Hydrosol, ultrasound phantom using the hydrosol, ultrasound phantom set, and method of manufacturing ultrasound phantom

Abstract

To provide a highly viscous hydrosol having a sound velocity close to that of a living body.SOLUTION: A hydrosol provided herein is used in ultrasound phantoms and comprises water, cellulose ether, and a sound velocity modifier.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a hydrosol, an ultrasound phantom using the hydrosol, an ultrasound phantom set, and a method for manufacturing an ultrasound phantom. [Background technology]

[0002] Medical imaging diagnostic equipment such as acoustic wave diagnostic equipment, magnetic resonance imaging diagnostic equipment, X-ray imaging diagnostic equipment, and near-infrared imaging equipment performs diagnosis by irradiating sound waves, electromagnetic waves, etc. onto the area to be observed and observing the reflected and transmitted sound waves or electromagnetic waves. Biological tissue simulating materials (hereinafter referred to as "phantoms") that mimic the reflection and absorption characteristics of sound waves, electromagnetic waves, etc. in living tissue are used to calibrate the above-mentioned imaging diagnostic equipment and to expand the measurement range.

[0003] Ultrasound diagnostic equipment is a device that observes the reflected waves of ultrasound irradiated onto the observation site and visualizes the internal state. In recent years, various analytical applications have been developed and installed, such as the shear wave elastography method, which can quantify Young's modulus by measuring the propagation velocity distribution of shear waves generated by vibrating the observation site, and the shear wave dispersion method, which can quantify viscosity by measuring the frequency dependence of the propagation velocity of the generated shear waves.

[0004] By combining multiple measurement methods, it has become possible to evaluate the progression of pathology that would be difficult to distinguish using a single evaluation method. For example, a method combining the aforementioned shear wave elastography method and shear wave dispersion method has been proposed as a new approach to understanding liver pathology.

[0005] On the other hand, in order to perform accurate evaluation using an ultrasound diagnostic device, it is necessary to calibrate the device using an ultrasound phantom with known Young's modulus, viscosity, etc. Patent Document 1 discloses a method for creating a phantom with controlled viscosity, in which glycerin, a viscous liquid, is added to the phantom. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6754112 Summary of the Invention [Problem to be solved by the invention]

[0007] In general, hydrogels, which are primarily composed of water, are particularly suitable as phantoms for ultrasound diagnostic devices, i.e., ultrasound phantoms, because the sound velocity of longitudinal waves is close to that of living tissue and acoustic attenuation is small.When using hydrogels as ultrasound phantoms, it is common to add a substance that adjusts the sound velocity of longitudinal waves to bring the sound velocity of longitudinal waves closer to that of living tissue.

[0008] On the other hand, when a substance is added to adjust the physical properties of the hydrogel other than the longitudinal wave sound velocity, an unintended change in the longitudinal wave sound velocity occurs. For example, the hydrogel disclosed in Patent Document 1 has a large amount of glycerin added to it in order to improve its viscosity, which achieves an improvement in the viscosity of the hydrogel. However, when used as an ultrasound phantom, there is a problem in that the longitudinal wave sound velocity is far different from that of a living body.

[0009] Therefore, an object of the present invention is to provide a hydrosol having a high viscosity and a sound speed close to that in a living body. Another object of the present invention is to provide an ultrasound phantom using a hydrosol having a high viscosity and a sound speed close to that in a living body. Another object of the present invention is to provide an ultrasound phantom set using a hydrosol having a high viscosity and a sound speed close to that in a living body. Another object of the present invention is to provide a method for manufacturing an ultrasound phantom using a hydrosol having a high viscosity and a sound speed close to that in a living body. [Means for solving the problem]

[0010] The present invention relates to a hydrosol applied to an ultrasound phantom, It is a hydrosol containing water, cellulose ether, and a sound speed adjusting agent. The present invention also provides The above hydrosol, a container for containing the hydrosol, the container having a holding part that comes into contact with the hydrosol and maintains the shape of the hydrosol; This is an ultrasound phantom having the following structure. The present invention also provides The above ultrasound phantom and a second ultrasound phantom comprising a second cellulose ether exhibiting an average molecular weight different from the average molecular weight of the cellulose ether contained in the ultrasound phantom, water, a sound speed adjusting agent, and a second container containing the second cellulose ether, the water, and the sound speed adjusting agent; This is an ultrasound phantom set including: The present invention also provides A preparation step of preparing a mixed solution by mixing water, cellulose ether, and a sound speed adjusting agent; A stirring step of stirring and mixing the mixed liquid to prepare a hydrosol; pouring the hydrosol into a container; A method for manufacturing an ultrasound phantom, comprising: [Effects of the Invention]

[0011] The present invention provides a hydrosol that can be used in an ultrasound phantom with controllable viscosity (high viscosity) and a sound speed similar to that of a living body, an ultrasound phantom using the hydrosol, and a method for manufacturing the same. Furthermore, the ultrasound phantom and ultrasound phantom set of the present invention can be used for calibrating an ultrasound diagnostic device. DETAILED DESCRIPTION OF THE INVENTION

[0012] In the present invention, unless otherwise specified, the expression "XX or more and YY or less" or "XX to YY" representing a numerical range means a numerical range including the lower and upper limits, which are the endpoints. When a numerical range is described in stages, the upper and lower limits of each numerical range can be combined arbitrarily.

[0013] [First embodiment] The first embodiment is for a hydrosol. The hydrosol of this embodiment is A hydrosol applied to an ultrasound phantom, comprising: It contains water, a cellulose ether, and a sound speed adjusting agent. The hydrosol applied to the ultrasound phantom according to this embodiment, and the materials and configuration contained in the ultrasound phantom using this hydrosol will be described below.

[0014] <Hydrosol explanation> The hydrosol of this embodiment is a hydrosol that is applied to an ultrasound phantom. The hydrosol of this embodiment is a fluid sol that contains water as its main component, and is a sol that contains water and a sound speed adjusting agent (described later), and in which at least a portion of a cellulose ether (described later) is dissolved in water. If necessary, the hydrosol can be mixed with other components (described later) and placed in a container (described later) to be used as an ultrasound phantom.

[0015] <Explanation of water> The hydrosol of this embodiment contains water. The water used in this embodiment may be tap water, well water, pure water, ultrapure water, or the like. Purified water is preferred from the viewpoint of suppressing variations in physical properties due to impurities. Examples of methods for purifying water include distillation, methods using reverse osmosis membranes, ion exchange membranes, and sterilization with UV lamps, and combinations of these methods.

[0016] In the hydrosol, at least a portion of the water is preferably hydrated with the cellulose ether described below. The water content in the hydrosol is, for example, preferably 50.00% by mass or more and 99.00% by mass or less, more preferably 70.00% by mass or more and 99.00% by mass or less, even more preferably 80.00% by mass or more and 99.00% by mass or less, and still more preferably 84.00% by mass or more and 94.00% by mass or less.

