Patent Document

The present application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/632,263 filed on Jan. 23, 2012. 
    
    
     FIELD OF THE INVENTION 
     The invention is in the medical field, and is particularly useful in percutaneous procedures such as embolization. 
     BACKGROUND OF THE INVENTION 
     In certain medical procedures, such as blood vessel embolization, it is desired to inject particles into the body. The procedure is a minimally invasive alternative to surgery. The purpose of embolization is to prevent blood flow to an area of the body, which effectively can shrink a fibroid, such as a uterine fibroid. It can also shrink a tumour or block an aneurysm. It is typically done by injecting blocking particles into a blood vessel. 
     The procedure is carried out as an endovascular procedure by a radiologist in an interventional suite. It is common for most patients to have the treatment carried out with little or no sedation, although this depends largely on the organ to be embolized. 
     Access to the organ in question is acquired by means of a guidewire and catheter. The position of the correct artery or vein supplying the undesired tissue in question is located by X-Ray images. These images are then used as a map for the radiologist to gain access to the correct vessel by selecting an appropriate catheter and or wire, depending on the shape of the surrounding anatomy 
     The blocking particles are mixed into a saline solution, sometimes a contrast agent is added (to make the solution opaque to X-Rays). The blocking particles have to be of certain sizes, typically between 0.1 mm to 1 mm, in order to block the blood vessel at the right diameter. Such particles tend to settle very quickly out of the solution as they are heavier than water, causing an uneven concentration of particles during the injection. The settling occurs in as little as a few seconds. It is inconvenient to keep shaking the syringe used for injection, as the whole process is performed in a few seconds and the doctor has to concentrate on injecting the correct amount. It is desired to have a syringe that can keep the particles uniformly dispersed in the saline solution regardless of delays in the injection process or speed of the injection. Since the syringes used are low cost disposable items, it is desired that the device used to keep the particles uniformly dispersed will also be very low cost and disposable. The ideal mixing syringe needs the following attributes: 
     A. Ability to be re-filled multiple times during a procedure. This rules out any single-use designs, typically using the rupturing of a membrane to allow mixing. 
     B. Generate a strong mixing action, preferable by creating a vortex in the mixture. 
     C. Use the minimum modification to a standard syringe. 
     Prior art mixing syringes, such as disclosed in U.S. Pat. No. 7,883,490 are designed to mix together two materials stored separately in two compartments. They are not designed to stir up a pre-mixed solution. Prior art syringes designed to stir-up embolization mixtures, such as disclosed in US2009/0247985, are needlessly complex. Also, many of the prior art mixing syringes are not designed to be filled with the pre-mixed solution just before use. This is required during embolization, as the correct volume and ratio of saline, particles and contrast agent has to be customized to the procedure by the doctor. The current invention acts as a regular syringe, allowing filling and injecting at any time, but it keeps the solution stirred up during injection. Similar to a regular syringe, it can be re-used several times during a procedure, if more particles have to be injected. The invention can be manufactured out of a regular syringe, which is a very low cost item. 
     SUMMARY OF THE INVENTION 
     A movable mixing disc is inserted into a regular syringe. The mixing disc has a small hole covered by a fine screen, allowing only saline solution to get behind disc. When the plunger of the syringe is pressed, the saline solution emerges from the mixing disc hole as a high velocity jet, stirring up the settled particles. As the ejection continues, the mixing disc is pushed forward by the plunger in order to eliminate any unused volume. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a general view of the invention. 
         FIG. 2A  shows a cross section of the mixing disc. 
         FIG. 2B  shows a front view of the mixing disc of  FIG. 2A . 
         FIG. 3  shows the action of the mixing disc. 
         FIG. 4A  is a cross section of a mixing disc stamped out of sheet metal. 
         FIG. 4B  is a front view of the mixing disc of  FIG. 4A . 
