Patent Application
20190021777
The present invention relates generally to surgery devices and methods. More particularly, the present invention relates to a cryotherapy device and method to treat, destroy or ablate a patient's abnormal tissues or lesions, e.g., for the ablation of cervical, precancerous lesions to prevent cervical cancer.
Cervical cancer is the third most common cancer in the world. Moreover, eighty percent of all cervical cancer cases occur in the developing world. With approximately 500,000 new cases each year, cervical cancer is responsible for over 250,000 deaths per year, making it the second leading cause of death in developing countries. Many of these deaths are women in their late 30s and early 40s, thus compromising the health and well-being of the surrounding family. Indeed, this is especially true for the children of these women, who often fall behind in their education and may be abandoned, without a mother.
While steps, such as annual PAP smears and other interventional methods, have been taken to eradicate cervical cancer in the developing world, cervical cancer still remains a large burden for these countries. Its prevalence in the developing world can in large part be attributed to a lack of appropriated technologies for screening and treatment.
A “single visit” approach has been developed and includes a screening by visual inspection with acetic acid and a point-of-diagnosis cryotherapy treatment. This approach for screening and treatment has provided a safe, acceptable, and feasible option in low-resource settings.
Cryotherapy includes freezing the abnormal cervical tissue with a coolant such as carbon dioxide, CO2, and has been used for over forty years to treat cervical dysplasia. This process uses what is called a “double freeze procedure.” One freezes the cervix for three minutes and then allows it to thaw for five minutes, then it is frozen again for an additional three minutes. This procedure maximizes the amount of tissue that is frozen more so than just doing one extra-long freeze because the frozen tissue becomes more thermally conductive after the first freeze so the second freeze penetrates quicker and subsequently deeper into the affected tissue.
Cryotherapy is the leading method for the ablation of cervical precancerous lesions for the prevention of cervical cancer, especially in the developing world. Despite proven efficacy of cryotherapy as a mode of ablating precancerous lesions, the current state of the art used to facilitate cryotherapy is not sufficiently designed for widespread and reliable use in the developing world.
While this single visit approach or “screen and treat” program has been shown to be effective in prevention of cervical cancer, there still remains a hurdle to scaling up such a program for widespread impact. While cryotherapy using CO2 has been shown to be safe and effective, even in the hands of low-level health care workers, the equipment is not necessarily suitable to be widely dispersed. Indeed, cryotherapy tools can be expensive, technically complex, lacking portability, and difficult to repair in the field.
Currently, the developing world utilizes cryoguns, see, for example, U.S. Pat. No. 4,377,168 which discloses expanding pressurized CO2 (or N2O in some instances when a country or program can afford the added expense of the N2O) against a thermally conductive tip. The expansion of the CO2 in this closed system creates a temperature of approximately −50 to −70 degrees C. on the surface of the tip which is in contact with a lesion.
With carbonated beverage manufacturers being widely dispersed in the developing world, and often using carbon dioxide to produce their carbonated beverages, carbon dioxide manufacturers are also widely dispersed in the developing world. This has led to cryoablation being conducted with carbon dioxide as the primary source of coolant.
The current design of cryotherapy tools suffers from several flaws when utilized with carbon dioxide tanks, including: water vapor leaving the tank causes tip blockages, non-medical grade carbon dioxide may have particulates, which cause tip blockages, and a pressure drop may occur in the cylinder through the cooling process during extended use which results in warmer and less effective tip temperatures.
Additionally, the equipment was never originally designed for use within the extreme conditions of the developing world where there are high volumes of ablations along with environmental abuse of the product. First, the tips on the current cryotherapy tools are manufactured with gold or chrome plating, which not only makes the tip expensive, at approximately three hundred dollars per tip, but these tips also suffer from corrosion from the chlorine disinfection method—the widely available method for sterilization in the developing world.
Improper cleaning and storage of these tips also leads to clogs, requiring replacement. Additionally, the overall cost of the equipment is around thirteen hundred to two thousand dollars per device. Moreover, with the complexity of this equipment's engineering design, there is a lack of repair knowledge and backup parts when the equipment breaks down. Unfortunately, when the cryotherapy equipment malfunctions in the field, the device becomes unused and is rarely capable of being easily fixed.
Finally, the amount of carbon dioxide required per treatment limits the portability of the device. A tank containing 50 lbs of CO2, weighs approximately 160 lbs total, and treats only about 10 to 15 patients. These large tanks are therefore difficult to transport to the rural areas where women need to be screened and treated, either in the context of health centers, mobile health vehicles or organized screen & treat camps. Therefore, these characteristics of current cryotherapy equipment prohibit its massive scale-up for widespread impact on reducing the burden of cervical cancer.
