Biomedical subjects

Stephen B Solomon

Publications and source records attributed to Stephen B Solomon.

14 recordsLinked to original sources

PubMed2003

Anatomic stereotactic catheter ablation on three-dimensional magnetic resonance images in real time.

BACKGROUND: Targets for radiofrequency (RF) ablation of atrial fibrillation, atrial flutter, and nonidiopathic ventricular tachycardia are increasingly being selected on the basis of anatomic considerations. Because fluoroscopy provides only limited information about the relationship between catheter positions and cardiac structures and is associated with radiation risk, other approaches to mapping may be beneficial. METHODS AND RESULTS: An electromagnetic catheter positioning system was superimposed on 3D MR images using fiducial markers. This allowed the dynamic display of the catheter position on the true anatomy of previously acquired MR images in real time. In vitro accuracy and precision during catheter navigation were assessed in a phantom model and were 1.11+/-0.06 and 0.30+/-0.07 mm (mean+/-SEM), respectively. Left and right heart catheterization was performed in 7 swine without the use of fluoroscopy, yielding an in vivo accuracy and precision of 2.74+/-0.52 and 1.97+/-0.44 mm, respectively. To assess the reproducibility of RF ablation, RF lesions were created repeatedly at the identical anatomic site in the right atrium (n=8 swine). Average distance of the repeated right atrial ablations was 3.92+/-0.5 mm. Straight 3-point lines were created in the right and left ventricles to determine the ability to facilitate complex ablation procedures (n=6 swine). The ventricular lesions deviated 1.70+/-0.24 mm from a straight line, and the point distance differed by 2.25+/-0.63 mm from the pathological specimen. CONCLUSIONS: Real-time display of the catheter position on 3D MRI allows accurate and precise RF ablation guided by the true anatomy. This may facilitate anatomically based ablation procedures in, for instance, atrial fibrillation or nonidiopathic ventricular tachycardia and decrease radiation times.

Animals↗

PubMed2003

Percutaneous computed tomography-guided radiofrequency ablation of renal masses in high surgical risk patients: preliminary results.

This article evaluates the safety and efficacy of percutaneous radiofrequency ablation (RFA) delivered by computed tomography (CT) fluoroscopic guidance for the treatment of small, solitary renal lesions in high risk surgical and anesthetic patients. In total, 29 patients with 35 small (</=4 cm) renal lesions underwent a total of 37 CT fluoroscopically guided RFA treatments using a dry RFA technique. Because of medical comorbidities, 26 patients were considered high surgical risk candidates, and 3 patients had von Hippel-Lindau disease. Procedures were performed percutaneously, under intravenous sedation and on an outpatient basis. Renal lesions were monitored on a 3-month basis using precontrast- and postcontrast-enhanced CT imaging to assess for the presence of growth or residual lesion enhancement. Of 37 RFA treatments, 35 (95%) were successfully performed under intravenous sedation and 32 (86%) treatments were performed on an outpatient basis. Over a mean radiographic follow-up period of 9 months, 33 of 35 (94%) renal lesions have required only a single RFA treatment, and 2 patients required a second, successful retreatment for small regions of residual enhancement on follow-up CT imaging. Of 13 renal lesions with a >/=12-month radiographic follow-up interval, 11 (85%) have demonstrated no residual enhancement or growth after RFA. Percutaneous RFA of small, solitary renal lesions is well tolerated in high surgical risk patients. Although early results are encouraging, longer-term follow-up time is necessary to determine the precise role of RFA in this patient population. high resolution video, medium resolution video, low resolution video

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PubMed2003

Real-time cardiac catheter navigation on three-dimensional CT images.

