dose distribution of the entire X-ray irradiation field is obtained.
Each time the X-ray irradiation field is subdivided, the dose distribution calculation unit 13 calculates a dose distribution of the entire X-ray irradiation field according to the subdivision stage from each X-ray irradiation dose determined for each of a plurality of regions.
The dose distribution calculation unit 13 obtains the dose distribution of the entire X-ray irradiation field using the specific part in the X-ray irradiation field as the central part of the X-ray irradiation field.
The dose distribution calculation unit 13 obtains each dose distribution of each entire region by using each specific portion in each of the plurality of regions as each central portion of the plurality of regions.
The dose distribution calculation unit 13 obtains an X-ray dose distribution based on the X-ray condition of the X-ray generation unit 4 and the X-ray irradiation position information on the subject 2 set by the X-ray condition setting unit 12.

Next, exposure dose calculation by the NDD method in the apparatus configured as described above will be described.
In the circulatory system diagnosis system, for example, the heart and coronary artery of the subject 2 are imaged. Prior to this contrast, the exposure dose to the subject 2 is calculated in advance. FIG. 2 shows an example of the X-ray field F for the model M of the subject 2.
The X-ray condition setting unit 12, for example, X-ray conditions when the subject 2 is irradiated with X-rays from the X-ray generation unit 4, for example, high voltage, current, and X-ray emission time supplied to the X-ray generation unit 4. Etc. are set. At the same time, the X-ray condition setting unit 12 sets, for example, position information from the X-ray generation unit 4 to the subject 2 and an irradiation angle of the X-rays irradiated on the subject 2.

The dose distribution calculation unit 13 performs calculation processing by the NDD method based on, for example, the X-ray conditions set in the X-ray condition setting unit 12, the position information, and the X-ray irradiation angle, and the exposure dose of the subject 2 Is calculated. That is, the dose distribution calculation unit 13 obtains the X-ray irradiation dose of a specific portion in the X-ray irradiation field, for example, the central portion C of the X-ray irradiation field as shown in FIG. irradiation dose determining the dose distribution D ₁ of the X-ray irradiation field F as a whole is uniformly irradiated to the entire X-ray irradiation field F. In this case the dose distribution calculation unit 13 obtains the dose distribution D ₁ of the entire X-ray irradiation field by using the NDD method.

The dose distribution calculation unit 13 sends the obtained dose distribution D _{1 of the} entire X-ray irradiation field F to the display unit 10. The display unit 10 receives the dose distribution D ₁ of the entire X-ray irradiation field F, displays the dose distribution D ₁ of the entire X-ray irradiation field F. Thereby, a typical X-ray irradiation dose in the X-ray irradiation field F, that is, a typical exposure dose to the subject 2 is known.
Then, the dose distribution calculation unit 13 divides the X-ray irradiation field in F as the second stage (2st) a plurality of regions, for example, equally nine in each area e ₁ to e ₉ in the XY direction. The dose distribution calculation unit 13 sets the X-ray irradiation dose in the central region e ₁ as the dose distribution D ₁ obtained in the first stage (1st). Dose distribution calculation unit 13 with which, for each of the regions _e 2 to e ₉ adjacent the periphery of the central region _{e 1,} each specific portions in the respective regions _e 2 to e _9, for instance the areas _e 2 to e ₉ , X-ray irradiation doses of the central portions C _{2 to} C ₉ are obtained, and the doses of the respective regions e _{2 to} e ₉ are assumed to be uniformly irradiated on the entire regions e _{2 to} e ₉ . Find the distribution. Incidentally, FIG. 3 is the central part _C 2 -C ₉ in each area _e 2 to e ₉
To complicated To illustrate the show only the central portion C ₂ of the region e ₂ in.
However, the dose distribution calculation unit 13 calculates the dose distribution _{D 1} of the central region _{e 1,} the X-ray irradiation field F overall dose distribution _{D 2} together with the dose distribution of the areas _e 2 to e _9. The dose distribution calculation unit 13, similarly to the above, and sends the X-ray irradiation field F overall dose distribution D ₂ on the display unit 10. Thus, the display unit 10, the dose distribution D ₂ of the entire X-ray irradiation field F in the case of subdivision is displayed, for example, nine of the regions e ₁ to e _9. Thus, each representative X-ray dose in each area e ₁ to e ₉ when the subdivision, that is, each representative exposure dose to the subject 2 can be seen, for example, nine of the regions e ₁ to e _9.
Next, the dose distribution calculation unit 13 further performs XY on the X-ray irradiation field F as the third stage (3st) and further XY each of the areas e _{1 to} e ₉ divided in the second stage (2st), for example. The X-ray irradiation field F is subdivided into, for example, 81 regions f _{1 to} f ₈₁ , which are divided into nine regions equally in the direction.

