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Biomedical subjects

M Langer

Publications and source records attributed to M Langer.

At least 109 records · Page 6Linked to original sources
PubMed1999

Stents for the treatment of aortic aneurysms. Review of devices, technique and results.

The endovascular treatment of abdominal aortic aneurysms has generated a great deal of interest since the early 1990s, and many different devices are currently available. The procedure of endovascular repair has been evaluated in many institutions and the different devices are compared. The first results were encouraging, but complications like endoleak, dislocation or thrombosis of the graft occurred. By the available devices the stent application is only promising, if the known exclusion criteria are strictly respected. Therefore a careful preinterventional assessment of the patient by different imaging modalities is necessary. As the available results up to now are preliminary and the durability of the devices has to be controlled, multicenter studies are required to improve the devices and observe their long-term success in the exclusion of abdominal aortic aneurysms.

Aortic Aneurysm↗
PubMed1998

[Endosonography controlled transgastric drainage of pancreatic pseudocysts].

BACKGROUND AND OBJECTIVE: Endoscopic drainage of a pancreatic pseudocyst is an alternative to surgical intervention. But transmural drainage carries the risk of bleeding or perforation. Effectiveness and complication rate of endoscopic ultrasound-guided drainage, to avoid these risks, was investigated. PATIENTS AND METHODS: Eleven patients (eight men, three women; mean age 55 years) with a pancreatic pseudocyst (nine with alcoholic and two with biliary pancreatitis) were studied prospectively between 1996 and 1998. In all of them transpapillary drainage of the cyst had not been technically possible. After an endoscopic ultrasound (EUS) examination, the gastric wall was incised with a fistulotome under EUS guidance. A guide-wire was then advanced through the fistulotome into the pseudocyst. A double pigtail catheter was implanted for drainage. The size of the pseudocyst was monitored sonographically at two-week intervals. RESULTS: A cystogastrostomy was successfully established in ten of the twelve patients without serious complication. The pseudocyst was no longer demonstrated after a mean of 4.2 months (2 weeks to 6 months), while a small pseudocyst (1.6 cm [0.9-2.4 cm) remained in three patients. In two of the latter the size of the pseudocyst increased again after removal of the drainage catheter. Complete drainage by repeat cystogastrostomy succeeded in one of them, while a cystojejunostomy was established in the other. CONCLUSION: Endoscopic ultrasound-guided transgastric drainage of a pancreatic pseudocyst is an effective treatment with few complications.

Adult↗
PubMed1998

A test of the claim that plan rankings are determined by relative complication and tumor-control probabilities.

PURPOSE: This study tests an accepted claim regarding tumor control (TCP) and normal tissue complication (NTCP) probability functions. The claim is that treatment plans can be ranked using relative probabilities, even when the absolute probabilities are unknown. The assumption supports the use of probability models for plan optimization and the comparison of treatment techniques. METHODS: The claim was tested using a hypothetical model consisting of two tissues, and illustrated with clinical data. Plans were scored using the probability of uncomplicated tumor control. The scores of different plans were compared by fixing their relative risks for an individual tissue complication, but adjusting the absolute probability levels up or down. The tested claim is that the plan rankings should not change. RESULTS: In the two-tissue model, the rankings of competing plans were reversed by doubling all the probabilities. The preference ordering of lung cancer plans changed after the risk of pulmonary complication was reduced by 3-fold. In another site, the ranking of plans by overall complication-free probability was disturbed by errors that preserved the ordering of plans with respect to any individual complication. An adjustment of +/- 2.5% in the initial NTCP values for two tissues changed the direction in which a plan score moved in response to a fixed tradeoff in complication risk in an optimization search. CONCLUSIONS: Contrary to claims, plan rankings are not determined by the relative probabilities of adverse events. The effect on plan scores of trading one complication for another depends on the absolute levels of risk. Absolute errors in NTCP and TCP functions result in the wrong ranking of plans, even when relative probabilities are correct. An optimization routine based on TCP and NTCP calculations may be forced in the wrong direction by small errors in the probability estimates.

Humans↗
PubMed1998

[Diverticulosis and diverticulitis in the elderly].

Diverticulosis of the colon is a disease that mainly affects the elderly, presenting in 10 to 20% of this age group. The most common complication--painful diverticular disease, is usually treated conservatively with a high-fiber diet, intermittent use of antispasmodics and possibly regulation of the stools. Diagnostic differentiation is best performed using ultrasonography of the bowel wall, supplemented where necessary by computer tomography and colonoscopy (sigmoidoscopy) or, where this latter is not possible, barium enema using Gastrografin. Conservative treatment of diverticulitis with antibiotics, bowel rest, possibly including parenteral alimentation, is usually applied for three to ten days. In the absence of a response to this treatment, frequent recurrence, immunosuppression or complications (perforation, peritonitis, enterovesicular fistula), surgery is indicated.

