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Biomedical subjects

W Wiesmann

Publications and source records attributed to W Wiesmann.

At least 19 recordsLinked to original sources
PubMed1996

Effect of spaceflight on human stem cell hematopoiesis: suppression of erythropoiesis and myelopoiesis.

Humans subjected to periods of microgravity develop anemia, thrombocytopenia, and abnormalities in red blood cell structure. The causes of these abnormalities are complex and unclear. The in vitro effects of spaceflight on hematopoietic cell proliferation and differentiation were investigated during the space shuttle missions STS-63 (Discovery) and STS-69 (Endeavour). CD34+ bone marrow progenitor cells were cultured in liquid suspension culture and on hematopoietic supportive stromal cells using hollow-fiber culture modules. One set of cultures was maintained at microgravity (flight cultures) for the last 8-10 days of culture and a second control was at full gravity (ground control). Over the 11- to 13-test-day period, ground control culture total cell number increased 41.0- to 65.5-fold but flight culture total cell number increased only 10.1- to 17.6-fold (57-84% decrease). Comparing ground control cultures and microgravity cultures, respectively, for progenitor cell content, myeloid progenitor cell numbers expanded 2.6- to 17.5-fold compared with 0.9- to 7.0-fold and erythroid progenitor cell numbers expanded 2.0- to 4.1-fold in ground control cultures but actually declined at microgravity (>83% reduction). Moreover, microgravity cultures demonstrated accelerated maturation/differentiation toward the macrophage lineage. These data indicate that spaceflight has a direct effect on hematopoietic progenitor cell proliferation and differentiation and that specific aspects of in vitro hematopoiesis, particularly erythropoiesis, involve gravity-sensitive components.

Antigens, CD↗
PubMed1994

[Documentation with a digital image workstation].

PAC systems are economically advantageous if the use of hardcopies for reporting, archiving and demonstrations is restricted. In place of a film a CRT display has to be used for visualisation. Problems in reporting regarding brightness, contrast, intensity and spatial resolution are described and compared to conventional X-ray films. Results from different studies using CRT displays for reporting are summarised and compared. Some of these studies show reduced diagnostic accuracy if a CRT display is used. This problem may be solved by further developments and by the implementation of software, e.g. computer-aided diagnosis. If the quality of reporting on a CRT display is increased and equivalent to the film, the introduction of a PACS will be qualitatively and economically acceptable.

Computer Systems↗
PubMed1992

Comparison between high-field-strength MR imaging and CT for screening of hepatic metastases: a receiver operating characteristic analysis.

The diagnostic performance of high-field-strength magnetic resonance (MR) imaging (1.5 T) for detection of liver metastases was compared with that of computed tomography (CT). All patients (n = 52) underwent preoperative screening for metastases by means of MR imaging with T1-weighted, proton-density-weighted, and T2-weighted pulse sequences and CT scanning with unenhanced, incremental dynamic bolus-enhanced, and delayed contrast medium-enhanced techniques. Diagnostic performance was evaluated by means of receiver operating characteristic analysis in which 800 images (400 with and 400 without lesions) and five readers (4,000 observations) were used; images were obtained from patients (n = 39) in whom the same anatomic levels were available for all MR imaging and CT studies. Direct comparison between the best MR imaging technique (T2-weighted spin-echo imaging [repetition time, 2,000 msec; echo time, 70 msec]) and the best CT technique (incremental dynamic bolus CT) showed a strong trend of superiority of T2-weighted MR imaging over incremental dynamic bolus CT. No highly statistically significant difference (P greater than or equal to .01), however, was found between these two techniques.

Esophageal Neoplasms↗
PubMed1992

Impact of hard-copy size on observer performance in digital chest radiography.

To determine the impact of reduced hard-copy size on diagnostic performance of digital radiography, screen-film chest radiographs were compared with isodose digital storage phosphor radiographs in the detection of simulated nodules, fine pulmonary lines, and micronodular opacities superimposed on the chests of 10 healthy volunteers. Digital radiographs were laser-printed in a full-size conventional format and in image lengths of two-thirds, one-half, and five-elevenths of the conventional format. Eighteen thousand observations by eight radiologists were analyzed by use of receiver operating characteristics. The detectability of lines and micronodular opacities decreased with declining image format size. In the detection of micronodular opacities, only the nearly full-size digital images were equivalent to conventional images. In the detection of linear opacities, reduction of image length by one-half or more reduced performance (analysis of variance, P less than .05). Only for the detection of nodules was no major difference found.

