MRI imaging marker

Abstract

To provide a marker for MRI imaging which can be an indicator of a position in an MRI image.SOLUTION: A marker (1) for MRI imaging comprises: a non-magnetic container (2); and an MRI contrast medium contained in the container (2).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a marker for MRI imaging for identifying the position of a lesion. [Background technology]

[0002] In recent years, advances in diagnostic technology have made it possible to detect minute lesions (small lesions) in the body and perform surgical treatments such as surgery. For example, methods have been developed to identify the location of small lesions using imaging diagnostic methods such as computed tomography (CT) or magnetic resonance imaging (MRI). Non-Patent Document 1 discloses a method in which a microcoil is placed near the lesion under CT guidance before surgery, and the lesion is resected based on the position of the microcoil. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Mayo et al. Lung nodules: CT-guided placement of microcoils to direct video-assisted thoracoscopic surgical resection. Radiology. 2009;250:576-585. Summary of the Invention [Problem to be solved by the invention]

[0004] CT and MRI can detect small lesions that are difficult to detect with ultrasound. However, these methods lack the ability to perform real-time imaging diagnosis like ultrasound. Therefore, surgery must be performed after accurately determining the location of small lesions through imaging diagnosis. However, in organs such as the liver that are not fixed to a skeleton, the location of small lesions is likely to change between the time of imaging and the time of surgery.

[0005] The method described in Non-Patent Document 1 is applicable to CT, but not to MRI, which can detect small lesions that are difficult to detect with CT. This is because there are many limitations to the procedure, such as the inability to detect metallic materials such as microcoils with MRI and the inability to use metallic devices due to the strong magnetic field generated by MRI.

[0006] An object of one aspect of the present invention is to provide a marker for MRI imaging that can be used as an index of a position in an MRI image. [Means for solving the problem]

[0007] In order to solve the above problems, an MRI imaging marker according to one aspect of the present invention includes a non-magnetic container and an MRI contrast agent contained in the container.

[0008] An MRI imaging marker according to one embodiment of the present invention may have a contrast region containing the MRI contrast agent and a non-contrast region not containing the MRI contrast agent, and at least two of the contrast regions may be formed at positions sandwiching at least one of the non-contrast regions.

[0009] In one embodiment of the MRI imaging marker of the present invention, the contrast region may be formed by two or more tubular portions of the container containing the MRI contrast agent, and the non-contrast region may be a region sandwiched between at least two of the tubular portions.

[0010] In the MRI imaging marker according to one aspect of the present invention, the contrast region may be formed by arranging the cylindrical portions in a grid pattern.

[0011] In the MRI imaging marker according to one aspect of the present invention, the container may be made of a flexible resin. [Effects of the Invention]

[0012] According to one aspect of the present invention, it is possible to realize a marker for MRI imaging that can be used as an index of a position in an MRI image. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 shows a marker according to one embodiment of the present invention. [Figure 2] FIG. 10 shows MRI images captured with different concentrations of MRI contrast agent. [Figure 3] FIG. 3 is a line graph showing the results of FIG. 2. [Figure 4] FIG. 2 is a diagram showing the state in which the marker shown in FIG. 1 is placed on the surface of the liver. [Figure 5] 2A and 2B are MRI images of the liver in which the markers shown in FIG. 1 are placed, showing horizontal and coronal sections. [Figure 6] 1A and 1B are MRI images of the liver after resection of a small lesion, showing axial and coronal sections. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications are possible within the scope of the claims. Furthermore, embodiments and examples obtained by appropriately combining the technical means disclosed in different embodiments and examples are also included in the technical scope of the present invention. All academic literature and patent documents described in this specification are incorporated herein by reference.

[0015] 1. Overview of the Invention One embodiment of the present invention provides a marker for MRI imaging, which serves as an index for identifying the location of a lesion in an MRI image. Note that the term "MRI image" refers to an image obtained by performing imaging using MRI.

[0016] Conventionally, in procedures such as surgery targeting small lesions inside the body, methods for determining the location of the target have been used, such as (1) relying on anatomical landmarks or (2) using ultrasound diagnostics, which enable real-time image diagnosis. For example, in the case of liver tumors, contrast agents for ultrasound diagnostics have been developed, and due to their usefulness, the use of ultrasound diagnostics during surgery is becoming increasingly important.

