JP2015010855A - Quantitation of nuclear medicinal image data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish a novel method for quantitation of nuclear medicinal data.SOLUTION: The nuclear medicinal image data and age information of a subject of the nuclear medicinal image data are read, and an index reflecting a radioactivity uptake quantity is calculated. The index is expressed by the formula, {radioactivity quantity in region of interest which is attenuated and corrected÷volume of region of interest}/{administration quantity of radioactivity÷weight excluding fat}. The weight excluding fat is expressed by the formula, {coefficient 1×height+coefficient 2×weight+coefficient 3×age+coefficient 4}. The age is obtained based on the read age information.

Description

  The present invention relates to the processing of nuclear medicine image data, and more particularly to providing a new technique aimed at objectively evaluating the results of a nuclear medicine examination.

  The principle of imaging technology based on nuclear medicine techniques such as PET, SPECT, and scintigraphy is that a drug (radiopharmaceutical drug) marked with a radioactive substance is administered into the body, and radiation emitted from the body is detected and imaged. That's it. If there is an abnormality in the tissue, the state of metabolism of the radiopharmaceutical changes as compared to the normal tissue. Therefore, by selecting and using a radiopharmaceutical having a desired metabolic characteristic, it is possible to image abnormal tissue function.

  A primary image obtained by PET, SPECT or the like is an image of the count value of radiation. In such an image, a region where the radiopharmaceutical is highly integrated is displayed brightly. That is, the pixel corresponding to the part has a high pixel value. However, since the radioactivity count value is affected by various factors, it is not always clear whether the corresponding tissue has an abnormality just because the pixel value of a specific pixel or region of interest is high. Therefore, attempts have been made to objectively evaluate pixel values by standardizing each pixel value according to a certain rule. SUV (Standardized Uptake Value) is the most famous as such a standardized value. SUV has the following values.

[Formula 1]
SUV = {radioactivity in the region of interest corrected for attenuation (kBq) ÷ volume of interest (ml)} / {radioactivity dose (MBq) ÷ subject's body weight (kg)}

  That is, the SUV is a value obtained by normalizing the radioactivity concentration of the region of interest by the radioactivity dose per body weight, and is a value that can serve as an index reflecting the radioactivity or radiopharmaceutical intake.

  The SUV was expected to have the same value regardless of the subject for tissues that worked in the same way. That is, for example, it is expected that the liver tissue without abnormality has the same value regardless of the subject, and the lung tissue with abnormality has the same value regardless of the subject. It had been. If so, it is possible to compare a plurality of measurement results from different subjects or a plurality of measurement results from the same subject but at different times. (The conversion of the measured value into a comparable value is referred to as “quantification” in the technical field of the present application.)

  However, it has been found that SUVs actually vary considerably depending on the subject's weight, even in tissues that work in the same way.

  FIG. 1 quotes Fig. 1a of Non-Patent Document 1 below. In this figure, the SUV of a specific tissue in which no abnormality is observed is measured for various subjects, and this is graphed with the horizontal axis representing the body weight. (In the figure, it is described as SUVbw. Here, bw means that the whole body weight of the subject is used. See Non-Patent Document 1.) As is apparent at first glance, the weight increases. It can be seen that SUV also tends to increase. Therefore, it can be understood that SUV is not always appropriate as an objective index indicating tissue abnormality.

Therefore, at present, in clinical applications, in particular, a value obtained by correcting the SUV by using a weight excluding fat (referred to as lean body weight) is often used instead of a simple weight. The normalized amount corrected based on this concept is called SUV _lbm or SUL and is defined as follows.

[Formula 2]
SUL = {Attenuation-corrected radioactivity in the region of interest (kBq) ÷ region of interest volume (ml)} / {radioactivity dose (MBq) ÷ subject's lean body mass (kg)}

However, in Equation 2, the lean body weight of the subject is determined using the James definition formula. James's definition is as follows.
Female: 1.07 × (weight)-148 × (weight / height) ²
Male: 1.1 (weight)-120 (weight / height) ²

FIG. 2 quotes Fig. 1c of Non-Patent Document 1 below. SUL (SUV _lbm ) was calculated using the same data as in FIG. 1 and plotted on a graph. According to the experimental results shown in this figure, the SUL exhibits a similar value regardless of the body weight.

