JP2022126995A - Program, image processing device and image processing method - Google Patents

Abstract

To enable improvement in diagnostic accuracy while reducing the burden on a subject.SOLUTION: Based on a reference pixel value which is a maximum pixel value of an area corresponding to the upper side of the center of a heart in a tomographic image data before smoothing processing is performed, a setting part 3 sets a region where the myocardial distribution of a radiopharmaceutical accumulated in the myocardium is copied to the tomographic image data as a region of interest. An extraction part 4 extracts the myocardial tomographic image data showing the myocardial distribution from the tomographic image data based on the region of interest. An image processing part 5 performs smoothing processing on the myocardial tomographic image data.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to image processing techniques for nuclear medicine.

SPECT (Single Photon Emission Computed Tomography) or PET (Positron Emission Tomography) to obtain a three-dimensional nuclear medicine image by administering a radiopharmaceutical to a subject and detecting the radiation emitted from the radiopharmaceutical : Positron emission tomography), which examines the heart, is attracting attention.

In cardiac nuclear medicine examination, a nuclear medicine image is acquired according to radiation from a radiopharmaceutical accumulated in the myocardium, and a heart examination is performed based on the nuclear medicine image. However, since radiopharmaceuticals are physiologically accumulated in the liver and excreted through the gastrointestinal tract, false images due to radiation from radiopharmaceuticals accumulated in the subdiaphragmatic organs such as the liver and gastrointestinal tract (artifacts) occur in the nuclear medicine image, which affects the image of the myocardium, especially the myocardial inferior wall adjacent to the subdiaphragmatic organ.

For example, the radiation from the subdiaphragmatic organs and the radiation from the inferior myocardial wall may be affected by the partial volume effect, resulting in an increase in the radiation count value of the inferior myocardial wall. In this case, a defect in the myocardial inferior wall may be masked, or the radiation count value may be perceived as decreased in a region other than the myocardial inferior wall. In addition, when image reconstruction is performed by filtered back-projection (FBP), the radiation count value of the myocardial inferior wall may decrease (see Non-Patent Document 1).

Non-Patent Document 2 describes a method for removing the effects of accumulation of radiopharmaceuticals in subdiaphragmatic organs in myocardial nuclear medicine images. Specifically, a method of repeating imaging until radiopharmaceutical accumulation in subdiaphragmatic organs decreases or moves, and a method of adding prone-position imaging in addition to normal supine-position imaging are described. In the prone position imaging, since the distance between the heart and the subdiaphragmatic organs increases, it is possible to reduce a virtual image due to accumulation of the subdiaphragmatic organs.

Steven Burrell, et al. "Artifacts and Pitfalls in Myocardial PerfusionImaging", Journal of Nuclear Medicine Technology, 2006 Dec;34(4):193-211. Ryan A Dvorak, et al. "Interpretation of SPECT/CT Myocardial Perfusion Images: Common Artifacts and Quality Control Techniques", Radiographics, Nov-Dec 2011;31(7):2041-57.

However, the methods described in Non-Patent Documents 1 and 2 do not necessarily reduce the influence of accumulation of radiopharmaceuticals in the subdiaphragmatic organs in nuclear medicine images of the myocardium, and there is a risk that diagnostic accuracy may be reduced. In addition, since it is necessary to perform imaging a plurality of times, there is also the problem that the examination time is long and the burden on the subject is heavy.

The present disclosure has been made in view of the above problems, and aims to provide a program, an image processing apparatus, and an image processing method capable of improving diagnostic accuracy while reducing the burden on a subject.

A program according to one aspect of the present disclosure shows the distribution of radiopharmaceuticals accumulated in the myocardium and subdiaphragmatic organs, and the maximum of the region corresponding to the upper side of the heart center in the tomographic image data before smoothing processing is performed. a setting unit for setting, as a region of interest, a region showing a myocardial distribution, which is the distribution of radiopharmaceuticals accumulated in the myocardium, as a region of interest in the tomographic image data based on a reference pixel value, which is a pixel value; Based on this, the computer is made to realize an extraction unit for extracting myocardial tomographic image data representing the myocardial distribution from the tomographic image data, and an image processing unit for performing smoothing processing on the myocardial tomographic image data.

In a preferred aspect, the setting unit measures the pixel values of the tomographic image data along each of a plurality of radial lines extending three-dimensionally radially from a predetermined position in the heart chamber, and and identifying a myocardial outer wall position corresponding to the myocardial outer wall in the tomographic image data based on highly integrated pixels, which are pixels having a maximum pixel value and a predetermined ratio or more of the reference pixel value, and setting the region of interest based on the location;

In a preferred aspect, when the number of highly integrated pixels is one, the setting unit specifies a position spaced apart from the highly integrated pixel by a certain distance outward from the highly integrated pixel as the myocardial outer wall position, and the number of the highly integrated pixels is two. In the case of three or more, the position of the pixel having the minimum pixel value between the high-integration pixel closest to the predetermined position and the high-integration pixel second closest to the predetermined position is defined as the outer myocardial wall position. Identify.

In a preferred aspect, the setting unit selects a substantially heart-shaped region, which is a region connecting the positions of the outer myocardial wall on each radial line, or an ellipsoidal region in which the shape of the substantially heart-shaped region is approximated to an ellipsoid. Set as the region of interest.

