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Biomedical subjects

M L Bahner

Publications and source records attributed to M L Bahner.

29 records · Page 2Linked to original sources
PubMed1998

Colour Doppler sonography in breast tumours: an update.

The aim of our study was to reassess the diagnostic performance of image-based, computer-assisted colour Doppler quantification under routine conditions. We used a computer-assisted protocol that quantitatively characterises a colour Doppler image by the relative amount of colour pixels (colour pixel density, CPD) and the colour hues (numerically expressed by the mean colour value, MCV) in 44 patients with breast carcinoma and 49 patients with benign breast lesions. Studies were carried out over two periods by two examiners, subsequently in charge of breast ultrasound. During the first period, the sensitivity of the MCV was 92 %, the specificity 75 %; the sensitivity of the CPD was 80 %, the specificity 81 %. During the second period, the sensitivity of the MCV was 58 %, the specificity 77 %; the sensitivity of the CPD was 68 %, the specificity 71 %. Despite measures to create uniform examination conditions, the diagnostic performance of this method may decline under routine conditions.

Adult↗
PubMed1998

Spiral CT vs incremental CT: is spiral CT superior in imaging of the brain?

The aim of this study was to evaluate image quality of spiral CT of the brain as compared with incremental CT using identical scanning parameters. Incremental or spiral cranial CT was performed on 46 consecutive, randomized patients with non-traumatic disease of the brain on a Siemens (Erlangen, Germany) Somatom Plus 4. Evaluation was done in a randomized blinded way by two experienced radiologists. Different anatomical structures, image noise, and artifacts were scaled 1 (bad) to 4 (very good). Statistical analysis was done using the F-test of variance for partial sums of squares as well as Student's t-test. Incremental CT was superior to spiral CT for evaluation of the internal capsule, supratentorial artifacts, gray/white matter differentiation, and image noise. No statistically significant differences were seen for evaluation of the pons, infratentorial artifacts, and eye muscles. With identical scanning parameters incremental CT is superior to spiral CT in the assessment of small, complex structures in a low-contrast setting. No differences are seen for larger structures or small structures in a medium-contrast range. Artifacts localized close to the skull in spiral CT can easily mimic hemorrhage in traumatized patients. Spiral CT should therefore only be used for CT angiography and if 3D reconstructions are needed.

Artifacts↗
PubMed1998

Technical aspects of virtual liver resection planning.

Operability of a liver tumor is depending on its three dimensional relation to the intrahepatic vascular trees which define autonomously functioning liver (sub-)segments. Precise operation planning is complicated by anatomic variability, distortion of the vascular trees by the tumor or preceding liver resections. Because of the missing possibility to track the deformation of the liver during the operation an integration of the resection planning system into an intra-operative navigation system is not feasible. So the main task of an operation planning system in this domain is a quantifiable patient selection by exact prediction of post-operative liver function and a quantifiable resection proposal. The system quantifies the organ structures and resection volumes by means of absolute and relative values. It defines resection planes depending on security margins and the vascular trees and presents the data in visualized form as a 3D movie. The new 3D operation planning system offers quantifiable liver resection proposals based on individualized liver anatomy. The results are visualized in digital movies as well as in quantitative reports.

Humans↗
PubMed1997

[Requirements for a teleradiology system. Experiences with the MEDICUS-2 field test].

During the Medicus field test we gained experience using the teleradiology system for almost daily teleconferences between a radiology department and clinics for internal medicine, urology, and gynecology. The existing system has a high degree of functionality. The full 12-bit data format is available using the DICOM protocol. A data security concept is implemented, ensuring data integrity, privacy and authentication of communication partners. This concept covers the areas of organization, technique, user training, and software implementation. A future system should be a general purpose radiology workstation covering viewing functionality, image manipulation, and digital archive access. Dedicated teleradiology features have to be a part. Specialized evaluation software, e.g. for dynamic MRI, should be integratable in a modular way. For data exchange with other systems and for the synchronization of teleconference sessions, the protocols should be independent of the network standard used (ISDN, Ethernet, ATM) and based on the DICOM protocol. Extensions of the existing standard are therefore necessary. Besides future technical developments, reimbursement for teleradiology must be accomplished.

Computer Communication Networks↗
PubMed1997

Prognostic significance of color Doppler findings in head and neck tumors.

We examined whether or not the degree of tumor vascularity in lymph node metastases as depicted by color Doppler is associated with a patient's prognosis. Cervical lymph node metastases in 25 patients with head and neck cancer were examined before combined accelerated radiotherapy and chemotherapy. The findings were quantified using a computer-assisted protocol that quantitatively describes color Doppler images by the relative color pixel density (CPD) and the color hues, which are numerically expressed by the mean color value (MCV). We found that, in the patient group with a CPD below median, the median survival was 958 days and, in the group with a higher CPD, it was 423 days (p = 0.05). The time to detection of distant metastases was 18 months with a low CPD, and 6 months with a high CPD (p = 0.05). However, the time to local or nodal progression was not different between the groups. The MCV was not correlated with prognostic data. These results indicate that, in patients with metastatic head and neck cancer, highly vascularized lymph nodes detected with color Doppler sonography may indicate a shorter survival and earlier occurrence of distant metastases.

Blood Flow Velocity↗
PubMed1987

Comparison of steady state serum theophylline concentrations in healthy volunteers after dosing with Euphyllin retard and PulmiDur.

In a randomized cross-over study, theophylline serum levels were compared over a 12-h dosing interval after repeated administration of Euphyllin retard and PulmiDur to 18 healthy male volunteers. Although both preparations are sustained-release formulations they differ in the systems used and in the state of hydration of theophylline. Two tablets each of Euphyllin retard or one tablet PulmiDur plus one tablet PulmiDur forte were administered in an identical dosing scheme always before food intake. The mean value curves of theophylline serum levels obtained at steady state clearly demonstrate the marked sustained-release properties of both preparations. The relative bioavailability of Euphyllin retard vs. PulmiDur calculated from the individual ratios of the dose adjusted AUCs was 96(83-111)%, results being given as geometric mean and 95% confidence limits. Hence Euphyllin retard is equivalent to PulmiDur with regard to the extent of absorption.

Adult↗
PubMedDate not supplied

Virtual planning of liver resections: image processing, visualization and volumetric evaluation.

Operability of a liver tumor depends on its three dimensional relation to the intrahepatic vascular trees as well as the volume ratio of healthy to tumorous tissue. Precise operation planning is complicated by anatomic variability and distortion of the vascular trees by the tumor or preceding liver resections. We have developed a computer based 3D virtual operation planning system which is ready to go in routine use. The main task of a system in this domain is a quantifiable patient selection by exact prediction of post-operative liver function. It provides the means to measure absolute and relative volumes of the organ structures and resected parenchyma. Another important step in the pre-operative phase is to visualize the relation between the tumor, the liver and the vessel trees for each patient. The new 3D operation planning system offers quantifiable liver resection proposals based on individualized liver anatomy. The results are presented as 3D movies or as interactive visualizations as well as in quantitative reports.

Algorithms↗