  As described above, SUL is considered to exhibit the same value regardless of the patient depending on the presence or absence of the lesion, and its usefulness is widely recognized. In particular, in the United States, it is standardized as a method for determining the therapeutic effect by PET. PERCIST (PET Response Criteria in Solid Tumors).

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.

  However, when the present inventor performed comparison between SUL subjects at a specific site using several hundreds of FDG-PET application examples in a hospital where the present inventor is present, the results shown in FIG. Was found (see FIG. 3-5). According to the experiment results of the present inventor, unlike the academic findings so far, SUL has weight dependence. Then, even if it is SUL, it will not necessarily be suitable for using for the determination of a therapeutic effect.

  For example, patients who have been treated with anti-cancer drugs may lose weight significantly due to side effects. In such a case, if there is weight dependence in the SUL, it would be meaningless to compare the SUL before and after the anticancer drug treatment, and the therapeutic effect cannot be determined using the SUL. End up.

  For this reason, it has become urgent to establish a new method for quantifying nuclear medicine data.

  The inventor of the present application has examined the cause of weight dependence of SUL and arrived at two hypotheses. One of them is the hypothesis that the lean body mass estimation method included in the SUL calculation formula is appropriate for Westerners but not for other races such as Japanese. Actually, including the example introduced in FIG. 2, all existing data indicating that the SUL is not dependent on weight has been obtained with westerners as subjects, and other races such as Japanese as subjects. What was going on wasn't being investigated. This is because race was not thought to have an effect on the estimation of lean body mass.

  The other is the hypothesis that James's formula does not include an age component, which may have an adverse effect on lean body mass estimation.

  The inventor of the present application considers how fat is added depending on the food culture and lifestyle and also changes depending on the age. Then, it may not be possible to accurately estimate lean body mass without considering these race and age factors, and even if SUV is corrected without taking these factors into account, For example, it may not be an appropriate correction for the Japanese.

  Therefore, the inventor of the present application investigated whether there is an appropriate method for estimating lean body mass for Japanese. As a result, we found a paper with a large sample size (2411 cases) in which the body composition of Japanese was investigated by the DXA method. (H Ito, et.al. European Journal of Clinical Nutrition (2001) 55, 462-470., Hereinafter referred to as Ito paper)

  According to the Ito paper, the lean body mass of Japanese people can be approximated by the following linear expression with height, weight, and age as variables.

[Formula 3]
Japanese lean body mass (kg) = factor 1 x height (m) + factor 2 x body weight (kg) + factor 3 x age + factor 4

According to the Ito paper, the coefficients 1 to 4 in Equation 3 are as follows. In the table, parentheses indicate standard errors.

  The inventor of the present application calculated the same amount as that of SUL using the Japanese lean body mass obtained from the equation (1). That is, when this new amount is expressed as SULj, SULj is expressed as follows.

[Formula 4]
SULj = {Attenuation corrected radioactivity in the region of interest (kBq) ÷ region of interest volume (ml)} / {radioactivity dose (MBq) ÷ Japanese lean body mass (kg)}

  The inventor of the present application calculated SUV, SUL, SULj for various tissues using FDG-PET data of normal tissues of a large number of Japanese subjects, and plotted them on a graph with the horizontal axis as the body weight. Some of the results are introduced in FIGS.

FIG. 3 is a graph showing the results of calculating SUV, SUL, and SULj from lung tissue and taking the weight on the horizontal axis. That is, for example, SULj in this figure is a value calculated by substituting the amount of radioactivity and volume of lung tissue as the amount of radioactivity in the region of interest and the region of interest volume, respectively, and substituting these into equation 4.
About the result shown in FIG. 3, when each normalized quantity is approximated by a linear expression, as shown in the figure, y = 0.0061x + 0.0971 for SUV, y = 0.0043x + 0.1015 for SUL, For SULj, the result was y = 0.0019x + 0.1657. Although SUV, SUL, and SULj are also dependent on body weight, the degree of SULj is clearly smaller than the other two. This is consistent with the impression obtained from FIG. Thus, it was shown that the weight dependence of the normalized amount can be reduced by using SULj for Japanese.

