Robotic versus Freehand Needle Positioning in CT-guided Ablation of Liver Tumors: A Randomized Controlled Trial

Purpose: To compare the accuracy of freehand versus robotic antenna placement in CT-guided microwave ablation (MWA) of liver tumors.

Materials and Methods: This study was conducted as a prospective single-center nonblinded randomized controlled trial (Netherlands Trial Registry, NTR6023). Eligible study participants had undergone clinically indicated CT-guided MWA of liver tumors and were able to receive a CT contrast agent. Randomization was performed per tumor after identification on contrast material-enhanced CT images. The primary outcome was the number of antenna repositionings, which was compared by using the Mann-Whitney U test. Secondary outcomes were lateral targeting error stratified by in-plane and out-of-plane targets and targeting time.

Results: Between February 14 and November 12, 2017, 31 participants with a mean age of 63 years (range, 25-88 years) were included: 17 women (mean age, 57 years; range, 25-77 years) and 14 men (mean age, 70 years; range, 52-88 years). The freehand study arm consisted of 19 participants, while the robotic study arm consisted of 18 participants; six participants with multiple tumors were included in both arms. Forty-seven tumors were assessed; five tumors were excluded from the analysis because of technical limitations. In the robotic arm, no antenna repositioning was required. In the freehand arm, a median of one repositioning was required (range, zero to seven repositionings; P <.001). For out-of-plane targets, lateral targeting error was 10.1 mm +/- 4.0 and 5.9 mm +/- 2.9 (P = .007) for freehand and robotic procedures, respectively, and for in-plane targets, lateral targeting error was 6.2 mm +/- 2.7 and 7.7 mm +/- 5.9, respectively (P = .51). Mean targeting time was 19 minutes (range, 8-55 minutes) and 36 minutes (range, 3-70 minutes; P = .001) for freehand and robotic procedures, respectively.

Conclusion: Robotic antenna guidance reduces the need for antenna repositioning in microwave ablation to accurately target liver tumors and increases accuracy for out-of-plane targets. However, targeting time was greater with robotic guidance than with freehand targeting. (C) RSNA, 2019