Biomedical subjects

J Mühling

Publications and source records attributed to J Mühling.

At least 73 records · Page 4Linked to original sources

PubMed2000

A pattern catalogue of surgical interventions for computer-supported operation planning.

In this paper we present a new operation planning system which was evaluated in the clinic for Cranio-Maxillo-Facial-Surgery at the University of Heidelberg. In opposite to commercial systems our goal was, that the system considers the complete surgical intervention and not only a single procedure of it. A second goal was, that the system enables managing of complex operations, independent of which way the intervention will be intraoperatively performed (without technical support, with passive navigation support or active support by robots). Our system supports the surgeon during the preoperative planning as well as during the intraoperative execution phase. Therefore we developed a course model by which the managing of surgical interventions is possible. The focus of this paper is on this course model. At first we introduce instruction graphs and describe the structure of each activity observing its attributes and their context. Additionally, various surgical scopes will be presented which enable the surgeon to select one view among different ones of the individual operation procedures in accordance to medical and technical knowledge as well as in accordance to different degrees of abstraction. At last we demonstrate operation patterns, used as expert knowledge.

Computer Simulation↗

PubMed2000

Clinical evaluation of a highly accurate algorithm for CT bone contour segmentation.

Planning, visualisation and intraoperative navigation in a robot assisted environment for craniofacial surgery require highly accurate methods for the segmentation of bone structures in CT data. Clinical systems are still based on time consuming interactive methods like the seed-point segmentation. Faster methods with no need for interactivity lacks in precision. In the following we will present an automatic and highly accurate algorithm for the segmentation of bone contours in CT data. It is based on an algorithm for the automatic calculation of a grey-value tissue relation model for CT and MRI data.

Algorithms↗

PubMed2000

A real-time CORBA based system architecture for robot assisted craniofacial surgery.

We present the concept of a system architecture for the computer aided craniofacial surgery. The architecture is based on CORBA, an industrial standard specification for the development of distributed applications. Our concept includes a fundamental behaviour oriented communication model and some fundamental software safety considerations. We've developed a standard library for the integration of new services and devices into our system architecture. It decreases development time noticeably. We tested the performance and usability of our concept on an evaluation set up consisting of a surgery robot system, an infrared navigation system, a force-torque sensor and a visualisation software, obtaining excellent results. Future work will consist in the integration of further devices and the extension of our safety concept. An accurate clinical evaluation will take place continuously.

Computer Graphics↗

PubMed2000

Texture mapping based visualisation methods for the manipulation of CT data: interaction and ergonomics.

The manipulation of large CT datasets needs fast visualisation methods for a comfortable user interaction. Modern visualisation techniques make use texture hardware in graphics workstations extensively. In the following we will present an interactive tool for the positioning of anatomical landmarks in CT datasets of non-pathological children. The tool includes a fast visualisation of CT cross sections based on a texture mapping technique and an interactive three-dimensional view of the segmented CT dataset.

Cephalometry↗

PubMed2000

Comparative examination of the accuracy of a mechanical and an optical system in CT and MRT based instrument navigation.

The aim of an intraoperative instrument navigation system is to support the surgeon in the localization of anatomical regions and to guide the use of surgical instruments. An overview of technical principles and literature reports on various navigation systems is provided here. The navigation accuracy (tested on a plastic phantom under simulated operating room conditions) of the mechanical Viewing Wand system and the optical SPOCS system amounts to 1 to 3 mm for computerized tomography (CT) data, with a significant inverse dependence on the layer thickness. The values for magnetic resonance tomography (MRT) data are significantly higher. In regard to the choice of registration points, a statistically inverse dependence exists between the number of points and the distance between the points. During the time period between autumn 1993 and mid-1999, more than 120 clinical applications were performed. The intraoperative accuracy was in the range of < or = 3 mm. Registering the patient position with preoperatively inserted screw markers achieved accuracy values of < or = 2 mm. The instrument navigation technique has proved to be very advantageous for the spatial orientation of the surgeons. The possibility of checking resection borders has opened up new perspectives in tumor surgery. A quality improvement and a reduction of the operational risks as well as a considerable decline in the stress placed on the patient can be expected in the near future due the techniques of computer-assisted surgery.

