Surgery – Instruments – Cutting – puncturing or piercing
Reexamination Certificate
2001-06-21
2003-09-09
Milano, Michael J. (Department: 3731)
Surgery
Instruments
Cutting, puncturing or piercing
C604S294000
Reexamination Certificate
active
06616677
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to liquid jets and, in particular, to a high repetition rate pulsed microjet.
DESCRIPTION OF RELATED ART
Hypodermic needle injectors are used to introduce fluids, such as medication, anesthetic, or vaccines, subdermally. Such injectors dispense fluid into a semi-hemispherical volume of a few cubic centimeters just beneath the skin. Accordingly, 1 cc, which is equivalent to 1 ml=10
3
&mgr;L=10
3
mmd
3
, of injected fluid occupies an approximately hemispherical volume of (2II/3)R
3
, where the radius R is approximately 0.8 cm.
Liquid jet injectors have been used as an alternative to a hypodermic needle injectors. The liquid jet injectors (“microjets”) inject a small, coherent, circular diameter of a predetermined amount of fluid subdermally or a predetermined depth into the tissue. Any type of fluid may be used such as drugs or vitamins. The injected fluid is pulsed for a predetermined period of time. Pulses may be repeated at a predetermined repetition rate to cover an area, to accurately administer a larger dose, or to aid in breaking up of the tissue. Typically, the repetition rate is between several pulses to several thousand pulses per second.
Liquid jet injectors typically pressurize the fluid using CO
2
liquid that is vaporized. Conventional liquid jet injectors operate at relatively low pressure at approximately 850 psi and produce a few milliliters of fluid volume with every pulse.
It is therefore desirable to develop a device for producing a high repetition pulsed microjet of reduced spherical volume and higher pressure than conventional liquid jet injectors.
SUMMARY OF THE INVENTION
An object of the present invention is to develop a system for producing a repetitive pulsed microjet able to precisely measure doses of relative small spherical volume, for example, preferably between approximately 1 &mgr;L and approximately 10 &mgr;L (which is equivalent to approximately 1 mm
3
to approximately 10 mm
3
), with each pulse to a predetermined depth into the tissue or beneath the skin.
Another object of the present invention is to develop a device for producing a repetitive pulsed microjet to inject pulses of energy into tissue instead of conventional pulsed lasers.
The present invention is also directed to developing a method for using a device to produce repetitive pulsed microjets to be used as an alternative to ultrasonic transducers in cataract removal surgery.
Another object of the invention is to use the device to administer heated fluids beneath the surface of the skin.
The present invention relates to a system and method for producing a high repetition pulsed microjet for use in medical applications. The device includes a stagnation chamber and a hydraulic pump for pumping a sterile fluid into the stagnation chamber. A flexible walled volume disposed in the stagnation chamber is filled with a hydraulic fluid. The hydraulic piston is cyclically displaced towards/away from the stagnation chamber thereby increasing/decreasing the pressure of the hydraulic fluid on the flexible walled volume. In turn, the flexible walled volume is compressed and the sterile fluid is expelled through an orifice in the flexible walled volume under pressure producing the pulsed microjet. This process may be repeated to produce repetitive pulsed microjets. In addition, the flow conduction of the hydraulic fluid between the hydraulic pump and stagnation chamber may be controlled by inserting a blocking device therebetween.
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Darby & Darby
Medjet Inc.
Milano Michael J.
Nguyen Victor
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