Luminescence amount correction method for correcting luminescence amount in luminescence phenomenon-exhibiting biological tissue

Abstract

Provided is a luminescence amount correction method for correcting a luminescence amount in luminescence phenomenon-exhibiting biological tissue. The luminescence amount correction method involves heating biological tissue that exhibits an in-vivo luminescence phenomenon by applying an AC magnetic field to a magnetic fluid injected into the luminescence phenomenon-exhibiting biological tissue, and correcting measurements of a luminescence amount in the luminescence phenomenon-exhibiting biological tissue before and after the heating. The method comprises: a step for determining, in vitro, a change in the luminescence amount with respect to the amount of the magnetic fluid; a step for heating the luminescence phenomenon-exhibiting biological tissue, and calculating the amount of the magnetic fluid contained in the luminescence phenomenon-exhibiting biological tissue, on the basis of a time constant related to a temperature change of the luminescence phenomenon-exhibiting biological tissue; a step for measuring the luminescence amount of the luminescence phenomenon-exhibiting biological tissue injected with the magnetic fluid; and a step for calculating a correction value for the measured luminescence amount on the basis of the calculated amount of the magnetic fluid.

Description

Luminescence intensity correction method for correcting the luminescence intensity of biological tissue that produces luminescence phenomena

[0001] The present invention relates to magnetic hyperthermia, which treats cancer by applying an AC magnetic field to biological tissue, such as tumor tissue, which has been injected with a magnetic fluid and generates luminescence due to luciferase activity, to heat the tumor tissue, and also to a method for correcting the amount of luminescence (luciferase activity value) in the tumor tissue.

[0002] Hyperthermia is attracting attention as a treatment for tumors. This treatment takes advantage of the fact that tumor tissue is more sensitive to heat than normal tissue, and can selectively induce necrosis and shrinkage of tumor tissue. Therefore, it is expected to be a minimally invasive treatment that places less strain on patients than the current common cancer treatments of surgery, chemotherapy, and radiation therapy.

[0003] Conventional heating methods for hyperthermia, such as RF dielectric heating and ultrasound heating, have been proposed and are already in use in medical settings. However, these methods have relatively difficult control over the heating area, and may not be able to selectively heat only tumor tissue. Effective hyperthermia requires continuous heating for a certain period of time to a temperature at which tumor tissue can necrotize. Further increasing the treatment temperature can further enhance tumor necrosis. However, there is a risk that surrounding normal tissue may also be exposed to high temperatures, causing necrosis. Therefore, establishing a successful hyperthermia requires elucidating the temperature and heating time that can treat only tumor tissue without harming normal tissue, and developing a temperature control system. Therefore, magnetic hyperthermia, which involves implanting a magnetic material as a heating element in tumor tissue and applying an AC magnetic field to achieve localized heating, has been proposed and researched, as shown in Figure 10. Figure 10 is a conceptual diagram of magnetic hyperthermia.

[0004] In magnetic hyperthermia, a soft heating method has been proposed in which a magnetic material with a low Curie temperature, known as a thermosensitive magnetic material, is implanted into the body, and the heating temperature is controlled by the change in the material's magnetic properties in response to temperature. However, with this method, the thermosensitive magnetic material is on the order of μm to mm, making it difficult to remove after treatment. Furthermore, precise temperature control for various tumor tissues with different heat resistances is also a difficult issue. Therefore, in animal experiments, a method has been adopted in which nm-order magnetic nanoparticles are implanted into the affected area, and the strength of the applied magnetic field is controlled while measuring the temperature with an optical fiber thermometer.

[0005] Patent Document 1 discloses a method of injecting a hypotonic suspension of magnetic particles into a patient's body and applying an AC magnetic field to the patient for magnetic hyperthermia.

[0006] Furthermore, Non-Patent Document 1 is the research of the present inventors, and discloses a constant temperature heating control method for precisely controlling the applied magnetic field so as to maintain a constant temperature without overshooting and without deviation at the target temperature, in relation to temperature control for heating magnetic nanoparticles injected into a living body by applying an alternating magnetic field in animal experiments.

