1,721,739 research outputs found
Evaluation techniques for fluid- and valve-related thrombogenic assessment of prosthetic mechanical heart valves
No full textObjektive Bewertung der Spontanmotorik bei gesunden Neugeborenen
No full textConsidering the enormous compound of developmental tests, which on the one hand aim to detect the present stage of a child´s development on the other hand compare it to the same age group and mostly important should enable the observer to make a sincere prediction concerning the prospective developmental status, the observation of spontaneous movements of newborns still represents a small though very important part, since central brain lesions are mostly shown in abnormal spontaneous movements. Up until now, the diagnosis is still based on a visual and thus subjective observation. Trying to find a more objective way to analyse the spontaneous motor activity of newborns the Helmholtz - Intitute developed a tool (ICP Diagnost), which allows the 3- dimensional acquisition of spontaneous movements in newborns, which has been validated and evaluated in this study. Therefore measurements with 11 healthy and 7 affected (infantile cerebral palsy) newborns, regarding the family history, pregnancy, birth and newborn history have been carried out using a standardized setting within the 1./3. and 5. month postpartum. Using a video based 3D motion analysis system (Vicon 370) consisting of 7 infrared cameras with infrared strobes the spontaneous motor activity was recorded. 20 markers placed on predefined body-segments of the infant reflected the infrared light , which was assimilated and converted into 3D movement data. The generated biomechanical model was a full body model. In collaboration with experienced neuropediatrics 35 parameters (velocity, acceleration, range of movement) used during the visual assessment of motor activity and describing the differences between healthy and affected newborns could be extracted from the patient´s 3D movement data. Using the obtained data and a matlab programme (patient classificator) we created 5 evaluation databases and a reliable combination of 8 parameters to match. These databases were used to evaluate the 3 classification systems in ICP Diagnost, regarding sensivity, specificity, predictive value and over all detection rate. In addition detected differences in the spontaneous movements of newborns were evaluated statistically
Kardiovaskuläres Tissue Engineering auf der Basis einer Fibringel-Matrix : Optimierung der Matrix hinsichtlich Isolation, Synthese und mechanischer Festigkeit
No full textIntraaneurysmatische Druckverteilung nach endovaskulärer Therapie von Bauchaortenaneurysmen : Möglichkeiten der Endoleckdetektion mithilfe eines implantierbaren, telemetrischen Drucksensors
No full textThe endovascular repair of abdominal aortic aneurysms (AAA) was first published in 1991 and has gained an increasing acceptance among elective procedures for AAA repair due to the lower peri- and postoperative morbidity. One of the major complications of this therapy is the occurrence of different types of endoleaks. These complication may lead to the necessity of a later reintervention or conversion to a conventional open AAA repair. In the presented study the influence of endoleaks on the intraaneurysmatic pressure was studied by means of a pulsatile in-vitro model of a AAA. Different types and sizes of endoleaks as well as various conditions of lumbar arteries were simulated in multiple systemic pressure ranges. The intraaneurysmatic pressure was measured at different positions within the aneurysm sac by means of wired and telemetric pressure sensors. The aim of this study was also to investigate whether in thrombosed aneurysm sacs compartmentalization leads to pressure differences and whether a preferred localization for pressure measurement exists. The intraaneurysmatic pressure measured at different positions within the aneurysm sac did not indicate any clinically significant differences in pressure increase after opening of an endoleak in all conditions investigated. This was true for the non-thrombosed and thrombosed aneurysm sac. In case of a successful excluded aneurysm the intraaneurysmatic pressure was maximal 18.2 ± 0.8 mmHg in the middle intraaortic pressure range and did not further increase after an increase in systemic pressure. The measured intraaneurysmatic pressure oscillated only in a minimal range at the respective mean pressure. After opening of an endoleak the intraaneurysmatic pressure increased to almost 100% of the systemic pressure, the amplitude of the intraaneurysmatic pressure oscillations increased but did not reach the systemic one. The observed pressure increase was statistically significant (p < 0,0001) in all conditions investigated and was in the lowest applied systemic pressure range about 75 mmHg. This pressure increase could be detected without any problems and clearly distinguished from other disturbing factors. All three investigated endoleak sizes were detectable but not differentiable. In case of a thrombosed aneurysm sac a suspected compartmentalization could not be observed. The relevant conditions of the systematic wire based pressure measurements were exemplarily repeated to evaluate the operability of a newly developed telemetric pressure sensor. The telemetric pressure sensor was implanted into the aneurysm sac and measured pressure readings were compared to the ones simultaneously obtained with wired pressure sensors. It could be shown that the telemetric pressure sensor was able to observe a significant pressure increase (p < 0,0001) in all conditions investigated. The observed differences between the telemetric and wired pressure measurements were insignificant in case of a non thrombosed and thrombosed aneurysm sac. Within an endovascular excluded aneurysm sac it is possible by means of wired as well as of telemetric pressure sensors to detect a clinically relevant pressure increase as well as to verify the successful exclusion of the aneurysm sac. The possibility of a permanent telemetric control of intraaneurysmatic pressure may be helpful to detect clinically relevant endoleaks earlier and subsequently perform a possibly necessary reintervention. In this way the follow-up may be designed less expensive, more convenient as well as with less radiation exposure to the patient