Aged↗
PubMed1998

MR findings in pontocerebellar hypoplasia.

We present four cases with combined hypoplasia of the cerebellum and the ventral pons-pontocerebellar hypoplasia (PCH). PCH represents an autosomal recessive neurodegenerative disorder with fetal onset. The disease is rare, with less than 20 cases having been reported. The main findings of PCH and the inclusion criteria for our cases can be summarised as progressive microcephaly from birth, pontocerebellar hypoplasia documented by MRI and marked chorea, which may change, later in childhood, to more dystonic patterns. The cerebral cortex becomes progressively atrophic. Motor and mental development are delayed, and epilepsy, mainly tonic-clonic seizures, is frequent. The MRI features in all of our cases were: (1) Hypoplastic cerebellum situated close to the tentorium. The hypoplastic cerebellum has a reduced number of folia, in contrast to the normal number of thin folia in simple cerebellar atrophy. (2) The cerebellar hemispheres are reduced to bean-like or wing-like structures. The cerebellar hemispheres appear to 'float' in the posterior fossa. (3) Markedly hypoplastic ventral pons. (4) Slight atrophy of the supratentorial gyral pattern. (5) Dilated cerebromedullary cistern and fourth ventricle. (6) Delayed myelination of the white matter. (7) No significant disorganisation of brain architecture and no severe corpus callosum defect.

Cerebellum↗
PubMed1998

Comparison of turbo inversion recovery magnitude (TIRM) with T2-weighted turbo spin-echo and T1-weighted spin-echo MR imaging in the early diagnosis of acute osteomyelitis in children.

OBJECTIVE: To compare turbo inversion recovery magnitude (TIRM) with standard T1-weighted (T1-W) and T2-weighted (T2-W) MR sequences in the very early detection of acute osteomyelitis in children. MATERIALS AND METHODS: In 15 children with osteomyelitis, 15 sets of T1-W spin-echo (SE) (TR/TE, 400-640/12-17), T2-W turbo spin-echo (TSE) (TR/TE/ETL, 3290-4465/112-120/11), and TIRM (TR/TE/TI, 4000-6120/60/160) images were acquired with a 1.0-T magnet. Contrast-to-noise (C/N) ratios and percentage of signal between lesion and normal bone marrow were analysed with a computer-assisted image analysing system in a region of interest (ROI). RESULTS: In 13 of 15 patients, the absolute signal enhancement in a ROI on the TIRM images was better than on the T1-W SE and T2-W TSE images and in 14 of 15 cases, C/N ratios were also better on the TIRM images than on the other sequences. In the other cases, the TIRM signal was diagnostically equivalent. On the TIRM images, the signal difference between normal and pathological tissue was increased to 43-281% (mean 124%). On the T2-W TSE images, this signal difference was 4-79% (mean 36%) and on the T1-W SE images 6-77% (mean 37%). Conclusion. The TIRM sequence is highly sensitive for detecting bone marrow oedema in the very early stage of acute osteomyelitis in children. MRI utilising the TIRM sequence allowed for an early diagnosis. With scan time of less than 4 minutes, this sequence is superior to T1-W SE and T2-W TSE images for detecting early osteomyelitis-associated bone marrow oedema.

Acute Disease↗
PubMed1998

Cartilage destruction in small joints by rheumatoid arthritis: assessment of fat-suppressed three-dimensional gradient-echo MR pulse sequences in vitro.

PURPOSE: To assess the accuracy of different MR sequences for the detection of articular cartilage abnormalities in rheumatoid arthritis. DESIGN AND PATIENTS: Ten metacarpophalangeal joints and 10 metatarsophalangeal joints (specimens from arthritis patients undergoing ablative joint surgery) were examined with a fat-suppressed (FS) 3D FLASH, a FS 3D FISP, a FS 2D fast spin-echo T2-weighted, and a 2D FS spin-echo T1-weighted sequence. Each cartilage lesion and each cortical lesion was graded from 0 to 4 (modified Outerbridge staging system). Subsequently, the results of each sequence were compared with the macroscopic findings and statistically tested against each other. RESULTS: The study shows that 3D gradient-echo sequences with fat suppression were best for imaging and grading of cartilage lesions in arthritis of the small joints of the hands and feet. Using 3D techniques, all grade 2, grade 3, and grade 4 lesions of cartilage or cortical bone were detected. CONCLUSION: FS 3D gradient-echo techniques were best for the detection and grading of hyaline cartilage and subchondral bone lesions in rheumatoid arthritis. MRI has a great potential as an objective method of evaluating cartilage damage and bone erosions in rheumatoid arthritis.