Humans↗

PubMed1999

Quantitative determination of free intracellular amino acids in single human polymorphonuclear leucocytes. Recent developments in sample preparation and high-performance liquid chromatography.

The described procedure allows quantitative, highly precise and reproducible analysis of free amino acid concentrations in single polymorphonuclear leucocytes (PMLs). This method is superior to previously described procedures with regard to sample size, PML separation, sample preparation and stability, as well as the chosen fluorescence high-performance liquid chromatography procedure, and can satisfy the high demands for ultra-sensitive and comprehensive amino acid analysis, especially for the continuous surveillance of severe diseases and organ dysfunction.

Amino Acids↗

PubMed1999

Photodynamic therapy of primary nonmelanomatous skin tumours of the head and neck.

BACKGROUND AND OBJECTIVES: Nonmelanomatous skin tumours are the most frequent tumours in the white population and mainly caused by cumulative exposure to ultraviolet B radiation. On account of this origination about 80% of all nonmelanomatous skin tumours are located on the arms or the head and neck. Standard treatment for most tumours is surgical resection, with often only moderate cosmetic outcome. STUDY DESIGN/MATERIALS AND METHODS: In a prospective clinical trial the effect of photodynamic therapy on primary nonmelanomatous skin tumours of the head and neck (basal cell cancer, squamous cell cancer) was tested. In this study Foscan (meta-Tetrahydroxyphenylchlorin/mTHPC), a systemic photosensitizer of the second generation, was applied. Patients were injected 0.15 mg/kg or 0.10 mg/kg Foscan intravenously 96 hours prior to laser light exposure. Light was delivered via fibres by an argon-dye laser at 652 nm, 100 mW/cm(2) and a light dose of 5-20 J/cm(2). RESULTS: Eighteen patients with a total of 97 nonmelanomatous skin tumours and a mean follow up of 15 months (ranging 3-24 months) were treated. Within several days tumour necrosis appeared followed by wound healing within 4-8 weeks, leaving only minor scars behind. Ninety tumours (92.7%) showed a complete response with an excellent cosmetic outcome and only seven tumours responded by partial success due to low light dosage. The cosmetic outcome was very good and the therapy was supported by a high degree of patient satisfaction. CONCLUSION: By choosing the correct drug and light dosage, a selective tumour necrosis can be obtained. Photodynamic therapy (PDT) using Foscan seems to be a promising new and safe treatment modality for the treatment of primary nonmelanomatous skin tumours of the head and neck that can substitute surgical therapy, offering an even better cosmetic outcome.

Adult↗

PubMed1999

Cerebral blood flow velocity during isovolemic hemodilution and subsequent autologous blood retransfusion.

PURPOSE: To quantify the influence of hematocrit on cerebral blood flow velocity (CBFV) in healthy volunteers undergoing acute isovolemic hemodilution (HD) with hydroxyethyl starch 10% (HES) and subsequent autologous whole blood retransfusion (RT). METHODS: In 11 volunteers 20 ml x kg(-1) blood was withdrawn over 30 min and simultaneously replaced with HES 10%. Thirty min later, RT was started at a constant rate over 30 min. Recorded parameters included: CBFV pulsatility-index (PI) and resistance-index (RI) of the middle cerebral artery (MCA). Blood pressure (BP), heart rate (HR), hemoglobin (Hb), hematocrit (Hc) peripheral O2-saturation (SpO2), P(ET)CO2, arterial oxygen content (CaO2) and cerebral arterial O2-transport (C(E)-DO2= CaO2 x Vm-MCA) were monitored. RESULTS: An average of 1570 total blood was withdrawn which resulted in a decrease in Hb from 14.5 mg x dl(-1) to 10.3 mg x dl(-1); Hc (and CaO2) decreased from 41.8% (19.8 ml x dl(-1)) to 29.6% (14.2 ml x dl(-1); P < 0.01). Vm-MCA increased from 61.2 cm x sec(-1) to 77.3 cm x sec(-1) (P < 0.01). Following RT, Vm-MCA decreased again, but remained higher than baseline (P < 0.01). PI decreased by 13% following RT (P < 0.05). There were no changes in RI, HR, BP SpO2 and P(ET)CO2. Regression lines could be fitted between Hc and Vm-MCA, Vm-MCA and CaO2, and between Hc and C(E)DO2. CONCLUSIONS: Transcranial Doppler changes in blood flow velocities correlated with the simultaneously recorded systemic Hc and CaO2 values. We found a 2% increase in CBFV for each 1% decrease in Hc and CaO2.

