Patent Publication Number: US-2021161700-A1

Title: Infusion of drugs

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to the infusion of a substance, in particular drugs, into a patient&#39;s body and, more specifically, to the stimulation of penis erection. 
     When a male is stimulated erotically, connections between arteries and veins are closed (arteriovenous anastomoses) so that blood which is normally able to bypass the empty spaces or sinuses of the corpora cavernosa is retained in the penis. 
     The main vessels supplying the blood to the cavernous spaces in the erectile tissue of the corpora cavernosa are the deep arteries of the penis. They are therefore heavily involved in the erection of the penis. They give off numerous branches—the helicine arteries—that open directly into the cavernous spaces. When the penis is flaccid, these arteries are coiled, restricting blood flow. However, the smooth muscle in the coiled helicine arteries relaxes as a result of parasympathetic stimulation. In their relaxed state, the helicine arteries straighten, enlarging their lumina and allowing blood to flow into and dilate the cavernous spaces in the corpora of the penis at arterial pressure. In combination with the bulbospongiosus and ischiocavernosus muscles compressing the veins egressing from the corpora cavernosa, the erectile bodies of the penis become enlarged and rigid, and an erection occurs. 
     Patients suffering from erectile dysfunction can cause the penis to become turgid by injecting into the corpora cavernosa a medicament, such as papaverine or prostaglandin E1, causing the smooth muscles to relax. The patients have to learn a certain technique under doctor&#39;s supervision in order to be able to properly inject the medicament in each of the corpora cavernosa. Only after about 15 minutes after administration of the medicament will the medicament become effective. 
     Furthermore, the available medicaments are only stable when cooled and typically as a dry substance. Consequently, since long term storage of drugs stimulating penis erection is not possible with many currently available drugs, the drug to be injected would typically be provided as a first substance, such as a saline solution, to be mixed by the patient with a dry and cooled second substance shortly before the injection is performed. Thus, the entire procedure is inconvenient for the patient, the more so as proper administration and dosing is critical since the medicament may be transported with the blood into other regions of the patient&#39;s body if the injection is not done properly. 
     Recently, a different method has become known under the brand Muse®. In this method, a plastic rod comprising the medicament alprostadil is inserted into the urethra. Upon pressing a button, the alprostadil is released from the rod into the urethra. After removal of the plastic rod, the penis is rolled between the palms of the hands so that the medicament dissolves, distributes and is absorbed through the urethra wall. However, proper dosage and administration is also critical in this method. 
     The afore-mentioned problems are not limited to the administration of drugs stimulating penis erection. Similar problems can also occur in other applications where long term storage of a drug to be injected is difficult and, therefore, the drug must be kept cool and mixed together with other substances shortly before being administered to the patient. 
     It is therefore the object of the present invention to improve the administration of a drug into a patient&#39;s body, and more specifically to improve the stimulation of penis erection, so that the entire process is more reliable and more convenient for the patient. 
     SUMMARY OF THE INVENTION 
     The essence of the invention lies in injecting a substance into the patient&#39;s body using an implantable infusion device. This will greatly improve the patient&#39;s comfort as he no longer needs to pierce himself with an infusion needle, which for many people is not an easy task. Furthermore, due to the permanent implantation of the infusion device, the injection will always occur at the proper location, said location being selected such that the drug is most effective. While there are many conceivable technical variations for injecting the drug through the infusion device into the patient&#39;s body, such injections are definitely more convenient for the patient once the infusion device has been implanted as compared to the alternative of injecting the drug from outside the patient&#39;s body. 
     In addition to the implantable infusion device at least one implantable reservoir is provided in fluid connection with the infusion device to supply to the infusion device a substance to be injected into the patient&#39;s body. Furthermore, according to the present invention, a cooling device is provided for keeping the content within at least one compartment of the reservoir at a temperature below 37° C. This can be achieved with relatively little energy supply if the amount of drugs to be cooled is extremely little, as explained above, and if furthermore the drug compartment within the reservoir is thermally insulated. For instance, the reservoir may be comprised in an insulation chamber. 
     It is preferred to provide the cooling device with a heat exchanger for exchanging with the patient&#39;s body heat generated by the cooling device. Such heat exchanger may be implanted within the patient&#39;s body remote from the cooling device to safely dissipate the heat energy in an area where it cannot adversely affect the content of the reservoir. 
     The cooling device can be of a variety of different types. According to a first embodiment, the cooling device may contain at least two different chemicals reacting with each other, thereby consuming thermal energy which energy is drawn from the contents within the reservoir so that a cooling effect on the contents is achieved. The two chemicals may be provided in separate chambers and a flow control device may be provided to bring together certain amounts of the two different chemicals so as to control the amount of thermal energy drawn from the contents within the reservoir. 
     According to a second embodiment, the cooling device may comprise at least one Peltier element. A Peltier element is an electrothermal converter causing a temperature difference to occur when an electric current is flowing through the element, based on the Peltier effect. While one part of the Peltier element cools down, a different part thereof heats up. Such heat may again be removed by means of a heat exchanger or simply by providing the particular part generating the heat with an enlarged surface so that the heat is directly dissipated into the adjacent body part of the patient. 
     According to a third embodiment, the cooling device may be of a refrigerator-type construction. That is, heat exchanging pipes within a chamber to be cooled and heat exchanging pipes outside the chamber for dissipating the heat energy absorbed in the cooling chamber are provided along with a compressor for compressing the refrigerant gas when it exits the cooling chamber and an expansion valve for expanding the refrigerant gas before it re-enters the cooling chamber. 
     Preferably, the reservoir has at least one first compartment, e.g. for accommodating an infusion liquid such as a saline solution, and at least one second compartment, e.g. containing a drug, in particular a drug in dry form, for mixing with the infusion liquid of the first compartment. The at least one second compartment is cooled by means of the cooling device, whereas the at least one first compartment is not necessarily cooled. The drug contained in the second compartment may be in powder form and, more specifically, may be a freeze-dried drug. In particular, the drug contained in the second compartment would be a drug for stimulating penis erection. A mixing chamber may be provided for mixing the substance from the first compartment with the substance from one or more of the at least one second compartment. 
     The number of the second compartments may be huge, such as 50 or more, in particular 100 or more. This would not constitute a particular problem in terms of space constraints since the amount of drugs required for each stimulation of penis erection is extremely little and would amount to a few micrograms. Furthermore, the reservoir may be adapted for implantation within the patient&#39;s body remote from the housing containing the needle, such as close to the symphyseal bone. There is a lot of space available above the patient&#39;s symphyseal bone, and the drugs could be delivered to the infusion device through an appropriate conduit. If desired, one can inject pure saline solution after the drug injection has been completed so as to clean the conduit and infusion device from any drug residue. 
     Preferably, the second compartments containing the drug are liquid-tightly sealed against the first compartment, with a mechanism being provided for individually opening a connection between the second compartments and the first compartment. 
     According to a preferred embodiment, the second compartments are mounted in a plate so as to open towards a first side of the plate and the opening mechanism is adapted to act on the second compartments from a second side of the plate opposite the first side of the plate so that the compartments open to the first side of the plate. Thus, the second compartments may be pushed from their rear side (second side of the plate) so as to open frontward into e.g. a mixing chamber in which the content of the opened second compartments mixes with the content of the first compartment of the reservoir, such as with saline solution. More specifically, the second compartments may be mounted in the plate as displaceable drug containers and the opening mechanism may be adapted to displace the drug containers such that they deliver their drug contents in the manner described. 
     Alternatively, the plate may be rotatable so as to allow the drug containers to be brought into alignment with a conduit upon rotation of the plate. Thus, when the drug is brought into alignment with such conduit, it may be mixed with e.g. saline solution pumped through the conduit towards the infusion needle. 
     According to another preferred embodiment, the second compartments are mounted on a tape wound up on a reel. A plurality of rows of the second compartments may be arranged on the tape in side-by-side relationship in a direction different to the winding direction of the tape. This way, the length of the tape can be reduced. It is particularly preferable if the tape is contained in a replaceable cassette. Thus, when all of the second compartments of the tape are emptied, the tape can be easily replaced by replacing the cassette. 
     As mentioned above, while the reservoir may generally be part of the housing accommodating the at least one infusion needle, it is preferred to arrange the reservoir separate from the housing for remote implantation within the patient&#39;s body. 
     At least a section of a periphery of the first compartment of the reservoir may be made from a flexible material permitting volume changes of the first compartment by deformation of the flexible material as infusion liquid is filled into or drawn out of the reservoir. Thus, the reservoir may be of balloon type. The flexible material may comprise a polymer membrane. A bellows construction is preferable having pre-bent creases to reduce long term degradation. 
     According to a particular embodiment, drawing liquid from the reservoir may cause a pressure decrease in at least part of the reservoir so that a negative pressure is attained as compared to the pressure in front of the infusion needle. For instance, the first compartment of the reservoir may comprise a gas chamber and a liquid chamber, said chambers being separated by a membrane, e.g. the polymer membrane. When liquid is drawn from the liquid chamber, the pressure in the gas chamber will decrease accordingly. 
     The reservoir may have an injection port for injecting liquid from outside the human body into the implanted reservoir. That way, the reservoir implanted in the patient&#39;s body along with the infusion device may be kept relatively small since the reservoir can be refilled easily at appropriate time intervals, possibly with a doctor&#39;s aid. 
     Preferably, the injection port comprises a self-sealing material in respect of penetrations caused by a replenishing syringe that would be typically used to refill the reservoir through the patient&#39;s skin. It is preferable to implant the self-sealing injection port of the reservoir subcutaneously in the patient&#39;s body so that it is easily accessible for refill by means of the syringe. 
     The conduit or conduits for connecting the remotely implanted reservoir with the infusion device should have a length sufficient to bridge the distance between the patient&#39;s symphyseal bone and the inferior fascia of the patient&#39;s urogenital diaphragm, where the housing is preferably to be placed. Accordingly, the conduit should have a length of 10 cm or more. 