[0017] On the other hand, with the recent remarkable advances in diagnostic imaging technology, there are an increasing number of situations where small lesions that can only be detected by highly sensitive diagnostic imaging methods such as CT or MRI must be treated. For example, the detection sensitivity of MRI for small liver tumors is extremely high, exceeding that of ultrasound.

[0018] However, no definitive solution has yet been found to the problem of how to identify the location of such small lesions during surgery and how to treat them, including by excision.While it is clear that early detection and treatment through diagnostic imaging is desirable, the current situation is one in which clinical diagnostic technology is not keeping up with this demand, creating a dilemma.

[0019] Unlike ultrasound diagnostics, CT or MRI are difficult to diagnose in real time, so when performing surgery or other procedures on lesions detected by these methods, the surgeon must accurately determine the location of the lesion. For example, for lesions in organs whose position relative to the skeleton is unlikely to change, such as brain tumors or spinal cord tumors, the location of the lesion can be identified using an intraoperative navigation system, relying on the positional relationship between the skeleton and the lesion in preoperative CT or MRI images.

[0020] However, in the case of organs whose position relative to the skeleton is easily changed, such as the lungs or liver, it is difficult to maintain the positional relationship of the organ relative to the skeleton between preoperative evaluation and lesion resection, making it difficult to use such intraoperative navigation systems. Furthermore, when using CT, there is a method using microcoils or the like as position markers, as shown in Non-Patent Document 1, but as mentioned above, this method cannot be used for lesions that are difficult to detect without MRI.

[0021] For small lesions, such as early-stage liver tumors, which are difficult to detect without MRI, marking their location before or during surgery and enabling accurate resection of small lesions could lead to early detection and treatment. It is also expected to lead to improved outcomes of cancer treatment for patients. As a result, one embodiment of the present invention can contribute to achieving Goal 3 of the Sustainable Development Goals (SDGs), including "Good Health and Well-Being."

[0022] The present inventors have completed the present invention after extensive research based on a novel idea that an MRI imaging agent, which has conventionally been used by administering it to a living body, can be used as an MRI imaging marker in a manner different from administration to a living body. One embodiment of the present invention will now be described.

[0023] In this specification, the term "living body" may refer to a human body, a mammalian body other than a human, or an animal body other than a mammalian body.

[0024] [2. Marker] 1, a marker 1 (MRI imaging marker) according to one embodiment of the present invention includes a non-magnetic container and an MRI imaging agent contained in the container. In this embodiment, the container included in the marker 1 is composed of a plurality of tubes 2 (cylindrical portions), and an MRI imaging agent is enclosed in the cavity of each tube 2.

[0025] In this embodiment, the tubes 2 are Nelaton catheters made of polyvinyl chloride, and each tube 2 is approximately 10 cm long and has an outer diameter of 10 Fr (approximately 3.3 mm). Twelve such tubes 2 are arranged in a grid pattern in the marker 1. The tubes 2 are arranged in a plane, six in the vertical direction and six in the horizontal direction, with 2 cm intervals between each, forming a flat grid shape.

[0026] Each tube 2 is supported by a support 3 made of a non-magnetic synthetic resin sheet, and their relative positions are fixed. The support 3 is a roughly square sheet with lengths of approximately 11 cm in the vertical and horizontal directions as viewed in FIG.

[0027] By providing the marker 1 with such a support 3, it becomes easy to arrange multiple tubes 2 to form a complex shape such as a lattice. In addition, the strength of the marker 1 is improved, making it easier to handle, and it also becomes easier to attach and detach from an MRI imaging target such as an organ. Note that the support 3 is not essential for the marker 1.

[0028] Marker 1 has contrast region 10 containing an MRI contrast agent and other non-contrast region 11 not containing an MRI contrast agent. Specifically, in marker 1, the region where tube 2 containing MRI contrast agent is placed is contrast region 10, and the other region is non-contrast region 11. In an MRI image of marker 1 captured by MRI, contrast region 10 is a region where a signal is detected (enhanced), and non-contrast region 11 is a region where no signal is detected (not enhanced).

[0029] Marker 1 is formed by arranging multiple tubes 2 in a lattice pattern. Therefore, contrast region 10 of marker 1 is also formed as a lattice pattern. In this way, the shape of contrast region 10 is the same as the shape of the container containing the MRI contrast agent.

