Patent Description:
Interventional radiology, also called interventional therapeutics, is an emerging discipline that has been developed rapidly in recent years and integrates imaging diagnosis and clinical therapy. The interventional radiology is a general term of a series of technologies of leading a specific implantable device (hereinafter referred to as "implant") into a diseased portion of a human body through a natural orifice or a tiny wound of the human body for minimally invasive therapy with a puncture needle, a catheter and other intervention equipment under the guide and monitoring of imaging equipment such as Digital Subtraction Angiography (DSA), Computed Tomography (CT), ultrasound and magnetic resonance. The existing implant substrates are made of metal-based and non-metal-based materials, such as non-absorbable metal materials: stainless steel, a nickel-titanium alloy, a cobalt-chromium alloy and the like, or absorbable metal materials: a magnesium base, an iron base, a zinc base and the like, and degradable polymer-based materials such as polylactic acid, polycaprolactone or its copolymer and a blend.

When the radiation density of the material of the implant substrate is greater than the density of a human tissue or organ around an implanted position, a contrast image may be formed for diagnosis or clinical treatment via X-ray irradiation. An implant with a certain thickness made of stainless steel, nickel-titanium alloy or cobalt-chromium alloy, has a relatively high radiation density, and may have relatively high X-ray radiopacity after being implanted. For example, a stainless steel vascular stent with a thickness of more than <NUM> microns may form a distinct image by itself in the medical imaging equipment DSA, so that the position and the shape may be easily identified, or the stent has good visibility, wherein the thickness is the wall thickness of the implant.

For a vascular stent, the smaller the thickness, the better the fitting with the blood vessel wall, thus lower shear interference of a stent strut to blood flow in a blood vessel would be caused, which is more favorable for avoiding thrombosis. Therefore, for a medical application, it tends to adopt a relatively thin vascular stent. However, when the thickness of the stainless steel stent is less than <NUM> microns, the image of the stent displayed under the DSA equipment is not clear enough, and the position and the shape of the stent are hard to visually identify, so that it is necessary to improve the visibility.

As the density of an implant made of the magnesium-based alloy and a polymer such as polylactic acid, polycaprolactone or its copolymer, and the like is very low, the obtained implant may have a thickness reaching the hundred-micron level, but its visibility under the DSA equipment in the prior art is still very poor. For example, a vascular stent which is made of the polymer and has the wall thickness of <NUM> to <NUM> microns is nearly invisible in the medical imaging equipment DSA, which leads to a fact that a doctor cannot accurately position the stent in a surgical procedure.

Therefore, for a polymer-based implant with extremely poor visibility, as well as a relatively thin metal-based implant, it is necessary to dispose an extra radiopaque structure at a proper position on the implant and enable the radiopaque structure to be identified by the doctor under the DSA to assist the doctor in accurately positioning the implant.

Generally, it is desirable that the smaller the size of the radiopaque structure the better to avoid the influence on the design and the relevant mechanical property of the implant. However, if the size of the radiopaque structure is not properly set, particularly when the adoption of the radiopaque structure with a relatively small thickness (<NUM> to <NUM> microns) is the only option because of the limit of designs of some thin-wall implants (<NUM> to <NUM> microns), the extremely small size of the radiopaque structure may cause poor visibility, and the aim of assisting in judging the position and the shape of the implant may not be achieved.

<CIT> discloses a medical scaffold formed of a pattern of struts interconnected by links, where a marker may be provided on the links. The marker may consist of a radiopaque sheet material wrapped around the link and held in place by a drug coating deposited over the scaffold.

<CIT> describes a radiopaque marker for locating a medical device in vivo comprising a catheter body, a matrix material and a metal, wherein said metal is blended into the matrix material to form a radiopaque band. The radiopaque band is bonded to the catheter for providing a contrast e.g. during angioplasty surgery.

In view of the above, an object of the invention is to provide a radiopaque structure having good or excellent visibility and an implantable medical device having the radiopaque structure to overcome the above-mentioned shortcomings.

According to the present invention, a radiopaque structure for use in an implantable medical device is provided as defined in claim <NUM>. The radiopaque structure, includes at least one radiopaque unit. Each radiopaque unit includes at least one radiopaque object; in at least one incidence direction of a light source, all the radiopaque objects in the radiopaque structure are divided into n regions according to the thickness in the incidence direction; a projection area Sm of m regions of the n regions and the effective thickness dm of the m regions accord with Sm-<NUM>(dm)a≥<NUM>, where a is more than or equal to -<NUM> and less than or equal to -<NUM>, and m is more than or equal to <NUM> and less than or equal to n.

According to the invention, in the incidence direction, the effective thickness dm of the m regions of the n regions ranges from <NUM> to <NUM>.

According to the invention, in the incidence direction, the projection area Sm of the m regions of the n regions is less than or equal to <NUM><NUM>.

In one embodiment, in the incidence direction, the projection area Sm of the m regions of the n regions is less than or equal to <NUM><NUM>.

In one embodiment, the radiopaque structure only includes one radiopaque unit, and the radiopaque unit includes at least one radiopaque object.

In one embodiment, the radiopaque unit includes multiple mutually spaced radiopaque objects.

In one embodiment, the radiopaque structure includes multiple mutually spaced radiopaque units, and each radiopaque unit includes at least one radiopaque object.

