C omputed tomography (CT)-guided interventions such as biopsy, catheter drainage, and radiofrequency ablation are widely used as minimally invasive diagnostic and therapeutic procedures. The use of CT fluoroscopy helps to reduce the procedure time, patient radiation dose, and complications, particularly in risky locations near large vessels and the gastrointestinal tract. Reported success rates of conventional CT and CT fluoroscopy-guided biopsies range from 90%-100% and 83%-100%, respectively (1-3). However, CT-guided interventions are time-consuming procedures and should be performed by experienced interventional radiologists. In addition, significant radiation exposures occur to medical personnel when CT fluoroscopic guidance is used.Recently, development of the robotic surgery platform has provided a tool that can overcome many of the limitations of conventional surgery. Augmented dexterity enabled by the endowristed movements, software filtration of the surgeon's movements, and enhanced vision provided by the stereoscopic camera combine to allow steady and careful dissection and prompt and precise suturing (4, 5). These advantages of the robotic system can also enable accurate targeting with diverse angulation of the robotic arm in CT-guided biopsy and tumor ablation. Furthermore, robotic intervention can potentially decrease procedure time and radiation exposure to both patients and doctors (6).We developed a robotic system with path-planning and needle-placement functions under CT guidance. The purpose of this experiment was to assess the stability and accuracy of our CT-guided intervention robot using an abdominal phantom.
Methods
Robot systemThe interventional robotic system used in this study is a master-slave type robotic system for CT-guided needle intervention jointly developed by our hospital and a manufacturer (Fig. 1).
I N T E R V E N T I O N A L R A D I O LO G Y O R I G I N A L A R T I C L E
PURPOSEWe aimed to evaluate the accuracy of a needle-placement robot for biopsy and radiofrequency ablation on an abdominal phantom.
METHODSA master-slave robotic system has been developed that includes a needle-path planning system and a needle-inserting robot arm with computed tomography (CT) and CT fluoroscopy guidance. For evaluation of its accuracy in needle placement, a commercially available abdominal phantom (Model 057A; CIRS Inc.) was used. The liver part of the phantom contains multiple spherical simulated tumors of three different size spheres. Various needle insertion trials were performed in the transverse plane and caudocranial plane two nodule sizes (10 mm and 20 mm in diameter) to test the reliability of this robot. To assess accuracy, a CT scan was performed after each trial with the needle in situ.
RESULTSThe overall error was 2 mm (0-2.6 mm), which was calculated as the distance from the planned trajectory before insertion to the actual needle trajectory after insertion. The standard deviations of the insertions on two nodules (10 mm and 20 mm in diameter) were 0.5 mm and 0.2 mm, respect...