Dose distribution calculation unit 13, the second stage (2st) 9 one of the regions corresponding to the divided e.g. central area _{e 1} in _{f 31, f 32, ...,} X -ray dose in the central area _{f 41} in _{f 51} Is C. This X-ray irradiation dose C is the same as the X-ray irradiation dose C obtained in the first stage (1st). Dose distribution calculation unit 13 with which, each area _f 31 adjacent the periphery of the central area _{f 41,} f 32, _..., for each _{f 51,} the respective regions _{f 31,} f 32, _..., each in the _{f 51} specific portion, e.g., the regions _{f 31,} f 32, _..., determine the respective X-ray irradiation dose in the center portion of the _{f 51,} these X-ray irradiation dose each area _{f 31,} f 32, _..., uniform whole _{f 51} , Each dose distribution of each region f ₃₁ , f ₃₂ ,..., F ₅₁ is obtained.

Hereinafter, similarly, the dose distribution calculation unit 13 sets each central portion for each region f ₁ , f ₂ ,..., F ₈₁ corresponding to each region e _{2 to} e ₉ divided in the second stage (2st). obtains an X-ray irradiation dose, these X-ray irradiation dose each area _{f 1,} f 2, _..., each area _f 1 as being uniformly irradiated to the whole of _{f 81,} f 2, _..., each dose distribution _{f 81} Ask for.
However, the dose distribution calculation unit 13 obtains the dose distribution D _{3 of the} entire X-ray irradiation field F by combining the subdivided regions f ₁ , f ₂ ,..., F ₈₁ . The dose distribution calculation unit 13, similarly to the above, and sends the dose distribution D ₃ of the entire X-ray irradiation field F on the display unit 10. Thus, the display unit 10, for example, 81 pieces of each area _{f 1,} f 2, _..., X-ray irradiation field F overall dose distribution _{D 3} in the case of subdivided into _{f 81} is displayed. Thus, for example, 81 pieces of each area _{f 1,} f 2, _..., each region _{f 1,} f 2 when segmented by _{f 81, ...,} each representative X-ray irradiation dose in _{f 81,} i.e. the subject Each representative exposure dose for 2 is known.
Thereafter, the dose distribution calculation unit 13 further subdivides the X-ray irradiation field F into a plurality of regions, obtains each X-ray irradiation dose for each of the subdivided regions, and combines these X-ray irradiation doses into the X-ray irradiation dose. The dose distribution of the whole irradiation field F is obtained. The dose distribution of the entire X-ray irradiation field F is displayed on the display unit 10.

  In the circulatory system diagnosis system, for example, when imaging the heart and coronary artery of the subject 2 in order to diagnose the subject 2, the X-ray irradiation angle with respect to the subject 2 and the relationship between the subject 2 and the X-ray tube 15 The distance, the position of the subject 2, that is, the position of the bed 3 are variously changed. Therefore, even when the exposure dose of the subject 2 is calculated by the NDD method, the exposure dose of the subject 2 is calculated by changing and setting the X-ray condition, position information, and X-ray irradiation angle.

  That is, the X-ray condition setting unit 12, for example, X-ray conditions when the subject 2 is irradiated with X-rays from the X-ray generation unit 4, for example, high voltage, current, and X-rays supplied to the X-ray generation unit 4. Change and set the radiation time. At the same time, the X-ray condition setting unit 12 changes and sets, for example, position information from the X-ray generation unit 4 to the subject 2 and an irradiation angle of the X-rays irradiated to the subject 2.