[0017] <Explanation of cellulose ether> The hydrosol of this embodiment contains a cellulose ether, which has a polysaccharide skeleton in which many glucose units, a monosaccharide, are linked in a linear chain, and in which some of the hydroxyl groups of the glucose are substituted with alkoxy groups.

[0018] The bond connecting glucose units is preferably a glycosidic bond from the viewpoint of availability. Furthermore, the D-form of glucose is preferred from the viewpoint of availability, but it may also be an L-form or a mixture. Furthermore, some hydroxy groups bonded to the anomeric carbon may be in the cis form (α-anomer). From the viewpoint of availability, cellulose with a basic skeleton consisting of 90% or more of β-D-glucose is preferred. Hereinafter, glucose after being bonded by glycosidic bonds will be referred to as glucose residues.

[0019] The alkoxy group substituting a portion of the hydroxy group of the glucose residue may be linear or branched, and may contain a hydroxy group. Furthermore, the hydroxy group of the alkoxy group containing a hydroxy group may be further substituted with an alkoxy group. Hereinafter, whether or not the hydroxy group of the glucose residue is substituted with an alkoxy group, it will be referred to as a glucose residue.

[0020] <Types of cellulose ethers and substituents> Examples of the cellulose ether suitable for use in this embodiment include carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose.

[0021] In the cellulose ether of the present embodiment, the hydroxyl groups derived from the glucose residue are preferably substituted with at least one selected from the group consisting of a methoxy group, a hydroxyethoxy group, and a hydroxypropoxy group. The alkoxy group substituting a portion of the hydroxyl groups of the glucose residue is preferably a methoxy group, an ethoxy group, a hydroxyethoxy group, a hydroxypropoxy group, or a carboxymethoxy group from the viewpoint of availability, and more preferably a methoxy group, a hydroxyethoxy group, or a hydroxypropoxy group from the viewpoint of water solubility suitable for producing a hydrosol.

[0022] The cellulose ether of this embodiment is preferably modified with an average of 0.4 to 2.4 methoxy groups, 0 to 0.6 hydroxyethoxy groups, and 0 to 0.5 hydroxypropoxy groups per glucose residue.

[0023] From the viewpoints of availability and water solubility suitable for producing a hydrosol, the average number of alkoxy groups contained in one glucose residue is preferably 0.4 to 2.4 methoxy groups, more preferably 0.9 to 1.9 hydroxyethoxy groups, preferably 0 to 0.6 hydroxyethoxy groups, more preferably 0 to 0.4 hydroxypropoxy groups, and preferably 0 to 0.5 hydroxypropoxy groups, more preferably 0.1 to 0.3 hydroxypropoxy groups.

[0024] In addition, when an alkoxy group containing a hydroxy group is introduced as a substituent on the glucose residue of a cellulose ether, the hydroxy group may also be replaced with an alkoxy group, and therefore, the number of alkoxy groups added may exceed the three hydroxy groups that the glucose residue originally has.

[0025] <Surface treatment of cellulose ether> The cellulose ether in this embodiment is preferably surface-treated with a hydrophobic substance in order to improve dispersibility in water. The hydrophobic substance used in the surface treatment is preferably a substance that undergoes a gradual decomposition reaction in water to become water-soluble, and glyoxal is preferred from the viewpoint of availability.

[0026] <Cellulose ether content> The hydrosol in this embodiment preferably has a cellulose ether purity of 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.The hydrosol in this embodiment preferably has a cellulose ether purity of 98% by mass or less.

[0027] The content of the cellulose ether is preferably 1.5 parts by mass or more, and in order to obtain a uniform hydrosol that ensures defoaming properties, it is preferably 1.5 to 5.0 parts by mass, more preferably 1.5 to 4.0 parts by mass, and even more preferably 2.0 to 4.0 parts by mass.

[0028] The hydrosol of this embodiment has a ratio (mass ratio) Cc / Cw of the cellulose ether content to the water content of 1.5 / 98 or more and 5 / 80 or less, i.e., 1.53 × 10 -2 Over 6.25 x 10 -2 The following is preferred:

[0029] <Mechanism of thickening of cellulose ether> The cellulose ether used in the hydrosol of this embodiment dissolves in water at room temperature (25°C) to form a hydrosol. In the hydrosol state, resistance occurs when a force is applied due to the entanglement of the polymer chains contained in the cellulose ether. The strength of the entanglement of the polymer chains can be adjusted by the amount and molecular weight of the cellulose ether. The molecular weight referred to here refers to the number average molecular weight or the mass average molecular weight.

[0030] For example, when a cellulose ether with a high molecular weight is used, the polymers are strongly entangled, which facilitates the formation of an intermolecular network, and even a small amount of addition enhances the elastic properties of the viscoelasticity.On the other hand, when a cellulose ester with a low molecular weight is used, the entanglement is weak, so even if a large amount is added, it is difficult to enhance the elastic properties.

[0031] Therefore, by changing the molecular weight and the amount of cellulose ether used, the elasticity and viscosity of the viscoelasticity can be controlled as desired. Due to the above-mentioned mechanism of thickening, the present invention can be suitably used to simulate the viscosity of organs in particular.

[0032] <Properties of cellulose ether containing methoxy groups> Among the cellulose ethers in the hydrosol of this embodiment, the hydrosol containing a cellulose ether containing a methoxy group is a hydrosol at room temperature, but undergoes a phase transition to a hydrogel upon heating, and this phase transition is reversible. This is thought to be because the interaction of the hydrophobic groups is strengthened by thermal motion as the temperature increases.

[0033] The phase transition temperature varies depending on the number of methoxy groups and the type of other alkoxy groups, but it has a phase transition point between 65°C and 90°C. Hydrosol and hydrogel can be distinguished by viscoelasticity measurements, which will be described later.

[0034] <Explanation of sound speed adjuster> The hydrosol of this embodiment contains a sound speed adjusting agent. The sound speed adjusting agent used in the hydrosol of this embodiment refers to a material that, when mixed with water, exhibits a longitudinal wave sound speed different from that of water alone.

[0035] The sonic velocity adjusting agent may be dissolved or dispersed in water, but is preferably dissolved in water from the viewpoint of ultrasonic transmittance. Furthermore, in order to prevent a change in the sonic velocity of longitudinal waves, it is preferable that the sonic velocity adjusting agent is not easily volatilized, and is preferably not decomposed in water or does not react with other components.

[0036] <Types of sound speed adjusters> Examples of the sound speed adjusting agent used in the hydrosol of this embodiment include inorganic compounds such as sodium bicarbonate, organic compounds such as urea, guanidine, guanidine salts, glucose, and inositol, alcohols such as ethanol, ethylene glycol, and glycerin, and organic solvents such as N,N-dimethyl sulfoxide and N,N-dimethylformamide.

[0037] <Amount of sound velocity adjuster added> The amount of the sound speed adjusting agent used in the hydrosol of this embodiment may be added in a range that does not deviate significantly from the speed of sound in the organs of a living body, which is about 1535 m / s.