[0030] The MRI contrast agent does not have to completely fill the lumen of the tube 2. When the MRI contrast agent is enclosed in a portion of the tube 2, the contrasted region 10 is the region of the tube 2 that contains the MRI contrast agent, and the other portion of the tube 2 is the non-contrast region 11.

[0031] In the marker 1, a non-contrast region 11 is formed between at least two tubes 2. In other words, in the marker 1, at least two contrast regions 10 are formed at positions sandwiching at least one non-contrast region 11. An example of a non-contrast region 11 in the marker 1 is a region surrounded by two tubes 2a and 2b extending in the vertical direction and two tubes 2c and 2d extending in the horizontal direction in Figure 1. The non-contrast region 11 can be said to be a region sandwiched between the contrast regions 10 formed by the two tubes 2a and 2b, and also a region sandwiched between the contrast regions 10 formed by the two tubes 2c and 2d.

[0032] In the marker 1, the non-contrast regions 11 are formed as a total of 25 regions in a 5-row, 5-column arrangement, partitioned by the tubes 2 arranged in a grid pattern. In addition, parts of the support 3 that are outside the outermost tubes 2 in the vertical and horizontal directions in plan view also form the non-contrast regions 11. In this way, at least some of the non-contrast regions 11 of the marker 1 may be regions that are not sandwiched between the contrast regions 10.

[0033] The MRI contrast agent included in the marker 1 is not particularly limited as long as it is a substance that can detect a signal (be contrasted) in an MRI image, but is preferably a substance that can detect a signal that is stronger than that of water. Marker 1 contains meglumine gadoterate (Magnescope; registered trademark) as an MRI contrast agent, but is not limited to this. Examples of MRI contrast agents include gadolinium preparations such as sodium gadoxetate (Primovist; registered trademark), ammonium ferric citrate (Ferriselts; registered trademark), and manganese chloride tetrahydrate (Bosdel; registered trademark), which are approved for administration to living bodies via intravenous injection, oral administration, etc.

[0034] Furthermore, because marker 1 contains an MRI contrast agent enclosed in tube 2, the MRI contrast agent itself does not normally have any effect when it comes into contact with a living body. Therefore, even a substance that has not been approved for administration to a living body can be used as the MRI contrast agent contained in marker 1. However, considering the risk of damage to tube 2 due to surgical instruments, etc., it is preferable that the MRI contrast agent contained in marker 1 is an MRI contrast agent that is approved for administration to a living body and whose safety has been confirmed.

[0035] The MRI contrast agent provided in marker 1 is not administered to a living body as in the past, but is placed in a tube 2 on a subject for MRI imaging for MRI imaging. Therefore, when using an MRI contrast agent that is approved for administration to a living body, it may be preferable that the concentration of the MRI contrast agent provided in marker 1 be different from that for administration to a living body.

[0036] The concentration of the MRI contrast agent is preferably 1 / 10 or less of the concentration when administered to a living body, more preferably 1 / 20 or less, more preferably 1 / 40 or less, and particularly preferably 1 / 100 or less. Furthermore, the concentration of the MRI contrast agent is preferably 1 / 10,000 or more of the concentration when administered to a living body, more preferably 1 / 1,000 or more, more preferably 1 / 500 or more, and particularly preferably 1 / 200 or more. At such a concentration, the contrast region 10 of the marker 1 can be confirmed in an MRI image.

[0037] When adjusting the concentration by diluting the MRI contrast agent, the diluent is not particularly limited as long as it is a non-magnetic liquid that produces a signal intensity in an MRI image lower than that of the MRI contrast agent contained in the marker 1. Considering the risk of damage to the tube 2 by surgical instruments, etc., it is preferable that the diluent for the MRI contrast agent be a liquid that is acceptable for administration to a living body. Examples of such liquids include water, alcohols, organic solvents, and mixed solutions thereof, and these liquids may contain salts such as sodium chloride. From the standpoints of availability and safety, physiological saline is preferred as the diluent.

