JP2017219530A - Method and device for analyzing myocardial nuclear medicine image data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new method for quantitatively evaluating a tracer accumulation for a nuclear medicine study on a heart.SOLUTION: In a method for analyzing myocardial nuclear medicine image data, radiation count information obtained through myocardial nuclear medicine measurement is normalized using a value related to a size of a heart. A preferred embodiment is characterized by conversion of a pixel value of each pixel of myocardial nuclear medicine image data into an SUV represented by [SUV=a tissue radioactivity concentration/(a radioactive dosage amount/a value related to the size of the heart)]. The value related to the size of the heart can be, for example, cardiac mass.SELECTED DRAWING: Figure 2

Description

  The present application relates to a method for analyzing myocardial nuclear medicine image data and an analysis apparatus.

  Nuclear medicine techniques are often used to obtain various physiological and biochemical information about the heart. In particular, the SPECT test has an excellent feature that the load test can be easily performed, the test success rate is high, the invasiveness is low, and the renal function is not affected.

The primary image obtained by nuclear medicine measurement is an image of the radiation count value or tissue radioactivity concentration, and the pixel corresponding to the region where the tracer is highly integrated has a large pixel value and is displayed brightly. The However, since the radiation count value or tissue radioactivity concentration is affected by various factors, it is not always clear whether the corresponding tissue is abnormal just because the pixel value of a particular pixel is different from other parts. Absent. Therefore, attempts have been made to quantitatively evaluate pixel values by normalizing each pixel value according to a certain rule. SUV (Standardized Uptake Value) is often used as such a quantitative value. SUV has the following values.
SUV = tissue radioactivity concentration / {radioactivity dose / subject's body weight}

  That is, SUV is a value obtained by normalizing the tissue radioactivity concentration with the radioactivity dose per body weight. A lean body weight may be used instead of a simple body weight (Non-patent Document 1).

Yoshifumi Sugawara, Kenneth R. Zasadny et al, "Reevaluation of the Standardized Uptake Value for FDG: Variations with Body Weight and Methods for Correction", November 1999 Radiology, 213, 521-525.

  A conventional SUV is a value created assuming that the tracer is uniformly distributed throughout the body or muscle. However, in the case of nuclear medicine examination of the heart, the tracer accumulates mainly in the myocardium, so the assumptions in conventional SUVs may not be appropriate. For this reason, it has become necessary to develop a new method for quantitatively evaluating tracer accumulation.

  One of the inventions described in this application is characterized by normalizing image data obtained by nuclear myocardial medicine measurement using a value related to the size of the heart.

In a preferred embodiment, the pixel value of each pixel of myocardial nuclear medicine image data is expressed by the following formula:

SUV = tissue radioactivity concentration / (radioactivity dose / value relating to heart size)

It is characterized by being converted to SUV, which can be expressed as follows.

  In the present invention, when normalizing myocardial nuclear medicine image data, a value relating to the size of the heart accumulated by the tracer is used as a standard for normalization. Therefore, the standard of normalization reflects the actual state of cardiac function more accurately than in the prior art. For this reason, the validity of the normalized value is increased as compared with the conventional technique, and image evaluation more appropriate than the conventional technique can be performed.

  In the above invention, the “value relating to the size of the heart” can be, for example, the weight of the heart. The weight of the heart can be, for example, the weight of the myocardium. The myocardial weight may be a value obtained by multiplying the myocardial volume by a density coefficient, for example.

In the above invention, the “tissue radioactivity concentration” may be a value obtained by multiplying a pixel value of myocardial nuclear medicine image data by a Becquerel calibration factor (BCF). BCF is a coefficient for converting a radiation count value into a radioactivity concentration (for example, Bq / ml). BCF can be obtained by a known method. For example, a nuclear medicine image can be taken for a vial (or syringe) containing a radiopharmaceutical having a known total radioactivity, and the value calculated by the following equation can be used.

BCF = Attenuation-corrected total activity (Bq) / (Total count of all slices / Collection time (seconds))

Moreover, when calculating | requiring BCF from the data obtained using the cylindrical phantom, the following formula can be used.

Volume coefficient = average count value in 1 slice / (volume of 1 pixel x collection time (seconds))

BCF = Attenuation corrected total activity (Bq) / (Phantom capacity × Volume coefficient)

Depending on the embodiment, the collection time may be corrected for the BCF. The collection time correction may be performed by, for example, multiplying the BCF by {1 pixel volume [cm ³ ] / collection time [sec]}.