FIG. 4 shows SUV, SUL, SULj calculated from liver tissue, and the results are graphed by taking the weight on the horizontal axis as in FIG. That is, for example, SULj in this figure is a value calculated by substituting the amount of radioactivity and volume of the liver tissue as the amount of radioactivity in the region of interest and the region of interest volume, respectively, and substituting them into Equation 4.
Referring to FIG. 4, SULj has little or no weight dependence. On the other hand, clear weight dependence is seen about SUV and SUL. As in the case of the lung, when each normalized amount is approximated by a linear expression, the slope of the SUV approximate expression is 0.0168 and the slope of the SUL approximate expression is 0.0112 as shown in the figure. On the other hand, the slope of the approximate expression of SULj is 0.0008, which indicates that there is almost no slope. The survey results on the liver also showed that the weight dependence of the normalized amount can be reduced by using SULj for Japanese.

FIG. 5 is a graph of SUV, SUL, SULj calculated from spleen tissue and the weight is plotted on the horizontal axis in the same manner as in FIG. That is, for example, SULj in this figure is a value calculated by substituting the amount of radioactivity and volume of the spleen tissue as the amount of radioactivity in the region of interest and the region of interest volume, respectively, and substituting them into Equation 4.
As can be seen from FIG. 5, SULj does not depend on body weight even in spleen tissue. On the other hand, clear weight dependence is seen about SUV and SUL. As in the case of the lung and liver, when each normalized amount is approximated by a linear expression, as shown in the figure, the slope of the approximate expression of SULj is -0.0001, which indicates that there is almost no inclination. It was. Therefore, the results of the investigation on the spleen have also shown that the weight dependence of the normalized amount can be reduced by using SULj, at least for the Japanese.

  As is clear from the experimental results introduced in FIGS. 3 to 5, SULj represented by Equation 4 is significantly smaller in weight dependence than SUV and SUL (or does not have weight dependence), and the measurement time It can be understood that this is a very convenient index for comparing the results of different nuclear medicine tests of subjects and subjects.

  From these experimental results, we estimate lean body mass using a linear equation with height, weight, and age as variables, and normalize the radioactivity concentration of the region of interest using the estimated lean body weight, It was found that comparable values could be obtained between multiple nuclear medicine data with different subjects and measurement times.

  Therefore, in the embodiment of the present invention, the process of calculating the lean body mass using a linear expression having height, weight, and age as variables, and the normalization of the radioactivity concentration of the region of interest using the estimated lean body weight are performed. Processing to be performed. With these features, comparable information can be obtained from data obtained by nuclear medicine techniques. That is, quantification of nuclear medicine data is realized.

Examples of preferred embodiments of the present invention include the following systems. The system includes a processing unit and a storage unit that stores a program, and the program is executed by the processing unit, whereby the system includes:
(A) reading nuclear medicine image data;
(B) reading subject's age information of the nuclear medicine image data;
(C) calculating an index reflecting radioactivity uptake;
Is configured to execute at least. Here, the index is a value that can be expressed by the following equation 4 ′.

[Formula 4 ']
Index reflecting radioactivity uptake = {radioactivity in region of interest corrected for attenuation ÷ volume of region of interest} / {radioactivity dose ÷ lean body mass}

  However, in the formula 4 ′, “lean body weight” is a value that can be expressed by the following formula 3 ′.

[Formula 3 ']
Lean body mass = factor 1 x height + factor 2 x body weight + factor 3 x age + factor 4

  Moreover, the age in Formula 3 ′ is a value obtained based on the age information read in step (b).

Examples of preferred embodiments of the present invention include the following computer program. When this computer program is executed by the processing means of the system,
(A) reading nuclear medicine image data;
(B) reading subject's age information of the nuclear medicine image data;
(C) calculating an index reflecting radioactivity uptake;
Comprises instructions configured to at least execute. Here, the index is a value that can be expressed by the following equation 4 ′.

[Formula 4 ']
Index reflecting radioactivity uptake = {radioactivity in region of interest corrected for attenuation ÷ volume of region of interest} / {radioactivity dose ÷ lean body mass}

  However, in the formula 4 ′, “lean body weight” is a value that can be expressed by the following formula 3 ′.