[0038] For example, when ultrasound with a frequency of 3.5 MHz is passed through a hydrosol, the sound speed of the ultrasound is preferably 1500 m / s or more and 1600 m / s or less, more preferably 1520 m / s or more and 1550 m / s or less, and even more preferably 1530 m / s or more and 1540 m / s or less.

[0039] The amount of the sound velocity adjusting agent added is preferably 0.1 parts by mass or more relative to 100.0 parts by mass of water from the viewpoint of stabilizing the sound velocity of longitudinal waves, and is preferably 25 parts by mass or less from the viewpoint of solubility and dispersibility in water, more preferably 0.5 parts by mass or more and 20 parts by mass or less.

[0040] For example, in the case of urea, when the mass of water is 94.0 parts by mass, the amount of urea added is preferably 2.0 parts by mass or more and 10.0 parts by mass or less, more preferably 4.0 parts by mass or more and 8.0 parts by mass or less, and even more preferably 5.0 parts by mass or more and 7.0 parts by mass or less.

[0041] <Other ingredients> The hydrosol of this embodiment contains water, cellulose ether, and other components different from the sound speed adjusting agent, and various other components can be added as needed.

[0042] <Explanation of ultrasonic scattering agents> The hydrosol of this embodiment may further contain an ultrasound scattering agent as another component. In ultrasound diagnostic devices, images are captured and measured using signals from ultrasound scattered within the hydrosol that reach a detector. Therefore, adding an ultrasound scattering agent to the part to be measured makes it possible to capture images and measure the Young's modulus and viscosity.

[0043] The scattering efficiency of ultrasound is calculated by the acoustic impedance of the material (= density x sound speed). The scattering efficiency at a material interface increases as the difference in acoustic impedance between the materials at the interface increases.

[0044] <Types of ultrasonic scattering agents> The ultrasound scattering agent may be any substance having a large difference in acoustic impedance from water, the main component of the hydrosol, and may be any of a gas, liquid, or solid. Liquids and solids are preferred from the viewpoint of dispersion stability within the hydrosol, and solids are preferred from the viewpoints of particle size and mechanical stability.

[0045] Substances that can be used as ultrasound scattering agents include known substances such as inorganic particles, metals, metal oxides, carbon particles, and spherical polymers.Specifically, carbon crystal particles such as graphite and microdiamond particles, amorphous carbon particles such as carbon black, resin particles such as polyethylene particles, polyethylene hollow spheres, and polystyrene hollow spheres, oxide fine particles such as titanium oxide, alumina oxide, and silicon oxide, and metal fine particles such as tungsten, nickel, and molybdenum are preferred.Among these, carbon crystal particles are particularly preferred in view of their high acoustic impedance and dispersibility in water.

[0046] <Particle size of ultrasonic scattering agent> The particle size of the ultrasound scattering agent is determined according to the wavelength of the input ultrasound. When calculated from the wavelength of the ultrasound emitted from the probe of the ultrasound diagnostic device, the particle size of the ultrasound scattering agent is preferably 5 μm or more and 50 μm or less, and more preferably 5 μm or more and 25 μm or less.

[0047] However, particles with a particle size of 5 μm or more and high density generally have a high settling velocity, and the ultrasound scattering agent particles may separate as the cellulose ether mixture thickens. The settling velocity can be calculated using the following Stokes' equation:

[0048] V=g(ρ p -ρ f )d p 2 / 18η V: Sedimentation velocity (m / s), g: Gravitational acceleration (m / s 2 ), ρp: particle density (kg / m 3 ), ρ f : Fluid density (kg / m 3 ), d p : particle diameter (m), η: fluid viscosity (Pa s) Therefore, settling of ultrasound scattering agent particles can be prevented by reducing the particle size of the ultrasound scattering agent, reducing the difference in density between the ultrasound scattering agent and the fluid, or increasing the viscosity of the fluid.

[0049] <Amount of ultrasonic scattering agent added> The content of the ultrasonic scattering agent may be adjusted appropriately depending on the target scattering effect and is not particularly limited, but when the mass of water is 94.0 parts by mass, it is preferably 0.1 parts by mass or more and 30.0 parts by mass or less, more preferably 0.5 parts by mass or more and 20.0 parts by mass or less, and even more preferably 3.0 parts by mass or more and 10.0 parts by mass or less.

[0050] <Explanation of ultrasonic absorbers> The hydrosol of this embodiment may further contain an ultrasound absorber as an additional component. An ultrasound absorber is a material that acts to weaken the intensity of ultrasound as it passes through. By controlling the ultrasound transmittance in the hydrosol, it is possible to produce a hydrosol with ultrasound transmittance equivalent to that of a living body.

[0051] <Types of ultrasonic absorbers> The ultrasonic absorbing agent used in the hydrosol of this embodiment may be any agent having a high ultrasonic transmission loss, and may be any of a gas, liquid, or solid. Liquids and solids are preferred from the viewpoint of dispersion stability within the hydrosol, and solids are preferred from the viewpoint of particle size and mechanical stability. Examples of types of ultrasonic absorbers include urethane rubber, silicone rubber, butadiene rubber, acrylic rubber, nitrile rubber, styrene rubber, and latex.

[0052] <Particle size of ultrasonic absorber> It is preferable that the ultrasonic absorbing agent be uniformly dispersed in the hydrosol. If the particle size of the ultrasonic absorbing agent is too small, the cohesive force is strong and it is easy to aggregate, but if the particle size is too large, it is easy to cause sedimentation. Therefore, the particle size is preferably 0.1 μm or more and 50 μm or less, and more preferably 0.2 μm or more and 30 μm or less.

[0053] <Amount of ultrasonic absorber added> The content of the ultrasonic scattering agent may be adjusted appropriately depending on the target scattering effect and is not particularly limited, but when the mass of water is 94.0 parts by mass, it is preferably 0.1 parts by mass or more and 30.0 parts by mass or less, more preferably 0.5 parts by mass or more and 20.0 parts by mass or less, and even more preferably 3.0 parts by mass or more and 10.0 parts by mass or less.

[0054] <Explanation of preservatives> The hydrosol of the present embodiment may contain a preservative as another component. Since hydrosols are generally prone to the growth of bacteria and mold, it is preferable to use a preservative to suppress the effects of deterioration on the physical properties.

[0055] <Types of preservatives> The preservative that can be used is not particularly limited, but is preferably one that is water-soluble and has a wide antibacterial spectrum.Examples of the preservative, disinfectant or antibacterial agent as a compound that can suppress the growth of bacteria and mold include alkyldiaminoethylglycine hydrochloride, sodium benzoate, ethanol, benzalkonium chloride, benzethonium chloride, chlorhexidine gluconate, chlorobutanol, sorbic acid, potassium sorbate, sodium dehydroacetate, methyl parahydroxybenzoate, ethyl parahydroxybenzoate, propyl parahydroxybenzoate, butyl parahydroxybenzoate, oxyquinoline sulfate, phenethyl alcohol and benzyl alcohol.

