Robot- and computer-assisted craniotomy (CRANIO): from active systems to synergistic man-machine interaction.

Computer and robot assistance in craniotomy/craniectomy procedures is intended to increase precision and efficiency of the removal of calvarial tumours, enabling the preoperative design and manufacturing of the corresponding implant. In the framework of the CRANIO project, an active robotic system was developed to automate the milling processes based on a predefined resection planning. This approach allows for a very efficient milling process, but lacks feedback of the intra-operative process to the surgeon. To better integrate the surgeon into the process, a new teleoperated synergistic architecture was designed. This enables the surgeon to realize changes during the procedure and use their human cognitive capabilities. The preoperative planning information is used as guidance for the user interacting with the system through a master-slave architecture. In this article, the CRANIO system is presented together with this new synergistic approach. Experiments have been performed to evaluate the accuracy of the system in active and synergistic modes for the bone milling procedure. The laboratory studies showed the general feasibility of the new concept for the selected medical procedure and determined the accuracy of the system. Although the integration of the surgeon partially reduces the efficiency of the milling process compared with a purely active (automatic) milling, it provides more feedback and flexibility to the user during the intra-operative procedure.

Identification of milling parameters for manual cutting of bicortical bone structures.

Within the framework of the development of a new neurosurgical robot system, parameters of conventional manual neurosurgical bone milling had to be determined. These results were used as a reference for the design and validation of the robotic versus manual milling task. Bovine scapulae were used for the tests because their bicortical structure is similar to the bone structure of the skull. The exercise was to cut defined geometries that had been registered on the bone prior to the start of the milling operation. The geometries had to be milled with a depth of 3 mm, which corresponded to the radius of the ball of the cutter. Different parameters like tool position, rotary speed, temperature, forces and time were registered. Eleven experienced neurosurgeons with practical experience of 80-1200 skull operations participated in this study. First results show a large variation in depth along the line. The lateral deviation was up to 5 mm, the depth error up to 2.5 mm, the tool temperature was 22 degrees C to 65 degrees C, and rotary speed varied from 15,000 to 80,000 rpm. Registered forces had maxima of 16 N in the feed direction and 21 N normal to the surface; average forces were approximately 1-2 N.

[CRANIO--development of a system for computer- and robot-assisted craniotomy]. / CRANIO--Entwicklung eines Systems zur Computer- und roboterunterstützten Kraniotomie.

In the framework of the DFG project CRANIO, we are dealing with the problems of computer-assisted planning and robot-assisted realization of craniotomy, with optional skull reconstruction. A CT dataset was obtained from a phantom skull model and basic operation planning as well as different registration methods were performed. As one option it is possible to mill a contour on the skull or even to remove the entire area with a robot-guided microsurgical milling tool. In this context, work space tests were performed with a hexapod parallel robot. The milling of any contour geometry could be realized with different tool angles using the existing CRIGOS robot system without additional axes.

[Minaro--new approaches for minimally invasive roentgen image based hip prosthesis revision]. / Minaro--neue Ansätze für die minimalinvasive röntgen-bildbasierte Revisionshüftendoprothetik.

The main objective of the MINARO project (Minimal Invasive NAvigation and RObotics) is the development of a modular intraoperative planning system for fluoroscopy based total hip revision surgery. Especially the distal cement removal can be a challenging problem. To avoid exhaustive x-ray imaging a navigation system should be used, nevertheless, the three-dimensional shape of the bone cement remains unclear. Our approach in the MINARO-project is to reconstruct the real shape of the bone cement by using just a few x-ray projections. First results show, that the reconstruction has an RMS-Error smaller than 0.5 mm using 6 x-ray projections.

Robot- and computer-assisted craniotomy: resection planning, implant modelling and robot safety.

BACKGROUND: In cases of cranial tumour, manual resection of the cancerous tissue can be very stressful and time-consuming, due to the adhesion of the subjacent dura mater. Computer-assisted planning, navigation and robotic craniotomy, with optional skull reconstruction using customized implants, are of increasing clinical interest in craniofacial and neurosurgery. METHODS: Using preoperative computed tomography (CT) images, an automatic segmentation of the tumour is performed, followed by resection planning. The skull reconstruction is performed using computer-assisted implant modeling and manufacturing. Risk analysis of the robot-guided intervention led to the development of a new hexapod robot system. RESULTS: Results from registration and robot accuracy on plastic and Anatomical skull are shown. The concept of a stand-alone safety system is presented to supervise the robot during the intervention. The entire process from preoperative CT scan to intraoperative robot assisted removal of tumourous bone is shown in laboratory and anatomical trials. CONCLUSION: The laboratory and anatomy studies conducted so far provided a substantial basis for further improvement of the system's integration in the surgical workflow and the final approval of the system for initial clinical studies.