     The implantable infusion device of the system preferably comprises one or more infusion needles designed to permanently reside within the patient&#39;s body. Such a system with only one infusion needle is generally known from WO 2007/051563. At least one drive unit is coupled to the infusion needle or needles and arranged for advancing the tip end thereof to penetrate any fibrosis when the system is implanted in the patient&#39;s body. At least the infusion needle or needles and the at least one drive unit are designed for implantation in the patient&#39;s body along with the reservoir. Preferably, at least one pump, which is preferably also adapted for implantation inside the patient&#39;s body, is provided to advance the substance to be injected from the reservoir to the infusion device. Other components such as an energy source, a control unit and/or a data processing device may be extracorporal to complete the system. However, it is preferred that the aforementioned components be implanted as well, suitably forming an integral part with the remaining components of the system so as to be implantable as a unitary piece. 
     The infusion needle or needles may rest at the implantation site over a long time either for single use or for multiple use. For instance, where it is likely that a patient will suffer an allergic attack, such as severe allergic reactions affecting e.g. the respiratory tract, in the near future or possibly only within a year or two, the infusion needle and possibly the entire system may be implanted in the patient&#39;s body for single use at the appropriate time. Over time, fibrosis will grow on the system. However, at the time of use, the infusion needle may be advanced by the drive unit so as to penetrate any fibrosis, thereby allowing immediate drug delivery from the reservoir through the tip end of the infusion needle into the patient&#39;s body. Where the infusion needle is implanted adjacent a blood vessel, the tip end of the infusion needle may be advanced into the blood vessel without any risk of formation of thrombosis (nicht fibrosis?) prior to use. 
     Where the system is implanted for multiple use, the drive unit is preferably configured for advancing and retracting the tip end of the infusion needle. Thus, each time when the drug is delivered to the patient, the infusion needle will be advanced, the drug injected and the infusion needle retracted again. 
     Preferably, the infusion needle is disposed within a housing of the infusion device with the tip end of the infusion needle being arranged for passing through an outer wall of the housing. This prevents any fibrosis from growing into the infusion needle, in which case the infusion needle would still be blocked even after penetrating any fibrosis that has built up in front of the needle. In the case of multiple use, it is preferred when the at least one drive unit is coupled to the at least one infusion needle so as to advance and retract the tip end of the at least one infusion needle in such a way that it penetrates at least two different penetration areas within the housing&#39;s outer wall, so as to allow for injecting the substance through said at least two different penetration areas via the at least one infusion needle. For instance, the at least one needle may be arranged for penetrating the at least two different penetration areas either simultaneously (e.g. where a plurality of needles, i.e. at least two needles, are provided) or in immediate time succession (e.g. where a single needle is provided). Also, where more than one needle is provided, they may be arranged in separate housings. 
     More specifically, in order to stimulate penis erection, the substance may be injected into both the right and left corpus cavernosum and/or into the two deep arteries thereof and/or possibly into muscle tissue regulating blood flow through the right and left corpus cavernosum and/or into tissue in close proximity to the left and right corpus cavernosum, by means of an infusion device permanently implanted at an appropriate location inside the patient&#39;s body. Accordingly, the housing or housings accommodating the at least one infusion needle are preferably adapted for implantation inside the patient&#39;s body adjacent the two corpora cavernosa and/or the two deep arteries thereof and/or adjacent muscle tissue regulating blood flow through the patient&#39;s left and right corpus cavernosum and/or adjacent tissue in close proximity to the two corpora cavernosa. The distance between the two different penetration areas to be penetrated by the at least one infusion needle is selected such that the respective parts of the patient&#39;s body are pierced whenever the drug is to be injected. As will be described below, two or more infusion needles may be provided in order to inject the drug in the two or more different penetration areas, or a single infusion needle may be provided along with an appropriate drive unit for displacing the tip end of the infusion needle so as to penetrate the housing&#39;s outer wall in the respective different penetration areas. 
     Preferably, a single command or single action from the patient is sufficient for injecting the substance through the at least two penetration areas, either due to a corresponding mechanical structure of the drive unit or due to a suitably configured control unit controlling the drive unit. This will make the handling of the system easy for the patient. 
     Where two different penetration areas are pierced in immediate time succession, the time delay between the penetration of the first and the second of the penetration areas is preferably as short as possible, more preferably less than 120 seconds, and most preferably less than 60 seconds. This can be achieved by means of a properly controlled drive unit. A longer time delay would be inconvenient for the patient. Therefore, it is preferred that, once the infusion needle has been retracted from a first of the two penetration areas, it is immediately advanced to the second of the penetration areas. 
     While it is possible according to one aspect of the invention to actively open the outer wall for allowing the infusion device to penetrate the wall, it is preferred according to another aspect of the invention to arrange an infusion needle so as to penetrate the outer wall by piercing through the outer wall. For that purpose, the outer wall may either comprise flaps to be pushed aside by the infusion needle as the infusion needle is advanced, or the outer wall may be made at least in the penetration areas from a material which is self-sealing in respect of penetrations resulting from the at least one infusion needle. While the entire housing may be made from the self-sealing material, it is advantageous for stability reasons if the self-sealing material forms at least one window area in the outer wall, the window area being positioned for penetration by the tip end of the at least one infusion needle. The window area may be formed by a self-sealing penetration membrane which is preferably integrated in the outer wall by press fitting it into the outer wall. 
     Typically, the self-sealing material would be made from a polymer material which preferably comprises silicone. Other biocompatible polymer materials, such as polyurethane and the like, may be employed as well. 
     The self-sealing material may also be a composite material. A particularly preferred embodiment of such composite material comprises at least one outer shape-giving layer and a self-sealing soft material contained within the outer layer. Thus, the outer layer forms a shell for the soft material. The outer layer may be made from a biocompatible polymer, such as one of those polymers mentioned above, and preferably the self-sealing soft material may be a gel. 
     Instead of a self-sealing material, the part of the outer wall to be penetrated by the infusion needle may comprise one or more flaps in the penetration areas through which the infusion needle or needles can pass. This can reduce the force needed for the infusion needle to penetrate the outer wall, as compared to the penetration of a self-sealing membrane. The flap is preferably arranged to be pushed aside by the infusion needle upon advancement of the infusion needle. 
     Alternatively, the outer wall may comprise at least one door in the penetration areas. A drive is connected to the door for actively opening the door so as to allow for the infusion device to be advanced through the opened door. Again, the door may comprise a flap, such as a resilient, normally closed flap. It is particularly preferred if the drive connected to the door forms part of the drive unit coupled to the infusion needle. More specifically, the arrangement may be such that advancement of the infusion device by means of the drive unit simultaneously causes the drive to open the door. 
     Where a single housing is provided for the at least one infusion needle or where two or more penetration areas are arranged in a single housing, the penetration areas may be arranged in the housing so that they can be placed either adjacent to both the right and left corpus cavernosum of the patient&#39;s penis and/or the two deep arteries of the right and left corpus cavernosum and/or adjacent to muscle tissue regulating blood flow through the right and left corpus cavernosum and/or in sufficiently close proximity to another type of tissue allowing both the first and second corpus cavernosum to become turgid when the particular drug is injected thereinto. 
     The at least one infusion needle preferably has a tube-like body closed at the tip end and provided with a laterally arranged delivery exit port for delivery of the drug into the particular body part. Therefore, the needle will not cut out any material but will simply divide it during penetration. Thus, when the needle penetrates any material, such as fibrosis and/or the self-sealing penetration membrane, there will be no material entering and blocking the drug delivery passageway. 
     As mentioned above, a separate infusion needle may be provided for each of the two or more penetration areas. Thus, where injection is desired to occur in only two different areas to provoke penis erection, two separate infusion needles may be advanced through the corresponding penetration area of the respective housing—preferably simultaneously—and retracted again after injection. 
     According to a preferred embodiment, two or more infusion needles are provided for each of the different penetration areas and arranged for penetrating different penetration sites within each of said different penetration areas. This allows for penetrating different sites within each penetration area at different times, thereby giving the human tissue time to recover from the piercing by the infusion needle. This can be achieved with a drive unit suitably configured to advance and retract one infusion needle in each of said different penetration areas at one time, and to advance and retract a different infusion needle in each of said different penetration areas at a different time. 
     Since it is preferred for reasons of space constraints to implant the reservoir remote from the injection area or areas, it can be advantageous to employ long infusion needles that are flexibly bendable. The tip end of such infusion needles would then be arranged within a first housing so as to penetrate the outer wall thereof upon advancement of the long infusion needle, whereas the other end of the infusion needle would be arranged in a second housing remotely implanted inside the patient&#39;s body. The injection needle would be sufficiently long to bridge the distance from the second housing for remote implantation to the first housing and further through the first housing up to the outer wall of the first housing to be penetrated by the needle. The long and flexibly bendable infusion needle may be guided within a suitable sheath. Furthermore, for reasons of space constraints, it is advantageous to also arrange at least a part of the drive unit for advancing and retracting the tip end of the infusion needle remote from the injection area, preferably within the second housing and even more preferably in a common housing with the remotely implanted reservoir. More preferably, most or all of the active parts, such as a motor, pump and the like, may be accommodated in the remotely implanted second housing, whereas the first housing only includes passive elements. 
     A drive unit according to the present invention includes not only the drive itself, such as an electric motor, but also those components which are involved in transforming the driving energy provided by the drive into movement of the at least one needle, such as transmission gears and the like. 
     For instance, in the case of the long flexibly bendable infusion needle, the drive unit may be such that the infusion needle is advanced and/or retracted by turning the infusion needle or by turning an element cooperating with the infusion needle. More specifically, the drive unit for advancing and retracting the infusion needle may comprise a screw drive connection. For instance, the drive of the drive unit may turn a screw threadingly engaged with a rack coupled to the infusion needle so that rotation of the screw will cause the infusion needle to be advanced or retracted. The screw and rack of the screw drive connection are preferably accommodated in the remotely implanted second housing but may also be arranged in the housing accommodating the tip end of the needle. Instead of the screw, the infusion needle itself may be rotated by means of a suitable drive so that threading on the needle engaging a fixedly mounted rack causes the infusion needle to advance or retract upon rotation of the infusion needle. Between the first and second housings, the infusion needle is preferably guided in a sheath, so as to reduce friction and prevent growth of fibrosis that might hinder movement of the needle. 
