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Biomedical subjects

R Leuwer

Publications and source records attributed to R Leuwer.

At least 37 records · Page 2Linked to original sources
PubMed2001

[Topographic diagnosis in the area of the head-neck: initial experiences comparing ultrasound panorama images with CT and MRI].

PURPOSE: Due to the restricted width of the ultrasound array, documentation of topographical correlations in B-scan-echography is still difficult. By means of Color SieScape it is possible to produce successive images of the regions of interest by lateral movement of the ultrasound array. Aim of the present study was to evaluate this new method in comparison to CT and MRI. METHOD: 18 patients with tumors in different areas of the head and neck region were examined by CT or MRI and by sonography. Color SieScape was used for documentation. A Sonoline Elegra ultrasound platform with 7.5 MHz linear array was used for the investigations. RESULTS: Because of claustrophoby no MRI-investigation could be done in 4 of the patients. Sonography and Color SieScape documentation was possible in all cases. In addition to the panorama-information of SieScape technique in every investigation by Color SieScape large and very small vessels could be documented in colour. CONCLUSION: By the use of Color SieScape the identification of the topographical correlations is improved. The spatial resolution is comparable to MRI and better than in CT. Investigation of patients who suffer from claustrophobia is much easier by Color SieScape. The imaging of parapharyngical structures could not be improved by Color SieScape. Nevertheless it is the only technique for the coloured documentation of even small vessels and topographic relations. Color SieScape investigations are faster and less expensive than CT or MRI.

Humans↗
PubMed2001

[Clinical relevance of developmental changes of the endolymphatic sac].

BACKGROUND: Outcome of endolymphatic sac shunt surgery crucially depends on endolymphatic sac morphology. The intraoperative finding of a fibrotic sac, e.g., will lead to therapy-failure. Aim of the present study was to determine possible developmental changes in endolymphatic sac morphology which could imply, that a shunt operation should not be undertaken in older age. METHOD: 46 histological temporal bone serial sections were examined. All sections were taken from the "Wittmaack Temporal Bone Collection". All specimens were obtained from patients with morphologically healthy ears, especially without a history of Menière's disease or other kinds of vertigo. RESULTS: During the fetal period the endolymphatic sac is a wide cavity that is surrounded by immature embryonal connective tissue. In older age this cavity gradually shrinks, leading to stenosis in about 80% of the cases. The endolymphatic duct, however, remains open. CONCLUSION: The increasing fibrosis of the endolymphatic sac is part of the natural involution of the inner ear. It constitutes a natural limitation for the outcome of endolymphatic sac shunt surgery in the elderly.

Adolescent↗
PubMed2001

[Use and results of universal newborn hearing screening with ALGO portable device].

BACKGROUND: Congenital hearing disorder, which has an occurrence of 1 in 1000 newborn babies, is a health problem that should be taken seriously. Once it has been discovered too late, it leads to lifelong language, intellectual, emotional and social problems. The aim of this project was the critical evaluation of a universal, ABR-based newborn hearing screening, looking at the specificity and the success of the method used as well as the organisational requirements and costs involved with this method. METHODS: From August 1999 until March 2000, 464 newborn babies, born at the University Hospital Eppendorf in Hamburg, were examined with the Algo portable. Another 31 children, all younger than 6 months, were also examined with the Algo portable, because of suspected hearing loss. When a child got a refer twice by the Algo portable, the child was examined again, using the conventional ERA-machine (Evoselect) to confirm the suspected hearing loss and to assess its grade. RESULTS: 98% of the newborns at our hospital were examined. Up to now, out of 13 conspicuous children, the majority of which belonged to the risk group, 6 have been identified as unambiguously bilateral and 2 as unilateral hard of hearing. After an introductory period of two months, the average costs per examination could be set at 38.65 DM and app. 3200 DM per bilateral hearing loss discovered. CONCLUSION: A Universal Newborn Hearing Screening is necessary and can be executed with calculable effort with concern to personnel, time and finance.

Age Factors↗
PubMed2000

[Anatomy of the valve system of the internal jugular vein].

