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Biomedical subjects

O Wendt

Publications and source records attributed to O Wendt.

12 recordsLinked to original sources
PubMed2001

[Cutting speeds and success of biopsy with different punch biopsy instruments].

PURPOSE: The goal of our investigations was the verification of the relationship between the reachable cutting speed and the biopsy success for different large-core needle biopsy devices in dependence of the cutting depth as well as different kinds of tissue. METHODS: We measured the dynamic cutting properties of five large-core needle devices with moveable outer needles in air and different tissues. An incremental stripe had been attached on to the outer needle and was moved through a photooptical sensor during the cutting phase. For the valuation of the biopsy success we compared the absolute weight respectively the volume of the tissue probes as well as the relative weight in relation to the size of the sample chambers within the inner trocars. RESULTS: A clear correlation between the cutting speed, the tissue properties and the biopsy success had been registered, especially for more solid tissues. CONCLUSIONS: For a successful large-core needle biopsy a cutting speed of 8 to 12 metres per second is essential. To compensate slower needle movements high quality requirements for the surface, geometry and edge have to be fulfilled.

Animals↗
PubMed1999

1H and 31P NMR characterisation of a double breast coil for spectroscopic measurements and imaging.

For the first time a double turn breast coil has been described which can be used for 1H imaging, 1H spectroscopy and 31P spectroscopy. The paper describes basic technical features of the coil, coil design, B1 field/excitation field distribution for 1H and 31P, sensitivity, and feasibility for 31P spectroscopic in vivo studies. The main advantage of the double frequency tuneable coil is that 1H imaging for tumor localization and 31P spectroscopy for response control can be done without an additional repositioning of the patient.

Breast Neoplasms↗
PubMed1998

[Effects of para- and diamagnetic materials in a 1.5 Tesla high field magnetic resonance tomography system].

This article shows the results of an experimental investigation of the interference by paramagnetic and diamagnetic materials on imaging in a closed 1.5 Tesla high field magnetic resonance imaging system (MRI). For different types of sequences (SE, GE, EPI) the effects of metal and non-metal profiles in producing artefacts were investigated. A phantom (plastic trunk) filled with Gd-Mn-solution was used for representation of the artefacts. The materials analysed were placed parallel to the phantom at predetermined distances. The images were obtained in transverse and sagittal planes and analysed with respect to the resulting artefacts. The results show that aluminum and polymer profiles produce the weakest artefacts, even when the material is positioned close to the phantom. A comparison of the sequence types shows that the SE-sequence has a low sensitivity to artefacts, despite the great profile variation in size and shape. The SE-sequence accordingly showed a higher imaging stability as compared with the GE- and EPI-sequences. Steel and copper produced the strongest artefacts. The examination was begun after an intensive study of the literature (Internet, Medline, Meditec). So far have been few publications on this subject.

Artifacts↗
PubMed1982

[Isolated Crohn disease attack of the stomach--differential diagnostic and therapeutic problems].

There are about 15-30 patients reported in the literature, who suffered from well established, isolated Crohn's disease of the stomach. Another case is reported here, who had gastrectomy, since a diagnosis of gastric carcinoma had been made before and during surgery. When histological findings are negative, very extensive diagnostic procedures have to be performed in order to exclude this entity and to avoid useless gastric surgery. A clearcut recommendation as to surgery in cases of stenosis of the pyloric region cannot be given; the experience from the case described however would tend to favour treatment by gastrectomy.

Crohn Disease↗
PubMedDate not supplied

The effects of the use of piezoelectric motors in a 1.5-Tesla high-field magnetic resonance imaging system (MRI).

PURPOSE: This paper presents the results of an experimental investigation with two different rotatory piezomotors in a closed 1.5 Tesla high-field MRI. The focus of the investigation was on testing the functionality of these motors within the MRI and to determining the image interference they caused. MATERIALS AND METHODS: To obtain a differentiated estimate of the interference the motors were tested in both the passive (turned off, i.e. without current flow) and active (turned on, i.e. with current flow) state during MRI scanning. Three different types of sequences were used for the test: Spin-Echo (SE), Gradient-Echo (GE) and Echo-Planar Imaging (EPI). A plastic container filled with a gadolinium-manganese solution was used for representation of the artefacts. The motors investigated were placed parallel to the container at predetermined distances during the experiment. RESULTS AND CONCLUSIONS: The results show that the motors investigated suffered no functional limitations in the magnetic field of the MRI but, depending on the type of motor, the measurement distance and the state of the motor, the motors had different effects on the sequence images. A motor in the off-state placed immediately next to the object to be measured mainly causes artefacts because of its material properties. If, on the other hand, the piezomotor is in the on-state images with strong noise result when the motor is immediately next to the object being measured. The images regain their normal quality when the motor is approximately at a distance of 1 m from the object being investigated. Driving the motor inside the MRI, therefore, is only to be recommended during the pauses in scanning: this delivers artefact-free images if minimal, motor-specific distances are kept to. With regard to the three different types of sequences it was determined that the SE sequence was the least sensitive and the EPI sequence the most sensitive to disturbance. The GE sequence showed only minimal differences to the SE sequence with regard to signal-to-noise ratios. Since it requires considerably shorter scan-times it can be considered to be the most effective type of sequence under these conditions.

Artifacts↗