WO1996023537A1

WO1996023537A1 - A piston extender for use with automatic injection machines

Info

Publication number: WO1996023537A1
Application number: PCT/US1996/000674
Authority: WO
Inventors: Reinhard Muller-Spath
Original assignee: Mallinckrodt Medical, Inc.
Priority date: 1995-01-30
Filing date: 1996-01-22
Publication date: 1996-08-08

Abstract

The present invention relates to piston extenders (60) to be used in conjunction with machines for automatic injection of solutions, such as parenteral solutions, e.g., X-ray contrast media. In particular, the present invention relates to a piston extender (60) of piston holder (50) which does not positively connect with the piston (30) of a syringe, and therefore cannot be used to retract the piston (30).

Description

A PISTON EXTENDER FOR USE WITH AUTOMATIC ---N-JECTION MACHINES

Background

The present invention relates to piston extenders to be used in conjunction with machines for automatic injection of solutions, such as parenteral solutions, e.g. X-ray contrast media.

Automatic injection machines are used for intravascular injection of parenteral solutions, such as X-ray contrast media, in several procedures, including phlebography, i.e. X-ray photography of leg veins for diagnosing thrombosis, and computer tomography. Normally, these procedures require the injection of relatively large volumes of contrast media, e.g. in the range of about 100 to 200 ml. The delivery of the contrast media may be controlled by machine settings so that a wide variety of desired injection profiles can be obtained with a high degree of accuracy, and in a simple manner, while meeting the particular medical requirements. In addition, the various injection profiles can be stored and are therefore always available for further inspection and for future investigations.

For example, injection machines can generally deliver parenteral solution at rates from 0.1 to 9.9 ml/s, selectable in 0.1 ml/s steps, and total injected volume of about 100 to 200 ml, selectable in 1 ml steps. The injection of these large volumes is carried out at relatively high pressure, in the range of several bars to several tens of bars, the pressure being electronically controlled and limited for safety reasons.

Syringes which contain large volumes between 100 and 200 ml are generally known in clinical terminology as "high-pressure syringes" because of the relatively high pressure used for injection.

It is sometimes desirable to inject smaller amounts of

SUBSTITUTESHEET(RI/LE26) solutions for various procedures. In some cases, conventional manual syringes, having normal volume capacities in the range from 1 to 100 ml may be used in conjunction with a conversion kit which allows manual syringes to be used with an injection machine designed for high pressure syringes. Such a conversion kit is described in co-pending European Patent Application 94101290.8, hereby incorporated by reference, and further described below.

The conversion kit enables automatic injection machines designed for high-pressure syringes to be used for injection from manual syringes, and includes at least one conversion vessel, having a receiving head with a radial recess including a first region for substantially non-rotary reception of the peripheral edge projecting from the distal end of a high-pressure syringe and also including a second region for receiving the radial end regions of the wings of a manual injection syringe of predetermined size. The conversion kit also includes at least one reducing sleeve for reducing the effective inner diameter of the cylindrical guide of the conversion vessel, comprising a substantially cylindrical sleeve member, having an outer diameter which will fit snugly within the inner diameter of the cylindrical guide and having an inner diameter which will snugly receive the outer diameter of the manual syringe, and a peripheral edge projecting radially from the distal end of the reducing sleeve and adapted to be received in the first region of the radial recess in the receiving head, and in which the peripheral edge of the distal end of the manual syringe can be received. In addition the conversion kit includes at least one conversion piston holder, having a radial maximum diameter equal to or less than the diameter of the piston of the manual syringe, and equipped with a means for releasably securing the piston holder to the free end of the spindle of the injection machine and equipped with a head for coupling the piston holder to the piston of a high-pressure syringe and for applying pressure to the piston of the manual syringe. In many cases, injection machines are used to both fill and dispense solutions to and from syringes. In particular, syringes may be filled in accordance with the following general procedure. First, an empty syringe is installed within the injection machine. The spindle of the injection machine is then attached to the piston of the syringe via a piston holder which is also attached to the spindle. The spindle is then extended to push the piston to the distal end of the syringe. The tip of the syringe is then contacted with a desired solution, either directly or through a filling means, such as a fill tube. The spindle is then retracted, thus pulling the piston toward the proximal end of the syringe and filling the syringe with the solution by the suction created. Once filled, the solution source is removed from the tip of the syringe. Prior to connecting the syringe to the delivery means needed for injection, the spindle may be extended a short distance to assure the elimination of air bubbles from the syringe chamber.