[Formula 3 ']
Lean body mass = factor 1 x height + factor 2 x body weight + factor 3 x age + factor 4

  Moreover, the age in Formula 3 ′ is a value obtained based on the age information read in step (b).

Examples of preferred embodiments of the present invention include the following methods. The computer program is a method performed by the system by being executed by the processing means of the system,
(A) reading nuclear medicine image data;
(B) reading subject's age information of the nuclear medicine image data;
(C) calculating an index reflecting radioactivity uptake;
At least. Here, the index is a value that can be expressed by the following equation 4 ′.

[Formula 4 ']
Index reflecting radioactivity uptake = {radioactivity in region of interest corrected for attenuation ÷ volume of region of interest} / {radioactivity dose ÷ lean body mass}

  However, in the formula 4 ′, “lean body weight” is a value that can be expressed by the following formula 3 ′.

[Formula 3 ']
Lean body mass = factor 1 x height + factor 2 x body weight + factor 3 x age + factor 4

  Moreover, the age in Formula 3 ′ is a value obtained based on the age information read in step (b).

  As described above, the coefficients 1 to 4 in Table 1 are coefficients obtained from a study that approximated a lean body mass using a data of 2,400 Japanese people and a lean equation for the weight, weight, and age as variables. In view of the fact that SUL adapted to Westerners was not adapted to Japanese, the coefficient appearing in the approximate expression may vary depending on race. Since the method for obtaining these coefficients is described in the aforementioned Non-Patent Document 1, some practitioners of the present invention prefer to prepare a new data set and independently obtain and use the coefficients 1 to 4. Some will be there. The invention specified in the scope of claims of the present application naturally includes such embodiments.

It is the figure which quoted fig.1a of the nonpatent literature 1, and is an experimental result which showed that the SUV currently used has a weight dependence. It is the figure which quoted fig.1c of a nonpatent literature 1, and is a figure which shows the experimental result that there is no weight dependence in SUL. It is a figure which shows the examination result of the weight dependence of SUV, SUL, and SULj by experiment of this inventor. A lung region is selected as the region of interest. It is a figure which shows the examination result of the weight dependence of SUV, SUL, and SULj by experiment of this inventor. A liver region is selected as the region of interest. It is a figure which shows the examination result of the weight dependence of SUV, SUL, and SULj by experiment of this inventor. The spleen region is selected as the region of interest. 1 is a diagram for explaining a main configuration of an exemplary system 100 capable of implementing processing according to the present invention. FIG. It is a flowchart for demonstrating the flow of the process which the system 100 which is an Example of this invention performs when the SULj analysis program 120 which is an Example of this invention is run by CPU102. It is a figure which introduces an example of the mode of ROI setting in a certain example. It is a figure which introduces an example of the mode of ROI setting in a certain example.

  Hereinafter, more specific examples of preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 6 is a diagram for explaining a main configuration of a system 100 for executing various processes disclosed in this specification. As illustrated in FIG. 6, the system 100 is similar to a general computer in hardware, and includes a CPU 102, a main storage device 104, an auxiliary storage device 106, a display interface 107, a peripheral device interface 108, a network interface. An interface 109 or the like can be provided. Similar to 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 auxiliary storage device 106. . 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 a peripheral device interface 108. The network interface 109 can be used to connect to another computer or the Internet via a network. The most basic functions of the system 100 are provided by the CPU 102 executing an operating system (OS) 110 stored in the auxiliary storage device 106. Further, characteristic functions of the system 100 are provided by the analysis program 120 being executed by the CPU 102. The analysis program 120 is configured to be implemented in the system 100 by executing the analysis program 120 by the CPU 102, in particular, the function for calculating the aforementioned SULj.

  The auxiliary storage device 106 may be capable of storing various data files in addition to the OS 110 and the program 120. The illustrated original image data file 132 is a data file including a nuclear medicine image, and is a file including data to be analyzed by the SULj analysis program 120. In the embodiment described here, the nuclear medicine image included in the data file 132 is an image obtained by FDG-PET measurement, and is a three-dimensional image in which each pixel has a value corresponding to the radiation count number. However, it should be noted that the present invention is applicable not only to such PET images but also to various nuclear medicine images such as SPECT and scintigraphy.