         FIG. 5  shows a version of the invention not requiring modifications to the syringe. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIG. 1 , the mixing syringe is a regular syringe with the addition of a mixing disc. A syringe  1  includes a plunger  2  and a seal  3  in order to eject the liquid  6  via tube  4 . A piston-like mixing disc  5   a  is added into the syringe. The initial position of disc  5   a  is shown as  5   a ′, with plunger seal  3  touching disc  5   a . As liquid and particles are sucked into syringe  1 , seal  3  moves farther from disc  5   a  to create a vacuum. Disc  5   a  moves as well, until stopped by slight ridge  8 . The size of the ridge is exaggerated in  FIG. 1  for clarity. It only needs to reduce the inside diameter by about 0.2-0.3 mm. Flexible seal  3  easily passes over such a ridge. The particles  7  are sucked into the syringe via tube  4  and quickly settle as shown in  FIG. 1 . The particles do not accumulate in the section between plunger seal  3  and disc  5   a  as disc  5   a  includes a filter with pore sizes smaller than the particles. This is shown in  FIGS. 2A and 2B . Disc  5   a  has one or more holes  9  covered by filter mesh  10 . It is desired to chamfer hole  9  under screen  10  to increase the effective area of the screen. The screen can also be mounted as a flexible flap, being pushed out of the way during ejection of the fluid. The conical shape of disc  5   a  is matched to the shape of the conical seal  3  and the conical tip of the syringe. This eliminates trapped fluid between the seal  3  and the syringe outlet at the end of the stroke. The conical shape of disc  5   a  also aids the removal of any trapped air bubbles, as they float to the top of disc  5   a  and escape when syringe is held vertically. As plunger  3  is moved towards disc  5   a  the liquid  6  is ejected via hole  9  at a high velocity, mixing up particles  7  and liquid  6 . This is shown in  FIG. 3 . 
     From the moment seal  3  touches disc  8  the disc is pushed forward towards the tube  4  until the syringe is empty and disc  5   a  is in position  5   a ′. The operation can now be repeated, if desired. 
     It is desirable to make hole  9  at an angle to the axis of the syringe in order to create a vortex  111 . An even more effective vortex  111  can be created if hole  9  is molded as a curved arc, both in the plane of the drawing and also in the plane perpendicular to the drawing. 
     Disc  5   a  can be molded in one piece, including screen  10 . Alternatively, screen  10  can be bonded to molded disc  5   a . The fit between disc  5   a  and bore of syringe  1  is not critical as the particles are relatively large. It was found out that for best results the diameter of disc  5   a  should be 0.1-0.2 mm smaller than the inside diameter of syringe  1 . 
     While the example given is for embolization, the invention can be used to mix and two components, including two liquids. 
     The disc  5  can also be made out of pressed sheet metal  11 . This is shown as disc  5   b  in  FIGS. 4A and 4B . In this case hole  9  and screen  10  are replaced by miniature stamped louvers  12  (similar to a miniature venetian blind) acting both as a screen and as a flow director. Recommended material is type 316L stainless steel or aluminum, with thickness between 0.1 to 0.3 mm. The thin wall allows seal  3  to enter into the hollow disc and squeeze out all the liquid. 
     In order to eliminate the need of molding custom syringes it was found out that the slight ridge  8  can be formed in existing syringes by briefly heating up the area of ridge  8  and pressing the walls in slightly, using a split ring slightly smaller than the outside diameter of the syringe. Other ways of creating a ridge without molding is pressing into the syringe a thin walled ring, held by friction. 
     If desired the invention can be manufactured out of a standard disposable syringe, without any modifications. The movable disc  5   a  is attached to the outlet side of the syringe with a short string that only allows it to move a limited distance. The string  13  is bonded by heat to the syringe or uses an anchor  14 . This is shown in  FIG. 5 . 
     In operation tube  4  is first inserted into a mixing bowl where the ingredients are mixed together. The mixture is sucked into the syringe. After filling the syringe is held vertically to help trapped air escape and plunger moved to expel all air. Afterwards tube  4  is moved to the catheter or needle used for the procedure and mixture is injected. 
     An additional improvement in mixing is to adjust the density of particles  7  to match the density of liquid  6 , typically a saline solution with a density around  1 . since the materials used to make particles  7  (plastic, glass or ceramic) have a density greater than  1 , they have to be made hollow. The technology of manufacturing small hollow spheres, known as micro-balloons, is well known and many polymers as well as glasses are commercially available in micro-balloon form. One supplier is Henkel (http://www.henkelna.com/cps/rde/xchg/henkel_us/hs.xsl/brands-1556.htm?iname=Dualite%25C2%25AE&amp;countryCode=us&amp;BU=industrial&amp;parentredDotUID=0000000GFR&amp;redDotUID=0000000GFR&amp;brand=000000QTQE 
     Both ideas can be combined: micro-balloon shaped polymer or glass spheres with a density around  1  can be dispensed from a syringe with a mixing disc.

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