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Biomedical subjects

S Riederer

Publications and source records attributed to S Riederer.

9 recordsLinked to original sources
PubMed2005

Study of CP(N-1) theta-vacua by cluster simulation of SU(N) quantum spin ladders.

D-theory provides an alternative lattice regularization of the 2D CP(N-1) quantum field theory in which continuous classical fields emerge from the dimensional reduction of discrete SU(N) quantum spins. Spin ladders consisting of n transversely coupled spin chains lead to a CP(N-1) model with a vacuum angle theta=npi. In D-theory no sign problem arises and an efficient cluster algorithm is used to investigate theta-vacuum effects. At theta=pi there is a first order phase transition with spontaneous breaking of charge conjugation symmetry for CP(N-1) models with N>2.

Journal Article↗
PubMed1998

Chronic post-traumatic radial instability of the metacarpophalangeal joint of the finger. Long-term results of ligament reconstruction.

Chronic painful post-traumatic instability of the radial collateral ligament complex of the metacarpophalangeal joint of a finger was treated by tendon graft reconstruction in 24 patients. Seventeen patients (20 joints) were available for a retrospective study at a mean follow-up time of 105 months. Eighty percent of the joints showed excellent or good results, with relief of pain, return of adequate stability, a near normal range of motion and absence of degenerative changes.

Chronic Disease↗
PubMed1994

[Organization and significance of quality control in recent surgical methods exemplified by 85 consecutive thoracoscopic interventions].

The rapid evolution or rather revolution of minimally invasive surgical techniques is stimulating new technical and clinical innovations. Quality control is of great importance in new areas of technical development where standards do not yet exist. By recording detailed documentation of patient data, indications, operative procedures and initial follow-up we can compare this new technology with the gold standard therapy. This documentation system for thoracoscopic interventions was developed together with the Swiss Group of Laparoscopic and Thoracoscopic Surgeons. This pilot project of 85 consecutive thoracoscopic interventions will demonstrate the acceptability, clinical application and ease with which data can be analyzed. Operative techniques are described in detail: 20 diagnostic interventions with biopsy, 19 apical parietal pleurectomies (+/- resections of bullous lung tissue), 10 therapeutic lung tissue resections, 19 palliative pleurodesis, 5 treatments of pleural empyema, 1 mediastinal tumor resection, 1 esophagectomy, 4 thoracic sympathectomies plus 6 other procedures. Data entry is efficient with mean total time of 10 min for each record. All of the data are entered into a computer database. The possibilities for interpreting and combining this data are presented. The operative techniques can easily be related with history, indications, anesthesia, complications and results. First evaluation of thoracoscopic efficiency is possible. In addition, a detailed analysis of intra- and postoperative complications and of the hospital course can be performed.

Documentation↗
PubMed1994

[Minimally invasive thoracic surgery].

Surgery of the intrathoracic organs may be performed without compromise of respiratory mechanics considering minimally invasive principles. An analysis of our experience of 373 thoracoscopic interventions reveals that the diverse procedures performed on the pleura (pleurectomy, pleurodesis), on the lung (wedge resection, fistula closure, ligature of parenchymatous leaks) and on other definec anatomical structures such as the sympathetic nerve or the thoracic duct, are effective in the therapy of intrathoracic disease. The most important pathological conditions which may be treated by thoracoscopy are listed. The range of complications (7%) and their causes are discussed. Current developments and innovations are summarized by a short review of the literature.

Cause of Death↗
PubMed1986

Parkinson plus syndrome: diagnosis using high field MR imaging of brain iron.

The distribution of iron in the brain was analyzed using high field strength (1.5 T) magnetic resonance (MR) imaging in 14 healthy control individuals and six patients with Parkinson plus syndromes (multisystem atrophy and progressive supranuclear palsy) who were unresponsive to antiparkinsonian therapy. The normal topographic distribution of iron in the brain as indicated by high field MR images coincided precisely with the distribution of iron in the brain as determined by Perls staining for ferric iron. In Parkinson plus syndromes, there were abnormally increased concentrations of iron (decreased T2 relaxation times) in the putamen, and less prominent increases in the caudate nucleus and lateral pars compacta of the substantia nigra. In high field strength MR images of normal patients, the decreased signal intensity in the globus pallidus is more prominent than that of the putamen. In MR images of patients with Parkinson plus syndromes, the decreased signal intensity of the putamen is more prominent than that of the globus pallidus.

Adult↗
PubMed1986

MRI of brain iron.

A prominently decreased signal intensity in the globus pallidum, reticular substantia nigra, red nucleus, and dentate nucleus was routinely noted in 150 consecutive individuals on T2-weighted images (SE 2000/100) using a high field strength (1.5 T)MR system. This MR finding correlated closely with the decreased estimated T2 relaxation times and the sites of preferential accumulation of ferric iron using the Perls staining method on normal postmortem brains. The decreased signal intensity on T2-weighted images thus provides an accurate in vivo map of the normal distribution of brain iron. Perls stain and MR studies in normal brain also confirm an intermediate level of iron distribution in the striatum, and still lower levels in the cerebral gray and white matter. In the white matter, iron concentration is (a) absent in the most posterior portion of the internal capsule and optic radiations, (b) higher in the frontal than occipital regions, and (c) prominent in the subcortical "U" fibers, particularly in the temporal lobe. There is no iron in the brain at birth; it increases progressively with aging. Knowledge of the distribution of brain iron should assist in elucidating normal anatomic structures and in understanding neurodegenerative, demyelinating, and cerebrovascular disorders.

Adolescent↗
PubMed1982

Intracranial intravenous digital subtraction angiography.

Intravenous digital subtraction angiography (iDSA) promises to significantly alter the use of conventional cerebral angiography in the workup of neurological patients. Understanding its diagnostic potential and its limitations are important in incorporating this new examination into the diagnostic thought process of neuroradiologic tests. Different image processing techniques such as integration of mask and contrast images promise to improve image quality for neuroradiologic application. At present, iDSA is suitable for the diagnosis and follow-up of vascular lesions (atherosclerosis, aneurysms, arteriovenous malformations, venous sinus occlusion), and tumor (meningioma). Although limited, the spatial resolution of iDSA studies is capable of demonstrating diffuse vascular disease such as arteritis and vasospasm after subarachnoid hemorrhage. In some patients in conjunction with the CT scan, iDSA may prove sufficient as the primary and only diagnostic angiographic test necessary, supplanting conventional angiography.

Arteriosclerosis↗