INTRODUCTION: Targets for ablation of atrial fibrillation, atrial flutter, and non-idiopathic ventricular tachycardia are increasingly being selected based on anatomic considerations. Because fluoroscopy provides only limited information about the relationship between catheter positions and cardiac structures, and is associated with radiation risk, other approaches to mapping may be beneficial. METHODS: The spatial and temporal information of an electromagnetic catheter tip position sensing system (Magellan, Biosense Inc.) was superimposed on a three-dimensional (3D) CT of the chest in swine using fiducial markers for image registration. Position and orientation of a 6 French catheter with an electromagnetic sensor was displayed in real-time on a corresponding 3D-CT. Catheter navigation within the heart and the great vessels was guided by detailed knowledge about catheter location in relation to cardiac anatomy. RESULTS: Anatomic structures including the atrial septum, pulmonary veins, and valvular apparatus were easily identified and used to direct catheter navigation. During the right heart examination, the catheter was navigated through the superior and inferior vena cava to predetermined anatomic locations in right atrium, right ventricle and pulmonary artery. The ablation catheter was also navigated successfully from the aorta through the aortic valve in the left ventricle. No complication was encountered during the experiments. The accuracy and precision of this novel approach to mapping was 4.69 +/- 1.70 mm and 2.22 +/- 0.69 mm, respectively. CONCLUSIONS: Real-time display of catheter position and orientation on 3D-CT scans allows accurate and precise catheter navigation in the heart. The detailed anatomic information may improve anatomically based procedures like pulmonary vein ablation and has the potential to decrease radiation times.

Animals↗

PubMed2003

Initial experience with a novel focused ultrasound ablation system for ring ablation outside the pulmonary vein.

INTRODUCTION: Atrial fibrillation has been shown to initiate from triggers within pulmonary veins. Several studies have documented that electrical isolation of those triggers can lead to maintenance of sinus rhythm. The complication of pulmonary vein stenosis has limited the utility of delivering ablation energy within the pulmonary vein. We utilize a focused ultrasound catheter ablation system for delivery of transmural ablation lines proximal to the pulmonary vein ostium. METHODS: Nine dogs (weight 30-39 kg) were anesthetized and ventilated. Through a transseptal approach, pulmonary veins were engaged with the focused balloon ultrasound catheter. Ultrasound power was delivered at 40 acoustic watts outside the pulmonary vein ostium, focused 2 mm off the balloon surface, with a depth of approximately 6 mm, for 30-120 seconds. Following ablation, lesions were histopathologically analyzed. RESULTS: Of nine animals studied, fourteen pulmonary veins were ablated. We found successful delivery of near circumferential and transmural ablation lines in 6/14 pulmonary veins. In each of the six circumferential ablations, successful alignment of the ultrasound transducer along the longitudinal axis of the parabolic balloon occurred. The final four ablations were conducted with an enhanced catheter design that assured axial alignment. Of these ablations, all four were circumferential. The remaining 8 pulmonary veins had incomplete delivery of lesions. In each of these veins the ultrasound transducer was misaligned with the balloon axis when therapy was delivered. CONCLUSION: Focused ultrasound ablation is a new means of performing pulmonary vein isolation. This method provides delivery of lesions outside the vein, limiting the risk of pulmonary vein stenosis for the treatment of atrial fibrillation.

Animals↗

PubMed2003

Interstitial photon radiation.

Most minimally invasive ablative techniques utilize thermal energies for tissue destruction. However, the heat-sink phenomenon may limit the efficacy of radiofrequency ablation and cryotherapy of tissue near blood vessels. One alternative non-temperature-dependent ablative technique is photon radiation. This radiation is dependent on energy and intensity, and its effects are influenced only by the density of the surrounding tissue. Photon radiation therapy may offer a unique alternative for ablating tissue surrounding vascular structures.

Animals↗

PubMed2003

Histologic evolution of high-intensity focused ultrasound in rabbit muscle.

