title: In vivo accuracy assessment of a needle-based navigation system for CT-guided radiofrequency ablation of the liver.
abstract: Computed tomography (CT)-guided percutaneous radiofrequency ablation (RFA) has become a commonly used procedure in the treatment of liver tumors. One of the main challenges related to the method is the exact placement of the instrument within the lesion. To address this issue, a system was developed for computer-assisted needle placement which uses a set of fiducial needles to compensate for organ motion in real time. The purpose of this study was to assess the accuracy of the system in vivo. Two medical experts with experience in CT-guided interventions and two nonexperts used the navigation system to perform 32 needle insertions into contrasted agar nodules injected into the livers of two ventilated swine. Skin-to-target path planning and real-time needle guidance were based on preinterventional 1 mm CT data slices. The lesions were hit in 97% of all trials with a mean user error of 2.4 +/- 2.1 mm, a mean target registration error (TRE) of 2.1 +/- 1.1 mm, and a mean overall targeting error of 3.7 +/- 2.3 mm. The nonexperts achieved significantly better results than the experts with an overall error of 2.8 +/- 1.4 mm (n=16) compared to 4.5 +/- 2.7 mm (n=16). The mean time for performing four needle insertions based on one preinterventional planning CT was 57 +/- 19 min with a mean setup time of 27 min, which includes the steps fiducial insertion (24 +/- 15 min), planning CT acquisition (1 +/- 0 min), and registration (2 +/- 1 min). The mean time for path planning and targeting was 5 +/- 4 and 2 +/- 1 min, respectively. Apart from the fiducial insertion step, experts and nonexperts performed comparably fast. It is concluded that the system allows for accurate needle placement into hepatic tumors based on one planning CT and could thus enable considerable improvement to the clinical treatment standard for RFA procedures and other CT-guided interventions in the liver. To support clinical application of the method, optimization of individual system modules to reduce intervention time is proposed.
authors.affiliation: Division of Medical and Biological Informatics, German Cancer Research Center, Heidelberg, Germany. l.maier-hein@dkfz.de
authors.forename: Lena
authors.initials: L
authors.lastname: Maier-Hein
authors.forename: Aysun
authors.initials: A
authors.lastname: Tekbas
authors.forename: Alexander
authors.initials: A
authors.lastname: Seitel
authors.forename: Frank
authors.initials: F
authors.lastname: Pianka
authors.forename: Sascha A
authors.initials: SA
authors.lastname: Müller
authors.forename: Stefanie
authors.initials: S
authors.lastname: Satzl
authors.forename: Simone
authors.initials: S
authors.lastname: Schawo
authors.forename: Boris
authors.initials: B
authors.lastname: Radeleff
authors.forename: Ralf
authors.initials: R
authors.lastname: Tetzlaff
authors.forename: Alfred M
authors.initials: AM
authors.lastname: Franz
authors.forename: Beat P
authors.initials: BP
authors.lastname: Müller-Stich
authors.forename: I
authors.initials: I
authors.lastname: Wolf
authors.forename: H-U
authors.initials: HU
authors.lastname: Kauczor
authors.forename: B M
authors.initials: BM
authors.lastname: Schmied
authors.forename: H-P
authors.initials: HP
authors.lastname: Meinzer
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000379:methods*; D004867:Equipment Design; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging* / Q000473:pathology*; D008113:Liver Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D008297:Male; D015233:Models, Statistical; D009038:Motion; D009339:Needles; D015203:Reproducibility of Results; D012984:Software; D013552:Swine; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*