Biomedical subjects

J Meixensberger

Publications and source records attributed to J Meixensberger.

At least 19 recordsLinked to original sources

PubMed2007

[Manipulator assisted endoscope guidance in functional endoscopic sinus surgery: proof of concept].

BACKGROUND: Functional endoscopic sinus surgery (FESS) is characterized by single-handed preparation and guidance of the endoscope by the nondominant hand. This results in an additional extension of operation time by up to 15% and ergonomic deficits. The aim of this study is the conception of an automated assistance system for FESS in view of the following questions: (1) Which degree of surgical automation is suitable for FESS? (2) Which design is suitable? (3) What are the properties of the technical system (planning, time, accuracy, precision) of the selected system? (4) Does the system offer potential for a clinical application? METHODS: In all 49 FESS were analyzed for surgical workflows. Measurement of the maximum forces within FESS was performed with 40 trials on an anatomical model. Three different mechanical systems were used in ten FESS and evaluated using the ICCAS Human-Machine Evaluation Scale. For realization of automated endoscope guidance an engine-driven and -braked manipulator (PA10-6c, Mitsubishi, Japan) was used. The technical parameters determined were expenditure of time for the preoperative planning of workspace, surgical accuracy and precision of the intraoperative endoscope positioning, maximal forces, and time. RESULTS: Concept-conditioned instrument changes amount to an average of 41.1 and 18.9% (5.21 min) time requirement for each FESS side. Maximum forces on the mucous membrane during a conventional FESS were measured at 9.8 N (5.9-9.8). Usability of the mechanical endoscope holder was estimated in 18 of 20 cases to be inferior to the standard procedure. The time needed for segmenting the intranasal workspace was 15.2 min (10.0-23.0). The maximum deviation of the automatically driven endoscope from a planned position amounted to 0.85 mm (manually 4.64 mm). The maximum force was measured with 1.1 N in the z direction (manually 9.8 N). Automated guidance of the endoscope to an intranasal position needed 7.25 s (6.4-7.9); manually 12.64 s (5.9-43.0). CONCLUSION: Guidance of the endoscope for FESS by an automated motor-driven system is possible. The conception which is based on workflow analysis favors a system with automatic definition of the workspace and a manual movement of the endoscope. The examined system offers a potential for clinical application. Definition of the automation level and development of a man-machine interface is more important than selection or reconstruction of a special manipulator for endoscope guidance in FESS from a surgical point of view.

Endoscopes↗

PubMed2006

[Improved accuracy and precision of the automated shaver (navigated control) in functional endoscopic sinus surgery].

BACKGROUND: The feasibility of a navigate-controlled Shaver for the paranasal sinus surgery was proven in an initial study. Deficits showed up in the conversion of the planed cavity. Goal of this study is (1) the development and evaluation of a FESS demonstrator for the investigations to the surgical accuracy and (2) the evaluation of the resulting surgical accuracy for registration and conversion of the work space with an improved rigidity of the Shaver and a completely revised study design. METHODS: As a demonstrator for the navigate-controlled resection of a volume through the Shaver a two-piece plastic head with an anatomical head and soft tissue model was designed. The investigation of the surgical accuracy takes place with 417 measurements to 4 different fiducial markers on the demonstrator head. The measurements for the deviation of the resulting cavity from the planned volume was realised with a work space by 24 x 24 x 30 mm. The 5 walls of the cavity were seized with 80 measuring points for each level and thus altogether 2000 measured values (5 models x 5 levels x 200 points). RESULTS: The described demonstrator showed itself suitable for the close-to-application attempts to the surgical accuracy. The maximum deviation A (max) indicated position of the Shaver from the reference value amounted to 1,93 mm. The maximum average value of the exceeding of a planned cavity amounts to 1,62 mm. CONCLUSIONS: Based on these results a virtual safety passage of 2.00 mm is sufficient. The study refers the clinical serviceability of the navigate-controlled Shaver in paranasal sinus surgery.

Equipment Design↗

PubMed2006

[Three-dimensional visualization of CT of the neck for surgical planning].