[0038] In this way, by using the marker 1 equipped with an MRI imaging agent, the position of the lesion can be more accurately identified by comparing the position of the marker 1 with the position of the lesion identified by the MRI image, compared to when the position of the skeleton or the like is used as an index. For example, if the marker 1 is placed on an organ such as the liver before surgery and an MRI image is taken, the positional relationship between the marker 1 and the organ is unlikely to change even if the organ moves thereafter. Therefore, the position of the lesion can be identified using the marker 1 as an index, and treatment such as surgery can be easily performed on the lesion. For small lesions, accurate identification of the position is particularly important, so the usefulness of such a marker 1 is even greater.

[0039] The marker 1 also has a grid-like contrast region 10 formed by a plurality of tubes 2 and a non-contrast region 11 sandwiched between these tubes 2. Therefore, by placing the marker 1 so as to cover an area where a lesion is thought to exist in an organ or the like being subjected to MRI imaging, it is easy to identify the position in the grid-like contrast region 10 near which the lesion exists. Therefore, by using the marker 1, the position of the lesion in an organ or the like being subjected to MRI imaging can be identified with great accuracy.

[0040] Furthermore, the tube 2 is made of polyvinyl chloride and is flexible, so the marker 1 can flex flexibly to match the surface shape of the organ or the like, and can assume a three-dimensional shape that conforms well to the surface of the organ or the like.

[0041] MRI imaging typically produces multiple cross-sectional MRI images, such as horizontal, coronal, and sagittal slices, taken from different directions relative to the body's longitudinal axis. If the marker 1 has a three-dimensional shape, the contrast-enhanced region 10 can be easily detected in the MRI images taken from any direction. Therefore, the marker 1 makes it easy to accurately identify the location of a lesion not only in two-dimensional imaging subjects but also in three-dimensional imaging subjects such as organs.

[0042] In MRI imaging, the horizontal section refers to a section in which the top and bottom of the MRI image correspond to the ventrodorsal direction of the body and the left and right correspond to the left and right direction of the body. The coronal section refers to a section in which the top and bottom of the MRI image correspond to the craniocaudal direction of the body and the left and right correspond to the left and right direction of the body. The sagittal section refers to a section in which the top and bottom of the MRI image correspond to the craniocaudal direction of the body and the left and right correspond to the ventrodorsal direction of the body.

[0043] (Variation) The configuration of the marker 1 is not limited to the above and can be modified in various ways. For example, in the marker 1, the multiple tubes 2 do not have to be arranged in a grid pattern, but may be arranged in a so-called fence pattern, aligned in only one direction. Furthermore, the spacing between the multiple tubes 2 does not need to be constant.

[0044] Furthermore, the container provided with the marker 1 may be a single bent tube 2 rather than multiple tubes 2. In this case, the single tube 2 can be considered to be divided into multiple cylindrical portions at any position, such as a bent or curved portion, as a boundary. For example, in the single tube 2, the region sandwiched between two opposing cylindrical portions (two contrast regions 10) divided by the bent portion can be defined as a non-contrast region 11.

[0045] Furthermore, the container included in marker 1 may have only a partial cylindrical portion such as tube 2, or may not have any cylindrical portion at all. An example of a container without a cylindrical portion is a shape in which multiple small spherical (dot-shaped) containers are arranged regularly or irregularly on sheet-like support 3. In this case, marker 1 can be said to have multiple dot-shaped contrast regions 10 and non-contrast regions 11 sandwiched between these contrast regions 10.

[0046] When the marker 1 has a container of this shape, it is easy to identify in the MRI image which of the multiple dot-shaped contrast regions 10 formed on the marker 1 has a lesion located near it.

[0047] The material of the container included in the marker 1 is not particularly limited as long as it is non-magnetic, but is preferably made of resin, and more preferably made of synthetic resin. Examples of synthetic resins include polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate, polyamide, and polystyrene. Biomass-derived polymer materials such as polylactic acid are also examples of synthetic resins. "Made of synthetic resin" means that the main material of the container is such a synthetic resin, and it may also contain a material other than synthetic resin. Furthermore, if the container included in the marker 1 is made of a non-magnetic material other than synthetic resin, it may be made of a non-magnetic metal material such as titanium.

[0048] If the container of the marker 1 is made of such a material, it will be less susceptible to the magnetic field generated by MRI, and therefore MRI imaging can be performed safely with the marker 1 placed on the subject.