Integrated home monitoring and compliance optimization for patients with mechanical circulatory support devices
No full textVergleichende In-vitro-Testung von Kavafiltern
No full textPURPOSE: In vitro evaluation of six established and two new IVC Filters in order to compare their capture rates.MATERIAL AND METHODS: Six established IVC Filters, the already in vitro tested Cook Celect Filter and a newly developed mesh Filter had to pass several tests in a flow model where they had to prove capture efficiency in vertical and horizontal positions as well as in concentric and eccentric centering. The study was divided into a single- and multi-clot test, where they were exposed to single or multi blood clots of different sizes (3x5, 3x10, 5x10, 5x20, 7x20, 10x24 mm). RESULTS: In the single-clot test the capture rate of the different filters increased significantly (p < 0.001) with increasing clot size. The filter position (horizontal, vertical) did not show any statistical significance (p = 0.3870, p = 0.2241) in either single or multi exposure. In contrast to the filter position, the filter centering (concentric, eccentric) had a statistically significant effect on the capture efficiency in multi exposure (p = 0.0149).CONCLUSION: There are remarkable differences between the tested IVC filters. The Cook Celect filter, the Günther tulip filter and the newly developed mesh filter reached the best results. With larger emboli the Vena Tech LP filter and the OptEase filter obtained equally good capture rates. The Anthéor filter, the Recovery filter and the Titanium Greenfield filter achieved substandard test-results
Einfluss von hyperthermen Oberflächen auf Humanblut
No full textIn order to estimate the impact of exposure of human blood to elevated surface temperatures in blood-conducting systems, detailed data is required. Therefore, titanium alloy housing dummies were immersed in 25 ml heparinized human blood. The dummies were constantly tempered at specific temperatures (37 - 45°C) over 15 minutes as well as one dummy was used as a blank sample and was not tempered. Blood samples were withdrawn for blood parameter analysis and the determination of the plasmatic coagulation cascade. The quantity of adhesions on surfaces were determined by drained weight and underwent histological analysis, likewise one sample was evaluated using FACS (Fluorescent activated Cell Sorter) for further information. With regard to red blood cells, white blood cells, platelets and hematocrit, no statistically significant temperature-dependent difference could be shown at temperatures up to 45°C. Yet, respecting the conditions of the dummies and the blank sample, hemoglobin as well as PF4 (platelet factor 4) seem to be significantly altered by elevated temperatures. Referring to red blood cells, hematocrit, hemoglobin and especially to platelets a significant decrease in terms of cell count could be shown. However, the descent does not appear to be temperature-dependent but correlates with the formation of surface adhesions. Towards 41°C, adhesions seem to increase, whereas temperatures above 43°C show a tendency to a decreasing amount of surface adhesions. Moreover, analyzed by an optical microscope, surface adhesions exposed to higher temperatures demonstrate elevated levels of granulocytes. Also, a temperature-dependent ascending trend towards 43°C could be seen with respect to the amount of activated platelets in FACS analysis.The results of our study suggest that human blood basically tolerates temperatures up to 45°C during the investigated time of 15 minutes. Still, alterations in blood-consistency can be observed. Especially the contact to extrinsic surfaces seems to strongly alter the mentioned parameters. Yet, a critical surface temperature not leading to any undesirable effects on human blood could not be identified within this study
Ex-vivo-Expansion perikardialer Patchstrukturen : zur Frage des Einflusses von zyklischem Stress und laminaren Strömungsbedingungen auf das Ex-vivo-Remodelling perikardialer Patchstrukturen
No full textBACKGROUND: Pericardium is widely used as a patch structure in paediatric cardiovascular heart surgery. However, the major problem still is the restricted availability and level of quality of autologous pericardium. Based on those limiting factors, a new concept has already been tested in a pilot study combining the mesh graft technique of burn surgery with the principles of tissue engineering to expand pericardial tissue ex vivo. The aims of this dissertation were to verify the preliminary result and improve the culture conditions and systems to optimize the synthesis of pericardial neo-tissue. In addition, the characteristics of native and pre-isolated pericardial cells concerning active migration and proliferation in fibrin gel scaffolds should be investigated. METHODS: Perforated porcine pericardial patches filled up with a fibrin-cell-carrier were cultivated in custom-designed bioreactor systems up to 20 days, one group under cyclic stress conditions observing the influences of different frequencies (f equal to or less than 10/min) on tissue-engineered samples and the other under laminar shear stress conditions using cell-seeded and cell-free fibrin gel scaffolds to compare levels of cell migration and proliferation. Extracellular matrix- (ECM) composition was analysed in all samples using routine histological and immunohistochemical techniques. RESULTS: Under stimuli of cyclic stress the neo-tissue synthesis has shown cell necrosis and scaffold dissections while under laminar flow conditions a positive development of ECM-deposition and