In one embodiment, each radiopaque unit includes multiple mutually spaced radiopaque objects.

In one embodiment, the radiopaque object is only made of a radiopaque material, and the radiopaque material is selected from the group consisting of gold, platinum, osmium, rhenium, tungsten, iridium, rhodium, tantalum, barium sulfate, columbium sesquioxide, titanium oxide, zirconium oxide, elemental iodine and iodide.

In one embodiment, when the radiopaque object includes various radiopaque materials, the average atomic number of a mixture of the various radiopaque materials is less than the atomic number of gold.

In one embodiment, the radiopaque object includes a radiopaque material and a non-radiopaque material, and the radiopaque material is selected from the group consisting of gold, platinum, osmium, rhenium, tungsten, iridium, rhodium, tantalum, barium sulfate, columbium sesquioxide, titanium oxide, zirconium oxide, elemental iodine and iodide.

In one embodiment, the non-radiopaque material is a degradable polymer material.

According to the present invention, an implantable medical device is also provided as defined in claim <NUM>.

The medical device includes a substrate and at least one radiopaque structure which is mentioned in any item above and is connected with the substrate.

In one embodiment, there are multiple radiopaque units, and the radiopaque objects of at least two radiopaque units have an overlapping region in the incidence direction.

In one embodiment, there are multiple radiopaque structures, wherein at least one radiopaque structure includes multiple mutually spaced radiopaque units, and each radiopaque unit in the radiopaque structure includes multiple mutually spaced radiopaque objects; and at least another one radiopaque structure includes one radiopaque unit which includes multiple mutually spaced radiopaque objects.

In one embodiment, the substrate is a metal having a thickness less than or equal to <NUM> microns, or a polymer having a thickness less than or equal to <NUM> microns.

In one embodiment, the substrate is a magnesium-based alloy having a thickness less than or equal to <NUM> microns.

In one embodiment, the substrate is a zinc-based alloy having a thickness less than or equal to <NUM> microns.

In one embodiment, the substrate is an iron-based alloy having a thickness less than or equal to <NUM> microns.

According to the radiopaque structure and the implantable medical device including the radiopaque structure of the present application, in at least one incidence direction of the light source, at least one group of the projection area Sm and the effective thickness dm of all the radiopaque objects in the radiopaque structure accords with Sm-<NUM>(dm)a≥<NUM>, so that the radiopaque structure has good or excellent visibility.

A further description will be made to the present application in combination with accompanying drawings showing embodiments as follows. In the drawings:.

For the purpose of making the present application more clear, a detailed description will be made of specific embodiments in conjunction with the drawings.

Unless otherwise specified, all technical and scientific terms used herein are the same as meanings of general understandings of persons skilled in the art. The visibility of the present application may be measured under a CGO-2100C type medical angiography X-ray machine produced by China Resources Wandong Medical Equipment Co. , and X-ray pulse prospective imaging parameters are selected as follows: ultrashort pulse (<NUM> to <NUM> frames/second), tube pressure of <NUM> to <NUM> kV and current of <NUM> to <NUM> mA. These parameters all represent a general technical level of the current angiography. In order to reduce the radiation dosage to a patient and a surgeon, on the premise of not affecting the image quality, such parameter settings as high voltage, low current and low frame frequency are generally used as far as possible.

As shown in <FIG>, the visibility of a radiopaque structure in an implant under imaging equipment may be judged according to an image formed by the radiopaque structure under the imaging equipment. When an infill and a boundary of the image are relatively fuzzy, but the position and the shape still may be visually identified with eyes alone, the visibility is good; and when the infill and the boundary of the image are very clear, and the position and the shape may be easily visually identified with the eyes alone, the visibility is excellent.

The radiopaque structure of the present application only represents a radiopaque structure having good or excellent visibility, and includes at least one radiopaque unit, and each radiopaque unit includes at least one radiopaque object. The radiopaque unit is a set of the radiopaque objects cooperating to form one visible image. The radiopaque structure of the present application may only include one radiopaque unit, and the radiopaque unit only includes one integral radiopaque object. In at least one incidence direction of a light source, the radiopaque object may form one integral image with good or excellent visibility. Or the radiopaque structure may only include one radiopaque unit, and the radiopaque unit includes multiple mutually spaced radiopaque objects. In at least one incidence direction of the light source, the multiple mutually spaced radiopaque objects may form one integral image with good or excellent visibility. Or the radiopaque structure includes multiple mutually spaced radiopaque units, and each radiopaque unit includes at least one radiopaque object. In at least one incidence direction of the light source, all the radiopaque objects included in the multiple mutually spaced radiopaque units may form one integral image with good or excellent visibility. When the radiopaque unit includes multiple radiopaque objects, it may include a radiopaque object which is invisible by itself, but is visible after cooperating with other radiopaque objects, namely the radiopaque object which contributes to the visibility of a finally observed image, or it may also include a radiopaque object which is invisible by itself and may not contribute to the visibility of the finally observed image after cooperating with other radiopaque objects.

No matter what a specific composition of the radiopaque structure is, the radiopaque structure may form an intact, continuous and independent image with good or excellent visibility under the imaging equipment. The image may be of a point shape, a ball shape, an opened line shape or a closed line shape.

It should be understood that the radiopaque objects may be integral radiopaque wires, radiopaque rings or radiopaque blocks and the like, and may be directly twined on the surface of an implanted medical device or embedded into grooves in the surface of the implanted medical device, or also fill open holes in the implanted medical device.

