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Biomedical subjects

J Teubner

Publications and source records attributed to J Teubner.

At least 19 recordsLinked to original sources
PubMed2002

[Quality assurance with teleradiology].

Teleradiology offers many applications for quality assurance in medicine. The spectrum reaches from electronic consultations in emergency or special cases and double reading--along with new models of cooperative work and medical networks--to technical quality assurance and integration into interinstitutional and patient controlled health records. Regional teleradiology networks based on server concepts can fulfill the developing technical and organisational requirements. The increasing mobility arising from smaller radiological equipment and improved accessibility to experts with minimized visualisation and reporting systems will change the radiological world of tomorrow, especially in combination with the usage of knowledge based systems in reference data bases and computer assisted diagnosis (CAD). Teleradiology by itself must be liable to quality assurance measurements to prevent unnecessary radiation exposure or danger to the doctor patient relation.

Computer Communication Networks↗
PubMed2001

High performance thermoelectric Tl9BiTe6 with an extremely low thermal conductivity.

Tl 9BiTe (6) exhibits a thermoelectric figure of merit of ZT approximately 1.2 around 500 K, which significantly exceeds the state-of-the-art materials in this temperature range. The extraordinary thermoelectric performance is mainly due to the extremely low thermal conductivity of Tl 9BiTe (6) [ 0.39 W/(m times K) at 300 K]. In fact, the minimum lifetime of the phonons has to be taken into account to describe the thermal conductivity data.

Journal Article↗
PubMed2001

International investigation of breast MRI: results of a multicentre study (11 sites) concerning diagnostic parameters for contrast-enhanced MRI based on 519 histopathologically correlated lesions.

A multicentre study was undertaken to provide fundamentals for improved standardization and optimized interpretation guidelines of dynamic contrast-enhanced MRI. Only patients scheduled for biopsy of a clinical or imaging abnormality were included. They underwent standardized dynamic MRI on Siemens 1.0 (163 valid lesions > or = 5 mm) or 1.5 T (395 valid lesions > or = 5 mm) using 3D fast low-angle shot (FLASH; 87 s) before and five times after standardized bolus of 0.2 mmol Gd-DTPA/kg. One-Tesla and 1.5 T data were analysed separately using a discriminant analysis. Only histologically correlated lesions entered the statistical evaluation. Histopathology and imaging were correlated in retrospect and in open. The best results were achieved by combining up to five wash-in or wash-out parameters. Different weighting of false-negative vs false-positive calls allowed formulation of a statistically based interpretation scheme yielding optimized rules for the highest possible sensitivity (specificity 30%), for moderate (50%) or high (64-71%) specificity. The sensitivities obtained at the above specificity levels were better at 1.0 T (98, 97, or 96%) than at 1.5 T (96, 93, 86%). Using a widely available standardized MR technique definition of statistically founded interpretation rules is possible. Choice of an optimum interpretation rule may vary with the clinical question. Prospective testing remains necessary. Differences of 1.0 and 1.5 T are not statistically significant but may be due to pulse sequences.

Adult↗
PubMed2000

Relevance of sonographic B-mode criteria and computer-aided ultrasonic tissue characterization in differential/diagnosis of solid breast masses.

We aimed to evaluate the differential diagnostic value of a method of computer-assisted texture analysis in comparison to established ultrasonographic B-mode characteristics in the examination of solid breast masses. At two centers, 77 patients presenting with a solid mass on B-mode scan were studied at 7.5 MHz. Description of B-mode appearance included assessment of tumor shape, borders, presence of an echogenic rim, tissue architecture, internal echo structure, absorption and elasticity. For statistical pattern recognition, the following parameters were used: form factor, mean grey level, signal-to-noise ratio, mean gradient and correlation from the co-occurrence matrix. At center 1, the most decisive parameter for differential diagnosis was distortion of tissue architecture (sensitivity, SN, 83%; specificity, SP, 92%) and, at center 2, relation to the adjacent tissue (SN 93%, SP 92%). Among texture parameters, best discrimination was achieved for correlation from the co-occurrence matrix at center 1 (SN 58%, SP 73%) and for form factor at center 2 (SN 93%, SP 77%). Among sonographic criteria, the highest contribution to the diagnosis was found for an unsharp border (odds ratio, OR, 12.2), architectural distortion (OR, 8.6), fixation to skin or chest wall (OR, 9.0) and fixation to adjacent breast parenchyma (OR, 8.8), according to texture analysis for parameters form factor (OR 4.0) and correlation from the co-occurrence matrix (OR 4.7). Ultrasonographic texture analysis can be helpful as an additional parameter in differential diagnosis of breast tumors, but did not reach differential diagnostic accuracy of sonomorphologic features.

Adult↗
PubMed2000

The Consortium of Graduate Medical Schools in Australia: formal and informal collaboration in medical education.

