Injector having low input power

A powered injector that stores energy at a low rate when not in use and delivers energy at a high rate during injection. Energy may be stored in a highly responsive energy storage device, such as a capacitor, for rapid delivery of power to the injector motor. In certain embodiments, wires connecting the powered injector to a power supply may be relatively small and inexpensive because the current and voltage loads placed on the wires are relatively low.

FIELD OF THE INVENTION

The invention relates generally to powered injectors for injecting medical fluid and, more specifically, to powered injectors that have a low input power level relative to an output power level thereof.

BACKGROUND

Generally, a powered injector is used to inject medical fluid, such as a pharmaceutical or a contrast agent, into a patient. Typically, a motor in the powered injector is utilized to drive a plunger of a syringe forward to inject medical fluid therefrom. A power supply generally provides energy to the motor. Frequently, the power supply is remote from the powered injector to reduce the likelihood of electromagnetic emissions from the power supply interfering with other medical equipment, such as medical imaging equipment.

Unfortunately, supplying power to the motor often presents design challenges to manufacturers of powered injectors. The motor often consumes energy at a high rate while moving the plunger of the syringe. Wires between the power supply and the motor are typically utilized to carry large currents and/or voltages to supply sufficient power to the motor. Wires having sufficient capacity to deliver this power are often expensive. This expense may be attributed to the thickness of the wires and/or high-cost materials utilized to construct such wires. For instance, wires suitable for high voltages often include expensive insulation. Further, because the power supply is often remote from the powered injector, the wires connecting the two are often very long. Thus, wires for delivering high power to the powered injector may add significant cost to a design.

SUMMARY

In certain aspects, the present invention generally relates to a powered injector that gradually stores energy at a low rate (e.g., at low power) when not in use and then quickly delivers energy at a high rate (e.g., at high power) during operation (e.g., during an injection procedure). Energy may be stored in a highly responsive energy storage device, such as a capacitor, for rapid delivery of power to the motor. In certain embodiments, wires connecting the powered injector to a power supply may be small and inexpensive (relative to conventional wire interconnections between injectors and power supplies) because the current and voltage loads placed on the wires are low (again, relative to conventional wire interconnections between injectors and power supplies).

A first aspect of the invention is directed to a powered injector that includes an energy storage device having a power input and a power output, a motor coupled to the power output of the energy storage device, and a ram that is coupled to the motor and that has a syringe plunger interface. The current carrying capacity of the power output of the energy storage device is greater (and in some cases, substantially greater) than the current carrying capacity of the power input of the energy storage device.

A second aspect of the invention is directed to an electric injector for use with a syringe having medical fluid (e.g., contrast media, radiopharmaceutical, saline, etc.) therein. This injector includes a plurality of supercapacitors coupled to one another in series, a motor coupled in parallel to the plurality of supercapacitors, and a syringe interface coupled to the motor.

Yet a third aspect of the invention is directed to a method of operation for a medical fluid injector. In this method, input power is received by the injector from a power supply at an input wattage. The input power is stored by the injector. Subsequently, discharge power is output by the injector at an output wattage that is at least twice as great as the input wattage.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

When introducing elements of various embodiments of the present invention, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, the use of “top”, “bottom”, “above”, “below” and variations of these terms is made for convenience, but does not require any particular orientation of the components. Further, as used herein, the terms “high power” and “low power” refer to power levels that are high or low relative to one another, rather than power above or below an absolute threshold level. The term “coupled” refers to a condition in which two or more objects are in direct contact or are interconnected (i.e., either directly or indirectly connected). The phrase “fluidly coupled” refers to a condition in which two or more objects are coupled in a manner such that fluid can flow from one object to another.

FIG. 1illustrates an exemplary injection system10having a powered injector12coupled to a power supply14by a power cable16. Advantageously, certain embodiments may include a relatively low cost power cable16. As explained further below, the exemplary powered injector12ofFIG. 1stores energy delivered at a relatively low input power level, thereby potentially reducing the peak power carried by the power cable16. Subsequently, the powered injector12uses the stored energy at a high output power level during an injection. Certain embodiments may include relatively small, inexpensive, and/or long cables that carry power to the powered injector. Some of these embodiments may facilitate remote placement of the powered injector relative to a power source. Prior to addressing the powered injector12in detail, features of the power supply14are explained.