The visibility of the radiopaque structure under the imaging equipment depends on two influence factors: the radiation impenetrability of the radiopaque object in the radiopaque structure and the detectability of the radiopaque structure.

The radiation impenetrability of the radiopaque object is determined according to the ratio of the emergence intensity of the light source to the incidence intensity. As shown in FORMULA (<NUM>): <MAT>.

I/I<NUM> is the ratio of the emergence intensity of the light source penetrating through the radiopaque object to the incidence intensity. Smaller I/I<NUM> shows higher radiation impenetrability of the radiopaque object. Therefore, under the light source with the same incidence intensity, the radiation impenetrability of the radiopaque object is in direct proportion to the linear attenuation coefficient µ of the radiopaque object and the thickness d of the radiopaque object along the incidence direction of the light source, that is, if the linear attenuation coefficient µ and the thickness d of the radiopaque object are greater, its radiation impenetrability is higher, but the linear attenuation coefficient µ of the radiopaque object is related to the atomic number of the radiopaque object: the greater the atomic number of the radiopaque object, the greater its linear attenuation coefficient µ. That is, if the atomic number of the radiopaque object and the thickness along the incidence direction of the light source are greater, its radiation impenetrability is higher.

The detectability of the radiopaque structure jointly depends on imaging equipment, the visual resolution and the projection area of all the radiopaque objects in the radiopaque structure in the incidence direction of the light source. Under the condition that the imaging equipment and the visual resolution are confirmed, the detectability of the radiopaque structure depends on the projection area of all the radiopaque objects in the radiopaque structure along the incidence direction of the light source.

It should be noted that for the same radiopaque structure, when the incident directions of the light source are different, the projection areas of all the radiopaque objects of the radiopaque structure may be possibly different, and correspondingly, images formed by the radiopaque structure in different incidence directions of the light source also may be different. For example, the radiopaque structure includes one straight-line segment radiopaque object. When the incidence direction of the light source is parallel to a lengthwise direction of the straight-line segment, the formed image is a point; and when the incidence direction of the light source is perpendicular to the lengthwise direction of the straight-line segment, the formed image is a straight-line segment.

It can be known from the visibility analysis for the radiopaque structure under the imaging equipment that the visibility of the radiopaque structure is related to the atomic number of the radiopaque object and the projection area and the thickness of the radiopaque object in the incidence direction of the light source.

A radiopaque object material is generally a heavy metal which is selected from at least one of or an alloy of gold, platinum, osmium, rhenium, tungsten, iridium, rhodium or tantalum and the like. The radiopaque object material also may be a metal compound such as barium sulfate, columbium sesquioxide, titanium oxide or zirconium oxide, or further may be a non-metal such as elemental iodine or iodide. Different radiopaque object materials have different atomic numbers.

In the present application, in a certain incidence direction of the light source, all the radiopaque objects of the radiopaque structure are divided into n regions (n is more than or equal to <NUM>) according to their thicknesses in the incidence direction. It should be understood that the thicknesses of the n regions may be different from one another, or partially equal, or totally equal. When n is more than or equal to <NUM>, the thicknesses of the radiopaque objects in each region may be equal to or different from those of the radiopaque objects in other regions; and when n is equal to <NUM>, it means that the thicknesses of all the radiopaque objects are equal. It should be understood that when the radiopaque structure includes one radiopaque object, the radiopaque object is directly divided into n regions according to its thickness in the incidence direction, and each region has a projection area in the incidence direction. When the radiopaque structure includes multiple mutually spaced radiopaque objects which are not overlapped in the incidence direction, the radiopaque objects are directly divided into n regions according to their thicknesses in the incidence direction, and the projection area of the n regions in the incidence direction is equal to a sum of the projection areas of each region of the n regions in the incidence direction. When the radiopaque structure includes multiple mutually spaced radiopaque objects which are overlapped in the incidence direction, the thickness of the radiopaque object overlapping region in the incidence direction shall be a sum of the thicknesses of each radiopaque objects in the overlapping region, so that before the thicknesses of the multiple radiopaque objects are divided into n regions in the incidence direction, the thicknesses of all the radiopaque objects in the overlapping region should be summed up and deemed as an overall thickness, and for the projection area of the thickness region subjected to overlapping processing in the incidence direction, the projection area of each radiopaque object in the overlapping region is only calculated once.

M regions are taken from the n regions randomly, where m is more than or equal to <NUM> and less than or equal to n. For each of the m regions in the incidence direction, the projection area is Si, and the thickness is di, where i is more than or equal to <NUM> and less than or equal to m. It should be understood that the projection area Sm of the m regions is a sum of the projection areas Si of the respective m regions in the incidence direction of the light source, namely <MAT>. It is defined that an average thickness corresponding to the projection area Sm is the effective thickness dm, <MAT>. There are <MAT> methods for randomly taking the m regions from the n regions, so that there are <MAT> groups of (dm, Sm) values for any m regions.

For any m regions in the n regions formed by dividing all the radiopaque objects of the radiopaque structure in a certain incidence direction of the light source, the sum of the projection areas Sm and the effective thickness dm in the incidence direction may be calculated by using three-dimensional model processing software after the radiopaque structure is subjected to three-dimensional reconstruction with Micro-CT.

