Papers by Alexander Kluge
Zeitschrift für Orthopädie und Unfallchirurgie, 2016
Schlüsselwörter l " mediale unikondyläre Schlittenprothese l " patientenspezifische Instrumente l... more Schlüsselwörter l " mediale unikondyläre Schlittenprothese l " patientenspezifische Instrumente l " Planungsgenauigkeit Key words l " medial unicompartmental knee arthroplasty l " patient-specific instruments l " preoperative planning accuracy Bibliografie
2012 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2012
MRI based nano-and microrobotics show good potential for new targeted therapies tackling e.g. can... more MRI based nano-and microrobotics show good potential for new targeted therapies tackling e.g. cancer. In this paper, a system developed for the propulsion and navigation of small ferromagnetic objects only using clinical MRI systems is evaluated in experiments. The experiments include propulsion of an untethered ferromagnetic object against a pulsatile flow in a pipe system, navigation of an untethered object filled with ferromagnetic nanoparticles around obstacles in a free environment, and the choosing of a branch in a closed flow-less channel system when propelling an untethered ferromagnetic object. The system is found to deal with the tasks efficiently.
Journal of Cardiovascular Electrophysiology, 2005
Percutaneous Pulmonary Vein Stenting. Introduction: Pulmonary vein stenosis (PVS) is a potential ... more Percutaneous Pulmonary Vein Stenting. Introduction: Pulmonary vein stenosis (PVS) is a potential complication of pulmonary vein isolation (PVI) using radiofrequency energy. The aim of our study was the evaluation of the severity and long-term outcome of primary angioplasty and angioplasty with pulmonary vein stenting for PVS. Methods and Results: Twelve patients with 15 PVS (greater than 70% stenosis) were prospectively evaluated. Primary dilation of the stenosis was performed because of clinical symptoms (10 patients) and/or the lung perfusion scans showed a significant perfusion defect (11 patients). Magnetic resonance imaging and lung perfusion scans performed before, directly after, during 3-month, and 6-month follow-up. In the stenting group additional multislice CT-scans directly after, during 6-month, and 12-month follow-up were performed. Within 2 months after primary balloon angioplasty, the PV size parameters were significantly reduced (P < 0.001) with recurrence of PVS in 11 of 15 PVs (73%). Pulmonary vein stenting in 8 patients and 11 PVs resulted in no vein stenosis during 12-month follow-up. Normalization of lung perfusion was noted in 8 of 12 patients. We observed 2 patients with hemoptysis during PV dilation, as severe complications with potential life-threatening character. Conclusion: PVS stenting seems to be superior to balloon angioplasty and effective at least over a period of 12 months in treating acquired PVS after pulmonary vein isolation.
Circulation Research, 2006
Natural adaptation to femoral artery occlusion in animals by collateral artery growth restores on... more Natural adaptation to femoral artery occlusion in animals by collateral artery growth restores only ≈35% of adenosine-recruitable maximal conductance (C max ) probably because initially elevated fluid shear stress (FSS) quickly normalizes. We tested the hypothesis whether this deficit can be mended by artificially increasing FSS or whether anatomical restraints prevent complete restitution. We chronically increased FSS by draining the collateral flow directly into the venous system by a side-to-side anastomosis between the distal stump of the occluded femoral artery and the accompanying vein. After reclosure of the shunt collateral flow was measured at maximal vasodilatation. C max reached 100% already at day 7 and had, after 4 weeks, surpassed (2-fold) the C max of the normal vasculature before occlusion. Expression profiling showed upregulation of members of the Rho-pathway (RhoA, cofilin, focal adhesion kinase, vimentin) and the Rho-antagonist Fasudil markedly inhibited arterioge...
American Journal of Roentgenology, 2006
WEB This is a Web exclusive article. OBJECTIVE. The purpose of this study was to assess the indiv... more WEB This is a Web exclusive article. OBJECTIVE. The purpose of this study was to assess the individual and combined usefulness of MRI techniques in cases of acute pulmonary embolism and to compare the usefulness of these techniques with that of 16-MDCT. SUBJECTS AND METHODS. Sixty-two patients with symptoms indicating acute pulmonary embolism underwent an MRI protocol that progressed from real-time MRI through MR perfusion imaging to MR angiography. The results were compared with those of 16-MDCT, which was the reference standard. Thoracic incidental diagnoses other than pulmonary embolism also were sought with CT and MRI. RESULTS. Pulmonary embolism was diagnosed with CT in 19 patients for totals of 90 lobar, 245 segmental, and 434 subsegmental arteries. On a per-patient basis, the sensitivities of real-time MRI, MR angiography, MR perfusion imaging, and the combined protocol were 85%, 77%, 100%, and 100%, respectively. The specificities were 98%, 100%, 91%, and 93%. The kappa values in a comparison of the MR techniques with CT were 0.89, 0.87, 0.86, and 0.9. On a per-embolus basis, the sensitivities of real-time MRI, MR angiography, and MR perfusion imaging for lobar pulmonary embolism were 79%, 62%, and 100%. The sensitivities for segmental pulmonary embolism were 86%, 83%, and 97%, respectively. MR perfusion imaging had a sensitivity of 93% for subsegmental pulmonary embolism. Eight of nine incidental findings revealed on CT were also subsequently diagnosed with real-time MRI. MRI failed to reveal a case of emphysema. Mean MRI examination time was 9 minutes 56 seconds. CONCLUSION. The combined MR protocol is both reliable and sensitive in comparison with 16-MDCT in the diagnosis of pulmonary embolism. MR perfusion imaging is sensitive for the detection of pulmonary embolism, whereas real-time MR and MR angiography are specific.
Journal of the American College of Cardiology, 2004
Noninvasive Imaging stenosis was 86%. Technical feasibility: Of 74 consecutive studies, 96% were ... more Noninvasive Imaging stenosis was 86%. Technical feasibility: Of 74 consecutive studies, 96% were adequate for qualitative interpretation and 78% for quantitative analysis. Conclusion: The low coefficient of variation in normal volunteer studies suggests quantitative perfusion analysis should differentiate ~15-16% variations in blood flow between myocardial segments. In patients, quantitative dipyridamole stress MRI myocardial perfusion imaging successfully detected four graded levels of perfusion, including defects in reperfused MI that were only 25% below normal.
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Papers by Alexander Kluge