Clinical Utility of Real-time Fusion Guidance for Biopsy and Ablation

Abstract

Purpose-To demonstrate utility, accuracy, and clinical outcomes of electromagnetic tracking and multi-modality image fusion for guidance of biopsy and radiofrequency (RF) ablation procedures.Materials and Methods-A combination of conventional image guidance (ultrasound/ computed tomography (CT)) and a research navigation system were used in 40 patients undergoing biopsy or RF ablation to assist in target localization and needle/electrode placement. The navigation system displays electromagnetically tracked needles and ultrasound images relative to a pre-procedural CT. Additional images (prior positron emission tomography (PET) or magnetic resonance imaging (MRI)) can be fused with the CT as needed. Needle aiming with and without tracking were compared, the utility of navigation for each procedure was assessed, the system's off-target tracking error for two different registration methods was evaluated, and setup time recorded.Results-The tracking error was evaluable in 35 of 40 patients. A basic tracking error of 3.8 ± 2.3 mm was demonstrated using skin fiducials for registration. The error improved to 2.7 ± 1.6 mm when using prior internal needle positions as additional fiducials. Real-time fusion of ultrasound with CT and registration with prior PET and MRI were successful and provided clinically relevant guidance information, enabling 19 of the 40 procedures.Conclusion-The spatial accuracy of the navigation system is sufficient to display clinicallyrelevant image guidance information during biopsy and RF ablation. Breath holding and respiratory gating are effective in minimizing the error associated with tissue motion. In 48% of cases, the navigation system provided information critical for successful execution of the

Fusion imaging of contrast-enhanced ultrasound and contrast-enhanced CT or MRI before radiofrequency ablation for liver cancers

“…Thirdly, the registration error was not analyzed in this study; however, the spatial accuracy of this system had already been verified by some previous studies. 41,42 Finally, the confidence in performing RFA depends on several factors other than the lesion localization. This study mentioned the level of confidence in performing the RFA procedure with the available guidance, which might be subjective.…”

Real-time FDG PET Guidance during Biopsies and Radiofrequency Ablation Using Multimodality Fusion with Electromagnetic Navigation

“…In 21 patients, an automatic image registration method was used to rigidly align PET and CT images in the vicinity of the desired PET target ( 18 ). In four patients in whom the navigational system for tracked instruments was employed, the preprocedural PET data set was coregistered with intraprocedural CT and US data sets by using manual registration.…”

Organ-focused mutual information for nonrigid multimodal registration of liver CT and Gd–EOB–DTPA-enhanced MRI

“…ablation of focal liver tumors assisted by the fusion of preoperative CT/MRI and intraoperative ultrasound (Jung et al, 2012), the target selection and calculation of the lesions ablative volume from the pre-procedure images must accurately be blended with the realtime ultrasound in order to place the thermal electrode on the selected targets. Millimetric displacement and tracking inaccuracy due to minor errors in the registration step may cause treatment failure (Krücker et al, 2011). The accuracy in the preoperative step registering the CT and the MRI becomes as important as the intraoperative step.…”