In the present application, the radiopaque structure accords with the condition that in at least one incidence direction of the light source, at least one group of effective thickness dm and projection area Sm of all the radiopaque objects in the radiopaque structure accords with Sm-<NUM>(dm)a≥<NUM> where a is more than or equal to -<NUM> and less than or equal to -<NUM>. To be more specific, only if a is one value more than or equal to -<NUM> and less than or equal to -<NUM>, at least one group of effective thickness dm and projection area Sm of all the radiopaque objects in the radiopaque structure may accords with Sm-<NUM>(dm)a≥<NUM>. At the moment, the radiopaque structure has good or excellent visibility.

With reference to <FIG>, visibility curves under conditions ofSm-<NUM>(dm)-<NUM>=<NUM>, Sm-<NUM>(dm)-<NUM>=<NUM> and Sm-<NUM>(dm)-<NUM>=<NUM> are shown respectively. The radiopaque structures corresponding to the curves have good visibility. It can be known according to mathematics that radiopaque structures corresponding to points located in regions above the visibility curves also have good or excellent visibility, and radiopaque structures corresponding to points located in regions below the visibility curves have poor visibility. In the present application, the regions above the visibility curves are regions where results are more than <NUM> after Sm and dm are substituted into Sm-<NUM>(dm)a (where a is more than or equal to -<NUM> and less than or equal to -<NUM>). Similarly, the regions below the visibility curves are regions where results are less than <NUM> after Sm and dm are substituted into Sm-<NUM>(dm)a (where a is more than or equal to -<NUM> and less than or equal to-<NUM>).

It should be noted that in the existing radiopaque materials, the atomic number of gold is the greatest, so that on the premise of the same thickness, the gold has the highest radiation impenetrability. It should be understood that the radiopaque object of the radiopaque structure may be prepared by mixing various radiopaque materials, so that the average atomic number of a mixture of the various radiopaque materials is less than the atomic number of the gold, that is, the radiation impenetrability of the mixture of the various radiopaque materials is lower than that of the only gold serving as the radiopaque material. Therefore, in the incidence direction of same X-ray, in order to obtain the same visibility as that of the radiopaque structure only taking the gold as the radiopaque object, the projection area Sm and/or the effective thickness dm of the radiopaque object prepared by mixing the various radiopaque materials may be increased relative to the projection area Sm and/or the effective thickness dm of the gold serving as the radiopaque object, that is, the result obtained by substituting the projection area Sm and the effective thickness dm of the radiopaque object prepared by mixing the various radiopaque materials into the Sm-<NUM>(dm)a (where a is more than or equal to -<NUM> and less than or equal to -<NUM>) should be more than <NUM>.

It should be understood that the radiopaque object of the radiopaque structure also may be prepared by mixing a radiopaque material with a non-radiopaque material, for example, the radiopaque object may be prepared by mixing the radiopaque material with a polymer. The polymer may be a degradable polymer selected from polylactic acid, polylactic acid-glycolic acid, poly-glycolide lactide and the like. The volume fraction of the radiopaque material in the radiopaque object is more than <NUM> percent and less than <NUM> percent. When the radiopaque material is mixed with the non-radiopaque material according to the certain volume fraction in the radiopaque object, the effective thickness dm of the radiopaque object in the incidence direction of the light source is a product of the volume fraction of the radiopaque material in the radiopaque object and the average thickness of the radiopaque object. When the effective thickness dm and the projection area Sm of the radiopaque object prepared by mixing the radiopaque material and the non-radiopaque material in at least one incidence direction of the light source accord with Sm-<NUM>(dm)a≥<NUM>, where a is more than or equal to -<NUM> and less than or equal to -<NUM>, the radiopaque structure has good or excellent visibility.

The present application further provides an implantable medical device. The implantable medical device includes a substrate and at least one of the above radiopaque structures connected with the substrate. The substrate may be one or several of an iron-based alloy, a magnesium-based alloy, a zinc-based alloy, an absorbable polymer, stainless steel, a nickel-titanium alloy and a cobalt-chromium alloy. The iron-based alloy substrate may be pure iron or an iron-based alloy with carbon content less than or equal to <NUM> weight percent, for example, a product obtained by nitriding and/or carburizing the pure iron. The implantable medical device may be a cardiovascular stent, a cerebrovascular stent, a peripheral vascular stent, a non-vascular stent, a spring ring, an occluder or a vena cava filter, an internal fixation implant such as a bone nail, a bone lamella, an intramedullary needle or a suture, and some other small-sized implanted devices. When the substrate is a metal material, its thickness may be less than or equal to <NUM> microns, and further, the substrate may be a magnesium-based alloy having the thickness less than or equal to <NUM> microns, or a zinc-based alloy having the thickness less than or equal to <NUM> microns, or an iron-based alloy having the thickness less than or equal to <NUM> microns. When the substrate is a polymer, its thickness may be less than or equal to <NUM> microns. The radiopaque structure may be directly embedded into the substrate in a way of perforating the substrate, or twisted on the surface of the substrate, or partially embedded into the substrate and partially protruding from the surface of the substrate, and also may be connected with the substrate through other auxiliary members. It is worth mentioning that when the device, such as a tubular vascular stent, includes a cavity, the thickness is the wall thickness, and the substrate structure may be disposed on a connection member of two adjacent circles of waveform ring-like objects connected with the stent.