[0007] Patent Document 2 discloses a cancer treatment device that applies an AC magnetic field of a specific frequency without relying on the thermal effect of magnetic heating.

[0008] International Publication No. WO 2014 / 140543 International Publication No. WO 2018 / 097185

[0009] A. Shikano, L. Tonthat, and S. Yabukami: IEEJ Trans. Electr. Electron. Eng. , 16 , 807 - 809 (2021)

[0010] In animal experiments to confirm the therapeutic effects of magnetic hyperthermia, tumor cells that constitutively express the luciferase gene (i.e., tumor cells that emit light through luciferase activity) are transplanted into the lymph nodes of experimental mice, and magnetic fluid containing magnetic nanoparticles is then injected into the lymph nodes, followed by magnetic heating treatment. Changes in the tumor tissue during treatment (whether the tumor tissue is actually growing or shrinking) can be estimated by measuring the amount of luminescence using, for example, a bioluminescence imaging device.

[0011] One of the present inventors developed a method for generating tumor cells for research purposes that use genetic engineering to generate tumor cells that constitutively express the luciferase gene, i.e., tumor cells that emit light through luciferase activity, and then transplant them into the lymph nodes of experimental mice with lymphadenopathy. By measuring the amount of luminescence generated by the tumor tissue, it is possible to determine the location of the tumor tissue in the body and track its behavior, such as growth, regression, and metastasis, allowing for real-time observation of changes over time.

[0012] The luminescence imaging device is, for example, an in vivo imaging system that measures luminescence due to luciferase activity, receives light emitted by chemical reactions within a living body, and measures the amount of luminescence.

[0013] In magnetic hyperthermia, a magnetic fluid containing metal particles (e.g., nano-sized iron particles) for magnetic heating is injected into tumor tissue, and therefore, when measuring luminescence using a bioluminescence imaging device, changes in tumor cells cannot be accurately measured due to absorption of luminescence by metal particles (magnetic nanoparticles) such as iron contained in the magnetic fluid that remain near the tumor tissue. That is, when measuring luminescence intensity using a bioluminescence imaging device to observe changes in tumor tissue over time during magnetic hyperthermia by injecting magnetic fluid into tumor tissue, changes in luminescence intensity due to changes in tumor tissue as well as changes in luminescence intensity due to absorption of luminescence by the metal particles contained in the magnetic fluid occur, and therefore, changes in luminescence intensity due to changes in tumor tissue may not be accurately measured.

[0014] Therefore, the object of the present invention is to provide a method for correcting the amount of luminescence of biological tissue that generates a luminescence phenomenon in order to accurately observe changes in the biological tissue (tumor tissue), for example, in magnetic hyperthermia, which involves injecting a magnetic fluid containing a metal component into biological tissue that generates a luminescence phenomenon due to luciferase activity and then heating the biological tissue with magnetic heating for treatment.

[0015] In order to achieve the above-mentioned object, the present invention provides a method for correcting the amount of luminescence of biological tissue that causes a luminescence phenomenon, which involves applying an AC magnetic field to a magnetic fluid injected into biological tissue that causes a luminescence phenomenon inside a living organism, heating the biological tissue that causes the luminescence phenomenon, and correcting the measured amount of luminescence of the biological tissue that causes the luminescence phenomenon, and is characterized by comprising the steps of: determining, outside the living organism, the change in the amount of luminescence relative to the amount of magnetic fluid; heating the biological tissue that causes the luminescence phenomenon, and calculating the amount of magnetic fluid contained in the biological tissue that causes the luminescence phenomenon based on a time constant related to the temperature change of the biological tissue that causes the luminescence phenomenon; measuring the amount of luminescence of the biological tissue that causes the luminescence phenomenon into which the magnetic fluid has been injected; and calculating a correction value for the measured amount of luminescence based on the calculated amount of magnetic material.

