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Biomedical subjects

Rüdiger Marmulla

Publications and source records attributed to Rüdiger Marmulla.

12 recordsLinked to original sources
PubMed2006

The influence of computed tomography motion artifacts on computer-assisted surgery.

PURPOSE: Motion artifacts can significantly deteriorate the precision of a computer-assisted surgical intervention because they destroy the isometric representation of tomographic pictures. In the context of a study, the influence of typical motion artifacts on the precision of markerless laser registration in image-guided oral and maxillofacial surgery was analyzed, and quality factors for evaluation of the isometry of a computed tomography (CT) dataset were determined. PATIENTS AND METHODS: Twenty patients underwent markerless registration, the precision being determined by means of intraoral evaluation markers. Then the 20 CT datasets were used for simulation of a typical motion artifact. The precision of the overlay of the dataset was checked again on the navigation workstation, in absence of the patient. The navigation system used was the Surgical Segment Navigator SSN++ (University of Heidelberg, Heidelberg, Germany). RESULTS: The motion artifacts reduced the average patient registration from 1 to 4 mm. Quality factors for the isometry of a CT dataset were: the volume enclosed between the soft tissue mantles of the preoperative CT dataset and the intraoperative laser scan dataset, as well as the orientation of the normal vectors on the 3-dimensional reconstruction of the CT dataset. CONCLUSION: The isometry of a CT dataset should always be checked before performance of a computer assisted surgical intervention because anisometric datasets result in inaccurate patient registration and navigation.

Artifacts↗
PubMed2005

Physiological shift of facial skin and its influence on the change in precision of computer-assisted surgery.

Methods of recording landmarks on the facial skin without the use of markers have become increasingly accepted in image-guided surgery. However, position or muscular activity may change the skin's geometry and generate a lack of agreement between the facial contours recorded before and those recorded during the operation. In the present study, we measured this physiological shift of facial skin and evaluated its influence on the accuracy of stereotactic recording. We made laser-scans of the skin of 20 conscious patients while they were sitting and lying, both at rest and when smiling. The laser-scans were referenced to the corresponding computed tomographic dataset, and the accuracy of the recording was calculated. Gravitational or muscular shifts of the skin reduced the mean (S.D.) accuracy of recording to 1.7 (0.3)mm. The loss of accuracy was significantly correlated with the dynamic and gravitational wrinkling of the facial skin and with the body mass index of each patient.

Adolescent↗
PubMed2005

Template-based registration for image-guided maxillofacial surgery.

PURPOSE: Fiducial marker registration using bone screws is a proved and tested method for patient-to-image registration for image-guided surgery of the head. The use of intraoral fiducial markers mounted on a template for the maxillary dentition is a less invasive alternative and is in use for intraoral image-guided surgery. The aim of this study was to verify if this method is sufficiently accurate for extraoral use. MATERIALS AND METHODS: Registration was performed using 243 different configurations of fiducial markers mounted on a maxillary template. The accuracy of the identification of artificial skull-mounted targets located in surgically relevant locations was determined for each registration. RESULTS: Targeting accuracy was sufficient for image-guided surgery of the maxilla, the midface, the orbit, and the pterygopalatine fossa. In the regions of the calvarium, however, average target registration error was > or =1.5 mm. Average target registration error was >3 mm. CONCLUSION: Fiducial marker registration based on a maxillary template is a safe and non-invasive alternative to bone-mounted fiducial markers for image-guided surgery in the regions of orbit, face, maxilla, and pterygopalatine fossa.

Bone Screws↗
PubMed2005

Intraoperative augmented reality: the surgeons view.

Augmented Reality (AR) is a promising tool for intraoperative visualization. Two different AR systems, one projector based, one based on see-through glasses were used on patients. The task was the transfer of preoperative planning into the intraoperative reality, or the visualization of space occupying lesions, respectively. The intraoperative application of both systems is discussed from the surgeons point of view.

General Surgery↗
PubMed2005

Visualization of surgical 3D information with projector-based augmented reality.

For visualizing surgical information (operation plans) directly onto the patient a projector-based augmented reality system is used for cranio-maxillofacial surgery. A prototype is introduced which has been evaluated in the first clinical cases. In a new setup with a second video projector it is now possible to give additionally 3D information for localization and orientation (6DoF). With this method the repositioning of a bone segment is intuitive and exact applicable.

Germany↗
PubMed2004

Advanced surface-recording techniques for computer-assisted oral and maxillofacial surgery.

Markerless recording of patients based on natural anatomical surfaces makes planning of computer-assisted surgery much easier, as it is not necessary to place and measure markers. Recording of the surgical site with a laser scan takes the place of conventional marker-based recording. We have used auricles as well as the maxilla and mandible as reproducible surfaces. The geometric congruence of the laser scanned surface with the corresponding surface in the computed tomographs data-set and the applied intraoperative accuracy after recording with a laser scanner have been evaluated, and the system was successful in the maxilla (mean precision: 0.8mm, standard deviation: 0.3mm). In the mandible, the tongue and mobile floor of the mouth led to geometric incongruence and inadequate laser scanning. An exact recording using auricles was possible only as long as the auricles had not been temporarily deformed by the head support during CT imaging.