matrix-remodelling could be observed. Moreover, active migration of pericardial cells into fibrin gel matrices from native tissue could be shown for the first time. The high number of migrated pericardial cells caused an extensive remodelling of fibrin gel matrix by typical ECM-proteins like type I and type III collagen as same as elastin. But in 20 days of cultivation the fibrin gel scaffold has not been entirely replaced by neo-tissue in any perforated patch. CONCLUSIONS: Native pericardial cells represent a promising resource to generate patch structures for pediatric cardiovascular heart surgery. In addition, this concept of ex vivo expansion can be realized without any cell culture. Nevertheless, further investigations have to verify the present results. Optimized culture parameters may increase the mechanical and functional characteristics of expanded pericardial tissue to the point of total replacement of scaffold while prospective animal studies will clarify the possible clinical benefit
Vergleichende In-vitro-Testung von Kavafiltern
No full textPURPOSE: In vitro evaluation of six established and two new IVC Filters in order to compare their capture rates.MATERIAL AND METHODS: Six established IVC Filters, the already in vitro tested Cook Celect Filter and a newly developed mesh Filter had to pass several tests in a flow model where they had to prove capture efficiency in vertical and horizontal positions as well as in concentric and eccentric centering. The study was divided into a single- and multi-clot test, where they were exposed to single or multi blood clots of different sizes (3x5, 3x10, 5x10, 5x20, 7x20, 10x24 mm). RESULTS: In the single-clot test the capture rate of the different filters increased significantly (p < 0.001) with increasing clot size. The filter position (horizontal, vertical) did not show any statistical significance (p = 0.3870, p = 0.2241) in either single or multi exposure. In contrast to the filter position, the filter centering (concentric, eccentric) had a statistically significant effect on the capture efficiency in multi exposure (p = 0.0149).CONCLUSION: There are remarkable differences between the tested IVC filters. The Cook Celect filter, the Günther tulip filter and the newly developed mesh filter reached the best results. With larger emboli the Vena Tech LP filter and the OptEase filter obtained equally good capture rates. The Anthéor filter, the Recovery filter and the Titanium Greenfield filter achieved substandard test-results
Bedeutung des Volume Rendering in der Diagnostik der Koronargefäße mittels Mehrschichtspiral-CT
No full textThe intention of this study is on the one hand to compare the measurement precision in determining vessel diameters of the 3D-volume rendering techique (3D-VRT) to quantitative coronary angiography (QCA) and on the other hand to challenge the diagnostic value of 3D-VRT. For 53 patients (42m, 11f), retrospectively ECG-gated MSCT of the heart was performed as well as quantitative X-ray coronary angiography. The standardized examination protocol included a collimation of 4x1mm,a tube voltage of 120kV with an effective tube current of 400 mAs and a tube rotation time of 500ms. An effective slice thickness of 1.25mm and a reconstruction increment of 0.6mm were chosen for image reconstruction. During examination 120ml of a non-ionic contrast material were administered by injection in a cubital vein with a flow-rate of 2.5ml/s. Using the Adaptive-Cardio-Volume algorithm, 3D-VR image series were calculated every 10% (30-80%) of the RR interval. For further analysis the images were transferred to an external workstation. Using a 3D-VR technique (512x512 matrix), 4770 coronary artery segments (AHA-classification) were evaluated for their visibility to classify them in a 4-point grading scale. In a second step, the diameter of each coronary artery of 50 patients in the individually best reconstruction was measured at the origin as well as 1cm, 3cm and 5cm distally. For each measurement from the 3D-VRT image the minimum, maximum and mean diameters were determined and compared with QCA- diameters using the Bland-Altman method. Finally, coronary artery stenosis were detected using both techniques. Further more, the diameter of 34 stenoses, detected on QCA, was measured as well as the vessel diameter 1cm proximal and distal of the stenosis. The measurement results of the 3D-VRT were compared to QCA results. 1851 (38.8%) of 4770 coronary artery segments were assessable (score 2-3), 1566 (32.84%) were scored with 1 point, meaning visible but not assessable and 1353 (28.36%) were not visible. Image reconstruction at 70% RR-interval shows for 13 coronary artery segments the best visibility with 51.95% assessable segments (min: 15.09%, max: 92.45%). The proximal segments were more often assessable when compared to the distal segments. Spearman-rank- order-correlation between visibility score and average heart rate or range of heart rate of each patient does not reveal any dependency (min: -0.3661, max: -0.5536 or min: 0.0156, max: 0.1320). Using the Bland-Altman method the difference between vessel diameter measured in 3D-VRT and QCA was evaluated in 581 measuring points (97 for quantification of coronary artery stenoses). The comparison of the maximum diameter of 3D-VRT and QCA shows the lowest differences (min: -0.007mm, max: -0.447mm) with a mean variance of 0.2552mm (min: -0.007, max: 2.184mm). Pearson correlation between diameter difference and average heart rate does not reveal any correlation (min: 0.0022, max: 0.2495). Coronary artery stenoses were detected with a sensitivity of 85% and a specificity of 98.26%. When compared to QCA, the ability of 3D-VRT to quantitatively assess coronary artery diameters and coronary artery stenoses is insufficient for clinical purposes. The good visibility and assessment of proximal vessel segments give reason to expect that current problems can be overcome in the near future
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