For example, the dose distribution calculation unit 13 performs the calculation process by the NDD method similarly to the above based on the X-ray condition, position information, and X-ray irradiation angle changed and set in the X-ray condition setting unit 12, and An exposure dose, for example, a dose distribution of the entire X-ray irradiation field H is obtained.
As described above, according to the above-described embodiment, the X-ray irradiation field F is subdivided into a plurality of regions in order, such as the first stage (1st), the second stage (2st),. Each X-ray irradiation dose is obtained for each region, and these X-ray irradiation doses are combined to obtain a dose distribution of the entire X-ray irradiation field F and displayed on each monitor device 26. Thus, it is possible to grasp the example schematic distribution state of the exposure dose of X-ray irradiation field F overall dose distribution D ₁ from the subject 2 displayed in the first stage (1st), second stage (2st ) can be grasped some trends dose distribution from the X-ray irradiation field F overall dose distribution D ₂ represented by. Accordingly, if the number of stages for subdividing the X-ray field F increases with time without waiting for the completion of the calculation process for obtaining a highly accurate dose distribution of the entire X-ray field F, the exposure of the subject 2 is increased. Details of dose distribution can be grasped with high accuracy.

  On the other hand, for each stage, an X-ray irradiation dose is obtained at an X-ray irradiation field F or a specific portion in each subdivided region, for example, an X-ray irradiation field or each central portion of each region. Since the X-ray irradiation dose is obtained on the assumption that the entire irradiation field F and each region are uniformly irradiated, the dose distribution of the entire X-ray irradiation field F, that is, the exposure dose of the subject 2 can be obtained with a small amount of data processing at each stage. Distribution can be obtained.

  Therefore, the dose distribution of the entire X-ray irradiation field can be obtained with high accuracy without impairing real-time properties. The distribution of the exposure dose of the subject 2 can be measured in a short time without reaching the number of subdivision stages for obtaining the distribution of the exposure dose of the subject 2 with an accuracy equivalent to the accuracy calculated in the past. The distribution of exposure dose can be grasped.

In addition, this invention is not limited to the said one Embodiment, You may deform | transform as follows.
For example, the specific portion in the X-ray irradiation field F or each subdivided region is, for example, the X-ray irradiation field or each central portion of each region. The part having the highest X-ray irradiation dose in the region is determined, and the X-ray irradiation field F or the entire region is assumed to be uniformly irradiated to the X-ray irradiation field F or the entire region. The dose distribution may be obtained. The specific portion in the X-ray irradiation field F may be a specific region of interest (ROI) in the subject 2.

The exposure dose calculation apparatus of the present invention has been described for the case where it is applied to the X-ray diagnosis apparatus used in the circulatory system diagnosis system. However, the present invention is not limited to this, and the head / abdomen angiography system, head diagnosis system, respiratory apparatus The present invention is applicable to various systems necessary for grasping the distribution of exposure dose of the subject 2 such as a system diagnosis system.
The size and the number of subdivisions of each region when subdividing the X-ray irradiation field F into a plurality of regions can be arbitrarily set.

The block block diagram which shows 1st Embodiment of the X-ray diagnostic apparatus to which the exposure dose calculation apparatus which concerns on this invention is applied. The figure which shows an example of the X-ray irradiation field with respect to the model of a subject. The schematic diagram which shows dose distribution of the whole X-ray irradiation field calculated | required every time an X-ray irradiation field is subdivided.

Explanation of symbols

  1: bed, 2: subject, 3: C arm, 4: X-ray generation unit, 5: X-ray detection unit, 6: mechanism unit, 7: high voltage generation unit, 8: system control unit, 9: image data Generation unit, 10: display unit, 11: operation unit, 12: X-ray condition setting unit, 13: dose distribution calculation unit.

