JP6823310B2 - Exposure dose control method and control device - Google Patents

Description

The present invention, when performing photographing for examination and diagnosis by administering radiopharmaceuticals, measures the internal exposure of the subject, to a method for management and the management device.

In recent years, with the widespread use of radiation-based examination devices such as CT and PET, there has been increasing interest in radiation exposure associated with medical practice. For exposure, it is necessary to record the type, energy, and location of the irradiated radiation and manage its effects over a long period of time. With regard to external exposure due to radiation emitted from outside the body, a technique for measuring and managing the exposure dose has been conventionally known.

Patent Document 1 discloses a management system for an exposure dose accumulated by a plurality of irradiations. The exposure dose management system of Patent Document 1 stores skin exposure dose and organ exposure dose in association with a three-dimensional image of the human body. However, the exposure dose for each organ is treated as already measured data, and the technique for specifying the exposure dose for each organ is not disclosed. Patent Document 2 discloses an image processing technique relating to image segmentation and contour display of a subject undergoing radiotherapy. The image processed by the technique of Patent Document 2 is used for estimating and recording the exposure distribution. Patent Document 3 discloses a technique for measuring an exposed area dose and an absorbed area dose. In the technique described in Patent Document 3, the exposed area dose is calculated from the area of the irradiation area of radiation, the area of the subject area, and the effective dose of the radiation source. Patent Document 4 discloses an exposure dosimeter that measures neutrons having a specific energy with high sensitivity. Patent Document 5 discloses an exposure dosimeter including a detector that reacts to relatively high-energy neutrons and a detector that reacts to relatively low-energy neutrons.

Further, as a dose evaluation method developed by the MIRD Committee (Medical International Radiation Dose Committee), the "MIRD method" disclosed in Non-Patent Document 1 is known. The MIRD method is a method of estimating the dose distribution by performing computer simulation using a simulated human body, and is widely used as a world standard method.

In Non-Patent Document 2 and Non-Patent Document 3, the organ region of a subject is automatically discriminated by using an image in which a tissue in the body of the subject is photographed, such as an X-ray image, a CT image, and an MRI image. The technology is disclosed.

Japanese Unexamined Patent Publication No. 2014-11478 JP-A-2008-508977 Japanese Unexamined Patent Publication No. 2004-069441 Japanese Unexamined Patent Publication No. 2000-147129 Japanese Unexamined Patent Publication No. 2-205792

Snyder WS, Fisher HL, Jr., Ford MR, Warner GG. "Estimates of absorbed fractions for monoenergetic photon sources uniformly distributed in various organs of a heterogeneous phantom." J Nucl Med. 1969: Suppl 3: 7-52. PubMed PMID : 5802194. X.Zhou, T.Ito, X.Zhou, H.Chen, T.Hara, R.Yokoyama, M.Kanematsu, H.Hoshi, and H.Fujita "A universal approach for automatic organ segmentations on 3D CT images based on organ localization and 3D GrabCut "Proc. Of SPIE Medical Imaging 2014: Computer-Aided Diagnosis, 9035, 90352V-1 --9035V-8, (2014). X.Zhou, S.Morita, X.Zhou, H.Chen, T.Hara, R.Yokoyama, M.Kanematsu, H.Hoshi, and H.Fujita "Automatic anatomy partitioning of the torso region on CT images by using multiple organ localizations with a group-wise calibration technique ”Proc. Of SPIE Medical Imaging 2015: Computer-Aided Diagnosis, edited by LMHadjiiski and GDTourassi, Vol.9414, 94143K-1 --94143K-6, (2015).

Techniques for detecting and controlling external exposure doses emitted from external radiation sources have been conventionally known. However, with regard to the internal exposure dose when a radiopharmaceutical is administered, a method of estimating the exposure dose based on the ICRP survey results has been widely adopted. Until now, no technique has been known for accurately detecting the internal exposure dose for each organ after the examination from the actual image of the subject to whom the radiation source was administered.

The present invention has been made in view of such a situation, and provides an apparatus and a method for accurately measuring and managing the internal exposure dose of a subject who has been administered a radiopharmaceutical for each organ. I am aiming.

The present invention relates to an exposure dose control method. The exposure dose management method of the present invention includes a step of taking a morphological image of a subject and a step of discriminating an organ from the morphological image and storing organ region information including the position and dimensions of the organ. Further, the method of the present invention is a step of administering a radioactive drug to a subject and taking a functional image showing the accumulation degree of the radioactive drug in the body, and the accumulation degree of the radioactive drug in a region corresponding to the whole body of the subject from this functional image. The radioactivity per unit of the degree of accumulation is calculated by adding up the values of and dividing the dose of the radiopharmaceutical by the obtained total value. Then, based on the organ area information, the value of the accumulation degree for each organ is extracted from the functional image and added up to obtain the total organ accumulation degree value, and the radioactivity per unit of the accumulation degree is the total organ accumulation degree value. By multiplying by, the amount of radioactivity for each organ is calculated, and the exposure dose for each organ is obtained from the amount of radioactivity, and the exposure dose for each organ is managed for each subject. It is characterized by being.