  The measurement condition data file 134 stores various conditions related to the PET measurement from which the PET image included in the original image data file 132 is created. This condition may include one or more of the administration time and type of the radiopharmaceutical, the start and end times of radiation measurement by the PET device, the height, weight, age, sex, race, nationality, and birthplace of the subject, depending on the embodiment. May be born. Depending on the embodiment, the contents of the measurement condition data file 134 may be integrated into the original image data file 132 as part of the original image data file 132, for example, included in the header thereof. is there. In some embodiments, at least one of the conditions included in the data file 134 may be input by a user using a keyboard or the like connected to the peripheral device interface 108. The correction data file 136 is a data file that stores various types of correction information used for analysis of PET images. Such correction information may include, for example, information for correcting the effect of radiation absorption / scattering in the body and information for correcting attenuation of radioactivity due to decay of radionuclides. Depending on the embodiment, the content of the correction data file 136 may be included in the original image data file 132 or may be included in the SULj analysis program 120. The coefficient data file 138 is a data file that stores coefficients used when the SULj analysis program 120 calculates lean body mass that appears in the above-described calculation of SULj. For example, it is a data file storing the coefficients 1 to 4 shown in Table 1 necessary for the calculation of the above-described equation 3 ′. Depending on the implementation, the contents of the coefficient data file 138 may be integrated into this program as part of the SULj analysis program 120. The processing result data file 140 is a data file that stores an analysis result obtained by the SULj analysis program 120.

  It should be noted that the data files 132 to 140 are often not stored in the auxiliary storage device 106 when the system 100 is manufactured and sold or activated. In other words, for example, the original image data file 132 is often data that has been transferred to the system 100 via the network interface 109 after the system 100 is activated, for example. As described above, in some embodiments, the data files 134, 136, and 138 do not exist as independent data files, and their contents are integrated into the SULj analysis program 120 and the original image data file 132. Sometimes it is. The processing result data file 140 does not exist before analysis by the SULj analysis program 120 is performed. Accordingly, it should be noted that the illustrated data files 132-140 are not a required component of an embodiment of the present invention. It should be noted that there may be a case where a plurality of data files 132 to 140 are stored instead of only one. For example, a plurality of original image data files 132 to be analyzed by the SULj analysis program 120 may be stored in the auxiliary storage device 106. Each of these data files 132 corresponds to, for example, a PET image obtained by measuring the same subject at different times, or a PET image obtained by measuring a different subject. There will be. Corresponding to the existence of a plurality of data files 132, a plurality of processing result data files 140 may also exist. Depending on the embodiment, the SULj analysis program 120 may be configured so that the contents of the plurality of data files 140 can be displayed in a comparable manner.

  In addition to the elements depicted in FIG. 6, the system 100 can have a configuration similar to that of an apparatus included in a normal computer system, such as a power supply and a cooling device. Various types of computer system implementations are known, such as those using storage device distribution / redundancy and CPU virtualization, but what is disclosed in this specification? It may be mounted on a computer system of any form. The items disclosed in this specification are 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 executing the program by the processing means, and (3) a process configured to execute the program and the program. The present invention can be embodied as an apparatus or a system including means.

  Next, a flow of processing performed by the system 100 when the SULj analysis program 120 is executed by the CPU 102 will be described with reference to FIG.

  Step 200 indicates the start of processing. In step 202, at least a part of the original image data file 132 is copied to the main storage device 104 as preparation for performing analysis processing by the SULj analysis program 120. In step 204, information on PET measurement conditions related to image data included in the original image data file 132 is acquired. This step is performed by loading the aforementioned measurement condition data file 134 in some embodiments. In another embodiment, it is performed by reading various condition information stored in the original image data file 132. In yet another embodiment, various conditions may be received from a keyboard or the like connected via the peripheral device interface 108. At this time, the CPU 102 according to the instruction of the SULj analysis program 120 may display a message indicating that the measurement condition should be input on the display connected thereto via the display interface 107.