     The infusion needles or, in the case of the afore-mentioned long and flexibly bendable infusion needles, at least the tip ends thereof, may be contained in a common housing in spaced apart relationship, with the drive unit being configured to advance and retract the tip ends of the infusion needles so as to penetrate the outer wall of the common housing in said at least two different penetration areas, again preferably simultaneously. Placing the needles or at least the tip ends thereof in a common housing simplifies the procedure for fixing the needles in place close to the injection areas. Furthermore, a single drive unit may be used for advancing and retracting the tip ends of the plurality of infusion needles, this making the entire system less voluminous. The use of a single drive unit is particularly advantageous where the drive unit is also contained in the common housing, i.e. where the drive unit is also to be implanted close to the very constrained injection area. 
     Again, according to a particularly preferred aspect of the invention, the tip ends of the infusion needles are laterally movable, so as to vary the penetration sites within the particular penetration areas of the housing&#39;s outer wall, thereby varying the injection site within the particular injection area in the patient&#39;s body. As set out above, frequent piercing of the same body part may cause irritation, eventually making further piercing difficult or even impossible. Variation of the injection site by laterally displacing the needle upon each injection cycle may overcome such problems. Accordingly, the drive unit in the common housing is preferably configured to laterally displace the tip ends of the infusion needles to different penetration sites within each of said different penetration areas. More specifically, the drive unit is preferably configured to laterally displace the tip ends of the infusion needles simultaneously. This can be achieved e.g. by jointly mounting the infusion needles on a movable carriage of the drive unit, such as a turntable and/or a shuttle, possibly in the form of a slide. Thus, the drive unit for advancing and retracting the tip ends of the infusion needles is preferably configured so as to also laterally displace the tip ends of the infusion needles each time the tip ends are advanced or retracted. 
     Thus, the lateral displacement and the advancement/retraction of the tip ends of the infusion needles are coordinated. The lateral displacement of the tip ends of the infusion needles may take place before and/or after an injection. The mechanism may be such that after a certain number of lateral displacements or after lateral displacement over a predefined distance, the tip end of the infusion needle is laterally returned to its initial position so that the next number of infusions will take place again at locations that have previously been penetrated by the needle. It is even preferred to configure the drive unit such that the tip ends of the infusion needle are displaced in at least two different lateral directions. For instance, when the infusion needle has laterally returned to its initial position, the next number of infusions may take place somewhat laterally offset above or below the first number of penetration sites. This permits a two-dimensional array of penetration sites to be obtained. 
     The infusion needles may be arranged one above the other within the common housing. Generally speaking, it is preferable in such a situation that the direction of lateral displacement of the tip ends of the infusion needle within the different penetration areas is different from, in particular perpendicular to, the direction of distance between the different penetration areas. Alternatively, where the infusion needles are arranged with great lateral distance between each other, the direction of lateral displacement of the tip ends of the infusion needles within each of the two different penetration areas may generally be the same as the direction of distance between the different penetration areas. 
     It is likewise possible to provide a single infusion needle within the housing and to implant the housing within the patient&#39;s body adjacent the two or more injection areas. In this case, the drive unit may be configured so as to laterally displace the tip end of the one infusion needle between various lateral positions such that the infusion needle can penetrate the housing&#39;s outer wall in the different penetration areas. The distance of lateral displacement of the single infusion needle between the different penetration areas would amount to 3 mm, 4 mm, 5 mm or even more upon each successive injection. Such successive injections are preferably in immediate time succession, preferably not exceeding 120 seconds between two injections, more preferably not exceeding 60 seconds. Most preferably, the drive unit will be adapted to initiate advancement of the one infusion needle to a second one of the plurality of penetration areas once it has been retracted from a first one of the penetration areas. 
     An implantable infusion device comprising a single, laterally displaceable infusion needle contained within a housing so as to penetrate the housing&#39;s outer wall at different penetration sites is generally known from WO 2007/051563. However, this prior art device is neither intended nor configured for injecting drugs simultaneously or quasi-simultaneously in immediate time succession in two or more different injection areas. The drive unit of the prior art device is instead configured to administer the drug at a different penetration site of a single injection area at each time of operation. For instance, the prior art device may be placed along a blood vessel so as to inject drugs at different injection sites within a single injection area of the blood vessel. Thus, the distance of lateral displacement of the tip end of the infusion needle between one injection and a next following injection is not configured in the prior art device such that different injection areas within the patient&#39;s body could be reached. Also, the prior art infusion device is not aimed at being used for the stimulation of penis erection. 
     Turning back to the present invention, it is again preferable, when the patient desires to achieve another penis erection at a later point of time, that the single infusion needle does not penetrate the same penetration site within the particular penetration area of the housing&#39;s outer wall, but that the drive unit is configured to laterally displace the tip end of the one infusion needle to different penetration sites within each of the different penetration areas. Again, the direction of lateral displacement of the tip end of the one infusion needle within each of the different penetration areas may either be the same as the direction of lateral displacement of the tip end of the infusion needle between the different penetration areas, or may be different from, in particular perpendicular to, the direction of lateral displacement of the tip end of the infusion needle between the different penetration areas. Depending upon the particular configuration of the system, this may be achieved with a single, multifunctional drive unit or with a plurality of different drive units suitably arranged to work in coordinated fashion. Even a combination of these alternatives is possible, leading again to a two-dimensional array of penetration sites within each penetration area. 
     Where the housing or at least the window area thereof is formed spherically, even a three-dimensional array of penetration sites through the housing&#39;s outer wall can be obtained by means of a suitably adapted drive unit for the needle displacement. This greatly increases the system&#39;s flexibility of use. 
     Regardless of the number of needles involved and regardless of the particular penetration site array to be achieved, it is preferable to configure the drive unit such that the lateral displacement of the tip end of the infusion needle or needles is achieved automatically during advancement and/or retraction of the tip end of the needle or needles. For instance, where the infusion needle is mounted on a movable carriage for the lateral displacement of the tip end of the needle, such as on a turntable or a shuttle, e.g. in the form of a slide, the drive unit may comprise a stepper which is adapted to automatically advance the movable carriage a predefined distance upon each advancement and/or retraction of the infusion needle. 
     Turning now to the pump for advancing the infusion liquid from the reservoir to the infusion needle or needles, such pump may be a manually driven pump or an automatically driven pump. The manually driven pump may be formed from a balloon which may be manually compressed if suitably arranged under the patient&#39;s skin. The balloon type pump may at the same time serve as a reservoir for the infusion liquid, in particular for the saline solution. Preferably, however, an automatically driven pump is used. While the type of pump is not critical, one specific type of pump is particularly preferred. More particularly, an implantable pump preferably comprises a valve device having a first and a second valve member, each having a smooth surface facing each other so as to form a sealing contact between the first and second valve members and further having different liquid channels that can be brought into alignment by displacement of the two smooth surfaces relative to one another while maintaining the sealing contact. This type of pump is described in great detail in WO 2004/012806 A1. The first and second valve members are preferably made from a ceramic material for its excellent sealing capabilities over a long period of time and its inertness to many substances. 
     The pump may be a membrane type pump, as also described in WO 2004/012806 A1, but is not restricted to this type of pump. The membrane type pump may comprise a membrane displaceable by a piston as the piston moves, the piston being coupled to the valve device so as to slidably displace the first and second valve members relative to one another as the piston moves. Preferably, the pump will be implanted separate from the housing accommodating the needle or needles for remote implantation within the patient&#39;s body. 
     Due to the space constraints within the patient&#39;s body in the area where injection is to take place, it is advantageous to implant as many components of the system as possible remote from the housing accommodating the infusion needle or needles. In this context, the drive unit may comprise a mechanical drive element for transmitting kinetic energy from a remote location within the patient&#39;s body to the at least one infusion needle. The mechanical drive element may comprise a rotating shaft by which a considerable distance can be bridged within the patient&#39;s body. The rotating shaft may, upon rotation about its axis of rotation, cause movement of the infusion needle either directly or indirectly. More specifically, the rotating shaft may be in the form of a worm screw which, when turned, causes the infusion needle or needles to advance and retract and/or causes the infusion needle or needles to move laterally upon each advancement/retraction. Individual rotating shafts or worm screws may be provided for each individual infusion needle and/or for advancing and retracting the tip end of the infusion needle or needles on the one hand and laterally displacing the tip end of the infusion needle or needles on the other hand. Most preferably, the rotating shaft or worm screw is flexibly bendable, so that it can be freely arranged within the patient&#39;s body. 
     Alternatively or in addition, the drive unit may comprise at least one wire directly or indirectly cooperating with the infusion needle so as to cause movement of the infusion needle upon actuation of the wire. Thus, the wire may be pulled at one end thereof which is located within the patient&#39;s body remote from the injection sites. Preferably, the wire extends through the same conduit which connects the infusion needle or needles with the reservoir. More specifically, pulling the wire may cause the tip end of the infusion needle or needles to displace laterally from a first to a second of the different penetration areas or from a first penetration site to a second penetration site within a single one of the different penetration areas. A single pulling wire may be sufficient to cause movement of the infusion needle in one direction, whereas a spring element or any other pretensioning means may be provided to urge the infusion needle back to the initial starting position or to a different starting position. Alternatively, two pulling wires may be provided to move the infusion needle back and forth in a single dimension. 
     According to a preferred embodiment, the infusion needle is arranged for two-dimensional lateral displacement. This can be achieved by means of two pulling wires, preferably cooperating again with spring elements or other pretensioning means to provide a counterforce to be overcome by pulling the wires. Alternatively, three pulling wires may be provided to laterally displace the tip end of the infusion needle back and forth along at least two directions within a two-dimensional plane. 
     A pulling wire may also be arranged to advance or retract the infusion needle by pulling the wire. Again, a spring element or other pretensioning means may be provided to urge the infusion needle back to its initial starting position or to a different starting position. 
     Alternatively, the drive unit may comprise a hydraulic drive for transmitting hydraulic energy from a remote location within the patient&#39;s body to the at least one infusion needle for advancing the tip end thereof and/or for laterally displacing the tip end thereof. The infusion liquid itself may be used as the hydraulic medium providing the hydraulic energy, or a secondary liquid different from the infusion liquid may be used. 
     Further alternatively, the drive unit may comprise one or more electric motors inside the housing accommodating the at least one infusion needle. In this case, energy may be transmitted from a remote location within the patient&#39;s body to the at least one motor by means of appropriate wiring. Again, as in the two afore-described alternatives, a single motor may be provided for advancing and retracting the tip end of the infusion needle or needles and for laterally displacing the tip end of the infusion needle or needles, or individual motors may be provided for each individual infusion needle and/or for advancing the tip ends of the infusion needle or needles on the one hand and laterally displacing the infusion needle or needles on the other hand. 
