Radiofrequency ablation of lung tumors in swine assisted by a navigation device with preprocedural volumetric planning.
OBJECTIVE
To develop an image guidance system that incorporates volumetric planning of spherical ablations and electromagnetic tracking of radiofrequency (RF) electrodes during insertion.


METHODS
Simulated tumors were created in three live swine by percutaneously injecting agar nodules into the lung. A treatment plan was devised for each tumor with optimization software to solve the planning problem. The desired output was the minimum number of overlapping ablation spheres necessary to ablate each tumor and the margin. The insertion plan was executed with use of the electromagnetic tracking system that guided the insertion of the probe into precomputed locations. After a 72-hour survival period, animals were killed and histopathologic sections of the tissue were examined for cell viability and burn pattern analysis.


RESULTS
A planning algorithm to spherically cover the tumors and the margin was computed. Electromagnetic tracking allowed successful insertion of the instrument, and impedance roll-off was reached in all ablations. Depending on their size, the tumors and the tumor margins were successfully covered with two to four ablation spheres. The image registration error was 1.0 mm +/- 0.64. The overall error of probe insertion was 9.4 mm +/- 3.0 (N = 8). Analysis of histopathologic sections confirmed successful ablations of the tissue.


CONCLUSIONS
Computer-assisted RF ablation planning and electromagnetically tracked probe insertion were successful in three swine, validating the feasibility of electromagnetic tracking-assisted tumor targeting. Image misregistration caused by respiratory motion and tissue deformation contributed to the overall error of probe insertion.
Banovac
Filip
F
Imaging Science and Information Systems (ISIS) Center, Georgetown University Hospital, CG 201, 3800 Reservior Rd NW, Washington, DC 20007, USA. banovac@isis.georgetown.edu <banovac@isis.georgetown.edu>
Cheng
Patrick
P
Campos-Nanez
Enrique
E
Kallakury
Bhaskar
B
Popa
Teo
T
Wilson
Emmanuel
E
Abeledo
Hernan
H
Cleary
Kevin
K
D000818:Animals; D017115:Catheter Ablation / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods; D008175:Lung Neoplasms / Q000175:diagnosis* / Q000601:surgery*; D008280:Magnetics / Q000295:instrumentation* / Q000379:methods; D011300:Preoperative Care / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013552:Swine; D016896:Treatment Outcome