The power supply14ofFIG. 1includes a power regulator18and a rectifier20. The power regulator18may include or be referred to as a current limiter, a transformer, or a power source controller, and the rectifier20may be referred to or include an alternating current (AC) to direct current (DC) converter. The power regulator18may have an AC power regulator, such as a silicon controlled rectifier and control circuitry, and/or a DC power regulator, such as a switching regulator, or a current or voltage divider. In certain embodiments, the rectifier20may have a low-pass filter and half-wave rectifier or a full-wave rectifier. Further, some embodiments may include a band-pass filter to reduce the likelihood of high and low frequency electromagnetic signals reaching the powered injector12. The power supply14may couple to a source of power, such as a power grid22.

In the illustrated embodiment, the powered injector12includes protection circuitry24, an energy storage device26, a controller28, a motor30, a ram32, and a syringe34. The protection circuitry24may include devices adapted to limit the magnitude of currents flowing into the energy storage device26, such as a fuse, a circuit breaker, or a current divider.

The energy storage device26may include or be referred to as a local energy source, a local energy storage, an on-board power supply, and/or an integrated power source. The energy storage device26may include a variety of devices configured to receive, store, and supply energy. For instance, the energy storage device26may include a capacitor, such as a supercapacitor (e.g., available from Maxwell Technologies of San Diego, Calif.). As used herein, the term “supercapacitor” refers to a capacitor having a gravimetric energy density greater than 0.4 Joules per gram. In some embodiments, the energy storage device26may include a capacitor exhibiting a capacitance greater than or equal to 1 farad, 10 farads, 30 farads, 100 farads, 200 farads, 300 farads, 350 farads, 500 farads, 1000 farads, 1500 farads, 2000 farads, or even more. Alternatively or additionally, the energy storage device26may include a battery, such as a lead-acid battery, a lithium ion battery, a lithium ion polymer battery, a nickel-iron battery, a nickel metal hydride battery, a nickel cadmium battery, a sodium metal chloride battery, or a nickel-zinc battery.

The controller28may include circuitry and/or code adapted to control a flow of energy from the energy storage device26to the motor30of the injector12. In some embodiments, the controller28may include logic circuitry, such as a central processor, a digital signal processor, an application specific integrated circuit, a microcontroller, or the like. The controller28may be equipped with a switch capable of preventing or modulating the flow of current from the energy storage device26in response to signals from the logic circuitry. For instance, certain embodiments may include an integrated gate bi-polar transistor (IGBT), a bipolar junction transistor, a metal oxide semiconductor field effect transistor (MOSFET), a mechanical relay, a solenoid, or a solid state relay. The controller28may include or couple to a user interface through which a user may signal the controller28to initiate an injection. For example, the user interface may include a graphical user interface.

In the illustrated embodiment, the motor30and ram32may include a variety of devices for converting electrical energy into a desired form of mechanical energy. For instance, the motor may include various types of electric motors, such as a stepper motor, a brush DC motor, a brushless DC motor, a linear motor, or a piezoelectric drive. The ram32may include a syringe interface and a transmission. The syringe interface may include or be referred to as a plunger interface, a pushing surface, and/or a pressure applicator. The transmission may include or be referred to as a drive, a gear-box, a rotation-to-linear motion transmission, and/or a motor-syringe mechanical interface.

The syringe34of the illustrated embodiment may include a plunger, a barrel, and medical fluid disposed within the barrel. The medical fluid in the syringe may be any appropriate medical fluid such as, but not limited to, saline, a contrast agent, a pharmaceutical, a radiopharmaceutical, or a combination thereof. In the current embodiment, the plunger is disposed within the barrel, and together, the plunger and barrel house the medical fluid. A backside of the plunger may include a surface and/or structure designed/configured to interface with the syringe interface of the ram32.

The protection circuitry24is shown as being electrically disposed (i.e., positioned with reference to a flow of electrons) between the energy storage device26and the power supply14, and the controller28is shown as being electrically disposed between the energy storage device26and the motor30. The protection circuitry24may serially couple to the power cable16and the energy storage device26. The energy storage device26may be serially coupled to the motor30via the controller28. The controller28may also couple to the protection circuitry24. The motor30may mechanically connect to a transmission of the ram32, and the ram32may be designed to interface with (e.g., mechanically couple to) the plunger of the syringe34via the syringe interface.