Adult↗

PubMed1999

[Video-endoscopy of the major salivary glands].

Videoendoscopy is a minimally invasive procedure for the diagnosis and therapy of sialopathies of the major salivary glands. The main indication is sialolithiasis of the submandibular and parotid glands. Sialoendoscopy offers, on the one hand, a diagnostic method for radiolucent calculi in particular and, on the other, can be used to simultaneously remove calculi. Furthermore, endoscopy is of high value for the diagnosis and treatment of other salivary gland diseases in which there are pathological changes of the ductal system. For example, regeneration of the gland is now possible in cases of chronic sialadenitis, due to the removal of a sialostenosis. Sialadenectomy can thereby be avoided.

Endoscopy↗

PubMed1999

Effects of theophylline on human cerebral blood flow velocity during halothane and isoflurane anaesthesia.

The acute influence of therapeutic doses of theophylline on cerebral blood flow velocities during general anaesthesia induced either by halothane or isoflurane has not been elucidated previously. The aim of this study, was therefore to investigate these effects during steady state anaesthetic conditions in anaesthetized patients using transcranial Doppler sonography. Thirty-four Patients were investigated. Anaesthesia was maintained either with 1 MAC (minimum alveolar concentration) halothane (n = 16) or 1 MAC isoflurane (n = 18); FiO2: 40%; end-expiratory pCO2: normocapnia. Theophylline administration was performed before surgery by infusing 6 mg kg-1 over a period of 7.5 min. Measurements were recorded prior to theophylline administration, and immediately after 2 mg kg-1 (2.5 min), 4 mg kg-1 (5 min) and 6 mg kg-1 (7.5 min), as well as 5, 10, 15, 20, 30 and 45 min after theophylline administration. Recorded variables included blood pressure, heart rate, arterial oxygen saturation, end-expiratory pCO2, body temperatures, middle cerebral artery blood flow velocity and pulsatility index. Theophylline administration was well tolerated by all study subjects. Heart rate, blood pressure, body temperatures, arterial oxygen saturation and end-expiratory pCO2 remained constant during the whole examination period. Following theophylline, mean blood flow velocity decreased by 25% in the halothane and by 30% in the isoflurane group (P < 0.05). By the end of the examination period, mean blood flow velocity had not yet recovered to the initial values whereby in both groups the mean blood flow velocity was 26% below the initial values. In the isoflurane group, the pulsatility index increased by about 20% (P < 0.05) and remained high until the end of the examination. In the halothane group, however, there were no changes in the pulsatility index. Our results show a remarkable, significant and simultaneous decrease in blood flow velocity in the middle cerebral artery associated with theophylline administration during halothane and isoflurane anaesthesia in man.

Adult↗

PubMed1999

Plasma levels of selectins and interleukins in cardiovascular surgery using cardiopulmonary bypass.

BACKGROUND: Cardiovascular surgery with cardiopulmonary bypass (CPB) leads to activation of a variety of inflammatory pathways, including the release of cytokines and selectins. METHODS: In 20 patients undergoing elective coronary artery bypass grafting, plasma levels of interleukins IL-2, -6, -8, -10, -12 and of P-, E-, and L-selectins were measured at eight time points before, during, and after CPB using a standardized ELISA technique. RESULTS: IL-2 plasma levels decreased significantly after the start of CPB and remained low until the second postoperative day. IL-6 and IL-8 levels increased significantly after weaning off CPB, with mean peak values six hours postoperatively. Very low IL-10 plasma levels were detectable preoperatively. They remained low during CPB and peaked significantly after weaning off CPB until skin closure. The IL-12 levels decreased after weaning off CPB (p < 0.05) until 6 hours postoperatively. The plasma levels of P-selectin showed no alterations, but concentrations of E- and L-selectin decreased after the start of CPB (p < 0.05). There were no adverse postoperative events. CONCLUSIONS: The results of our study demonstrate a dysregulation of cytokine and selectin production during and up to 48 h after CPB, which may be a "normal" stress reaction to CPB.