Claims (11)

Based on the X-ray conditions when the subject is irradiated with X-rays from the X-ray generation source and the positional information from the X-ray generation source to the subject, the amount of exposure of the subject is calculated by computer processing In the exposure dose calculation method to
The X-ray irradiation field is subdivided into a plurality of regions sequentially in several stages, and before the X-ray irradiation field is subdivided and every time it is subdivided, the X-ray irradiation field and the plurality of regions respectively. The X-ray irradiation dose of each specific part is obtained, and this X-ray irradiation dose is obtained as each X-ray irradiation dose of the entire area, and the X-ray irradiation is performed before and after the subdivision. Find the dose distribution of the whole field,
A method for calculating an exposure dose. The X-ray irradiation dose of the specific portion in the X-ray irradiation field is obtained, and the dose distribution of the entire X-ray irradiation field is obtained assuming that the X-ray irradiation dose is uniformly applied to the entire X-ray irradiation field.
Every time the X-ray irradiation field is subdivided, the dose distribution of the entire X-ray irradiation field according to the subdivision stage is determined from the X-ray irradiation doses determined for each of the plurality of regions.
The exposure dose calculation method according to claim 1.   2. The exposure dose calculation method according to claim 1, wherein the specific portion in the X-ray irradiation field is a central portion of the X-ray irradiation field.   2. The exposure dose calculation method according to claim 1, wherein each of the specific portions in the plurality of regions is a central portion of the plurality of regions.   2. The X-ray irradiation dose is obtained based on at least one of or both of the X-ray condition for irradiating the X-ray and irradiation position information of the X-ray irradiated to the subject. The exposure dose calculation method described. An exposure dose calculation device that calculates an exposure dose of the subject based on X-ray conditions when the subject is irradiated with X-rays from the X-ray generation source and position information from the X-ray generation source to the subject In
The X-ray irradiation field is sequentially subdivided into a plurality of regions in several stages, and before the X-ray irradiation field is subdivided and every time it is subdivided, in the X-ray irradiation field and in the plurality of regions, respectively. Each X-ray irradiation dose with each specific portion is obtained, and this X-ray irradiation dose is obtained as each X-ray irradiation dose for the entire region, and the X-ray irradiation is performed before and after the subdivision. A dose distribution calculation unit for determining the dose distribution of the entire field,
An apparatus for calculating an exposure dose. The dose distribution calculation unit obtains the X-ray irradiation dose of the specific portion in the X-ray irradiation field before subdividing the X-ray irradiation field, and the X-ray irradiation dose is uniformly distributed over the entire X-ray irradiation field. Obtain the dose distribution of the entire X-ray field as being irradiated,
Every time the X-ray irradiation field is subdivided, the dose distribution of the entire X-ray irradiation field according to the subdivision stage is determined from the X-ray irradiation doses determined for each of the plurality of regions.
The exposure dose calculation apparatus according to claim 6.   The dose calculation unit according to claim 6, wherein the dose distribution calculation unit obtains a dose distribution of the entire X-ray irradiation field using the specific portion in the X-ray irradiation field as a central portion of the X-ray irradiation field. apparatus.   The dose calculation unit according to claim 6, wherein the dose distribution calculation unit obtains each dose distribution of each of the plurality of regions by using the specific portions in the plurality of regions as central portions of the plurality of regions. apparatus.   The dose distribution calculation unit obtains the X-ray irradiation dose based on at least one of or both of a condition for emitting the X-ray from the X-ray source and irradiation position information of the X-ray irradiated to the subject. The exposure dose calculation apparatus according to claim 6. The X-ray source has an X-ray tube that emits X-rays;
An X-ray stop for reducing the X-rays emitted from the X-ray tube;
A bed on which the subject is placed;
An X-ray detector for detecting the X-ray dose emitted from the X-ray tube and transmitted through the subject;
An irradiation position calculation unit for obtaining irradiation position information of the X-ray irradiated to the subject based on each position information of at least the X-ray tube and the bed;
The dose distribution calculation unit obtains the X-ray dose distribution based on the X-ray condition of the X-ray tube and the irradiation position information calculated by the irradiation position calculation unit;
The exposure dose calculation apparatus according to claim 6.

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