[0049] The material of the container included in the marker 1 is preferably flexible, but is not limited to this. For example, the container included in the marker 1 may be formed in a three-dimensional shape rather than a flat shape, even if it is not flexible. In other words, the marker 1 may include a container having a three-dimensional shape that matches the shape of the MRI imaging subject. With this configuration, even if the container included in the marker 1 is not flexible, the marker 1 can be well placed so as to conform to the surface shape of the MRI imaging subject.

[0050] The material of the support 3 included in the marker 1 may be a non-magnetic material, preferably a synthetic resin, similar to the container included in the marker 1. Furthermore, the support 3 does not need to be sheet-shaped, and may be, for example, a tape-like or thread-like member that fastens the plurality of tubes 2 together.

[0051] [3. How to use the marker] A method for diagnosing a lesion using Marker 1 and a method for surgically treating a lesion using Marker 1 are also included within the scope of the present invention.

[0052] Specifically, a method for diagnosing a lesion according to one embodiment of the present invention includes the steps of placing an MRI imaging marker, which includes a non-magnetic container and an MRI contrast agent contained in the container, on an MRI imaging target that may contain a lesion; acquiring an MRI image of the MRI imaging target with the MRI imaging marker placed thereon; and identifying the position of the lesion in the imaging target from the MRI image based on the position of the MRI imaging marker and the position of the lesion.

[0053] Furthermore, a method for surgically treating a lesion according to one embodiment of the present invention includes the steps of placing an MRI imaging marker, which includes a non-magnetic container and an MRI contrast agent contained in the container, on an MRI imaging target that may contain a lesion; acquiring an MRI image of the MRI imaging target with the MRI imaging marker placed thereon; and marking the position of the lesion on the imaging target, which is identified based on the position of the MRI imaging marker and the position of the lesion in the MRI image.

[0054] The above description of [2. Markers] can be used as appropriate for the MRI imaging marker (marker 1) and the method for identifying the position of the lesion based on the position of the MRI imaging marker and the position of the lesion. Furthermore, conventionally known methods can be used for acquiring MRI images.

[0055] The subject of MRI imaging is not particularly limited, but examples thereof include organs in a living body. Organs whose positions relative to the skeleton tend to fluctuate are particularly suitable for diagnostic or surgical methods using marker 1. This is because the positional relationship between the skeleton and the organ tends to fluctuate, making it difficult to identify the location of a lesion based on the MRI image after MRI imaging. Examples of organs whose positions relative to the skeleton tend to fluctuate include organs in the thoracic or abdominal cavity, such as the heart, lungs, stomach, duodenum, liver, pancreas, kidneys, gallbladder, spleen, small intestine, large intestine, uterus, and prostate.

[0056] The method for placing the marker 1 on the MRI imaging subject is not particularly limited, but for example, the marker 1 may be simply placed on the MRI imaging subject, or the marker 1 may be simply fixed to the MRI imaging subject using a fixing device such as a non-magnetic needle or thread. The fixing device may be included in the marker 1 or may be independent of the marker 1.

[0057] The method for marking the position of a lesion in an MRI imaging subject is not particularly limited, but examples include a method of burning the lesion or its surroundings with an electric scalpel or the like. [Example]

[0058] An embodiment of the present invention will now be described.

[0059] [A. MRI contrast agent concentration considerations] The optimal concentration of MRI contrast agent to be encapsulated in Marker 1 was investigated. A 38% aqueous solution of meglumine gadoterate (Magnescope Intravenous 38% Syringe, Guerbet Japan Co., Ltd.) was used as the MRI contrast agent. Figure 2 shows bright-field and MRI images of samples of the MRI contrast agent serially diluted with saline. MRI imaging was performed using an intraoperative MRI system (Fujifilm Healthcare Systems Co., Ltd., LUCENT-J). The magnetic field strength of the intraoperative MRI system was 0.4 T (tesla).

[0060] As shown in Figure 2, the samples used were Sample A, which was saline (not containing an MRI contrast agent), and Samples B to G, which were MRI contrast agents diluted stepwise with saline. The dilution ratios (concentration ratios relative to the stock solution) of the MRI contrast agent in Samples B to G were B: 5x (1 / 5), C: 10x (1 / 10), D: 20x (1 / 20), E: 40x (1 / 40), F: 100x (1 / 100), and G: 200x (1 / 200), respectively.

[0061] The signal intensity of each sample in the obtained MRI images is shown as a line graph in Figure 3. The signal intensity in the MRI images was quantified by creating a T1 relaxation curve using inversion recovery and calculating the T1 value.