BACKGROUND: Surgical planning in ENT profits from computer assisted preoperative visualization and planning. The informative capability is to be improved by three-dimensional illustrating of the preoperative available data. The possibility of a 3-D-visualization of lymph nodes stands in the center of the interest. METHODS: 16 CT data sets with a tumor-classification of T1N1 or higher were included. Altogether 720 pseudo-3-D-illustrations were provided with an average of 9.3 objects. Current algorithms were used for the segmentation and visualization and the results were divided in three classes. RESULTS: The average time requirement for visualization and segmenting amounted to 122 minutes, the minimum value is at 61 minutes per data set. Automatic segmenting succeeded only with structures with clear grey tone differences to the environment. In all other cases an additional manual interaction had to take place. CONCLUSIONS: 3-D-Visualising of CT of the neck represents a new quality in preoperative planning. A clear trend at increasing detail loyalty and information efficiency showed up in the groups of B and C. It is possible to make from these pictures a quantitative statement on surgery relevant infiltration. Likewise conceivable are the postoperative quality control or planning and process control of a postoperative radio-chemotherapy. The automatic algorithms can be estimated as reliable. Application is still far from a clinically efficient use. With the rising efficiency of the computing systems, the improved software and the imaging systems the problems mentioned are, however, solvable.

Algorithms↗

PubMed2006

[Accuracy and precision in the evaluation of computer assisted surgical systems. A definition].

Accuracy represents the outstanding criterion for navigation systems. Surgeons have noticed a great discrepancy between the values from the literature and system specifications on one hand, and intraoperative accuracy on the other. A unitary understanding for the term accuracy does not exist in clinical practice. Furthermore, an incorrect equality for the terms precision and accuracy can be found in the literature. On top of this, clinical accuracy differs from mechanical (technical) accuracy. From a clinical point of view, we had to deal with remarkably many different terms all describing accuracy. This study has the goals of: 1. Defining "accuracy" and related terms, 2. Differentiating between "precision" and "accuracy", 3. Deriving the term "surgical accuracy", 4. Recommending use of the the term "surgical accuracy" for a navigation system. To a great extent, definitions were applied from the International Standardisation Organisation-ISO and the norm from the Deutsches Institut für Normung e.V.-DIN (the German Institute for Standardization). For defining surgical accuracy, the terms reference value, expectation, accuracy and precision are of major interest. Surgical accuracy should indicate the maximum values for the deviation between test results and the reference value (true value) A(max), and additionally indicate precision P(surg). As a basis for measurements, a standardized technical model was used. Coordinates of the model were acquired by CT. To determine statistically and reality relevant results for head surgery, 50 measurements with an accuracy of 50, 75, 100 and 150 mm from the centre of the registration geometry are adequate. In the future, we recommend labeling the system's overall performance with the following specifications: maximum accuracy deviation A(max), precision P and information on the measurement method. This could be displayed on a seal of quality.

Equipment Failure Analysis↗

PubMed2006

[Workflow analysis to assess the efficiency of intraoperative technology using the example of functional endoscopic sinus surgery].

Evaluation of the efficiency of surgical technology systems has to date been largely subjective. The aim of this study was to develop an ontology for surgical procedures usable workflow structures, and the evaluation of surgical workflow analysis using the example of functional endoscopic sinus surgery (FESS). A total of 38 procedures (20 patients) were included. Surgery was carried out by seven different surgeons with different degrees of training. Description of the surgical procedures and resources is based on the standard EN1828/2001 (Structure for Classification and Coding Systems for Surgical Procedures). In addition the requirements of the Workflow Reference Models (document no. Tc00-1003), Workflow Management Coalition (WfMC) were integrated. The workflow recorded the position, frequency of change of position, use time, cleaning time and concept based instrument changes. A total of 293 items were used to define FESS. A total of 1,029 different endoscopic positions were documented. These could be combined into five major endoscopic positions. The frequency of position changes was 27.1 per side, the period spent in an endoscopic position is about 1.31 min. Time for the concept-caused instrument changing was 6.44 min per side. This study demonstrates the need for assistance in guiding the endoscope in FESS. Using the workflow-data, the concept of an assistant system is possible. We offer a basis for discussion of the development of an ontology, recording and analysing surgical workflows and their practical application.

Biotechnology↗

PubMed2006

[Clinical efficiency and the influence of human factors on ear, nose, and throat navigation systems].