Ear, External↗
PubMed2004

Markerless laser registration in image-guided oral and maxillofacial surgery.

PURPOSE: The use of registration markers in computer-assisted surgery is combined with high logistic costs and efforts. Markerless patient registration using laser scan surface registration techniques is a new challenging method. The present study was performed to evaluate the clinical accuracy in finding defined target points within the surgical site after markerless patient registration in image-guided oral and maxillofacial surgery. PATIENTS AND METHODS: Twenty consecutive patients with different cranial diseases were scheduled for computer-assisted surgery. Data set alignment between the surgical site and the computed tomography (CT) data set was performed by markerless laser scan surface registration of the patient's face. Intraoral rigidly attached registration markers were used as target points, which had to be detected by an infrared pointer. The Surgical Segment Navigator SSN++ has been used for all procedures. SSN++ is an investigative product based on the SSN system that had previously been developed by the presenting authors with the support of Carl Zeiss (Oberkochen, Germany). SSN++ is connected to a Polaris infrared camera (Northern Digital, Waterloo, Ontario, Canada) and to a Minolta VI 900 3D digitizer (Tokyo, Japan) for high-resolution laser scanning. RESULTS: Minimal differences in shape between the laser scan surface and the surface generated from the CT data set could be detected. Nevertheless, high-resolution laser scan of the skin surface allows for a precise patient registration (mean deviation 1.1 mm, maximum deviation 1.8 mm). CONCLUSIONS: Radiation load, logistic costs, and efforts arising from the planning of computer-assisted surgery of the head can be reduced because native (markerless) CT data sets can be used for laser scan-based surface registration.

Data Display↗
PubMed2003

Laser-scan-based navigation in cranio-maxillofacial surgery.

BACKGROUND: In computer-assisted surgery, a correlation between a volume data set and the surgical site is required in order to localize the patient's head on the operating table. Registration markers are commonly used for this procedure. However, the marker registration is associated with high logistics, since the markers have to be placed prior to data set acquisition and have to be kept in their position until the patient enters the operating room. This study deals with a new markerless registration method in cranio-maxillofacial surgery that is based on a high-resolution laser-scan of the patient's (relaxed) skin surface. PATIENTS: 20 patients with tumours, bone malformations or foreign bodies, scheduled for computer-assisted surgery, were involved in the study. STUDY DESIGN: The clinically applied accuracy of the laser-scan-based registration was measured through additionally placed registration markers. The inherent precision of the laser-scan registration system was controlled in phantom studies. RESULTS: The clinically applied accuracy of the new laser-scan-based registration technique ranged between 0.2 and 1.8 mm with a mean deviation of 1.1mm and a standard deviation of 0.3 mm. CONCLUSION: The facial skin surface can serve as a sufficiently stable and invariable reference base in order to register patients for computer-assisted cranio-maxillofacial surgery.

Algorithms↗
PubMed2003

Soft tissue scanning for patient registration in image-guided surgery.

Prior to an image-guided surgical intervention, a correlation between the patient's data set and the surgical site is required. This study introduces a markerless registration method for cranio-maxillofacial surgery that is based on a high-resolution laser scan of the patient's skin surface. The Surgical Segment Navigator SSN++ rejects contaminated surface measurements in a way similar to the bluescreen technique. Acquisition of the spatial position and the corresponding surface color of each laser-scanned point facilitates this bluescreen method, removing points with a defined surface color, e.g., blue or green points. The accuracy of the laser-scan-based registration was measured via additional intraoral titanium-markers. These markers served only to check the accuracy of the markerless registration process. In twelve patients, the stability and accuracy of the data set alignment was evaluated for high-(300,000 surface points), medium-, and low-resolution (down to 3,750 surface points) laser scanning. The accuracy of the registration technique was best for high-resolution laser scanning (mean deviation 1.1 mm; maximum deviation 1.8 mm). Low-resolution laser scans revealed inaccuracies up to 6 mm.

Face↗
PubMed2003

Development and first patient trial of a surgical robot for complex trajectory milling.

OBJECTIVE: Today's surgical robots normally perform "simple" trajectories, e.g., assisting as tool-holding devices in neurosurgery, or milling linear paths for cavities in total hip replacement. From a clinical point of view, it is still a complex undertaking to implement robots in the operating room. Until now, robot systems have not been used in patient trials to mill "complex" trajectories, which involve many positional and orientation changes and are often necessary in cranio-maxillofacial (CMF) surgery. This paper presents the RobaCKa surgical robot system, which allows more precise execution of surgical interventions and milling of "complex" trajectories. MATERIALS AND METHODS: The main components of the RobaCKa system are a (former) CASPAR robot system, a POLARIS system, and a force-torque sensor. RESULTS: In the first patient trial (April 2003) the planned trajectory was executed with an error of 0.66 +/- 0.2 mm. CONCLUSIONS: The use of former industrial robots for surgical applications is possible but complex. The advantages are improved precision and quality and the possibility of documentation. The use of such systems is normally limited to research institutions or large clinics, because it is hardly possible to implement the necessary technical and logistic efforts in routine surgical work.

Craniotomy↗