Analysis of surgical management of calvarial tumours and first results of a newly designed robotic trepanation system.

This study was performed to evaluate the surgical strategy in patients with calvarial tumours, in order to design and modify a robot-assisted trepanation system. A total of 75 patients underwent craniectomy for the treatment of calvarial tumours during the 10-year period from 1993 to 2002. The patients' complaints, the size, location and histology of the tumour, and the various cranioplasty techniques used were analysed retrospectively. In a second procedure several craniectomies at typical locations according to the study's results were performed in a laboratory setting using a hexapod robotic tool, constructed at the Helmholtz-Institute, RWTH Aachen University, and plastic model heads. The workflow was documented and the reproducibility and the accuracy of the procedure were registered. A total of 83 surgical procedures were performed on 75 patients. The majority (87 %) of lesions treated surgically were located in the frontal, temporal and anterior parts of the parietal region. Histological examination revealed benign lesions in 66 % of the patients and dural involvement in 46 %. According to these results craniectomies were performed using the robotic system. Mean positioning accuracy of the robotic system while milling was 0.24 mm, with a standard deviation of 0.04 mm, and maximum error under 1 mm. Craniectomies leaving a 1-mm layer of the tabula interna intact to ensure a healthy dura were performed in several regions successfully. The majority of calvarial tumours, requiring surgical treatment in our patients, were located in cosmetically relevant areas in which drilling can be carried out with the robotic trepanation system. Consequently, the surgical approach had to be planned carefully in order to achieve a good cosmetic outcome.

Cellular energetics in the preconditioned state: protective role for phosphotransfer reactions captured by 18O-assisted 31P NMR.

Cell survival is critically dependent on the preservation of cellular bioenergetics. However, the metabolic mechanisms that confer resistance to injury are poorly understood. Phosphotransfer reactions integrate ATP-consuming with ATP-producing processes and could thereby contribute to the generation of a protective phenotype. Here, we used ischemic preconditioning to induce a stress-tolerant state and (18)O-assisted (31)P nuclear magnetic resonance spectroscopy to capture intracellular phosphotransfer dynamics. Preconditioning of isolated perfused hearts triggered a redistribution in phosphotransfer flux with significant increase in creatine kinase and glycolytic rates. High energy phosphoryl fluxes through creatine kinase, adenylate kinase, and glycolysis in preconditioned hearts correlated tightly with post-ischemic functional recovery. This was associated with enhanced metabolite exchange between subcellular compartments, manifested by augmented transfer of inorganic phosphate from cellular ATPases to mitochondrial ATP synthase. Preconditioning-induced energetic remodeling protected cellular ATP synthesis and ATP consumption, improving contractile performance following ischemia-reperfusion insult. Thus, the plasticity of phosphotransfer networks contributes to the effective functioning of the cellular energetic system, providing a mechanism for increased tolerance toward injury.

Site-specific mutagenesis of Escherichia coli asparaginase II. None of the three histidine residues is required for catalysis.

Site-specific mutagenesis was used to replace the three histidine residues of Escherichia coli asparaginase II (EcA2) with other amino acids. The following enzyme variants were studied: [H87A]EcA2, [H87L]EcA2, [H87K]EcA2, [H183L]EcA2 and [H197L]EcA2. None of the mutations substantially affected the Km for L-aspartic acid beta-hydroxamate or impaired aspartate binding. The relative activities towards L-Asn, L-Gln, and l-aspartic acid beta-hydroxamate were reduced to the same extent, with residual activities exceeding 10% of the wild-type values. These data do not support a number of previous reports suggesting that histidine residues are essential for catalysis. Spectroscopic characterization of the modified enzymes allowed the unequivocal assignment of the histidine resonances in 1H-NMR spectra of asparaginase II. A histidine signal previously shown to disappear upon aspartate binding is due to His183, not to the highly conserved His87. The fact that [H183L]EcA2 has normal activity but greatly reduced stability in the presence of urea suggests that His183 is important for the stabilization of the native asparaginase tetramer. 1H-NMR and fluorescence spectroscopy indicate that His87 is located in the interior of the protein, possibly adjacent to the active site.