Further, in a preferred aspect, the extracting unit, for each peripheral pixel, which is a pixel on the periphery of the region of interest, extends from the peripheral pixel to a specific distance along an outward line directed outward from the peripheral pixel. If there is an outer integrated pixel between them, which is a pixel whose pixel value is the maximum and whose pixel value is equal to or greater than a certain percentage of the reference pixel value, pixels on the outward line are selected based on the pixel values along the outward line. The myocardial tomographic image data is extracted by subtracting the subdiaphragmatic accumulation pixel value corresponding to the radiopharmaceutical accumulated in the subdiaphragmatic organ from the pixel value of .

In a preferred aspect, the extraction unit approximates a change in pixel value along the outward line from the outer peripheral pixel to the outer integrated pixel with a Gaussian function, and calculates the pixel value represented by the Gaussian function as The pixel value of the subdiaphragmatic accumulation is subtracted from the pixel value of the pixels on the outward line.

In a preferred aspect, the extraction unit approximates changes in pixel values along the outward line in the region of interest with a Gaussian function, and converts the pixel values represented by the Gaussian function to pixels on the outward line. The pixel value is obtained by subtracting the pixel value of the integration under the diaphragm from the pixel value of .

In a preferred aspect, if the outer integrated pixels exist for each of the outer peripheral pixels, the extracting unit sets all pixel values of an area outside the outer integrated pixels along the outward line to zero. and, when the outer integrated pixels do not exist, the pixel values of the area outside the position apart from the peripheral pixels of the tomographic image data by a specific distance are set to zero.

In a preferred aspect, the image processing unit inversely transforms the myocardial tomographic image data into projection data, and performs smoothing processing on the myocardial tomographic image data based on the projection data.

The image processing apparatus according to one aspect of the present disclosure shows the distribution of radiopharmaceuticals accumulated in the myocardium and subdiaphragmatic organs, and the area corresponding to the upper side of the center of the heart in the tomographic image data before smoothing processing is performed A setting unit for setting, as a region of interest, an area showing a myocardial distribution, which is the distribution of radiopharmaceuticals accumulated in the myocardium, in the tomographic image data, based on a reference pixel value that is the maximum pixel value of It has an extraction unit that extracts myocardial tomographic image data representing the myocardial distribution from the tomographic image data based on the region of interest, and an image processing unit that performs smoothing processing on the myocardial tomographic image data.

An image processing method according to an aspect of the present disclosure shows the distribution of radiopharmaceuticals accumulated in the myocardium and subdiaphragmatic organs, and a region corresponding to the upper side of the center of the heart in tomographic image data before smoothing processing is performed Based on the reference pixel value, which is the maximum pixel value of the tomographic image data, a region showing the myocardial distribution, which is the distribution of the radiopharmaceutical accumulated in the myocardium, is set as a region of interest, and the region of interest is Based on this, the myocardial tomographic image data representing the myocardial distribution is extracted from the tomographic image data, and smoothing processing is performed on the myocardial tomographic image data.

According to the present disclosure, it is possible to improve diagnostic accuracy while reducing the burden on a subject.

1 is a block diagram showing the configuration of an image processing device according to an embodiment of the present disclosure; FIG. 4 is a flowchart for explaining the operation of the image processing device according to one embodiment of the present disclosure; 9 is a flowchart for explaining an example of region-of-interest extraction processing; It is a figure which shows an example of the radial line in a slice image. FIG. 10 is a diagram for explaining the process of identifying the myocardial outer wall position; 4 is a flowchart for explaining an example of myocardial extraction processing; FIG. 10 is a diagram for explaining processing for identifying pixel values of integration of subdiaphragmatic organs; It is a figure which shows the image processing method of this indication, and the image processing method of a reference example. FIG. 4 is a diagram showing myocardial tomographic image data obtained by the image processing method of the present disclosure and myocardial tomographic image data obtained by the image processing method of the reference example;

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an image processing device according to one embodiment of the present disclosure. The image processing apparatus 100 shown in FIG. 1 is configured by, for example, a computer system including a processor (computer) and memory (both not shown). In this case, each component and each function of the image processing apparatus 100 described below are realized by, for example, reading a program by a processor and executing the read program. The program can be recorded in a computer-readable recording medium such as a memory.

The image processing apparatus 100 is also connected to an input/output device 101 and an auxiliary storage device 102 . The input/output device 101 is an input device such as a keyboard, touch panel, and pointing device that receives various information from a user who uses the image processing apparatus 100, and outputs various information to the user, such as a display device and a printer. and an output device. The input/output device 101 may also include a network interface device for transmitting and receiving various information via a communication network such as the Internet. Auxiliary storage device 102 is, for example, a storage device that stores various information such as a mass storage device.

The image processing apparatus 100 has an acquisition unit 1 , a reconstruction unit 2 , a setting unit 3 , an extraction unit 4 and an image processing unit 5 .