RATIONALE AND OBJECTIVES: The purpose of this study was to examine the histologic evolution over time of rabbit skeletal muscle thermally ablated with high-intensity focused ultrasound. The objectives included determining the extent and focality of damage created by this noninvasive, transcutaneous ablative technology. METHODS: Transcutaneous, thermal ablation with an external focused ultrasound transducer was applied to the paraspinous muscles of 19 rabbits. At varying times, up to 100 days after therapy, single sonications were examined histologically. RESULTS: Initially, only subtle staining changes were identified within lesions. In the chronic phase (day 51-100), the muscle was replaced or infiltrated by variable amounts of scar and fat similar to degenerative muscle disorders. Histologic changes were limited to the tissue within the intensity focus of the transducer and were not seen in intervening tissues. DISCUSSION: The current study took a systematic approach to study the long term, in vivo histologic effects of single HIFU lesions in a nonregenerative tissue. This experience in muscle tissue will provide a basis for understanding ultrasound effects for clinical applications such as treatment of uterine fibroids, cardiac tissue, and sarcomas.

Animals↗

PubMed2003

Talc pleurodesis mimics pleural metastases: differentiation with positron emission tomography/computed tomography.

Talc pleurodesis is a technique used in the treatment of patients with persistent pleural effusions or pneumothorax not amenable to other treatment. These are commonly seen in patients with malignant thoracic neoplasms. Radiographic abnormalities resulting from prior talc pleurodesis could be confused with progression of the underlying neoplastic process. Positron emission tomography with F-18 fluorodeoxyglucose (FDG-PET) might be unable to distinguish between malignant and benign inflammatory processes. This report demonstrates the use of combined positron emission tomography/computed tomography (PET/CT) in a patient with a history of both malignant neoplasm and a prior talc pleurodesis. Fusion of PET and CT studies could add information that CT and PET alone cannot. This could alter the diagnostic and therapeutic course for patients with a history of both thoracic neoplasm and talc pleurodesis.

Chylothorax↗

PubMed2002

Focused ultrasound ablation of the epididymis with use of thermal measurements in a canine model.

OBJECTIVE: To explore the epididymis as an alternative anatomical target to the vas deferens for noninvasive male sterilization using therapeutic focused ultrasound. DESIGN: Controlled preclinical study. SETTING: Canine animal model in an academic research environment. PATIENT(S): Four healthy male mongrel dogs (30-35 kg). INTERVENTION(S): A transducer mounted on a plastic clip delivered ultrasound energy to the canine epididymis. Thermocouples placed transcutaneously into the epididymis, intradermally, and on the skin surface recorded temperatures during ablation with a wide range of acoustic powers and sonication times (control, 3 W/120 s, 5 W/90 s, 7 W/60 s). MAIN OUTCOME MEASURE(S): Thermocouple temperature measurements determined the optimal range of ablation parameters that produced successful thermal occlusion of the epididymis without adverse effects (e.g., skin burns, testicular injury). RESULT(S): A large "therapeutic window" was determined (power = 3-7 W, time = 20-120 seconds) over which noninvasive thermal occlusion of the epididymis can be achieved. Thermal occlusion rates were higher, and complications lower, than found previously with vas deferens ablation. CONCLUSION(S): The epididymis represents a larger and easier target than the vas deferens for performing noninvasive male sterilization using focused ultrasound. Long-term azoospermia studies will be necessary to confirm permanent sterilization with this technique.

Animals↗

PubMed2002

Percutaneous gadolinium injection under MR guidance to mark target for CT-guided radiofrequency ablation.

Selection of the appropriate imaging tool depends on a number of factors that reflect the patient, the procedure, and the physician. Multiple imaging techniques are often required to perform elements of a whole procedure. A patient with an allergy to iodinated contrast material and a 3.0-cm hepatic metastasis that was invisible on computed tomography (CT) was treated with CT-guided radiofrequency ablation by first injecting gadolinium under magnetic resonance guidance to mark the location of the lesion. Gadolinium's high atomic number makes it a viable contrast agent for attenuating x rays under fluoroscopic or CT guidance.

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PubMed2002

High-intensity focused ultrasound ablation of the epididymis in a canine model: a potential alternative to vasectomy.