BACKGROUND: The aim of this study was to evaluate the Navibase navigation system for ear, nose, and throat (ENT) surgery. A new methodology for evaluating surgical and human factors is developed. PATIENTS AND METHODS: The evaluation is based on 102 ENT surgical applications, including 89 cases of functional endoscopic sinus surgery (FESS). The evaluation of surgical and human factors was performed by seven ENT surgeons. To evaluate surgical performance, level of quality (LOQ) in the 89 cases of FESS was determined, comparing the surgeon's own impressions with those of the navigation system on a scale from 0 to 100 and further comparing them with clinical results. Intraoperative changes in surgical strategy were documented. The human factors of total confidence (trust), situation awareness, skill set requirement and workload shift were recorded as level of reliance (LOR). RESULTS: The maximum deviation amounted to 1.93 mm. Averaging the quality of information resulted in an LOQ of 63.59. Every second application of the navigation system (47.9%) led to a change in surgical strategy. Total confidence showed a positive evaluation of 3.35 points in LOR. CONCLUSION: Application-relevant information relevant to the application beyond only technical details permits comparison with other assisting systems.

Attitude of Health Personnel↗

PubMed2006

Surgery of cavernous malformations with and without navigational support--a comparative study.

BACKGROUND: The aim of this descriptive study was the comparison of the clinical and surgical data of patients who suffered from cavernoma and were treated surgically with and without intraoperative navigation (ultrasound, neuronavigation). METHOD: Between 1995 and 2002, 40 patients were treated for cavernous malformations microsurgically: 24 patients (group I) using a neuronavigation system (STP 4.0, SNN, Germany), 7 patients (group II) using ultrasound (Siemens Omnia with 5.0 MHz Probe) and 9 patients (group III) without any image guidance using anatomic landmarks. FINDINGS: With the use of neuronavigation the mean sizes of cavernous malformations, which were resected, were reduced from 25.6 mm (group III) and 24.4 mm (group II) to 16.3 mm (group I) (p > or = 0.05). Corresponding to the reduction of the cavernoma size, the mean distances of the vascular lesion to the cortical surface increased from 13.9 mm (group III) and 17.8 mm (group II) to 24.4 mm under neuronavigational support (p > or = 0.05). All cavernomas were resected completely in all 40 patients. Postoperative neuroradiological control (MRI) confirmed complete resection in all cases. No significant differences in the clinical outcome could be evaluated in all three groups up to three months postoperatively. CONCLUSIONS: Use of neuronavigation was associated with a more comfortable and safer surgery of smaller and more deeper-seated cavernomas. In spite of the lack of significance between all groups, the advantages of neuronavigation in planning and realising surgery could be documented, which justify the additional costs and time-consuming acquisition of planning image data and postprocessing as well as intraoperative navigation.

Adolescent↗

PubMed2006

Application of intraoperative 3D ultrasound during navigated tumor resection.

Intraoperative 3D ultrasound (3D-iUS) may enhance the quality of neuronavigation by adding information about brain shift and tumor remnants. The aim of our study was to prove the concept of 3D ultrasound on the basis of technical and human effects. A 3D-ultrasound navigation system consisting of a standard personal computer containing a video grabber card in combination with an optical tracking system (NDI Polaris) and a standard ultrasound device (Siemens Omnia) with a 7.5 MHz probe was used. 3D-iUS datasets were acquired after craniotomy, at different subsequent times of the procedure and overlaid with preoperative MRI. All patients underwent early postoperative 3D MRI including contrast agent within 24 hours after surgery. Acquisition of 3D iUS and the fusion with preoperative MRI was successful in 22/23 patients. The expenditure of time was at least 5 minutes for one intraoperative 3D US dataset. The technique was used three to seven times during surgery. The quality of the ultrasound images was superior in cases of metastasis, meningeoma and angioma over those in malignant glioma. Brain shifting ranged from 2-25 mm depending on localization and kind of tumor. A resection control was possible in 78%. All six neurosurgeons demonstrated a learning curve. The introduction of 3D ultrasound has increased the value of neuronavigation substantially, making it possible to update several times during surgery and minimize the problem of brain shift. Configuration of both the 3D iUS based on a standard ultrasound system and the MR navigation system is time- and especially cost-effective. Faster navigational datasets and more intuitive image-guided surgery enable novel and user-friendly display techniques.