The acquisition unit 1 acquires, as data to be processed, projection data based on radiation from a subject to whom a radiopharmaceutical has been administered. Projection data is generated by imaging a subject using a radiation detector after a certain period of time after administering a radiopharmaceutical to the subject. Specifically, the projection data is data including a plurality of pixels two-dimensionally arranged for each predetermined rotation angle of the detector rotating around the subject and the pixel value of each pixel. A pixel value is a value determined according to a count value obtained by counting radiation from a part of the subject corresponding to the pixel. The pixel value may be, for example, the count value itself.

In this embodiment, the projection data is projection data for myocardial nuclear medicine examination. In this case, the count value usually shows not only the radiation from the myocardium but also the radiation from the radiopharmaceutical accumulated in the subdiaphragmatic organs such as the liver. Further, the radiopharmaceutical is not particularly limited as long as it is a radiopharmaceutical used for myocardial SPECT examination or myocardial PET examination.

The reconstruction unit 2 generates tomographic image data based on the projection data acquired by the acquisition unit 1 . Specifically, the reconstruction unit 2 performs image reconstruction processing on the projection data, generates horizontal tomographic image data representing a horizontal tomographic image of the myocardium (body-axis cross-sectional image), and generates horizontal tomographic image data. A plurality of tomographic image data with different cross-sectional orientations are generated by performing cross-sectional conversion processing on the . In this embodiment, the tomographic image data includes horizontal long-axis tomographic image data representing a horizontal long-axis tomographic image of the myocardium, vertical long-axis tomographic image data representing a vertical long-axis tomographic image of the myocardium, and short-axis image of the myocardium. The short-axis tomographic image data shown in FIG.

Each tomographic image data reflects not only the distribution of radiopharmaceuticals accumulated in the myocardium but also the distribution of radiopharmaceuticals accumulated in subdiaphragmatic organs such as the liver and gastrointestinal tract adjacent to the heart. Further, each tomographic image data is generated such that the center of the heart (more specifically, the center of the left ventricle of the heart) is positioned at the center of the image. Note that each tomographic image data is a set of multiple slice images.

In this embodiment, the image reconstruction processing is image reconstruction processing using a statistical image reconstruction method including resolution correction, such as the MLEM (Maximum Likelihood Expectation Maximization) method and the OSEM (Ordered Subset Expectation Maximization method) method. is. In this case, the influence of radiopharmaceutical accumulation in the subdiaphragmatic organs on the myocardial inferior wall can be reduced. In addition, extraction of myocardial tomographic image data by the extraction unit 4, which will be described later, is facilitated. However, the image reconstruction processing may be image processing using a statistical image reconstruction method that does not include resolution correction, or image processing using a conventional filtered back-projection (FBP) method. good.

In particular, tomographic image data for myocardial SPECT examination has a relatively small amount of information and a relatively large amount of statistical noise. Smoothing processing is performed to smooth changes in pixel values. However, the smoothing process emphasizes the influence of radiopharmaceutical accumulation in the subdiaphragmatic organs on the inferior myocardial wall. Therefore, in this embodiment, the reconstruction unit 2 does not perform smoothing processing.

Alternatively, the acquisition unit 1 may acquire tomographic image data instead of projection data as data to be processed. In this case, the reconstruction unit 2 does not need to perform image reconstruction processing. It is also assumed that the tomographic image data acquired by the acquisition unit 1 has not undergone smoothing processing.

The setting unit 3 sets a three-dimensional region showing a myocardial distribution, which is the distribution of the radiopharmaceutical accumulated in the myocardium, as a region of interest in the tomographic image data. Specifically, the setting unit 3 maps the myocardial distribution to the tomographic image data based on the reference pixel value, which is the maximum pixel value of the upper region corresponding to the upper side of the center of the heart in the tomographic image data. set the region of interest as the region of interest.

The extraction unit 4 extracts myocardial tomographic image data representing myocardial distribution from the tomographic image data based on the region of interest set by the setting unit 3 .

The image processing unit 5 performs various image processing on the myocardial tomographic image data extracted by the extraction unit 4 and outputs the processed image data. Image processing includes, for example, smoothing processing and cross-section conversion processing. In addition, the image processing may be to generate desired tomographic image data by inversely transforming myocardial tomographic image data into projection data, and performing image reconstruction processing, cross-sectional transformation processing, and smoothing processing on the projection data. good. In this case, it is possible to generate tomographic image data or the like in which the orientation of the cross section is the desired orientation.

FIG. 2 is a flowchart for explaining the operation of the image processing apparatus 100. As shown in FIG.

First, the acquisition unit 1 acquires data to be processed (step S101). For example, the acquisition unit 1 may acquire data via the input/output device 101 from any external device such as an imaging device that images a subject using a radiation detector, or data stored in the auxiliary storage device 102 data may be obtained.

The acquisition unit 1 determines whether the acquired data is projection data (step S102).

If the acquired data is projection data, the reconstruction unit 2 generates tomographic image data based on the projection data (step S103). On the other hand, if the acquired data is not projection data, that is, if the acquired data is tomographic image data, the processing of step S103 by the reconstruction unit 2 is skipped. Assume that the tomographic image data is not subjected to smoothing processing.

