| Solid hydrogel coupling for ultrasound imaging and therapy -> Monitor Keywords |
|
|
 
Solid hydrogel coupling for ultrasound imaging and therapyRelated Patent Categories: Surgery: Kinesitherapy, Kinesitherapy, UltrasonicSolid hydrogel coupling for ultrasound imaging and therapy description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060184074, Solid hydrogel coupling for ultrasound imaging and therapy. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATIONS [0001] This application is a divisional application based on prior copending application Ser. No. 10/449,819 filed May 30, 2003, which itself is based on a prior copending provisional application, Ser. No. 60/384,566, filed on May 30, 2002, the benefit of the filing dates of which is hereby claimed under 35 U.S.C. .sctn..sctn. 119(e) and 120. FIELD OF THE INVENTION [0003] The present invention generally relates to a hydrogel based coupling for use in ultrasonic imaging and therapy, and method for use of the same, and more specifically, pertains to a dimensionally stable hydrogel that remains stable when transmitting relatively high intensity ultrasound to a therapy site, and a method for using the same. BACKGROUND OF THE INVENTION [0004] Ultrasound is widely used for imaging a patient's internal structures without risk of exposure to potentially harmful radiation, as may occur when using X-rays for imaging. The first recorded use of ultrasound for imaging was by Dr. Karl Dussik, a Psychiatrist working at a hospital in Bad Ischl, Austria, who employed ultrasound to locate brain tumors. He used two opposed probes, including one for transmitting ultrasound waves, and the other for receiving them. With these probes, he transmitted an ultrasound beam through a patient's skull, and used the received signal to visualize the cerebral structure by measuring the ultrasound beam attenuation. He published a description of his technique in 1942, in an article entitled, "Hyperphonography of the Brain." [0005] Medical diagnostic equipment specially manufactured for using ultrasound became available in the 1950s. An ultrasound examination is a safe diagnostic procedure that uses high frequency sound waves to produce an image of the internal structures of a patient's body. Many studies have shown that these sound waves are harmless and may be used with complete safety, even to visualize the fetus in pregnant women, where the use of X-rays would be inappropriate. Furthermore, ultrasound examinations are sometimes quicker and typically less expensive than other imaging techniques. [0006] More recently, the use of high intensity focused ultrasound (HIFU) for therapeutic purposes, as opposed to imaging, has received significant attention in the medical community. HIFU therapy employs ultrasound transducers that are capable of delivering 1,000-10,000 W/cm.sup.2 to a focal spot, in contrast to diagnostic imaging ultrasound, where intensity levels are usually below 0.1 W/cm.sup.2. A portion of the energy from these high intensity sound waves is transferred to the targeted location as thermal energy. The amount of thermal energy thus transferred can be sufficiently intense to cauterize undesired tissue, or to cause necrosis of undesired tissue (by inducing a temperature rise to beyond 70.degree. C.) without actual physical charring of the tissue. Tissue necrosis can also be achieved by mechanical action alone (i.e., by cavitation that results in mechanical disruption of the tissue structure). Further, where the vascular system supplying blood to an internal structure is targeted, HIFU can be used to induce hemostasis. The focal region of this energy transfer can be tightly controlled so as to obtain necrosis of abnormal or undesired tissue in a small target area without damaging adjoining normal tissue. Thus, deep-seated tumors can be destroyed with HIFU without surgical exposure of the tumor site. [0007] A particular advantage of HIFU therapy over certain traditional therapies is that HIFU is less invasive. The current direction of medical therapy is progressively toward utilizing less-invasive and non-operative approaches, as is evident from the increasing use of laparoscopic and endoscopic techniques. Advantages include reduced blood loss, reduced risk of infection, shorter hospital stays, and lower health care costs. HIFU has the potential to provide an additional treatment methodology consistent with this trend by offering a method of non-invasive surgery. Also, HIFU enables transcutaneous tumor treatment without making a single incision, thus avoiding blood loss and the risk of infection. Furthermore, HIFU therapy may be performed without the need for anesthesia, thereby reducing surgical complications and cost. Most importantly, these treatments may be performed on an outpatient basis, further reducing health care cost, while increasing patient comfort. [0008] The use of HIFU for the destruction of tumors is a relatively new technique. The first clinical trials were performed on patients with hyperkinetic and hypertonic disorders (symptoms of Parkinson's disease). HIFU was used to produce coagulation necrosis lesions in specific complexes of the brain. While the treatment was quite successful, monitoring and guidance of the HIFU lesion formation was not easily achieved (as reported by N. T. Sanghvi and R. H. Hawes, (1994) "High-intensity focused ultrasound," Gastrointestinal Endoscopy Clinics of North America, 4: 383-95). [0009] Two HIFU-based systems have been developed for the treatment of benign prostatic hyperplasia (BPH) in humans (see the report by E. D. Mulligan, T. H. Lynch, D. Mulvin, D. Greene, J. M. Smith, and J. M. Fitzpatrick, (1997) "High-intensity focused ultrasound in the treatment of benign prostatic hyperplasia," Br J Urol, 70: 177-80). These systems are currently in clinical use in Europe and Japan, and are undergoing