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  • 1
    Abstract: The increasing complexity of MR-guided interventions demands high SNR and short image acquisition times. Therefore, a rising number of such procedures is performed in closed-bore MR scanners where patient access is severely restricted. Consequently, safe, accurate, and continuous instrument monitoring and guidance is a mandatory pre-requisite. A combination of an automatic passive tracking technique and a manually steerable instrument holder is proposed to meet the requirements of percutaneous interventions. The setup was tested during LITT as an advanced minimally invasive technique. Our experiments demonstrate the potential of this approach which is suitable for a wide range of interventional applications.
    Type of Publication: Proceeding
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  • 2
    Abstract: In percutanous MR-guided interventions passive markers are used to delineate the position or the trajectory of rigid instruments, e.g. needles. In this work, a modified passive marker and a modified passive tracking pulse sequence are proposed. Based on the 3D position and rotation of the marker an imaging slice is automatically adjusted in real time. Measurements indicate that the marker design combined with the pulse sequence allows an accurate rotation estimation and 3D tracking of rigid instruments. Thus, the choice of an optimal needle trajectory in percutaneous interventions is highly facilitated and under manual control of the operator.
    Type of Publication: Proceeding
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  • 3
    Keywords: Germany ; IN-VIVO ; THERAPY ; VIVO ; imaging ; SYSTEM ; SYSTEMS ; RISK ; TISSUE ; SURGERY ; MAGNETIC-RESONANCE ; BREAST ; TARGET ; IDENTIFICATION ; LESIONS ; LENGTH ; CANCER-THERAPY ; MR imaging ; PATTERN ; monitoring ; ABLATION ; methods ; NECROSIS ; SCANNER ; SCAN ; INTERVENTIONS ; tumours ; biomedical MRI ; actuators ; biomedical transducers ; biomedical ultrasonics ; MR SYSTEMS ; patient monitoring ; SHIFT ; THERMOMETRY ; UTERINE LEIOMYOMAS
    Abstract: Purpose: Focused ultrasound surgery (FUS) is a highly precise noninvasive procedure to ablate pathogenic tissue. FUS therapy is often combined with magnetic resonance (MR) imaging as MR imaging offers excellent target identification and allows for continuous monitoring of FUS induced temperature changes. As the dimensions of the ultrasound (US) focus are typically much smaller than the targeted volume, multiple sonications and focus repositioning are interleaved to scan the focus over the target volume. Focal scanning can be achieved electronically by using phased-array US transducers or mechanically by using dedicated mechanical actuators. In this study, the authors propose and evaluate the precision of a combined robotic FUS setup to overcome some of the limitations of the existing MRgFUS systems. Such systems are typically integrated into the patient table of the MR scanner and thus only provide an application of the US wave within a limited spatial range from below the patient. Methods: The fully MR-compatible robotic assistance system InnoMotion (TM) (InnoMedic GmbH, Herxheim, Germany) was originally designed for MR-guided interventions with needles. It offers five pneumatically driven degrees of freedom and can be moved over a wide range within the bore of the magnet. In this work, the robotic system was combined with a fixed-focus US transducer (frequency: 1.7 MHz; focal length: 68 mm, and numerical aperture: 0.44) that was integrated into a dedicated, in-house developed treatment unit for FUS application. A series of MR-guided focal scanning procedures was performed in a polyacrylamide-egg white gel phantom to assess the positioning accuracy of the combined FUS setup. In animal experiments with a 3-month-old domestic pig, the system's potential and suitability for MRgFUS was tested. Results: In phantom experiments, a total targeting precision of about 3 mm was found, which is comparable to that of the existing MRgFUS systems. Focus positioning could be performed within a few seconds. During in vivo experiments, a defined pattern of single thermal lesions and a therapeutically relevant confluent thermal lesion could be created. The creation of local tissue necrosis by coagulation was confirmed by post-FUS MR imaging and histological examinations on the treated tissue sample. During all sonications in phantom and in vivo, reliable MR imaging and online MR thermometry could be performed without compromises due to operation of the combined robotic FUS setup. Conclusions: Compared to the existing MRgFUS systems, the combined robotic FUS approach offers a wide range of spatial flexibility so that highly flexible application of the US wave would be possible, for example, to avoid risk structures within the US field. The setup might help to realize new ways of patient access in MRgFUS therapy. The setup is compatible with any closed-bore MR system and does not require an especially designed patient table
    Type of Publication: Journal article published
    PubMed ID: 20527572
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