No matter whether the implantable medical device is disposed outside or implanted into a body, the radiopaque structure accords with the condition that in at least one incidence direction of a light source, at least one group of effective thickness dm and projection area Sm of all radiopaque objects of the radiopaque structure accords with Sm-<NUM>(dm)a≥<NUM>, wherein a is more than or equal to -<NUM> and less than or equal to -<NUM>.

It should be understood that the radiopaque structure on the implanted medical device may only include one radiopaque unit. In at least one incidence direction of the light source, at least one group of effective thickness dm and projection area Sm of all radiopaque objects of the radiopaque unit accords with Sm-<NUM>(dm)a≥<NUM>, wherein a is more than or equal to -<NUM> and less than or equal to -<NUM>, so that the radiopaque structure in the implanted medical device has good or excellent visibility. Alternatively, the radiopaque structure on the implanted medical device also may include multiple mutually spaced radiopaque units. The effective thickness dm and the projection area Sm of all the radiopaque objects of each radiopaque unit do not accord with the above characteristic relation, or the effective thickness dm of all the radiopaque objects of each radiopaque unit does not accord with the above characteristic relation, but in at least one incidence direction of the light source, the multiple mutually spaced radiopaque units have a radiopaque object overlapping portion, so that in this incidence direction, at least one group of effective thickness dm and projection area Sm of all the radiopaque objects of a combination of the multiple radiopaque units accords with Sm-<NUM>(dm)a≥<NUM>, wherein a is more than or equal to -<NUM> and less than or equal to -<NUM>, so that the radiopaque structure in the implanted medical device has good or excellent visibility. Alternatively, the radiopaque structure on the implanted medical device also may include multiple mutually spaced radiopaque units. The effective thickness dm and the projection area Sm of all the radiopaque objects of each radiopaque unit do not accord with the above characteristic relation, and in at least one incidence direction of the light source, the multiple mutually spaced radiopaque units do not have the radiopaque object overlapping portion, but at least one group of effective thickness dm and projection area Sm of all the radiopaque objects of a combination of the multiple radiopaque units accord with Sm-<NUM>(dm)a≥<NUM>, wherein a is more than or equal to -<NUM> and less than or equal to -<NUM>, so that the radiopaque structure in the implanted medical device has good or excellent visibility.

In this present application, in order to better adapt to a small-sized implantable medical device and avoid influence on the mechanical property of the implantable medical device, the projection area Sm of all the radiopaque objects of each radiopaque structure in the incidence direction is less than or equal to <NUM><NUM>.

In the present application, according to the invention, in the incidence direction, the effective thickness dm of all the radiopaque objects of the radiopaque structure ranges from <NUM> to <NUM>.

A further description will be made to the technical scheme of the present application in combination with specific embodiments and contrasts as follows. It should be noted that due to the precision limitation of a measuring instrument, the measurement precision of the projection areas of the radiopaque objects in the following embodiments shall include three decimal places, so that (Sm, dm) in the following embodiments accord with Sm-<NUM>(dm)a=<NUM>, including a situation that Sm-<NUM>(dm)a infinitely approaches to <NUM> after (Sm, dm) are substituted, and an absolute value of Sm-<NUM>(dm)a herein is defined to be less than <NUM>/<NUM>, which is deemed to infinitely approach to <NUM>. It should be understood that an image obtained by enabling Sm-<NUM>(dm)a to infinitely approach to <NUM> and an image obtained under the condition of Sm-<NUM>(dm)a=<NUM> are undifferentiated under visual or eye identification.

An iron-based alloy vascular stent includes a radiopaque structure. The radiopaque structure only includes one radiopaque unit which only includes an integral block-shaped radiopaque object. The stent includes multiple mutually spaced waveform ring-like objects, and any two adjacent waveform ring-like objects are connected through a connection member. A hole is formed in the connection member which is located at the proximal end of the stent, and is filled with the radiopaque object, thus the radiopaque structure is formed. The radiopaque object is only made of gold and has a coverage area of <NUM><NUM> in the circumferential direction of the stent. Under irradiation of an X-ray with an incidence direction approximately perpendicular to the coverage surface of the radiopaque object, the radiopaque object has a projection area of <NUM><NUM>, and the effective thickness corresponding to the projection area is <NUM>.

After the iron-based alloy vascular stent of this embodiment is implanted into a body, when the incidence direction of the X-ray is approximately perpendicular to the coverage surface of the radiopaque object, the radiopaque object of the radiopaque structure has at least one group of projection area and effective thickness (Sm, dm)=(<NUM>, <NUM>), which accords with Sm-<NUM>(dm)-<NUM>=<NUM>, so that an obtained image basically may be identified with eyes, namely the radiopaque structure has good visibility.

An iron-based alloy vascular stent includes a radiopaque structure. The radiopaque structure only includes one radiopaque unit which includes four mutually spaced block-shaped radiopaque objects. The four mutually spaced radiopaque objects form an integral image under X-ray imaging equipment. The stent includes multiple mutually spaced waveform ring-like objects, and any two adjacent waveform ring-like objects are connected through a connection member. A hole is formed in the connection member which is located at the proximal end of the stent and is filled with the radiopaque structure. The four radiopaque objects are only made of gold and have a coverage area sum of <NUM><NUM> in the circumferential direction of the stent. Under irradiation of an X-ray with an incidence direction approximately perpendicular to the coverage surfaces of the radiopaque objects, the four radiopaque objects have a projection area of about <NUM><NUM>, and the effective thickness corresponding to the projection area is <NUM>.

