Search PubMed⌕ Search

Biomedical subjects

F Dammann

Publications and source records attributed to F Dammann.

52 records · Page 3Linked to original sources
PubMed1997

[Value of dacryocystography in localization diagnosis of lacrimal duct stenosis].

PURPOSE: Evaluation of dacryocystography in the preoperative localisation of stenosis of the lacrimal passage. METHOD: The lacrimal system of 20 patients (25 eyes) suffering from lacrimal passage obstruction was examined either by conventional (n = 20) or by digital (n = 5) technique. Diagnostic imaging was evaluated concerning topographic Information of the pathologic lacrimal system, localisation of the level and differential diagnosis of the cause of the obstruction. RESULTS: Cause of the obstruction was chronic dacryocystitis (n = 16), dacryolithiasis (n = 1), atresia of the lacrimal duct (n = 2), posttraumatic lesions (n = 3), rhinosinusitis (n = 1) and carcinoma of the maxillary sinus (n = 1). In 23 of 25 cases (92%) we found an exact correlation between dacryocystography and the intraoperative findings. The variation of stenosis types as well as different examination techniques are presented and compared with literature findings. CONCLUSION: Dacryocystography is a valuable method in the diagnosis and preoperative planing in lacrimal system obstruction.

Adolescent↗
PubMed1997

MR imaging of the liver with Resovist: safety, efficacy, and pharmacodynamic properties.

PURPOSE: To evaluate the safety, efficacy, and pharmacodynamic properties of a new superparamagnetic parenteral iron oxide contrast agent for magnetic resonance (MR) imaging. MATERIALS AND METHODS: Thirty-six patients with liver lesions received a bolus injection of Resovist (SH U 555 A; Schering, Berlin, Germany) at a dose of 4, 8, or 16 micromol iron per kilogram body weight (micromol Fe/kg). Fast low-angle shot, spin-echo, and turbo gradient spin-echo MR images were obtained before and 10, 40, and 70 minutes after injection. Blood samples were obtained, vital signs were monitored, and adverse events were recorded. Lesion detection was assessed by two independent, blinded readers. RESULTS: No drug-related adverse events occurred. Serum iron and ferritin levels were increased at all dose levels. Partial thromboplastin time increased and factor XI level decreased 4 hours after injection of 16 micromol Fe/kg. Lesion detection and diagnostic confidence were increased in patients who received 4 or 8 micromol Fe/kg, with no further increase with a 16-micromol dose. CONCLUSION: Resovist is safe and effective. The best MR imaging results were obtained 40 minutes after injection of 8 micromol Fe/kg.

Adult↗
PubMed1997

Do mammography, sonography, and MR mammography have a diagnostic benefit compared with mammography and sonography?

OBJECTIVE: The purpose of our study was to assess the added value of MR mammography, mammography, and sonography compared with mammography and sonography in diagnostic evaluation of the breast. MATERIALS AND METHODS: We evaluated reports of MR mammography, conventional mammography, and sonography of the breast in 89 patients who had been referred for surgical biopsy. The dynamic MR mammography examinations were obtained on a 1.0-T MR imager using a double-breast coil and a three-dimensional axial fast low-angle shot sequence. Each type of study was interpreted by a different observer. All mammograms and sonograms were available to all observers. Without knowledge of biopsy results, observers classified mammograms and sonograms (which we call the standard method) as well as mammograms, sonograms, and MR mammograms (which we call the combined method). Classifications were on a per-breast basis: no disease; probably a benign or malignant lesion; and most likely a benign or malignant lesion. A classification of no disease or most likely a benign or malignant lesion was considered to represent a high confidence of the observer in the diagnosis. RESULTS: Of 98 breasts evaluated with the standard method, observer confidence was high for 44% of all malignant lesions versus 86% with the combined method. The highest specificity (92%) was achieved by interpretation of the standard method (combined method, 64%). The highest sensitivity (95%) was achieved by interpretation of the combined method (standard method, 83%). Overall accuracy was 87% for the standard method and 83% for the combined method. In separate analyses of nonpalpable and palpable lesions, the combined method achieved an accuracy of 74% for nonpalpable lesions and 88% for palpable lesions. The standard method achieved an accuracy of 85% for nonpalpable lesions and 88% for palpable lesions. CONCLUSION: MR mammography as an adjunct to mammography and sonography reveals breast cancer with a higher confidence and sensitivity than do mammography and sonography only. The combined method can be recommended if the greatest possible sensitivity or negative predictive value is wanted. However, the combined method is not useful for screening or workup of suspicious lesions because of its lower specificity and accuracy.

