Automatic liquid injection system and method   

Abstract: A power assisted method and injector device for controllably delivering to patients a dispersion medicament or diagnostically active agent, the homogeneity of which is preserved throughout delivery. Diagnostically active agents disclosed are gas microbubble suspensions useful in ultrasonic diagnostic imaging and liposomal formulations in which liposome vesicles are loaded with iodinated compounds.

FIELD OF THE INVENTION

The present invention concerns the administration by injection to patients of liquid compositions for therapeutic or diagnostic purposes. It more particularly concerns a power assisted method and device for controllably dispensing a liquid medicament or diagnostically active contrast agent, the homogeneity of which is preserved throughout delivery. Typically, the contrast agent is an aqueous suspension of gas filled microvesicles, namely microbubbles bounded by a surfactant stabilized gas/liquid interface, or microballoons bounded by a tangible material envelope.

BACKGROUND ART

Power injectors and mechanically assisted infusion systems for controllably dispensing therapeutically active medications are well known in the art. Typically, such devices include an automatic injector for syringes containing an injectable liquid and a plunger or piston movable within the barrel of the syringe to expel said liquid through a tip thereof and injecting into a patient via a tubing connected to an injecting needle or catheter. For controlling the injections parameters, the plunger is driven by means of an electromechanical arrangement organised to push the plunger at a desired rate, continuously or at chosen intervals, so that the amount of medication is delivered to the patient\'s body under strictly determined conditions. For instance, in the case of intravenous dispensing contrast agent formulations for diagnostic purposes (X-ray, MRI or ultrasound), the rate and the mode of injection can be accurately controlled to match the requirements of the imaging methods and detector systems used to investigate the circulation or a specific organ in the body. Typical automated injection devices are illustrated and described in U.S. Pat. No. 5,176,646 incorporated herein by reference.

Although the automated injectors known are highly sophisticated instruments capable of mastering most injection problems experienced in practice, there remains at least one variable factor not yet under control. Indeed the known power injectors have no control of the homogeneity of the liquid stored within the syringe barrel during the course of its application. This kind of problem is of course non-existent with “true solutions” (i.e. solutions to the molecular level) since in this case no concentration change can occur in the course of time; it however may become important when the injectable formulation is a suspension or dispersion of active particles which tend to settle, coalesce or segregate with time in the syringe. Indeed, even some modest separation of the particles by gravity or otherwise from the carrier liquid in the course of administration of the formulation may have very important influence on reproducibility and reliability of the tests. Hence, in this case, a method and means to keep the syringe content homogeneous during injection is highly desirable. The present method and device constitute a very effective solution to the aforediscussed problem.

SUMMARY

Briefly stated, in order to secure homogeneity of a liquid suspension of particles within the barrel of an injector device, the invention provides a method and means whereby the particles are kept under sufficient agitation so as not to settle, segregate or agglomerate in the carrier liquid. This may involve acting on the carrier liquid itself, i.e. on the bulk of the suspension, or may involve acting only on the particles (in this case, one would expect the moving particles to impart motion to the carrier liquid by viscous friction). The agitation means may be provided within the syringe or in some cases outside thereof; for instance with magnetic particles, the particles can be subjected to an external variable magnetic field, the oscillation or rotation of which will set them into motion, the moving particles then acting on the carrier liquid and keeping the suspension homogeneous.

In the case of particles not sensitive to external fields, mechanical agitation is provided to the extent that it is sufficient to keep the suspension homogeneous but insufficient to break or damage the particles or disturb their distribution. For this, the syringe barrel may be subjected to motion, said motion being continuous or discontinuous, regular or irregular; the motion can possibly have a shaking, rocking or oscillating effect on the syringe. The frequency, intensity and rate of the motion is such that it will not interfere with the control of delivery parameters of the suspension.

The embodiments disclosed below in connection with the annexed drawings provides very effective means to keep the syringe content under sufficient agitation to secure injection of a homogeneous therapeutic or diagnostic liquid compositions into a patient.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view in perspective of a device for agitating a liquid within the syringe of a power driven automatic injector system of the invention.