Adult↗

PubMed1999

An argon-dye laser system for photodynamic therapy and diagnosis.

An argon-dye laser system for the clinical application of photodynamic therapy and photodynamic diagnosis is presented. Two out-patient treatment rooms and three operating theaters are served by an argon-dye laser system which can be accessed by remote-control from each treatment room. The argon-dye laser offers a wide range of light wavelengths with sufficient energy for all kinds of photosensitizers and fluorescent substances. This report presents our experiences with the first remote-controlled laser configuration which is being used routinely in clinical practice for photodynamic therapy and photodynamic diagnosis.

Ambulatory Care↗

PubMed1999

Development of an interactive multimedia-CBT-program for dental implantology and using tests of a program prototype.

The aim of the study was the development of a teaching program for dental implantology designed to improve student education as well as further training in this area. Initially, the computer equipment of German dentists was evaluated. Then, the contents of a teaching program "implantology interactive" were defined. A fully functional program prototype was developed in co-operation with a medical publishing house. Subsequently, the program was tested and statistically evaluated by 70 dental students and 40 dentists for the purpose of quality assurance. The program received extremely positive ratings with regard to design and functionality. Furthermore it was found to be clearly arranged and easy to comprehend. Even computer illiterate test persons had no problem working with the program. The biggest problem discovered during the test run was that 21% of the test persons lost their orientation while working with the program. The results of the study were used to optimize the program. For example, a graphic orientation tree was integrated, thereby improving the orientation within the program. The extremely positive reactions of the test persons leads us to expect that the introduced CBT-project will be successful. The use of the program in the student education in the dental clinic in Heidelberg and a publication in a medical publishing house are to be expected in the near future.

Attitude of Health Personnel↗

PubMed1999

Unrecognized renal damage in critically ill patients.

INTRODUCTION: The objective of this study was to evaluate the percentage of unrecognized renal damage in patients with normal creatinine and urea in serum and normal creatinine clearance and to evaluate the usefulness of various proteins and enzymes as supplementary procedures for the investigation of renal function. MATERIAL AND METHODS: Forty critically ill male patients (APACHE II-score > 20, injury severity score > 15) were daily screened for a period of five days. In the 1st group there were 30 patients with normal creatinine and urea in serum and with normal creatinine clearances. In the second group there were ten patients with increased values of these parameters. The base-line condition of all patients and any changes in hemodynamic, nutrition and ventilation were noted. Clearances of inulin, para-aminohippuric acid, and creatinine were measured and the Cockcroft-Gault equation was calculated daily for a period of five days. Excretion of alpha-1-microglobulin. Tamm-Horsfall-protein, alanine aminopeptidase, angiotensinase A, albumin and immunoglobulin G were also measured daily. RESULTS: 21 Patients of group 1 and all patients of group 2 showed the expected correlation between the routine parameters of creatinine and urea in serum and the level of protein and enzyme excretion. Nine patients of group 1 (30%) showed normal glomerular filtration rates but pathological excretion fractions of all proteins and enzymes. CONCLUSIONS: Although all routine parameters of renal function (creatinine and urea in serum, creatinine clearance both by 24-h collection period and from the Cockcroft-Gault equation), and additionally inulin and para-aminohippuric acid clearance were measured, no references on tubular and glomerular damage were found in 30% of the investigated patients.

Acute Kidney Injury↗

PubMed1998

Navigation in maxillofacial and craniofacial surgery.