[0056] Among these, parahydroxybenzoic acid esters are preferred because they are water-soluble, have a wide antibacterial spectrum, and are particularly preferred for their minimal effect on the human body. Furthermore, methyl parahydroxybenzoate is particularly preferred from the viewpoint of water solubility.

[0057] <Amount of preservatives added> Since the effectiveness of preservatives varies depending on the compound, it is preferable to add them appropriately. For example, in the case of methyl parahydroxybenzoate, if the mass of water is 94.0 parts by mass, it is sufficient to add 0.1 parts by mass to 0.3 parts by mass, and addition within this range will be sufficient to achieve a sufficient effect as a preservative.

[0058] <Explanation of antifoaming agent> The hydrosol of this embodiment may contain an antifoaming agent as another component. If air bubbles are introduced during the preparation of the hydrosol, the ultrasonic waves will be excessively scattered due to the difference in acoustic impedance between the water and air interfaces, so it is preferable to use an antifoaming agent.

[0059] <Types of antifoaming agents> Examples of usable defoaming agents include oils such as mineral oil and fats, surfactants such as fatty acids, fatty acid esters, phosphate esters, and metal soaps, and silicone compounds such as silicone oil and dimethylsiloxane. Of these, silicone compounds are particularly preferred because they have a high defoaming effect even when added in small amounts.

[0060] <Amount of antifoaming agent added> The effects of defoaming agents vary depending on the compound, so it is preferable to add them appropriately. For example, in the case of a silicone compound, if the mass of water is 94,000 parts by mass, it is sufficient to add 0.001 part by mass or more and 0.100 part by mass or less, and the effect as a defoaming agent will be sufficient if the amount added is within this range.

[0061] <Explanation of thickener> The hydrosol of this embodiment may contain a thickener as another component. The addition of a thickener can improve the dispersion stability of the ultrasound scattering agent and ultrasound absorbing agent in the hydrosol.

[0062] Usable thickeners include synthetic polymers such as sodium polyacrylate and polyvinyl alcohol, polysaccharides such as tamarind seed gum, guar gum, succinoglycan, diutan gum and derivatives thereof, and cellulose derivatives. On the other hand, preferred thickeners are those that do not inhibit the dissolution and thickening of the cellulose ether when added.

[0063] <Gelling agent> The hydrosol of this embodiment may contain a gelling agent as another component. The addition of a gelling agent allows for fine adjustment of the Young's modulus of the hydrosol. Examples of gelling agents that can be used include polysaccharides such as agar, carrageenan, pectin, gellan gum, sodium alginate, tamarind seed gum, and curdlan, and gelatin.

[0064] <Other ingredients> The hydrosol of this embodiment may contain, as other components, a coloring agent such as an aqueous dye, a pH adjuster such as a phosphate buffer solution, and the like.

[0065] <Materials with multiple functions> The hydrosol of this embodiment contains water, cellulose ether, a sonic speed adjuster, and other components as necessary, but may exhibit multiple functions depending on the type and amount of materials used. In such cases, even if the function is different from the intended purpose, it is considered that a material has been added.

[0066] For example, graphite has a high ultrasonic scattering efficiency and therefore functions primarily as an ultrasonic scattering agent, but because some ultrasonic waves pass through it, it also functions as a sound speed adjuster and ultrasonic absorber. In this case, even if the purpose is not to adjust the sound speed or ultrasonic transmittance, it is considered that a sound speed adjuster or ultrasonic absorber has been added.

[0067] <Hydrosol ingredients> The hydrosol according to this embodiment preferably contains water, cellulose ether, a sound speed adjuster, and other components such as an ultrasound scattering agent, a preservative, and an antifoaming agent. The total mass of these components is preferably 80 to 100 parts by mass, more preferably 90 to 100 parts by mass, and even more preferably 95 to 100 parts by mass, based on 100 parts by mass of the entire hydrosol. The above-mentioned amounts of components can fully exhibit the functions of this embodiment.

[0068] <Hydrosol viscosity> The hydrosol of this embodiment has a storage modulus G' at a frequency of 2.5 Hz in dynamic shear viscoelasticity measurement at 25°C. 2.5 The storage modulus at a frequency of 0.25 Hz is G' 0.25 Then, G' 2.5 / G' 0.25 is preferably 2.0 or more and 15 or less, and more preferably 2.0 or more and 10 or less. By doing so, the hydrosol of this embodiment can obtain high viscosity and appropriate elasticity.

[0069] <Hydrosol analysis method> The viscoelasticity of the hydrosol according to this embodiment can be evaluated using a shear-type dynamic viscoelasticity measuring device, such as the MCR302 available from Anton Paar Japan.

[0070] In terms of measurement error, the measurement conditions for shear dynamic viscoelasticity measurement should be a measurement strain of 0.01% or more and 1.00% or less. If the strain is less than 0.01%, the response stress from the hydrosol will be small, making the measurements unreliable. Also, if the strain is greater than 1.00%, the internal structure may be destroyed due to deformation of the hydrosol, reducing the reliability of the measurements.

[0071] In addition, taking into consideration the tracking ability of the hydrosol and the measurement jig, it is desirable that the measurement frequency be 0.01 Hz or more and 10.0 Hz or less. If measurement values ​​on the high-frequency side exceeding 10.0 Hz are required, the high-frequency side data can be predicted using the temperature-time conversion rule.

[0072] Specifically, dynamic viscoelasticity measurements are performed at multiple temperatures while changing the frequency, and a composite curve (master curve) is obtained by horizontally shifting the data obtained for each temperature. The amount of horizontal shift can be determined by approximating the WLF law or Arrhenius law.

[0073] <How to distinguish between hydrosol and hydrogel> The aforementioned hydrosol and hydrogel states can be determined using the shear-type dynamic viscoelasticity measuring device. Specifically, if the value of tan δ, which is the ratio of the loss modulus G'' to the storage modulus G', is 1 or greater, the material is a hydrosol, and if it is less than 1, the material is a hydrogel.

[0074] <Viscosity index> When a viscoelastic material conforms to the Voigt model, the greater the viscosity, the greater the storage modulus (G') as the measurement frequency increases. In other words, the rate of increase in the storage modulus G' between specific frequencies can be used as an index of viscosity.

[0075] This property was utilized to evaluate the viscosity of the hydrosol according to this embodiment. Specifically, the storage modulus G' at a frequency of 2.5 Hz was 2.5 , the storage modulus at a frequency of 0.25 Hz is G' 0.25 Then, the ratio of them is G' 2.5 / G' 0.25 The value of was used as an index of viscosity. The viscoelasticity measurement was performed under the conditions of a strain of 0.1%, a measuring jig with a diameter of 25 mm parallel plates, and a sample thickness of 0.4 mm.

