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Biomedical subjects

R Marmulla

Publications and source records attributed to R Marmulla.

At least 19 recordsLinked to original sources
PubMed2006

Image-to-patient registration techniques in head surgery.

Frame-based stereotaxy was developed in neurosurgery at the beginning of the last century, evolving from atlas-based stereotaxy to stereotaxy based on the individual patient's image data. This established method is still in use in neurosurgery and radiotherapy. There have since been two main developments based on this concept: frameless stereotaxy and markerless registration. Frameless stereotactic systems ('navigation systems') replaced the cumbersome stereotactic frame by mechanically and later also optically or magnetically tracked instruments. Stereotaxy based on the individual patient's image data introduced the problem of patient-to-image data registration. The development of navigation systems based on frameless stereotaxy has dramatically increased its use in surgical disciplines other than neurosurgery, but image-guided surgery based on fiducial marker registration needs dedicated imaging for registration purposes, in addition to the diagnostic imaging that might have been performed. Markerless registration techniques can overcome the resulting additional cost and effort, and result in more widespread use of image-guided surgery techniques. In this review paper, the developments that led to today's navigation systems are outlined, and the applications and possibilities of these methods in the field of maxillofacial surgery are presented.

Cephalometry↗
PubMed2005

[Markerless patient registration. A new technique for image-guided surgery of the lateral base of the skull].

BACKGROUND: Markerless patient registration is a new procedure that may reduce logistical efforts and possibly also the radiation load on the patients prior to a computer-assisted intervention. Congruent surfaces, such as bone surfaces or skin surfaces, represented in a data set and in the surgical site, can be overlapped with the help of surface matching. Hitherto, these techniques were performed by using the periorbital and frontal skin of the face. The present clinical study assessed the usability of the auricle as a skin structure for markerless patient registration in lateral skull base surgery. PATIENTS AND METHODS: The periauricular precision of the navigation system SSN was investigated clinically in ten patients. Radiopaque registration markers in the periauricular region served as a target in order to evaluate the markerless registration method. RESULTS: Exact patient registration failed in five cases due to temporary deformation of the auricle caused by the head support during CT imaging. An excellent patient registration (mean target registration error = 0.9+/-0.2 mm) was found as long as the auricles had not been temporarily deformed during CT imaging. CONCLUSION: Laser-scan registration of the auricle reduces logistics in image-guided lateral skull base surgery. The problem of temporary deformation of the auricle during CT imaging might be solved by an appropriate opening in the head support at the level of the auricles.

Humans↗
PubMed2005

An augmented reality system for image-guided surgery.

The introduced new developed navigation system is a High Intensity Approach Light System for augmented reality in image-guided surgery. The surgeon follows the projected approach lights with his ordinary surgical instruments. Thus, tracked instruments are not necessary with this system.

Humans↗
PubMed2005

[A new method for computer-assisted orbitotomies].

BACKGROUND: Surgical planning and tumor margins from preoperative image data sets can be transferred to the surgical site by use of computer-assisted navigation systems. Usually registration markers are placed prior to image data acquisition in order to correlate the patient's preoperative image data set with his/her position in the operating room. Pointers are commonly used for navigation, and the position of the pointer within the surgical site is compared to its position within the image data set. With a new navigation system, patient registration can be performed without registration markers. Tumor margins and osteotomy lines can be projected onto the surgical site. MATERIALS AND METHODS: With the new navigation system, which has been developed by the Sonderforschungsbereich 414 of the Deutsche Forschungsgemeinschaft, markerless patient registration is performed using the contours of the patient's face. A scanner is mounted above the operating table, which detects the surface of the surgical site intraoperatively. Osteotomy lines and tumor margins are projected onto this surface using an intense beamer. The procedure is illustrated for a patient with a meningeal tumor of the orbit. RESULTS: Patients can be registered with an accuracy of 1 mm. Pointers are not required to transfer the data on the surgical site. Furthermore, monitors are no longer required, since the information is projected directly on the patient's surface. CONCLUSIONS: Surgical planning and tumor margins can exactly be visualized within the surgical site. Ergonomics are especially improved for navigated orbitotomies via a coronal approach.

Adult↗
PubMed2005

Laser surface registration for lateral skull base surgery.