It would therefore be advantageous to provide a device and method that could safely, effectively, and in a low-cost manner treat, destroy or ablate cervical, precancerous lesions in order to prevent cervical cancer.
Recognizing the need in emerging nations for the development of improved cryotherapy techniques, the present invention is generally directed to satisfying this need. The present invention's method of treatment or process for providing cryotherapy ablation utilizes a pressurized tank of a low-temperature liquid as its source for the low-temperature, thermal reservoir that is needed to conduct by this process.
A preferred embodiment of the present invention takes the form of a device, that is adapted to connect to the outlet of a tank that is pressurized and contains liquid carbon dioxide for providing a patient with a cryotherapy process that is directed to the ablation of lesions, includes: (a) a piping assembly having a configuration that includes a distal end, adapted to connect to said pressurized tank outlet, and a proximal end with a nozzle adapted to create a spray of carbon dioxide snow as a result of the freezing of the liquid carbon dioxide upon its exhaustion from the piping assembly, (b) a tubular, snow horn having a configuration that includes a distal end, adapted to connect to the piping assembly proximal end, and a proximal end, a boundary wall extending between the ends and enclosing the snow horn's interior region, and wherein the snow horn distal end includes a snow horn nut and pressure relief means, (c) a tubular applicator having a distal end, adapted to temporarily connect to the snow horn proximal end, and a proximal end and an interior wall extending between these ends and enclosing the applicator's interior region, and wherein this interior wall has an interior diameter that increases in value from the proximal end to the distal end of the applicator, and wherein this interior wall has a plurality of vent holes, (d) an applicator tip having an inner surface and an outer surface that includes a metal portion and a configuration adapted to allow the applicator tip to connect to the applicator's distal end during process of providing cryotherapy ablation, and (e) a push rod having a distal end and a proximal end and a base attached to the push rod distal end and wherein this base includes an anchor.
A first variant of this preferred embodiment further includes a handle having a barrel, a grip, a thumb-operated trigger and a drive system adapted to control the movement of the push rod during the process of providing said cryotherapy ablation.
A second variant of this preferred embodiment further includes a wind knob situated on the handle and adapted to control the movement of the push rod during the process of collecting snow in the tubular applicator.
A third variant of this preferred embodiment is adapted so that the handle barrel has a centerline and the handle grip has a centerline, and these centerlines intersect so that the enclosed angle formed by these intersecting centerlines is in the range of 10-20 degrees.
A fourth variant of this preferred embodiment is adapted so that the amount of increase in the diameter of applicator's interior wall between its ends when divided by the length between these ends is in the range of 0.4 to 1.6 percent.
Another preferred embodiment of the present invention is that in which the configurations of the piping assembly, tubular snow horn, tubular applicator and applicator tip configurations are all further adapted for a cryotherapy process that is directed to the removal of cervical, precancerous lesions for the prevention of cervical cancer.
Thus, there has been summarized above (rather broadly and understanding that there are other preferred embodiments which have not been summarized above) the present invention in order that the detailed description that follows may be better understood and appreciated.
Before explaining at least one embodiment of the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components or elements set forth in the following description or illustrated in the drawings. This invention is capable of being practiced and carried out in various ways. Therefore, it is to be understood that the present invention is not to be limited to the specific embodiment disclosed herein, and that its many variants are intended to be included within the scope of the appended claims. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. In the accompanying drawings, like numbers refer to like elements throughout.
A preferred embodiment in accordance with the present invention 1 provides an apparatus or device and method that extracts heat from a warmer medium or material such as human or animal tissue. As shown in this application's figures, the embodiment of the present invention that is shown there utilizes cryotherapy to treat, destroy or ablate a patient's abnormal tissues or lesions, e.g., when the patient is a member of the animal species, which includes female humans for the ablation of cervical, precancerous lesions for the prevention of cervical cancer. The device includes an auxiliary piping assembly 10 that is configured to be connected to the typically horizontally-directed outlet of a pressurized, carbon dioxide tank in the bottom of which resides liquid carbon dioxide, CO2, or other suitable fluid that freezes at a comparatively low temperature (i.e., the phase diagram for CO2 reveals that it can, when it is under pressures in the range of approximately 5-100 atmospheres, only pass from a liquid to a solid state when its temperature is also below approximately minus 60 degrees Centigrade—we define herein fluids that can remain in a liquid state at such elevated pressures and when approaching such reduced temperatures as low-temperature liquids which upon freezing yield low-temperature snows).