After the iron-based alloy vascular stent of this embodiment is implanted into a body, when the incidence direction of the X-ray is approximately perpendicular to the coverage surfaces of the radiopaque objects, the four radiopaque objects of the radiopaque structure have at least one group of projection area and effective thickness (Sm, dm)=(<NUM>, <NUM>), which accords with Sm-<NUM>(dm)-<NUM>=<NUM>, so that an obtained image basically may be identified with eyes, namely the radiopaque structure has good visibility.

An iron-based alloy vascular stent includes a radiopaque structure. The radiopaque structure only includes one radiopaque unit which only includes an integral block-shaped radiopaque object. The stent includes multiple mutually spaced waveform ring-like objects, and any two adjacent waveform ring-like objects are connected through a connection member. A hole is formed in the connection member which is located at the proximal end of the stent, and is filled with the radiopaque object, thus the radiopaque structure is formed. The radiopaque object is only made of gold and has a coverage area of <NUM><NUM> in the circumferential direction of the stent. Under irradiation of an X-ray with an incidence direction approximately perpendicular to the coverage surface of the radiopaque object, the radiopaque object has a projection area of about <NUM><NUM>, and the effective thickness corresponding to the projection area is <NUM>.

A magnesium-based alloy vascular stent includes a radiopaque structure. The radiopaque structure only includes one radiopaque unit which only includes an integral block-shaped radiopaque object. The stent includes multiple mutually spaced waveform ring-like objects, and any two adjacent waveform ring-like objects are connected through a connection member. A hole is formed in the connection member which is located at the proximal end of the stent, and is filled with the radiopaque object, thus the radiopaque structure is formed. The radiopaque object is only made of gold and has a coverage area of <NUM><NUM> in the circumferential direction of the stent. Under irradiation of an X-ray with an incidence direction approximately perpendicular to the coverage surface of the radiopaque object, the radiopaque object has a projection area of about <NUM><NUM>, and the effective thickness corresponding to the projection area is <NUM>.

After the magnesium-based alloy vascular stent of this embodiment is implanted into the body, when the incidence direction of the X-ray is approximately perpendicular to the coverage surface of the radiopaque object, the radiopaque object of the radiopaque structure has at least one group of projection area and effective thickness (Sm, dm)=(<NUM>, <NUM>), which accords with Sm-<NUM>(dm)-<NUM>=<NUM>, so that an obtained image basically may be identified with eyes, namely the radiopaque structure has good visibility.

After the magnesium-based alloy vascular stent of this embodiment is implanted into a body, when the incidence direction of the X-ray is approximately perpendicular to the coverage surface of the radiopaque object, the radiopaque object of the radiopaque structure has at least one group of projection area and effective thickness (Sm, dm)=(<NUM>, <NUM>), which accords with Sm-<NUM>(dm)-<NUM>=<NUM>, so that an obtained image basically may be identified with eyes, namely the radiopaque structure has good visibility.

After the iron-based alloy vascular stent of this embodiment is implanted into a body, when the incidence direction of the X-ray is approximately perpendicular to the coverage surfaces of the radiopaque objects, the four radiopaque objects of the radiopaque structure have at least one group of projection area and effective thickness (Sm, dm)=(<NUM>, <NUM>), which accords with Sm-<NUM>(dm)-<NUM>><NUM>, so that an obtained image may be easily and clearly identified with eyes, namely the radiopaque structure has excellent visibility.

After the iron-based alloy vascular stent of this embodiment is implanted into a body, when the incidence direction of the X-ray is approximately perpendicular to the coverage surface of the radiopaque object, the radiopaque object of the radiopaque structure has at least one group of projection area and effective thickness (Sm, dm)=(<NUM>, <NUM>), which accords with Sm-<NUM>(dm)-<NUM>><NUM>, so that an obtained image may be easily and clearly identified with eyes, namely the radiopaque structure has excellent visibility.

An absorbable polymer-based vascular stent includes a radiopaque structure. The radiopaque structure only includes one radiopaque unit which only includes an integral block-shaped radiopaque object. The stent includes multiple mutually spaced waveform ring-like objects, and any two adjacent waveform ring-like objects are connected through a connection member. A hole is formed in the connection member which is located at the proximal end of the stent, and is filled with the radiopaque object, thus the radiopaque structure is formed. The radiopaque object is only made of gold and has a coverage area of <NUM><NUM> in the circumferential direction of the stent. Under irradiation of an X-ray with an incidence direction approximately perpendicular to the coverage surface of the radiopaque object, the radiopaque object has a projection area of about <NUM><NUM>, and the effective thickness corresponding to the projection area is <NUM>.

After the absorbable polymer stent of this embodiment is implanted into a body, when the incidence direction of the X-ray is approximately perpendicular to the coverage surface of the radiopaque object, the radiopaque object of the radiopaque structure has at least one group of projection area and effective thickness (Sm, dm)=(<NUM>, <NUM>), which accords with Sm-<NUM>(dm)-<NUM>><NUM>, so that an obtained image may be easily and clearly identified with eyes, namely the radiopaque structure has excellent visibility.