BACKGROUND: Central venous catheters (CVC) in the internal jugular vein have become an important adjunct to the overall management of intensive care patients, but their use is associated with frequent neck complications. In a review of the literature anatomical variation in size, form and function of the valve system of the internal vein was found. PURPOSE: This study macroscopically and microscopically investigates the anatomical variety of the vein valves of the inferior internal jugular vein. MATERIAL AND METHODS: 100 cadavers from legal autopsies were investigated. We selected 45 patients with an acute myocardial infarction death and a control group (55 patients) formed by different causes of death. The veins were prepared for light microscopic study, the specimens were serially sectioned (ca. 30 sections) and stained with hematoxylin and eosin. RESULTS: Anatomical variety was observed predominantly unilateral on the right side of the internal jugular vein. The valves were often bicuspid at the right side (92%) and tricuspid on the left side (64%) and mostly located ca. 2 cm above the subclavia-jugularis bifurcation. In the histological study, a variability of the net of collagen and elastin fibres in the tunica intima and media was observed. The structure of the adventitia was constant. 18 patients with a jugular valve vein incompetence (age over 60) appeared to have thickening of the tuberculum in the sinus of the valve. The cups of the valves were found rudimentary in these patients with advanced stages of tricuspid incompetence. CONCLUSION: The present study demonstrates the variety of the valves of the jugular vein. They play an important role to impede the retrograde flow during cardiopulmonary resuscitation as well as in jugular vein cannulation.

Adolescent↗
PubMed2000

Planning and rehearsal of surgical interventions in the volume model.

Visualization of 3D medical data is routinely used in a wide range of applications. However, for the planning and rehearsal of surgical interventions more sophisticated techniques for interaction have to be developed. The realistic specification and visualization of free form cuts is needed to allow the 'look and feel' close to a real dissection. The problem here is, since these cuts are not represented by intensity changes, that the gray-level-gradient-method can not be used for the estimation of surface normals. In addition, the interactive repositioning of dissected fragments has to be simulated. We have developed an extended ray-casting algorithm for visualization of object motion in the volume model. We implemented new methods for the representation, modeling and high quality rendering (subvoxel resolution) of arbitrarily shaped cut regions within the volume model. The representation is done using a dynamic data structure. This way, all operations can easily be reversed and the original object information is preserved. The modeling of cut surfaces is done in an independent data volume where the partial-volume-effect, which is the prerequisite for the gray-level-gradient method, is calculated as it would be generated by an imaging system. This way, the localization of cut surfaces at subvoxel resolution and an accurate estimation of the surface normals is achieved. The key point here is to detect if a cut surface really truncates an object or if the object has not been affected by a cutting operation. We will present an new method, called adaptive sampling which allows to determine the situation by the generation of additional sample points (when necessary) during the ray casting process. The described techniques provides the basis for simulation of surgical interventions in the voxel-model which could not be achieved with any surface-based method. We present a system for simulation and rehearsal of otosurgical approaches, where we implemented a drill-like tool with which the student lays off the route to the operating area. The key point is to not injure structures of risk such as the facial nerve. For applications like the simulation of craniofacial surgery we developed a gradual cutting tool ("virtual scalpel").

Computer Graphics↗
PubMed1999

[A new aspect on the development of chronic middle ear diseases in patients with cleft palate].

BACKGROUND: The prevalence of chronic middle ear disease in patients after surgery for cleft palate is about 50%. Aim of the present study was to analyse its morphological and physiological causes to prevent chronic atelectatic otitis media or cholesteatoma. METHODS: 15 adult patients with cleft palate were examined using middle ear microscopy, pure tone audiometry, EMG of the tensor veli palatini muscle and MRI of the Eustachian tube. RESULTS: 8 of 15 patients had chronic middle ear disease. With 13 of 15 patients single motor unit action potentials could be recorded from the tensor veli palatini muscle. MRI of the Eustachian tube revealed two decisive observations in patients with chronic middle ear disease: in 4 patients the pterygoid hamulus could not be detected, in all otitis patients the continuity of tensor veli palatini muscle was interrupted or disturbed by medial or lateral fixation. CONCLUSION: Chronic middle ear disease with cleft palate patients is basically caused by impaired muscular compliance of the Eustachian tube. Thus integrity of hamulus as well as tensor veli palatini muscle must become of crucial interest in cleft palate surgery.

Adolescent↗
PubMed1999

[Muscular compliance of the auditory tube].

BACKGROUND: The simultaneous electromyographical assessment of innervation patterns of the mylohyoid and the tensor veli palatini muscle is introduced as a new technique for the examination of the auditory tube function. PATIENTS AND METHODS: Clinical studies were performed on 30 healthy volunteers and 50 patients suffering from chronic tubotympanic mucositis and cholesteatoma. Concentric needle electrodes were advanced into the tensor veli palatini muscle through the palate. The mylohyoid muscle was examined using surface electrodes. RESULTS: Innervation patterns of the tensor veli palatini muscle in volunteers were limited to the time interval of the mylohyoid innervation pattern only, i.e., the oral and pharyngeal phases of swallowing. In 14 of the chronic otitis patients these tensor muscle innervation patterns were found outside this interval. CONCLUSION: This observation provides a new pathophysiological explanation for the clinical concept of a relative closing failure of the auditory tube. These results emphasize the significance of coordination in muscular compliance of the tube.