OBJECTIVE: Logistics in the run-up to computer-assisted lateral skull base intervention can be reduced by markerless registration methods. So far, only the facial skin surface but not the skin surface that was near to the lateral skull base was used for markerless patient registration. The present study was designed to evaluate whether the auricles may serve as an accurate spatial reference for markerless patient registration in image-guided lateral skull base surgery. STUDY DESIGN: In a prospective clinical study, the precision of markerless patient registration was checked by using periauricular evaluation markers and additional distant oral evaluation markers that served as targets for the infrared pointer of a navigation system. Ten patients with cranial tumors, bony malformations, or foreign bodies who were planned for image-guided surgery were selected. Markerless patient registration was performed by laser-scanning with the SSN++ navigation system. RESULTS: Based on the auricle, a high accuracy (mean target detection error tde = 0.9 mm +/- s = 0.3 mm) was achieved in markerless patient registration as long as the auricle was not deformed during CT imaging or during laser scanning. However, the conventional CT acquisition with a head support caused temporary auricular deformations in half of the patients, which made a precise laser-scan registration impossible. CONCLUSIONS: Automated laser registration of the auricle reduces the logistical input in connection with computer-assisted lateral skull base surgery, ensuring the accuracy that has been achieved up to now with marker-based methods. Constantly good results can be achieved if the head support of the computer tomograph has an appropriate opening at the level of the auricles in order to avoid auricular deformations during CT acquisition.

Adult↗
PubMed2005

Robot-assisted craniotomy.

In the Special Research Centre 414 of the German Research Funding (DFG, Bonn) a system for robot-assisted cranial surgery was developed. It is designed for the accurate and safe execution of craniotomies and repositioning of bone pieces. The system is intended for use in the surgical therapy of craniosynostosis. Preoperatively, CT imaging is performed. In a computerized planning system the position and shape of the intended craniotomy is intuitively planned on a virtual model of the patient's skull. Intraoperatively, after conventional removal of the covering soft tissue, the robot performs the craniotomy autonomously. Extensive testing in phantom studies and animal tests confirmed the reliability and accuracy of the system. A thorough risk analysis of the system was performed. In this paper, the first clinical use of the system on a patient is described and the clinical importance is discussed.

Bone Cysts↗
PubMed2005

Geometric accuracy of the NewTom 9000 Cone Beam CT.

OBJECTIVES: To determine the geometric accuracy of digital volume tomograms to assess their usability for implant planning. METHODS: A measuring object with 216 measuring points, whose geometry is exactly known, is X-rayed with a NewTom 9000 cone beam scanner; thereafter the geometry of the volume tomogram of the object is compared with the original body. RESULTS: Considering all three coordinate axes, geometric mean deviations of 0.13 +/- 0.09 mm with a maximum deviation of 0.3 mm were determined. These geometric deviations are below the resolution power of the volume tomograph. CONCLUSION: The digital volume tomographies of NewTom 9000 present images which are geometrically correct and, from a geometrical point of view, suitable for three-dimensional implant planning.

Dental Implantation, Endosseous↗
PubMed2004

Automated laser registration in image-guided surgery: evaluation of the correlation between laser scan resolution and navigation accuracy.

Markerless patient registration based on the facial skin surface makes logistics prior to image-guided surgery much easier, as it is not necessary to place and measure registration markers. A laser scan registration of the surgical site takes the place of conventional marker-based registration. In a clinical study, the stability and accuracy of markerless patient registration was evaluated in 12 patients. Intraoral titanium markers served as targets for the infrared-pointer of the navigation system in order to check the accuracy of the markerless registration process. The correlation between laser scan resolution and navigation accuracy was checked using seven different laser scan resolutions (a cloud of 300,000 laser scan points down to 3750 laser scan points of the surgical site). The markerless patient registration was successful as long as high laser scan resolution was used (30,000 laser scan points and more): the titanium markers were detected with a mean deviation of 1.1 +/- 0.2 mm. Low resolution laser scans (6000 laser scan points of the surgical site and less) revealed inaccuracies up to 6 mm.

Humans↗
PubMed2004

Robots in the operating theatre--chances and challenges.

The use of surgical robots and manipulators is still being frequently discussed in the mass media as well as in the scientific community. Although it was already noted in 1985 that the first patient was treated by a joint team of robot and surgeon, today such systems are not routinely used. This can be explained by the high complexity of such systems and the often limited usability, but also, that it is difficult for surgeons to accept "automatic" machines. In this paper the possibilities and chances of robots and manipulators will be explained and it will be shown that robots will never work alone in the operating theatre as it is common in industry today. On the other hand, also limitations and challenges will be outlined. Therefore first a review on today's systems is given in different disciplines including oral- and cranio-maxillofacial surgery, then advantages and disadvantages are shown.

Equipment Design↗
PubMed2004

High-resolution laser surface scanning for patient registration in cranial computer-assisted surgery.