The purpose of this piping assembly and its configuration is adapted to yield the proper flow conditions for the beginning of the creation of the CO2 snow or “dry ice” from the distal end of the piping assembly when the pressurized tank of carbon dioxide is allowed to exhaust through the piping assembly at operating pressures in the range of 750-850 psig and the CO2 freezes as it exits the assembly. See U.S. Pat. No. 6,543,251 and European Patent Number (EP) 1,046,614B1 for background technology related to the creation of CO2 snow.
One variant for the configuration of this piping assembly 10 includes a distal end 12 that has an adapter 14 which allows the piping assembly to be connected and firmly affixed to the tank's outlet, while also reducing the diameter of the pipe through which the exhaust is flowing. See
A pressure gauge 16 that is sized to measure and read pressures up to approximately 700-1,000 psig is included in this piping assembly so as to check to ensure that the tank pressure is adequate to support the creation of CO2 snow. It also includes a valve 18 that regulates flow through the piping assembly. A ninety degree elbow 20 that is used to redirect the normal direction of the flow from the tank from being horizontal to vertical, and a proximal end 22 to which is attached a nozzle 24 whose outlet or orifice 24a diameter is critical to the efficient operation of the piping assembly and it's on-demand, capability to begin the creation of CO2 snow.
A preferred variant of this piping assembly's distal end has the diameter of the pipe to which the nozzle connects being ⅛ of an inch and the diameter of the nozzle's orifice 24a being in the range of 0.005-0.050 inches, with a preferred value of 0.016 inches. Downstream from this nozzle and its orifice 24a is a snow horn 26 which has a boundary wall 26c and a configuration adapted to create the final flow conditions for the collection of CO2 snow having a desired density. Alternatively, the snow horn has a configuration adapted to create the proper flow conditions at the snow horn's proximal end so as to enable a prescribed mass of the snow of a desired density to be collected in a specified period of time. See
The CO2 snow's desired density is chosen so that the mass of CO2 snow collected is sufficient to provide the needed low temperature reservoir while also allowing the scale of the device to be such that it is appropriate for the desired cryotherapy procedure. Experimentation has shown that a CO2 snow density in the range of 8-11 g/in3 allows the required mass of snow to be in the range of 8-10 g for a normal preventive, ablation of cervical, precancerous lesions procedure.
The present invention also includes a hollow, tubular applicator 30 which has proximal 32 and distal 34 ends. As its name implies, this part of the present invention is used by a health care provider to help precisely locate the point/s on a patient where the invention's cryotherapy will be applied. This applicator 30 has a configuration that is adapted to collect and temporarily store in its interior 36 and proximate its distal end the mass 6 of CO2 snow that is required (i.e., sufficient to allow the mass of collected snow to serve as the low temperature thermal reservoir for the device after the applicator's distal end has been disconnected from the snow horn and the applicator's tip attached so the applicator and its tip together can be used to perform a cryotherapy ablation).
See
A flow-through fitting 40 is provided at the applicator's distal end that is configured to allow for, among other things, the attachment and detachment of the applicator's distal end to and from the coupling 28 on the distal end of the snow horn during the part of the process in which the applicator is filled with CO2 snow. This same fitting 40, upon being decoupled from the snow horn, is also configured to allow it to be used for attaching to the applicator's distal end an especially designed applicator cap or tip 50 which is the part of the device that actually comes into contact with a patient's body where it is desired to freeze and ablate targeted tissues or cells.
The proximal end 32 of the applicator has an opening 38 that allows access to the applicator's interior from this proximal end. This opening allows for the introduction of a means for advancing 60 any CO2 snow that may accumulate in the applicator. For the embodiment shown in
In the alternate venting pattern, channels running parallel to the axis of the applicator allow gas venting to the atmosphere at both the proximal 32 and distal 34 ends of the applicator. The opening to each of the channels is sufficiently small such that the particles of snow do not coagulate in this region in such a way as to block the channels. The channels may also serve to vent the sublimating gas during a cryotherapy treatment procedure and thereby prevent accumulation of the sublimate in the vaginal cavity which inhibits the device operator's ability to see the distal end of the applicator.