Adolescent↗
PubMed1999

[Removal of a cochlea implant with chronic granulation labyrinthitis and foreign body reaction].

BACKGROUND: Cochlea Implantation is an accepted treatment for children and adults with profound sensorineural deafness. In rare cases postoperative complications may occur so that removal of the implant is unavoidable. CASE REPORT: In a particular case we present and discuss the case of a 69-year-old patient. CONCLUSION: After removal of a cochlear implant, the electronic array is frequently left in the cochlea as a temporary replacement. This is a common practice, but whether it is advisable should be verified according to the specific intraoperative situation.

Aged↗
PubMed1999

[Evidence-based medicine--a critical overview].

BACKGROUND: Evidence-based medicine (EBM) is a strategy for the standardization of medical decision-making. The purpose of this review was to demonstrate the most important tools of EBM and to critically appraise them. METHODS: The current literature concerning the subject is reviewed. A clinical example for the systematic use of EBM in diagnostic tests is explained in detail. RESULTS: The risk of an increasing bureaucratic hindrance of medical procedures by EBM is weighed against the advantages of a systematic strategy for the valid assessment of medical information. According to the clinical example EBM proves to be a valuable tool in the quantitative estimation of residual risk and reliability of diagnostic tests in everyday clinical practice. CONCLUSION: The critical use of the systematic tools of EBM for clinical decision-making is recommended.

Decision Support Techniques↗
PubMed1998

[Value of duplex ultrasound in diagnosis of parotid tumors].

BACKGROUND: The sensitivity of diagnostic imaging of processes in the parotid gland has been increased by improved spatial resolution, yet specificity remains unchanged. The purpose of this study was to determine whether the low-flow color duplex technique alters the specificity of B-mode ultrasonography. PATIENTS AND METHODS: Forty-one patients with tumors of the parotid gland were examined by color duplex echography as well as histologically. Twenty-eight of the 41 patients had benign tumors and 13 had malignant disease. In 17 of 41 patients, color duplex ultrasonography failed to detect any vascularization within the tumor. Histopathological examination showed that 3 of these 17 tumors were malignant and 14 of 17 were benign. Intranodal vascularization was detected in 24 cases. Ten of these patients were found to have malignant tumors of the parotid gland; 14 had benign parotid tumors. RESULTS: Our present findings show that marked intratumoral vascularization especially appears in malignant tumors. In contrast to lymph nodes, the location and texture of intranodal blood vessels do not provide information about the nature of the neoplasm. CONCLUSIONS: Low flow duplex ultrasonography does not increase the specificity of preoperative examination in tumors of the parotid gland.

Diagnosis, Differential↗
PubMed1998

[Complications with permanent damage in endonasal paranasal sinus operations--more frequent in experienced surgeons?].

BACKGROUND: The rate of serious complications in endonasal sinus surgery has not gone down although optical aids are widely used nowadays. Are serious complications caused more often by unexperienced or experienced surgeons using a microscope and/or endoscope? METHODS: We defined serious complications as follows: death, persistent neurological deficits or permanent loss of vision, and injury to the internal carotid artery. Two different studies were made: the first consecutive 300 interventions of 6 sinus surgeons were evaluated. Sixteen malpractice cases were analysed regarding the experience of the surgeon. RESULTS: In 9 out of 16 malpractice cases serious complications were attributable to experienced surgeons, five to moderately experienced surgeons, and only two to an inexperienced surgeon (although he had extensive experience in external sinus surgery). There were 6 deaths, 6 neurologic defects, 2 visual disorders, and 2 injuries to the internal carotid artery without any sequelae. In 9 cases the serious complications were related to injury of the internal carotid artery, in five cases to perforation of the skull base. Twice the orbital wall was penetrated. In 1800 procedures performed by 6 surgeons, no serious complications were encountered. There were only lesions of the periorbit (n = 33) or CSF leaks (n = 8) without any permanent damage to the patient. CONCLUSIONS: Even an experienced surgeon must always keep in mind that serious complications can occur in sinus surgery. One must constantly be alert to the possibility of anatomical variants or specific pathologic findings.

Cause of Death↗
PubMed1997

[Microlight-guided spectrophotometry of the cochlea].