OBJECTIVE: Markerless patient registration is a new procedure that may reduce logistical efforts and possibly also the radiation load on the patients prior to a computer-assisted intervention. Congruent surfaces, such as bone surfaces or skin surfaces, represented in a data set and in the surgical site, can be overlapped using surface-matching. Previous studies describing this kind of markerless registration, however, show inaccuracies of up to 10 mm during computer-assisted navigation. Furthermore, these systems use less than 1000 surface points of the soft tissue surface in order to establish a correlation between the patient and the data set. Previous papers did not answer the question whether it is this scanning resolution that induces these inaccuracies in registration or rather intraoperative skin deformations. STUDY DESIGN: In the present study therefore a new navigation system (SSN++) was used which is able to register up to 180,000 surface points of the surgical site. SSN++ is an infrared navigation system enlarged by a Minolta VI 900 3D volume digitizer. Three different kinds of laser scan-resolution were used for data correlation. An additional congruence analysis was performed in order to assess the geometry of the matched skin surfaces. 22 patients suffering from different cranial diseases (tumors, bony malformations, foreign bodies) were prepared for a computer-assisted intervention. Intraoral titanium-markers, rigidly fixed on the patients by a maxillary splint, were placed as targets while the CT data sets were made. These targets were - after markerless laser scan registration of the patients - supposed to serve for validating the new high-resolution navigation system SSN++. RESULTS: The accuracy of markerless laser scan registration depends on the intraoperative laser scan's resolution. A high accuracy of the data correlation can be achieved if the number of the laser scan cloud points is about the same as the number of voxels of the corresponding surface on the CT data set. A reduction of the laser scan cloud points to less than 10 % compared to the number of voxels of the CT surface, however, leads to a significant loss of accuracy after markerless patient registration. CONCLUSION: The markerless laser scan registration of the surgical site may achieve the same accuracy as a patient registration made by rigidly fixed titanium screws (mean accuracy: 1.2 mm) as long as a high-resolution laser scan is being used.

Brain Diseases↗
PubMed2003

[New concepts in image assisted surgery: automated patient registration based on the jaw and external ear].

OBJECTIVE: Automatic and marker less patient registration based on natural anatomical interfaces may considerably reduce the radiation load and logistical input prior to computer-assisted surgical interventions, as it is not necessary to place and measure reference markers. The present study was to find out if, apart from the facial skin, also auricles as well as the upper and lower jaw can be used as anatomical interfaces for the intraoperative registration of the patient's position. MATERIAL AND METHOD: Prior to surgical intervention the positions of 20 patients were registered by a high-resolution 3D laser scan and correlated with the preoperative CT data set. Tumors, skeletal malformations, and foreign bodies were indications for surgical intervention. Auricles as well as the upper and lower jaw were used to register the patient's positions. The accuracy of this basically marker less method was clinically evaluated through the additionally placed conventional registration markers. RESULTS AND CONCLUSION: The marker less patient registration based on natural anatomical interfaces was successful in the upper jaw (deviation: 0.8+/-0.3 mm). The tongue and mobile floor of the mouth led to geometric incongruence and inadequate laser registration in the lower jaw. As far as the auricles were concerned, high accuracy could only be achieved as long as the auricles had not been deformed during CT imaging (deviation: 1.9+/-0.9 mm). The usual CT acquisition with a conventional head support, however, led to temporary auricular deformations in more than half of the patients, which made an exact laser scan registration impossible.

Artifacts↗
PubMed2000

[Traumatology. Mandibular fractures excluding condylar fractures].

Functionally stable fixation via bicortical osteosynthesis on the one hand, and monocortical non-compression osteosynthesis on the other, are still two competing concepts in treating mandibular fractures. A survey of the literature shows that complicated fractures with severe dislocation of the fragments have the lowest rate of complications after functionally stable fixation, whereas non-complicated fractures without significant dislocation in the distal part of the mandible can be treated successfully via monocortical non-compressive osteosynthesis as well. It seems that pre- and intraoperative parameters can be helpful in describing the character of a mandibular fracture in order to give a differential indication between the two therapeutical concepts. The consideration of only seven parameters, as the mandibular fracture score does, provides many combinations of describing a fracture, so that former studies with their small number of patients make only a rather inaccurate differential indication possible. As long as there is no prospective multi-center study giving a guideline to classify mandibular fractures, the rigid internal fixation via functionally stable osteosynthesis should be preferred in all cases which are not "clear, easy to handle" fractures.

Fracture Fixation, Internal↗
PubMed1999

[New possibilities of temporomandibular joint registration during orthodontic operations].