The exact dimensions of such an applicator will obviously be a function of the type of cryotherapy procedure that is desired to be performed using the present invention. For a normal preventive, ablation of cervical, precancerous lesions procedure, typical dimensions for this applicator are: outer diameter=⅝ inch, wall thickness= 1/16 inch when polycarbonate extruded tubing is being used as the material from which to fabricate the tube, length in the range of 6-8 inches, vent holes: diameters in the range of 0.02-0.03 inches and 15-20 in number and spaced at 0.25 inch intervals along the length of the tube. For an applicator sized in this manner, typical snow horn dimensions would then be: length=7-9 inches, inside tube diameter=⅜ inch and where it may be fabricated from an assortment of plastics, including polycarbonate, acrylic, polysulfone, ABS, acetal copolymer, or polypropelene.
Once the applicator is sufficiently filled with CO2 snow, the applicator is disconnected from the snow horn and an applicator cap or tip 50 is attached to the fitting 40 on the applicator's distal end 34. During a cryotherapy treatment process, the mass or plug 6 of CO2 snow must be continually pressed up against the inner side 52 of the applicator cap to ensure that the plug has good thermal contact with the applicator cap 50. An appropriately sized spring or other suitable biasing means 70 is fitted around the push rod and travels along with the push rod and up into the applicator's interior. The distal end 72 of this spring presses against the back side of the base of the applicator while its proximal end 74 rest against a portion of an especially configured handle 80 that has a configuration adapted to allow the handle to be hand-operated to control the positioning of the applicator's tip 50 and either lock in position or incrementally advance the push rod and the plug of CO2 snow.
Since, during a cryotherapy procedure, the plug 6 of CO2 snow is slowly moving towards the distal end of the applicator, the interior wall 42 of the applicator near its distal end has been provided with a slight outward taper in order to aid the forward movement of this plug. For a normal preventive, ablation of cervical, precancerous lesions procedure, and consistent with the typical dimensions previously given for an applicator, a typical taper is in the range of 0.5-6.0 percent, or more preferably in the range of 1-3 percent.
The handle 80 of the present invention is of a two-piece 82a, 82b construction and contains an opening 84 in the front face 86 of the handle and into which the proximal end 32 of the applicator is press fitted. This opening extends all the way through the handle and therefore allows the proximal end 62 of the push rod to extend from the rear face 88 of the handle. A spring-loaded trigger 90 is affixed to the handle and is configured such that a boundary edge 92 of the trigger interacts with grooves 60a on the push rod to provide the handle with its ability to incrementally advance or lock the push rod's position relative to the handle. The retraction of the push rod is handled manually (for example, to allow for the filling of the distal end of the applicator with CO2 snow), i.e., the handle's trigger is pulled backward to release the push rod while the proximal end of the push rod is grasped in the free hand of the one who is holding the device's handle and pulled backward to retract the push rod.
This device's applicator cap or tip 50 has a configuration adapted to allow it to be attached to and detached from the fitting 40 applicator's distal end and provide good thermal transfer through it since it is this tip that comes into contact with a patient and therefore needs an adequate rate of low-temperature thermal transfer from the mass of collected snow to the patient for the cryotherapy ablation process to be successful. This capability is provided by forming its outer surface 54 which comes into contact with a patient from metal while the remainder of the tip is normally formed from plastic.
The method or steps for using the present invention include:
For a cryotherapy process directed to the ablation of cervical, precancerous lesions to prevent cervical cancer, and utilizing what is called a “double freeze procedure,” a second freeze would be completed by completing steps 7 through 16 after a five minute thaw cycle is completed and by using a second applicator set (i.e., push rod, spring, applicator and its cap) that would be provided with the device.
An alternative way to describe the method of the present invention is note that it is a method for providing a patient with cryotherapy ablation in which the steps for performing this method utilizing a connection to the outlet of a pressurized tank of a low-temperature liquid in association with the device as disclosed in the prior paragraphs.
It can be seen that the current invention eliminates many of the previously noted disadvantages (e.g., frequent tip blockages in the very expensive, gold or chrome plated nozzles that do not hold up well to frequently being disinfected; current devices on which these nozzles are used cost around thirteen hundred dollars per device; often considerable difficulty in maintaining such devices; need to transport with these devices fifty pound tanks of carbon dioxide tank; difficulty in scaling up the current process to accommodate large numbers of patients) in traditional cryotherapy processes.
It should be noted that many of the above-noted advancements came about only after extensive trial-and-error efforts that utilized a series of prototypes of the present invention. Each of these prototypes also contained improvements and additional features that were added to overcome some of the unexpected, technical problems that were encountered in the operation of the earlier prototypes.