FIG. 2 is a graph illustrating the homogeneity variations in a suspension of microbubbles contained in a syringe, the latter being either still or subjected to motion according to the invention.

FIG. 3 is a graph illustrating the gas volume and in vitro intensity of samples with and without treatment according to the invention.

FIG. 4a is a schematic view in perspective of another device for agitating a liquid within the syringe of a power driven automatic injector system of the invention. In this embodiment, the syringe is held by a supporting bracket, the latter being driven into motion by a motor.

FIG. 4b is a schematical sectional view of the motor driving means of the embodiment of FIG. 4a.

DETAILED DESCRIPTION

The device represented schematically in FIG. 1 comprises a series of co-operating elements mounted on a board 1. Such schematic representation of the present device is only for clarity and better understanding of the device\'s operation. Obviously, in its actual commercial construction, the device is in the form of a much more compact and sophisticated apparatus, for instance in the form of an instrument like the Perfusor® fm of the Firm BRAUN Meslungen AG, D-34209, Meslungen, Germany (displayed in Publication B.03.01.95 No 0879 0744), or like the apparatuses disclosed in U.S. Pat. No. 4,652,260 and U.S. Pat. No. 5,176,502, both being incorporated herein by reference.

The present device comprises the following working components: a syringe 2 shown in an uplifted position, an automatic power driving unit 3 for acting on the syringe, a pair of syringe motioning units 4 for liquid agitation, and a control box 14 for controlling operation of the units 4.

The syringe 2 has a barrel 5, a plunger 6 sliding in the barrel and a tip connector 7 linked to a tubing 8, the latter leading to an injection needle 9. The needle 9 is for injecting an administrable liquid into the tissues or the circulation of a patient.

The power driving unit 3 has an electromechanically controlled pusher rod 10 for acting on the rear end 11 of the syringe plunger, and a control knob 12 for setting the automatic driving parameters that will rule the action of the rod 10.

Each unit 4 is equipped with two rollers 13, themselves driven into rotation by electric motors within the units and not represented in the drawing. The rotation of the rollers 13 is governed by means of a box 14 via lead wires 15 connected to said motors.

In operation, an injectable carrier liquid with particles (e.g. gas-filled microballoons) in suspension is introduced into the barrel 5 of the syringe 2 through the tip 7, this being consecutive to the retraction (manual or mechanical) of the plunger 6, so that an adequate pumping action is provided. Then the syringe is placed on the rollers 13, so that the flange 16 thereof abuts the roller\'s edge 17, this being for retaining the syringe in its relative position against unwanted longitudinal translation. In this situation, the pushing rod 10 of the driving unit 3 couples with the plunger\'s end 11, so that any forward displacement of the rod 10 is transferred to the plunger with consequent expelling of the liquid toward the needle 9 for injection.

During injection, the rollers will alternately rotate the syringe a certain angle in one direction, say 30°, 60°, 90°, 180°, 270° or 360° and then, reciprocably, in the opposite direction. This balancing motion, which may be carried out in a stepwise manner, will move the liquid carrier to such an extent that any separation or segregation of the particles is hindered. This is very efficient for instance in the case of suspensions of gas-filled microbubbles used in echography since there is always a bubble size distribution in such suspensions, the larger bubbles tending to rise faster than the smaller ones by buoyancy. In a variant, the syringe can be made to rotate in one direction only, provided that the connector tip 7 thereof is made to freely rotate in order to prevent distortion of the tubing 8. Normally, the rate of rotation impressed by the rollers 13 is from about 0.5 to 200 rpm depending upon the suspension viscosity. This rate should be sufficient to keep the particles in homogeneous suspension but insufficient to break the particles or disturb their distribution in the carrier liquid. If necessary, in the case of more viscous suspensions, an additional vibrational motion of a few Hz to a few hundreds of Hz can be applied to the syringe by means of a pitch-fork or pitch-pipe. It should be mentioned that at very high rotation rates (e.g. 1,000 rpm or more) the radial speed may become dominant which will result in axial concentration of the microbubbles in the middle of the syringe. Rotational speeds at which the radial component becomes important are to be avoided as under such conditions the suspension will become non-homogeneous again. This is clearly undesired.

