Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1999-04-13
2001-03-06
Nguyen, A. T. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S191000
Reexamination Certificate
active
06197000
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to injection systems, to pump systems for use therein and to a method of using such pump systems, and, particularly, to injection systems and to pump systems used to pressurize fluids for use in medical procedures and to a method of using such pump systems.
BACKGROUND OF THE INVENTION
In many medical procedures, such as drug delivery, it is desirable to inject a fluid into a patient. Likewise, numerous types of contrast media (often referred to simply as contrast) are injected into a patient for many diagnostic and therapeutic imaging procedures. For example, contrast media are used in diagnostic procedures such as X-ray procedures (including, for example, angiography, venography and urography), CT scanning, magnetic resonance imaging (MRI), and ultrasonic imaging. Contrast media are also used during therapeutic procedures, including, for example, angioplasty and other interventional radiological procedures. Regardless of the type of procedure, any fluid injected into the patient must be sterile and contain a minimum of pyrogens.
A number of substantial problems arise in the use of current pumping systems and methods for injecting fluid into a patient's body. For example, it is often difficult to accurately control the pressure and flow rate of the fluid exiting the pumping system. In relatively low pressure applications, for example, peristaltic pumps have long been used. However, peristaltic pumps are difficult to control with accuracy.
In the case of relatively high pressure applications, such as CT and angiography, mechanized syringe injectors are used. The use of mechanized syringe injectors also results in a number of substantial drawbacks. Current mechanism for powering and controlling syringe pumps are complicated, inefficient and costly. Expensive and bulky pressure jackets for housing the syringe pumps are often required to prevent failure at high pressures. Syringe pumps are severely limited in that the maximum volume that can be injected at one time is the volume of the syringe. Disposable syringe pumps are costly. Moreover, the flow rate acceleration of syringe injectors is limited by the inertia of the extensive drive train required to translate motor rotation into syringe plunger motion.
These and other drawbacks in currently available syringe pumping systems create and magnify a number of inefficiencies in current procedures for injecting contrast media. For example, a number of factors, including, but not limited to, the procedure to be performed and the size of the patient, determine: (i) the contrast to be used, (ii) the concentration thereof, and (iii) the amount to be injected. Under current practice of injecting contrast media via syringe pumping systems, hospitals must purchase and stock many contrast media concentrations in multiple container sizes in an attempt to provide the correct concentration and amount of a specific contest for a specific procedure, while minimizing the wastage of contrast. In that regard, contrast is typically very expensive.
Thus, most contrast media are provided by manufacturers in numerous concentrations in sterilized containers (such as glass bottles or plastic packages) ranging incrementally in size from 20 ml to 200 ml. These containers are generally designed for a single use (that is, once a container is opened for a patient, it is used for that patient only). The contrast is generally aspirated from such containers via the syringe pump used to inject the contrast, and any contrast remaining in the container is discarded to prevent injection with potentially contaminated contrast. The hospital staff is faced with the task of choosing an appropriately sized contrast container to assure an optimum study while minimizing discarded contrast. Time consuming procedures are required to reload the syringe if more contrast is required than originally calculated. On the other hand, expensive waste results if only a portion of a filled syringe is injected. The inventory of contrast containers required under the current system increases costs and regulatory burdens throughout the contrast media supplier-consumer chain.
Many of these costs, regulatory burdens and other problems associated with the use of multiple contrast containers can be substantially eliminated through use of relatively large contrast media containers for single- and multiple-patient use in connection with a pumping system allowing any volume and concentration of contrast to be injected as determined by the hospital staff before or during a procedure. Current syringe pumping systems simply do not provide a sufficiently cost-effective and efficient pumping system to provide optimal pressurization for injection of contrast and other liquid media.
It is, therefore, very desirable to develop injection systems and pump systems that reduce or eliminate the limitations associated with current injection systems and pump systems.
SUMMARY OF THE INVENTION
The present invention provides a pump system for use in pressurizing a liquid medium for injection into a patient. In general, the pump system comprises a pressurizing unit having at least one chamber. The pump system may also include a dampening chamber in fluid connection with the outlet flow of the pump system to decrease the pulsatile nature of the flow.
Each chamber has disposed therein a pressurizing mechanism to pressurize liquid medium within the chamber. Preferably, the pressurizing mechanism pressurizes the liquid medium via positive displacement thereof through generally linear motion of the pressurizing mechanism within the chamber. Through reciprocating linear motion of the pressurizing mechanism (for example, a piston), the liquid medium is alternatively drawn into the chamber from a source of liquid medium (for example, a container) and forced out of the chamber at a desired pressure.
Generally linear, reciprocating motion can be provided by a number of pressurizing mechanisms including, but not limited to, pistons. Generally linear reciprocating motion can also be provided by a flexing element such as a diaphragm disposed within the chamber. In positive displacement of the liquid medium, there is generally to one-to-one correspondence between the length of the generally linear stroke of the pressurizing mechanism and the amount of liquid medium displaced. Positive displacement through generally linear motion provides better volumetric efficiency than achievable through the use of rotational pumps. Volumetric efficiency can be defined as the volume of fluid actually per unit mechanical displacement divided by the theoretical volume of fluid delivered per unit mechanical displacement. The volumetric efficiency of rotational pumps is undesirably dependent upon the pressure and flow rate of the liquid medium.
Each chamber comprises an inlet port and an outlet port. The pump system also preferably comprises an inlet port check valve in fluid connection with each inlet port which allows the liquid medium to flow into the chamber through the inlet port, but substantially prevents the liquid medium from flowing out of the chamber through the inlet port. Likewise, the pump system preferably comprises an outlet port check valve in fluid connection with each outlet port which allows pressurized liquid medium to flow out of the chamber through the outlet port, but substantially prevents the liquid medium from flowing into the chamber through the outlet port. Each inlet port is connected to a source of liquid medium. Each inlet port can be connected (i) to a common source of liquid medium, or (ii) to different sources of varying liquid mediums in the case that mixing of varying liquid mediums is desired. If the volume displaced in each stroke is maintained relatively small, liquids of widely varying viscosity and density can be mixed without the use of mixing devices (for example, mechanical stirrers or rotary vane mixers) other than the present invention. Each outlet port is connected to a common outlet line for transmitting pressurized liquid medium to be injec
Hirschman Alan D.
Reilly David M.
Bartony Henry E.
Bradley Gregory L.
Medrad Inc.
Nguyen A. T.
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