Gerlig Widmann

Errors and error management in image-guided craniomaxillofacial surgery

Image-guided surgery is being increasingly used in craniomaxillofacial tumor surgery, trauma surgery, orthognathic surgery, and implant surgery. Compared with conventional procedure, treatment planning is performed on the computer based on previously obtained 3-dimensional imaging data, and the surgical procedure is carried out under guidance of a surgical navigation system. Accuracy is of vital importance for the clinical application of this sophisticated technology. All errors are integrative and depend on many factors, including image modality, registration technique, tracking technology, and application type. Knowledge of errors and error management is important to understand the possibilities and limitations of different image-guided surgical approaches. The aim of this review is to provide a comprehensive overview on the different errors and error management strategies in image-guided craniomaxillofacial surgery.

Navigated CT-guided interventions.

Diagnostic and therapeutic CT‐ guided percutaneous interventions are clinical routine in interventional radiology. Image‐guided navigation systems visualize the internal anatomy during interventions in real time not necessitating continuous image acquisition. Although multiple 3D image‐guidance devices have been developed and used by several surgical disciplines in the last few years, they have not yet been fully applied by the interventional radiologist. The aim of this article is to review the currently performed methods of CT‐guided percutaneous interventions and to discuss the potential benefits of newly developed 3D‐ navigation systems.

Frameless Stereotactic Cannulation Of The Foramen Ovale For Ablative Treatment Of Trigeminal Neuralgia

OBJECTIVE: Ablative neurosurgical treatment of trigeminal neuralgia, including percutaneous radiofrequency thermocoagulation, requires cannulation of the foramen ovale. To maximize patient security and cannulation success, a frameless stereotactic system was evaluated in a phantom study, a cadaveric study, and a preliminary clinical trial. METHODS: Frameless stereotaxy using an optical navigation system, an aiming device, and a noninvasive vacuum mouthpiece-based registration and patient fixation technique was used for the targeting of a test body based on 1-, 3-, and 5-mm axial computed tomographic slices and of the foramen ovale in three cadavers and 15 patients based on 3-mm axial computed tomographic slices. RESULTS: The mean normal (x/y) localization accuracy/standard deviation (n = 360) was 1.31/0.67 mm (1-mm slices), 1.38/0.65 mm (3-mm slices), and 1.84/0.96 mm (5-mm slices). Significantly better results were achieved with 1- and 3-mm slices when compared with 5-mm slices (P < 0.001). The foramen ovale (3 × 6 mm) was successfully cannulated at the first attempt in all cadavers and patients, which indicates clinical localization accuracies better than 1.5 mm in the anteroposterior and 3 mm in the medial-lateral directions. CONCLUSION: Based on the noninvasive Vogele-Bale-Hohner vacuum mouthpiece, there is no need for invasive head clamp fixation. Imaging, real laboratory simulation, and the actual surgical intervention can be separated in time and location. The presented data suggest that frameless stereotaxy is a predictable and reproducible procedure, which may enhance patient security and cannulation success independent of the surgeon’s experience.

State-of-the-art HR-US imaging findings of the most frequent musculoskeletal soft-tissue tumors

High resolution ultrasound (HR-US) including color Doppler ultrasound (CD-US), power Doppler ultrasound (PD-US), and spectral wave analysis (SWA), is a broadly available, non-invasive and relatively low-cost modality without ionizing radiation. It is increasingly used for initial assessment of an ambiguous musculoskeletal soft-tissue lesion and for sonographically guided core biopsy. The aim of this review is to provide sonographic findings of the most frequent benign and malign soft-tissue lesions. By this essay, we can show that combined with clinical features, with information on tumor-localization and patient age, many musculoskeletal lesions may be successfully characterized by HR-US. In contrast, a mere morphologic assignment of some fibrous tumors and malignant lesions remains often impossible; however, certain CD-US signs such as anarchic vascular architecture or arteriovenous shunting may be very helpful indicators for malignancy. HR-US offers a simple, quick, and reliable first-line examination of musculoskeletal soft-tissue lesions and may have an important role in the diagnostic work-up followed by magnetic resonance or multimodality imaging and guided core biopsy.

Stereotaxy: Breaking the limits of current radiofrequency ablation techniques

Radiofrequency ablation (RFA) allows for local curative tumor treatment by inducing coagulation necrosis with high-frequency alternating current. However, the tumor size is the major limiting factor due to a mismatch of the tumor volume and the induced necrotic zone. RFA probes have to be optimally distributed in and around the tumor in order to produce overlapping ablation zones. Due to different guidance and ablation strategies the result is strongly operator dependent and there is a lack of reliability. These challenges can be managed by 3D-planning using a frameless stereotactic navigation system, allowing for the simultaneous display of multiple trajectories. The spatial information gained from 3D imaging is available in coordinates and thus forms an accurate input for performing the intervention. Stereotaxy enables highly accurate probe positioning. Stereotactic radiofrequency ablation (SRFA) may substantially improve the safety and efficacy in clinical practice, especially in the treatment of large and irregularly shaped tumors. The proposed methods may also be used for similar percutaneous local tumor treatments.

Frameless stereotactic targeting devices: technical features, targeting errors and clinical results

Brain biopsies (BB) and depth electrode placements (DEP) are increasingly performed using frameless stereotactic targeting devices. This paper is intended to provide a comprehensive review of the technical features, targeting errors and clinical results.

Target registration and target positioning errors in computer-assisted neurosurgery: proposal for a standardized reporting of error assessment.

Assessment of errors is essential in development, testing and clinical application of computer‐assisted neurosurgery. Our aim was to provide a comprehensive overview of the different methods to assess target registration error (TRE) and target positioning error (TPE) and to develop a proposal for a standardized reporting of error assessment.

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.

Tumour ablation: technical aspects.

Abstract Image-guided percutaneous radiofrequency ablation (RFA) is a minimally invasive, relatively low-risk procedure for tumour treatment. Local recurrence and survival rates depend on the rate of complete ablation of the entire tumour including a sufficient margin of surrounding healthy tissue. Currently a variety of different RFA devices are available. The interventionalist must be able to predict the configuration and extent of the resulting ablation necrosis. Accurate planning and execution of RFA according to the size and geometry of the tumour is essential. In order to minimize complications, individualized treatment strategies may be necessary for tumours close to vital structures. This review examines the state-of-the art of different device technologies, approaches, and treatment strategies for percutaneous RFA of liver tumours.

Comparison of freehand-navigated and aiming device-navigated targeting of liver lesions

Accurate needle placement is crucial for the success of percutaneous radiological needle interventions. We compared three guiding methods using an optical‐based navigation system: freehand, using a stereotactic aiming device and active depth control, and using a stereotactic aiming device and passive depth control.