Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-08-20
2002-07-23
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S438000, C600S466000
Reexamination Certificate
active
06423009
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to cryosurgery and more specifically, to a method and system employing three-dimensional ultrasonography for assisting in the placement of cryoprobes and other medical instruments during percutaneous prostatectomy procedures.
BACKGROUND OF THE INVENTION
One of the most important functions of clinical surgery is the resection and removal of undesirable tissues. Cryosurgery is an alternative surgical technique in which undesirable tissue is frozen, in the hope that freezing alone will destroy the undesirable tissue without necessitating resection and removal of the undesirable tissue. Leaving dead tissue in place may have beneficial immunological effects.
Cryosurgery is performed using one or more internally cooled cryosurgical probes which will be hereinafter referred to as cryoprobes. A typical cryoprobe is a surgical device having the general appearance and size of a conventional knitting needle, which is provided with cooling sites disposed at predetermined locations on the outer surface thereof. Typically, the cooling sites are located at the tip of the cryoprobe and cooling is accomplished by employing one of a variety of cooling means such as boiling of refrigerants, cooling of refrigerants, Joule-Thomson effects etc. In a typical percutaneous transrectal cryosurgical procedure, such as a prostatectomy, the cooling site on the cryoprobe is first brought into contact with the undesirable prostate tissue. The cryoprobe is then cooled and, as the temperature of the probe is lowered, tissue freezing begins from the cooling site surface outward into the tissue forming a frozen region commonly referred to as an ice-ball. Typically, freezing is continued until the ice-ball has encompassed all the prostate and any undesirable tissue known to exist outside the prostate. However, as will be described in greater detail below, up until now, the extent of the freezing is usually approximated by the practitioner. The frozen tissue is left in situ to be dealt with by the body's immune system.
In contrast, in traditional resection surgery, the practitioner targets the undesirable tissue and using visual and tactile control, manually resects and removes that tissue.
Cryosurgery has numerous advantages which have promoted small scale, steady use of this procedure for approximately 150 years since the first description of the method by J. Arnott in 1845. Arnott taught that, by applying a brine solution to diseased skin tissue, the tissue could be frozen and destroyed. One of the advantages of cryosurgery is the ease with which this procedure can be applied with minimal trauma to the patient. Conventional surgical procedures require resection which results in blood loss and trauma to the patient.
In modern prostate cryosurgery, cryoprobes are inserted into undesirable tissue through small punctures in the skin at predetermined sites, thereby minimizing the surgical trauma experienced by the patient. In comparison, resection surgery of the prostate is considered a major surgery, with significant bleeding, morbidity, mortality and lengthy recovery periods. There are also further risks and side effects associated with resection surgery such as wound infection, urinary tract infection, deep venous thrombosis, impotence and incontinence.
Another advantage of cryosurgery is that the cryoprobes are applied focally, to treat only the undesirable region, thereby sparing much of the surrounding healthy tissue. This aspect of the procedure has found important applications in liver cryosurgery. In resection surgery, the extent of the tissue removed is determined by many considerations related to conventional resection strategy, such as integrity of the blood supply and the functionality of the tissue remaining after surgery. Often, this strategy requires removal of significant amounts of healthy tissue or even whole organs.
In contrast, the strategy of a cryosurgical procedure is to only remove the undesirable tissue, even if it has irregular margins and shape, leaving the healthy tissue intact. Cryosurgery can therefore be considered a tissue-sparing procedure.
Furthermore, after resection surgery it is often very difficult to retreat the tissue if the disease recurs due to severe fibrosis and the risks of damaging either the sphincter, causing incontinence, or the rectum. However, when cryosurgical procedures are employed, the tissue can be, and routinely is retreated because adhesions and fibrosis considerations are not significant factors. Further to this end, because there is less fibrosis and adhesions in the pelvis, cryosurgery is also advantageous over other modern localized treatment modalities such as, radical prostatectomy, hyperthermia or radiation therapy.
The above-described advantages of cryosurgery have helped the method remain in use for the last 150 years. However, while this type of procedure is effective in many situations where a non-invasive procedure is required, there are several disadvantages with conventional cryosurgical techniques.
Many practitioners were reluctant to use cryosurgery because it was considered inferior to resection surgery. The technique suffered from three major drawbacks which rendered it problematic. Firstly, when the cryosurgical procedure is internal and as no large incisions are made, the practitioner does not have tactile and/or visual contact with the undesirable tissue and is therefore forced to operate “blind”. Operating “blind” severely hinders an accurate determination of the outline of the prostate and the extent of any other undesirable tissue. Accordingly, the determination is, at best, only an approximation, based primarily on the practitioner's experience and skill. Secondly, due to the lack of tactile and/or visual contact, the ability to control the extent to which the undesirable tissue is being frozen and thereby destroyed is limited and, once again, must be approximated by the practitioner. Furthermore, the third disadvantage of particular relevance to the present invention is that it is typically very difficult to place medical instruments, such as cryoprobes, percutaneously with any comfortable degree of accuracy. Therefore it is possible that inaccurate placement of the medical instruments could lead to over treatment beyond the desired region, leading to detrimental side effects such as incontinence.
Unlike after resection surgery, after cryosurgery, the undesirable tissue remains in the patient at the end of the procedure. After resection surgery, the practitioner takes confidence in the effectiveness of the procedure in question, by virtue of the fact the undesirable tissue was removed from the patient. However, after a cryosurgical procedure, due to the fact that the undesirable tissue is left in the patient, the level of confidence as to the effectiveness of the procedure is low as there is no true knowledge as to whether or not the undesirable tissue was extirpated. In conventional cryosurgery the practitioner has no means for confirming the success of his procedure immediately at the completion of the cryosurgical procedure. This is also disadvantageous to the patient's psychological state-of-mind, as the patient must recover and wait for further post-surgical testing to determine the effectiveness of the procedure.
The above described disadvantages of cryosurgery were severe enough to make the use of cryosurgery questionable for many years. Probably the most significant breakthrough in cryosurgery occurred when body imaging technologies were developed, and two-dimensional ultrasonography was employed to image the freezing process during cryosurgery. The use of two-dimensional ultrasonography has resolved in part the original drawbacks with cryosurgery and has led to an unprecedented growth in the use of this technique. However, while the use of two-dimensional ultrasonography imaging has alleviated some of the practitioner's above- described visual disadvantage, two-dimensional ultrasonography has not completely resolved the imaging problem. Furthermore,
Downey Donal
Fenster Aaron
Lateef Marvin M.
Life Imaging Systems Inc.
Patel Maulin
Zavis Katten Muchin
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