In an electrosurgical generator for generating radio frequency power, the generator includes a radio frequency output stage having two or more output connections, and a power supply coupled to the output stage for supplying power to the output stage. A controller is operable to cause the generator to supply a blended output signal alternating constantly between a first output signal across the output connections in which the radio frequency output voltage developed across the output connections is limited to at least a first predetermined threshold value for cutting or vaporisation of tissue, and a second output signal across the output connections in which the radio frequency output voltage developed across the output connections is limited to a second threshold value for coagulation. There is also provided adjustment means, operable by a user of the electrosurgical generator, for changing between various preset settings for the blended signal, the preset settings each having a predetermined duty cycle of the blended signal that is limited to the first threshold value for cutting or vaporisation, and a predetermined duty cycle of the blended signal that is limited to the second threshold value for coagulation.

Electrosurgical generator and system

A stent includes a main body of a generally tubular shape for insertion into a lumen of a vessel of a living being. The tubular main body includes a substantially biodegradable matrix having collagen IV and laminin that enclose voids within the matrix. The tubular main body also includes a biodegradable strengthening material in contact with the matrix to strengthen the matrix. The tubular main body is essentially saturated with drugs.

Biodegradable drug delivery vascular stent

Mechanisms of Tissue Injury in Cryosurgery

An electrosurgical system including an electrode assembly having two electrodes for use immersed in an electrically conductive fluid has a generator with control circuitry for rapidly reducing the delivered radio frequency output power by at least 50% within at most a few cycles of the peak radio frequency output voltage reaching a predetermined threshold limit. In this way, tissue coagulation can be performed in, for example, saline without significant steam generation. The same peak voltage limitation technique is used in a tissue vaporization or cutting mode to limit the size of the steam pocket at the electrodes and to avoid electrode burning.

Electrosurgical generator method

An artery, vein, aneurysm, vascular malformation or arterial fistula is occluded through endovascular occlusion by the endovascular insertion of a platinum wire and/or tip into the vascular cavity. The vascular cavity is packed with the tip to obstruct blood flow or access of blood in the cavity such that the blood clots in the cavity and an occlusion if formed. The tip may be elongate and flexible so that it packs the cavity by being folded upon itself a multiple number of times, or may pack the cavity by virtue of a filamentary or fuzzy structure of the tip. The tip is then separated from the wire mechanically or by electrolytic separation of the tip from the wire. The wire and the microcatheter are thereafter removed leaving the tip embedded in the thrombus formed within the vascular cavity. Movement of wire in the microcatheter is more easily tracked by providing a radioopaque proximal marker on the microcatheter and a corresponding indicator marker on the wire. Electrothrombosis is facilitate by placing the ground electrode on the distal end of the microcatheter and flowing current between the microcatheter electrode and the tip.

Endovascular electrolytically detachable wire and tip for the formation of thrombus in arteries, veins, aneurysms, vascular malformations and arteriovenous fistulas

Method and apparatus for placing therapeutic devices such as embolic coils includes a probe assembly carried within a catheter. The probe assembly includes a fiber-optic cable with a connector retained thereon by crimping. The connector has a cable-receiving end resembling a ferrule, which is crimped about the cable. The other end of the connector provides mounting of a therapeutic device, such as an embolic coil. Heat releasable adhesive bonds the therapeutic device to the mounting portion of the connector. Laser energy transmitted through the fiber-optic cable is converted to heat by the connector, which thereupon becomes heated, releasing the adhesive bond between the connector and the therapeutic device. The probe assembly can then be withdrawn from the treatment site.

Method and apparatus for placement of an embolic coil

PURPOSE To assess the effectiveness of self-expanding, cobalt-alloy stents in the treatment of aneurysms in a canine model and to observe the pattern of blood flow and formation of fibrotic scar tissue.

METHODS Porous metallic stents were endovascularly placed across the necks of experimentally created side aneurysms in the carotid arteries of three dogs; aneurysms were also created in the opposite carotid arteries in these animals to serve as controls.

RESULTS Before stent placement, angiography of the carotid arteries demonstrated whirl-like, vortex flow of blood within the lumens of the aneurysms. Inflow was seen along the distal aneurysm wall; outflow was demonstrated along the proximal wall; slower vortex flow was present in the central lumen. Immediately after stent placement there was disruption of the usual vortex flow with stasis of contrast media and blood within the lumen. Inflow and outflow patterns were no longer seen. Complete ablation of these aneurysms was evident at follow-up angiographic studies--1 week, 1 month, and 2 months after stent placement. The stented carotid arteries remained widely patent; control aneurysms and carotid arteries were patent and unchanged. Histopathologic analysis revealed fibrotic reactive scar tissue completely filling the stented aneurysm pouches.

CONCLUSION Treatment of selected intracranial aneurysms via an endovascular approach has merit and could supplant more invasive, risky, and costly surgical procedures in some cases.

http://www.ajnr.org/content/ajnr/15/7/1223.full.pdf

Embolization of experimentally created aneurysms with intravascular stent devices.