  Depending on the myocardial nuclear medicine image data, each pixel value may already indicate the radioactivity concentration. In this case, of course, BCF is not necessary.

  One type of embodiment of the present invention includes the following method. This method is a method of processing myocardial nuclear medicine image data, wherein the processing means of the apparatus is executed by executing a program command,

  Operating said device as a first means for storing a heart parameter, which is a value relating to the size of the heart, and as a second means for storing a radioactive dose;

Using the values stored in the first means and the second means, the pixel values of at least some of the pixels of the image data are expressed by the following formula:

SUV = tissue radioactivity concentration / (radioactivity dose / value based on cardiac parameters)

Converting to SUV and storing;
including.

  In some embodiments, the cardiac parameter is myocardial weight, and the value based on the cardiac parameter is also myocardial weight.

  In some embodiments, the cardiac parameter is a myocardial volume, and the value based on the cardiac parameter is a myocardial weight calculated by multiplying the myocardial volume by a conversion factor.

  One type of embodiment of the invention is a computer program comprising program instructions configured to cause the apparatus to perform the method when executed by a processing means of the apparatus.

  In one embodiment of the above invention, there is provided an apparatus comprising processing means and storage means, wherein the storage means stores program instructions, and when the program instructions are executed by the processing means, the method There is an apparatus configured to perform the following.

  Some of the implementations of the present invention that are presently preferred are specified in the claims that follow. However, the configurations specified in these claims do not necessarily include all of the novel technical ideas disclosed in the present specification and drawings. The applicant shall allege that he has the right to obtain a patent for all the new technical ideas disclosed in the present specification and drawings, regardless of whether they are described in the present claims. Is noted.

It is a figure for demonstrating the hardware constitutions of the system which can implement this invention. It is a figure for demonstrating the suitable Example of the SUV conversion process of a myocardial nuclear medicine image.

  Hereinafter, examples of preferred embodiments of the technical idea disclosed in the present application will be described with reference to the accompanying drawings.

  FIG. 1 is a diagram for explaining a hardware configuration of a system 100 in which the present invention can be implemented. As illustrated in FIG. 1, the system 100 is similar to a general computer in hardware, and includes a CPU 102, a main storage device 104, a mass storage device 106, a display interface 107, a peripheral device interface 108, a network. An interface 109 or the like can be provided. As with a general computer, a high-speed RAM (Random Access Memory) can be used as the main storage device 104, and an inexpensive and large-capacity hard disk or SSD can be used as the large-capacity storage device 106. it can. A display for displaying information can be connected to the system 100, which is connected via a display interface 107. In addition, a user interface such as a keyboard, a mouse, and a touch panel can be connected to the system 100, and this is connected via the peripheral device interface 108. The network interface 109 can be used to connect to another computer or the Internet via a network.

  The mass storage device 106 stores an operating system (OS) 110, an SUV conversion program 120, an alignment program 122, and a contour extraction / volume calculation program 124. The most basic functions of the system 100 are provided by the OS 110 being executed by the CPU 102. The SUV conversion program 120 includes program instructions relating to new processes disclosed by the present application, and the system 100 executes the new processes disclosed in the present application by executing at least a part of the instructions by the CPU 102. Can be carried out.

  The contour extraction / volume calculation program 124 is a program having instructions for extracting the contour of the myocardium. Several algorithms or software for myocardial contour extraction are known. For example, such an algorithm is disclosed in International Publication (WO2013 / 047496A1) of the PCT application filed by the present applicant. In addition, there are myocardial contour extraction algorithms or software such as QGS developed at Cedras-Sinai Medical Center, 4D-MSPECT developed at University of Michigan, and pFAST developed at Sapporo Medical University. The program instructions included in the contour extraction / volume calculation program 124 may be configured to extract a myocardial contour using these algorithms and software and calculate the volume of the extracted myocardium. Although the embodiments of the invention disclosed in the present application can operate with various myocardial contour extraction algorithms, it is preferable to perform myocardial contour extraction using the algorithm described in WO2013 / 047496A1 because of its high extraction accuracy. It is.

  The mass storage device 106 can further store three-dimensional nuclear medicine image data 130. These nuclear medicine image data are to be analyzed or manipulated by the programs 120 and 124. The mass storage device 106 may further store a collection condition file 131 that stores various data collection conditions related to the nuclear medicine image data. Further, data 150 obtained by converting the nuclear medicine image data 130 into an SUV by the SUV conversion program 120 can also be stored.