The setting unit 3 executes region-of-interest extraction processing (see FIGS. 3 to 5) for setting a region of interest for the tomographic image data acquired by the acquisition unit 1 or the tomographic image data generated by the reconstruction unit 2. (Step S104)

The extracting unit 4 executes myocardial extraction processing (see FIGS. 6 and 7) for extracting myocardial tomographic image data from the tomographic image data based on the region of interest set by the setting unit 3 (step S105).

The image processing unit 5 determines whether or not to generate projection data from the myocardial tomographic image data (step S106). For example, whether or not to generate projection data may be specified in advance, or the image processing unit 5 may ask the user at this stage whether or not to generate projection data.

When projection data is not generated, the image processing unit 5 performs predetermined image processing including smoothing processing on the myocardial tomographic image data (step S107). Then, the image processing unit 5 displays the image-processed myocardial tomographic image data on the input/output device 101 (step S108), and ends the process. Instead of displaying the myocardial integrated data on the input/output device 101, the image processing unit 5 may transmit it to an external device (not shown) via the input/output device 101, or store it in the auxiliary storage device 102. You may

On the other hand, when generating projection data, the image processing unit 5 generates projection data from the myocardial tomographic image data (step S109). Then, the image processing unit 5 generates desired tomographic image data as myocardial tomographic image data from the generated projection data, and performs predetermined image processing including smoothing processing on the myocardial tomographic image data (step S110). Then, the image processing unit 5 shifts to the process of step S108.

FIG. 3 is a flowchart for explaining an example of the region-of-interest extraction processing in step S104.

In the region-of-interest extraction process, the setting unit 3 first determines whether or not to perform precise setting for precisely setting the region of interest (step S201). For example, whether or not to perform the precise setting may be specified in advance, or the setting unit 3 may ask the user at this stage whether to perform the precise setting.

When the precise setting is not performed, the setting unit 3 performs simple setting for simply setting the region of interest (step S202), and ends the process. Methods for simply setting the region of interest include, for example, a method of setting an ellipsoidal region of a predetermined size centered on the center of each tomographic image data as the region of interest, and a method of manually setting the region of interest by the user. .

When fine setting is performed, the setting unit 3 first obtains a reference pixel value, which is the maximum pixel value of the upper region corresponding to the upper side of the center of the heart in the tomographic image data (step S203). Since the upper region is a region that is less affected by radiopharmaceutical accumulation in the subdiaphragmatic organs, the reference pixel value can be regarded as the maximum pixel value that is not affected by the accumulation of radiopharmaceuticals in the subdiaphragmatic organs. In this embodiment, the upper region is assumed to be the upper half region of the short-axis tomographic image data. In this case, the reference pixel value can be set more appropriately.

Note that the upper region may be above the center of the heart, and may be limited to, for example, a portion of the upper half of the short-axis tomographic image data. In addition, the range of the longitudinal direction of the upper region is 100% of the total length along the long axis of the heart, and the range from the apex to the base of the heart (0% to 100%) when the apex is the starting point. However, it may be limited to a range from 30% to 90% more preferably.

Subsequently, the setting unit 3 measures the pixel values of the tomographic image data along each of a plurality of radial lines radially extending three-dimensionally from the center of the heart (step S204). In the present embodiment, the setting unit 3 selects slice images at the center of each of the horizontal long-axis tomographic image data, the vertical long-axis tomographic image data, and the short-axis tomographic image data, which are tomographic image data, at regular intervals from the center of the image. Pixel values are measured outward from the center of the image along each of a plurality of radial lines extending radially. The constant angle is, for example, 3 degrees. Note that the starting point of the radial line is not limited to the center of the heart, and may be any position within the heart chamber. Moreover, the starting point of the three-dimensional radial shape is not limited to the center of the heart, and may be any predetermined position within the heart chamber.

FIG. 4 is a diagram showing an example of radial lines in one slice image. In the example of FIG. 4, 40 radial lines X extending from the center O of the heart are shown with a fixed angle of 9 degrees.

Returning to the description of FIG. After measuring the pixel value of each radial line, the setting unit 3 determines the position of the pixel where the pixel value is the maximum and is equal to or greater than a threshold that is a certain percentage (for example, 20%) of the reference pixel value for each radial line. A high-accumulation position where the radiopharmaceutical is accumulated is identified (step S205). It should be noted that the high-accumulation position is considered to be a position corresponding to the myocardium.

The setting unit 3 specifies the myocardial outer wall position, which is the position corresponding to the outer wall of the myocardium, based on the high accumulation position for each radial line (step S206). Specifically, the setting unit 3 confirms the number of high-accumulation positions for each radial line, and specifies the outer myocardial wall position based on the high-accumulation positions and the number thereof.

FIG. 5 is a diagram for explaining the process of specifying the myocardial outer wall position, showing changes in pixel values along radial lines. In FIG. 5, the horizontal axis indicates positions along radial lines with the center O of the heart being 0, and the vertical axis indicates pixel values. Also, T is the threshold.

FIG. 5A shows an example in which there is one high integration position. In this case, the setting unit 3 determines that there is no accumulation in the subdiaphragmatic viscera in the direction along the radial line, and specifies a position a fixed distance L outward from the high accumulation position M as the myocardial outer wall position W. do. The fixed distance L is, for example, 2 cm.