Repositioning osteotomies in a Le Fort I fashion can affect the position of the TMJ, which cannot be viewed directly during surgery. Using the computer-assisted navigation system SSN (Surgical Segment Navigator), the intraoperative position of the TMJ can be checked and unintentional malpositions can be detected. Positioning of the maxilla after Le Fort I osteotomy was carried out in a conventional fashion. Afterwards, the position of the maxilla was corrected in the same patients using the SSN. In this way, the precision of conventional and SSN-guided positioning of the maxilla and its effect on the TMJ has been compared.

Cephalometry↗
PubMed1999

Surgical planning of computer-assisted repositioning osteotomies.

Repositioning osteotomies are frequently used in orthopedic surgery and traumatology to correct malpositions. Computed tomography (CT), stereolithographic models, and x-rays are used in planning. However, the precision achieved in the planning phase is usually not translated to patients. The Surgical Segment Navigator (SSN) is a navigation system that allows computer-assisted correction of malpositions. It consists of an infrared positioning device, two dynamic reference frames (DRF), an infrared pointer, and an infrared camera. All data are displayed numerically and graphically on the monitor of the SSN workstation. The Laboratory Unit for Computer-Assisted Surgery (LUCAS) is used for planning surgery in the laboratory. LUCAS requires only a native CT scan. A preparatory operation to implant bone markers that will be visible in x-rays and a further planning CT scan showing the bone markers, which were necessary with previous systems, are not required for the LUCAS and SSN system. This significantly reduces the radiation exposure of the patient and the costs of surgical planning. Measuring anatomical landmarks in the surgical site, which is time-consuming and reduces accuracy, is not required with the SSN system because the position of the infrared transmitters is known during surgical planning on the LUCAS workstation. This makes the surgical approach faster and much more precise. The surgical planning data are transferred to the surgical site using a data file and an individual surface pattern that fits the surface of the navigated bone segment. The data file is exported from the LUCAS-workstation to the SSN workstation. The planned spatial displacement of the infrared transmitters is saved in this file. The individual surface pattern carries the infrared transmitters. This pattern is the mechanical interface between infrared transmitters and navigated bone segment. The individual surface pattern can be polymerized directly on a small stereolithographic model of the navigated bone segment. The surface pattern can also be generated as negative form from a CT data set using a computer-assisted design/manufacture system. In summary, LUCAS and SSN allow for the computer-assisted correction of malpositions and positioning of artificial joints and implants. In principle, the systems can be used in all fields of surgery.

Biomechanical Phenomena↗
PubMed1998

[Intraoperative precision of mechanical, electromagnetic, infrared and laser-guided navigation systems in computer-assisted surgery].

Intraoperative precision in computer-assisted surgery depends on the characteristics of a navigation system, the precision of correlation between object and data set, the position, number and fixation of landmarks, and the parameters of the data set. The characteristics of a navigation system, in particular the immanent precision, can be detected by the use of the geometric model and navigation analyzer developed at the University of Regensburg with the support of Carl Zeiss, Germany. The precision of five navigation systems of different types and technology was measured: Viewing Wand (ISG, mechanical system), the SMN microscope (Carl Zeiss, infrared system with laser autofocus), the MKM system (Carl Zeiss, robot platform with laser autofocus) and the STP pointer (Leibinger, infrared system). The immanent precision of these systems ranges from 0.1 to 2.0 mm. An electromagnetic system (3-Space Digitizer, Polhemus) was compared; this produces serious spherical deviations of 10.0 to 20.0 mm in the presence of metal, surgical and rotating instruments, and circuits. The application of these different systems for craniomaxillofacial surgery is discussed.

Computer Systems↗
PubMed1998

[Comparative accuracy assessment between a mechanical (viewing wand) and a laser-controlled microscopic positioning system using a geometric test model].

The precision of a new laser-guided navigation system (the "MKM") was compared with the "Viewing Wand" mechanical navigation system. We describe the inherent deviations in each positioning system as well as errors caused by data acquisition and referencing between the CT data set used for navigation and the original object. Two thousand individual measurements were performed on geometric test models scanned by CT. The technical accuracy of the mechanical navigation system varied between 0.48 mm in the most favorable area of the working field and 1.8 mm in the more inaccurate areas. For the laser-guided system a precision of 0.27 mm was found for all areas of the working field. After referencing between the CT data set and the original object, the error of measurement increased in both navigation systems: i.e., 0.83 mm for the Viewing Wand and 0.49 mm for the MKM system.

Equipment Design↗