  In step 206, various information for correcting the image data (count number) included in the original image data file 132 is acquired. Such correction information may include, for example, information for correcting the effect of radiation absorption / scattering in the body and information for correcting attenuation of radioactivity due to decay of radionuclides. In some embodiments, this information may be done by reading the correction data file 136. In another embodiment, a function for calculating such correction information may be incorporated in the SULj analysis program 120, and a part of the measurement condition information obtained in step 204 (for example, administration start time of radiopharmaceuticals). The CPU 102 may calculate the correction information based on the command of the SULj analysis program 120 based on the type, type, subject's head circumference, chest circumference, and waist circumference. In yet another embodiment, the image data included in the original image data file 132 may already be data that has been subjected to the necessary correction, in which case step 206 is not necessary.

  In step 208, coefficient information used for calculating the lean body mass necessary for the above-described calculation of SULj (step 212 described later) is acquired. In some embodiments, obtaining coefficient information may include reading a coefficient data file 138. Examples of the coefficient information are coefficients 1 to 4 shown in Table 1, for example. As is apparent from Table 1, the values of the coefficients 1 to 4 depend on the sex. Accordingly, step 208 may include searching the coefficient data file 138 or another database (not shown) for a coefficient that matches the subject's sex information acquired in step 204. As described above, the coefficients 1 to 4 in Table 1 are coefficients obtained from a study that approximated a lean body mass using a data of 2,400 Japanese people and a lean equation for the weight, weight, and age as variables. In view of the fact that the SUL that fits Westerners does not fit Japanese, the coefficients 1 to 4 in Table 1 may vary depending on race. Accordingly, step 208 may include searching the coefficient data file 138 or another database (not shown) for a coefficient that matches these based on information such as the nationality and race of the subject acquired in step 204. . In some embodiments, these coefficients may be included in the program as part of the SULj analysis program 120. In this case, it is not necessary to read the coefficient data file 138 in step 208 or access an external database (not shown) storing these coefficients. In some embodiments, the coefficients 1 to 4 in Table 1 may be described in advance in the source code of the calculation formula used in the lean body mass calculation step (step 212) described later. In this case, the coefficient information acquisition step 208 is unnecessary, and it is only necessary to select a calculation formula that fits the sex of the subject.

  Step 210 is a step of setting a region of interest (ROI) from which SULj is derived. The region of interest may be the entire body, for example, or may be a specific organ such as the brain, lungs, heart, liver, spleen, or bone. It may also be a specific area within these organs. Depending on the embodiment, each pixel may be regarded as a region of interest, or a small number of pixels (for example, a region surrounded by 3 pixels × 3 pixels × 3 pixels in the xyz direction) may be set as a region of interest. there will be. The region of interest may be set automatically, or manually or semi-automatically. There are already many examples of methods for setting a region of interest for data analysis in nuclear medicine images such as PET and SPECT, and such software is also included in the attached software such as PET and SPECT devices. There are many cases. Automatic extraction of organ regions transforms a nuclear medicine image to be analyzed into a standard human body shape (or transforms the standard human body shape into a shape similar to the analysis target image) and corresponds to each organ in the standard human body shape The region is often regarded as each organ region in the nuclear medicine image to be analyzed. When the region of interest is manually set, a desired section of the analysis target image can be displayed on a display and set by surrounding a desired range with a mouse or the like. In addition, the system may display several candidates for the region of interest and manually adjust the shape of the candidate using a mouse or the like. The SULj analysis program 120 preferably includes a set of instructions that are executed by the CPU 102 to implement these region-of-interest setting functions in the system 100. However, there is an embodiment in which the region of interest is always the entire image, a specific region, or each pixel, and no special processing for ROI setting is performed, and the default region is the region of interest. sell.