FIG. 5B shows an example of two or more highly integrated positions. In this case, the setting unit 3 determines that the high accumulation position M1 closest to the center O of the heart is the position of the myocardium, and the high accumulation position M2 that is second closest to the center O of the heart is the position of accumulation of the radiopharmaceutical in the subdiaphragmatic organs. Then, the position of the minimum pixel value between the high accumulation position M1 and the high accumulation position M2 is specified as the myocardial outer wall position W. FIG. At this time, if there is a predetermined distance (for example, 2 cm) or more between the high-accumulation position M1 and the high-accumulation position M2, the setting unit 3 selects a position a predetermined distance away from the high-accumulation position M1 toward the outer wall of the myocardium. It may be identified as position W. The predetermined distance may be the same as the fixed distance L shown in FIG. 4(a).

FIG. 5(c) shows an example in which the high integration position is zero. In this case, the setting unit 3 determines that there is no myocardium in the direction along the radial line, and does not specify the myocardium outer wall position W. FIG.

Returning to the description of FIG. After specifying the position of the outer myocardial wall for each radial line, the setting unit 3 sets the region of interest based on the position of the outer myocardial wall of each radial line (step S207), and ends the process.

The region of interest is a substantially heart-shaped region connecting the positions of the myocardial outer wall of each radial line of each tomographic image data, or an ellipsoidal region obtained by approximating the shape of the substantially heart-shaped region to an ellipsoid. The method of approximating the approximately heart-shaped area to the ellipsoidal area is not particularly limited, but may be, for example, the method of least squares. Whether the region of interest should be a substantially heart-shaped region or an ellipsoidal region may be set in advance or may be set by the user.

Note that the region of interest may be adjusted manually. For example, if the region of interest is an ellipsoidal region, adjustment of the region of interest includes movement of the entire region of interest, movement of the ellipsoid along three axes, deformation and rotation. Further, when the region of interest is a substantially heart-shaped region, adjustment of the region of interest includes mesh deformation, movement of the entire region of interest, correction for each pixel, and the like.

FIG. 6 is a flowchart for explaining an example of myocardial extraction processing in step S105.

In the myocardial extraction process, the extraction unit 4 determines whether or not to perform presumed removal to remove the influence of radiopharmaceutical accumulation in the subdiaphragmatic organs on the region of interest (step S301). For example, whether or not to perform the estimated removal may be specified in advance, or the extraction unit 4 may inquire of the user at this stage whether to perform the estimated removal.

If the estimation removal is not performed, the extraction unit 4 sets all pixel values of regions other than the region of interest of each tomographic image data to zero, thereby extracting myocardial tomographic image data (step S302), and ends the process. do.

In the case of presumed removal, the extraction unit 4 analyzes the tomographic image data and estimates the pixel values resulting from the accumulation of the radiopharmaceutical in the subdiaphragmatic organs (step S303).

Specifically, first, the extraction unit 4 measures the pixel value along an outward line extending outward from each peripheral pixel, which is a pixel on the periphery of the region of interest in the tomographic image data. . The outward line is specifically a line passing through the peripheral pixels and the center of the region of interest, or a line passing through the peripheral pixels and perpendicular to the periphery of the region of interest.

Subsequently, the extraction unit 4 extracts, for each peripheral pixel, a pixel value that is maximum and a constant ratio of the reference pixel value (for example, , 20%).

If there is no outer integrated pixel, the extraction unit 4 determines that there is no pixel value due to the integration of the subdiaphragmatic organ on the outward line, and does not estimate the pixel value of the integration of the subdiaphragmatic organ.

On the other hand, if the outer integrated pixels are present, the extraction unit 4 estimates the pixel values of the integrated subdiaphragmatic organs based on the pixel values from the outer peripheral pixels to the outer integrated pixels on the outward line.

FIG. 7 is a diagram for explaining the process of estimating the pixel values of the integration of the subdiaphragmatic organs based on the pixel values from the peripheral pixels to the outer integration pixels. In FIG. 7, the horizontal axis indicates the position along the outward line, and the vertical axis indicates the pixel value. Also, T is the threshold, R is the specific distance, C is the peripheral pixel, and D is the outer integrated pixel.

The extraction unit 4 performs fitting to approximate the change F in pixel value from the peripheral pixel C to the outer integrated pixel D on the outward line with a Gaussian function, and obtains a Gaussian function G that approximates the change F. FIG. Then, the extraction unit 4 specifies the pixel value represented by the Gaussian function G as the pixel value of the accumulation of the subdiaphragmatic organs. A function other than the Gaussian function may be used as the function that approximates the change F.

Returning to the description of FIG. After estimating the pixel value of the accumulation of the subdiaphragmatic organ, the extraction unit 4 subtracts the pixel value of the accumulation of the subdiaphragmatic organ corresponding to each peripheral pixel from the pixel value of the tomographic image data, and extracts the myocardial image data ( Step S304), the process ends. In the example of FIG. 7, the pixel values represented by the curve H obtained by subtracting the pixel values of the accumulation of the subdiaphragmatic organs represented by the Gaussian function G from the pixel values represented by the pixel value changes F are the pixels of the myocardial image data. value.