In a variant, the unit 4 can have the form of a closable housing equipped with fixed syringe retaining means, i.e. other than the rollers edges 17 and, possibly if required, pressure resisting means (like a pressure mantle or jacket) in case the suspension is viscous and exerts undue pressure efforts to the syringe barrel. Also the syringe components can be made of moulded plastic (disposable syringes) and the barrel external surface provided with an integrally moulded relief pattern mating with corresponding pattern on the roller\'s surface, so that positive grip drive of the syringe is ensured.

Also, the rod 10 and the plunger 6 can be made integral with each other so that filling of the syringe can be controlled by the power unit 3, the pumping action then resulting from a backward displacement of rod 10.

The power unit per se is standard and its nature and operation well known to the skilled person. Embodiments thereof are disclosed in the cited references and also in U.S. Pat. No. 5,456,670. The power unit usually contains an electrically powered and controlled helical screw means for mechanically advancing or retracting rod 10 continuously or intermittently, so that the liquid in the syringe can be dispensed continuously or by increments. The various parameters ruling said motions of the syringe piston can be monitored and adjusted by the control 12 and possible other control means not represented in the drawing. Means of unit 3 also ensure that such delivery parameters can be monitored and recorded for display. An instant stop switch (not shown) may also exist, in case the operation of the system should be suddenly interrupted due to a problem with the patient or otherwise.

It should be incidentally noted that although the present embodiment involves rocking the syringe only, one may also consider a modification involving a back and forth rotation of the pumping ensemble, this being achieved by well known mechanical means adapted to support said pumping ensemble and to impart motion thereto.

Furthermore, although the present embodiment involves motion around the longitudinal axis, a variant may include rocking the syringe about a transversal axis.

A second device embodiment illustrated schematically in FIGS. 4a and 4b comprises a syringe 22 with a barrel 25 supported in a rotatable fashion by a bracket 30a-30b and a plunger 26 sliding in the barrel whose displacement therein is controlled by a power driven unit 23 capable of moving forward and backward in engagement with the back pusher end of the plunger 26. The device also comprises a motor driven unit 24 encompassing a portion 30b of the supporting bracket, the latter being rotated through gears 31, as better shown on FIG. 4b, for agitation of a liquid suspension in the syringe barrel. The longitudinal forward or backward displacement of the unit 23 (acting on the plunger 26) is effected via a motor 31 which rotates a screw-bar 32, the latter engaging with a matching threaded portion (not shown) within the unit 23. The device further comprises an electronically computerized control box 34 for controlling operation of the units 23 (via motor 31) and 24, and for processing the signals from a laser detector 35 designed to read an identifying mark 36 on the syringe; this mark is for preventing errors in the selection of the syringe, especially if the syringe is of the prefilled type. The code of the mark can be according to standard bar codes. Note in this regard that since the syringe barrel is set into rotation in the present device, one can use a fixed detector instead of a mobile one which is advantageous designwise. By counting and recording via box 24 the number of turns of the screw bar 32, the position of the unit 23 (and consequently of the plunger 26) can be monitored and regulated at will. The control box 34 can of course comprise further monitoring and visualizing means (not shown) to optically display and appropriately regulate the various parameters involved in operation of the device. As in the previous embodiment, the syringe has a tip 27 for connecting to a liquid dispensing tubing 28, the latter leading to means for injecting an administrable liquid into a patient.

The operation of the present device is very similar to that of the earlier embodiment and hence needs not be discussed further at length. Suffice to say that it may also comprise security means intended to automatically interrupt the operation in case troubles develop with the patient or otherwise during injection. For instance, the pressure in the syringe barrel can be monitored by registering the force required to push the plunger, this being via the power absorbed by the driving motor 31. A sudden surge, for instance a rapid increase of current in said motor can trigger via the control unit 34 an emergency stop of the device. Alternatively, this effect could also be detected according to usual means by a strain gauge installed in the drive 23.