[0062] As shown in Figure 3, the signal intensity was strongest when the MRI contrast agent was diluted 100 times (1 / 100th the concentration of the stock solution). Furthermore, the MRI images in Figure 2 show that when the MRI contrast agent was diluted 20 times or more (1 / 20th the concentration of the stock solution or less), the signal intensity was stronger than that of saline. In all of the surgical examples using Marker 1 shown below, the MRI contrast agent was prepared at the dilution concentration with the highest signal intensity (100 times the dilution, 1 / 100th the stock solution) and enclosed in Marker 1.

[0063] [B. Example of surgery using markers] Hepatocellular carcinoma resection surgery was performed under MRI guidance using Marker 1 shown in Figure 1. This surgery was conducted as an epidemiological study on MRI-guided liver resection, and was approved by the Hiroshima University Epidemiological Research Ethics Committee (Permission Number: E-1600, Approval Date: May 10, 2019).

[0064] 4 is a diagram showing the state in which the marker 1 was placed on the liver L in a case of hepatocellular carcinoma resection surgery using the marker 1. Specifically, after laparotomy under general anesthesia, the marker 1 was placed on the surface of the liver L so as to cover the approximate area where the hepatocellular carcinoma was present, and MRI imaging was performed.

[0065] Figure 5 shows axial and coronal MRI images obtained by MRI imaging. In Figure 5, the hepatocellular carcinoma lesion is indicated by an arrow, and the position where marker 1 is enhanced is indicated by an arrowhead. As such, marker 1 has multiple enhanced regions 10 sandwiched between non-enhanced regions 11, making it easy to confirm the position of marker 1 even in MRI images showing three-dimensional cross sections of organs.

[0066] The surgeon used MRI images to identify the location of the lesion by comparing the position of Marker 1 with that of the lesion, and then marked the lesion with an electric scalpel. Marker 1 was then removed from the surface of liver L, and a resection margin of approximately 2 cm was left around the lesion, and the lesion was resected.

[0067] Figure 6 shows axial and coronal MRI images obtained by performing MRI again after resection. In Figure 6, the location of the hepatocellular carcinoma lesion in liver L is indicated by an arrow. As shown in Figure 6, it was confirmed that the hepatocellular carcinoma had been completely removed by appropriately resecting a portion of liver L centered on the lesion. After confirming the completion of the resection using MRI images, the abdomen was closed and the surgery was completed.

[0068] Table 1 below shows the results of 12 MRI-guided resection surgeries for hepatocellular carcinoma performed using Marker 1. Table 2 below shows the results of three MRI-guided resection surgeries for hepatocellular carcinoma or metastatic liver tumors performed without Marker 1, before the invention of Marker 1. These surgeries were performed between July 2019 and October 2021.

[0069] By using Marker 1, the surgeon has the advantage of being able to accurately identify and resect the lesion, and there was no notable increase in surgical time or blood loss compared to conventional methods. In other words, Marker 1 does not pose any major disadvantages to surgery compared to conventional methods, and it has been shown that good surgical results can be obtained even in difficult cases where it is difficult to identify the location of the lesion.

[0070] [Table 1]

[0071] [Table 2] [Industrial Applicability]

[0072] The present invention can be used, for example, for MRI imaging during surgery. [Explanation of symbols]

[0073] 1 marker (MRI imaging marker) 2 Tube (container, cylindrical part) 3 Support 10 Contrast area 11 Non-contrast area L liver

Claims

1. The device comprises a non-magnetic container and an MRI contrast agent contained in the container, a contrast region containing the MRI contrast agent and a non-contrast region not containing the MRI contrast agent; At least two contrast regions are formed at positions sandwiching at least one non-contrast region, In the contrast region, four or more cylindrical portions of the container containing the MRI contrast agent are arranged to form a lattice, the non-contrast region is a region surrounded by the lattice formed by the cylindrical portion, the MRI contrast agent is one or more selected from the group consisting of gadolinium preparations, ferric ammonium citrate, and manganese chloride tetrahydrate; The MRI imaging marker, wherein the concentration of the MRI contrast agent is 1 / 200 or more and 1 / 20 or less of the concentration when administered to a living body.

2. The MRI imaging marker according to claim 1 , wherein the container is made of a flexible resin.

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