Adult↗

PubMed2006

Establishing navigated control in head surgery.

Navigated Control (NC) describes an additional control for a tracked power driven instrument within a preoperatively segmented work space. In head surgery the authors first implemented NC in functional endoscopic sinus surgery (FESS). Recently the feasibility of NC for surgery on the petrosal bone is evaluated. NC in FESS and in petrosal bone surgery may reduce the risk of comorbidity and the time effort compared to the conventional surgical interventions.

Endoscopy↗

PubMed2005

Brain tissue oxygen (PtiO2): a clinical comparison of two monitoring devices.

BACKGROUND: We investigated the difference between two commercially available sensors for continuous monitoring of brain tissue oxygen (PtiO2). One is a single parameter probe for PtiO2 monitoring (Licox), the other is a multiparamter sensor (Neurotrend) further including measurement of brain temperature, pH, and partial pressure of tissue carbon dioxide. METHODS: In seven patients after subarachnoid hemorrhage or traumatic brain injury continuous monitoring of PtiO2 was performed simultaneously using Licox and Neurotrend. FINDINGS: Mean PtiO2 was generally lower when assessed by the Neurotrend, as compared with the Licox (Licox 27.7 mmHg vs. Neurotrend 20.9 mmHg; P = 0.028). The amplitude of PtiO2 elevations during ventilation with 100% oxygen was higher with the Licox, but this did not reach statistical significance (Licox 55.2 mmHg vs. Neurotrend 50.2 mmHg, P = 0.082). Regarding clinical stability of the sensors, only one Neurotrend sensor provided valid function over the desired monitoring period. Five Neurotrend sensors dislocated or broke and one sensor did not show any function after insertion. No malfunction occurred with the Licox sensors. CONCLUSIONS: Our results suggest that PtiO2 might be lower when assessed by the Neurotrend sensor. The clinical stability of the Neurotrend sensor was of concern and allowed monitoring in one of seven patients over the desired monitoring period of several days only.

Brain Injuries↗

PubMed2005

Improvement of brain tissue oxygen and intracranial pressure during and after surgical decompression for diffuse brain oedema and space occupying infarction.

BACKGROUND: We evaluated the perioperative and intraoperative changes of intracranial pressure (ICP) and partial pressure of brain tissue oxygen (PtiO2) after decompressive craniectomy in patients with diffuse brain oedema and space occupying infarction. METHODS: Ten patients suffering from medically intractable raised intracranial pressure (ICP) were included. The underlying diseases and causes for elevated ICP were diffuse brain oedema after subarachnoid haemorrhage (n = 3) and head injury (n = 3), or space occupying infarction of the middle cerebral artery territory due to vasospasm after SAH (n = 4). Continuous perioperative and intraoperative monitoring of PtiO2 and ICP was performed at the side of decompression. FINDINGS: ICP and PtiO2 improved significantly in a uniform pattern during bone flap removal and dura opening, irrespective of the underlying disease (mean ICP from 52 mmHg to 8 mmHg, mean PtiO2 from 9 mmHg to 25 mmHg). ICP, PtiO2, and cerebral perfusion pressure were further improved in the subsequent 12 hours after surgery, as compared to the preoperative 12 hours. CONCLUSIONS: Decompressive craniectomy seems to be a successful option in the treatment of intractable intracranial hypertension with associated cerebral hypoxia. These positive effects may last for several hours after the procedure irrespective of the underlying disease.

Brain↗

PubMed2005

[Mechatronic in functional endoscopic sinus surgery. First experiences with the daVinci Telemanipulatory System].

BACKGROUND: This study examines the advantages and disadvantages of a commercial telemanipulator system (daVinci, Intuitive Surgical, USA) with computer-guided instruments in functional endoscopic sinus surgery (FESS). METHODS: We performed five different surgical FESS steps on 14 anatomical preparation and compared them with conventional FESS. A total of 140 procedures were examined taking into account the following parameters: degrees of freedom (DOF), duration , learning curve, force feedback, human-machine-interface. RESULTS: Telemanipulatory instruments have more DOF available then conventional instrumentation in FESS. The average time consumed by configuration of the telemanipulator is around 9+/-2 min. Missing force feedback is evaluated mainly as a disadvantage of the telemanipulator. Scaling was evaluated as helpful. The ergonomic concept seems to be better than the conventional solution. DISCUSSION: Computer guided instruments showed better results for the available DOF of the instruments. The human-machine-interface is more adaptable and variable then in conventional instrumentation. Motion scaling and indexing are characteristics of the telemanipulator concept which are helpful for FESS in our study.

