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Overlapping ablation using a coaxial radiofrequency electrode and multiple cannulae system: experimental study in ex-vivo bovine liver.

Choi D, Lim HK, Kim MJ, Lee J, Kim SK, Kim EY, Kim S, Kim SH - Korean J Radiol (2003 Apr-Jun)

Bottom Line: The long-axis (diagonal) and short-axis lengths on a transverse section of four-ablation zones (cakes) ranged from 8.5 to 9.7 (mean, 9.1) cm and from 3.0 to 4.1 (mean, 3.7) cm, respectively.Gross pathologic examination of three composite six-ablation zones (spheres) showed that the long-axis (diagonal) and short-axis lengths of zones ranged from 9.0 to 9.9 (mean, 9.4) cm and from 6.8 to 7.5 (mean, 7.2) cm, respectively.Using a coaxial RF electrode and multiple cannulae, together with ultrasound guidance and precise overlapping ablation techniques, we successfully created predictable thermal zones in ex-vivo bovine liver.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Kangbuk Samsung Hospital, Seoul, Korea.

ABSTRACT

Objective: To assess the sizes and configurations of thermal zones after overlapping ablations using a coaxial radiofrequency (RF) electrode and multiple cannulae in ex-vivo bovine liver.

Materials and methods: For ablation procedures, a coaxial RF electrode and introducer set was used. Employing real-time ultrasound guidance and overlapping techniques in explanted, fresh bovine liver, we created five kinds of thermal zones with one (n=10), two (n=8), four (n=3), and six ablation spheres (n=3). Following ablation, MR images were obtained and the dimensions of all thermal zones were measured on the longitudinal or transverse section of specimens. The shape of the composite ablation zones was evaluated using three-dimensional MR image reconstruction.

Results: At gross pathologic examination of ten single-ablation zones (spheres), the long-axis (transverse) and short-axis lengths of zones ranged from 3.7 to 4.4 (mean, 4.1) cm and from 3.5 to 4.0 (mean, 3.7) cm, respectively. The long-axis (transverse) and short-axis lengths of double-ablation zones (cylinders) with 23% overlap ranged from 7.0 to 7.7 (mean, 7.3) cm and from 3.0 to 3.9 (mean, 3.5) cm, respectively; those with 58% overlap ranged from 6.0 to 6.4 (mean, 6.2) cm and from 3.8 to 4.6 (mean, 4.3) cm, respectively. The long-axis (diagonal) and short-axis lengths on a transverse section of four-ablation zones (cakes) ranged from 8.5 to 9.7 (mean, 9.1) cm and from 3.0 to 4.1 (mean, 3.7) cm, respectively. Gross pathologic examination of three composite six-ablation zones (spheres) showed that the long-axis (diagonal) and short-axis lengths of zones ranged from 9.0 to 9.9 (mean, 9.4) cm and from 6.8 to 7.5 (mean, 7.2) cm, respectively. T2-weighted MR images depicted low-signal thermal zones containing multiple curvilinear and spotty regions of hyperintensity.

Conclusion: Using a coaxial RF electrode and multiple cannulae, together with ultrasound guidance and precise overlapping ablation techniques, we successfully created predictable thermal zones in ex-vivo bovine liver.

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Related in: MedlinePlus

Photograph of a radiofrequency (RF) system (LeVeen CoAccess Electrode System, RadioTherapeutics Corporation, Mountain View, Cal., U.S.A.). At the tip of the 16-gauge outer electrode, ten hookshaped, retractable electrodes (top) are seen fully deployed (3.5 cm). Also visible are a cannula (bottom) and stylet (middle).
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Figure 1: Photograph of a radiofrequency (RF) system (LeVeen CoAccess Electrode System, RadioTherapeutics Corporation, Mountain View, Cal., U.S.A.). At the tip of the 16-gauge outer electrode, ten hookshaped, retractable electrodes (top) are seen fully deployed (3.5 cm). Also visible are a cannula (bottom) and stylet (middle).

Mentions: We used a coaxial electrode system (RadioTherapeutics Corporation) consisting of a 16-gauge LeVeen CoAccess electrode and introducer set, the latter comprising a stylet and a cannula (Fig. 1). The CoAccess electrode is equipped with an uninsulated 16-gauge outer electrode that houses ten solid, retractable, curved hooks. When these are fully extended, their diameter is 3.5 cm and the device assumes an umbrella shape. The 15-gauge insulated cannula guides placement of the electrode, and can provide access to the target tissue. A 200-W monopolar RF generator (RF 3000; RadioTherapeutics Corporation) is used as the energy source, and four ground pads under a copper plate are also employed. For ablation, the tip of the RF electrode is advanced towards the target tissue, and the curved electrodes are fully deployed. Power output is initially set at 50 W, and every 60 sec a 10 W increase is applied until 110 W is attained. The device is maintained at peak power for 15 mins or until it impedes out (a rapid rise in impedance stops current flow and ablation). If this occurs, it is turned off for 30 sec and then restarted at 70% of the maximum power attained at the time of impeding out. Application continues until the generator once again impedes out, or for 15 mins. If the device does not impede out during the first cycle, it is switched off for 30 secs and then restarted at maximum power and run until it impedes out or 15 mins have elapsed. The algorithm is based upon tissue impedance rather than tissue temperature (1).