CONTEXT: In 1996-97 three Australian medical schools adopted 4-year graduate medical courses. The schools formed a consortium to establish common admissions processes and to collaborate on curriculum and staff development. OUTCOMES: ADMISSIONS: Outcomes in admissions included the construction of an entry test and agreement on common application procedures. Structured interviews and measures of prior tertiary performance were adopted in each school with some local variations. Formal structures were put into place to manage the development of the test and admissions procedures. OUTCOMES: CURRICULUM AND STAFF DEVELOPMENT: No formal structures were put into place for curriculum and staff development. While the advantages of common approaches were recognised, it was accepted that it was also important to generate local ownership and commitment to the new courses. Outcomes of educational consortia should not be judged solely by the nature of joint ventures but by the way in which membership of the consortium changes the priorities and practices within the institutions. Examples of the operation of this principle within the three schools include: use of visiting experts to refine and modify approaches to problem-based learning; use of staff from partner institutions to facilitate implementation of the courses; sharing information technology expertise; cooperation in the construction of feedback mechanisms, and sharing advice on fulfilling accreditation requirements. CONCLUSION: The Consortium has had an important impact on Australian medical education. There is a need for further analysis of the two methods of operation of the consortium, formal and informal, and their relation to its overall functioning.

Australia↗
PubMed1999

[Lymph node imaging with ultra-rapid 3D MR angiography].

PURPOSE: A report on observations of lymph node images obtained by gadolinium-enhanced 3D MR angiography (MRA). METHODS: Ultrarapid MRA (TR, TE, FA-5 or 6.4 ms, 1.9 or 2.8 ms, 30-40 degrees) with 0.2 mmol/kg BW Gd-DTPA and 20 ml physiological saline. Start after completion of injection. Single series of the pelvis-thigh as well as head-neck regions by use of a phased array coil with a 1.5 T Magnetom Vision or a 1.0 T Magnetom Harmony (Siemens, Erlangen). We report on lymph node imaging in 4 patients, 2 of whom exhibited benign changes and 2 further metastases. In 1 patient with extensive lymph node metastases of a malignant melanoma, color-Doppler sonography as color-flow angiography (CFA) was used as a comparative method. RESULTS: Lymph node imaging by contrast medium-enhanced ultrarapid 3D MRA apparently resulted from their vessels. Thus, arterially-supplied metastases and inflammatory enlarged lymph nodes were well visualized while those with a.v. shunts or poor vascular supply in tumor necroses were poorly imaged. CONCLUSIONS: Further investigations are required with regard to the visualization of lymph nodes in other parts of the body as well as a possible differentiation between benign and malignant lesions.

Adult↗
PubMed1998

[A multicenter study of diagnostic criteria in ultrasound mammography. Statistical pitfalls and ways out of the data jungle].

This paper demonstrates the statistical processing of data from a multicentric study. Seventy-seven patients with a suspicious, solid breast mass were included in a two-center study, using clinical breast examination, mammography, and ultrasound. The assessment was formalized using a uniform evaluation sheet. The prospective results of the examinations were compared with the histologic report. The degree of interdependence between an examiner's diagnosis and diagnostic criteria used was assessed using the kappa statistics. We found that despite standardized assessment, the criteria used for differential diagnosis were at least partially different. The criteria valid for diagnosis at both centers were whether a mass fitted well into the surrounding tissue or led to destruction or architectural distortion, whether it was fixed to the surrounding tissues, as assessed by sonopalpation maneuvers, and whether it borders were sharp or unsharp.

Artifacts↗
PubMed1998

[Optimal expansion of the multi-link stent. An in vitro study with high resolution roentgen technique].

It has been speculated that high pressure implantation may improve the results of coronary stenting. However, this method bears the risk of persistent dissection and may increase late lumen loss. Presently, there is no consensus about the optimal stent implantation technique with the regard to balloon size and pressure. To elucidate this question an experimental study was performed in a coronary stenosis model. 3.5 mm Multi-Link (ML) stents were implanted in 3.3 mm silicone rubber tubes containing 50% concentric narrowings. Three implantation techniques were applied: 1. The standard technique using the conventional ML delivery system with a compliant balloon (ML-ST). 2. A new deployment method with a high pressure delivery system (ML-HP). 3. "Focal postdilation" using the ARC catheter, which has a special balloon with an inner compliant and an outer non-compliant section (ML-ARC). For comparison, the Palmaz-Schatz stent was implanted by using a high pressure balloon. Stent expansion was imaged by magnification radiography. Minimal lumen diameter within the stent (MLD) and the lumen diameter outside the stent (BD) were measured after dilations with 6, 9, 12, 15, 18, and 21 atm. The relation of the BD to the MLD was used as an index of vessel trauma. The results lead to the following conclusions: 1. A complete apposition to the vessel wall for a balloon/vessel relation of 1.1:1 could not be reached with pressures below 9-15 atm. The increase of the pressure beyond 15 atm resulted only in a minimal additional lumen. 2. Compared to the Palmaz-Schatz stent the recoil of the ML stent was significantly lower. 3. For all three implantation techniques the ML-ARC showed the best results with the maximal dilation of the stenotic vessel-area and the minimal expansion of the vessel outside the stent.

