Biomedical subjects

U Boenick

Publications and source records attributed to U Boenick.

At least 19 recordsLinked to original sources

PubMed2005

[A novel method for patient-oriented assignment of wheelchair cushions based on standardized laboratory testing procedures].

A wheelchair seat cushion represents the interface between the wheelchair and the wheelchair driver and has to manage the force transmission and the stabilization between both of them. An additional very important requirement is the prevention of pressure ulcers by pressure relief and the transfer of humidity and heat away from the patient. The allocation of a cushion to the patient happens normally on the base of a subjective description of the cushion without any transparent decision rules. Consequently the quality of this procedure could be improved by a better description of the cushion, based on standardized laboratory tests and by the development of decision tools helping to identify the main efforts of the user. This article describes a procedure that allows the allocation of wheelchair seat cushions based on the characteristic of cushions from standardized laboratory tests and on the brief description of the user. Additionally the existing principles for wheelchair cushions are listed, described and compared. The possibilities to develop structured decision tools for wheelchair cushions are discussed.

Decision Support Techniques↗

PubMed2003

[Drive principles of a triaxial physiological hip joint simulator for wear testing of hip endoprostheses].

The long-term performance of hip joint replacements is a major criterion for quality assessment. Aseptic loosening as a result of wear has a considerable impact on the long-term stability of the prosthesis. Constant improvements in hip joint endoprostheses necessitate the use of hip joint simulator to evaluate and assess the suitability of newly developed materials. In the present paper, a triaxial physiological hip joint simulator is presented, and detailed information provided, on the applied control concepts, adaptation of various hard- and software systems and the accuracy of the kinematic and force parameters achievable.

Biomechanical Phenomena↗

PubMed2002

[Personal emergency call system based on human vital and system technical parameters in a Smart Home environment].

Progress in microtechnology and radio transmission technology has enabled the development of highly reliable emergency-call systems. The present article describes systems that have been specially designed to improve the safety and independence of handicapped and elderly persons living at home. For such persons immediate help in an emergency situation is of crucial importance. The technical state of the art of emergency-call systems specially developed for use by the elderly, is briefly discussed, in particular the well-known radio emergency-call button, with the aid of which an alarm can be activated manually. This system, however, does not offer adequate safety in all emergency situations. Alternative or complementary systems designed to automatically trigger an alarm on the basis of the recording and evaluation of so-called vital parameters, are therefore proposed. In addition, in a smart-home environment with networked devices, further parameters--so-called environment parameters can be used. It is found that the identification of an emergency situation becomes more reliable as the number of parameters employed increases.

Aged↗

PubMed2002

[Evaluation of measurement systems for determining therapeutic effectiveness of anti-decubitus ulcer devices].

Interface pressure measurement is today a most used technique for laboratory evaluation of support surfaces in prevention of pressure sores. This article describes the results of an experimental comparative evaluation of four modern pressure mapping systems (Tekscan, Xsensor, Novel and FSA) using a special loading device. The tests generated data on numerical accuracy, linearity and hysteresis. The results show that the accuracy of pressure mapping systems is still limited and results obtained from different systems can not be directly compared.

Biomechanical Phenomena↗

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↗

PubMed2000

Ultrasonic surfactant nebulization with different exciting frequencies.

Intratracheal bolus instillation of natural lung surfactant is the treatment of choice in neonatal respiratory distress syndrome and an increasing part in adults' therapy. For reasons of hemodynamics, surfactant distribution and efficiency the application mode should be improved. Nebulization seems to have some advantages but its technical realization is difficult. The aim of the present study was to investigate if ultrasonic nebulization with exciting frequencies higher than 2.8 MHz can improve the efficiency of surfactant nebulization without changing the surface-active properties of the material. Exciting frequencies of 1.7, 3.3 and 4.0 MHz were used to produce a surfactant aerosol. The phospholipid content in the liquefied aerosol and particle size distinctly dropped with higher frequencies. The surface activity was not altered in the produced aerosol and neither in the surfactant remaining in the nebulizer. Although possible, ultrasonic nebulization of surfactant suspensions is ineffective because of a striking decrease in phospholipid content.

Aerosols↗

PubMed2000

[Multifunctional testing of PTCA balloon catheters].