[0076] <Measurement of steady flow viscosity> The viscosity index G' of the hydrosol in this embodiment 2.5 / G' 0.25 can be obtained indirectly by measuring the steady flow viscosity. The steady flow viscosity can be measured using an E-type viscometer or the like. The measuring jig of the viscometer may be a parallel plate or a cone plate. The measurement conditions are 0.1 to 1000.0 sec -1 The following shear rate is desirable:

[0077] Steady flow viscosity is the viscosity when shear force is applied in the same direction, and is therefore essentially different from dynamic shear viscoelasticity measurement, which applies a periodic force. Therefore, the direct viscosity index G' 2.5 / G' 0.25 You cannot ask for this.

[0078] However, for the hydrosol according to this embodiment, the relationship between shear rate and steady-flow viscosity in steady-flow viscosity measurement overlaps with the relationship between angular velocity and complex viscosity in dynamic viscoelasticity measurement, and thus the Cox-Merz law holds true. In other words, the complex viscosity can be obtained indirectly by measuring the steady-flow viscosity. Furthermore, the complex viscosity can be converted to the complex modulus (the square root of the sum of the squares of the storage modulus and the loss modulus) by multiplying it by the angular velocity (2 x π x frequency).

[0079] Here, assuming that tanδ does not change between frequencies of 0.25 Hz and 2.5 Hz, the complex elastic modulus G* at 2.5 Hz is 2.5 and the complex modulus of elasticity G* at 0.25 Hz 0.25 Hz ratio G* 2.5 / G* 0.25 is the ratio of storage modulus G' 2.5 / G' 0.25 can be considered equivalent to

[0080] Storage modulus ratio G' obtained by steady flow viscosity measurement 2.5 / G' 0.25 The calculation method is based on the assumption that the Cox-Merz law is satisfied and that tanδ does not change between frequencies of 0.25 Hz and 2.5 Hz. Therefore, the ratio of the direct storage modulus G' is calculated by shear dynamic viscoelasticity measurement. 2.5 / G' 0.25 It is preferable to obtain

[0081] Second Embodiment The second embodiment relates to an ultrasound phantom and an ultrasound phantom set. The ultrasound phantom of this embodiment is a hydrosol of the present invention; a container for containing the hydrosol, the container having a holding part that comes into contact with the hydrosol and maintains the shape of the hydrosol; It has. The ultrasound phantom set of this embodiment is The above ultrasound phantom and a second ultrasound phantom comprising a second cellulose ether exhibiting an average molecular weight different from the average molecular weight of the cellulose ether contained in the ultrasound phantom, water, a sound speed adjusting agent, and a second container containing the second cellulose ether, the water, and the sound speed adjusting agent; Includes. The following is an explanation. Some of the substances have been described above, so the explanation will be omitted.

[0082] <Explanation of the ultrasound phantom> The ultrasound phantom in this disclosure is the hydrosol contained in a container described below, which is portable and can be used for calibrating an ultrasound diagnostic device. By making it portable, it can be distributed by transportation and can be carried near the ultrasound diagnostic device that the user wants to calibrate.

[0083] <Container description> The container used in the ultrasound phantom of this embodiment is intended to maintain the shape of the hydrosol of this embodiment. That is, in the ultrasound phantom of this embodiment, the container has a holder that comes into contact with the hydrosol and maintains the shape of the hydrosol, and is a container that contains the hydrosol.

[0084] The material of the container is not particularly limited, as long as it does not cause deformation of the ultrasound phantom or leakage of water. The shape of the container may be a cube, rectangular parallelepiped, cylindrical, or the like, or may be a shape that mimics an organ. Furthermore, the container may be partially filled with a material other than the hydrosol of this embodiment.

[0085] Furthermore, a lid may be provided at a position facing the acoustic coupling surface on the top of the container in order to prevent evaporation of water from the hydrosol. That is, in the ultrasound phantom of this embodiment, the container may have a lid facing the acoustic coupling surface, a holding part for maintaining the shape of the hydrosol, and a main body part that is fastened to the lid. There are no particular restrictions on the material of the lid, but it should be one that does not allow water to seep out, and it is preferable that the shape of the lid has a structure that allows it to fit tightly to the holding part or main body part.

[0086] <Acoustic coupling surface> The hydrosol in the ultrasound phantom of this embodiment preferably has an acoustic coupling surface for acoustically coupling with the acoustic probe, and the container preferably has the holding part at a position different from the acoustic coupling surface.Furthermore, the hydrosol in the ultrasound phantom of this embodiment preferably has an acoustic wave reducing part at a position opposite the acoustic coupling surface across the hydrosol, which reduces reflection of acoustic waves from the acoustic coupling surface.

[0087] The acoustic coupling surface in this embodiment refers to a surface that acoustically couples with the acoustic probe. From the viewpoint of ultrasonic wave transmissibility, the acoustic coupling surface is preferably flat. Furthermore, the acoustic coupling surface may be the hydrosol of this embodiment, or may be covered with a material other than the hydrosol of this embodiment. For example, the acoustic coupling surface may be covered with a film-like material to prevent evaporation.

[0088] Here, being acoustically coupled to the acoustic probe means that the ultrasonic waves can be transmitted well. There is a large difference in acoustic impedance between the acoustic probe and the human body (or the ultrasonic phantom), and the ultrasonic beam may be reflected and not be transmitted efficiently inside the living body.

[0089] Therefore, it is necessary to place a material that has the acoustic characteristic impedance of the human body between the acoustic probe and the probe. This is the acoustic coupling surface. By placing this acoustic coupling surface between the probe and the human body, the reflection of ultrasound can be minimized, resulting in good ultrasound transmission.

[0090] <Sound-absorbing material> The sound-absorbing material in this embodiment is a material that attenuates transmitted ultrasonic waves. That is, the sound-absorbing material is the material used in the acoustic reduction section. As a result, ultrasonic waves incident from the acoustic coupling surface are attenuated by passing through the hydrosol and then the sound-absorbing material. As a result, reflected waves from the container can be suppressed.

[0091] Any sound-absorbing material can be used as long as it has a high ultrasonic transmission loss. Rubber materials are preferable, and urethane rubber materials are particularly preferable. The higher the transmission loss, the better. -1 ·cm -1 It is preferable that it is equal to or greater than 20 dB MHz. -1 ·cm -1 or more, and more preferably 25 dB·MHz -1 ·cm -1 That's all.

[0092] <Ultrasound phantom set> By taking advantage of the aforementioned thickening mechanism of cellulose ether, it is possible to provide an ultrasound phantom set. For example, an ultrasound phantom set with the same storage modulus but different viscosities can be prepared by preparing multiple hydrosols made of multiple cellulose ethers with different molecular weights, each adjusted to have the same storage modulus. In this way, the ultrasound phantom set can be used to calibrate ultrasound equipment.

[0093] Furthermore, an ultrasound phantom set with different storage moduli but the same viscosity can be prepared by preparing a plurality of hydrosols adjusted to have the same viscosity index using a plurality of cellulose ethers with different molecular weights.