The powered injector12ofFIG. 1may be fluidly coupled to a patient36or other organism via a conduit and a hollow, hypodermic needle. In certain embodiments, an imaging device38(may be utilized to image the patient36during and/or after injection of medical fluid into the patient36. The imaging device38may refer to or include a variety of imaging systems such as a projection radiography system (e.g., an x-ray system), a fluoroscopy system, a tomography system (e.g., a computed axial tomography system), a magnetic resonance imaging (MRI) system, and/or an ultrasound system.

In some embodiments, the powered injector12, the patient36, and the imaging device38may be remote from the power supply14. For instance, in the injection system10ofFIG. 1, they are in separate rooms, with the power supply14disposed in a facilities room40and the other components in an imaging room42. In certain embodiments, to extend between these rooms40,42, the power cable16may be longer than 1 meter, 2 meters, 3 meters, 6 meters, 10 meters, 20, meters, 50 meters, or more. The imaging room42may include various forms of shielding, such as electromagnetic shielding, to isolate the imaging device38from some sources of interference. In some embodiments, the imaging room42may be generally free of ferrous materials that might be attracted to magnets and/or cause image artifacts in an MRI machine. Advantageously, by positioning the power supply14remote from the powered injector12, the injection system10may tend to reduce interference with the imaging device38from the power supply14.

Turning toFIG. 2, the exemplary energy storage device26is depicted in greater detail. The illustrated energy storage device26includes a bank of supercapacitors44coupled in series. The present embodiment includes fifteen supercapacitors44, but other embodiments may include any appropriate and/or desired number of supercapacitors. For instance, some embodiments include more than one supercapacitor, more than two, more than three, more than four, more than five, more than ten, more than twenty, more than fifty, or even more than one hundred supercapacitors. The serially connected supercapacitors44, when fully charged, output a current of approximately 40 amps at an aggregate voltage of approximately 38 volts. In other words, the energy storage device26outputs approximately 1500 watts of power. Other embodiments of the energy storage device26provide output of other appropriate wattages. For instance, in some embodiments, the energy storage device26may output more than 500 watts, more than 700 watts, more than 1000 watts, more than 1200 watts, more than 1500 watts, more than 1700 watts, more than 2000 watts, more than 2500 watts, or even more.

To carry this power, in some embodiments, a power output46of the energy storage device26may couple to a high current (or voltage) capacity conductor48. In certain embodiments, the conductor48may be a low gauge wire of relatively short length (e.g., a 10 to 14 AWG gauge wire of less than about two feet in length). That is, the conductor48may have a conductive portion with a cross-sectional area greater than or equal to about 3.3×10−3square inch, greater than or equal to about 5.2×10−3square inch, greater than or equal to about 8.2×10−3square inch, or greater than or equal to about 1.3×10−2square inch.

In contrast, the wires connecting the energy storage device26and the power system14, including the power cable16, may have a much lower current carrying capacity than the conductor48. For example, the power cable16may be embodied by a 25-pin cable with a D-shell pin connector and 22 gauge wires (wire having a diameter of about 2.5×10−2inch). In certain embodiments, the power cable16may include or consists essentially of a wire or wires having a conductive portion with a cross-sectional area less than or equal to about 2.6×10−3square inch, less than or equal to about 1.2×10−3square inch, less than or equal to about 8.0×10−4square inch, less than or equal to about 5.0×10−4square inch, less than or equal to about 2.5×10−4square inch, or less than or equal to about 1.6×10−4square inch. The power cable16may couple to a power input50of the energy storage device16. In some embodiments, five wires of the cable16may carry a ground voltage and five wires may conduct current driven by a DC voltage less than 42 volts through the power input50. Advantageously, the power cable16and electronics in the power supply14may be less expensive than components adapted to deliver1500watts of power the entire distance from the power supply14to the motor30.