New in vitro measuring methods for balloon catheters used for percutaneous transluminal coronary angioplasty (PTCA) and their verification in a complex test device are presented. This system can mimic all relevant application situations. The central element of the test device is a coronary vessel model matching the physiological situation in terms of geometrical structure and frictional properties. Reactive force sensors are used to measure the application-relevant forces exerted by the catheter on the model vessel walls and accessories, such as guide wire and guiding catheter. To generate a kink-free advancement of the catheter and permit measurement of the active forces, an alternating drive unit has been specially developed. The testing and application of the newly developed methods revealed statistically significant differences between various types of catheter. The test device closes a gap between complex but subjective clinical tests, and individual objective, but application-removed in vitro test setups for PTCA catheters. While the initial prototype had shortcomings with regard to the reproducibility of measurements, successor systems developed for industrial use are now in production. The properties of these measuring systems developed for the benefit of manufacturer and reprocessor of PTCA catheters are discussed.

Angioplasty, Balloon, Coronary↗

PubMed2000

[Reuse of instruments for minimal invasive surgery--status and prospects].

The development of instruments for minimal invasive surgery (MIS) is moving in the direction of the miniaturization of mechanical components, a combination of multiple functions in a single instrument, and the introduction of new techniques, in particular those reducing bleeding and thermal damage when cutting blood vessels. These tendencies have consequences for the reprocessability of the instruments, usually making reprocessing more difficult. In particular cleaning--the removal of contaminations from tiny lumina, joints, etc., is highly demanding. In addition, proof of successful cleaning is difficult, and no standardised method of doing this in practice is currently available. An overview of the problems associated with the reprocessing of instruments for minimal invasive surgery is given, and a numbers of possible solutions are discussed.

Endoscopes↗

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

[Comparison of internal fixation methods for the symphysis in multi-directional dynamic gait simulation].

For the stabilization of the ruptured pubic symphysis, rigid forms of fixation such as plate osteosynthesis and flexible fixations such as wire loops or PDS banding have been recommended. All methods have only been tested by static unidirectional loading until failure of the system. By this experimental arrangement Ecke and Hofmann found comparable results for flexible and rigid methods of internal stabilization of the pubic symphysis. They preferred flexible methods to maintain mobility of the symphysis and to prevent symphyseal fusion. We tested dynamic compression plate osteosynthesis, reconstruction plate osteosynthesis, wire loops and PDS banding for internal fixation of injured pubic symphysis in a dynamic multidirectional experimental arrangement simulating gait conditions. The specimens were loaded with 85 N in vertical (y-) direction and 34 N in sagittal (z-) direction, which represent 50% of the forces acting at the pubic symphysis during walking and with a frequency of 1.5 Hz over 55,500 loads simulating the conditions over a 6-week mobilization period. Loading with 100% of the acting forces (corresponding to full weight bearing mobilization) led to early failure of the system. Our experimental analysis showed that neither wire loops nor PDS banding is able to stabilize the ruptured pubic symphysis, even immediately after fixation before loading. During the tests instability increased until failure of the system due to cutting of the bone or breaking of the wires or PDS banding. Success of plate osteosynthesis was dependent on the initial stability of the fixation. Overwinding of the screws, as in osteoporotic bone, lead to increasing loosening during repeated loading, whereas primary stable fixation of the screws was almost completely maintained during the test. In consequence, neither wire loops nor PDS banding should be used for stabilization of injured pubic symphysis if early mobilization with partial weight bearing is desired. Plate osteosynthesis (DC or reconstruction plate) tolerates early half weight bearing in patients with "open-book" injury only if safe screw fixation is guaranteed.

Biomechanical Phenomena↗

PubMed1998

Influence of different trocar tips on abdominal wall penetration during laparoscopy.

Most trocars currently used to place a cannula through the abdominal wall have a conical or pyramidal tip. Because the risk of inadvertent injury along with removal of the cannula is probably related to (a) the force needed to traverse the abdominal wall, (b) the force needed to remove the trocar, and (c) the defect in the abdominal wall, the optimum configuration of the penetrating tip should be determined. The entry force needed to perforate the abdominal wall, the removal force necessary to remove the trocar, and the defect in the abdominal wall were measured in a porcine model under standardized conditions (general anesthesia, 12 mmHg pneumoperitoneum). Nineteen trocars (six disposable, seven reusable, six custom-made) have been tested. They were divided into six groups according to the shape of the tip (conical, pyramidal, or a combination). The entry force (F = 25.6, p < 0.0001) and the removal force (F = 5.1, p < 0.01) were related to the shape of the tip. Conical tips needed a higher force than purely pyramidal tips. The abdominal defect was also different between groups (F = 6.5, p < 0. 001). The trocar with a pyramidal shape caused a greater defect than conical tips. The defect in the abdominal wall was inversely related to the entry force (r = -0.55, p < 0.001) and to the removal force (r = -0.57, p < 0.001). There is not an optimum configuration of a simple push-through trocar with a low entry force and a high removal force. Some kind of a conical tip is recommended for insertion of trocars under direct view.

Abdominal Muscles↗

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↗

PubMed1998