In step S304, if there is a pixel with a negative value obtained by subtracting the subdiaphragmatic organ accumulation pixel value from the tomographic image data pixel value, the extraction unit 4 sets the pixel value of the pixel to zero. In addition, the extraction unit 4 sets zero outside the outer integrated pixels or outside a position separated by a specific distance from the peripheral pixels along the outward line.

In step S303, the change F in the pixel value from the peripheral pixel C to the outer integrated pixel D is approximated by the Gaussian function G. may be approximated by a Gaussian function. In this case, myocardial image data is extracted by replacing the pixels outside the high accumulation position M with pixels represented by a Gaussian function.

As described above, according to the present embodiment, the setting unit 3 performs the smoothing process based on the reference pixel value, which is the maximum pixel value of the region corresponding to the upper side of the center of the heart in the tomographic image data before the smoothing process is performed. Then, an area showing the myocardial distribution, which is the distribution of the radiopharmaceutical accumulated in the myocardium, is set as the region of interest in the tomographic image data. The extraction unit 4 extracts myocardial tomographic image data representing myocardial distribution from the tomographic image data based on the region of interest. The image processing unit 5 performs smoothing processing on the myocardial tomographic image data. Therefore, the smoothing process is performed after the myocardial tomographic image data representing the myocardial distribution is extracted from the tomographic image data. Therefore, it is possible to generate image data with high visibility while removing the influence of accumulation of radiopharmaceuticals in the subdiaphragmatic organs in tomographic image data without performing multiple imaging of the subject. It is possible to improve diagnostic accuracy while reducing the burden.

Further, in this embodiment, the setting unit 3 measures the pixel values of the tomographic image data along each of a plurality of radial lines extending radially in three dimensions from the center of the heart, and the pixel value is maximized for each of the radial lines. and specifying a myocardial outer wall position corresponding to the myocardial outer wall position in the tomographic image data based on the high-accumulation pixels, which are pixels having a predetermined ratio or more of the reference pixel value, and setting a region of interest based on the myocardial outer wall position. do. Therefore, it is possible to appropriately set the region of interest.

Further, in the present embodiment, when there is one highly integrated pixel, the setting unit 3 specifies a position a certain distance away from the highly integrated pixel toward the outside as the myocardial outer wall position, and when there are two or more highly integrated pixels, , the position of the pixel having the minimum pixel value between the high-integration pixel closest to the center and the high-integration pixel second closest to the center as the outer myocardial wall position. Therefore, it is possible to appropriately specify the position of the outer myocardial wall, so that it is possible to more appropriately set the region of interest.

Further, in the present embodiment, the region of interest is a substantially heart-shaped region that is a region connecting the outer wall positions of the myocardium on radial lines, or an ellipsoidal region that approximates the shape of the substantially heart-shaped region to an ellipsoid. Therefore, it is possible to set the region of interest to an appropriate region showing the heart.

Further, in the present embodiment, the extraction unit 4, for each peripheral pixel, which is a pixel on the periphery of the region of interest, along an outward line from the peripheral pixel to a specific distance. If there is an outer integrated pixel whose pixel value is maximum and whose pixel value is equal to or higher than a certain percentage of the reference pixel value, the pixel value of the pixel on the outward line is calculated based on the pixel value along the outward line. Myocardial tomographic image data is extracted by subtracting the pixel value of the accumulation of the subdiaphragmatic organ, which is the pixel value corresponding to the radiopharmaceutical accumulated in the subdiaphragmatic organ. Therefore, myocardial tomographic image data can be appropriately extracted.

Further, in the present embodiment, the extraction unit 4 approximates changes in pixel values along the outward line from the outer peripheral pixels to the outer integrated pixels with a Gaussian function, and converts the pixel values represented by the Gaussian function into subdiaphragmatic organs. is subtracted from the pixel value of the pixel on the outward line as the pixel value of the accumulation of . Therefore, it is possible to appropriately obtain the pixel value of the accumulation of the subdiaphragmatic organs, so that the myocardial tomographic image data can be extracted more appropriately.

Further, in the present embodiment, if there is an outer integrated pixel for each peripheral pixel, the extraction unit 4 sets all the pixel values of the area outside the outer integrated pixel along the outward line to zero, and does not exist, all the pixel values of the area outside the position apart from the peripheral pixels of the tomographic image data by a specific distance are set to zero. Therefore, it becomes possible to appropriately extract the myocardial distribution, which is the distribution of the radiopharmaceutical accumulated in the myocardium.

Further, in the present embodiment, the image processing unit 5 inversely transforms the myocardial tomographic image data into projection data, and performs smoothing processing on the myocardial tomographic image data based on the projection data. Therefore, it is possible to generate a desired myocardial tomographic image.

Here, in order to evaluate the influence of accumulation of radiopharmaceuticals in the subdiaphragmatic organs on myocardial tomographic image data, myocardial tomographic image data obtained by the image processing method of the present disclosure is compared with the myocardial tomographic image data obtained by the image processing method of the reference example. did.

FIG. 8 is a diagram showing an image processing method of the present disclosure and an image processing method of a reference example. Specifically, FIG. 8(a) shows an image processing method of a reference example, and FIG. 8(b) shows an image processing method of the present disclosure.

