Biomedical subjects

Stephen B Solomon

Publications and source records attributed to Stephen B Solomon.

40 records · Page 3Linked to original sources

PubMed2002

Measurement of needle-tip bioimpedance to facilitate percutaneous access of the urinary and biliary systems: first assessment of an experimental system.

RATIONALE AND OBJECTIVES: Percutaneous access to the renal collecting system or biliary system is most frequently performed under image guidance. However, current techniques lack a feedback mechanism to help confirm successful access. A percutaneous needle system has been developed consisting of a modified 18-gauge percutaneous access needle that measures tissue impedance at its needle tip. Initial results in utilizing this novel system to determine successful access into dilated kidney and gall bladder specimens are reported. METHODS: Impedance measurements were recorded as the needle was precisely advanced through ex vivo kidney and liver/gall bladder specimens. In an anesthetized porcine model, impedance values were recorded with laparoscopic visualization as the needle was advanced percutaneously through abdominal wall, liver, and into gall bladder. RESULTS: A characteristic, reproducible drop in impedance was noted with successful entry into ex vivo distended kidney and gall bladder specimens. This feature was also noted during in vivo percutaneous cholecystostomy. CONCLUSIONS: A measurable, characteristic drop in tissue impedance signifies successful entry into the urinary and biliary systems. This impedance needle system may facilitate current percutaneous access techniques.

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PubMed2002

Robotically driven interventions: a method of using CT fluoroscopy without radiation exposure to the physician.

Radiation exposure to physicians' hands during interventional procedures with computed tomography (CT) fluoroscopic guidance may be high. A robot was developed that could hold, orient, and advance a needle, with CT fluoroscopic guidance. This robot could be either computer or joystick controlled. Twenty-three robotically guided percutaneous interventions were performed without complication. Physician radiation exposure was negligible during the CT fluoroscopy-guided procedures.

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PubMed2002

High intensity focused ultrasound ablation of the vas deferens in a canine model.

PURPOSE: High intensity focused ultrasound is an ablative technology capable of producing thermal coagulative necrosis of sub-surface structures without injuring intervening tissues. We assessed the feasibility of using high intensity focused ultrasound to produce occlusion of the canine vas deferens. MATERIALS AND METHODS: A high intensity focused ultrasound transducer was incorporated into a hand held clip specially designed to grasp the vas deferens transcutaneously. Slots within the jaws of the clip ensured that the vas deferens and high intensity focused ultrasound target zone were properly co-located. We ablated 10 vasa using a range of power and time parameters. At 2 weeks after ablation each vas, epididymis and testis was surgically harvested en bloc. Retrograde vasography was performed to assess vasal occlusion, followed by pathological analysis. RESULTS: High intensity focused ultrasound occlusion of the vas deferens was confirmed in 4 specimens ablated with parameters at the upper end of the parameter range, 2 of the 2 ablated with 7 W. for 60 seconds and 2 of the 4 ablated with 7 W. for 30 seconds. Histological injury was noted in 8 of the 10 ablated specimens. Skin burns that developed over 4 of the targeted vasa were conservatively managed. Bilateral sham procedures in a control dog resulted in patent vasa and no associated skin burns. CONCLUSIONS: We demonstrated the feasibility of noninvasive, transcutaneous high intensity focused ultrasound occlusion of the vas deferens with ablation powers at the upper end of the tested range, that is 7 W. Modifications of the hand held clip and optimization of ablation parameters would likely improve the success rate of this procedure. Refinement of this technology may provide a rapid noninvasive alternative to conventional vasectomy.

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PubMedDate not supplied

Treatment of renal tumors with radiofrequency ablation.

BACKGROUND: Radiofrequency (RF) energy has been investigated as a minimally invasive modality for ablating small renal tumors. Recent advances in the application of this technology have improved its safety and effectiveness. MATERIALS AND METHODS: We describe the technology of RF application and review the current delivery systems as applied to renal tumor ablation. We also review relevant animal studies, which have revealed the natural history of ablated renal tissue. Finally, we examine recent human trials with an emphasis on longer-term follow-up, imaging, complications, and successful ablation according to tumor location within the kidney; i.e., central v peripheral. RESULTS: Radiofrequency ablation can be performed safely in a minimally invasive fashion either percutaneously or laparoscopically. Energy delivery varies, and available systems include dry, wet, cooled-tip, and bipolar electrodes. Heat rise and subsequent charring in the tissue adjacent to the electrode is limited by temperature or impedance-based feedback systems. In animal studies, ablation results in complete cell kill, as judged by nicotinamide adenine dinucleotide diaphorase staining. Clinical trials with intermediate follow-up show excellent success rates. Tumors >3 cm and central tumors have a higher recurrence rate after RFA than smaller, more peripheral tumors. CONCLUSIONS: The current literature suggests that RFA is a promising minimally invasive method of treating small renal tumors. Nevertheless, long-term follow-up is still required, and questions remain regarding the optimal delivery system, duration of ablation, and method of surveillance.

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