Humans↗
PubMed1992

[An economic comparison between digital luminescence radiography and conventional film processing in intensive care medicine].

The costs of a conventional film-screen radiography daylight-system and storage-phosphor computed radiography (Fuji AC-1) are compared. In 1990, 3841 radiologic procedures (mostly portable chest X-rays) were performed in 3474 patients of a surgical intensive care unit. With conventional film-screen radiography 6.8% retakes were necessary for diagnostic or technical reasons. Comparing the fixed and variable costs of both systems conventional film-screen radiography was more economic under the given conditions of the test. It is concluded that computed radiography in intensive care patients has definite advantages in terms of image quality and reproducibility, however, in order to compete successfully in the economic turf CR has to be implemented in a picture archiving and communication system (PACS).

Costs and Cost Analysis↗
PubMed1992

[Hemangioma of the left ventricle].

The authors describe the case of a histologically proven hemangioma in the left coronary artery of the left ventricle of a 24-year-old woman. The results of the different medical imaging methods applied are described and the treatment of cardiac angiomas is discussed.

Adult↗
PubMed1991

[Artificial respiration in the prone position in a case of acute respiratory distress syndrome].

A patient is presented in whom an acute respiratory distress syndrome (ARDS) developed after severe lung contusion. Exchange of gas was markedly restricted under aggressive respiration (FiO2 = 1.0, PEEP = 10 mmHg, breathing time quotient = 0.5, respiratory minute volume = 16 litres; gas exchange values: PaO2 = 67 mmHg, PaCO2 = 45 mmHg, PA-aO2 = 461 mmHg). After control of the computed tomogram of the lungs showed marked densifications in those parts of the lung that are lower most by gravitation according to the positioning of the patient at a particular time the patient was ventilated in ventricumbent (prone) position for 60 hours. After having remained in this position for 48 hours, there was a significant improvement in the gas exchange (PaO2 = 89 mmHg, PaCO2 = 36 mmHg, PA-aO2 = 77 mmHg at FiO2 = 0.3, PEEP = 6 mmHg, breathing time quotient = 0.5 and respiratory minute volume = 9 litres). The control CT in dorsal position showed that the dorsal densifications had disappeared completely. Five days later the patient could be extubated. Respiration in ventricumbent (prone) position may considerably improve oxygenation by perfusion of well-ventilated regions of the lung that are lower-most by gravitation according to the relative positioning of the patient. Besides regions not well ventilated or not ventilated at all (according to the patient's position) may be better ventilated or re-opened and made accessible to ventilation by this method.

Adult↗
PubMed1991

[A comparison between digital luminescence radiography and conventional myelography].

The potential of digital luminescence radiography in replacing conventional myelography was analyzed using ROC methodology. 95 conventional (CR), digital (DR) and edge enhanced digital (EDR) myelograms (49 disk herniations, 46 normal) were read independently by 5 radiologists; and a ROC analysis was performed. Higher confidence levels were used in making both correct and incorrect diagnoses with DR and EDR than with CR. However, no statistically significant differences between AUC (area under the curve) values obtained with the different techniques, were noted. The separate analysis of cervical and lumbar myelograms showed no significant differences between the different techniques. With DR and EDR, the sensitivity of 4 of 5 readers was somewhat higher in the lumbar but lower in the cervical region than with CR. Replacement of conventional by digital luminescence myelography seems possible; however, some decrease of sensitivity in the cervical region must be accepted.

Humans↗
PubMed1991

Detection of hepatic masses in patients with carcinoma: comparative sensitivities of sonography, CT, and MR imaging.

To evaluate the sensitivity of sonography, CT, and MR imaging in the detection of hepatic masses in carcinoma patients, we conducted a prospective study of 75 consecutive patients with gastrointestinal tumors who were admitted for surgical resection of the primary tumor. Sonography was performed with convex transducers of 3.5 and 5.0 MHz. Three noninvasive CT techniques were used: unenhanced CT scans, the incremental bolus dynamic scanning technique, and delayed scanning 4-6 hr after bolus injection of 60 g of iodine. MR images (1.5 T) were acquired as presaturated T1- and T2-weighted spin-echo sequences and as breath-holding fast low-angle shot (FLASH) 60 degrees and FLASH 15 degrees sequences. As it is difficult to distinguish benign from malignant masses solely on the basis of morphologic criteria, the techniques for each imaging method were designed to detect and not to characterize hepatic lesions. Each examination was interpreted blindly, and the results were compared with surgical findings, intraoperative sonography, and biopsy of the liver as the gold standard. All focal hepatic masses verified at surgery, malignant or benign, were included in the analysis. Sixty-five (68%) of 95 focal hepatic masses were detected by CT, 60 lesions (63%) by MR, and 50 lesions (53%) by sonography. Although lesions 1-2 cm were shown almost equally well by CT and MR (74% and 77%, respectively), the detection rate of smaller lesions (less than 1.0 cm) decreased more drastically with MR (31%) than with CT (49%). Sonography had a sensitivity of only 20% with the smaller lesions. All imaging techniques had a sensitivity of 100% for focal hepatic masses larger than 2.0 cm. Our results show that CT has a higher overall sensitivity (68%) than MR and sonography for the detection of focal hepatic masses. When the results of the three procedures are combined, the overall sensitivity is 77%. This is unsatisfactorily low, as CT and MR have a size threshold of about 1.0 cm and are relatively unreliable for the detection of smaller lesions.