[0016] A further method of correcting the amount of luminescence of biological tissue causing a luminescence phenomenon according to the present invention comprises heating a preparation containing a light-absorbing component injected into biological tissue causing a luminescence phenomenon inside a living organism and correcting the measured amount of luminescence of the biological tissue causing the luminescence phenomenon, the method comprising the steps of: determining, ex vivo, a change in the amount of luminescence relative to the amount of preparation containing the light-absorbing component; heating the biological tissue causing the luminescence phenomenon and calculating, based on a time constant related to the temperature change of the biological tissue causing the luminescence phenomenon, the amount of preparation containing the light-absorbing component contained in the biological tissue causing the luminescence phenomenon; measuring the amount of luminescence of the biological tissue causing the luminescence phenomenon into which the preparation containing the light-absorbing component has been injected; and calculating a correction value for the measured amount of luminescence based on the calculated amount of preparation containing the light-absorbing component.

[0017] According to the present invention, the luciferase activity value (amount of luminescence) measured for biological tissue inside a living body that produces a luminescence phenomenon due to luciferase activity can be corrected with high precision, and changes in the biological tissue can be accurately measured.

[0018] FIG. 1 is a diagram showing an example of the configuration of a magnetic heating system in an embodiment of the present invention. FIG. 2 is a graph showing the relationship between the biological surface temperature measured by the biological surface temperature measuring unit 16 and the temperature of the magnetic fluid 20. FIG. 3 is a diagram showing an outline of the measurement of (luminescence) amount by a biological luminescence imaging device. FIG. 4 is a flowchart showing a method for measuring the amount of luminescence due to luciferase activity in this embodiment. FIG. 5 is a graph showing the measurement results of the luminescence decay rate. FIG. 6 is a graph showing the measurement results of the amount of luminescence. FIG. 7 is a graph showing an example of the measurement results of temperature change during magnetic hyperthermia treatment. FIG. 8 is a graph showing a time constant corresponding to the passage of time. －１ 1 is a graph showing the value of .lamda.. The graph shows the calibrated amount of light emitted. 2 is a conceptual diagram for explaining magnetic hyperthermia.

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. However, the technical scope of the present invention is not limited to these preferred embodiments.

[0020] 1 is a diagram showing an example of the configuration of a magnetic heating system 100 according to an embodiment of the present invention. A magnetic fluid 20 is injected into tumor tissue, which is the biological tissue that is the target of magnetic heating, for example, tumor tissue near a lymph node of a living organism 30.

[0021] In research into magnetic hyperthermia, animal experiments to confirm the therapeutic effects of magnetic heating involve transplanting tumor cells that constitutively express the luciferase gene, i.e., tumor cells that produce luminescence, into the lymph nodes of experimental mice, injecting a magnetic fluid containing magnetic nanoparticles into the lymph nodes, and then carrying out a treatment process using the magnetic heating system 100 of this embodiment. Changes in luciferase activity in the tumor tissue during the treatment process (whether the tumor tissue actually grows or decreases) can be estimated by measuring the luminescence caused by luciferase activity using, for example, a bioluminescence imaging device.

[0022] Using genetic engineering, known research tumor cells are prepared that constitutively express the luciferase gene, i.e., tumor cells that generate luminescence through luciferase activity, and then transplanted into the lymph nodes of experimental mice. The amount of change in the tumor lesion due to treatment with the magnetic heating system 100 is measured using a bioluminescence imaging device. The bioluminescence imaging device is, for example, an in vivo imaging system that receives luminescence emitted from the luciferase gene in the living body and measures the luciferase activity, i.e., the amount of luminescence.

[0023] Luciferase activity causes tumor tissue to glow, and by measuring this luminescence using a bioluminescence imaging device, it is possible to determine the location of tumor tissue within the body and track its behavior, such as growth, degeneration, and metastasis, and observe changes over time in real time.

[0024] The magnetic heating system 100 controls the heating of a magnetic fluid 20 injected into a site within a living body 30, for example, near a lymph node into which tumor cells have been transplanted, and is configured with a heating unit 12 that applies a magnetic field to the magnetic fluid 20 on the surface of the living body near the lymph node into which the tumor cells have been transplanted to heat the magnetic fluid, a temperature measuring unit 16 that measures the temperature of the living body 30 near the lymph node where the tumor tissue and magnetic fluid 20 are located, and a control unit 18 that controls the heating unit 12 based on the measured temperature.