     Even further alternatively, the drive unit may comprise an electromagnetic drive for laterally displacing and/or for advancing and retracting the tip end of the infusion needle or needles. For instance, the electromagnetic drive may comprise a group of electromagnets composed of a plurality of laterally spaced apart electromagnet first parts and at least one electromagnet second part, the electromagnet second part cooperating with an energized one of the electromagnet first parts. The electromagnet second part is fixedly connected to the infusion needle or needles either directly or indirectly so that upon energization of one or more of the electromagnet first parts the electromagnet second part and, thus, the infusion needle or needles will be caused to move. The arrangement of the electromagnet first parts and second part may be such that the electromagnet first parts are arranged in a first plane and the electromagnet second part is movable in front of or behind the first plane. Alternatively, the electromagnet first parts may face each other, thereby defining a first plane between them, and the electromagnet second part may be movable within the first plane. Depending on which one or ones of the electromagnet first parts are energized, the electromagnet second part with the infusion needle or needles fixed thereto will move accordingly. The electromagnet first parts preferably each include a magnetic coil. 
     In either one of the aforementioned alternatives, it is advantageous to transmit the driving energy through the conduit that connects the at least one infusion needle with the remotely implanted reservoir. That is, in the case of a mechanical drive element in the form of a wire or rotating shaft, the wire/shaft and the infusion liquid may be guided through a common conduit. The common conduit may comprise two separate paths, one for the shaft or wire and one for the infusion liquid. Such a common conduit facilitates the handling and arrangement of the system during implantation. Similarly, the wiring for transmitting electric energy to the motor or to the electromagnetic drive may be guided through a conduit connecting the infusion needle or needles with the reservoir. 
     Where the pump and/or drive unit is not actuated manually, a drive in the form of a motor may be arranged e.g. for electrically, magnetically or electromagnetically actuating the pump and/or drive unit or for hydraulically actuating the pump and/or drive unit. The motor is preferably arranged for actuating either the pump or the drive unit, thereby causing simultaneous actuation of the other, e.g. the drive unit or the pump. A motor may also be provided for actuation of any other energy consuming part of the infusion device. More specifically, a plurality of motors may be provided, e.g. an individual motor for each infusion needle and/or an individual motor for displacing the tip end of the infusion needle in a lateral direction on the one hand and for advancing the tip end of the infusion needle through the housing&#39;s outer wall on the other hand. 
     Again, for reasons of space constraints in the area of implantation of the housing accommodating the infusion needle or needles, it is advantageous to remotely implant the motor within the patient&#39;s body separate from the housing. Again, actuating means may be provided for manual activation of the motor or motors, such actuating means preferably being adapted for subcutaneous implantation. 
     The term “motor” according to the present invention includes anything that employs energy other than manual power and either automatically transforms such energy into kinetic or hydraulic or another type of energy or directly uses such energy to activate the pump, drive unit and/or other part of the overall system. As such, it is possible that part of the drive unit also forms part of the motor, e.g. in the case of an electromagnetically actuated drive unit. 
     Coupling elements may be provided either for conductive or for wireless energy transfer from outside the patient&#39;s body to the motor. For instance, the motor may be arranged for being wirelessly driven by an external electromagnetic field. 
     An energy source for providing energy to at least one of the pump, the drive unit and the drive (motor) for driving the drive unit, and any other energy consuming part of the system may be provided. For instance, an external energy source for use outside the patient&#39;s body, such as a primary energy source or a battery, in particular a rechargeable battery, that may be mounted on the patient&#39;s skin, may be used to provide energy to the pump and/or drive unit and/or any other energy consuming part of the system. The energy source may in particular be connected to the at least one motor for actuating these components. An external energy source for wireless energy transfer may be adapted to create an external field, such as an electromagnetic field, magnetic field or electrical field, or create a wave signal, such as an electromagnetic wave or sound wave signal. 
     Where the energy is wirelessly transferred to the implanted components, a transforming device for transforming the wirelessly transferred energy into electric energy may be provided. Such transforming device is preferably adapted to be placed directly under the patient&#39;s skin so as to minimize the distance and the amount of tissue between the transforming device and the energy supply means outside the patient&#39;s body. 
     Instead of or in addition to an external energy source, the system may comprise an implantable energy source. While such implantable energy source may be part of or may be contained within the housing accommodating the infusion needle or needles, it is preferred to provide the implantable energy source separate from the housing for remote implantation within the patient&#39;s body. Such implantable energy source preferably comprises energy storage means, such as a long-life battery or, more preferably, an accumulator. The accumulator has the advantage of being rechargeable. Preferably, the accumulator comprises a rechargeable battery and/or a capacitor. 
     Again, coupling elements for conductive or wireless energy transfer from a primary energy source outside the patient&#39;s body to the accumulator may be provided for charging the accumulator from outside the patient&#39;s body when the device is implanted in the patient&#39;s body. Similarly, the accumulator may comprise coupling elements for conductive and/or wireless energy supply to the at least one motor of the infusion device. 
     A feedback subsystem, which may be part of a control unit described below, can advantageously be provided to wirelessly send feedback information relating to the energy to be stored in the energy storage means from inside the human body to the outside thereof. The feedback information is then used for adjusting the amount of wireless energy transmitted by the energy transmitter. Such feedback information may relate to an energy balance which is defined as the balance between an amount of wireless energy received inside the human body and an amount of energy consumed by the at least one energy consuming part. Alternatively, the feedback information may relate to an energy balance which is defined as the balance between a rate of wireless energy received inside the human body and a rate of energy consumed by the at least one energy consuming part. 
     Preferably, a control unit is provided for controlling an amount of infusion liquid to be administered through the at least one injection needle. A single command from the patient to the control unit, such as a single actuation of a press button or other type of switch, is sufficient for causing the control unit to control the injection of the drugs at two different locations within the patient&#39;s body. The control unit may be provided for controlling at least one of the pump, the drive unit and the motor and any other energy consuming part of the system and, where the system includes an internal or external energy source, said energy source. Again, the control unit is preferably separate from the housing accommodating the infusion needle or needles so as to be implantable within the patient&#39;s body. The control unit may be adjusted such that the appropriate amount of drugs will be administered at the appropriate time to the particular one of the injection sites. Automatic administration will substantially relieve the patient. 
     Preferably, the control unit has a data transfer port for data transfer between an external data processing device outside the patient&#39;s body and the control unit implanted in the patient&#39;s body, regardless of whether the control unit is contained in the housing accommodating the infusion needle or needles or whether it is implanted within the patient&#39;s body remote from said housing. The data transfer port allows for monitoring the control unit to adapt the system to changing needs of the patient. Preferably, the data transfer port is a wireless transfer port for the data transfer, so as to provide easy data exchange between the control unit and the external data processing device, e.g. during a visit to the doctor. Most preferably, the control unit is programmable to further increase its adaption flexibility. Instead of or in addition to the external data processing device, the control unit may comprise an external component for manual operation by the patient for setting into operation the control unit. 
     Apart from or as a part of the control unit, feedback may be provided on parameters relevant for the treatment. Such parameters may be either physical parameters of the patient and/or process parameters of the system. For this purpose, at least one feedback sensor is provided for detecting such parameters. For instance, the feedback sensor may be adapted to detect one or more parameters relating to any of the following: drug level, flow volume in blood vessel, pressure, electrical parameters, distension, distance, etc. 
     The feedback sensors may be connected to the control unit and the control unit may comprise a control program for controlling drug delivery in response to one or more signals from the feedback sensors. In addition or alternatively, feedback data may be transferred from the control unit to the external data processing device. Such feedback data may be useful for the doctor&#39;s diagnosis. 
     The penetration areas of the wall or walls of the housing or housings within which the infusion needle or needles are disposed may be arranged in the patient&#39;s body at various locations. For instance, they may be arranged adjacent the left and right corpora cavernosa and/or the two deep arteries running through the left and right corpora cavernosa and/or muscle tissue regulating blood flow through the patient&#39;s left and right corpora cavernosa and/or another kind of tissue in close proximity to the left and right corpora cavernosa. 
     A holder may be used to secure the corpora cavernosa to the housing or housings so that the housing rests in place. 
     Other components of the system are preferably remotely implanted, such as adjacent the patient&#39;s symphyseal bone. As discussed above, some components of the may be implanted subcutaneously. Subcutaneous implantation increases the possibilities of wireless energy and/or data transfer between the implanted and the extracorporal parts of the system. Also, refilling the reservoir through an injection port by means of a replenishing needle penetrating through the patient&#39;s skin is substantially facilitated when an injection port of the reservoir is implanted subcutaneously. In particular, the compartment of the reservoir containing the saline solution might need to be refilled frequently, whereas the other compartments comprising individual small doses of the drug would need no refill. It should be understood, however, that depending upon the circumstances any implantable component of the system may be placed in the abdomen or even in the thorax. Activating means for direct manual operation by the patient may also be provided to be implanted subcutaneously, e.g. for setting into operation one or more of the aforementioned motors or for simply setting into operation the control unit of the system. Such activating means may be in the form of a subcutaneously implantable switch manually operable by the patient from outside the patients body. 
