Surgery – Instruments – Cyrogenic application
Reexamination Certificate
2000-01-05
2002-05-07
Leubecker, John P. (Department: 3739)
Surgery
Instruments
Cyrogenic application
C606S022000, C606S021000
Reexamination Certificate
active
06383181
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to method and apparatus for the thermal ablation of the interior lining of an organ, and more particularly for destruction of Barrett's tissue and other lesions of the gastrointestinal tract by cryo-ablation of the gastrointestinal mucosa (gastrointestinal tract lining).
REVIEW OF THE RELATED TECHNOLOGY
Barrett's esophagus is a recognized precursor to 50% of all esophageal cancers. The incidence of esophageal cancer is rising and this disease is now among the top 15 cancers (Blot et al, JAMA, 270:1320 [1993]). Barrett's tissue has been found in 10% of an asymptomatic population undergoing upper gastrointestinal endoscopy.
Standard therapy for esophageal cancer is removal of the esophagus, with mortality rates up to 37%. Treatment of this cancer costs $25,000 to $50,000 dollars per patient.
Barrett's esophagus is characterized by abnormal cell growth along the inner lining of the esophagus above the lower esophageal sphincter. Recent studies have demonstrated that when the metaplastic columnar epithelium characteristic of Barrett's is removed, healing replaces the Barrett's tissue with normal stratified squamous epithelium (Sampliner et al,
Gastrointestinal Endoscopy
, 44:532-535 [1966]). This presumably reduces the risk of cancer.
Lives would be saved if Barrett's tissue could be removed quickly, inexpensively, and with low risk. However, the only available procedures have been slow, costly, uncomfortable, and/or dangerous. As a result, Barrett's esophagus goes untreated in many patients, whose health suffers.
The known ablation treatments for Barrett's esophagus include laser treatment (Ertan et al,
Am. J. Gastro
., 90:2201-2203 [1995]), ultrasonic ablation (Bremner et al,
Gastro. Endo
., 43:6 [1996]), photodynamic therapy (PDT) using photo-sensitizer drugs (Overholt et al,
Semin. Surq. Oncol
., 1:372-376 (1995)), and multipolar electrocoagulation such as by use of a bicap probe (Sampliner et al, supra). The treatments are often made with the aid of an endoscope.
Both sonic and light treatments require expensive apparatus and treat only a small area at one time, so that an operation to remove the Barrett's tissue becomes tedious as well as more costly. One reported treatment with Nd:YAG laser used a 2.2-mm beam to treat large areas of the esophagus (Ertan et al,
Am. J. Gastro
. 90:2201-2203 [1995]). Furthermore, such therapies are often accompanied by esophageal strictures and significant patient inconveniences; since total avoidance of sun exposure and bright light is required for one month after photodynamic therapy.
Another problem is that there is no visual indication of which tissues have been treated, or the extent to which tissues have been treated. The physician, looking through an endoscope, cannot see the effects of the sound or light directly.
Cryotherapy of the esophagus via direct contact with a liquid nitrogen cryoprobe (metal probe cooled to a low temperature) has been studied in both animal models and humans (Rodgers et al,
Cryobiology
. 22:86-92 (1985); Rodgers et al,
Ann. Thorac. Surq
., 55:52-7 [1983]) and has been used to treat early esophageal cancer (Grana et al,
Int. Surg
., 66:295 [1981]). Disadvantages of this modality include the necessity for direct mucosal contact, which temporarily binds the probe to the esophagus, potentiating the risk of esophageal perforation and inability to control the exact area of mucosal ablation. Rodgers et al states that a cryoprobe must include a heating element to allow it to be removed. This precludes removal of the probe until thawing has occurred. The depth of the injury with a solid cryoprobe cannot be reliably controlled. If the tip heater malfunctions, or timing is not precise, the depth of freezing can become dangerous. In spite of the heating element, cats died from esophageal lesions in some cases, apparently caused by freezing too deeply and destroying the esophageal wall entirely. These studies highlight the fact that controlling the amount of tissue that is irreversibly damaged by cooling is one of the main problems with cryosurgery.
Use of a bicap electrocoagulation probe has been suggested as a means for ablation of Barrett's esophagus (Heier et al,
Gastro. Endo
., 43:185 [1996]). The use of a bicap electrocoagulation probe also suffers from many disadvantages. Since the tip is small and must be repeatedly energized, the operation will be slow and time-consuming. Furthermore, the depth of injury is difficult to control. Esophageal perforation could occur with excessive duration of the electrocautery current.
All the known ablation treatments using sound, light, or heat also suffer from another defect, a defect common to all: penetration of the damage. The treatments cannot be adjusted to destroy only the very thin lining with the Barrett's tissue; underlying tissue is destroyed as well.
As flesh is somewhat transparent to both sound and light, these energies will penetrate some distance below the surface. The proportion of energy absorbed by the tissue is generally constant, and so, at least to a first approximation, the intensity of the light or sound will fall off exponentially with depth. Therefore, the amount of tissue damage will also tend to decrease exponentially with distance. There is consequently no sharp line of demarcation between destroyed tissue and tissue which is not affected: the degree of damage decreases continuously. Healthy tissue is damaged along with diseased tissue.
The same type of damage results from heat probe or cryoprobe treatments. When the surface temperature of flesh is raised, heat travels by conduction into the tissue. The penetration of the heat—the temperature/depth function—depends on the surface temperature, the exposure time, and the heat capacity of the hot probe in contact with the surface. The degree of damage at any one depth depends on the temperature reached. Similar problems are involved with the freezing associated with contact by a solid cryoprobe.
Clearly, to raise the tissue temperature to a damaging level in only a thin layer of epithelium, heat must be applied quickly from a very high-temperature probe. However, this creates problems of possible sticking and require precise timing of the hot probe contact duration, lest heat penetrate too deeply.
Complicating the use of heat, there is also a time factor. Not only the peak temperature reached by tissue, but also how long the tissue “bakes” at the high temperature, determines the amount of damage. (This is the reason cold water should be put onto a burn, even after the bum is away from heat.)
With none of the existing therapies is one able to precisely control the depth of tissue damage while maintaining a sharp demarcation between damaged and undamaged tissue, with the physician being able to observe the precise location and degree of damage as it occurs. Ideally, the Barrett's tissue should be destroyed with the direct visualization and control by physician in a manner which avoids any substantial damage to adjacent healthy tissue.
SUMMARY OF THE INVENTION
The present invention overcomes the drawbacks of the prior art by using a direct spray of cryogenic liquid to ablate Barrett's tissue in the esophagus. Liquid nitrogen, an inexpensive and readily available liquified gas, is directed onto the Barrett's tissue through a tube while the physician views the esophagus through an endoscope. The apparatus and method of the present invention can be used to cause controlled damage to the mucosal layer at any location in the gastrointestinal tract in a manner in which re-epithelialization can occur. They can be used not only for the treatment of Barrett's esophagus, which is the preferred application of the present invention, but also for the treatment of any mucosal gastrointestinal lesion, such as tumor, polyps and vascular lesions. The apparatus and method can also be used for the treatment
Cartledge Jennifer B.
Johnston Mark H.
Bloom Leonard
Leubecker John P.
Majerowicz Frank
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