[0025] The heating unit 12 can use a drive coil 12a and a high-frequency induction heating power supply 12b that drives it, and the drive coil 12a is positioned so that the magnetic fluid 20 injected into the living body 30 is positioned approximately on the center line of the coil axis. The alternating current magnetic field generated from the drive coil 12a heats the magnetic fluid 20 inside the living body. A chiller (not shown) for cooling the heating unit 12 can be provided as needed.

[0026] The temperature measurement unit 16 is a radiation thermometer (thermography) and is a temperature sensor that uses infrared rays to measure the surface temperature of an object, including the living body 30. The temperature measurement unit 16 measures not the temperature of the magnetic fluid 20 itself inside the living body, but the living body surface temperature resulting from the heating of the magnetic fluid 20. Lymph nodes are tissues relatively close to the living body surface, and the living body surface temperature close to the magnetic fluid 20 injected into the lymph nodes changes in a manner that closely correlates with the temperature of the magnetic fluid 20. Therefore, the temperature of the magnetic fluid 20 can be detected by measuring the living body surface temperature. The temperature measurement unit 16 is not limited to thermography, and can also be, for example, an optical fiber thermometer that is directly inserted into tumor tissue inside the living body 30 to measure the temperature.

[0027] 2 is a diagram showing the relationship between the organism surface temperature measured by the organism surface temperature measuring unit 16 and the temperature of the magnetic fluid 20. As the temperature of the magnetic fluid 20 increases (or decreases), the organism surface temperature also increases (or decreases) linearly, and the temperature of the magnetic fluid 20 can be measured based on the temperature measured by the organism surface temperature measuring unit 16.

[0028] The control unit 18 is a computer device that executes the temperature control method of this embodiment. The control unit 18 can be, for example, a general-purpose computer device such as a laptop or desktop PC, and is configured with a storage means (memory such as RAM or ROM, a magnetic disk, etc.) that stores the computer program and various data for executing the temperature control method of this embodiment, and a processing means (CPU, etc.) that executes the computer program. The control unit 18 controls the output of the heating unit 12, which heats the magnetic fluid 20, based on the temperature data acquired from the temperature measurement unit 16. For example, constant-temperature heating control is performed to maintain a therapeutic temperature of 40 to 43°C.

[0029] [Magnetic Fluid] The magnetic fluid used in magnetic hyperthermia is required to be safe as a pharmaceutical product because it is placed in the body. Therefore, when selecting a magnetic fluid, it is desirable to choose one that has been approved as a pharmaceutical product through preclinical trials and clinical trials. For this reason, in this embodiment, we selected Resovist® (Kyowa Critical Care, Tokyo), a medical magnetic fluid that has already been approved as a pharmaceutical product and is used in magnetic hyperthermia research. Resovist® is a magnetic fluid containing magnetic nanoparticles made of iron oxide coated with carboxydextran and with a particle size in liquid of approximately 57 nm.

[0030] In magnetic hyperthermia, a magnetic fluid containing magnetic nanoparticles is injected into tumor tissue, followed by magnetic heating. The changes in tumor tissue caused by treatment can be observed by measuring the amount of luminescence emitted by luciferase activity before and after magnetic heating. For example, a decrease in the amount of luminescence indicates a decrease in the tumor tissue size, whereas an increase in the amount of luminescence indicates an increase in the tumor tissue size. The amount of luminescence is measured using a bioluminescence imaging device.

[0031] 3 is a diagram illustrating the measurement of the amount of luminescence using the bioluminescence imaging device 200. For example, in an animal experiment, tumor cells that generate luminescence due to luciferase activity are transplanted into the subiliac lymph node (SiLN) of an experimental mouse MXH10 / Mo / lpr as a living body 30, and magnetic fluid 20 is further injected. The amount of luminescence is measured before and after magnetic hyperthermia using the bioluminescence imaging device 200. The bioluminescence imaging device 200 captures luminescence associated with luciferase activity emitted from the tumor tissue using the image sensor 204, and performs image processing using the image processing unit 208.