As already said, the particles of the suspensions in this invention may be of various kinds and involve for instance microspheres containing entrapped air or other gases used in echography. These microspheres may be bounded by a liquid/gas interface (microbubbles), or they may have a tangible membrane envelope of for instance synthetic polylactides or natural polymer like denatured protein such as albumin (microballoons). The carrier liquid for the microbubble suspensions comprises surfactants, preferably saturated phospholipids in laminar or lamellar form such as diacylphosphatidyl derivatives in which the acyl group is a C16 or higher fatty acid residue.

The gases used in the microbubbles or microballoons are pure gases or gas mixtures including at least one physiologically acceptable halogenated gas. This halogenated gas is preferably selected among CF4, C2F6, C3F8, C4F8, C4F10, C5F12, C6F14 or SF6. The gas mixtures can also contain gases such as air, oxygen, nitrogen, helium, xenon or carbon dioxide. In fact in a number of cases microbubbles or microballoons will contain mixtures of nitrogen or air with at least one perfluorinated gas in proportions which may vary between 1 and 99%.

In the microballoons the membrane is made from a biodegradable material such as biodegradable polymers, solid triglycerides or proteins and are preferably selected from the polymers of polylactic or polyglycolic acid and their copolymers, denatured serum albumin, denatured haemoglobin, lower alkyl polycyanoacrylates, and esters of polyglutamic and polyaspartic acid, tripalmitin or tristearin, etc. In an embodiment, the microballoons are filled with C3F8 and the material envelope is made of albumin.

Homogeneity of suspensions of microballoons whose membrane is made of saturated triglycerides such as tripalmitin, trimyristin or tristearin and their mixtures with other tri- or di-glycerides, fatty acids or polymers is particularly interesting as those are used for delivering active ingredients to specific sites within the body. Homogeneity of suspensions of such microballoons has been effectively maintained using the method and the device of the invention.

Other particles whose density is different from that of the carrier liquid may include liposomes filled with iodinated X-ray opacifiers such as iomeprol, iopamidol, iopentol, iohexyl, metrizamide, iopromide, iogulamide, iosimide or ioversol or, for instance, coated and uncoated magnetic particles which tend to precipitate in saline or other carriers.

The present injector system can be used in imaging organs, blood vessels and tissues of mammalians, e.g. the ultrasonic imaging of the heart, the liver or spleen, the brain, the kidneys, the blood vessels, etc.

The invention is further illustrated by the following Examples.

A solution of gas filled microbubbles stabilised by a phospholipids interface was prepared according to Example 1 of U.S. Pat. No. 5,445,813. The dry matter concentration was 5 mg/ml in a saline solution (0.9% NaCl). Typically, the bubble size distribution extended from 0.2 to 15 μm. The concentration of bubbles between 2 and 5 μm was 5×107 microbubble/ml.

The solution was transferred in a 50 ml plastic syringe and samples were taken in time intervals for analysis. This represent the starting 100% of the bubble concentration. The syringe was mounted in the infusion unit and the elution started. The elution flow was fixed at 1.6 ml/min.

Aliquots of the eluted solution were analysed by Coulter measurement (bubbles distribution; size and concentration) and imaging.

TABLE 1 Radius Va 1.0 0.131 1.5 0.294 2.0 0.523 2.5 0.817 3.0 1.177 3.5 1.602 4.0 2.092 4.5 2.648 5.0 3.269 5.5 3.955 6.0 4.707 6.5 5.524 7.0 6.407 7.5 7.355 8.0 8.368 8.5 9.446 9.0 10.590 9.5 11.800 10.0 13.075 10.5 14.415 11.0 15.820 11.5 17.291 12.0 18.828 12.5 20.429 13.0 22.096 13.5 23.829 14.0 25.626 14.5 27.489

In water, the rate of rise (Va) by buoyancy of air filled microbubbles of radius (a) can be obtained from the following Stokes relation

Va = 2 

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