8 and 9 show specific examples of ROI setting. FIG. 8 is an example in which an ROI is set in the lung region. In this example, the ROI can be set by selecting a desired location of the tomographic image 800 displayed on the display connected to the display interface 107 with the mouse connected to the peripheral device interface 108. It is configured as follows. For example, when the mouse cursor is positioned on the tomographic image 800, the mouse button is pressed at a desired location, the mouse is moved as it is, and the mouse button is released at the desired location, the button operation and the movement operation are performed on the screen. A circle 802 is drawn and the ROI can be configured to be set within a sphere whose cross-section is this circle. This example is configured so that the statistical data 804 of the ROI is automatically calculated and displayed, and the volume of the sphere that becomes the ROI is 37.60 cm ³ , and the maximum value, the minimum value, and the standard deviation of the SULj are respectively It is calculated and displayed as 1.78, 1.43, 0.11. FIG. 9 shows a state in which the ROI is set on the axial, coronal, and sagittal cross-sectional views. In FIG. 9, circles or ellipses 902a to 902g are drawn. These are all circles or ellipses drawn by the mouse operation as described above. The ROI is set as a sphere or ellipsoid whose cross section is a circle or an ellipse. The SULj analysis program 120 is preferably configured to be implemented in the system 100 by executing the ROI setting function using the mouse as described above by being executed by the CPU 102.

  In step 212, the lean body weight of the subject shown in the image data 132 is calculated. This calculation is performed according to Equation 3 or Equation 3 ′ described above. Expression 3 ′ is re-displayed as follows.

[Formula 3 ']
Lean body mass = factor 1 x height + factor 2 x body weight + factor 3 x age + factor 4

  In a preferred embodiment, the lean body mass and the unit of body weight are kg and the height unit is meters. That is, it is the same as Equation 3. However, in some embodiments, g may be used instead of kg, and cm may be used instead of meters. When the unit changes, the coefficients 1 to 4 also change. Therefore, the values of the coefficients 1 to 4 may vary depending on the embodiment depending on the unit of height and weight.

  Although the calculation of lean body mass is performed according to equation 3 ′, equation 3 ′ does not have to be directly described in the source code of the SULj analysis program 120. Depending on the source code, only the first two terms may be calculated first, and the latter two terms may be calculated later. Depending on the source code, the height and weight may be described as (100 cm + 70 cm) or (50 kg + 20 kg), for example, and there may be two or more terms multiplied by a factor of 1, for example. However, all such forms fall within the scope of the claimed invention, and the lean body mass can be understood as being calculated according to Equation 3 or Equation 3 ′. All fall within the scope of the claimed invention.

  In step 214, SULj is calculated. This calculation is performed according to the above-described Equation 4 or Equation 4 ′. Expression 4 ′ is reprinted as follows.

[Formula 4 ']
SULj = {radioactivity amount in region of interest corrected for attenuation ÷ volume of region of interest} / {radioactivity dose ÷ lean body mass}

  The region of interest appearing in Equation 4 ′ is the region of interest set in step 210 (or a region defined by default). In some embodiments, the amount of radioactivity within the region of interest can be a cumulative value of pixel values within the region of interest. “Attenuation-corrected radioactivity in the region of interest” refers to the radioactivity including corrections for the effects of absorption and scattering by body tissues and the decay of radionuclides based on the correction information obtained in step 206. It is. Depending on the embodiment, these corrections may already be included in the pixel value of the data 132 to be analyzed. In this case, it is not necessary to newly perform attenuation correction in step 214.

  The “region of interest volume” in Equation 4 ′ can be a value depending on the number of pixels in the region of interest in a preferred embodiment. The “radioactivity dose” in equation 4 ′ can be the information obtained in step 204. The “lean body weight” in the equation 4 ′ is the value obtained in step 212.

  In a preferred embodiment, the unit of “attenuation corrected radioactivity in the region of interest” is kBq, the unit of “region of interest volume” is ml, the unit of “radioactivity dose” is MBq, The unit of fat body weight is kg. That is, it is the same as Equation 4. However, it will be appreciated that embodiments of the invention are not limited to the use of these units.

  Although the calculation of lean body mass is performed according to equation 4 ′, equation 4 ′ does not have to be directly described in the source code of the SULj analysis program 120. Depending on the source code, the denominator may be calculated first, and the numerator may be calculated later. Regarding the calculation of molecules, depending on the source code, the amount of radioactivity in the region of interest may be calculated and corrected for attenuation, and then divided by the region of interest volume, or {radioactivity in the region of interest ÷ region of interest volume} In some cases, the calculation is done first, and it is multiplied by a correction term for attenuation correction. The same applies to step 212, but there can be various variations in how to write the source code for calculating SULj. However, all such variations are within the scope of the claimed invention without exception as long as SULj can be understood as being performed according to Equation 4 or Equation 4 ′.