FIG. 3is an elevation view the exemplary powered injector12. As illustrated byFIG. 3, the powered injector12includes a stand assembly52, a support arm54, and a power head56. The illustrated stand assembly52includes four sets of wheels58, a chassis60, vertical supports62, a handle64, and a display66. The vertical supports62may elevate the handle64, display66, and support arm54above the chassis60, and, in certain embodiments, it may have a recessed portion through which the power cable16is routed. The display66may include a liquid crystal display, a cathode ray tube display, an organic light emitting diode display, a surface emission display, or other appropriate display, and it may be coupled to the controller28.

The support arm54of the injector12shown inFIG. 3includes multi-axis articulating members68,70. The illustrated articulating member68has two degrees of freedom relative to the chassis60due to two perpendicular axes of rotation72,74. Similarly, the exemplary articulating member70has two degrees of freedom relative to the articulating member68by virtue of two perpendicular axes of rotation76,78. The power cable16is shown as being routed along the articulating members68,70to the power head56.

The power head56ofFIG. 3couples to the articulating member70via a joint that provides two degrees of freedom relative to the articulating member70. As a result, in the present embodiment, the power head56may rotate about axes80,82. In total, the illustrated power head56has six degrees of freedom relative to the chassis60. Other embodiments may include more or fewer degrees of freedom.

The power head56includes a display84, a fluid control bar86, and an air detector88. The fluid control bar86facilitates manual manipulation of the plunger in the syringe34, and the air detector88signals the controller28when air is detected leaving the syringe34.

In the present embodiment, the power head56houses the protection circuitry24, the energy storage device26, the controller28, the motor30, the ram32, and a portion of the syringe34. In other embodiments, a number of these components or a portion of these components may be distributed elsewhere on the powered injector12or elsewhere in the injecting system10(FIG. 1).

The powered injector12may operate according to an exemplary injection process90depicted byFIG. 4. The energy storage device26receives energy at low power, as depicted by block92. In some embodiments, the energy storage device26may receive this energy via the power cable16from the power supply14. During this step92, a charging current may flow through the power input50of the energy storage device26. The charging current may be delivered at low power, such as less than 500 watts, less than 400 watts, less than 300 watts, less than 200 watts, less than 100 watts, less than 50 watts, less than 10 watts, or even less. As energy is delivered by the power cable16, it may be stored in the energy storage device26, as depicted by block94. For example, a charge may build on plates of the capacitors44. In some embodiments, the energy storage device26may be charged through induction (e.g., in cordless embodiments).

Next in the exemplary injection process90, the energy storage device26delivers energy to the motor30at high power, as depicted by block96. For example, the controller28may close a current path through the conductor48by energizing a gate of a solid state switching device, and the capacitors44may discharge through the power output46and the conductor48. In certain embodiments, the energy storage device26may deliver energy at a rate of more than 700 watts, more than 800 watts, more than 1000 watts, more than 1200 watts, more than 1400 watts, more than 1500 watts, more than 1700 watts, more than 2000 watts, more than 3000 watts, more than 5000 watts, or more.

As depicted by block98, the injection process90includes injection of a medical fluid. In the powered injector12ofFIGS. 1-3, current from the energy storage device26powers the motor30, and the motor30drives the ram32. The ram32, in turn, pushes a plunger of the syringe through the barrel of the syringe34, and pushes the medical fluid out of the syringe and into the patient36. The medical fluid may include any appropriate medical fluid such as a contrast agent, a pharmaceutical, a radiopharmaceutical, saline, or a combination thereof.

FIG. 5depicts another exemplary injection process100that may be performed by the injection system10ofFIGS. 1-3. The injection process100begins with receiving power from a power grid22, as depicted by block102, and, then, rectifying the power from the grid22, as depicted by block104. As an example, the rectifier20in the embodiment ofFIG. 1may rectify the power from the grid22. Next, in the present embodiment, the power regulator18regulates the rectified power to produce low-level power, as depicted by block106. The power cable16conducts the low-level power over a distance, such as between rooms40,42, as depicted by block108.