[0094] Third Embodiment The third embodiment relates to a method for manufacturing an ultrasound phantom. The method for manufacturing an ultrasound phantom according to this embodiment is as follows: A preparation step of preparing a mixed solution by mixing water, cellulose ether, and a sound speed adjusting agent; A stirring step of stirring and mixing the mixed liquid to prepare a hydrosol; pouring the hydrosol into a container; Includes. The following is an explanation. Each substance has been explained above, so further explanation will be omitted.

[0095] The method for producing the ultrasound phantom is not particularly limited. A mixture is prepared by mixing water, cellulose ether, a sound speed adjuster, and optionally other components such as an ultrasound scattering agent, a preservative, and an antifoaming agent. The mixture is stirred to obtain a hydrosol in which at least a portion of the cellulose ether is dissolved. Heating or cooling may be performed as needed.

[0096] The method for producing an ultrasound phantom according to this embodiment preferably includes a step of performing dynamic shear viscoelasticity measurement on the hydrosol after the stirring step to obtain a frequency-storage modulus curve, thereby obtaining a calibration curve for the ultrasound phantom.

[0097] The distribution of the components in the hydrosol includes two types: one in which the components are uniformly dispersed in the solvent macroscopically and in equilibrium, and the other in which the components are uniformly dissolved in the solvent at the molecular level and in equilibrium. The former type includes an ultrasonic scattering agent and an antifoaming agent, while the latter type includes a cellulose ether, a sound speed adjusting agent, and an antiseptic.

[0098] The obtained hydrosol can be poured into a container of a desired shape to obtain an ultrasound phantom. This manufacturing method allows the materials that make up the ultrasound phantom to be distributed in a packed form, adjusted to have the desired storage modulus and viscosity index. Users can create ultrasound phantoms on-site by mixing the material pack with a specified amount of water.

[0099] That is, the method for manufacturing an ultrasound phantom includes a preparation step of preparing a mixed solution containing water, cellulose ether, and a sound speed adjusting agent, a stirring step of stirring and mixing the mixed solution to prepare a hydrosol, and an injection step of pouring the hydrosol into a container of a desired shape, thereby obtaining an ultrasound phantom containing a hydrosol containing water, cellulose ether, and a sound speed adjusting agent.

[0100] Before pouring the hydrosol into a container of the desired shape, the obtained hydrosol is subjected to viscoelasticity measurement to measure the storage modulus at frequencies of 0.25 Hz and 2.5 Hz, and information is obtained as to whether the ratio of the storage modulus at frequencies of 0.25 Hz and 2.5 Hz is 2.0 or more and 15 or less, thereby making it possible to confirm whether the hydrosol according to this embodiment has been produced without any problems.

[0101] The ultrasound phantom according to this embodiment can be used as an ultrasound phantom for calibrating an ultrasound diagnostic device, such as an ultrasound dispersion method for calculating the viscosity of an organ. [Example]

[0102] The present invention will be described in detail below with reference to examples, but the present embodiment is not limited to these examples. In the following formulations, parts are by weight unless otherwise specified.

[0103] <Material> The materials used in Examples 1 to 27 and Comparative Examples 1 to 3 are listed below. [water] Ultrapure water: Ultrapure water produced by MilliQ IQ7003, purified using a combination of reverse osmosis membranes, continuous ion exchange, and germicidal UV lamps.

[0104] [Cellulose ether] C-1 Product name: hi-Metolose (registered trademark) hi90SH-4000 (manufactured by Shin-Etsu Chemical Co., Ltd.) This cellulose, whose main component is β-D-glucose, has 1.4 methoxy groups and 0.2 hydroxypropoxy groups per cellulose residue, making it a hydroxypropyl methylcellulose. The viscosity of a 2% by mass aqueous solution is 3,980 mPa·s, and it is surface-treated with glyoxal.

[0105] C-2 Product name: hi-Metolose (registered trademark) hi90SH-15000 (manufactured by Shin-Etsu Chemical Co., Ltd.) This cellulose, whose main component is β-D-glucose, has 1.4 methoxy groups and 0.2 hydroxypropoxy groups per cellulose residue, making it a hydroxypropyl methylcellulose. The viscosity of a 2% by weight aqueous solution is 14,000 mPa·s, and it is surface-treated with glyoxal.

[0106] C-3 Product name: hi-Metolose (registered trademark) hi90SH-30000 (manufactured by Shin-Etsu Chemical Co., Ltd.) This cellulose, whose main component is β-D-glucose, has 1.4 methoxy groups and 0.2 hydroxypropoxy groups per cellulose residue, making it a hydroxypropyl methylcellulose. The viscosity of a 2% by weight aqueous solution is 25,400 mPa·s, and it is surface-treated with glyoxal.

[0107] C-4 Product name: hi-Metolose (registered trademark) hi90SH-100000 (manufactured by Shin-Etsu Chemical Co., Ltd.) This cellulose, whose main component is β-D-glucose, has 1.4 methoxy groups and 0.2 hydroxypropoxy groups per cellulose residue, making it a hydroxypropyl methylcellulose. The viscosity of a 1% by mass aqueous solution is 4,290 mPa·s, and the surface is treated with glyoxal.

[0108] C-5 Product name: Metrolose (registered trademark) 60SH-4000 (manufactured by Shin-Etsu Chemical Co., Ltd.) This cellulose, whose main component is β-D-glucose, has 1.9 methoxy groups and 0.3 hydroxypropoxy groups per cellulose residue, making it a hydroxypropyl methylcellulose. The viscosity of a 2% by mass aqueous solution is 4,000 mPa·s, and it is not surface-treated with glyoxal.

[0109] C-6 Product name: METOLOSE (registered trademark) SEB-4000 (manufactured by Shin-Etsu Chemical Co., Ltd.) This cellulose, whose main component is β-D-glucose, has 1.5 methoxy groups and 0.2 hydroxyethoxy groups per cellulose residue, making it a hydroxyethyl methylcellulose. The viscosity of a 2% by mass aqueous solution is 4,000 mPa·s, and it is not surface-treated with glyoxal.

[0110] C-7 Product name: Metrolose (registered trademark) SM-4000 (manufactured by Shin-Etsu Chemical Co., Ltd.) This cellulose is primarily composed of β-D-glucose and is a methylcellulose with 1.8 methoxy groups per cellulose residue. The viscosity of a 2% by weight aqueous solution is 4,000 mPa·s, and it is not surface-treated with glyoxal.

[0111] [Sound speed adjuster] Urea (Kishida Chemical Co., Ltd.) Glycerin (Kishida Chemical Co., Ltd.)