  In addition to the elements depicted in FIG. 1, the system 100 can have a configuration similar to that of an apparatus included in a normal computer system, such as a power supply or a cooling device. The implementation form of the computer system includes storage device distribution / redundancy and virtualization, use of multiple CPUs, CPU virtualization, use of a processor specialized for specific processing such as DSP, and implementation of specific processing in hardware. Various forms using various techniques, such as combining, are known. The invention disclosed in the present application may be mounted on any form of computer system, and the scope thereof is not limited by the form of the computer system. The technical idea disclosed in this specification is generally (1) executed by a processing unit to cause an apparatus or a system including the processing unit to perform various processes described in this specification. (2) an operation method of an apparatus or a system realized by the processing means executing the program, and (3) the program and the program. The present invention can be embodied as an apparatus or system provided with processing means. As described above, some software processing may be implemented as hardware.

  It should be noted that the data 130, 131, 135, etc. are often not stored in the mass storage device 106 when the system 100 is manufactured and sold or activated. These data may be data transferred from an external device to the system 100 via the peripheral device interface 108 or the network interface 109, for example. Depending on the embodiment, the data 131 and 150 may be formed through execution of the SUV conversion program 120 by the CPU 102. Further, depending on the implementation form of the alignment program 122 and the OS 110, at least one of the data 131 and 150 may not be stored in the mass storage device 106 but may be stored only in the main storage device 104. It should be noted that the scope of the invention disclosed in the present application is not limited by the presence or absence of these data.

Next, the three-dimensional nuclear medicine image data 130 will be described in detail. This image data is image data obtained by nuclear medicine measurement performed using the myocardium as an examination target tissue. In this embodiment, the three-dimensional nuclear medicine image data is image data obtained using SPECT as a nuclear medicine measurement technique. SPECT examinations that are performed using the myocardium as an examination target tissue include myocardial blood flow SPECT examinations that are performed for the purpose of detecting ischemia, for example. Examples of radiopharmaceuticals for SPECT suitable for this test include ²⁰¹ TlCl (thallium chloride), tetrophosmin technetium ( ^99m Tc) injection, 15- (4-iodophenyl) -3 (R, S) -methylpentadecanoic acid ( ¹²³ I) Injection solutions and the like are known.
In the embodiment described in detail below, the image data 130 is image data in which each pixel value corresponds to a radiation count value. However, in some embodiments, the image data 130 may be image data such that each pixel value represents a tissue radioactivity concentration.

  Next, the flow of the SUV conversion processing 300 of nuclear medicine image data disclosed in the present application will be described with reference to FIG. The process 300 can be a process performed by the system 100 when the SUV conversion program 120 is executed by the CPU 102. Further, depending on the embodiment, a predetermined process may be performed when the contour extraction / volume calculation program 124 is called from the SUV conversion program 120 and executed by the CPU 102 while the process 300 is being performed. .

  Step 305 indicates the start of processing. In step 310, data to be processed by the SUV conversion program 120 is read (loaded). That is, all or part of the image data 130 is read from the mass storage device 106 and stored in the main storage device 104. The image data 130 may be directly taken into the main storage device 104 from an external nuclear medicine device via the network interface 109.

In step 320, various acquisition conditions for the image data 130 are acquired. The various collection conditions are, for example, the following information.
-Radiation dose measured before administration of radiopharmaceuticals to subjects (pre-dose radiation dose). For example, the value obtained by measuring the radiation dose for each syringe with the radiopharmaceutical to be administered in a syringe for administration.
-Measurement date and time of pre-dose radiation dose-Date and time of data collection start-Data collection time-Radiation dose measured after administration of radiopharmaceuticals to subjects (post-dose radiation dose). For example, a measurement of the radiation dose remaining in the syringe after administration.
・ Date and time of measurement of radiation dose after administration ・ Half-life of tracer contained in radiopharmaceutical ・ BCF (Becquerel calibration factor, coefficient that converts radiation count value into radioactivity concentration (eg Bq / ml))

  Depending on the embodiment, these acquisition conditions may be included in the image data 130. In that case, the system 100 may read the information from the data 130 and store it in the main storage device 104 or the mass storage device 106.

  In some embodiments, the system 100 may be configured to generate and display a user interface (eg, a dialog box) for an operator to input these collection conditions. When the operator inputs necessary collection conditions, the system 100 may store them in the main storage device 104 or the mass storage device 106.

  In some embodiments, each pixel value in the image data 130 may represent a tissue radioactivity concentration. In such a case, since the BCF is not used, it is not necessary to acquire the BCF.

  As described above, the system 100 may be configured to store the acquired collection condition information in the main storage device 104 or the mass storage device 106. In this embodiment, it is assumed that the collection condition information for the image data 130 is stored in the collection condition file 131.