An iron-based alloy vascular stent includes a radiopaque structure. The radiopaque structure only includes one radiopaque unit which includes four mutually spaced block-shaped radiopaque objects. The four mutually spaced radiopaque objects form an integral image under X-ray imaging equipment. The stent includes multiple mutually spaced waveform ring-like objects, and any two adjacent waveform ring-like objects are connected through a connection member. Four holes are formed in the connection member which is located at the proximal end of the stent and are respectively filled with the four radiopaque objects. The radiopaque objects are made of a mixture of gold powder and polylactic acid, wherein the volume fraction of gold is <NUM> percent. A total coverage area sum of the four radiopaque objects in the circumferential direction of the stent is <NUM><NUM>. Under irradiation of an X-ray with an incidence direction approximately perpendicular to the coverage surfaces of the radiopaque objects, the four radiopaque objects have a projection area of about <NUM><NUM>, and the average thickness of the radiopaque objects corresponding to the projection area is <NUM>, so that the effective thickness corresponding to the projection area is the product of the volume fraction of the gold and the average thickness of the radiopaque objects, and is <NUM>.

After the iron-based alloy vascular stent of this embodiment is implanted into a body, when the X-ray is entering from the direction approximately perpendicular to the coverage surfaces of the radiopaque objects, the four radiopaque objects of the radiopaque structure have at least one group of projection area and effective thickness (Sm, dm)=(<NUM>, <NUM>), which accords with Sm-<NUM>(dm)-<NUM>=<NUM>, so that an obtained image basically may be identified with eyes, namely the radiopaque structure has good visibility.

An absorbable iron-based alloy vascular stent includes a radiopaque structure. The radiopaque structure includes two radiopaque units which are disposed at the proximal end of the stent and are staggered from each other by <NUM> degrees along the circumferential direction of the stent. Each radiopaque unit only includes an integral radiopaque object. The stent includes multiple mutually spaced waveform ring-like objects, and any two adjacent waveform ring-like objects are connected through a connection member. A hole is formed in each of two connection members which are disposed at the proximal end of the stent and are staggered from each other by <NUM> degrees along the circumferential direction of the stent, and is filled with each radiopaque object, thus the radiopaque structure is formed. The radiopaque objects are only made of gold, and the radiopaque object of each radiopaque unit has a coverage area of <NUM><NUM> in the circumferential direction of the stent. Under irradiation of an X-ray with an incidence direction approximately perpendicular to the coverage surfaces of the radiopaque objects, the radiopaque objects of the two radiopaque units are completely overlapped, and have a projection area of about <NUM><NUM>, and the effective thickness corresponding to the projection area is <NUM>.

In this embodiment, when the X-ray is entering from the direction approximately perpendicular to the coverage surfaces of the radiopaque objects, the two radiopaque units have a radiopaque object overlapping region in the incidence direction of the X-ray; the two radiopaque objects of the radiopaque structure have at least one group of projection area and effective thickness (Sm, dm)=(<NUM>, <NUM>), which accords with Sm-<NUM>(dm)-<NUM>=<NUM>, so that an obtained image may be identified with eyes, namely the radiopaque structure has good visibility.

An iron-based alloy vascular stent includes a radiopaque structure. The radiopaque structure only includes one radiopaque unit which only includes an integral radiopaque object. The stent includes multiple mutually spaced waveform ring-like objects, and any two adjacent waveform ring-like objects are connected through a connection member. A hole is formed in the connection member which is located at the proximal end of the stent, and is filled with the radiopaque object, thus the radiopaque structure is formed. The radiopaque object is only made of gold and has a coverage area of <NUM><NUM> in the circumferential direction of the stent. Under irradiation of an X-ray with an incidence direction approximately perpendicular to the coverage surface of the radiopaque object, the radiopaque object has a projection area of <NUM><NUM>, and the effective thickness corresponding to the projection area is <NUM>.

With reference to <FIG>, an iron-based alloy vascular stent <NUM> includes multiple mutually spaced waveform ring-like objects <NUM>, and any two adjacent waveform ring-like objects are connected through a connection member (not marked in the figure). The iron-based alloy vascular stent <NUM> further includes a first radiopaque structure <NUM>, a second radiopaque structure <NUM> and a third radiopaque structure <NUM> which are disposed on the connection members.

The first radiopaque structure <NUM> only includes one radiopaque unit (not marked in the figure) which only includes an integral radiopaque object (not marked in the figure). A hole is formed in the connection member at the middle section of the stent <NUM> and is filled with the radiopaque object of the first radiopaque structure <NUM>, thus the first radiopaque structure <NUM> is formed. The radiopaque object is only made of gold and has a coverage area of <NUM><NUM> in the circumferential direction of the stent <NUM>. Under irradiation of an X-ray with an incidence direction approximately perpendicular to the coverage surface of the radiopaque object, the radiopaque object has a projection area of about <NUM><NUM>, and the effective thickness corresponding to the projection area is <NUM>.

The second radiopaque structure <NUM> only includes one radiopaque unit (not marked in the figure) which includes four mutually spaced block-shaped radiopaque objects <NUM>, <NUM>, <NUM> and <NUM>. The four mutually spaced radiopaque objects <NUM>, <NUM>, <NUM> and <NUM> form an integral image under X-ray imaging equipment. Four holes are formed in the connection member which is located at the proximal end of the stent <NUM> and are respectively filled with the four radiopaque objects <NUM>, <NUM>, <NUM> and <NUM>. The four radiopaque objects are only made of gold and have a coverage area sum of <NUM><NUM> in the circumferential direction of the stent. Under irradiation of an X-ray with an incidence direction approximately perpendicular to the coverage surfaces of the radiopaque objects, the radiopaque objects have a projection area of about <NUM><NUM>, and the effective thickness corresponding to the projection area is <NUM>.