[0032] In measuring the amount of luminescence using the bioluminescence imaging device 200, magnetic nanoparticles such as iron contained in the magnetic fluid 20 that remain near the tumor tissue may absorb the luminescence associated with luciferase activity, making it impossible to accurately measure changes in the tumor tissue. That is, when measuring the amount of luminescence using the bioluminescence imaging device 200 to observe changes in the tumor tissue over time during the process of injecting the magnetic fluid 20 into the tumor tissue and performing magnetic hyperthermia treatment using magnetic heating, not only does the amount of luminescence change due to the luciferase activity resulting from changes in the tumor tissue occur, but also attenuation of the amount of luminescence resulting from the absorption of luminescence by the magnetic nanoparticles contained in the magnetic fluid 20 occurs, making it impossible to accurately measure changes in the amount of luminescence due to changes in the tumor tissue.

[0033] Therefore, in order to accurately measure changes in tumor tissue, this embodiment proposes the following light emission correction method, which corrects the measured light emission amount using a time constant corresponding to the temperature change of the tumor tissue.

[0034] [Light Emission Amount Correction Method] Next, a light emission amount correction method according to this embodiment will be described with reference to the flowchart shown in Fig. 4. Fig. 4 is a flowchart showing the light emission amount correction method according to this embodiment.

[0035] First, an in vitro experiment is conducted to measure the luminescence decay rate corresponding to the amount of Resovist® used as the magnetic fluid 20 (S101). Multiple samples are prepared, each containing a different amount of Resovist® in each container, and the absorbance of light at the same wavelength (e.g., 550 nm) as the luminescence associated with luciferase activity measured by the bioluminescence imaging device 200 is measured for each sample. The light absorption by Resovist® itself weakens the intensity of light emitted from the tumor tissue, and the amount of luminescence from the tumor tissue is attenuated.

[0036] Figure 5 is a graph showing the results of measuring the luminescence decay rate. The luminescence decay rate increases with increasing amounts of Resovist®, and this luminescence decay rate can be approximated by a predetermined exponential approximation. The dotted line in Figure 5 is the approximate curve for the luminescence decay rate.

[0037] In animal experiments using MXH10 / Mo / lpr mice, tumor cells that generate luminescence due to luciferase activity were transplanted into the subiliac lymph nodes (SiLNs) of the mice, and a predetermined amount (e.g., 10 μl) of magnetic fluid 20, Resovist®, was injected into the nodes using a syringe. Magnetic hyperthermia treatment was then performed, and the amount of luminescence associated with luciferase activity before and after treatment was measured using a bioluminescence imaging device (S102). The amount of luminescence before the injection of Resovist® was also measured.

[0038] 1, magnetic hyperthermia is performed by driving the high-frequency induction heating power supply of the heating unit 12 with alternating current at a predetermined frequency, heating the SiLN of the MXH10 / Mo / lpr mouse to a therapeutic temperature of, for example, about 40°C, and controlling the heating to maintain the therapeutic temperature for a certain period of time. Magnetic hyperthermia is performed multiple times (for example, once a day for a predetermined period of time over multiple days), and by measuring the amount of light emitted before and after each magnetic hyperthermia treatment, the progress of the increase or decrease in tumor tissue due to each magnetic hyperthermia treatment can be confirmed each time.

[0039] Figure 6 is a graph showing the results of measuring the amount of luminescence. In the example of measurement in Figure 6, three MXH10 / Mo / lpr mice (mouse 1: filled circle, mouse 2: filled triangle, mouse 3: open square) were implanted with tumor cells that produce luminescence due to luciferase activity, and magnetic hyperthermia was performed four times over four days. The graph shows the changes in the amount of luminescence measured before and after the injection of Resovist (registered trademark) and the four magnetic hyperthermia treatments.

[0040] In the magnetic hyperthermia treatment in S102, the heating unit 12 of the magnetic heating system 100 is activated to start heating the magnetic fluid, and the temperature measurement unit 16 measures the temperature change during heating up to the predetermined treatment temperature. Based on this temperature change, the time constant of the temperature change is calculated (S104). The time constant is the time it takes for the temperature to reach 63% of the equilibrium state at the treatment temperature, and when the measured temperature change is expressed by the following approximate formula (1) using an exponential function, the coefficient m3 corresponds to the time constant: y = m1 + m2 exp(-m3 x) (1)

[0041] Figure 7 is a graph showing an example of the measurement results of temperature changes during magnetic hyperthermia. In this example, the temperature of the living body surface near the tumor tissue is measured by the thermography temperature measurement unit 16, and the average value (avg line) of the temperature distribution with a predetermined spread and the maximum temperature value (max line) of that temperature distribution are graphed. The time constant can be determined from either temperature change, but calculating the time constant from the maximum temperature value (max line), which has higher sensitivity, allows for a time constant with a high signal-to-noise ratio to be determined.

