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76 Executive Briefing Lesion comparison test Ex vivo chicken breasts were kept cool in a refrigerator and were not frozen or left uncovered before testing. The chicken breast was placed across the grounding pad of the MultiGen Radiofrequency Generator so that only one-third of the chicken was on the conduc- tive section of the pad. Side-by-side lesions were created with the 100mm, 20-gauge, 10mm tip Venom Cannula and the 100mm, 20-gauge, 10mm tip standard RF cannula, according to the following procedure. The 20-gauge Venom Cannula was inserted into the chicken breast approximately 1mm to 2mm below the surface. After the cannula entered the tissue, it was rotated to orient the bend in the hori- zontal plane and then advanced until the active tip was fully insert- ed into the tissue. An aliquot (0.15 mL) of 0.9% NaCl solution was placed in the cannula, and the Venom electrode was then inserted into the cannula so that it deployed out the side port. The same procedure was followed to insert the standard 20-gauge cannula and electrode into the chicken breast in a location that was parallel to, and one inch away from, the Venom Cannula. Thermal lesions were created with temperature control at 80°C for 90 seconds us- ing the MultiGen Radiofrequency Generator. Before each pair of lesions was created, care was taken to ensure that both electrodes read impedance within 5% of each other.The testing procedure was repeated two more times on the same chicken breast to cre- ate three pairs of lesions with the 20-gauge cannulae. A second chicken breast was then placed on the grounding pad and the procedure was repeated using the 100mm, 18-gauge, 10mm tip Venom Cannula and the 100mm, 18-gauge, 10mm tip standard RF cannula. Therefore, a total of 12 lesions (six lesion pairs) were creat- ed during the test: six 20-gauge lesions on one chicken breast and six 18-gauge lesions on a separate chicken breast. The length and transverse width of all of the lesions were measured and recorded. Fluid propagation: The location of fluid propagation was compared between the 18-gauge Venom Cannula and the 18-gauge standard RF cannula and between the 20-gauge Venom Cannula and the 20-gauge standard RF cannula. A four-inch section of damp gauze was suspended and labeled with four markers to serve as targets for placing the cannulae. Four syringes containing approximately one mL of dyed solution (blue food coloring in water) were connected to the cannulae samples. Each standard RF cannula was placed with the tip on the marker and the opening at the end facing the same direction. Each Venom Cannula was placed on the wetted gauze in the same fashion, with the side port oriented in the same direction. Beginning with the 18-gauge cannulae, approximately 0.05 mL of dyed solution was dispensed from each syringe and an image was captured of the dyed spots on the gauze. The same procedure was followed for the 20-gauge cannulae. For all samples, the syringes were displaced slowly to ensure that the gauze was not saturated too quickly, which could have altered the natural profusion of the solution. Results Thermal dosing test The Venom Cannula created lesions in ex vivo chicken breasts that featured larger radiofrequency thermal dosing than the stan- dard RF cannula. The radiofrequency energy dosage with the 20-gauge Venom Cannula was 18% to 40% greater than with the 20-gauge standard RF cannula (average of 27% greater across the four tests). Likewise, the radiofrequency energy dosage with the 18-gauge Venom Cannula was 34% to 59% greater than with the 18-gauge standard RF cannula (average of 43% greater across the four tests). The Venom Cannula also delivered significantly more consistent radiofrequency thermal dosing than the standard RF cannula. One standard deviation of the average results for the 20-gauge Venom Cannula equaled 41 J (approximately 2% of the average dose of 1959 J), whereas one standard deviation for the 20-gauge standard RF cannula equaled 103 J (approximately 7% of the average dose of 1546 J). The 18-gauge Venom Cannula also showed more consistent dosing than the 18-gauge standard RF cannula. Lesion comparison test The Venom Cannula and Venom Electrode combination produced consistently larger lesions than Stryker's standard RF cannula and electrode in ex vivo chicken breasts, as shown by the cross sec- tional measurements and representative images of the lesion pairs. The lesions created by the 20-gauge Venom Cannula and Venom Electrode combination were approximately 35% wider and 6% lon- ger than those created by the 20-gauge standard RF cannula and electrode, based on the average measurements of lesion pairs one through three. Likewise, the lesions created by the 18-gauge Ven- om Cannula and Venom Electrode were approximately 25% wid- er and 12% longer than those created by the 18-gauge standard RF cannula and electrode, based on the average measurements of lesion pairs four through six. The length of the Venom lesions was distributed equally both proximal and distal to the tip of the Venom Cannula and Venom Electrode. The volume of the lesions produced by the Venom Cannula and standard RF cannula was also compared. The three-dimensional shape that a standard thermal lesion takes has been best described as a prolate spheroid, which is an elongated spherical body. Due to the difficulty of seeing the true three-dimensional shape that the Venom lesion takes in a tis- sue specimen, it was necessary to approximate the shape based on a two-dimensional view in the specimen. Thus, the volume of the le- sions was calculated using the cross-sectional dimensions and the equation, V=4/3*π*a*b2, where "a" is the longitudinal radius and "b" is the transverse radius of a prolate spheroid. It should be noted that the Venom electrode contributes a greater percent increase in active surface area when used with the 20-gauge Venom Cannula than with the 18-gauge Venom Cannula and will subsequently yield a greater percent increase in lesion volume when compared to the standard RF cannulae of equivalent size. On average, the 20-gauge Venom Cannula created a lesion of 92% greater volume than the 20-gauge standard RF cannula, and the 18-gauge Venom Cannula created a lesion of 76% greater volume than the 18-gauge stan- dard RF cannula. Calculated average volume of lesions produced by the Venom Cannula and standard RF cannula in ex vivo chicken breasts Gauge size Venom Standard D e l t a Cannula (mm 3 ) RF cannula (mm 3 ) (%) 20-gauge 337 175 92% 18-gauge 655 373 76% Fluid propagation test In the fluid propagation test, the shape and location of the dyed region of gauze around each cannula tip showed that the Venom Cannulae dispersed the solution more proximal to the center of the exposed tip (i.e., more local to the side port). In contrast, the stan- dard RF cannulae dispersed the solution in a location more distal to the exposed tip. For both the 18-gauge and 20-gauge cannu- lae, the dye dispersion from the Venom Cannulae showed more symmetry in the X direction than was seen with the standard RF cannulae. The solution dispersion from the Venom Cannulae also provided more adequate coverage of the exposed tip than did the standard RF cannulae. The immediate dispersion of the solution did not completely encompass the exposed tip of the standard RF cannulae. Discussion Numerous factors influence the size and shape of a radiofrequen- cy lesion. The lesions form adjacent to the interface between the conductive surfaces of the radiofrequency source and the patient