Adipose Tissue↗
PubMed1998

A mild form of Proteus syndrome.

Proteus syndrome is a rare congenital hamartomatous syndrome. We report on the clinical and radiological appearances of a boy in order to illustrate the typical signs which include subcutaneous masses, in mild forms partial gigantism of hands and feet, hemihypertrophy, and bony abnormalities. We discuss how to make the definitive diagnosis on the basis of using a known rating scale, important aspects of differential diagnosis and clinical features, and diagnostic management.

Child, Preschool↗
PubMed1998

Human articular cartilage: in vitro correlation of MRI and histologic findings.

The aim of our study was to correlate MRI with histologic findings in normal and degenerative cartilage. Twenty-two human knees derived from patients undergoing amputation were examined with 1.0- and 1. 5-T MR imaging units. Firstly, we optimized two fat-suppressed 3D gradient-echo sequences. In this pilot study two knees were examined with fast imaging with steady precession (FISP) sequences and fast low-angle shot (FLASH, SPGR) sequence by varying the flip angles (40, 60, 90 degrees) and combining each flip angle with different echo time (7, 10 or 11, 20 ms). We chose the sequences with the best visual contrast between the cartilage layers and the best measured contrast-to-noise ratio between cartilage and bone marrow. Therefore, we used a 3D FLASH fat-saturated sequence (TR/TE/flip angle = 50/11 ms/40 degrees) and a 3D FISP fat-saturated sequence (TR/TE/flip angle = 40/10 ms/40 degrees) for cartilage imaging in 22 human knees. The images were obtained at various angles of the patellar cartilage in relation to the main magnetic field (0, 55, 90 degrees). The MR appearances were classified into five categories: normal, intracartilaginous signal changes, diffuse thinning (cartilage thickness < 3 mm), superficial erosions, and cartilage ulcers. After imaging, the knees were examined macroscopically and photographed. In addition, we performed histologic studies using light microscopy with several different stainings, polarization, and dark field microscopy as well as electron microscopy. The structural characteristics with the cartilage lesions were correlated with the MR findings. We identified a hyperintense superficial zone in the MR image which did not correlate to the histologically identifiable superficial zone. The second lamina was hypointense on MRI and correlated to the bulk of the radial zone. The third (or deep) cartilage lamina in the MR image seemed to represent the combination of the lowest portion of the radial zone and the calcified cartilage. The width of the hypointense second zone correlated weakly to the accumulation of proteoglycans in the radial zone. The trilaminar MRI appearance of the cartilage was only visible when the cartilage was thicker than 2 mm. In cartilage degeneration, we found either a diffuse thinning of all layers or circumscribed lesions ("cartilage ulcer") of these cartilage layers in the MR images. Early cartilage degeneration was indicated by a signal loss in the superficial zone, correlating to the histologically proven damage of proteoglycans in the transitional and radial zone along with destruction of the superficial zone. We found a strong effect of cartilage rotation in the main magnetic field, too. A rotation of the cartilage structures caused considerable variation in the signal intensity of the second lamina. Cartilage segments in a 55 degreesangle to the magnetic main field had a homogeneous appearance, not a trilaminar appearance. The signal behavior of hyaline articular cartilage does not reflect the laminar histologic structure. Osteoarthrosis and cartilage degeneration are visible on MR images as intracartilaginous signal changes, superficial erosions, diffuse cartilage thinning, and cartilage ulceration.

Aged↗
PubMed1998

Integrating HIS-RIS-PACS: the Freiburg experience.

With the integration of different formerly isolated information systems, such as Hospital Information System (HIS). Radiology Information System (RIS), Picture Archiving and Communication System (PACS) and modalities, we evolve towards an architecture of distributed information processing in radiology, the data being stored in distributed databases. The frontier between the cooperative information systems becomes more subtle than in the past, and it seems more convenient to distinguish the different computer functionalities or services used in radiology than to detail the functions of RIS and PACS. This paper opens with a description of the different computer services used in radiology and how they relate one to another. It also shows how these functionalities could be integrated within a global Radiology Information and Archiving System. Finally, it shows the degree of systems interconnection that can be achieved presently, using the PACS-RIS installation at the University Hospital of Freiburg as an example.

Computer Communication Networks↗
PubMed1998

Purification and functional characterization of an 85-kDa gelsolin from the ascidians Microcosmus sulcatus and Phallusia mammilata.