In order to fill the syringe in this manner, it is necessary to have a positive connection between the spindle and the piston, so that both extension and retraction can be accomplished.

Coππon connections known in the prior art are shown in Figs. 1 and 2, as described below.

Fig. 1A is a cross-section view of a piston, generally designated by reference numeral 10, and a piston holder, generally designated by reference numeral 20, for a standard high-pressure syringe as known in the prior art. In particular, piston 10, includes a main body 12, adapted to fit snugly within the chamber of a syringe, and a connection peg 14, connected to the main body 12, by a stem 16. The piston holder 20, includes a main body 22, and a peg slot 24, in open connection with a stem slot 26. The piston holder 20, also includes suitable means (not shown) for connection to the spindle of the injection machine. The peg slot 24, and stem slot 26, are constructed so as to loosely receive the peg 14, and stem 16, of the piston 10, when connected together as shown in Fig. IB. Fig. 1C is bottom view of the piston holder 20 showing the stem slot 26, having a key shaped opening. A first portion 27, of stem slot 26, is dimensioned to allow the peg 14, of the piston 10, to fit through and be received in the peg slot 24. A second portion 28, of stem slot 26, dimensioned to fit around the stem 16, of piston 10, and to hold the peg 14, within the peg slot 24.

Once the piston 10, and piston holder 20, are connected together as shown in Fig. IB, the piston holder 20, coacts positively with the piston 10, so that when the piston holder 20, is retracted or extended, by action of the spindle, the piston

10, is moved in the same manner.

Fig. 2A is a cross-section view of a piston, generally designated by reference numeral 30, and a piston holder, generally designated by reference numeral 40, for a standard manual syringe as known in the prior art. In particular, piston 30, includes a main body 32, adapted to fit snugly within the c±iamber of a syringe, and a screw threaded cavity 34, formed within the main body 32. The piston holder 40, includes a main body 42, and a screw threaded extension 44. The piston holder 40, also includes suitable means (not shown) for connection to the spindle of the injection machine. The screw threaded extension 44, and screw threaded cavity 34, are constructed so as to positively coact when the piston 30, and piston holder 40, are connected together as shown in Fig. 2B. When the piston 30, and piston holder 40, are connected together as shown in Fig. IB, the piston holder 40, coacts positively with the piston 30, so that when the piston holder 40, is retracted or extended, by action of the spindle, the piston 30, is moved in the same manner.

One disadvantage of filling syringes using the injection machine, is that the positive connection between the piston and piston holder is necessary. In particular, with the positive connection, any time the spindle of the injection machine is retracted, the piston of the syringe is also retracted. This is true even in the event the spindle is retracted by mistake. This can be extremely disadvantageous in several circumstances. For example, retraction of the spindle after filling of the syringe can draw air into the syringe chamber, requiring the syringe to once again by purged of air prior to injection. In addition, if the spindle is retracted while the syringe is still connected to the patient, the result may be extraction of blood, etc, from and possible damage to the arterial system of the patient. Obviously, this is very dangerous and should be avoided.

The use of pre-filled syringes has helped to avoid the need to fill syringes using the injection machine. However, pre- filled syringes usually have the same piston configurations as those shown in Figs. 1 and 2. Therefore, the disadvantages noted above still exist.

It is also often desirable to inject smaller amounts of solutions from either high-pressure syringes or from manual syringes. This is often accomplished by under filling the syringe. For example, a 100 mL syringe may be filled with only

50 mL of solution. This adds other disadvantages to the possible retraction of the piston. In particular, the exposed portion of the interior of the chamber of the pre-filled syringe may not be sterile, especially upon exposure to the ambient conditions upon connection of the syringe to the injection machine.

Consequently, -retraction of the piston can pull the piston into the unsterilized area creating a serious risk of contamination of the solution within the pre-filled syringe.

Therefore, there remains a need in the art for iπprovements in this field and particularly for improvements to piston holders for use with injection machines.

Objects Of The Invention

It is one object of the present invention to provide a piston extender or piston holder for an automatic injection machine, which can be used to push a piston of a high-pressure syringe, but can not retract the piston.

It is further object of the present invention to provide a piston extender or piston holder for an automatic injection machine, which can be used to push a piston of a manual syringe, but can not retract the piston.

Sumnary Of The Invention

The above objects and others can be accomplished according to the present invention by providing a piston extender or piston holder which does not positively connect with the piston of the syringe. The piston extender or piston holder of the present invention can have several configurations as will be explained in greater detail below.

Brief Description Of The Drawings

Fig. 1A is a cross-section view of a piston and a piston holder for a standard high-pressure syringe as known in the prior art.

