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  • 1
    Keywords: OPTIMIZATION ; tumor ; Germany ; IN-VIVO ; VIVO ; CT ; imaging ; SUPPORT ; SYSTEM ; liver ; TUMORS ; ACCURACY ; computed tomography ; NUCLEAR-MEDICINE ; TIME ; TARGET ; NO ; TRIAL ; TRIALS ; ACQUISITION ; LESIONS ; EXPERIENCE ; RADIOFREQUENCY ABLATION ; REGISTRATION ; tomography ; COMPUTED-TOMOGRAPHY ; MOTION ; TRACKING ; IMAGE REGISTRATION ; nuclear medicine ; ORGAN MOTION ; radiology ; RE ; GUIDANCE ; ABLATION ; radiation therapy ; NUCLEAR ; USA ; SET ; IMPROVEMENT ; navigation ; MEDICINE ; CHALLENGES ; INSERTION ; HEPATIC-TUMORS ; INTERVENTIONS ; tumours ; NEEDLES ; computerised tomography ; needle insertion ; CLINICAL-EVALUATION ; motion compensation ; patient treatment
    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
    Type of Publication: Journal article published
    PubMed ID: 19175098
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  • 2
    Keywords: IN-VITRO ; tumor ; Germany ; human ; MODEL ; THERAPY ; VITRO ; CT ; SYSTEM ; liver ; ACCURACY ; computed tomography ; SURGERY ; TARGET ; REGISTRATION ; STRATEGIES ; COMPUTED-TOMOGRAPHY ; MOTION ; TRACKING ; BIOPSY ; RE ; THERAPIES ; ABLATION ; THIN-PLATE SPLINES ; RESPIRATORY MOTION ; ENGLAND ; THERMAL ABLATION ; navigation ; respiratory liver motion simulator ; POSITION ; INTERVENTIONS ; NEEDLES ; DEVICE ; deformation model ; image-guided systems ; interventional radiology ; needle insertion ; respiratory motion compensation
    Abstract: Computed tomography (CT) guided minimally invasive procedures in the liver, such as tumor biopsy and thermal ablation therapy, require precise targeting of hepatic structures that are subject to breathing motion. To facilitate needle placement, we introduced a navigation system which uses needle-shaped optically tracked navigation aids and a real-time deformation model to continuously estimate the position of a moving target. In this study, we assessed the target position estimation accuracy of our system in vitro with a custom-designed respiratory liver motion simulator. Several real-time compatible transformations were compared as a basis for the deformation model and were evaluated in a set of experiments using different arrangements of three navigation aids in two porcine and two human livers. Furthermore, we investigated different placement strategies for the case where only two needles are used for motion compensation. Depending on the transformation and the placement of the navigation aids, our system yielded a root mean square (RMS) target position estimation error in the range of 0.7 mm to 2.9 mm throughout the breathing cycle generated by the motion simulator. Affine transformations and spline transformations performed comparably well (overall RMS 〈 2 mm) and were considerably better than rigid transformations. When two navigation aids were used for motion compensation instead of three, a diagonal arrangement of the needles yielded the best results. This study suggests that our navigation system could significantly improve the clinical treatment standard for CT-guided interventions in the liver
    Type of Publication: Journal article published
    PubMed ID: 18432412
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