  In step 335, myocardial contour extraction is performed on the image data 130 after alignment. The processing in step 335 may be performed by the CPU 102 executing the contour extraction / volume calculation program 124. As described above, several algorithms or software for myocardial contour extraction are known. For example, such an algorithm is disclosed in International Publication (WO2013 / 047496A1) of PCT application by the applicant of the present application. Yes. The program instructions included in the contour extraction / volume calculation program 124 may be configured to extract a myocardial contour using the algorithm.

  In some embodiments, the contour extraction / volume calculation program 124 may be configured to calculate the volume of the myocardium using the extracted contour. For example, the number of pixels existing between the extracted myocardial inner membrane and outer myocardium may be multiplied by a pixel-volume conversion factor (for example, the volume per pixel) to obtain the volume of the myocardium.

In step 340, the radiation dose administered to the subject is calculated. The information necessary to calculate the dose of radiation administered is as follows.
-Radiation dose measured before administration of radiopharmaceuticals to subjects (pre-dose radiation dose).
• Measurement date and time of pre-dose radiation dose • Date and time of data collection start • Radiation dose measured after administration of radiopharmaceuticals to subjects (post-dose radiation dose).
-Date and time of measurement of radiation dose after administration-Half-life of tracer included in radiopharmaceuticals In this example, these pieces of information are acquired in step 320 and stored in the collection condition file 131. Therefore, the system 100 may acquire the information by reading from the collection condition file 131 in step 340.

Subsequently, the dose of administration radiation is calculated using the following formula.

Attenuation time 1 (seconds) = | Measurement date and time of pre-dose radiation dose-Date and time of data collection start |
Attenuation time 2 (seconds) = | Date and time of measurement of radiation dose after administration-Date and time of data collection start |
Attenuation coefficient = LN (2.0) / half-life (seconds) (LN; natural logarithm of e at the bottom)
Dosage dose = {Radiation dose before administration × Exp (−attenuation coefficient × Attenuation time 1)} − {Radiation dose after administration × Exp (−Attenuation coefficient × Attenuation time 2)}

In step 345, the pixel value of each pixel of the image data 130 is converted to SUV. In the existing SUV conversion, normalization is performed using the body weight of the subject. However, the SUV conversion of the present embodiment is performed by the following equation 1.

[Formula 1]
SUV = tissue radioactivity concentration / (radioactivity dose / myocardial weight)

  Each parameter will be briefly described as follows.

  Tissue radioactivity concentration: Although it may be a value that has been subjected to normalization or interpolation processing, each pixel value in many nuclear medicine image data represents either tissue radioactivity concentration or radiation count value ing. When the pixel value of each pixel of the image data 130 represents the radioactivity density, the pixel value may be used as it is as the tissue radioactivity density. When the pixel value of each pixel of the image data 130 represents a radiation count value, a Becquerel Calibration Factor (Becquerel Calibration Factor), which is a coefficient for converting the radiation count value into a radiation concentration (for example, Bq / ml); It is necessary to convert the pixel value to the radioactivity density by multiplying by (BCF). If a BCF is required, for example, it may be configured to obtain this transform coefficient at step 320.

  Radioactive dose: The dose of radiation determined in step 340.

  Myocardial weight: calculated based on myocardial contour data obtained in step 335. For example, the number of pixels existing between the extracted myocardial intima and outer myocardium is multiplied by a pixel-volume conversion factor to obtain the myocardial volume, and the obtained myocardial volume is calculated by calculating the myocardial volume-myocardial weight. The myocardial weight may be obtained by multiplying by a conversion factor (density factor). A known literature value or the like can be used as the density coefficient, and can be 1.05, for example. The calculation of the myocardial weight may be performed in step 335 or may be performed in this step. Depending on the embodiment, the myocardial weight calculation algorithm may be implemented in the contour extraction / volume calculation program 124 or may be implemented in the SUV conversion program 120. The calculated myocardial weight may be stored in the main storage device 102 or the mass storage device 106. Depending on the embodiment, it may be stored in a register of the CPU 102.

BCF can be obtained by a known method. For example, a nuclear medicine image can be taken for a vial (or syringe) containing a radiopharmaceutical having a known total radioactivity, and the value calculated by the following equation can be used.

BCF = Attenuation-corrected total activity (Bq) / (Total count of all slices / Collection time (seconds))

Moreover, when calculating | requiring BCF from the data obtained using the cylindrical phantom, the following formula can be used.