     The various aforementioned features of the invention may be combined in any way if such combination is not clearly contradictory. The invention will now be described in more detail in respect of preferred embodiments and with reference to the accompanying drawings. Again, individual features of the various embodiments may be combined or exchanged unless such combination or exchange is clearly contradictory to the overall function of the device. In particular, while the following description of preferred embodiments specifically relates to the stimulation of penis erection and, more specifically, to systems for the drug delivery at two or more different injection sites, it is to be understood that other uses, in particular with a single needle adapted for drug delivery in a single injection site, are also encompassed by this invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the muscles of the perineum, 
         FIG. 2  shows a cross-section through the penis, 
         FIG. 3  shows a first embodiment including a single needle, 
         FIG. 4  shows a second embodiment including a single needle and a motor accommodated in a common housing, 
         FIG. 5  shows a third embodiment including two needles in a common housing, 
         FIG. 6  shows a plan view of a part of the infusion device of  FIGS. 4 and 5 , 
         FIG. 7  shows a cross-sectional view through a penetration membrane made from a composite material, 
         FIG. 8  shows a cross-sectional view through the outer wall with flaps in the penetration area, 
         FIG. 9  shows a cross-sectional view through the outer wall with an actively openable door in the penetration area, 
         FIG. 10  shows a cross-sectional view through the outer wall with an actively openable door according to another embodiment, 
         FIG. 11  shows a fourth embodiment including a plurality of needles within a common housing, 
         FIG. 12  shows a fifth embodiment comprising a single needle which is laterally and vertically displaceable, 
         FIG. 13  shows a sixth embodiment similar to the fifth embodiment, but with more steps for laterally displacing the needle, 
         FIG. 14  shows a seventh, spherical embodiment for obtaining a three-dimensional array of penetration sites, 
         FIG. 15  shows an eighth embodiment comprising two needles in a common housing which are laterally and vertically displaceable, 
         FIG. 16  shows a ninth embodiment with a principle of advancing and retracting an infusion needle by means of a pull wire, 
         FIG. 17  shows a tenth embodiment with a principle of laterally displacing an infusion needle by means of pull wires, 
         FIG. 18  shows an eleventh embodiment with a principle of advancing and retracting a needle and laterally displacing a needle by means of rotating shafts, 
         FIG. 19  shows the overall system of the invention implanted in a patient&#39;s body according to a first variation, 
         FIG. 20  shows the overall system of the invention implanted in the patient&#39;s body according to a second variation, 
         FIG. 21  shows the overall system of the invention implanted in the patient&#39;s body according to a third variation, 
         FIG. 22  shows drug compartments as part of the reservoir of the system according to a first principle, 
         FIG. 23  shows drug compartments mounted on a tape wound on a reel in a replaceable cassette as part of the reservoir of the system according to a second principle, 
         FIG. 24  shows a part of the tape of  FIG. 19  in greater detail, 
         FIG. 25  shows the principle of operation of the replaceable cassette of  FIG. 23 , 
         FIG. 26  shows drug compartments as part of the reservoir of the system according to a third principle, 
         FIG. 27  shows a cross-sectional view through the drug compartments of  FIG. 26  including an insulation chamber and cooling device, 
         FIG. 28  shows the principle of the cooling device of  FIG. 27  in combination with a heat exchanger, 
         FIG. 29  shows a specific embodiment for the cooling device of  FIG. 27 , 
         FIG. 30  shows a part of the system implanted in the patient&#39;s body comprising separate needles for the right and the left corpus cavernosum, 
         FIG. 31  diagrammatically shows the system of  FIG. 30 , 
         FIG. 32  shows a part of the system of  FIG. 31 , including a tube into which the needle can be advanced, 
         FIGS. 33A to 33C  show a first and second embodiment for electromagnetically displacing the infusion needle in a plurality of lateral directions, and 
         FIGS. 34A and 34B  show a third embodiment for electromagnetically displacing the infusion needle in a plurality of lateral directions. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows the muscles of the perineum of a male. Reference numerals  1 ,  2  and  3  designate the ischiocavernosus muscles, bulbospongiosus muscles and superficial transverse perineal muscles, respectively. The bulbospongiosus muscle surrounds lateral aspects of the bulb of the penis at the most proximal part of the body of the penis inserting into the perineal membrane, and further surrounds the dorsal aspect of the corpus spongiosum  4  surrounding the urethra  5  and the left and right corpora cavernosa  6 ,  7 . The ischiocavernosus  1  embraces the crus of the penis, inserting onto the inferior and medial aspects of the crus and to the perineal membrane medial to the crus. While the bulbospongiosus muscle assists the erection by compressing outflow via the deep perineal vein and by pushing blood from the bulb into the body of the penis, the ischiocavernosus muscle  1  maintains erection of the penis by compressing outflow veins and pushing blood from the root of the penis into the body of the penis.  FIG. 2  is a cross-sectional view through the penis. As can be seen, the penis is composed of three cylindrical bodies of erectile cavernous tissue: the paired corpora cavernosa  6 ,  7  dorsally and the single corpus spongiosum ventrally. Deep arteries  9 ,  10  run distally near the center of the corpora cavernosa, supplying the erectile tissue in these structures. The deep arteries of the penis are the main vessels of the cavernous spaces in the erectile tissue of the corpora cavernosa and are therefore involved in the erection of the penis. They give off numerous branches that open directly into the cavernous spaces. When the penis is flaccid, these arteries are coiled, restricting blood flow. 
     For reasons of simplification, the following figures only display the corpora cavernosa  6 ,  7 .  FIG. 3  shows a part of the system according to a first embodiment. More specifically, a single infusion needle  11  is arranged in a housing  12  with a tip end  13  of the needle  11  being positioned such that it can be advanced and retracted through a self-sealing window area  14  in the housing&#39;s  12  outer wall  15  in a longitudinal direction  16 , so as to pierce the corpus cavernosum  6  or  7  located adjacent the window area  14 . 
     Two window areas  14  are provided in the outer wall  15  of the housing  12 , one adjacent each of the two corpora cavernosa  6 ,  7 . The infusion needle is displaceable in a lateral direction  17  between the two window areas  14  by means of a drive unit D. The same drive unit D or a different drive unit may cause the infusion needle  11  to be advanced and retracted. For this purpose, the infusion needle  11  is mounted on a slide  18  for longitudinal advancement and retraction. A conduit  19  is connected to one end of the infusion needle  11  to supply infusion liquid through the infusion needle  11  to the tip end  13  thereof. 
     In operation, the infusion needle  11  will first be advanced with the tip end  13  thereof to penetrate one of the two self-sealing penetration windows  14 , injection fluid containing a drug for stimulation of penis erection will be injected into the corpus cavernosum  7  through the infusion needle  11  and, thereafter, the infusion needle  11  will be retracted again. Upon retraction of the infusion needle, the infusion needle will be laterally displaced along the direction  17  so that the tip end  13  thereof comes to lie in front of the other of the two self-sealing window areas  14 , the infusion needle  11  will be advanced again so that infusion liquid can be injected through the tip end  13  thereof into the other corpus cavernosum  7  and then the infusion needle  11  will be retracted again. At the end of this procedure, the infusion needle  11  will return to its initial position shown in  FIG. 3 . 
     The structure of the system shown in  FIG. 3  may be purely mechanical. For instance, as will be described in more detail below, the pressure with which the infusion liquid is advanced through the conduit  19  towards the needle  11  may in cooperation with spring elements cause the needle  11  to be advanced, retracted and laterally displaced to the other window area  14 . Thus, after two pulses of injection fluid advanced through the conduit  19  towards the needle  11 , the needle  11  will automatically return to its starting position shown in  FIG. 3 . 
     However, it is likewise possible to incorporate a motor M or a plurality of motors M within the housing  15  in order to achieve the desired needle displacement by means of the drive unit D. This is schematically shown in  FIG. 4 . Of course, the motor M will have to be provided with energy and will need to be controlled in an appropriate manner so as to obtain the desired effect. This is not specifically shown in  FIG. 4 . The energy is preferably transmitted to the motor M from an energy source either remotely implanted inside the patient&#39;s body or provided externally of the patient&#39;s body. 
     The drive D may be configured such that after each penetration cycle (consisting of two injections) the infusion needle  11  stops at a position different from the starting position so that the tip end  13  thereof penetrates the window areas  14  in the next following injection cycle at different sites as compared to the foregoing injection cycle. 
       FIG. 5  shows a third embodiment which differs from the first and second embodiments in that it comprises two infusion needles  11  contained in the housing  15 . Thus, when infusion liquid is guided through the conduit  19  towards the two infusion needles  11 , both needles are advanced and retracted simultaneously along the direction  16 , so that injection of infusion liquid occurs at exactly the same time. The drive unit D or a separate drive unit may be used to turn the turntable  20  on which the infusion needles  11  are mounted, stepwise in the direction  17  so that the window areas  14  will be penetrated by the tip end of the infusion needle  11  at different penetration sites during the next following injection cycle. Again, one or more motors M, not shown in  FIG. 5 , may be used for driving one or more of the components of the drive unit D. 
     The principle of a guide structure for laterally displacing the infusion needle will now be described in context with  FIG. 6 . Such guide structure may be used e.g. for each of the two infusion needles  11  shown in  FIG. 5  or may also be used slightly modified for the lateral displacement of the infusion needle  11  shown in  FIGS. 3 and 4 . 
     The guide structure  28  is securely fixed adjacent the self-sealing window area  14  which itself is implanted adjacent the patient&#39;s corpus cavernosum  7 . The guide structure  28  comprises a guide pin  27  securely connected to the infusion needle  11  (not shown) such that the infusion needle  11  cooperates with the guide structure  28 . Upon advancement or retraction of the infusion needle  11 , the guide pin  27  will be guided in the guide structure  28  and thereby laterally displace the infusion needle  11 , which lateral displacement causes rotation of the turntable  20  (not shown in  FIG. 6 ). Resilient flaps  28   a ,  28   b  within the guide structure  28  serve to guide the guide pin  27  through the entire guide structure  28  upon repeated advancement and retraction of the infusion needle  11 . The guide structure  28  is designed to provide different penetration sites through the self-sealing window area  14  into the corpus cavernosum  7 . Where it is desired, the trajectory of guide structure  28  may include a return path  28   c  for the guide pin  27  to return to its starting position shown in  FIG. 6 . Such return action will be caused by a return spring  29  which is permanently fixed to a rigid part of the housing  15 . 
     The same structure can likewise be used in the embodiments shown in  FIGS. 3 and 4  to displace the single infusion needle  11  laterally between the two window areas  14 . Of course, the structure would have to be slightly adapted to accommodate for the larger distance to be overcome between the two window areas  14 . 
       FIG. 7  shows a preferred embodiment of a penetration membrane to be used as the self-sealing window area  14  in the outer wall  15  of the housing  12 . The penetration membrane  30  is made from a composite material. The same material can also be used for other flexible wall portions or for an infusion port that will be described below in connection with another embodiment. The composite material of penetration membrane  30  shown in  FIG. 7  comprises an outer shape-giving layer  30   a  defining a volume in which a self-sealing soft material  30   b  is contained. Self-sealing soft material  30   b  can be of gel type having a viscosity such that it does not flow through any penetrations caused by the infusion needle  11  during penetration of the outer shape-giving layer  30   a . Instead of a single outer shape-giving layer  30   a , the shape-giving layer  30   a  may comprise a plurality of layers. The outer shape-giving layer  30   a  preferably comprises silicone and/or polyurethane, since such materials can be produced to have self-sealing properties in respect of penetrations resulting from the infusion needle  11 . 