[0042] Based on the calculated time constant, the amount of magnetic fluid 20 near the tumor tissue is calculated (S106). The time constant is a heat response characteristic of the magnetic fluid 20. The larger the amount of magnetic fluid, the steeper the rise in heating becomes, and therefore the smaller the time constant becomes. Therefore, there is a correlation between the time constant and the amount of magnetic fluid. More specifically, the smaller the time constant of the temperature change (1 / time constant (time constant －１ It can be inferred that the larger the value of ) is, the greater the amount of magnetic fluid 20. The magnetic fluid 20 is injected into the lymph node into which the tumor cells have been transplanted, and immediately after injection, it remains near the lymph node. However, as time passes, it gradually flows out of the lymph node, and the amount of magnetic fluid 20 injected near the tumor tissue gradually decreases. The amount of magnetic fluid 20 that has decreased and the amount of magnetic fluid 20 that remains near the tumor tissue at the time of measurement are calculated from the time constant.

[0043] The amount of magnetic fluid after X hours has elapsed since the magnetic fluid was injected is calculated using the following formula (2): Amount of magnetic fluid after X hours has elapsed = Amount of magnetic fluid injected initially (X=0) x Time constant －１(X = magnetic hyperthermia at time 0 (at time of injection)) / time constant －１ (Magnetic hyperthermia treatment after X hours) (2)

[0044] FIG. 8 shows the time constants over time for the three experimental mice in FIG. －１ 1 is a graph showing the change in the amount of magnetic fluid 20 remaining near the tumor tissue. It can be seen that the amount of magnetic fluid 20 generally decreases over time.

[0045] Based on the amount of magnetic fluid 20 calculated in S106 after the predetermined time has elapsed, a correction value for the amount of luminescence measured in S102 is calculated (S108). The measured amount of luminescence is affected by the amount of luminescence corresponding to the size of the tumor tissue, as well as by light absorption by the magnetic fluid 20 remaining near the tumor tissue. Therefore, using the luminescence decay rate calculated in S101 corresponding to the amount of magnetic fluid 20, a correction value for the amount of luminescence that eliminates the influence of light absorption is calculated most simply by, for example, the following formula (3): Correction value for luminescence amount = Measured luminescence amount × luminescence decay rate corresponding to the amount of magnetic fluid (3)

[0046] FIG. 9 is a graph showing the corrected values ​​of the luminescence intensity measurements. The graph in FIG. 6 shows the luminescence intensity measurements before correction. Comparing FIG. 9 with FIG. 6 reveals the following observations from the experimental results. Specifically, in FIG. 6 , the luminescence intensity changes before and after magnetic fluid injection before magnetic hyperthermia treatment. In FIG. 6 , the luminescence intensity decreases for Mouse 1 and Mouse 3 (dotted box P) even before magnetic hyperthermia treatment. In FIG. 9 , the luminescence intensity remains largely unchanged (dotted box Q). This indicates that the luminescence intensity measurements before correction (actual measurements) include the influence of light absorption by the magnetic fluid 20. However, the corrected luminescence intensity values ​​obtained by correcting the luminescence intensity measurements eliminate the influence of light absorption by the magnetic fluid 20 and represent luminescence intensity corresponding only to the size of the tumor tissue. Even after magnetic hyperthermia treatment, differences in the luminescence intensity measurements before and after correction for Mouse 1 and Mouse 3 are observed, suggesting that the luminescence intensity has been correctly corrected.