[0112] [Other ingredients] Other polysaccharides: Agar (Kishida Chemical Co., Ltd.) Thickener: Glycerin (Kishida Chemical Co., Ltd.); since it is a water-soluble liquid, it also affects the speed of sound. Ultrasonic scattering agent: Graphite Product name: Nikabeads (registered trademark) ICB1020 (Nippon Carbon Co., Ltd.) Scaly graphite 1 Product name: MCP-10 (Nippon Graphite Industries Co., Ltd.) Average particle size: 10 μm Scaly graphite 2 Product name: MCP-15 (Nippon Graphite Industries Co., Ltd.) Average particle size: 15 μm Preservative: Methyl parahydroxybenzoate (Kishida Chemical Co., Ltd.) Antifoaming agent: Silicone-based antifoaming agent Product name: KS-537 (Shin-Etsu Chemical Co., Ltd.)

[0113] <Evaluation method> [Storage modulus ratio] The hydrosol obtained by stirring a mixture of water, cellulose ether, sound speed adjuster, and optionally other ingredients such as ultrasound scattering agents, preservatives, and antifoaming agents was subjected to dynamic viscoelasticity measurements at 25°C and two frequencies, 0.25 Hz and 2.5 Hz, using a viscoelasticity measuring device (MCR302, manufactured by Anton Paar Japan Co., Ltd.) and a φ25 mm parallel plate, and the storage modulus was obtained at each frequency.

[0114] The storage modulus at a frequency of 2.5 Hz is G' 2.5 The storage modulus at a frequency of 0.25 Hz is G' 0.25 Then, G' 2.5 / G'0.25 If the score was between 2.0 and 15, the score was evaluated as OK.

[0115] G' 2.5 / G' 0.25 If the viscosity is 2.0 or more, it can be used as a high viscosity ultrasound phantom. On the other hand, if it exceeds 15, it has almost no elastic properties and is therefore unsuitable as an ultrasound phantom.

[0116] [Sound speed measurement] To measure the sound velocity, a sample for sound velocity measurement was prepared by filling a jig for sound velocity measurement with a diameter of 64 mm and a length of 40 mm with hydrosol and sealing both ends with acrylic plates.

[0117] The specific method for measuring the speed of sound is as follows: Fill a water tank with water and record the water temperature. Place a transducer (V328-SU, Olympus Corporation, transmission frequency 3.5 MHz) and a needle-type hydrophone (Toray Engineering D Solutions Co., Ltd.) in the water, and place a jig filled with water for measuring the speed of sound between them.

[0118] In this state, the ultrasonic waves emitted from the transducer are received by the hydrophone, and waveform data is obtained over time. Next, a sample filled with hydrosol for measuring the speed of sound is placed between the transducer and the hydrophone, and waveform data over time is similarly obtained.

[0119] A cross-correlation analysis is performed between the waveform when there is only water and the waveform when the hydrosol is installed, and the delay time between the arrival times of the waveforms is measured. When the delay time is τ, the thickness of the sample is t, and the water temperature is T, the sound velocity C1 of the water and the sound velocity C2 of the sample can be calculated by the following formula. C1=1403+5×T-0.06×T 2 +0.0003×T 3 C2=t / (T+t / C1)

[0120] (Examples 1 to 40, Comparative Examples 1 to 3) <How to create an ultrasound phantom> [Manufacturing example] As an example of a manufacturing procedure for an ultrasound phantom, the manufacturing procedure of Example 1 will be described. For the other Examples 2 to 40 and Comparative Examples 1 to 3, ultrasound phantoms were manufactured using the same manufacturing procedure as Example 1, but with different types and amounts of materials according to the formulations in Tables 1 and 2.

[0121] An ultrasound-absorbing tile (Aptflex F28 manufactured by Precision Acoustics, transmission loss 30 dB·MHz-1·cm-1) cut to a width of 100 mm, depth of 100 mm, and height of 10 mm was attached to the bottom of a polypropylene container with an inner diameter of 120 mm width, 120 mm depth, and 90 mm height using waterproof double-sided tape.

[0122] A 2L disposable cup was charged with 1410g of ultrapure water and 0.03g of antifoaming agent (KS-537), and a stirrer equipped with a 100mm diameter flat-panel impeller was installed. A well-mixed mixture of 90g of sonic velocity regulator (urea), 60g of ultrasonic scattering agent (Nicabeads ICB1020), 0.75g of preservative (methyl parahydroxybenzoate), and 37.5g of cellulose ether C-1 (hi-Metolose hi90SH-4000) was added little by little while stirring at 150 rpm. The mixture was then stirred at 150 rpm for 1 hour at room temperature. The rotation speed was then reduced to 75 rpm and the mixture was stirred for 30 minutes to produce a hydrosol.

[0123] Next, the above hydrosol was poured into a polypropylene container fitted with the above ultrasound-absorbing tiles to a height of 1 cm from the top of the container to prepare an ultrasound phantom.

[0124] The obtained hydrosol was evaluated for the viscosity index as described above to confirm whether the desired viscosity was obtained. Furthermore, the obtained hydrosol was filled into a jig for sound velocity measurement, and both ends were sealed with acrylic plates to prepare a sample for sound velocity measurement, and the sound velocity was measured by the method described above.

[0125] As an example of the manufacturing procedure for an ultrasound phantom, the manufacturing procedure for Comparative Example 1 will be described. For Comparative Example 2, an ultrasound phantom was manufactured using the same procedure, but with the formulation in Table 1, with only the type and amount of material changed.

[0126] A 2-L separable flask was charged with 1,410 g of ultrapure water and 0.03 g of antifoaming agent (KS-537), and a stirring device equipped with a 75 mm half-moon stirring blade was installed. A well-mixed mixture of 90 g of sonic speed regulator (urea), 60 g of ultrasonic scattering agent (Nicabeads® ICB1020), 0.75 g of preservative (methyl parahydroxybenzoate), and 17.5 g of agar was added little by little while stirring at 150 rpm. The flask was then placed in a 90°C oil bath and stirred at 150 rpm for 1 hour to produce a sol containing the dissolved agar.

[0127] In the embodiments and examples described in this specification, all components other than water are weighed assuming the mass of a sufficiently dried anhydrous substance (dry mass). The dry mass can be determined by the loss on drying method specified in JIS K0068.

[0128] After the evaluation for Table 1, the mixed solution was poured into a polypropylene container with the ultrasound-absorbing tiles attached thereto to a height of 1 cm from the top of the container to prepare an ultrasound phantom.

[0129] The obtained hydrosol was filled into a jig for measuring the sound velocity, both ends of which were sealed with acrylic plates, and the jig was left overnight at room temperature to prepare a sample for measuring the sound velocity, and the sound velocity was measured by the method described above.

[0130] The obtained hydrosol was cooled to room temperature and used to evaluate the viscosity index. The results obtained are shown in Tables 1 and 2.

[0131] [Table 1]

[0132] [Table 2]

[0133] In Tables 1 and 2, the numerical values ​​for each material in the recipe column indicate the mass of each material (unit: parts by mass). From the results of Tables 1 and 2, Examples 1 to 40 according to the present invention all have a G' 2.5 / G' 0.25 The viscosity was in the range of 2.0 to 15.0, and the sound speed was in the range of 1530 to 1540 m / s. In other words, it was confirmed that high viscosity and a temperature close to that of a living body were compatible.