     Instead of a self-sealing membrane, the window area  14  in the outer wall  15  of the housing  12  may be formed by one or more flaps, as shown in  FIG. 8 . Two flaps  30 ′ being made from a resilient, biocompatible material are arranged so as to form a slit which is normally closed and through which the infusion needle  11  can pass when it is advanced. Upon advancement of the infusion needle  11 , the needle will push aside the normally closed flaps  30 ′, and when the needle  11  is retracted again, the flaps  30 ′ will return to their normally closed position so as to form a seal against ingression of body liquid. 
       FIG. 9  shows a different embodiment. In this case, the self-sealing window  14  in the outer wall  15  comprises a door  30 ″ which can be opened by mechanical action. In the embodiment shown, the door is formed by a flap made from a resilient, biocompatible material which keeps the window area  14  closed in its normal position. A pull wire  300  is attached to one end of the door  30 ″ in order to allow for opening the door by pulling the pull wire  300 . The pull wire  300  or any other drive connected to the door  30 ″ forms part of the drive unit coupled to the infusion needle  11 . For instance, as is shown in  FIG. 10 , the pull wire  300  may be attached directly to the infusion needle  11  so that advancement of the infusion needle  11  will simultaneously cause the door  30 ″ to be lifted up so that the infusion needle  11  can pass underneath the door  30 ″ and thus penetrate the outer wall  15  easily. Due to the resiliency of the door material, the door  30 ″ will automatically close when the force, such as the pulling force exerted via the pull wire  300 , is released. Instead or in addition, the closing action may be supported by at least one spring element urging the door into its closed position. 
       FIG. 11  shows a fourth embodiment comprising a plurality of infusion needles for each of the two window areas  14 . In this embodiment it is not necessary to provide a turntable by which the needles can be pivoted stepwise in order to laterally displace the needles from one penetration site to a different penetration site within the same window area  14 . Instead, upon successive injection cycles a different one of the plurality of injection needles will be advanced and retracted for each of the two window areas  14 . Thus, the effect achieved is the same as in the embodiment shown in  FIG. 5 . However, instead of the turntable  20  ( FIG. 5 ) a valve V is needed to direct the infusion liquid to only one of the plurality of infusion needles  11  in each of the two window areas  14 . More specifically, depending upon the position of the valve V, a first one of the infusion needles  11  in the first window area  14  and a first one of the plurality of the infusion needles  11  in the second window area  14  will be advanced and retracted simultaneously, and during the next following infusion cycle, another one of the plurality of infusion needles will be advanced and retracted in the two window areas  14 . 
       FIG. 12  shows a fifth embodiment which differs from the first and second embodiments shown in  FIGS. 3 and 4  in that the single infusion needle  11  is not only laterally displaceable in the direction  17  between the two window areas  14  but also laterally displaceable between different penetration sites  21  within the same penetration area  14 . More specifically, the direction of lateral displacement of the tip end of the infusion needle  11  within each of said different penetration areas  14  is perpendicular to the direction of lateral displacement between the different penetration areas  14 . To achieve this result, the drive unit D is configured to longitudinally advance and retract the infusion needle  11  along a direction  16 , to pivot the infusion needle  11  by means of a turntable  20  between the two penetration areas  14  along a pivoting direction  17  and to raise or lower the infusion needle  11  along a third direction  22  perpendicular to the longitudinal direction  16 . A suitable purely mechanical construction may perform this function. However, one or more motors may also be provided to perform one and/or the other of these functions. 
       FIG. 13  shows a sixth embodiment similar to the fifth embodiment shown in  FIG. 12 . In contrast to  FIG. 12 , the infusion needle  11  is not only laterally displaceable between different penetration sites  21  within the same penetration area  14  in a direction perpendicular to the direction of lateral displacement between the two penetration areas  14 , but is also laterally displaceable within the same penetration area  14  in a direction parallel to the direction of lateral displacement between the different penetration areas  14 . In other words, the tip end of the infusion needle  11  is laterally displaceable in two dimensions within the same penetration area  14 . 
       FIG. 14  shows a seventh embodiment which enables the infusion needle  11  to be moved along a three-dimensional, spherically curved array of penetration sites. In this embodiment, a part of the housing  12 , more specifically the window area  14 , is spherically curved and the needle  11  is mounted in a sphere so that upon rotation of the sphere along the directions  17   a  and  17   b  the tip end  13  of the needle  11  can be moved to any position in front of the window area  14 . Once an appropriate position has been adjusted for the tip end  13 , the needle  11  can be advanced on the slide  18  so as to penetrate the window area  14 . Instead of accommodating the slide inside the sphere, it may likewise be mounted on the outer surface of the sphere. Similarly, the infusion needle  11  itself can be mounted on the outer surface of the sphere. The mechanism for moving the sphere along the directions  17   a ,  17   b  can be of many different types, such as mechanical by means of rollers or magnetic. 
       FIG. 15  shows an eighth embodiment similar to the third embodiment shown in  FIG. 5 . That is, two needles  11  are provided in a common housing so as to be longitudinally movable in order to advance and retract the tip ends thereof through the penetration areas  14 . Instead of mounting the infusion needles  11  on a turntable  20 , as in the embodiment of  FIG. 5 , so as to change the injection sites  22  within a penetration area  14  upon each injection cycle, the eighth embodiment of  FIG. 15  achieves the same result by raising and lowering the two injection needles along a direction  22 , similar to the fifth embodiment described above in relation to  FIG. 12 . Again, the result is that the direction of lateral displacement of the tip ends of the two infusion needles  11  within each of the two different penetration areas  14  is perpendicular to the direction of distance between the two different penetration areas  14 . Of course, this embodiment, like the sixth embodiment shown in  FIG. 13 , can also be modified such that the tip ends of the two infusion needles  11  are laterally displaceable in two dimensions within the same penetration area  14 . 
       FIG. 16  shows a ninth embodiment with a principle of advancing and retracting the infusion needle  11  by means of a pull wire  101 . The pull wire  101  is redirected about a pin  102  such that by pulling the wire  101  at an end remotely located somewhere in the patient&#39;s body the tip end of the infusion needle  11  will be advanced through the window of the housing  12 . A helical spring provides a counterforce so that the infusion needle  11  will be retracted once the pulling force on the pull wire  101  is released. This principle can be combined with other embodiments described hereinbefore and hereinafter. Instead of the helical spring  104 , a second pull wire may be provided to retract the infusion needle  11 . It is even possible to use a single pull wire  101  running around two pins  102  in a loop, so that pulling the wire  101  in the one direction or in the other direction will cause advancement or retraction of the infusion needle  11 . 
     The pull wire  101  and the conduit  19  for the infusion liquid are guided in a common sheath  103 . The common sheath  103  has various functions. First, it gives support to the pull wire  101  in bending sections. Second, it facilitates implantation of the conduit  19  along with the pull wire  101 . Third, it protects the pull wire  101  against any build-up of fibrosis. 
       FIG. 17  shows a tenth embodiment which involves remotely actuated pull wires  105 ,  106  guided within a common sheath  103  along with the conduit  19  for the infusion liquid. The pull wires  105  and  106  are directly attached to the infusion needle  11  on opposite sides thereof so that the infusion needle  11  which is mounted on a turntable  20  will be laterally displaced in the one direction or in the other direction depending on whether the wire  105  or the wire  106  is pulled. Instead of using two wires  105 ,  106 , one of the wires may be replaced with a pretensioning means, such as the helical spring  104  in  FIG. 16 . In addition, a further wire, in particular third wire (not shown), may be provided for lateral displacement of the infusion needle  11  in a further direction, so that a two-dimensional lateral displacement can be achieved by pulling the appropriate wires. 
     The pull wires may alternatively be attached to an element other than the infusion needle  11 , provided that the infusion needle  11  is connected to such other element, so that when the other element is moved or turned by pulling one or more of the wires the tip end of the infusion needle  11  will be displaced accordingly. 
     In the case that a long, flexibly bendable needle is provided with the tip end thereof being arranged in a first housing for penetrating the outer wall of the first housing and the other end is arranged in a remotely implanted second housing, one can dispense with the turntable  20  and achieve accurate lateral displacement of the tip end of the needle by pulling the appropriate one of three pull wires which are attached either directly or indirectly to the circumference of the front end of the infusion needle at regularly spaced intervals. 
       FIG. 18  shows an eleventh embodiment with a different principle of advancing and retracting the tip end of the infusion needle, on the one hand, and laterally displacing the tip end of the infusion needle  11 , on the other hand. Instead of pull wires, rotating shafts  107 ,  108  are provided. The drive for driving the rotating shafts  107 ,  108  is remotely located somewhere in the patient&#39;s body. The front ends of the rotating shafts have a threading  109 ,  110 , e.g. in the form of a worm screw, meshing with the teeth of a rack  111 ,  112  formed either directly or indirectly on the infusion needle  11  and on the turntable  20 , respectively. Thus, by turning the rotating shaft  107 , the infusion needle  11  will advance or retract, as the case may be, due to the cooperation of the worm screw  109  and the rack  111 . Similarly, by turning the rotating shaft  108 , the infusion needle  11  will be displaced laterally in the one or the other direction due to the cooperation of the worm screw  110  and the rack  112  of the turntable  20 . Again, the rotating shafts  107 ,  108  are guided in a common sheath  103  along with the conduit  119  for the infusion liquid. 
     In  FIGS. 17 and 18 , the action of the pull wires  105 ,  106  and the rotating shaft  108  make it possible to laterally displace the tip end of the infusion needle  11  between two different penetration areas and/or from a first penetration site to a second penetration site within a single penetration area. 