In the image processing method of the reference example shown in FIG. 8A, after performing smoothing processing on tomographic image data generated by reconstruction processing, section conversion processing and myocardium extraction processing are performed. On the other hand, according to the image processing method of the present disclosure shown in FIG. I am doing smoothing. In the myocardial extraction processing, all pixel values in regions other than the region of interest of each tomographic image data are set to zero, without presuming removal to remove the influence of radiopharmaceutical accumulation in the subdiaphragmatic organs on the region of interest. ing.

FIG. 9 is a diagram showing myocardial tomographic image data obtained by the image processing method of the reference example and myocardial tomographic image data obtained by the image processing method of the present disclosure.

A Siemens Symbia T6 equipped with a low-energy high-resolution collimator was used as an imaging device for acquiring projection data, and a Siemens nuclear medicine image processing workstation SYNGO Mi Apps (version.VA60C) was used for data processing. ), and DRIP and cardioBULL manufactured by Fuji Film Toyama Chemical Co., Ltd. were used. Curie meter IGC-7 manufactured by Aloka was used as a dose calibrator.

A heart-liver HL type phantom manufactured by Kyoto Kagaku Co., Ltd. was used as the subject, and a cylindrical container made of polypropylene (with a lumen diameter of 3.5 mm) was placed on the outside of the lower wall of the left ventricular myocardium to simulate accumulation of subdiaphragmatic organs. 5 cm, length 10.0 cm, volume 100.0 mL). In addition, two types of subjects were prepared, one with no defect in the left ventricular myocardium, and the other with a circular defect tip with a diameter of 2.0 cm attached to the center of the lower wall of the left ventricular myocardium. In the following description, tomographic image data acquired when there is no defect in the left ventricular myocardium is sometimes referred to as data without defect, and tomographic image data acquired when a circular defect chip is attached is sometimes referred to as data with defect. .

The nuclide of the radiopharmaceutical is 99mTc, and the amount of ^99mTc enclosed in the left ventricular myocardium (capacity 120 mL) is assumed to be approximately 2% of the dose accumulated in the myocardium in clinical practice, and the accumulated amount corresponding to the administration of ^740MBq 14.8 MBq (123 kBq/mL). Cylindrical vessels had radiodensity ratios of 0 (water only), 0.5, 0.75, 1.0, 1.25, 1.5, 2.0, and 3.0 for the cylindrical vessels to the left ventricular myocardium. ^99m Tc is encapsulated in such a manner as to be as follows, and FIG. 9 shows their myocardial tomographic image data (specifically, the central slice of short-axis tomographic image data). Only water was sealed in the left ventricle, right ventricle, mediastinum, liver and stomach. In addition, as an image reconstruction method used for image reconstruction processing, FBP, OSEM, OSEM-PR with resolution correction (Resolution Recovery: RR), attenuation correction (Attenuation Correction: AC), scattering correction (Scatter Correction: FIG. 9 shows myocardial tomographic image data obtained by each image reconstruction method using OSEM-ACSCR, which is an OSEM with resolution recovery (SC) and resolution recovery (PR).

Each myocardial tomographic image data was evaluated as follows.

Specifically, in the central slice of short-axis tomographic image data, a CPC (circumferential profile curve) is created at intervals of 1 degree within the region of interest, and the maximum pixel value in the upper half region is was normalized as 100%. In clinical practice, when %Uptake, which is the ratio of the pixel value to the maximum pixel value, is 70% or less, it is often judged to be a significant blood flow abnormality. The effect of accumulation of subdiaphragmatic organs is considered significant when the minimum value of the 90-degree region on the wall side is 70% or more, and the maximum value of the 90-degree region on the lower wall side is 143 for data without defects. If the value is (100/0.7) or more, there is a possibility that walls other than the lower wall may appear to have abnormal blood flow.

Regarding missing data, in the image processing method of the reference example, when the image reconstruction method is FBP and OSEM, the radiation density ratio of the cylindrical container is 0.75 or more, the %Uptake is 70% or more, and the image reconstruction In the case of OSEM-PR and OSEM-ASCPR using PR as the method, the radiation concentration ratio of the cylindrical container was 1.0 or more and 70% or more.

On the other hand, in the image processing method of the present disclosure, when the image reconstruction method is FBP, the radiation density ratio of the cylindrical container is 1.75 or more and the %Uptake is 70% or more, and when the image reconstruction method is OSEM, the cylindrical container When the radiation density ratio is 1.25 or more and the %Uptake is 70% or more, and the image reconstruction method is OSEM-PR, the radiation density ratio of the cylindrical container is 3.0 or more and the %Uptake is 70% or more. Also, when the image reconstruction method was OSEM-ACSCPR, %Uptake was less than 70% at all radiation density ratios.

Regarding the data without loss, in the image processing method of the reference example, when the image reconstruction method is FBP, the radiation density ratio of the cylindrical container is 2.0 or more and the %Uptake is 143% or more. In the case of , %Uptake was 143% or more when the radiation density ratio of the cylindrical container was 1.5 or more. On the other hand, in the image processing method of the present disclosure, Uptake was less than 143% in all image reconstruction methods.