Breast↗
PubMed1995

Adapted techniques for clinical MR imaging of tendons.

To determine whether the echo time of magnetic resonance gradient-echo and spin-echo imaging sequences may be important for the occurrence of high signal strength from tendon with pathological alterations, imaging sequences with sufficient spatial resolution and very short echo times were developed for whole-body imagers with standard gradient system. The sequences were applied on the Achilles tendons of five healthy volunteers and seven patients with achillodynia. Some affected regions inside tendon, probably corresponding with tissue with subtle edema in the collagen bundles were only revealed in images recorded with very short echo times TE < 5 ms, whereas stronger affections and protons in liquids between the fiber bundles were also shown in images with longer echo times TE > 10 ms. Gradient-echo methods allow shorter echo times than spin-echo techniques for a given gradient system of the imager and given spatial resolution. So minimum echo time gradient-echo sequences should be used for sensitive imaging of tendon alterations, because no considerable signal dephasing due to susceptibility effects were found in tendon.

Achilles Tendon↗
PubMed1995

[Value of the AMBER system in interstitial lung changes].

PURPOSE: To evaluate the diagnostic value of the AMBER technique in the diagnosis of interstitial lung disease. METHODS: A prospective comparison of conventional and AMBER chest radiographs of 52 patients was performed using HR-CT as a gold standard on the same day. ROC analysis based on the results of 5 observers was carried out to quantify the diagnostic value of both chest radiograph techniques. RESULTS: The ROC area for the AMBER system (0.860) showed statistically significant superiority in comparison to the conventional technique (0.828). This was mainly due to the better sensitivity of the AMBER system (65.3%) compared to the conventional chest radiographs (39.8%) within the lung regions superimposed by the diaphragm or the mediastinum. No difference between both methods was observed within the lung regions without superimposion. CONCLUSION: AMBER technique improved conventional chest radiography in the diagnosis of interstitial lung disease due to superiority in the superimposed lung regions.

Evaluation Studies as Topic↗
PubMed1995

Comparison of magnetic resonance imaging methods for examinations of abdominal aortic aneurysms.

RATIONALE AND OBJECTIVES: Different magnetic resonance imaging techniques were compared with respect to available anatomic information regarding abdominal aortic aneurysms (AAA) and regions involved in thrombosis. METHODS: Twenty patients with AAA were examined by turbo spin-echo (TSE) imaging of coronal and transverse slices, resulting in black blood images. Bright blood imaging was performed using a spoiled gradient-echo sequence with gradient moment nulling. Sets of 25 to 50 thin slices were recorded sequentially in a single slice mode using coronal and transverse orientation. Both sets of bright blood images were reconstructed by maximum intensity projection. RESULTS: In all patients, the size and shape of the AAA could better be assessed by the TSE images than by the gradient-echo images. In contrast, reliable differentiation of thrombotic areas and of the perfused lumen was possible in only 56% of the slices recorded by TSE imaging but in 94% of the gradient-echo images. The two-dimensional inflow technique provided clearly higher sensitivity even to slow blood flow than TSE imaging. Maximum intensity projection reconstructions from sets of coronal two-dimensional inflow images often did not depict the lower part of the AAA because of saturation effects, whereas sets of transverse slices provided complete angiograms of the aortoiliac vascular tree. DISCUSSION: At this time, no single magnetic resonance method can provide all essential information. A comprehensive examination should include TSE imaging for topographic assessment and transverse two-dimensional inflow imaging for analysis of thrombotic areas.

Aged↗
PubMed1995

[Modern radiologic diagnosis for the ENT physician].