For a first example, more recently the push rod or plunger (60) of the present invention has had the base (66) on its distal end (64) reconfigured so as to better control the rate at which the applicator cap (50) warms up and detaches from the tissue when the cryotherapy procedure is terminated. In earlier prototypes, the dry ice that was at one time adjacent the push's rod's base would occasionally move forward and maintain contact with the applicator cap (50) even after the push rod itself had been locked or retracted. This prevented the applicator cap from immediately beginning to warm up when the cryotherapy procedure was terminated.
To rectify this situation, a sand-anchor-shaped fitting or anchor 61 was added to the push rod's base. See
For a second example, to make the snow collection process as reliable as possible, it was found desirable to further evolve the present invention's snow horn by improving upon the way that it interfaces at its distal end with the piping assembly proximal end and the way that it vents excess gases during the snow collection process.
This nut includes a spring-loaded, pressure-relief collar or other automatic, pressure relief means 26e that is adapted to open at a specified pressure (e.g., approximately 90 psig) to allow excess CO2 gases to be relieved before the pressure in the snow horn rises to such a level as to threaten the actual rupturing of the snow horn.
Notice should also be taken of the shape of the exterior surfaces of the snow horn nut 26d and the snow horn collar 26e. The have been specifically provided with complemental curvature or a rounded interface 26g at the points where they contact each other so as to enable the snow horn to be pivoted about these contact points to aid in aligning the various components of the device during the snow collection process.
For a third example, to make the tissue cooling portion of a cryotherapy procedure as reliable as possible, it was found desirable to further evolve the present invention's tubular applicator by improving upon: (a) its consistency of performance in allowing the collected quantity of snow to smoothly move forward through the applicator without binding at various points on the applicator's inner wall, and (b) its venting capabilities during the snow collection process.
The quantity and placement of vent holes 44 in the applicator's wall was also, from extensive experimentation, found to be important to the smooth advancement of the collected snow through the applicator. Too many vent holes (e.g, approximately 400 vent holes with 0.02 inch diameters in a 12 inch long, ¾ inch outer diameter applicator) were found to cause too much surface friction and impeded the smooth advancement of the collected snow through the applicator. This decreases the performance of the device by limiting how cold the applicator tip can get.
Venting of the now improved-upon, hollow tubular applicator 30 of the present invention is seen to be accomplished with an assortment of vent holes whose number, locations and diameters are a function of the mass of CO2 snow or dry ice that is to be collected. For example, for an 8 inch long, ¾ inch outer diameter applicator that's to be used with approximately 12.5 grams of dry ice, such an applicator would typically have: (a) 2 large diameter vent holes that are located near its proximal end and allow CO2 to vent into the device's handle, and (b) approximately 15-25 vent holes of 0.02 inch diameter that are located around the perimeter of and near the center of the applicator. When only approximately 10 grams of dry ice are to be used with this size applicator, it would typically not have the centrally located vent holes.
This improved-upon tubular applicator 30 is also seen to have: (a) nub locks 46 near its proximal end that aid in locating and locking the applicator into the device's handle 80, (b) coarse threads on its distal end that are used to temporarily connect the applicator to a snow horn during a snow collection process and to the applicator during the freeze process, and (c) a finger grip 48 that aids in aligning the applicator to the device's handle and temporarily locking the components together.
Another embodiment of this improved-upon tubular application includes one that has double walls or tubes (inner and outer) that are separated by an air gap that exists to provide the collected snow within the applicator with insulation from its surrounding hotter environment and to prevent the external surface of the applicator from getting too cold. These tubes are not bonded together so as to allow them to contract at different rates in response to the exposure to extreme temperatures due to contact with dry ice snow.
For a fourth example, much experimental effort has been expended towards perfecting the design of the device's handle 80 so as to maximize the reliability of its operation and its ease of use.
Extending downward and forward from the rear portion of the handle's barrel is a grip 98 whose centerline 98a is oriented with respect to the centerline 96a of the handle's barrel so as to be at a specified included angle, α, so as to optimize the ergonomic advantages of the handle. From much experimentation with early handle prototypes, it was found that an included angle in the range of 10-20 degrees was preferred, with an included angle of approximately 12 degrees being optimum.
The many features and advantages of the present invention are apparent from the above detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to and are considered to fall within the scope of the present invention.
This is a continuation-in-part, patent application that claims the priority and benefits of U.S. patent application Ser. No. 13/898,962, filed May 21, 2013 by the present inventors and entitled “CRYOTHERAPY DEVICE AND METHOD FOR THE TREATMENT OF CERVICAL PRECANCEROUS LESIONS” and for which U.S. Pat. No. 9,717,546 will issue on Aug. 1, 2017. The teachings of this parent application are incorporated herein by reference to the extent that they do not conflict with the teaching herein.
