Surgery – Instruments – Electrical application
Reexamination Certificate
2002-08-26
2004-02-17
Cohen, Lee (Department: 3739)
Surgery
Instruments
Electrical application
C607S099000, C607S113000
Reexamination Certificate
active
06692493
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to advances in medical systems and procedures for prolonging or improving human life. More particularly, this invention relates to an improved method and system for alleviating urinary obstruction caused by enlargement of the prostate by performing intraurethral radio-frequency ablation for urethral enlargement.
BACKGROUND OF THE INVENTION
A majority of all males over 60 years old experience partial or complete urinary obstruction because of enlargement of the prostate. This condition usually originates from benign prostatic hyperplasia (BPH), which is an increase in cell mass near the urethra, or less likely, from prostate cancer. Both these conditions involve an increase in prostatic tissue mass, which in its increased state encroaches on the urethra and obstructs the urinary pathway.
In the case where urinary obstruction is caused by BPH, a common treatment involves a medical procedure using a medical side-cutting instrument and/or endoscope to surgically enlarge a passageway for urine flow through the prostate. The side-cutting instrument or endoscope is passed through the penis into the urethra and is surgically used to remove prostate tissue and part of the urethra at the point of obstruction. This procedure is referred to as “Trans-Urethral Resection of the Prostate” (or “TURP”). This procedure, although effective, is invasive and complicated. For example, it requires the use of anesthesia and substantial hospital care. It also has the risk of causing bleeding. Moreover, it is expensive and causes great discomfort and trauma to the patient. For example, chapter 18, entitled “Complications of Transurethral Resection of the Prostate,” by R. Sunshine and M. Droller, of a book entitled
Urologic Complications, Medical and Surgical, Adult and Pediatric,
edited by Fray S. Marshall (Yearbook Medical Publishers, 1986), elaborates on the various complications of the TURP procedure.
In the case where urinary obstruction results from prostatic cancer, surgical prostatectomies are commonly used to eliminate the obstruction. However, surgical prostatectomies have serious side effects and risks, including impotence and urinary incontinence.
In recent years, less invasive systems and procedures that inflict less trauma on patients have been attempted. One such procedure, called “Trans-Urethral Needle Ablation” (or “TUNA”), involves passing a radio-frequency (RF) instrument such as a catheter, cannula, sheath, or scope into the urethra. The RF instrument houses special RF electrode tips that emerge from the side of the instrument. The tips are pushed out of the instrument along off-axis paths to pierce the urethral wall and pass into the prostatic tissue outside of the urethra. As a result of the various electrodes emerging from the side of the instrument, such radio-frequency instruments are frequently complex and expensive. By heating the prostate with RF power applied through the electrode tips emerging from the side of the radio-frequency (RF) instrument, the prostate tissue surrounding the urethra is ablated. Specifically, heat ablation is performed at multiple locations outside the urethra to provide a series of ablations, thereby causing the prostate tissue outside the urethra to die and necrose. Subsequent to heating, the necrotic tissue is absorbed by the body or excreted, thereby reducing the tissue mass outside the urethra, which consequently reduces the urethral obstruction. For further explanation of this system and procedure, one can consult a research paper published by Goldwasser, et al., entitled “Transurethral needle ablation (TUNA) of the prostate using low-level radio-frequency energy: an animal experimental study;”
Eur. Urol.,
vol. 24, pp. 400-405 (1993); and a research paper published by Schulman, et al., entitled “Transurethral needle ablation (TUNA); safety, feasibility, and tolerance of a new office procedure for treatment of benign prostate hyperplasia;”
Eur. Urol.,
vol. 24, pp. 415-423 (1993). Also, product literature on the TUNA system available from a company named Vitamed, Inc., of Menlo Park, Calif., carries some description of the procedure.
The TUNA system and procedure is generally used to relieve urethral obstruction caused by BPH. It favors a transurethral approach because the target tissue to be ablated is generally near to it. However, again, although the TUNA system and procedure is effective, it requires epidural or general anesthetic, and generally causes the patient great discomfort and pain. Moreover, the TUNA procedure is medically and technically very complex for surgeons to perform, requiring a complicated and expensive catheter or sheath or RF electrode system to perform it. Also, it is a relatively blind procedure in the sense that the ends of the RF electrodes emerging at the side of the radio-frequency electrode system, once they penetrate the target tissue cannot be seen. Nor is there any technique for providing a visual representation of them. Furthermore, the TUNA system and procedure attempts to leave the urethra intact and uninjured by the application of RF heating, which is difficult to achieve, making its outcome uncertain. The TUNA system and procedure causes scratching of the urethra, bleeding or irritation from a cystoscope, cannula, catheter, or tissue-piercing electrode tips passed into the urethra. Furthermore, the TUNA procedure produces trapped coagulated and necrotic tissue or fluid in the interstitial region of the prostate outside the urethra. This can result in swelling and increased pressure of tissue outside the prostate as the necrotic tissue is absorbed by the body. Such pressure can compress the urethra to further enhance its obstruction.
It is observed that such techniques have not been directed at creating ablation of urethra or the periurethral region (the region surrounding the urethra or the critical prostate region) for the reasons discussed above. Accordingly, it would be desirable to have an effective technique to perform intraurethral RF electrode ablation of the urethra and periurethral tissue for the purposes of alleviating urinary obstruction caused by enlargement of the prostate and that avoids the limitations of the art.
Another system and procedure contemplated by Onik, et al. is described in their research paper entitled “Transrectal ultrasound-guided percutaneous radical cryosurgical ablation of the prostate,”
Cancer,
vol. 72, pp. 1291-1299 (1993). This technique is utilized for the treatment of prostate cancer and involves disposing cryogenic (freezing) probes in the prostate for ablating the cancer cells. Onik, et al., propose passing a cryogenic probe transperineally (through the perineum) into the prostate. At the same time, an imaging ultrasonic probe is passed through the rectum and is used to visualize the position of the cryogenic probe and the volume of cryogenic ablation in the prostate. This technique requires use of cryogenic probes (also referred to as cryo-probes) having a relatively large diameters. The cryo-probes are complex in construction and operation and require elaborate cooling and thawing cycles, making the procedure typically quite complicated and expensive. It is technically challenging and critical to maintain precise temperatures at the target tissue area to prevent hemorrhaging when removing the probe and also to prevent freezing sensitive rectal mucosa tissue.
One more recent procedure contemplated and reported by McGahan, et al., in their research paper entitled “Percutaneous Ultrasound-Guided Radiofrequency Electrocautery Ablation of Prostate Tissue in Dogs,”
Acad. Radiol.,
vol. 2, pp. 61-65 (1994), involves placing an RF electrode transrectally into the prostate of a dog under rectal ultrasound guidance. Their intent was solely to explore the feasibility of ablating cancerous tumors within the peripheral region of the prostate. Their research treated only normal animals and no ablation of cancer tissue was actually performed. McGahan, et al., hoped to prevent RF heat ablation of the urethra (which i
Cosman Eric R.
Goldberg S. Nahum
McGovern Francis J.
Rittman, III William J.
Cohen Lee
Cosman Company, Inc.
Fish & Richardson P.C.
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