(Delete)

The present invention also provides an exposure dose control device. The exposure dose management device of the present invention discriminates an organ from a morphological image of a subject and stores it as organ region information including the position and dimensions of the organ, and an organ region discriminating means, and a subject to which a radioactive drug is administered is photographed to capture the subject. The exposure dose for each organ of the subject is measured and managed from the imaging means for taking a functional image showing the accumulation degree of the radioactive drug in the body, the organ area information of the morphological image and the value of the accumulation degree of the radioactive drug in the functional image. It is equipped with an exposure dose measurement management means. In the exposure dose management device of the present invention, the exposure dose measurement management means calculates the radioactivity per unit of the degree of accumulation of the radiopharmaceutical from the morphological image and the functional image, and the organ from the functional image using the organ region information. A means for extracting the total value of the degree of accumulation for each degree, and the exposure dose for each organ from the amount of radioactivity for each organ calculated by multiplying the total value of the degree of accumulation for each organ by the radioactivity per unit of the degree of accumulation. It is characterized in that it is provided with a means for obtaining the radiation dose and a means for managing the exposure dose for each subject for each subject.

With the exposure dose management method and the exposure dose management device of the present invention, the internal exposure dose of a subject can be measured by using an actual functional image of the subject to which the radiopharmaceutical is administered. Compared with the conventional method for estimating the internal exposure dose, it is possible to obtain a highly accurate measurement result of the internal exposure dose for each organ.

By obtaining the measurement results of the internal exposure dose for each organ, it becomes possible to manage the exposure history of the subject for each organ. In addition, it is possible to manage the exposure dose by different types of examinations and diagnostic devices, and to manage the exposure dose by adding it to the external exposure dose. It also makes it possible to manage exposure doses through different testing and medical institutions.

FIG. 1 is a block diagram schematically showing a configuration of an exposure dose management device according to the present invention. FIG. 2 is a flowchart of the exposure dose management method according to the first embodiment. FIG. 3 is a flowchart of the exposure dose management method according to the second embodiment. FIG. 4 is a drawing substitute photograph showing an example of a morphological image of a subject. FIG. 5 is a drawing substitute photograph showing a state in which an organ is discriminated on a morphological image and displayed in a different color scheme. FIG. 6 is a drawing substitute photograph showing an example of the functional image of the subject. FIG. 7 is a drawing substitute photograph showing a state in which an image of an organ is mapped on a functional image and displayed in a different color for each organ. FIG. 8 is a drawing substitute photograph showing an output screen of the measurement result of the internal exposure dose for each organ of the subject.

Hereinafter, embodiments of a suitable exposure dose control device according to the present invention will be described with reference to the drawings. The morphological image referred to here is an image in which the position and shape of the tissue in the subject's body can be discriminated, and for example, an X-ray image, a CT image, an MRI image, etc. correspond to the morphological image. To do. On the other hand, a functional image is an image that reflects information on the physiological function or characteristics of the subject's body or metabolism, and an image taken by a gamma camera, a PET image (Positron Emission Tomography), or the like corresponds to the functional image. To do.

FIG. 1 is a block diagram schematically showing a suitable configuration of an exposure dose management device. The exposure dose management device 1 includes a morphological image capturing means 2, a functional image capturing means 3, and a computer 4. The functional imaging means 3 in the present embodiment is a means for photographing a subject to which a radioactive drug has been administered to obtain an image showing the degree of accumulation of the radioactive drug in the subject's body.

The storage means 6 of the computer 4 stores the organ region determination means 11, the exposure dose measuring means 12, and the exposure dose management means 13 in the form of an executable program.

The organ region determining means 11 receives the morphological image taken by the morphological image capturing means 2, and automatically determines the region of each organ in the morphological image based on the techniques disclosed in Non-Patent Document 2 and Non-Patent Document 3. Organ area information including the position and size of the organ is created and temporarily stored in the storage means.

The exposure dose measuring means 12 receives the functional image taken by the functional image capturing means 3 and reads the value of the degree of accumulation of the radioactive drug in the subject's body from the functional image. Then, the exposure dose for each organ is measured by using the read accumulation degree value and the organ region information of the corresponding subject created by the organ region discriminating means 11.