Angioplasty, Balloon, Coronary↗
PubMed1996

[Development of a clinical-radiological CD-ROM database for focal lesions of the liver].

PURPOSE: The development of a CD-ROM database for continuous acquisition and archiving of interesting radiologic cases is described. As a pilot study radiologic images of focal lesions of the liver were collected. METHODS: The database runs on a PC (80486 DX2, 66 MHz, 16 MB RAM), which is connected to the clinic network, a high quality x-ray scanner and a CD-ROM writer. Radiologic images can be inserted into the database either by scanner or by image transfer via network. The database is designed using Access 2.0. Well documented cases were chosen retrospectively, manipulated and archived. RESULTS: 308 images of 12 focal lesions with a capacity of 802 MB were stored on CD-ROM. Per case a storage capacity of 40-75 MB is necessary for image raw material, 15-25 MB are necessary for the postprocessed data. Spatial resolution is 190 dpi (3000 pixel/40 cm). Clinical data, radiological diagnosis coded by modified ACR index and a compressed icon of the images are stored on PC, the image data are stored on CD-ROM. 2.5 hours per case are needed for the complete acquisition, manipulation and archiving procedure, but improved hardware configuration can reduce the time significantly. CONCLUSION: The described database allows continuous archiving of interesting radiologic cases on PC. ACR index is suited for a quick search of a specific combination of radiologic images and diagnosis from different modalities.

Angiography↗
PubMed1994

Oxygenation of mammary tumors as evaluated by ultrasound-guided computerized-pO2-histography.

The average pO2 in breast carcinomas in situ is significantly lower than that in the normal breast tissue. The mean pO2 value for benign breast tumors is significantly higher than that of the breast cancers but lies significantly lower than the corresponding normal breast. No significant differences are found in the mean pO2 values when comparing cancers of different stages and histology. A decrease in the mean pO2 value is measured from the periphery to the center of the breast tumors investigated. The average pO2 values for pre- and postmenopausal patients differ significantly. The described method provides a reliable assessment of tissue pO2 in situ with a minimum of discomfort. Due to extensive inter tumor heterogeneity, prediction of pO2 values for tumors of same stage and same histology is not possible, so that measurement of individual tumor is mandatory for determining therapy response.

Adenofibroma↗
PubMed1993

[Echomorphology of breast cancer].

Breast carcinoma presents with very heterogeneous histopathological pattern. According to the macroscopic growth pattern, we distinguish five different tumor types, each responsible for typical sonographic characteristics: intraductal, circumscribed, stellate, diffuse and intermediate/mixed pattern. The different echographic features of these malignancies will be analysed in relation to histomorphological parameters.

Breast Diseases↗
PubMed1993

[Localization of non-palpable lesions by mammography for preoperative marking and tissue removal].

Mammography screening can increase survival by 15-50%. Minute nonpalpable breast carcinomas can be detected and surgically removed using precise localization techniques. Various techniques are shown, including localization by means of grid mammography and conventional localization with several needles. Stereotactic localization is recommended if the focus cannot be detected by sonography--a procedure now almost always possible if mammography units have the necessary additional equipment. In future it will often become necessary, following a good response to pre-operative chemotherapy, for the tumor, which as a result has become nonpalpable, to be marked prior to surgery (e.g. remaining microcalcifications). This is essential if a representative area of tissue is to be made available for histological examination.

Breast Neoplasms↗
PubMed1992

Aluminium absorption and antacid therapy in infancy.

The aim of this study was to determine whether infants absorb aluminium from antacid therapy. The study was conducted at Torrens House, a service provided by Child and Adolescent Health Services (CAFHS) for feeding and settling problems. Over an 11 week period, all patients receiving antacid therapy were studied. Patients not receiving antacids but of similar age acted as controls. Plasma and urine levels of aluminium were measured. The 15 infants receiving antacids had higher aluminium levels than the 17 controls (plasma 3.3 +/- 2.2 mumol/L vs 1.5 +/- 1.5 mumol/L, P less than 0.01; urine 25.1 +/- 27.6 mumol/L vs 1.1 +/- 1.8 mumol/L, P less than 0.004). The response was variable with 50% of infants receiving antacids recording plasma aluminium levels previously associated with toxicity in patients with renal failure after chronic exposure to aluminium. We conclude that infants absorb aluminium from antacids and suggest that patients receiving have their plasma levels monitored to identify those at possible risk of toxicity.

Aluminum↗
PubMed1991

[The radiologic picture of bronchopulmonary aspergillosis].

The increasing incidence of conditions associated with immune suppression, either as part of the illness or as the result of treatment, makes it necessary to investigate the possibility of fungus infections whenever there are broncho-pulmonary changes. In this respect, aspergillus is a common infection which produces more or less typical radiological changes. It often requires a variety of radiological procedures, including the use of CT and nuclear medicine. The latter can be useful in the allergic form of aspergillosis used for ventilation scintigraphy. The possibility of aspergillosis must be brought to the attention of the clinicians by the radiologist, even in cases that are not entirely typical.

Adult↗