clinical trials in the United States. Both systems use a transrectal HIFU probe to deliver 1,000-2,000 W/cm.sup.2 to the prostate tissue through the rectum wall. No evidence of damage to the rectal wall has been observed during a rectoscopy, performed immediately after HIFU treatment (as reported by S. Madersbacher, C. Kratzik, M. Susani, and M. Marberger, (1994) "Tissue ablation in benign prostatic hyperplasia with high intensity focused ultrasound," Journal of Urology, 152: 1956-60, discussion 1960-61). Follow-up studies have shown decreased symptoms of BPH (i.e., increased urinary flow rate, decreased post-void residual volume, and decreased symptoms of irritation and obstruction (see S. Madersbacher, C. Kratzik, N. Szabo, M. Susani, L. Vingers, and M. Marberger, (1993) "Tissue ablation in benign prostatic hyperplasia with high-intensity focused ultrasound," European Urology, 23: 1: 39-43). [0010] HIFU has also been studied for the de-bulking of malignant tumors (C. R. Hill and G. R. ter Haar, (1995) "Review article: high intensity focused ultrasound--potential for cancer treatment," Br J Radiol, 68: 1296-1303), prostate cancer (S. Madersbacher, M. Pedevilla, L. Vingers, M. Susani, and M. Marberger, (1995) "Effect of high-intensity focused ultrasound on human prostate cancer in vivo," Cancer Research, 55: 3346-51), and testicular cancer (S. Madersbacher, C. Kratzik, M. Susani, M. Pedevilla, and M. Marberger, (1998) "Transcutaneous high-intensity focused ultrasound and irradiation: an organ-preserving treatment of cancer in a solitary testis," European Urology, 33: 195-201) are among the cancers currently being investigated clinically for potential treatment with HIFU. An extensive clinical study to extracorporeally treat a variety of stage 4 cancers is underway in England (as noted by A. G. Visioli, I. H. Rivens, G. R. ter Haar, A. Horwich, R. A. Huddart, E. Moskovic, A. Padhani, and J. Glees, (1999) "Preliminary results of a phase I dose escalation clinical trial using focused ultrasound in the treatment of localized tumors," Eur J Ultrasound, 9: 11-18). The cancers involved include prostate, liver, kidney, hipbone, ovarian, breast adenoma, and ocular adenoma. No adverse effects, except one case of skin burn, have been observed. [0011] An important component in any type of ultrasound therapy system is the mechanism for coupling the acoustic energy into the tissue. Good acoustic coupling is necessary to efficiently transfer the ultrasound energy from the transducer to the treatment site. The ideal acoustic coupler is a homogenous medium that has low attenuation and acoustic impedance similar to that of the tissue being treated. Due to its desirable acoustic transmission characteristics, water has commonly been used as the coupling medium in many therapeutic applications of ultrasound. [0012] In previous hemostasis studies in which HIFU has been used to arrest bleeding of injured blood vessels and organs, the HIFU transducer was contained within a water-filled, conical, plastic housing with a thin, polyurethane membrane at the tip. This coupler was designed for superficial treatments, since it places the HIFU focus only several millimeters beyond the tip of the cone. While this coupling method has been useful for hemostasis experiments, it has many drawbacks that would make it impractical for a clinical setting. These disadvantages include degassing, sterilization, circulation, and containment issues. Due to the limitations of the current HIFU applicators, an alternative coupling medium is desirable. [0013] Previous studies have shown hydrogels to be efficient coupling media for diagnostic ultrasound. Hydrogels are hydrophilic, cross-linked, polymer networks that become swollen by absorption of water. The high WC and favorable mechanical properties of hydrogels have made them attractive for a wide range of biomedical applications, including soft contact lenses, maxillofacial reconstruction, burn dressings, and artificial tendons. Since hydrogels consist mostly of water, they inherently have low attenuation and acoustic impedance similar to tissue. They can be formed into rigid shapes and have relatively low material costs. [0014] Unlike the ultrasound transmission gels typically used for diagnostic scans, hydrogels can have consistencies similar to soft rubber, and can be formed into relatively rigid, three-dimensional (3-D) shapes. It would be desirable to provide hydrogel based couplings, methods for producing such hydrogel couplings, and methods for using such hydrogel couplings, wherein each coupling and each method is specifically configured for use in HIFU applications. It should be understood that because of the significant increase in power in HIFU as opposed to imaging, HIFU applications require much more robust couplers that can withstand the higher energy conveyed through the material, than is required in diagnostic or imaging applications. [0015] Polyacrylamide (PA) gel has been employed as an acoustic coupler for non HIFU applications. The structure and properties of polyacrylamide have been extensively researched for the past 30 years. Currently, its most common biomedical application is gel electrophoresis for the separation of charged macromolecules. PA gel can have a very high WC, ranging from 70% to greater than 90% water by weight. The gel can be prepared relatively easily and quickly at room temperature. In addition, PA has been used for a variety of biomedical applications, and has been shown in many studies to have very good biocompatibility. An important consideration for any blood-contacting device is its resistance to causing thrombosis on its surface. Experiments have shown PA to exhibit no platelet adhesion. A recent clinical study that investigated the use of a PA-based blood filtration technique showed the material to have good blood compatibility, with no