Therefore, it was shown that the image processing method of the present disclosure can reduce the influence of the accumulation of the subdiaphragmatic organs and improve the diagnostic accuracy.

The above-described embodiments and examples of the present disclosure are illustrative examples of the present disclosure, and are not intended to limit the scope of the present disclosure only to those embodiments. Those skilled in the art can implement the present disclosure in various other forms without departing from the scope of the present disclosure.

1: acquisition unit, 2: reconstruction unit, 3: setting unit, 4: extraction unit, 5: image processing unit, 100: image processing device, 101: input/output device, 102: auxiliary storage device

Claims (11)

To the reference pixel value, which is the maximum pixel value of the area corresponding to the upper side of the center of the heart in the tomographic image data before smoothing, which shows the distribution of radiopharmaceuticals accumulated in the myocardium and subdiaphragmatic organs a setting unit for setting, as a region of interest, an area showing a myocardial distribution, which is the distribution of the radiopharmaceutical accumulated in the myocardium, in the tomographic image data based on
an extraction unit that extracts myocardial tomographic image data representing the myocardial distribution from the tomographic image data based on the region of interest;
A program for causing a computer to implement an image processing unit that performs smoothing processing on the myocardial tomographic image data. The setting unit measures the pixel values of the tomographic image data along each of a plurality of radial lines extending three-dimensionally from a predetermined position in the heart chamber, and identifying a myocardial outer wall position corresponding to the myocardial outer wall position in the tomographic image data based on highly integrated pixels, which are pixels having a predetermined ratio or more of the reference pixel value, and determining the region of interest based on the myocardial outer wall position. 2. The program according to claim 1, which sets the . When the number of the highly integrated pixels is one, the setting unit specifies a position spaced outward from the highly integrated pixels by a predetermined distance as the outer wall position of the myocardium. 3. The position of the pixel having the minimum pixel value between the high-integration pixel closest to the position of and the high-integration pixel second closest to the predetermined position is specified as the outer myocardial wall position. program as described. The setting unit sets, as the region of interest, a substantially heart-shaped region that is a region connecting the outer wall positions of the myocardium on each radial line, or an ellipsoidal region that approximates the shape of the substantially heart-shaped region to an ellipsoid. 4. A program according to claim 3. The extracting unit, for each peripheral pixel, which is a pixel on the periphery of the region of interest, along an outward line extending outward from the peripheral pixel, within a specific distance from the peripheral pixel, the pixel value is maximized. In addition, when there is an outer integrated pixel which is a pixel having a certain ratio or more of the reference pixel value, based on the pixel value along the outward line, the pixel value of the pixel on the outward line is divided into the subdiaphragm 5. The program according to any one of claims 1 to 4, wherein the myocardial tomographic image data is extracted by subtracting the subdiaphragmatic accumulation pixel value, which is the pixel value corresponding to the radiopharmaceutical accumulated in the organ. The extraction unit approximates a change in pixel value from the peripheral pixel to the outer integrated pixel along the outward line with a Gaussian function, and converts the pixel value represented by the Gaussian function to the subdiaphragmatic integrated pixel. 6. The program according to claim 5, wherein the value is subtracted from pixel values of pixels on said outward line. The extraction unit approximates changes in pixel values along the outward line in the region of interest with a Gaussian function, and extracts pixel values represented by the Gaussian function from pixel values of pixels on the outward line to the subdiaphragmatic area. 6. The program according to claim 5, wherein the pixel value is obtained by subtracting the pixel value of the accumulation of . The extracting unit, for each peripheral pixel, when the outer integrated pixel exists, sets all pixel values of a region outside the outer integrated pixel along the outward line to zero, and determines that the outer integrated pixel exists. 8. The program according to claim 6 or 7, wherein, if not, all pixel values in an area outside a position separated by a specific distance outward from said peripheral pixels of said tomographic image data are all set to zero. 9. The program according to any one of claims 1 to 8, wherein the image processing unit inversely transforms the myocardial tomographic image data into projection data, and performs smoothing processing on the myocardial tomographic image data based on the projection data. . To the reference pixel value, which is the maximum pixel value of the area corresponding to the upper side of the center of the heart in the tomographic image data before smoothing, which shows the distribution of radiopharmaceuticals accumulated in the myocardium and subdiaphragmatic organs a setting unit for setting, as a region of interest, an area showing a myocardial distribution, which is the distribution of the radiopharmaceutical accumulated in the myocardium, in the tomographic image data based on
an extraction unit that extracts myocardial tomographic image data representing the myocardial distribution from the tomographic image data based on the region of interest;
and an image processing unit that performs smoothing processing on the myocardial tomographic image data. To the reference pixel value, which is the maximum pixel value of the area corresponding to the upper side of the center of the heart in the tomographic image data before smoothing, which shows the distribution of radiopharmaceuticals accumulated in the myocardium and subdiaphragmatic organs Based on this, for the tomographic image data, a region showing the myocardial distribution, which is the distribution of the radiopharmaceutical accumulated in the myocardium, is set as a region of interest,
extracting myocardial tomographic image data representing the myocardial distribution from the tomographic image data based on the region of interest;
An image processing method, comprising smoothing the myocardial tomographic image data.

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