Marion Haidu

Respiratory motion control for stereotactic and robotic liver interventions

Control of respiratory motion is an essential prerequisite for stereotactic computer‐assisted and robotic interventions in the liver.

Multipolar radiofrequency ablation using 4-6 applicators simultaneously: A study in the ex vivo bovine liver

In this study the volume and shape of coagulation zones after multipolar radiofrequency ablation (RFA) with simultaneous use of 4-6 applicators in the ex vivo bovine liver were investigated. The RF-applicators were positioned in 13 different configurations to simulate ablation of large solitary tumors and simultaneous ablation of multiple lesions with 120 kJ of applied energy/session. In total, 110 coagulation zones were induced. Standardized measurements of the volume and shape of the coagulation zones were carried out on magnetic resonance images and statistically analyzed. The coagulation zones induced with solitary applicators and with 2 applicators were imperceptibly small and incomplete, respectively. At 20mm applicator distance, the total ablated volume was significantly larger if all applicators were arranged in a single group compared to placement in 2 distant applicator groups, each consisting of 3 applicators (p=.001). The mean total coagulated volume ranged from immeasurably small (if 6 solitary applicators were applied simultaneously) to 74.7 cc (if 6 applicators at 30 mm distance between neighboring applicators were combined to a single group). Applicator distance, number and positioning array impacted time and shape. The coagulation zones surrounding groups with 4-6 applicators were regularly shaped, homogeneous and completely fused, and the axial diameters were almost constant. In conclusion, multipolar RFA with 4-6 applicators is feasible. The multipolar simultaneous mode should be applied for large and solitary lesions only, small and multiple tumors should be ablated consecutively in standard multipolar mode with up to 3 applicators.

Targeting accuracy of CT-guided stereotaxy for radiofrequency ablation of liver tumours

Abstract The targeting accuracy during CT-guided stereotactic radiofrequency ablation (SRFA) of liver tumours was evaluated in a clinical study. Patients under general anaesthesia were immobilized using a vacuum cushion and respiratory motion control was based on temporary disconnections of the endotracheal tube. An optical-based navigation system was used for 3D trajectory planning and needle placement via a stereotactic aiming device. A control CT with the needles in place was fused with the planning CT for accuracy evaluation. Sub-analysis was performed for “location” (liver segments II – VIII), “approach” (intercostal or transabdominal), “properties” (clear parenchymal, subcapsular, subphrenic, fat, and subphrenic plus fat), and “path length”. In 20 patients with 35 liver lesions, a total of 145 needles were placed with mean (±SD) lateral errors of 3.6 ± 2.5 mm at the needle tip, angular errors of 1.3° ± 1.2°, and longitudinal errors at the needle tip of -7.4 ± 6.2 mm. No puncture-related complications were noted. No significant differences of angular errors between segments, approach and properties were recorded. Long paths correlated with smaller angular errors. CT-guided stereotaxy can be considered safe and provided precise multiple needle placement for SRFA of liver lesions at arbitrary trajectories in various segments and locations.

Stereotactic Radiofrequency Ablation: Providing New Dimensions in Interventional Oncology

Purpose: Radiofrequency ablation (RFA) has become widely accepted as the first-line local tumor therapy of surgical untreatable primary and secondary liver malignancies. Main risk factors for residual tumor and local recurrence are tumor size (> 3cm), imprecise probe placement and insufficient overlapping of multiple ablation spheres. Our aim was to evaluate if stereotactic RFA may improve the results of conventional techniques. Materials/Methods: Stereotactic RFA of 92 primary and 67 secondary liver tumors in 68 patients was performed. After general anesthesia the patient was rigidly immobilized on the CT table. A contrast-enhanced helical CT scan (2 mm slice thickness) was obtained with respiratory triggering. Pathways for multiple probes were planned on a navigation system in order to cover the whole tumor volume by overlapping necroses. Depending on the size of the tumor (0.5-11 cm, mean: 2.9 cm) pathways for the placement of 1-24 probes were planned. After registration a targeting device was adjusted for every path. In maximal expiration one after another coaxial needle was advanced to the preplanned depth. A native control CT was performed for verification of needle placement. RFA followed subsequently. Residual tumor was determined on a contrast-enhanced CT after 1 month, recurrence on CTs at 3 months intervals (mean follow-up: 9.2 months). Results: Residual tumor was found in 12/159 lesions (2.7%) of which 10 could be successfully retreated. Recurrences were found in 12/147 (8.2%) lesions, of which 3 were successfully re-ablated. Recurrence rate for lesions 5 cm (n=19) was 10.5%. Conclusion: Stereotaxy allows for precise positioning and 3D-distribution of RFA probes in order to achieve an overlapping ablation zone for even large lesions. It decreases the local tumor recurrence rate as compared to conventional CT/US-guided RFA.

Stereotaktische Radiofrequenzablation Alternative zur Leberresektion bei kolorektalen Lebermetastasen

Fast 50 Prozent der Patienten mit kolorektalem Karzinom entwickeln Lebermetastasen. Mehrere retrospektive Analysen zeigen, dass die chirurgische Resektion das Überleben deutlich verlängert. An spezialisierten Zentren konnten in Kombination mit effektiver systemischer Therapie 5-Jahresüberlebensraten von 30 bis knapp 60 Prozent erzielt werden.