The powered injector12may store and expend the energy delivered via the power cable16. In the present embodiment, the low-level power may be conducted through an input50of the energy storage device26, as depicted by block110ofFIG. 5, and a capacitor44may be charged by a current carrying the low-level power, as depicted by block112ofFIG. 5. Next, the controller28of the present embodiment may receive a signal to inject a fluid, as depicted by block114ofFIG. 5. For instance, a user may press a button to initiate injection, and the button may transmit a signal to the controller28. At this point, in some embodiments, the controller28may verify that the energy storage device26has stored sufficient energy to proceed with the injection. After the energy storage device26is partially charged, charged above a threshold value, or fully charged, the controller28may close a path through conductor48to conduct high-level power through output46of the energy storage device26, as depicted by block116ofFIG. 5. The motor30may receive the high-level power and drive the plunger of the syringe34via the ram32, as depicted by block118ofFIG. 5. As a result, medical fluid is expelled from the syringe34(e.g., injected into the patient36), as depicted by block120ofFIG. 5. Finally, in some embodiments, the patient36may be imaged, as depicted by block122ofFIG. 5, for instance, with one of the imaging systems discussed in reference to imaging device38inFIG. 1.

FIG. 6illustrates an exemplary cordless injector306having an energy storage device302capable of being coupled to a docking station300. As used herein, the term “cordless” refers to the capacity to operate without an external connection to a source of electrical power. The injector306may include one or more of the features of the previously discussed powered injector12. The injector306features a shielded syringe assembly308, shielding310, a syringe drive312, a docking station electrical interface314, and a docking station mechanical interface315. The docking station electrical interface314includes a plurality of leads332,333,334,335. These leads and/or others may be utilized in charging the injector306and/or as a communication link to enable the injector to communicate data to and/or through the docking station300. In some embodiments, the injector306may be able to communicate data to and/or through the docking station300(e.g., to be conveyed to an imaging system and/or a hospital information system) via wireless communication (e.g., radio frequency).

In the present embodiment, syringe assembly308includes a syringe316and shielding318. The illustrated syringe316includes a needle320, a barrel322, a plunger324, and a push rod326having an outer end328. One or more fluids330may be disposed within the barrel322of the syringe316. For example, the fluid330may include a radiopharmaceutical, a contrast agent, saline, a pharmaceutical, or a combination thereof. The syringe316may exhibit any of a number of appropriate designs/configurations. For instance, in some embodiments, the syringe316may be a single stage syringe, a two stage syringe with different fluids in each stage, a multi-barrel syringe, or a syringe having more than two stages and/or more than two fluids.

The shielding310,318of the injector306may include electromagnetic shielding, radiation shielding, thermal shielding, or some combination thereof. In some embodiments, the shielding310,318may feature radiation shielding materials, such as lead, depleted uranium, tungsten, tungsten impregnated plastic, etc. Alternatively or additionally, shielding310,318may include electromagnetic shielding materials, such as a layer, mesh, or other form of copper, steel, conductive plastic, or other conductive materials. In certain embodiments, the shielding310,318may be substantially or entirely nonferrous. The shielding310may entirely envelope the syringe316, the syringe drive312, and/or the energy storage device302; substantially envelope one or more of these components316,312,302; or partially envelope one or more of these components316,312,302. Similarly, the shielding318may entirely, substantially, or partially envelope the syringe316. Some embodiments of the injector302may not include shielding310and/or318, which is not to suggest that any other feature discussed herein may not also be omitted.

The syringe drive312of the injector306may include a piezoelectric drive, a linear motor, a shape memory alloy, a rack-and-pinion system, a worm gear and wheel assembly, a planetary gear assembly, a belt drive, a gear drive, a manual drive, a hydraulic drive, and/or a pneumatic drive. For example, in the embodiment ofFIG. 8, discussed below, the syringe drive312may include an electric motor and a screw drive. In some embodiments, the syringe drive312may be entirely, substantially, or partially non-ferrous.

The docking station300for the injector306includes a complementary electrical interface336, a complementary mechanical interface338, and a power cable340. The complementary electrical interface336includes a plurality of female connectors342,343,344,345. The power cable340may be adapted to receive power from a power source, such as a low wattage DC power source. Moreover, the docking station300may be mounted on a movable stand, a rotatable arm, a vehicle (e.g., ambulance), an imaging device, a patient table, a wall mount, or another suitable mount.