The exposure dose measuring means 12 extracts the total value of the accumulation degree for each organ from the functional image by using the calculation means for calculating the radioactivity per unit of the accumulation degree of the radiopharmaceutical using the functional image and the organ area information. It is provided with a means for calculating the exposure dose for each organ by multiplying the total value of the degree of accumulation for each organ by the radioactivity per unit of the degree of accumulation.

The exposure dose management means 13 stores attributes such as the age and gender of the subject and attributes such as the shooting date and time and shooting conditions of the image for each subject, and these data and the exposure dose associated with the image shooting are stored. Associate and aggregate. Then, the exposure dose of the organ is managed for each subject.

Hereinafter, the exposure dose management method using the exposure dose control apparatus 1 described in the embodiment of the present invention will be described in detail with reference to the drawings.

(Example 1)
In the exposure dose management method of this embodiment, a computer tomography apparatus using X-rays (hereinafter, also simply referred to as CT) is used for the morphological imaging means 2, and a positron emission tomography apparatus 3 is used for the functional imaging apparatus 3. An imaging device (hereinafter, also simply referred to as a PET device or PET) is used.

In this embodiment, a flow chart of exposure dose management method using the exposure dose control apparatus 1 shown in FIG. First, in step S1, CT is used to take a CT image of the subject, which is a morphological image. An example of the captured CT image is shown in FIG. 4 as a drawing substitute photograph. The CT image shown in FIG. 4 is a vertical cross-sectional grayscale image of a subject who is an adult male.

The captured morphological image is input to the computer 4, and the individual organs are discriminated by the organ region discriminating means 11. The organ region determination means 11 determines the boundaries of the organs shown in the image (step S2). Then, the position, size, and shape of each organ are specified and saved as organ area information (step S3). FIG. 5 shows a drawing-substituting photograph of a CT image processed so that each organ is displayed in a different color using the organ region information.

Next, a PET image, which is a functional image, is taken using the PET device (step S4). In this embodiment, a radiopharmaceutical is administered to a subject, photons are measured when the elements contained in the radiopharmaceutical are decayed in the body, and an image corresponding to the degree of accumulation of the radiopharmaceutical in the body is taken as a functional image. The PET apparatus of this embodiment outputs a value of SUV (standardized uptake value), which is one index of the degree of accumulation of radiopharmaceuticals, as a pixel value. The grayscale image created based on this pixel value is hereinafter referred to as an SUV image.

The SUV is a value obtained by correcting the radioactivity concentration by the dose and the body weight, which is represented by the following (Equation 1).
SUV = Detected radioactivity concentration ÷ (radioactivity dose ÷ body weight) ・ ・ ・ (Equation 1)

The value of the SUV is set to be "1" in any region of the whole body when the administered radiopharmaceutical is not excreted from the body and is uniformly distributed in the body. The actual SUV value reflects the difference in the degree of accumulation of the radiopharmaceutical for each organ, and also shows the individual difference in the accumulation location and the degree of accumulation for each subject. FIG. 6 shows a drawing substitute photograph of an SUV image as an example of a functional image. This image is an SUV image in which the same subject as the CT image of FIG. 4 is photographed by the functional image capturing means 3 and the SUV value is output as a difference in brightness. By inputting the data corresponding to the SUV image obtained here into the computer 4 and processing it, the exposure dose for each organ can be measured.

The processing by the exposure dose measuring means 12 using the SUV image data and the organ area information will be described below. In step S5, all the pixels in the region corresponding to the whole body of the subject in the SUV image are extracted, and the SUV which is the pixel value is added up. In this embodiment, threshold processing and morphology processing are performed on the SUV image in order to discriminate the region corresponding to the whole body from the SUV image (step S5). Then, the total value of the obtained SUVs is divided by the dose of the radiopharmaceutical administered to the subject. As a result, the radioactivity per unit of SUV, which is the degree of integration, can be obtained (step S6).

Next, in order to measure the exposure dose for each organ, the organ region information obtained in step S3 is superimposed on the SUV image. FIG. 7 shows an image processed so that the regions of each organ are displayed in different colors. For each organ, the pixel values of the corresponding regions of the SUV image are extracted and added up. As a result, the total data of the SUV values for each organ can be obtained (step S7). This total value is multiplied by the radioactivity per unit of integration degree (step S8). The result of the multiplication in step S8 gives the exposure dose for each organ.

Tables 1 to 3 below show the results of computer 4 processing of the amount of radioactivity for each organ, assuming that 400 MBq, which is the maximum dose of FDG, was administered to 3 subjects. ..

From the results shown in Tables 1 to 3 above, it was found that the radioactivity, volume, irradiation dose, and equivalent dose contained in each organ could be quantitatively measured for each subject. This clarified the exposure of each organ. It was also found that the exposure dose differs depending on the individual.