       FIG. 19  shows a first variation of an overall system comprising any one of the first to eleventh embodiments described above. Specifically shown in the variation shown in  FIG. 19  is a housing  12  with a single infusion needle  11  and a drive unit D as described in relation to  FIG. 12 . The housing  12  is implanted with its windows areas  14  positioned adjacent the corpora cavernosa  6 ,  7 , of which window areas  14  only one is shown in  FIG. 19 . A motor M is contained in the housing  12  for driving the drive unit D. The motor M within the housing  12  is controlled by means of a control unit C 2  constituting the implantable part of a control system which further comprises an external data processing device C 1  by which commands and any other kind of data can be sent to the control unit C 2 . For instance, the external data processing device C 1  may be used to initiate an injection cycle from outside the patient&#39;s body, this being done wirelessly as indicated by arrow  23 . The implanted control unit C 2  not only controls the motor M inside the housing  12  but also controls the energy supply from an accumulator A to the motor M inside the housing  12 . 
     The external data processing device C 1  may likewise be used to program the implanted control unit C 2 . Also, a data transfer port for transferring data between the external data processing device C 1  and the implanted control unit C 2  may be adapted to transfer data in both directions. 
     A feedback sensor F implanted inside the patient&#39;s penis is shown here as being connected to the motor M inside the housing  12  and may likewise be connected to the implantable control unit C 2 . The feedback sensor F can sense one or more physical parameters of the patient, such as the drug level inside the corpora cavernosa, the flow volume through the corpora cavernosa, the pressure inside the corpora cavernosa and the like. Other feedback sensors may be provided at a different location so as to sense process parameters of the system, such as electrical parameters, distention, distance and the like. 
     The conduit  19  connecting the needle  11  with a reservoir comprising compartments R 1  and R 2  and the wiring  24  for transmitting electric energy from the energy source A to the motor M inside the housing  12  are guided through a common conduit  25 . 
     In the variation of the entire system shown in  FIG. 19 , the reservoir comprises a first compartment R 1  with e.g. a saline solution included therein, and a second compartment R 2  with e.g. a drug in powder form or freeze-dried form included therein. A pump P driven by a second motor M 2  is arranged to pump infusion liquid from the reservoir R 1  to the infusion needle  11 . The infusion liquid pumped by the pump P will pass through a mixing chamber  26  into which drugs will be released from the reservoir R 2  in appropriate time coordination. The motor M 2  or a different motor may cause the drugs to be released from the second reservoir R 2 . The motor M 2  is also controlled by the control unit C 2 . Thus, infusion liquid pumped via the pump P from the relatively large first reservoir R 1  through the mixing chamber  26 , in which it is mixed with the drugs released from the second reservoir R 2 , will reach the infusion needle  11  which has meanwhile penetrated the self-sealing window area  14  of the housing  12  and will flow into the corpus cavernosum  7 . 
     In addition to or instead of the control unit C 2 , a pressure sensitive switch for activating the motor M inside the housing  12  and/or the motor M 2  may be arranged subcutaneously. 
     Although the embodiment shown in  FIG. 19  may comprise one of a great variety of reservoir types, a particular reservoir type will now be described. The volume of the reservoir R 1  is divided into two sections by means of a membrane  31 . One section is filled with gas whereas the other section is filled with the infusion liquid (saline solution). An infusion port  32  allows for refilling the reservoir R 1  with infusion liquid by means of a replenishing needle. When the reservoir R 1  is in its full state, the gas section is at ambient pressure or over-pressurized. As infusion liquid is drawn from the reservoir R 1  by means of the pump P upon each infusion cycle, the pressure in the gas section will decrease below ambient pressure, i.e. to a negative relative value. Depending upon the particular type of pump P, it may be advantageous to provide a single acting ball valve to prevent any backflow from the pump P to the reservoir R 1 . 
     There are various ways of providing the motors M and M 2  with energy. In the variation shown in  FIG. 19 , energy is supplied from outside the patient&#39;s body either for direct use by the motors and/or for charging the accumulator A, which may be in the form of a rechargeable battery and/or a capacitor. An extracorporal primary energy source E transmits energy of a first form through the patient&#39;s skin  100  to an energy transforming device T which transforms the energy of the first form into energy of a second form, such as electric energy. The electric energy is used to recharge the accumulator A which provides secondary energy to the motor M upon demand. 
     The external primary energy source E may be adapted to create an external field, such as an electromagnetic field, magnetic field or electrical field, or create a wave signal, such as an electromagnetic wave or sound wave signal. For instance, the energy transforming device T as shown in  FIG. 19  may act as a solar cell, but adapted to the particular type of wave signal of the primary energy source E. The energy transforming device T may also be adapted to transform temperature changes into electrical energy. 
     Instead of the external primary energy source E, an implantable primary energy source E may be used, such as a regular long-life battery instead of the accumulator A. 
     The energy signal may also be used to transmit signals from the external data processing device C 1  by appropriate modulation of the energy signal, regardless of whether the energy is transmitted wirelessly or by wire, the energy signal thereby serving as a carrier wave signal for the digital or analog control signal. More particularly, the control signal may be a frequency, phase and/or amplitude modulated signal. 
       FIG. 20  shows a second variation of the entire system which basically differs from the system of  FIG. 19  only in that the motor M inside the housing  12  is dispensed with. Instead, the motor M 2  is used to drive the drive unit D. This is achieved by means of a rotating shaft  33  in the form of an elastically bendable worm screw, the rotating shaft  30  replacing the wiring  24  of the system shown in  FIG. 19 . 
       FIG. 21  shows a third variation of the entire system which operates purely mechanically. The reservoir R 1  containing the infusion liquid, i.e. the saline solution, is of balloon type, thereby functioning both as a reservoir and as a pump if it is compressed manually from outside the patient&#39;s body. The pressure generated in the reservoir R 1  will act on the reservoir R 2  containing the drug. Upon a certain pressure, the drug will be released from the reservoir R 2  into the mixing chamber  26  and upon further increase of the pressure the infusion liquid will be allowed to enter the mixing chamber  26 , mix with the drug released from the reservoir R 2 , flow towards the infusion needle  11 , and build up pressure in the infusion needle  11  such that the drive unit D is caused to advance the infusion needle  11  through the self-sealing window area  14  into the patient&#39;s corpus cavernosum. Once the pressure is released, the infusion needle  11  will retract automatically due to mechanical spring forces or the like and move into a different position in which it can penetrate the second of the two self-sealing window areas  14  when the reservoir R 1  is compressed again. Where two infusion needles  11  are provided in the housing  12 , a single compressing action on the reservoir R 1  would be sufficient to inject the drug into both the left and right corpora cavernosa. 
       FIG. 22  shows a first principle of how drugs within a plurality of compartments  34  of the reservoir R 2  can be released one at a time by a purely hydromechanical solution. As the infusion liquid is urged from the reservoir R 1  towards the conduit  19  leading to the infusion needle or needles, it is first blocked by a spring-loaded ball valve  34  which opens only when a certain pressure is exceeded. The pressure building up in front of the ball valve  34  is guided by means of a stepper valve V sequentially onto one of a plurality of compartments  35 . The compartments are each formed as a cavity  35  within a piston  36 . Once a certain pressure is exceeded, the piston  36  will be pushed into a position where the compartment  35  is in flow communication with a mixing chamber  26 . In the state shown in  FIG. 22 , three pistons  36  have already been pushed into such position. When the pressure in the reservoir R 1  is further increased, the spring force of the ball valve  34  will be overcome and the infusion liquid urged from the reservoir R 1  towards the conduit  19  will take with it the drug that has been released into the mixing chamber  26 . 
       FIGS. 23 to 25  show a second principle of realizing the reservoir R 2  comprising a plurality of small drug compartments  35 ,  35   a ,  35   b . The drug compartments are integrally formed in a tape  201  which is wound on a first reel  202  and can be unwound from said first reel  202  onto a second reel  203 . The reels  202 ,  203  and the tape  201  are contained in a cassette  200  which may be inserted in the entire system so as to form part of the reservoir. The cassette  200  is preferably replaceable. 
     As can be seen in  FIG. 24 , the compartments  35 ,  35   a ,  35   b  containing the drug e.g. in powder form or freeze-dried form are arranged in a plurality of rows as seen in the transporting direction (indicated by the arrow). However, the compartments  35  of one row are a certain distance offset in the transporting direction from the compartments  35   a  and  35   b  of the other rows. Thus, when the tape  201  is wound from reel  202  to reel  203 , it is guided through a conduit  204  forming part of the cassette  200  through which the infusion liquid is pumped from the reservoir R 1  to the infusion needle or needles, and the compartments  35 ,  35   a ,  35   b  will enter the conduit  204  one after the other. 
     While it is conceivable to open one of the compartments  35 ,  35   a ,  35   b  that has entered the conduit  204  by mechanical action, such as a hammer or piercing element, the opening of the compartments  35  in the embodiment shown in  FIGS. 23 to 25  needs no further action other than winding the tape  201  onto the reel  203 . That is, as can be seen from  FIG. 25 , when the tape  201  enters the conduit  204  through a first slit  205 , the compartments  35  will not be damaged due to the fact that the slit  205  is relatively wide and is closed by two soft sealing lips  206 . However, when the tape  201  exits the conduit  204  on the other side thereof, it will have to pass a narrower second slit  207  with front edges  208  that are not resilient. The compartments  35  will therefore burst on their way out of the conduit  204  when they slip between the edges  208  of the narrow slit  207 . Soft seals  209  in the slit  207  prevent liquid from leaking from the conduit  204 . 
     The entry  210  and the exit  211  of the conduit  204  within the cassette  200  each include a valve that automatically closes when the cassette  200  is removed from the system and automatically opens when the cassette  200  is installed in the system. This allows for replacement of the cassette  200  without adversely affecting the remaining components of the overall system. 
       FIGS. 26 and 27  show a third principle of realizing the reservoir R 2  comprising a plurality of small drug compartments  35 . While  FIG. 26  shows a cross-sectional plan view according to section BB in  FIG. 27 ,  FIG. 27  shows a cross-sectional side view thereof according to section AA in  FIG. 26 . The compartments  35  containing the drug in powder form or freeze-dried form are arranged in a rotatable plate  37 . A motor M 2  is provided to rotate the plate  37  about an axis  38 . The motor M 2  is controlled to advance the plate  37  stepwise so as to bring one compartment  35  at a time in line with the conduit  39  connecting the reservoir R 1  containing the saline solution with the infusion needle or needles. Energy is supplied to the motor M 2  from the accumulator A via the control unit C 1 . 