BACKGROUND AND PURPOSE: High-intensity focused ultrasound (HIFU) is a noninvasive technology capable of inducing thermal coagulative necrosis of subsurface structures without injuring intervening tissues. We have previously reported on the feasibility of HIFU vasectomy in a canine model. In this study, we evaluated the feasibility of HIFU ablation of the canine epididymis as an alternative to vasectomy. The epididymis may be a better target than the vas deferens because it is larger, more easily positioned in the HIFU focal zone, and more susceptible to occlusive injury at lower energy levels, thus reducing collateral damage. MATERIALS AND METHODS: A hand-held HIFU clamp was used to grasp the epididymides of anesthetized dogs (eight surgically exposed and six grasped transcutaneously). An ultrasound transducer in the clamp focused energy on a 1 x 3 x 8-mm target zone centered between the clamp jaws. Ultrasonic energy (6-19 W) was delivered to this target zone for various times (16-150 seconds). The vas, epididymis, and testis were harvested for histologic examination 2 weeks after ablation. RESULTS: Seven of the eight epididymides ablated after surgical exposure demonstrated histologic findings associated with occlusion (fibrosis, hemorrhage, and proximal duct dilatation). Five of the six epididymides ablated transcutaneously also demonstrated histologic evidence of occlusion. Skin burns were evident overlying three epididymides, and one testicular injury was noted adjacent to an ablated region of the epididymis. CONCLUSION: High-intensity focused ultrasound ablation of the epididymis causes injury and histologic changes associated with epididymal occlusion. Further investigations are under way to optimize ablation parameters and to confirm azoospermia with ejaculate studies. Refinement of this technology may provide a rapid noninvasive alternative to conventional vasectomy.

Animals↗

PubMed2002

Robotic percutaneous access to the kidney: comparison with standard manual access.

PURPOSE: To evaluate the efficiency, accuracy, and safety of robotic percutaneous access to the kidney (PAKY) for percutaneous nephrolithotomy in comparison with conventional manual techniques. MATERIALS AND METHODS: We compared the intraoperative access variables (number of access attempts, time to successful access, estimated blood loss, complications) of 23 patients who underwent robotic PAKY with the remote center of motion device (PAKY-RCM) with the same data from a contemporaneous series of 23 patients who underwent conventional manual percutaneous access to the kidney. The PAKY-RCM incorporates a robotic arm and a friction transmission with axial loading system to accurately position and insert a standard 18-gauge needle percutaneously into the kidney. The blood loss during percutaneous access was estimated on a four-point scale (1 = minimal to 4 = large). The color of effluent urine was graded on a four-point scale (1 = clear to 4 = red). RESULTS: The mean target calix width was 13.5 +/- 9.2 mm in the robotic group and 12.2 +/- 4.5 mm in the manual group (P = 0.57). When comparing PAKY-RCM with standard manual techniques, the mean number of attempts was 2.2 +/- 1.6 v 3.2 +/- 2.5 (P = 0.14), time to access was 10.4 +/- 6.5 minutes v 15.1 +/- 8.8 minutes (P = 0.06), estimated blood loss score was 1.3 +/- 0.49 v 1.7 +/- 0.66 (P = 0.14), and color of effluent urine following access was 2.0 +/- 0.90 v 2.1 +/- 0.7 (P = 0.82). The PAKY-RCM was successful in obtaining access in 87% (20 of 23) of cases. The other three patients (13%) required conversion to manual techniques. There were no major intraoperative complications in either group. CONCLUSIONS: Robotic PAKY is a feasible, safe, and efficacious method of obtaining renal access for nephrolithotomy. The number of attempts and time to access were comparable to those of standard manual percutaneous access techniques. These findings provide the groundwork for the development of a completely automated robot-assisted percutaneous renal access device.

Blood Loss, Surgical↗

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.

Animals↗

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.

Animals↗