Radiologic diagnosis has acquired an increased importance in head and neck diseases since the introduction of sectional imaging techniques. In addition to clinical and endoscopic examinations, CT has become the standard modality for TNM staging of malignant diseases. CT is also a basic tool in diagnosing benign diseases localized in or infiltrating into the deep head and neck regions. Ultrasound is widely available and is now well established in the diagnosis of superficial pathologies. Magnetic resonance is the newest imaging modality and is being increasingly used in clinical practice. By avoiding ionizing radiation MRI provides an improved method for contrast studies and enables high-quality multiplanar imaging. The applications of this method are still expanding with ongoing refinements of MR imaging techniques. Conventional radiological methods remain limited to a few indications. Radiation dose and cost have now required replacement of traditional step-by-step diagnostic methods by the one method that can meet most requirements in a single examination.

Humans↗
PubMed1989

M2 muscarinic receptors on the iris sphincter muscle differ from those on iris noradrenergic nerves.

The pre- and postjunctional affinity constants of a series of muscarinic antagonists were determined in guinea pig and rabbit irises. Field stimulation-evoked [3H]noradrenaline release from superfused isolated irises was concentration dependently inhibited by (+/-)-methacholine, confirming the presence on the iris noradrenergic nerves of prejunctional inhibitory muscarinic receptors. The affinity constants of the antagonists at the pre- and postjunctional receptors are compatible with the coexistence in the iris of two different M2 receptors: the cardiac (M2 alpha) subtype on the noradrenergic nerves and the smooth muscle (M2 beta) subtype on the iris sphincter muscle. The rank order of potency of the antagonists studied at the prejunctional site was: atropine greater than himbacine greater than AF-DX 116 greater than pirenzepine greater than hexahydrosiladifenidol. The order of potency at the postjunctional receptors mediating the methacholine-induced isotonic contraction of the isolated rabbit iris sphincter was: atropine greater than hexahydrosiladifenidol greater than pirenzepine greater than himbacine greater than AF-DX 116.

Animals↗
PubMed1989

AF-DX 116 differentiates between prejunctional muscarine receptors located on noradrenergic and cholinergic nerves.

Prejunctional affinity constants of the cardioselective muscarine receptor antagonist AF-DX 116 (11-[(2-[(diethyl-amino)methyl]-1-piperidinyl)acetyl]-5,11-dihydro-6 H-pyrido [2,3-b] [1,4] benzodiazepine-6-one) were determined for muscarine autoreceptors on cholinergic nerves of the guinea-pig ileum and for heteroreceptors on noradrenergic nerves of the rat heart and guinea-pig iris. AF-DX 116 antagonized with low affinity the muscarinic inhibition induced by arecaidine propargyl ester of the stimulation-evoked [3H]acetylcholine overflow (pA2 6.74) from the guinea-pig ileum. In contrast, AF-DX 116 was more potent in antagonizing the methacholine-induced inhibition of the stimulation-evoked [3H]noradrenaline overflow from rat heart (pA2 7.29) or guinea-pig iris (pA2 7.57). The data confirm previously reported differences between prejunctional muscarine heteroreceptors in the rat heart which belong to the cardiac subtype (M2 alpha or M2) and autoreceptors in the guinea-pig ileum that cannot be distinguished from the ileal subtype (M2 beta) or M3).

Acetylcholine↗
PubMedDate not supplied

Computer-aided surgical planning for implantation of hearing aids based on CT data in a VR environment.

A study was undertaken to assess the feasibility of a preoperative fitting test for an implantable hearing aid in a virtual reality (VR) environment. High-resolution spiral computed tomography (CT) of the mastoid bone was performed, and the results of a mastoidectomy were simulated with manual segmentation on a standard medical workstation. CT was also performed on a temporal bone specimen obtained at real mastoidectomy, and the bone margins were segmented automatically with threshold-based techniques. A triangulated surface representation of the bone structures including the mastoid cavity was generated. These data as well as the computer-aided design (CAD) files of the medical devices were transferred into a VR environment. The CAD components of the hearing aid were manipulated to simulate the surgical implantation procedure. Merging CAD data of an implantable hearing aid with CT data of the temporal bone in a VR environment was shown to be a feasible method of providing three-dimensional information for the presurgical determination of fit and mountability. Advances in hardware and software are expected to improve the usability of this method. Although clinical studies are needed, these results may serve as an impetus for exploring the use of low-cost, widely available VR computer equipment in a potentially broad field of clinical applications.

Cochlear Implants↗