Volume coefficient = average count value in 1 slice / (volume of 1 pixel x collection time (seconds))

BCF = Attenuation corrected total activity (Bq) / (Phantom capacity × Volume coefficient)

  Depending on the embodiment, the collection time may be corrected for the BCF. The collection time correction may be performed, for example, by multiplying the BCF by {1 pixel volume [cm3] / collection time [sec]}.

  The image data after the pixel value of each pixel is converted to SUV may be stored as SUV image data 150 in, for example, the mass storage device 106 (see FIG. 1).

  In this embodiment, the myocardial nuclear medicine image data is normalized based on the weight of the myocardium accumulated by the tracer. Therefore, the normalized value reflects the actual state of cardiac function more accurately than in the prior art, and the state of myocardial blood flow can be imaged more objectively. That is, for example, the validity / reliability when comparing data with different measurement dates / times and subjects is improved.

  Depending on the embodiment, normalization may be performed using the myocardial volume instead of the myocardial weight, or normalization may be performed using another index related to the size of the heart.

  In step 350, the calculation result of the myocardial blood flow increase rate is displayed. The method of display can vary. For example, when the SUV image data 150 in which the result is stored is 3D image data in which the pixel value of each pixel is converted to SUV, for example, the position of the corresponding pixel on the short-axis tomographic image or the 3D image Alternatively, it may be displayed as a luminance or color tone according to the SUV value.

  In some embodiments, the nuclear medicine image data to be subjected to SUV conversion may be two-dimensional array data or a two-dimensional polar map instead of three-dimensional data. In that case, since the SUV image data 150 is also two-dimensional array data or a two-dimensional polar map, these may be displayed.

  Although the present invention has been described in detail with reference to the preferred embodiments, the above description and the accompanying drawings are not intended to limit the scope of the present invention, but rather to satisfy the requirements of the law. Is presented. There are various variations in the embodiments of the present invention other than those introduced here. For example, the various numerical values shown in the specification or the drawings are all examples, and these numerical values are not presented with the intention of limiting the scope of the invention. Individual features included in the various embodiments introduced in the specification or drawings may only be used in conjunction with the embodiments where it is directly described that the features are included, and other features described herein. The present invention can also be used in combination in the embodiments and various embodiments not described. In particular, the order of the processes introduced in the flowchart does not have to be executed in the order in which they were introduced. Depending on the practitioner's preference and necessity, the order may be changed or executed concurrently in parallel. These blocks may be implemented in an integral manner or may be implemented as an appropriate loop. All of these variations are included in the scope of the invention disclosed in the present application, and the scope of the invention is not limited by the implementation of processing. The description order of the processes specified in the claims does not necessarily specify the essential order of the processes. For example, an embodiment in which the order of the processes is different, an embodiment in which the processes are executed including a loop, etc. Is also included in the scope of the claimed invention.

  Further, for example, the embodiment of the SUV conversion program 120 includes a program that is a single program, a program group that includes a plurality of independent programs, and a contour extraction / volume calculation program 124. What was integrated in whole or in part may also be included. As is well known, there are various implementation forms of the program, and all of these variations are included in the scope of the invention disclosed in the present application.

  Furthermore, since the new SUV disclosed in the present application is characterized by normalization using an index related to the size of the myocardium, this normalization is appropriate for various nuclear medicine examinations for the heart. The SUV of the present application can be used in all fields having

  Regardless of whether the present claims are claimed or not, the applicant alleges that he has the right to obtain a patent for all forms that do not depart from the spirit of the invention disclosed herein. Note that.

100 system 102 CPU
104 Main storage device 106 Mass storage device 107 Display interface 108 Peripheral device interface 109 Network interface 120 SUV conversion program 124 Contour extraction / volume calculation program

Claims (4)

A method of processing myocardial nuclear medicine image data, wherein the processing means of the apparatus is executed by executing a program command,
Operating said device as a first means for storing a heart parameter, which is a value relating to the size of the heart, and as a second means for storing a radioactive dose;
Using the values stored in the first means and the second means, the pixel values of at least some of the pixels of the image data are expressed by the following formula:

SUV = tissue radioactivity concentration / (radioactivity dose / value based on cardiac parameters)

Converting to SUV and storing;
Including a method.   The method of claim 1, further comprising outputting the SUV.   A computer program comprising program instructions configured to cause the apparatus to perform the method of claim 1 or 2 when executed by a processing means of the apparatus.   An apparatus comprising processing means and storage means, wherein the storage means stores a program instruction, and when the program instruction is executed by the processing means, the method according to claim 1 or 2 is executed. Configured device.

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