[0047] For Mouse 2, the measurement results showed no change in the luminescence intensity before and after magnetic fluid injection before magnetic hyperthermia treatment. This is presumably due to the magnetic fluid 20 not being properly injected into Mouse 2's lymph nodes. The luminescence intensity measurements for Mouse 2 over the entire period overlapped and nearly matched the pre- and post-correction values, suggesting that there was little magnetic fluid near the lymph nodes where hyperthermia treatment was performed. If there is a sufficient amount of magnetic fluid 20 near the tumor tissue, the tumor tissue will not be heated and will not change even if hyperthermia treatment is performed. Even if the luminescence intensity correction of this example is performed, there will be no magnetic fluid 20 present and the tumor tissue will not change, so the luminescence intensity should not change. The measurement results for Mouse 2 are considered to indicate this, and complementarily suggest the effectiveness of the luminescence intensity correction method described above in this embodiment.

[0048] As described above, the measured luminescence intensity can be corrected using a time constant determined based on the temperature change measured during magnetic heating therapy, thereby correcting the measured luminescence intensity and measuring an accurate luminescence intensity (luciferase activity value).

[0049] In the above embodiment, an example was described in which a magnetic fluid such as Resovist® was injected into luminescent biological tissue. However, the formulation administered to the living body is not limited to this example. It is also possible to use a formulation containing a different light-absorbing component that absorbs light and changes temperature when heated. The light-absorbing component may be, for example, a metal component such as the iron oxide component contained in the above-mentioned Resovist®, or another inorganic or organic component. Furthermore, the formulation is not limited to a fluid, and may be in other forms such as a powder or solid. Furthermore, the bioluminescence phenomenon used in the measurement is not limited to luminescence due to luciferase activity, and other bioluminescence phenomena may also be used.

[0050] The present invention is not limited to the above-described embodiments, and it goes without saying that the present invention also includes design changes within the scope of the gist, including various modifications and alterations that would be conceivable to a person with ordinary knowledge in the field of the present invention.

[0051] 100: magnetic heating system, 12: heating unit, 12a: driving coil, 12b: high-frequency induction heating power supply, 16: temperature measurement unit, 18: control unit, 20: magnetic fluid (magnetic nanoparticles), 30: living body, 200: living body luminescence imaging device, 204: imaging element, 208: image processing unit

Claims

1. A method for correcting the amount of luminescence measured in a living organism by applying an AC magnetic field to a magnetic fluid injected into biological tissue that produces a luminescence phenomenon inside the living organism to heat the biological tissue that produces the luminescence phenomenon, and correcting the amount of luminescence measured in the biological tissue that produces the luminescence phenomenon, the method comprising the steps of: determining, outside the living organism, the change in the amount of luminescence relative to the amount of magnetic fluid; heating the biological tissue that produces the luminescence phenomenon and calculating the amount of magnetic fluid contained in the biological tissue that produces the luminescence phenomenon based on a time constant related to the temperature change of the biological tissue that produces the luminescence phenomenon; measuring the amount of luminescence of the biological tissue that produces the luminescence phenomenon into which the magnetic fluid has been injected; and calculating a correction value for the measured amount of luminescence based on the calculated amount of magnetic fluid.

2. A method for correcting the amount of luminescence, which involves heating a preparation containing a light-absorbing component injected into biological tissue that causes a luminescence phenomenon inside a living organism, and correcting the amount of luminescence measured in the biological tissue that causes the luminescence phenomenon, the method comprising the steps of: determining, outside the body, a change in the amount of luminescence relative to the amount of preparation containing the light-absorbing component; heating the biological tissue that causes the luminescence phenomenon, and calculating the amount of preparation containing the light-absorbing component contained in the biological tissue that causes the luminescence phenomenon based on a time constant related to the temperature change in the biological tissue that causes the luminescence phenomenon; measuring the amount of luminescence in the biological tissue that causes the luminescence phenomenon, into which the preparation containing the light-absorbing component has been injected; and calculating a correction value for the measured amount of luminescence based on the calculated amount of preparation containing the light-absorbing component.

3. A method for correcting the amount of luminescence according to claim 1 or 2, characterized in that the time constant is determined based on the largest temperature change in the living tissue that causes the luminescence phenomenon.

4. A method for correcting the amount of luminescence according to claim 1 or 2, characterized in that the biological tissue that produces the luminescence phenomenon emits light due to luciferase activity.

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