     The rotatable plate  37  is mounted in a fixed base plate  39  which itself is fixedly mounted in a housing  40  insulating the base plate  39  and the rotatable plate  37  thermally against an outer housing  42 . A cooling device  41  is provided to cool a liquid surrounding the base plate  39  and rotatable plate  37  down to a temperature below 37° C. This serves to protect the drugs inside the compartment  36  from degrading too quickly. The accumulator A supplies the cooling device  41  with energy. 
       FIG. 28  shows a general principle of cooling the reservoir R 2  containing the drug to be cooled. The cooling device  41  may be an electrothermal cooler, i.e. based on the Peltier effect consuming electric energy, or may be of the refrigerator type. Accordingly, the cold part of the cooler  41  is placed on the side to be cooled whereas the warm part of the cooling device  41  is placed on the other side so that the heat energy can be dissipated to the outside. An increased surface  41   a  on the warm side of the cooling device  41  serves to increase heat dissipation. Furthermore, a heat exchanging fluid may be passed through a conduit  41   b  along the increased surface  41   a  to transfer the dissipated heat energy to a remote location within the patient&#39;s body where the heat is dissipated into the patient&#39;s body through a specific heat exchanging surface  41   c.    
       FIG. 29  shows a different principle of cooling, the drugs contained in the reservoir R 2 . In this embodiment, two chemicals X 1  and X 2  are contained separate from each other in respective compartments of the cooling device  41 . When the chemicals X 1  and X 2  are brought together, they will react with each other and such reaction will consume energy which is absorbed as thermal energy from the surroundings. By means of two pistons  41   d ,  41   e , the chemicals X 1 , X 2  are dispensed into a cooling line  41   f  in a controlled manner, which cooling line is preferably in contact with the housing  40  containing the reservoir R 2 . The chemical mixture X 1 -X 2  displaced within the cooling line  41   f  will flow back into the chamber containing the chemicals X 1 , X 2 , but onto the other side of the pistons  41   d ,  41   e.    
     A further embodiment is shown in  FIG. 30 . In this embodiment, again, two separate needles are provided, one needle for each of the left and right corpora cavernosa. However, unlike the previously discussed embodiments, the two needles each have their own housing  12  implanted in the patient&#39;s body with their respective self-sealing window area  14  adjacent the left and right corpora cavernosa, respectively. This principle is shown in  FIG. 31  in more detail with respect to one of the two needles. The drive unit D comprises a piston  50 , to which the hollow infusion needle  11  is attached. The piston  50  separates a first chamber  51   a  in front of the piston  50  and a second chamber  51   b  behind the piston  50 . While the pressure in the first chamber  51   a  corresponds to the pressure exerted by the pump P, the pressure in the second chamber  51   b  can be kept at a lower value. The second chamber  51   b  may be filled with a liquid, such as the infusion liquid, and the liquid may be urged into a flexible volume  52 . The flexible volume  52  could be of simple balloon type so as to fill up without exerting any strong counterforce. 
     Instead of the flexible volume  52 , a conduit  53  may connect the second chamber  51   b  with the reservoir R 1 . Thus, when the needle  11  is advanced, liquid will be dispelled from the second chamber  51   b  through the conduit  53  into the reservoir R 1 , and as the needle  11  is retracted by means of a return spring  55 , liquid will be drawn from the reservoir R 1  through the conduit  53  back into the second chamber  51   b.    
     The injection process is carried out as follows. As the pressure is increased in the first chamber  51   a  by means of the pump P, the needle  11  will be displaced against the force of the spring  55  of the drive unit B. Thus, the tip end  13  of the infusion needle  11  will penetrate through the self-sealing window area  14  press-fitted into the wall  15  of the housing  12  and will further penetrate any fibrosis having built up in front of the housing. When the return spring  55  is completely compressed and the pressure built up by the pump P is further increased, a ball valve  56  will be displaced against a second return spring  57  which is stronger than the first return spring  55 . That way, as long as the pressure is held at a sufficiently high level, infusion liquid will be pumped from the reservoir R 1  through the conduit  19 , the hollow infusion needle  11  and the needle&#39;s laterally arranged exit port into the patient&#39;s body. Upon pressure release, the ball valve  56  will close due to the return springs  55  and  57 , and then the needle  11  will be retracted to its initial position shown in  FIG. 22 . 
     It may be advantageous not to pierce any living tissue by means of the injection needle  11  once it is advanced through the outer wall  15  of the housing  12 . Therefore, as shown in  FIG. 32 , a tube  58  may be placed in front of the window area  14 . The cross-sectional form of the tube  58  may be adapted to the cross-sectional form of the window area  14 , i.e. where the window area  14  is rectangular, the tube  58  likewise has a rectangular cross-section. 
     The exit end of the tube  58  has an open area  59  sufficiently large to prevent growth of fibrosis from spanning over the open area. Fibrosis will slowly grow into the tube along the tube&#39;s inner surface, before it reaches the window area  14  after a relatively long time. The tip end  13  of the needle  11  will therefore not have to penetrate any fibrosis during the first while after implantation of the system. Preferably, the open area  59  has an opening width of at least 3 mm. The length of the tube  58  may be in the range of 4 mm to 30 mm. The opening width  59  and the length of the tube  58  should be adjusted such that the substance injected into the tube  58  can safely seep into the patient&#39;s body. Thus, the longer the tube is, the larger the opening width thereof should be. 
       FIGS. 33A and 33B  show a first embodiment for displacing the tip end of the infusion needle  11  in two or more different directions, i.e. a two-dimensional displacement. More specifically,  FIG. 33A  shows a plan view, whereas  FIG. 33B  shows a side elevational view schematically. As can be seen, a plate  60  to which the infusion needle  11  is fixedly mounted has a projection  61  extending into a frame  62  within which the projection  61  is free to move in any direction. Electromagnetic coils  63  are mounted on the sides of the frame  62  and are individually energizable. The electromagnetic coils  63  constitute the first part of an electromagnetic drive whereas the projection  61  is configured to constitute the second part of the electromagnetic drive. Thus, when one or more of the electromagnetic coils are energized, an electromagnetic field is created in the frame  62  and the electromagnet second part, i.e. the projection  61 , will adjust its position within such field accordingly. Due to the fact that the infusion needle  11  is fixedly mounted to the plate  60 , the infusion needle  11  will move along with the projection  61 . This way, the infusion needle  11  can be advanced and retracted and can also be displaced laterally. 
     Of course, the infusion needle  11  may be attached to the electromagnetic drive in a different manner, e.g. perpendicular to the plane defined by the electromagnetic coils  63  (rather than in parallel as in  FIG. 33B ). As a result, the infusion needle would be laterally displaceable in a plurality of directions (rather than being advanceable and retractable). 
     Alternatively, the electromagnetic drive may be such as to displace the infusion needle in any lateral direction and, in addition, to advance and retract the infusion needle. This can be achieved e.g. with a structure as schematically shown in  FIG. 33C  relating to a second embodiment for displacing the tip end of the infusion needle  11 .  FIG. 33C  shows an elevational side view similar to  FIG. 33B , but the electromagnetic coils  63  do not define a single plane, but rather a plurality of planes is defined one above the other by providing additional electromagnetic coils  63  in a vertical direction. The top plan view would be similar to  FIG. 33A . This way, the electromagnet second part  61  fixedly connected to the needle  11  moves within a three-dimensional frame  62  depending on the energization of respective ones of the magnetic coils  63 . 
       FIGS. 34A and 34B  show a plan view and a side view of a third embodiment of an electromagnetic drive for moving the infusion needle  11  in a plurality of directions. In this embodiment, the electromagnetic coils  63  constituting the electromagnet first parts are arranged in a first plane and the electromagnet second part constituted by the protrusion  61  fixedly connected to the infusion needle  11  via the plate  60  is movable in a plane in front of or behind the plane defined by the electromagnet first parts. However, the electromagnetic coils  63  are oriented differently in this third embodiment. Again, depending upon the energization of the individual electromagnetic coils, the electromagnet second part, i.e. the protrusion  61 , will adjust its position in the created electromagnetic field within the frame  62 . 
     A method of treating a human being (or an animal) by implanting at least part of the system in the patient&#39;s body comprises the steps of cutting the skin, dissecting free a first area near the left and right corpus cavernosum, placing the at least one housing accommodating the at least one infusion needle within said dissected area such that the tip end of the at least one infusion needle, when penetrating the housing&#39;s outer wall, can penetrate into the left and right corpus cavernosum and/or the two deep arteries of the right and left corpus cavernosum and/or into muscle tissue regulating blood flow to the patient&#39;s left and right corpus cavernosum and/or into another kind of tissue in close proximity to the patient&#39;s left and right corpus cavernosum allowing stimulation of erection of the two corpora cavernosa, and finally closing at least the skin after implantation of at least parts of the system. 
     Where parts of the system are implanted remote from the corpora cavernosa, a second area remote from the first area may be dissected free in order to place e.g. the at least one reservoir in the patient&#39;s body at the remote second area, with a conduit connecting the reservoir with the at least one infusion needle accommodated in the at least one housing. In this case, it is preferable to place the reservoir adjacent the patient&#39;s symphyseal bone. 
     One or more of the following elements may be placed within the patient&#39;s body remote from the housing or housings accommodating the at least one needle:
         at least one drive unit for advancing and retracting the tip end of the infusion needle,   a pump (P) for advancing the substance from the reservoir to the at least one infusion needle, at least one motor (M, M 2 ) for actuation of the drive unit (D) or a drive driving the drive unit, and/or the pump (P) or any other energy consuming part of the system,   energy storage means (A) for providing the at least one motor with energy,   galvanic coupling elements between either an external energy source (E) or the energy storage means (A) and the motor (M, M 2 ) for transmitting energy to the motor in contacting fashion,   wireless coupling elements adapted to connect either the motor (M, M 2 ) or the energy storage means (A) or both to an extracorporal primary energy source for transmitting energy to either the motor or the energy storage means or both in non-contacting fashion,   control unit (C 1 ) for controlling the motor (M, M 2 ),   a data transmission interface for wirelessly transmitting data from an external data processing device (C 2 ) to the control unit (C 1 ),   the feedback sensor (F),   wireless energy transforming means, and   the injection port ( 32 ) for refilling the reservoir (R 1 ).