BACKGROUND: Intraoperative measurements of local intracapillary hemoglobin oxygenation of the human cochlea via the round window membrane have been shown to be possible using the Erlangen microlight-guided spectrophotometer. The aim of the present study was to develop a new microlight guide suitable for measurements in the round window niche and to evaluate electrophysiologically the possible impact of the procedure on the cochlea. METHODS: Measurements were made for wavelengths of 450 to 900 nm at a total power of 5.3 mW. The exit diameter of the light guide was 200 microns and the angle used was 20 degrees. The recording depth was about 250 microns. The atraumatic character of the spectrophotometry was demonstrated by monitoring the compound action potential (CAP) threshold tuning curve from 1 to 34 kHz in ketanest-anesthetized guinea pigs. RESULTS: CAP thresholds remained constant (0.3 +/- 3.9 dB SPL) during 3 to 30 min of exposure to the light. CONCLUSIONS: These results suggest that the spectrophotometry may be useful as a new technique for intraoperative monitoring of intracapillary hemoglobin without causing physiological deterioration of the cochlea.

Animals↗
PubMed1996

[What is the value of color-coded duplex ultrasound in diagnosis of head-neck tumors].

BACKGROUND: The aim of the present study is to demonstrate the rating of low flow color duplex echography as a new technique in the preoperative staging of head and neck cancer. METHODS: Forty-four patients with squamous cell carcinomas of the oral cavity, oropharynx, and hypopharynx were examined. Gray scale imaging as well as color duplex scan with doppler spectrum quantification were performed on each patient using a Siemens Quantum 2000 duplex scan with 7.5 MHz linear array. RESULTS: Squamous cell carcinomas of the upper aerodigestive tract as well as their metastases are poorly vascularized but show irregular vascular patterns. In comparison to gray scale echography estimation of tumor borderline is improved by imaging of peripheral tumor vessels. Furthermore, imaging of irregular central tumor vessels in metastatic lymphatic nodes renders important information for N-staging. CONCLUSION: Thus color duplex echography should be recommended for routine application in preoperative head and neck tumor staging.

Blood Flow Velocity↗
PubMed1994

[Diseases of the petrous bone--demands made on radiologic diagnosis from the otosurgical point of view].

Advances in microsurgical techniques in otosurgery as well as further developments in imaging methods enable the surgeon to perform procedures at the petrous bone that are as radical as they can contribute to retaining the function. The present study aims at explaining by means of case reports the specific otosurgical problems in typical diseases of the otobase and at presenting the ranking of the individual imaging methods from the surgeon's point of view. For example, special features in the preoperative diagnosis of glomus tumours, acoustic neurinomas, Ménière's disease, cholesteatomas and so-called petrous bone tip processes are pointed out. A special aspect of radiological and surgical collaboration is seen in highly vascularised tumours of the otobase in respect of the possibilities offered by interventional angiography. The importance of MR-tomography in preoperative diagnostics is assessed with some reservation because this does not show up surgically relevant landmarks.

Aged↗
PubMed1993

[3D reconstruction by high resolution MR tomography of the inner ear].

By means of modern 3D-visualization systems it is possible to render detailed reconstructions of very small morphological structures such as the inner ear. Aim of the present study was to demonstrate the imaging quality of a new 3D-segmentation program developed in the University of Hamburg. The investigation was carried out on a high-resolution MR-tomography of the author's labyrinth and facial nerve. The images were obtained with a fast-field-echo technique using a surface coil. 32 axial slices of 1.0 mm thickness were used for reconstruction. Thus it was possible to completely visualize cochlea, semicircular canals and facial nerve. Especially the filiform substructures of the inner ear could reliably be reconstructed. So the content of information of the MR-investigation could be increased by the 3D-technique applied.

Computer Simulation↗
PubMed1992

["Crown-cork tympanoplasty"--a method for complete reconstruction of the tympanic membrane].

The crowncorktympanoplasty is a technique for the total reconstruction of the tympanic membrane, recommended in cases of ear malformation, blunting-phenomena and total deficiency of the membrane caused by chronic otitis media. Autologous tragal composite graft is used for the myringoplasty. While the cartilage faces to the middle ear cavity, the overflapping perichondrium is layed on the bony meatal wall in the manner of a crowncork. 10 cases performed in the last two years are reported. In each one an intact tympanic membrane could be reached. In average, the ear bone gap could be reduced for 18.5, 17.5, 16.5 and 13.5 dB in the frequencies of 500, 1000, 2000 and 4000 Hz.

Adolescent↗