The standardized operational techniques available today make it possible to perform extensive surgeries for the treatment of craniofacial malformations and advanced tumors in this anatomically complex region. The new techniques of computer-assisted surgery allow us to interactively use the three-dimensional image data of the patient during surgery. Simulation of complex osteotomies in individual patients is now possible with the aid of new software developments for virtual cutting and shifting of bone segments. Intraoperative realization with navigation systems has been performed at our clinic for the past 4 years, and we have gained extensive experience from more than 100 clinical applications of mechanical and optoelectronic navigation systems. These passive localization systems supply the surgeon with direct intraoperative support while performing the surgeries. It is the primary goal of computer-assisted surgery to support the surgeon during diagnosis, operational planning, and intraoperative navigation. We can thereby achieve a reduction in operational risk and duration, which in turn results in a considerable stress reduction for the patient.

Craniofacial Abnormalities↗

PubMed1998

Possibilities and developments of intraoperative image-guided surgery in craniofacial surgery.

The standardised operational techniques of fronto-orbital osteotomy and the various modifications used today make it possible to perform extensive surgery for the treatment of craniofacial malformations and advanced tumours in this region, while also allowing for a good extra- and intracranial view. Osteotomies and resections in areas of the skull base that are normally hard to reach have been considerably facilitated and the operational risk has been lowered. Our aim is to achieve a further reduction of the operational risks and of the post-surgical morbidity rate through the use of techniques of computer-assisted surgery. Especially in the area of the complex anatomy of the skull base, use of the systems for the purpose of orientation and realisation of operational planning as well as for the control of how radical a tumour resection needs to be, have proved quite successful. Meanwhile, we have acquired experience in more than 100 clinical applications of mechanical and optoelectronical navigation systems. However, it is not possible to make changes to the presurgical data. Also, the flexibility of the system is still somewhat limited. By introducing a new referencing system, the flexibility and possible applications of navigation have been increased. The current possibilities and indications for the use of intraoperative navigation are discussed.

Computer Simulation↗

PubMed1998

[Modifications of fronto-orbital osteotomy as an approach to the anterior and middle skull base].

Various extracranial, intracranial and combined extra-intracranial approaches have been described for the surgical therapy of tumours of the anterior and medial cranial base. A combined extra-intracranial approach is indicated in cases in which the cranial base tumour spreads out intracranially and at the same time into the main nasal cavity, the paranasal space and/or the orbits. These tumours of the skull base can be surgically removed by two standardised modifications of the fronto-orbital osteotomy--the fronto-orbito-nasal and the fronto-orbito-zygomatic osteotomy. The advantage of these surgical techniques in comparison with other methods is that they permit a good extracranial and intracranial view with only minimal brain trauma. Generally, additional transfacial incisions are unnecessary. The operative techniques are described and the results of 108 cases of tumours of the skull base shown.

Craniotomy↗

PubMed1998

[Long-term outcome after corrective surgery of the neuro- and viscerocranium of patients with simple and syndrome-related premature craniosynostosis].

A retrospective and partly prospective study was conducted to analyse both clinically and cephalometrically the craniofacial growth pattern of patients with isolated and syndrome-related premature craniosynostosis after standardized fronto-orbital and midface advancement. The file data of 293 children with fronto-orbital advancement were evaluated over an average period of 4.4 years. In addition, lateral teleradiographies of 117 patients from this group were cephalometrically analysed. Moreover, late results of 36 children and 8 adults with midface-advancement with an average follow-up period of 4.5 years were assessed. In contrast to linear craniectomy and so-called lateral canthal advancement, in only 8.2% of cases (24 out of 293 patients) were relapses requiring reoperation found in this study after fronto-orbital advancement. The evaluations indicate that with simple forms of craniosynostosis such as trigonocephaly and plagiocephaly predominantly very good or good growth can be observed. Cephalometric evaluation confirmed the limited potential of growth in the area of the anterior skull base and in the midface in the presence of syndrome-related faciocraniosynostoses. In such cases the cephalometrically confirmed maxillary hypoplasia, which increases in severity in the following order of syndromes 'Saethre-Chotzen-Crouzon-Apert-Pfeiffer', could be influenced only to a limited degree by fronto-orbital advancement. For this reason midface advancement is of secondary importance in children with very severe anomalies. In the present evaluation, a high rate of relapse of midfacial hypoplasia was to be found in children and adolescents after this operation in accordance with other references. Therefore, the indication for Le Fort III osteotomy in the growth period should be limited.

Adult↗