[0134] In the results in Table 1, Comparative Example 1, which does not use cellulose ether, has a G' 2.5 / G' 0.25 In addition, in Comparative Example 2, which used glycerin, a thickener having the effect of adjusting the sound velocity, when the sound velocity was adjusted to 1530 to 1540 m / s, which is the range of the living body, G' 2.5 / G' 0.25 The viscosity was not increased sufficiently because the value was less than 2.0.

[0135] Furthermore, in Comparative Example 3, in which no sound speed adjusting agent was added, the viscosity exceeded the evaluation standard, but the sound speed did not reach the range of that in living tissue.

[0136] The disclosure of this embodiment includes the following configurations and methods. (Configuration 1) A hydrosol applied to an ultrasound phantom, comprising: A hydrosol comprising water, a cellulose ether, and a sound speed modifier. (Configuration 2) 2. The hydrosol according to claim 1, wherein the hydroxy group derived from the glucose residue of the cellulose ether is substituted with at least one group selected from the group consisting of a methoxy group, a hydroxyethoxy group, and a hydroxypropoxy group. (Configuration 3) 3. The hydrosol according to claim 1 or 2, wherein the cellulose ether is modified with, on average, 0.4 to 2.4 methoxy groups, 0 to 0.6 hydroxyethoxy groups, and 0 to 0.5 hydroxypropoxy groups per glucose residue. (Configuration 4) 4. The hydrosol according to any one of aspects 1 to 3, wherein the cellulose ether is surface-treated with glyoxal. (Configuration 5) In dynamic shear viscoelasticity measurements at 25°C, the storage modulus at a frequency of 2.5 Hz is defined as G'. 2.5 The storage modulus at a frequency of 0.25 Hz is G' 0.25 Then, G' 2.5 / G' 0.25 5. The hydrosol according to any one of configurations 1 to 4, wherein the value of the σ is 2.0 or more and 15 or less. (Configuration 6) In dynamic shear viscoelasticity measurements at 25°C, the storage modulus at a frequency of 2.5 Hz is defined as G'. 2.5 The storage modulus at a frequency of 0.25 Hz is G' 0.25 Then, G' 2.5 / G' 0.25 6. The hydrosol according to any one of configurations 1 to 5, wherein the value of the σ is 2.0 or more and 10 or less. (Configuration 7) The hydrosol according to any one of configurations 1 to 6, a container for containing the hydrosol, the container having a holding part that comes into contact with the hydrosol and maintains the shape of the hydrosol; An ultrasound phantom having (Configuration 8) the hydrosol having an acoustic coupling surface for acoustically coupling with an acoustic probe; 8. The ultrasound phantom according to claim 7, wherein the container has the holding portion at a position different from the acoustic coupling surface. (Configuration 9) 9. The ultrasound phantom according to claim 8, further comprising an acoustic wave reducing section that reduces reflection of acoustic waves from the acoustic coupling surface, at a position facing the acoustic coupling surface across the hydrosol. (Configuration 10) 10. The ultrasound phantom according to claim 8 or 9, wherein the container has a lid portion facing the acoustic coupling surface, the holding portion, and a main body portion fastened to the lid portion. (Configuration 11) An ultrasound phantom according to any one of configurations 7 to 10, a second ultrasound phantom comprising a second cellulose ether exhibiting an average molecular weight different from the average molecular weight of the cellulose ether contained in the ultrasound phantom, water, a sound speed adjusting agent, and a second container containing the second cellulose ether, the water, and the sound speed adjusting agent; Ultrasound phantom set including: (Method 1) A preparation step of preparing a mixed solution by mixing water, cellulose ether, and a sound speed adjusting agent; A stirring step of stirring and mixing the mixed liquid to prepare a hydrosol; pouring the hydrosol into a container; A method for manufacturing an ultrasound phantom, comprising: (Method 2) The method for producing an ultrasound phantom according to Method 1 includes, after the stirring step, a step of performing dynamic shear viscoelasticity measurement on the hydrosol to obtain a frequency-storage modulus curve.

Claims

1. A hydrosol applied to an ultrasound phantom, comprising: A hydrosol comprising water, a cellulose ether, and a sound speed modifier.

2. The hydrosol according to claim 1, wherein the cellulose ether has a hydroxy group derived from a glucose residue substituted with at least one selected from the group consisting of a methoxy group, a hydroxyethoxy group, and a hydroxypropoxy group.

3. The hydrosol according to claim 1, wherein the cellulose ether is modified with, on average, 0.4 to 2.4 methoxy groups, 0 to 0.6 hydroxyethoxy groups, and 0 to 0.5 hydroxypropoxy groups per glucose residue.

4. 2. The hydrosol of claim 1, wherein the cellulose ether is surface-treated with glyoxal.

5. In dynamic shear viscoelasticity measurement at 25°C, the storage modulus at a frequency of 2.5 Hz is G' ２．５ The storage modulus at a frequency of 0.25 Hz is G' ０．２５ Then, G' ２．５ / G' ０．２５ The hydrosol according to claim 1, wherein the σ is 2.0 or more and 15 or less.

6. In dynamic shear viscoelasticity measurement at 25°C, the storage modulus at a frequency of 2.5 Hz is G' ２．５ The storage modulus at a frequency of 0.25 Hz is G' ０．２５ Then, G' ２．５ / G' ０．２５ The hydrosol according to claim 1, wherein the σ is 2.0 or more and 10 or less.

7. A hydrosol according to claim 1 or 2; An ultrasound phantom comprising: a holding portion that comes into contact with the hydrosol and maintains the shape of the hydrosol; and a container that contains the hydrosol.

8. the hydrosol having an acoustic coupling surface for acoustically coupling with an acoustic probe; The ultrasound phantom according to claim 7 , wherein the container has the holding portion at a position different from the acoustic coupling surface.

9. The ultrasound phantom according to claim 8 , further comprising an acoustic wave reducing portion that reduces reflection of acoustic waves from the acoustic coupling surface, at a position facing the acoustic coupling surface across the hydrosol.

10. The ultrasound phantom according to claim 8 , wherein the container has a lid portion facing the acoustic coupling surface, the holding portion, and a main body portion fastened to the lid portion.

11. The ultrasound phantom according to claim 7; a second ultrasound phantom comprising a second cellulose ether exhibiting an average molecular weight different from that of the cellulose ether, water, a sound speed adjusting agent, and a second container containing the second cellulose ether, the water, and the sound speed adjusting agent; Ultrasound phantom set including:

12. A preparation step of preparing a mixed solution by mixing water, cellulose ether, and a sound speed adjusting agent; A stirring step of stirring and mixing the mixed liquid to prepare a hydrosol; pouring the hydrosol into a container; A method for manufacturing an ultrasound phantom, comprising:

13. The method for producing an ultrasound phantom according to claim 12, further comprising the step of performing dynamic shear viscoelasticity measurement on the hydrosol after the stirring step to obtain a frequency-storage modulus curve.

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