The third radiopaque structure <NUM> is disposed at the distal end of the stent <NUM> and includes a first radiopaque unit <NUM> and a second radiopaque unit <NUM>. In this embodiment, the first radiopaque unit <NUM> and the second radiopaque unit <NUM> are staggered from each other by <NUM> degrees in the circumferential direction of the stent <NUM>. The first radiopaque unit <NUM> includes a first radiopaque object <NUM> and a second radiopaque object <NUM> which are spaced from each other; two holes are formed in the connection member which is located at the proximal end of the stent <NUM> and are respectively filled with the first radiopaque object <NUM> and a second radiopaque object <NUM>. The second radiopaque unit <NUM> includes a third radiopaque object <NUM> and a fourth radiopaque object <NUM> which are spaced from each other; two holes are formed in the connection member, which is staggered from the first radiopaque unit by <NUM> degrees, at the proximal end of the stent <NUM>, and are filled with the third radiopaque object <NUM> and the fourth radiopaque object <NUM> respectively. The first, second, third and fourth radiopaque objects <NUM>, <NUM>, <NUM> and <NUM> form an integral image under X-ray imaging equipment, and are only made of gold, and a coverage area sum of the first, second, third and fourth radiopaque objects <NUM>, <NUM>, <NUM> and <NUM> in the circumferential direction of the stent <NUM> is <NUM><NUM>. Under irradiation of an X-ray with an incidence direction approximately perpendicular to the coverage surfaces of the radiopaque objects, there is no overlapping region between the radiopaque objects of the first radiopaque unit <NUM> and the second radiopaque unit <NUM>; and the first, second, third and fourth radiopaque objects <NUM>, <NUM>, <NUM> and <NUM> have a projection area of about <NUM><NUM>, and the effective thickness corresponding to the projection area is <NUM>.

When the iron-based alloy vascular stent <NUM> of this embodiment is implanted into a body, and the incidence direction of the X-ray is approximately perpendicular to the coverage surface of the radiopaque object of the first radiopaque structure <NUM>, the radiopaque object of the first radiopaque structure <NUM> has at least one group of projection area and effective thickness (Sm, dm)=(<NUM>, <NUM>), which accords with Sm-<NUM>(dm)-<NUM>=<NUM>, so that an obtained image basically may be identified with eyes, namely the first radiopaque structure <NUM> has good visibility.

When the incidence direction of the X-ray is approximately perpendicular to the coverage surfaces of the radiopaque objects of the second radiopaque structure <NUM>, the four radiopaque objects <NUM>, <NUM>, <NUM> and <NUM> of the second radiopaque structure <NUM> have at least one group of projection area and effective thickness (Sm, dm)=(<NUM>, <NUM>), which accords with Sm-<NUM>(dm)-<NUM>=<NUM>, so that an obtained image basically may be identified with eyes, namely the second radiopaque structure <NUM> has good visibility.

When the incidence direction of the X-ray is approximately perpendicular to the coverage surfaces of the radiopaque objects of the third radiopaque structure <NUM>, the first, second, third and fourth radiopaque objects <NUM>, <NUM>, <NUM> and <NUM> of the third radiopaque structure <NUM> have at least one group of projection area and effective thickness (Sm, dm)=(<NUM>, <NUM>), which accords with Sm-<NUM>(dm)-<NUM>=<NUM>, so that an obtained image basically may be identified with eyes, namely the third radiopaque structure <NUM> has good visibility.

In this embodiment, the first radiopaque structure <NUM> and the first radiopaque unit <NUM> of the third radiopaque structure <NUM> are staggered from each other by <NUM> degrees in the circumferential direction of the stent <NUM>. Therefore, information such as an axial length or a rotating angle of the stent <NUM> may be calculated according to images displayed under the imaging equipment due to the cooperation of the first radiopaque structure <NUM>, the second radiopaque structure <NUM> and the third radiopaque structure <NUM>.

Claim 1:
A radiopaque structure (<NUM>, <NUM>, <NUM>) for use in an implantable medical device, comprising:
at least one radiopaque unit (<NUM>, <NUM>), wherein each radiopaque unit (<NUM>, <NUM>) includes at least one radiopaque object (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>,<NUM>) and
wherein in at least one incidence direction of a light source, the at least one radiopaque object (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) in the radiopaque unit (<NUM>, <NUM>) are divided into n regions according to the thickness in the incidence direction;
wherein a projection area Sm of m regions of the n regions and the effective thickness dm of the m regions accord with Sm-<NUM>(dm)a≥<NUM>, wherein a is more than or equal to -<NUM> and less than or equal to -<NUM>, and m is more than or equal to <NUM> and less than or equal to n and the projection area of m regions of n regions is defined by <MAT> and the effective thickness dm of the m regions is defined by <MAT>, and
wherein, in the incidence direction, the projection area Sm of the m regions of the n regions is less than or equal to <NUM><NUM> and the effective thickness dm of the m regions of the n regions ranges from <NUM> to <NUM>.