Adenocarcinoma↗
PubMed1991

[The diagnostic reliability of the occipitomental radiograph of the paranasal sinuses. Correlation with magnetic resonance tomography].

100 conventional occipitomental radiographs of the paranasal sinuses were studied independently by five radiologists. Predictive values were determined, based on MRI as the gold standard. Sensitivity and specificity for detection of mucosal thickening in the sinuses were: maxillary sinus: 0.73/0.76, frontal sinus: 0.20/0.85, ethmoid sinus: 0.38/0.87, sphenoid sinus: 0.14/0.96. In the maxillary sinus polypoid thickening was demonstrated with a significantly higher sensitivity than that of diffuse mucosal thickening (0.82 versus 0.65, Chi-square-test, p less than 0.01). Because of the low predictive values the occipitomental view is insufficient to assessing mucosal thickening in the paranasal sinuses, with the exception of polypoid mucosal thickening in the maxillary sinus.

Adult↗
PubMed1991

[Magnetic resonance tomography of the ankle joint].

To define the clinical role of MRI of the ankle joint, a total of 88 patients was investigated. In the evaluation of ligamentous injury, MRI was inferior to established imaging methods. By contrast, it provided additional therapy-relevant information in the assessment of hemophilic arthropathy, osteochondritis dissecans, and inflammatory and neoplastic diseases of the ankle joint. In the latter conditions, MRI may make other more conventional methods of examining the ankle joint unnecessary.

Ankle Injuries↗
PubMed1991

[A method of estimating doses in digital luminescent radiography].

Digital storage phosphor radiography can produce images of a constant optical density over a wide range of exposure dose by adjusting reading sensitivity. Since overexposed images are not as readily recognized as with the conventional film-screen technique, a formula was designed, which calculates the radiation dose in the film plane from image sensitivity (S factor), latitude (L factor) and average grey value of the region of interest. To verify the formula, 168 measurements with variation of dose, kVp, L factor, S factor and the readout algorithm were performed using the DIGISCAN storage phosphor system (Siemens). The experiments confirmed the validity of the formula for an S factor of below 5000 (values during routine use 50-400). Correlation between dosimetrically measured radiation dose and the calculated dose was 0.997.

Humans↗
PubMed1990

[The visualization of metal implants with digital luminescence radiography].

DLR makes it possible to integrate conventional radiography into digital communication and storage methods (PACS) into radiology. The use of DLR has been compared with conventional film methods in the demonstration of hip prostheses. The high contrast differences at the edge of the metal implant leads to artifacts, which could result in erroneous interpretation. Suitable image manipulation makes it possible, however, to eliminate these artifacts almost completely. DLR leads to an improvement in diagnosis in those complications not specifically related to the prostheses.

Evaluation Studies as Topic↗
PubMed1990

[Computerized tomography diagnosis of opportunistic lung mycoses].

In 11 patients with opportunistic pneumo-mycosis, computed tomography revealed a predominantly nodular infiltration pattern of the lungs, which revealed particular features that showed a dependence on the species of pathogen involved and the stage of the disease. Computed tomography of the chest proved to be superior to conventional chest films in the clarification of unclear fungal pneumonia in patients on immunosuppressive treatment.

Aspergillosis↗
PubMed1989

[New aspects of preoperative imaging diagnosis in aggressive fibromatosis].

Aggressive fibromatosis is a surgical problem due to its tendency to recur following excision. The imaging methods available are presented and their diagnostic value discussed. A combination of different investigative procedures allows preoperative assessment of tumor type and extent and accurate planning of surgical procedure.

Angiography↗