signs of hemolysis or blood clotting. It would thus be desirable to develop PA gel-based coupling materials, a method for making such materials, and a method for using such materials, where the materials are specifically configured for HIFU therapy applications. SUMMARY OF THE INVENTION [0016] A first aspect of the present invention is directed to a hydrogel coupling adapted to be disposed between an ultrasound transducer and a target, for use in acoustically coupling an ultrasound transducer with at least one of the target and a physical boundary associated with the target. Desirable targets might include surface tissue on a patient, as well as sub-dermal areas within a patient's body. Thus, the physical boundary can be the dermal layer of a patient, and the target area can be a sub-dermal area, so that the acoustic transducer must be coupled with the dermal layer. The acoustical energy generated by the transducer must then move through the coupling, through the dermal layer (the physical boundary), and be focused on the target. [0017] Furthermore, the target or physical boundary may also represent the wall of an internal body cavity. For example, a probe including an ultrasound transducer and a hydrogel coupling in accord with the present invention may be inserted into a body cavity, so that the hydrogel coupling acoustically couples the acoustic transducer to the wall of the body cavity. Depending on the focal length of the ultrasound transducer, the focal region can be proximate the wall, in which case the wall is the target. In other cases, the focal region can be beyond the wall, in which case the wall is the physical boundary, and the target is beyond the wall. [0018] In some cases, a probe may be surgically inserted into a patient, such that the hydrogel coupling of the present invention couples to internal tissues. As with the cavity wall noted above, such internal tissue can be considered either a boundary or a target, depending on the focal length of the acoustic transducer and the size and shape of the hydrogel coupling, and the location of the tissue to be treated. [0019] In a first aspect of the present invention, the hydrogel coupling includes a dimensionally stable hydrogel mass having a proximal surface configured to be disposed adjacent to an ultrasound transducer, and a distal surface configured to acoustically couple with at least one of a target and a physical boundary associated with a target. A distance between the proximal surface and an outer extent of the distal surface of the dimensionally stable hydrogel mass (i.e., its length) is selected to ensure that a focal region of an ultrasound transducer is disposed proximate a target. In some cases, the target will be proximate a boundary such as a dermal layer or a cavity wall, and the distance will differ from the focal length of the acoustic transducer by a relatively small amount. In other cases, the target will be disposed beyond such a boundary, and the distance will be selected to ensure that when the dimensionally stable hydrogel mass is disposed between the acoustic transducer and the boundary, such that when the acoustic transducer is coupled with the boundary, the focal region of the acoustic transducer is proximate the target. Longer focal lengths will require a dimensionally stable hydrogel mass having a greater length. By selecting a dimensionally stable hydrogel mass having an appropriate length, the focal region will overlap the target. [0020] Preferably, the proximal surface of the dimensionally stable hydrogel mass is further configured to conform to an outer surface of an ultrasound transducer. In some embodiments, the proximal surface is convex in shape. The distal surface of the dimensionally stable hydrogel mass can be shaped as desired. Beneficial distal surface shapes include concave surfaces, convex surfaces and flat surfaces. The body of the dimensionally stable hydrogel mass (i.e., the portion between the proximal and distal surfaces) can be shaped as desired. A generally cone shaped, dimensionally stable hydrogel mass is likely to be preferred, since the acoustic beam from an ultrasonic transducer configured for applying HIFU is generally focused to a cone shape, starting out with a broad footprint near the ultrasonic transducer, and narrowing to a small focal region. Dimensionally stable hydrogel masses in the shapes of cones and truncated cones have been empirically determined to be useful. [0021] In at least one embodiment, the dimensionally stable hydrogel mass is substantially transparent, to avoid blocking a view of a target when in use. This characteristic facilitates the use of the hydrogel coupling, since a clinician will be able to see through the dimensionally stable hydrogel mass, to verify where the outer extent of the distal surface is contacting the boundary or the target. Continue reading about Solid hydrogel coupling for ultrasound imaging and therapy... Full patent description for Solid hydrogel coupling for ultrasound imaging and therapy Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Solid hydrogel coupling for ultrasound imaging and therapy patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Solid hydrogel coupling for ultrasound imaging and therapy or other areas of interest. ### Previous Patent Application: Method and device for applying pressure waves to the body of an organism Next Patent Application: Treatment of skin with acoustic energy Industry Class: Surgery: kinesitherapy ### FreshPatents.com Support Thank you for viewing the Solid hydrogel coupling for ultrasound imaging and therapy patent info. IP-related news and info Results in 0.29146 seconds Other interesting Feshpatents.com categories: Qualcomm , Schering-Plough , Schlumberger , Seagate , Siemens , Texas Instruments , 174 |
 * Protect your Inventions * US Patent Office filing 
PATENT INFO |
|