  If a plurality of regions of interest are set, step 214 may be repeated for each region of interest.

  Step 216 represents a process of storing the SULj calculation result in the main storage device 104 and / or the auxiliary storage device 106. The data file storing the calculation result is exemplified as the processing result data 140 in FIG. Depending on the embodiment, a plurality of processing result data 140 corresponding to each subject may be stored as a result of analyzing a plurality of data 132 having different test subjects and measurement times.

  Step 218 represents processing for displaying the calculated SULj. This display can vary. For example, in an embodiment in which each pixel or a partition by a small number of pixels is regarded as a region of interest, SULj is calculated for each pixel or partition, and can be displayed as if it were a 3D image or a tomographic image. . That is, it is possible to provide a nuclear medicine image represented by shading based on the value of SULj, instead of a normal nuclear medicine image represented by shading based on the radiation count value. A nuclear medicine image represented by shading based on the radiation count value is an image that is difficult to compare with other nuclear medicine images of different subjects and measurement times, but a nuclear medicine image represented by shading based on the value of SULj If so, the comparison is possible as described above. Depending on the embodiment, the change in SULj in a specific region of interest (for example, a specific organ) of a plurality of nuclear medicine images with different measurement times of the same subject may be displayed as a graph with time on the horizontal axis. As mentioned above, SULj is an index that reflects the amount of radioactive uptake, that is, an index that reflects the metabolic function of the tissue, so such a graph shows how tissue abnormalities change over time. In addition, it can be useful information to see whether the effect of the treatment is seen when the treatment is given.

  Step 220 represents the end of the process.

  While embodiments of the present invention have been described using preferred examples, these examples have not been introduced to limit the scope of the present invention, but to meet the requirements of the patent law and contribute to an understanding of the present invention. It was introduced in. The present invention can be embodied in various forms, and there are many variations in the embodiments of the present invention other than those exemplified here. The individual features included in the various described embodiments can only be used with the embodiments in which the features are directly described, and are not limited to the other embodiments and descriptions described herein. It can also be used in combination in various implementations that are not. In particular, the order of the processes introduced in the flowchart does not necessarily have to be executed in the order in which they are introduced. Depending on the preference of what is to be implemented, the order may be changed or executed concurrently in parallel. May be implemented inseparably, or may be implemented as an appropriate loop. In some embodiments, some of the blocks in the flowchart may not be implemented. For example, as described above, there may be an embodiment in which the steps 206, 208, and 210 are unnecessary. All of these variations are included in the scope of the present invention. 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. Regardless of whether a claim is made in the current claims, the applicant claims to have the right to obtain a patent for all forms that do not depart from the spirit of the present invention. Keep in mind.

Claims (2)

A system comprising processing means and storage means for storing a program, the program being executed by the processing means,
(A) reading nuclear medicine image data;
(B) reading subject's age information of the nuclear medicine image data;
(C) calculating an index reflecting radioactivity uptake;
At least, wherein the index is a value that can be expressed by the following equation (1):

Index reflecting radioactivity uptake amount = {radioactivity in region of interest corrected for attenuation ÷ volume of region of interest} / {radioactivity dose ÷ lean body mass} (1)

In formula (1), “lean body weight” is a value that can be represented by the following formula (2):

Lean body mass = factor 1 x height + factor 2 x body weight + factor 3 x age + factor 4 (2)

The age in Formula (2) is a value obtained based on the age information read in the step (b). By being executed by the processing means of the system,
(A) reading nuclear medicine image data;
(B) reading subject's age information of the nuclear medicine image data;
(C) calculating an index reflecting radioactivity uptake;
A computer program comprising instructions configured to execute at least
The index is a value that can be expressed by the following formula (1):

Index reflecting radioactivity uptake amount = {radioactivity in region of interest corrected for attenuation ÷ volume of region of interest} / {radioactivity dose ÷ lean body mass} (1)

In formula (1), “lean body weight” is a value that can be represented by the following formula (2):

Lean body mass = factor 1 x height + factor 2 x body weight + factor 3 x age + factor 4 (2)

The age in Formula (2) is a computer program which is a value obtained based on the age information read in the said step (b).