From the pharyngeal baskets of the ascidians Microcosmus sulcatus and Phallusia mammilata we have purified an 85-kDa protein that is characterized as a member of the gelsolin family. These proteins from both species show the same behaviour in functional assays. The ascidian gelsolin binds two actin monomers in a highly cooperative manner. This complex formation is Ca(2+)-dependent, but not completely reversible, as on removal of Ca2+ one actin monomer dissociates leaving a 1:1 complex between gelsolin and G-actin. The properties of F-actin severing and G-actin nucleation depend on the presence of free Ca2+ in a micromolar range, with half maximum activation at about 3 x 10(-6) M. The protein becomes inactivated when Ca2+ concentrations of 0.5 mM are exceeded. Fragmentation of F-actin by the ascidian gelsolin is comparably fast to that of vertebrate gelsolin. A steady state of actin fragmentation is reached within 2-4 s. Promotion of G-actin nucleation is also comparable to that of vertebrate gelsolin. Regarding functional aspects, the ascidian gelsolin is more closely related to vertebrate gelsolin than to an arthropod gelsolin from crayfish tail muscle.

Actins↗
PubMed1998

[RARE urography in pelvic tumors: diagnostic ranking and comparison with intravenous pyelography].

PURPOSE: To examine if RARE urography may replace conventional intravenous urography in patients with suspected urinary obstruction in pelvic tumours. MATERIALS AND METHODS: In a prospective trial on 120 patients with pelvic tumours scheduled for operation, biplanar RARE urography was performed and compared to conventional intravenous urography and ultrasound findings. RESULTS: In 30 out of 120 patients an ureteric obstruction was diagnosed by ultrasound. Sensitivity of RARE urography for obstruction was 98% as compared to 60% in conventional intravenous urography. In 12 patients additional retrograde cystoureterography showed a sensitivity of 83%. Specificity of RARE urography and intravenous urography was 100%. In combination with axial MR tomography RARE urography yielded a more precise localisation of the site of obstruction and the underlying cause (98%) as compared to conventional urography (60%) and ultrasound (56%). CONCLUSION: By use of RARE urography urinary obstruction can be reliably demonstrated or ruled out. Combining RARE urography with tomographic MR imaging allows the precise depiction of the site of the obstruction and may demonstrate the underlying pathology.

Aged↗
PubMed1998

[Clinical uses of proton magnetic resonance spectroscopy of the brain].

In spite of all the scientific advances of the past few years, proton magnetic resonance spectroscopy of the brain has not attained the status of a routine examination technique with clinically accepted indications. The method should be considered as an additional option to MR imaging for inherited and acquired encephalopathic changes as well as, in future, for localization diagnosis of epilepsies. A proton magnetic resonance spectroscopic investigation without a prior intensive clinical and imaging investigation is not useful. Above all, factors influencing metabolite distribution such as for example, serum osmolality must be known. Methodological prerequisites for the clinical application of proton resonance spectroscopy are, first of all, a high stability of the chosen technique as well as a sufficiently certain quantification of metabolites and the availability of a reference group. The use of short echo times is necessary for the quantification of glutamine and the osmolyte myo-inositol. Indications for individual cases in which clinical investigations and MR topography cannot provide sufficient certainty and spectroscopy can furnish additional information are, in addition to uses in neuropediatrics, the suspicion of Alzheimer's dementia, HIV encephalopathy in early manifestations, and unclarified depressions of consciousness accompanying liver cirrhosis.

AIDS Dementia Complex↗
PubMed1998

Functional MR imaging of the cervical spine in patients with rheumatoid arthritis.

PURPOSE: To evaluate functional MR imaging in patients with rheumatoid arthritis (RA) involving the cervical spine. MATERIAL AND METHODS: We used a device that allows MR examination to be made of the cervical spine in infinitely variable degrees of flexion and extension. Dynamic functional MR imaging was performed on 25 patients with RA. RESULTS: Functional MR imaging was able to show the degree of vertebral instability of the occipito-atlantal or atlanto-axial level as well as the subaxial level. By performing functional MR imaging, we were able to demonstrate the extent of synovial tissue around the dens, and the impingement and displacement of the spinal cord during flexion and extension. The basilar impression, the cord impingement into the foramen magnum, the cord compression, the slipping of vertebrae, and the angulation of the cord were all much more evident in functional than in static MR imaging. CONCLUSION: Functional MR imaging provided additional information in patients with RA, and is valuable in patients who have a normal MR study in the neutral position and yet have signs of a neurological deficit. Functional MR imaging is important in the planning of stabilizing operations of the cervical spine.

Adult↗