Clinical Competence↗

PubMed2005

Correlation of continuously monitored regional cerebral blood flow and brain tissue oxygen.

BACKGROUND: The purpose of this study was to investigate the relationship between continuously monitored regional cerebral blood flow (CBF) and brain tissue oxygen (PtiO2). METHODS: Continuous advanced multimodal neuromonitoring including monitoring of PtiO2 (Licox, GMS) and CBF (QFlow, Hemedex) was performed in eight patients after severe subarachnoid haemorrhage (n=5) and traumatic brain injury (n=3) for an average of 9.6 days. Parameters were measured using a flexible polarographic PtiO2-probe and a thermal diffusion CBF-microprobe. FINDINGS: Regarding the whole monitoring period in all patients, the data indicated a significant correlation between CBF and PtiO2 (r=0.36). In 72% of 400 analysed intervals of 30 minutes duration with PtiO2 changes larger than 5 mmHg, a strong correlation between CBF and PtiO2 existed (r>0.6). In 19% of intervals a still statistically significant correlation was observed (0.3<r<0.6). During the remaining 9% no correlation was found (r<0.3). Regarding the clinical stability of the monitoring devices, the CBF monitoring system allowed monitoring of CBF in 64% of the time when PtiO2 monitoring was possible only. Phases of non-monitoring were mostly due to fever of the patient, when the system does not allow monitoring to avoid overheating of the cerebral tissue. CONCLUSIONS: This study suggests a correlation between CBF and PtiO2. The level of PtiO2 seems to be predominately determined by regional CBF, since changes in PtiO2 were correlated in 90% of episodes to simultaneous changes of CBF.

Brain↗

PubMed2005

Effect of 3T MRI on the function of shunt valves--evaluation of Paedi GAV, Dual Switch and proGAV.

The MR-compatibility of medical implants and devices becomes more and more important with the increasing number of high-field MR-scanners employed. Until the end of 2004, about twenty 3T MR in Germany will be in clinical practice. Patients with hydrocephalus need frequent follow-up MR-examinations to assure correct functioning of a shunt. We tested three types of gravitational valves: the Paedi GAV, the Dual Switch and as a new programmable valve the proGAV (Miethke Company, Berlin), that have not been evaluated at 3T, yet. In sum, there is strong evidence for maintenance of function of these valves after exposure to 3T. This also implies the programmable valve, as long as the brake mechanism is properly adjusted during MR-examination.

Cerebrospinal Fluid Shunts↗

PubMed2005

[Recommendations for the management of patients with aneurysmal subarachnoid hemorrhage].

After SAH, primary and secondary complications are frequent and often require neurosurgical interventions to avoid secondary brain damage. The authors of the present paper have summarized the available data about the treatment modalities often used for patients with SAH. The present recommendations have been developed as a neurosurgical and neuroanestesiological consensus. Evidence from prospective, randomized, double blind, placebo-controlled studies support grade A recommendations (standard) for the prophylaxis and treatment of cerebral vasospasm with oral Nimodipine in good grade patients. For intravenous Nimodipine or for oral nimodipine treatment in poor grade patients, available data only support grade C recommendations (options). Despite the lack of data supporting standards (grade A) or guidelines (grade B), avoidance and rigorous treatment of hypotension and hypovolemia remains the mainstay in the prophylaxis and treatment of a delayed ischemic neurological deficit (DIND). Prophylactic hypervolemia or prophylactic hypertension and hypervolemia was shown to be ineffective in reducing symptomatic vasospasm and improving outcome (grade B). Therapeutic hypertensive hypervolemic hemodilution is recommended as a treatment of symptomatic vasospasm but no prospective studies are available (grade C recommendation). Suggested target values for moderate triple-H-therapy are CPP 80- 120 mmHg (MAP 90-130), CVP > 7 mmHg and Hk 0.25-0.40. Balloon angioplasty should be considered for treatment of DIND cause by focal, proximal cerebral vasospasm. There is no evidence supporting the routine use of antifibrinolyticals, steroids or anticonvulsive prophylaxis. Clinical data indicate that current prophylaxis and treatment of cerebral vasospasm is still insufficient and aggressive triple-H-therapy is associated with an increased incidence of complications.

