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Biomedical subjects

Georg Eggers

Publications and source records attributed to Georg Eggers.

13 recordsLinked to original sources
PubMed2006

Age- and tooth-related pulp cavity signal intensity changes in healthy teeth: a comparative magnetic resonance imaging analysis.

OBJECTIVE: To determine if it is possible to measure age-related pulp cavity signal intensity changes by using magnetic resonance imaging (MRI). STUDY DESIGN: Dental pulp cavity signal intensities were assessed in 92 test subjects on the basis of MRI signal intensity measurements at freely defined regions of interest by using T1 gradient echo sequences before and after contrast-agent administration. Relative signal intensity differences were calculated and provided the basis for age- and tooth-related comparisons. RESULTS: Significant signal intensity differences were noted between the oldest (born between 1930 and 1959) and the youngest (born after 1980) test subjects and the other groups (P < .05). In addition, the first molars showed significantly lower signal intensity differences than the second molars (P < .05). CONCLUSION: Magnetic resonance imaging can be used to determine pulp cavity signal-intensity changes with age.

Age Factors↗
PubMed2006

Augmented reality with fibre optics.

In this paper we present the concept and the first results of the Fibre Optic Pointer - a miniaturized Augmented Reality system for craniofacial surgery. The objective is the integration into surgical instruments.

Craniofacial Abnormalities↗
PubMed2005

Infiltrating basal cell carcinoma of the neck 34 years after irradiation of an haemangioma in early childhood. A case-report.

A case of a 34-year-old Caucasian male is presented with a basal cell carcinoma deeply infiltrating the structures of the neck, including skeletal muscles and reaching the parotid gland. Radical surgical removal under meticulous histological control was performed. 18 months postoperatively, the patient is still free of recurrence. Thirty years ago the patient had undergone radiotherapy for an infantile haemangioma of the skin of the neck. The effects of this treatment when given in childhood in the aetiology of a basal cell carcinoma are discussed.

Adult↗
PubMed2005

Artefacts in magnetic resonance imaging caused by dental material.

A common problem in computer tomography (CT) based imaging of the oral cavity is artefacts caused by dental restorations. The aim of this study was to investigate whether magnetic resonance imaging (MRI) of the oral cavity would be less affected than CT by artefacts caused by typical dental restorative alloys. In order to assess the extent of artefact generation, corresponding MRI scans of the same anatomic region with and without dental metal restorations were matched using a stereotactic frame. MRI imaging of the oral and maxillofacial region could be performed without reduction of the image quality by metallic dental restorations made from titanium, gold or amalgam. Dental restorations made from titanium, gold or amalgam did not reduce the image quality of the MRI sequence used in imaging of the oral and maxillofacial region for dental implant planning. In this respect MRI is superior to CT in implant planning.

Animals↗
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

Accuracy of image-guided implantology.

OBJECTIVES: The accuracy of two commercially available systems for image-guided dental implant insertion based on infrared tracking cameras was compared with manual implantation. MATERIAL AND METHODS: Phantoms of partially edentulous mandibles were used. In a master phantom, pilot boreholes for dental implants were placed. These boreholes were reproduced in slave phantoms using either of the two image-guided systems and manual implantation. The resulting positions were determined using a coordinate measurement machine and compared with the master model. RESULTS: In comparison with manual implantation, the difference of borehole positions to the master phantom was significantly lower using either of the systems for image-guided implant insertion. CONCLUSION: Image-guided insertion of dental implants is significantly more accurate than manual insertion. However, the accuracy that can be achieved with manual implantation is sufficient for most clinical situations.

Cephalometry↗
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

Histological features and malignant transformation of inverted papilloma.

Inverted papilloma (IP) is a primarily benign epithelial neoplasm with a propensity to transform to squamous cell carcinoma (SCC). Neither the etiology of IP nor the factors responsible for malignant transformation are fully known to date. A considerable number of histopathological grading systems have been suggested. It was the aim of this study to find histological parameters in IP that allow a prognosis concerning the occurrence of malignant transformation. In a group of 93 cases of IP, the patients' records, histological specimens and a questionnaire were evaluated. Thirteen patients had suffered a recurrence of a previously treated IP. SCC in the IP had been diagnosed in 12 of the cases. The histological specimen showed increased counts of mitosis and dyscariosis in the IP. All other histological parameters did not show a significant difference between the groups. History and symptoms proved to be nonspecific as well. Patients in the group with SCC were significantly older at the first diagnosis of IP than patients without carcinoma. This group also included a higher portion of male patients. Patients fulfilling the named histological criteria combined with male gender and higher age are a high-risk group in the necessary long-term follow-up.

Age Factors↗
PubMed2004

Piezosurgery: an ultrasound device for cutting bone and its use and limitations in maxillofacial surgery.

Piezosurgery uses modulated ultrasonic vibration to allow controlled cutting of bony structures. Delicate bony structures can be cut easily and with great precision, without destruction of soft tissue. We have found this device useful when exact cutting of thin bones is essential. However, it is of only limited use in cutting thick bones and in regions with limited access.

Bone and Bones↗
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↗
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↗