Fig. IB is a cross-section view of the piston and the piston holder shown in Fig. 1A shown connected together.

Fig. 1C is a bottom view of the piston holder shown in Fig. 1A. Fig. 2A is a cross-section view of a piston and a piston holder for a standard manual syringe as known in the prior art.

Fig. 2B is a cross-section view of the piston and the piston holder shown in Fig. 2A shown connected together.

Fig. 3 is a cross-section view of a piston extender for a manual syringe according to one embodiment of the present invention.

Fig. 4 is a cross-section view of a piston extender for a high-pressure syringe according to another embodiment of the present invention.

Detailed Description Of The Invention

Fig. 3 is a cross-section view of a piston extender, generally designated by reference numeral 50, for a manual syringe according to one embodiment of the present invention. In particular, piston extender 50, includes a main body 52, and a peg extension 54. The peg 54, has a smooth exterior surface and is sized to fit loosely within the screw threaded cavity of a manual syringe piston. Therefore, the piston extender 50, can be used to push the piston, but does not positively connect to the piston, making retraction of the piston impossible.

The piston extender 50, can be made in several different configurations. In particular, the piston extender 50, can be adapted to connect with the piston holder of the injection machine. This connection can be of any suitable means such as the connections shown between the pistons andpiston holders in Figs. 1 or 2. Alternatively, the piston extender 50, can include means for direct connection to the spindle of the injection machine and thereby take the place of the original piston holder. The piston holder 50, can be made in several different lengths to accσrπrodate different sized syringes. A longer piston holder 50, can be particularly useful when being used with an under filled syringe, as the piston holder 50, can fill the exposed interior portion of the syringe chamber. The piston holder 50, may also be made is a wide variety of diameters for use with any number of different sized syringes.

Fig. 4 is a cross-section view of a piston extender, generally designated by reference numeral 60, for a high-pressure syringe according to further embodiment of the present invention. In particular, piston extender 60, includes a main body 62, and a hollow portion 64. The hollow portion 64, has a smooth interior and is sized to fit loosely around the peg and stem of a high-pressure syringe piston. Therefore, the piston extender 60, can be used to push the piston, but does not positively connect to the piston, making retraction of the piston impossible.

The piston extender 60, can also be made in several different configuration. In particular, the piston extender 60, can be adapted to connect with the piston holder of the injection machine. This connection can be of any suitable means such as the connections shownbetween the pistons andpiston holders in Figs. 1 or 2. Alternatively, the piston extender 60, can include means for direct connection to the spindle of the injection machine and thereby take the place of the original piston holder. The piston holder 60, may also be made is a wide variety of diameters for use with any number of different sized syringes.

The piston holder 60, can be made in several different lengths to accommodate different sized syringes. A longer piston holder 60, can be particularly useful when being used with an under filled syringe, as the piston holder 60, can fill the exposed interior portion of the syringe chamber. As will be evident from the above description, the piston extenders according to the present invention overcome all of the disadvantages of having a piston holder which positively connects with the piston of a syringe. In particular, the piston extenders of the present invention enable injection to be carried out by pushing of the piston, but make retraction of the syringe impossible. Therefore, air can not be drawn into the chamber of the syringe by mistakenly retracting the piston. Further, retraction of the piston while still connected to the patient is not possible, thus avoiding possible damage to the patient. Finally, possible contamination of the solution within the syringe is avoided because the piston can not be retracted into the unfilled interior portion of the syringe chamber.

The foregoing has been a description of certain preferred embodiments of the present invention, but is not intended to limit the invention in any way. Rather, many modifications, variations and changes in details may be made within the scope of the present invention.

Claims

What is claimed is:

1. A piston extender for an automatic injection machine, comprising a body portion adapted to fit within the chamber of a syringe to be used in conjunction with said injection machine; means to connect said piston holder to a spindle of said injection machine; and means to engage a piston of said syringe, wherein engaging means can push said piston but cannot retract said piston.

2. A piston extender according to claim 1, wherein said engaging means comprises a peg extension on said body portion, said peg extension adapted to fit loosely within a screw threaded cavity of said piston.

3. A piston extender according to claim 1, wherein said engaging means coπprises a hollow portion within said body portion, said hollow portion adapted to loosely receive a peg and stem extension of said piston.

4. A piston extender according to claim 1, wherein said connection means comprises means for direct attachment to said spindle.

5. A piston extender according to claim 1, wherein said connection means comprises means for attachment to a piston holder of said injection machine.