Overlapping ablation using a coaxial radiofrequency electrode and multiple cannulae system: experimental study in ex-vivo bovine liver.

Choi D, Lim HK, Kim MJ, Lee J, Kim SK, Kim EY, Kim S, Kim SH - Korean J Radiol (2003 Apr-Jun)

Photograph of a radiofrequency (RF) system (LeVeen CoAccess Electrode System, RadioTherapeutics Corporation, Mountain View, Cal., U.S.A.). At the tip of the 16-gauge outer electrode, ten hookshaped, retractable electrodes (top) are seen fully deployed (3.5 cm). Also visible are a cannula (bottom) and stylet (middle).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2698069&req=5

Figure 1: Photograph of a radiofrequency (RF) system (LeVeen CoAccess Electrode System, RadioTherapeutics Corporation, Mountain View, Cal., U.S.A.). At the tip of the 16-gauge outer electrode, ten hookshaped, retractable electrodes (top) are seen fully deployed (3.5 cm). Also visible are a cannula (bottom) and stylet (middle).
Mentions: We used a coaxial electrode system (RadioTherapeutics Corporation) consisting of a 16-gauge LeVeen CoAccess electrode and introducer set, the latter comprising a stylet and a cannula (Fig. 1). The CoAccess electrode is equipped with an uninsulated 16-gauge outer electrode that houses ten solid, retractable, curved hooks. When these are fully extended, their diameter is 3.5 cm and the device assumes an umbrella shape. The 15-gauge insulated cannula guides placement of the electrode, and can provide access to the target tissue. A 200-W monopolar RF generator (RF 3000; RadioTherapeutics Corporation) is used as the energy source, and four ground pads under a copper plate are also employed. For ablation, the tip of the RF electrode is advanced towards the target tissue, and the curved electrodes are fully deployed. Power output is initially set at 50 W, and every 60 sec a 10 W increase is applied until 110 W is attained. The device is maintained at peak power for 15 mins or until it impedes out (a rapid rise in impedance stops current flow and ablation). If this occurs, it is turned off for 30 sec and then restarted at 70% of the maximum power attained at the time of impeding out. Application continues until the generator once again impedes out, or for 15 mins. If the device does not impede out during the first cycle, it is switched off for 30 secs and then restarted at maximum power and run until it impedes out or 15 mins have elapsed. The algorithm is based upon tissue impedance rather than tissue temperature (1).

Bottom Line: The long-axis (diagonal) and short-axis lengths on a transverse section of four-ablation zones (cakes) ranged from 8.5 to 9.7 (mean, 9.1) cm and from 3.0 to 4.1 (mean, 3.7) cm, respectively.Gross pathologic examination of three composite six-ablation zones (spheres) showed that the long-axis (diagonal) and short-axis lengths of zones ranged from 9.0 to 9.9 (mean, 9.4) cm and from 6.8 to 7.5 (mean, 7.2) cm, respectively.Using a coaxial RF electrode and multiple cannulae, together with ultrasound guidance and precise overlapping ablation techniques, we successfully created predictable thermal zones in ex-vivo bovine liver.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Kangbuk Samsung Hospital, Seoul, Korea.

ABSTRACT

Objective: To assess the sizes and configurations of thermal zones after overlapping ablations using a coaxial radiofrequency (RF) electrode and multiple cannulae in ex-vivo bovine liver.

Materials and methods: For ablation procedures, a coaxial RF electrode and introducer set was used. Employing real-time ultrasound guidance and overlapping techniques in explanted, fresh bovine liver, we created five kinds of thermal zones with one (n=10), two (n=8), four (n=3), and six ablation spheres (n=3). Following ablation, MR images were obtained and the dimensions of all thermal zones were measured on the longitudinal or transverse section of specimens. The shape of the composite ablation zones was evaluated using three-dimensional MR image reconstruction.

Results: At gross pathologic examination of ten single-ablation zones (spheres), the long-axis (transverse) and short-axis lengths of zones ranged from 3.7 to 4.4 (mean, 4.1) cm and from 3.5 to 4.0 (mean, 3.7) cm, respectively. The long-axis (transverse) and short-axis lengths of double-ablation zones (cylinders) with 23% overlap ranged from 7.0 to 7.7 (mean, 7.3) cm and from 3.0 to 3.9 (mean, 3.5) cm, respectively; those with 58% overlap ranged from 6.0 to 6.4 (mean, 6.2) cm and from 3.8 to 4.6 (mean, 4.3) cm, respectively. The long-axis (diagonal) and short-axis lengths on a transverse section of four-ablation zones (cakes) ranged from 8.5 to 9.7 (mean, 9.1) cm and from 3.0 to 4.1 (mean, 3.7) cm, respectively. Gross pathologic examination of three composite six-ablation zones (spheres) showed that the long-axis (diagonal) and short-axis lengths of zones ranged from 9.0 to 9.9 (mean, 9.4) cm and from 6.8 to 7.5 (mean, 7.2) cm, respectively. T2-weighted MR images depicted low-signal thermal zones containing multiple curvilinear and spotty regions of hyperintensity.

Conclusion: Using a coaxial RF electrode and multiple cannulae, together with ultrasound guidance and precise overlapping ablation techniques, we successfully created predictable thermal zones in ex-vivo bovine liver.

Show MeSH
Related in: MedlinePlus