Objective: To determine the feasibility and efficacy of cryosurgery of breast cancer. Design: In phase 1, carcinogen-induced mammary adenocarcinomas in 13 Sprague-Dawley rats were treated by cryosurgery and were then examined for histopathologic change. In phase 2, transplantable mammary adenocarcinomas in 50 DBA/IJ mice were treated by cryosurgery to determine the effect of varying tumor temperatures, and duration and number of freeze-thaw cycles on tumor viability. In phase 3, 2- to 3-cm ultrasound-monitored cryolesions were formed in the breasts of 4 dogs and 4 sheep. These animals were followed up for procedure-related complications; the histopathologic necrosis of the cryolesions were correlated with the ultrasound images. Based on the results of these experiments, ultrasound-guided cryosurgery of breast cancer was initiated in a human clinical trial. Results: In phase 1, a single, short-term ( Conclusions: In situ breast cryosurgery has been proved to be feasible and efficacious in small and large animal studies and has been successfully performed in 1 patient with breast cancer. The results of this study suggest that ultrasound-guided cryosurgery of breast cancer warrants further investigation. Arch Surg. 1997;132:28-33

https://jamanetwork.com/HttpHandlers/ArticlePdfHandler.ashx?journal=SURG&articleId=596712&pdfFileName=archsurg_132_1_005.pdf

Cryosurgery of Breast Cancer

Leflunomide is an isoxazole with newly discovered immunosuppressive properties. Its mechanism of action operates later in the cell cycle than cyclosporine and appears to interfere with lymphocyte IL-2 responsiveness. With the encouraging results from in vitro and small-animal studies, we subjected leflunomide to the rigorous canine renal transplantation model in a dose response protocol. Thirty-eight female mongrel dogs underwent renal transplantation and bilateral nephrectomy. Immunosuppression was stratified from controls with no immunosuppression to monotherapy with leflunomide at 2, 4, 8, and 16 mg/kg/day given orally and in a combination therapy with cyclosporine. To evaluate its toxicity while maintaining a low constant blood level, eight dogs were treated by continuous intravenous infusion at doses of 2, 4, 6, and 8 mg/kg/day. The mean survival time for nonimmunosuppressed controls (n = 2) was 9 days, leflunomide 2 mg/kg/day (n = 2) was 9 days, leflunomide 4 mg/kg/day (n = 4) was 16 days, leflunomide 8 mg/kg/day (n = 5) was 28 days, leflunomide 16 mg/kg/day (n = 7) was 21 days. Cyclosporine alone at 10 mg/kg/day (n = 4) resulted in a mean survival time of 13 days. The mean survival time with the combination of cyclosporine 10 mg/kg/day with leflunomide 4 mg/kg/day (n = 6) was 68 days. The mean survival time for continuous intravenous leflunomide 2 mg/kg/day (n = 2) was 10 days; for leflunomide 4 mg/kg/day, 20 days; for leflunomide 6 mg/kg/day, 14 days; and leflunomide 8 mg/kg/day, 21 days. The mean serum trough levels of leflunomide ranged from 10 micrograms/ml at the 2 mg dose to 55 micrograms/ml for the 16 mg dose, levels that have been well tolerated in man. Leflunomide at 16 mg/kg/day reliably prevented acute allograft rejection, but the dogs died of inanition with normal renal function. Leflunomide at a nontoxic dose of 4 mg/kg/day extended survival to 16 days, but all dogs died of rejection. A combination of inadequate doses of leflunomide (4 mg/kg/day) and cyclosporine (10 mg/kg/day) resulted in all animals having normal renal function and weight for > or = 30 days. Even at a high dose of 16 mg/kg/day, no viral or bacterial infections were noted. These observations in a canine system add to the growing enthusiasm for the evaluation of leflunomide in human transplantation.

An evaluation of leflunomide in the canine renal transplantation model.

BACKGROUND AND PURPOSE: Carotid fusiform aneurysms are most commonly treated with occlusion of the parent vessel. The purpose of our study was to assess the effectiveness of self-expanding, cobalt-alloy stents in the ablation of experimental fusiform aneurysms with preservation of the parent vessel in a carotid artery model. METHODS: Porous metallic stents were placed endovascularly along the lengths of experimentally created fusiform aneurysms in the carotid arteries of dogs; aneurysms were also created in the animals' opposite carotid arteries to serve as controls. RESULTS: Before stent placement, angiography of the carotid arteries showed large fusiform aneurysms along the lengths of the common carotid arteries and complex patterns of flow. Immediately after stent placement there was disruption of the usual flow patterns within the lumens of the fusiform aneurysms. The lumen between the wall of the aneurysm and stented carotid showed stasis of contrast material and blood. Near-complete ablation of all aneurysms was observed 8 weeks after stent placement. The stented carotid arteries remained widely patent; control aneurysms and carotid arteries were patent and unchanged. Histopathologic analysis revealed fibrotic reactive scar tissue filling the space between the stent wires and outer wall of the fusiform aneurysm. CONCLUSION: Changing blood flow dynamics within an aneurysm can promote thrombus formation. The stent promotes stasis and thrombus within the residual lumen between the stent wall and the outer wall of the aneurysm because its woven wire mesh interferes with usual blood flow patterns, which then promotes formation of thrombus and fibrosis within the residual aneurysmal lumen.

http://www.ajnr.org/content/ajnr/21/4/739.full.pdf

Michael Haklin

Papers

Method and apparatus for placement of an embolic coil

Embolization of experimentally created aneurysms with intravascular stent devices.

Cryosurgery of Breast Cancer

An evaluation of leflunomide in the canine renal transplantation model.

Occlusion of experimentally created fusiform aneurysms with porous metallic stents.