Angioplasty, Balloon↗

PubMed2005

[Virtual training in head- and neurosurgery].

BACKGROUND: Surgical skill requires training at close-to-reality scenarios. Conventional procedures (practical exercises, anatomical or animal cadavers) are increasingly in conflict with objective parameters (costs of OR, quality management, cadavers availability and cost). Surgical procedures can be covered by using Virtual Surgical Reality (VSR). METHODS: We examined the principle of a VSR system and evaluated the results with 30 probands by the example of modified radical mastoidectomy and ventriculocisternostomy. Probands were divided in experienced (A) and non-experienced surgeons (B). The protocol included time of surgery, collisions and fatal injuries at altogether 15 passages (10 passages - break of 14 days - 5 passages). Additionally the Medical Level of Trust (LOT) describes the confidence into the surgical scenario and thus the quality by volume illustration, texture and haptic data feedback to the user. We used a numeric scale between 0 and 100 and the starting point of 50. RESULTS: The learning effect can be confirmed for both virtual scenarios. The mastoid scenario reaches a total confidence index LOT of 75. The ventricle scenario is evaluated with a total confidence index of 84. The necessary time for the opening of the antrum is reduced from 15.0 minutes (group A) and 22.5 minutes (group B) around 37 % to 9, 5 (group A) and around 56 % to 10.0 minutes (group B). The virtual haptic result was evaluated positive in both scenarios. CONCLUSIONS: VSR systems have the potential to revolutionize surgical training. All surgical experienced probands evaluated the VSR-scenario as near-to-reality. "Suspension of Disbelief" is the major condition for effective virtual reality training systems.

Clinical Competence↗

PubMed2005

[Navigated control: a new concept in computer assisted ENT-surgery].

This work conceived and evaluates a mechatronical system for ORL-surgery by example of a Shaver for Functional Endoscopic Sinus Surgery controlled by navigation. The Shaver is automatically on/off-regulated depending on the current position in relation to the planned working space. This working space is defined on the basis of the individual CT data. Within this area the Shaver reacts to the signal of the surgeon (foot pedal). If the Shaver leaves the working space, an interruption of the drive regulation to the Shaver takes place. The evaluation of the planning software based on 32 patient CT-data sets. The registration accuracy in a anatomical model was examined on 451 measurements of endonasal attached titanium screws. The conversions of the working space were evaluated at 5 different technical models. The average time for segmenting the working space was found at 4.23 minutes per case. An average registration accuracy of the Shaver of 1.08 mm resulted. The pre-defined cavity was to be cleared away without restrictions. The preoperative determined work-space was converted by 3.1 mm over all levels. The study proves the feasibility of a mechatronical assistant system by the example of the navigate-controlled Shaver in paranasal sinus surgery. Contrary to conventional CAS solutions redundancy and cognitive discharge of the surgeon are considered in this conception. We see numerous applications according to the explained principle for power-control of instruments in ORL-surgery in the future such as drilling, high frequency surgery or laser.

Feasibility Studies↗

PubMed2005

The first evaluation of brain shift during functional neurosurgery by deformation field analysis.

Stereotactic surgery is based on a high degree of accuracy in defining and localising intracranial targets and placing surgical tools. Brain shift can influence its accuracy significantly. Deep brain stimulation of the subthalamic nucleus can markedly change the quality of life of patients with advanced Parkinson's disease, but the outcome depends on the quality of electrode placement. A patient is reported in whom the placement of the second electrode was not successful. Deformation field analysis of pre- and postoperative three dimensional magnetic resonance images showed an intraoperative brain movement of 2 mm in the region of the subthalamic nucleus (the target point). Electrode repositioning resulted in efficient stimulation effects. This case report shows the need to reduce risk factors for intraoperative brain movement and demonstrates the ability of deformation field analysis to quantify this complication.

Aged↗