FIG. 8 shows a drawing substitute photograph in which the exposure dose for each organ is detected using the CT images and SUV images from FIGS. 4 to 7, and the cumulative result is output by integrating with the past exposure dose. Since the exposure dose for each organ is obtained with high accuracy for each subject, it is possible to integrate and accumulate the exposure dose at the time of past imaging and the exposure dose of different examinations, and manage the exposure dose for each organ of the subject. Is performed (step S9).

By the exposure dose management method using the exposure dose measuring device 1 of this embodiment, the internal exposure dose of the subject can be measured for each organ by using the actual SUV image of the subject to which the radiopharmaceutical is administered. Compared with the conventional internal exposure dose estimation method, it is possible to obtain a highly accurate measurement result of the internal exposure dose for each organ, and it becomes possible to verify individual differences for each subject. In addition, it is possible to perform unprecedented detailed management by integrating and accumulating the exposure dose for each organ in the past.

(Example 2)
In this embodiment, a method of measuring the exposure dose will be described in a different order from that of the first embodiment. The exposure dose management device 1 used is the same as that of the first embodiment. Further, regarding the exposure dose management method, the same step numbers as those in the first embodiment are assigned and duplicate explanations are omitted.

In this embodiment, the SUV image and the organ area information are input to the exposure dose measuring means 12, pixels of the area corresponding to each organ are extracted from the SUV image, and the SUV value which is the pixel value is added up. As a result, the total value of the accumulation degree of the radiopharmaceutical for each organ is obtained (step S11). Next, the total value of the SUV region of the region corresponding to the whole body of the SUV image is obtained by further summing all the total values of the SUVs for each organ (step S12). Then, the total value of the obtained SUVs is divided by the dose of the radiopharmaceutical administered to the subject. As a result, the radioactivity per unit of SUV, which is the degree of integration, can be obtained (step S6). The subsequent measurement method is the same as that of the first embodiment.

Although specific examples of the present invention have been described in detail based on Examples, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above, and also include design changes within a range that does not deviate from the gist of the present invention. For example, in the embodiment, the CT device and the PET device are used to acquire the morphological image and the functional image, respectively, but different devices can be used to acquire the images. For example, an X-ray imaging apparatus, an MRI apparatus, or the like can be used for photographing a morphological image. A gamma camera or the like can be used to capture a functional image. In addition, any known image processing method can be applied to the discrimination of the whole body region and the discrimination of the organs.

1 ・ ・ Exposure dose management device 2 ・ ・ Morphological image photographing means 3 ・ ・ Functional imaging means 4 ・ ・ Computer 6 ・ ・ Storage means 11 ・ ・ Organ area discrimination means 12 ・ ・ Exposure dose measuring means 13 ・ ・ Exposure dose management means

Claims (2)

The process of taking a morphological image of the subject and
A process of discriminating an organ from the morphological image and saving organ region information including the position and size of the organ,
A step of administering a radioactive drug to the subject and taking a functional image showing the degree of accumulation of the radioactive drug in the body, and
Radiation per unit of the degree of accumulation by adding up the values of the degree of accumulation of the radiopharmaceutical in the region corresponding to the whole body of the subject from the functional image and dividing the dose of the radioactivity drug by the obtained total value. The process of calculating the ability and
Based on the organ region information, the step of extracting the value of the degree of accumulation for each organ from the functional image and adding up the values to obtain the total value of the degree of accumulation of organs.
The process of calculating the amount of radioactivity for each organ by multiplying the total value of the degree of accumulation of the radioactivity per unit of the degree of accumulation , and obtaining the exposure dose for each organ from the amount of the radioactivity .
The process of managing the exposure dose for each organ for each subject,
An exposure dose management method characterized by being equipped with. An organ region discrimination means that discriminates an organ from a morphological image of a subject and saves it as organ region information including the position and dimensions of the organ.
A functional image photographing means for photographing the subject to which the radioactive drug was administered and taking a functional image showing the degree of accumulation of the radioactive drug in the subject's body.
An exposure dose measuring means for measuring an exposure dose for each organ of a subject from the organ region information of the morphological image and the value of the accumulation degree of the radiopharmaceutical in the functional image.
Exposure dose management means for managing the exposure dose of organs for each subject,
It is an exposure dose control device equipped with
The exposure dose measuring means uses the functional image to calculate the radioactivity per unit of the degree of accumulation of the radiopharmaceutical, and the organ area information is used to obtain the total value of the degree of accumulation for each organ from the functional image. And a means for obtaining the exposure dose for each organ from the amount of radioactivity for each organ calculated by multiplying the total value of the degree of accumulation for each organ by the radioactivity per unit of the degree of accumulation. An exposure dose control device characterized by being equipped with.