In operation, the cordless injector306is complementarily designed to mate with the docking station300. Specifically, the docking station mechanical interface315of the injector306is designed to mate with the complementary mechanical interface338of the docking station300, and the docking station electrical interface314of the injector306is designed to mate with the complementary electric interface336of the docking station300. Energy flows through the power cable340, through the female connectors342,343,344,345, and into the male connectors332,333,334,335at low power. The low power energy flows into the energy storage device302. In some embodiments, the energy storage device302may be charged while the injector is being utilized in a syringe filling procedure. For instance, while the energy storage device302is charging, the syringe drive312may apply force331that draws the plunger324away from the needle320within the barrel322, thereby tending to pull fluid into the barrel322. During filling, in situ or ex situ feed-forward or feed-back control may be exercised over the fill rate and/or fill volume.

When the energy storage device302is charged or energized, the cordless injector306may be removed from the docking station300and used to inject a radiopharmaceutical330or other appropriate medical fluid without power cables interfering with the procedure. Injection may be performed at the same site at which the cordless injector306is filled and charged, or the cordless injector306may be shipped in a charged and filled state for use at another site. During injection, energy may flow at a high rate from the energy storage device302to the syringe drive312, which applies force331to the outer end328of the push rod326. The push rod326drives the plunger324through the barrel332toward the needle320and, thus, causes the fluid330to be expelled from the syringe316. During expulsion (e.g., injection) of the fluid330, in situ or ex situ feed-forward or feed-back control may be exercised over the rate and/or volume of injection.

FIG. 7illustrates an exemplary cordless injector348capable of accommodating a plurality of (here, two) syringes. The cordless injector348includes a secondary syringe350and a secondary syringe drive352. The secondary syringe350may be shielded and may include fluid354, which may be one or more of the medical fluids mentioned herein. The secondary syringe350may be within shielding310, but in other embodiments, the secondary syringe350may be partially or entirely external to shielding310. While the syringes shown inFIG. 7are illustrated as being separate and distinct from one another, other embodiments of the injector348a capable of accommodating multi-barrel syringe assemblies (e.g., a substantially unitary, two-barreled syringe assembly).

In operation, the syringe drive352of the injector348may apply a force354to the plunger of the secondary syringe350and cause the fluid354to be drawn into or pushed out of the secondary syringe350. In some embodiments, syringe drive312and secondary syringe drive352may be partially or entirely integrated into a single syringe drive. Alternatively, the syringe drive312and the secondary syringe drive352may be independent syringe drives. During injecting and/or filling, independent, in situ or ex situ feed-forward or feed-back control over the flow rate and/or volume of fluids330and/or354injected or filled by the cordless injector348may be exercised.

FIG. 8illustrates an exemplary syringe drive312within the cordless injector306. The illustrated syringe drive312includes an electric motor356, a transmission358, and a linear drive360. The electric motor356may be a DC electric motor or an AC electric motor, such as a stepper motor. The illustrated transmission358includes a primary pulley362, a secondary pulley364, and a belt366. The present linear drive360has an externally threaded shaft, worm, or screw368, a bushing370, an outer shaft372, and a syringe interface374. The transmission358may have a ratio of the diameter of the secondary pulley364to the diameter of the primary pulley362of greater than 0.5:1, greater than 1.0:1, greater than 1.5:1, greater than 2:1, greater than 3:1, greater than 4:1, greater than 5:1, greater than 8:1, greater than 20:1, or more. The syringe interface374includes a wider, outer-end receptacle376and a shaft slot378. In some embodiments, one or more of the motor356, transmission358, and drive360may be substantially or entirely non-ferrous. In some embodiments, one or more of the motor356, transmission358, and drive360may be partially, substantially, or entirely shielded by shielding310.

In operation, the electric motor356of the injector306drives the primary pulley362. As the primary pulley362rotates, the belt366rotates the secondary pulley364. The rotation of the secondary pulley364drives the screw368, which rotates within the bushing370. The bushing370is threaded so that rotation of the screw368applies a linear force to the bushing370. A linear sliding mechanism may prevent rotation of the bushing370while permitting the bushing370to translate up and down the screw368. As the screw368rotates, the outer shaft372may be pulled down the screw368or pushed up the screw368by the bushing370. The outer shaft372may linearly translate relative to the screw368and move the plunger of the syringe316via the syringe interface374.

While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the figures and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.