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T Schmitz-Rode

Publications and source records attributed to T Schmitz-Rode.

At least 19 recordsLinked to original sources
PubMed2006

[First results with catheter and magnetically guided and detached polymerized ferromagnetic particle filaments and heat-induced particle release using the Stereotaxis Niobe system].

PURPOSE: To develop a new technique for intravascular guidance and the release of magnetized ferromagnetic nanoparticles using a polymerized filament by means of an external magnetic field. MATERIALS AND METHODS: Ferromagnetic nanoscaled beads were embedded in temperature-sensitive gels to form filaments after polymerization. Deflection of the filaments was assessed in a Stereotaxis Niobe magnetic navigation system (MNS) in comparison with dedicated guide wires. The curvature was measured as a surrogate parameter for deflection. In combination with commercially available catheters, the filaments were navigated in a perfused aneurysmatic vessel model and a perfused branched vessel model under the influence of two permanent magnets of the Niobe MNS. The magnetic field vector was varied in all three dimensions. After positioning, the magnetic colloid-containing filaments were exposed to an electromagnetic field of 45 kA/m, 200 kHz for a period of 5 minutes for non-invasive heating. RESULTS: The filaments showed superior deflectability compared to the dedicated guide wires (p = 0.0091). The curvature was 0.54 +/- 0.12 mm(-1) for the filaments and 0.33 +/- 0.21 mm(-1) for the guide wires. In combination with angiography catheters, magnetic guidance and accumulation of specially designed filaments were possible in the perfused vessel model. Inductive heating allowed non-invasive disintegration and releasing of the nanoparticles in all filaments. CONCLUSION: This feasibility study shows that magnetic guidance and targeting of a specially designed magnetic colloid-containing filament and subsequent disintegration are feasible. This technique offers the potential for controlled local drug release.

Aneurysm↗
PubMed2006

Impact of pressure recovery in the evaluation of the Omnicarbon tilting disc valve.

BACKGROUND: Pressure recovery is not taken into account when calculating trans-prosthetic gradients after mechanical valve replacement using Doppler echocardiography. This may lead to underestimation of valvular performance. METHODS: Simultaneous measurement of Doppler and direct trans-prosthetic gradients was performed in a circulatory mock loop simulator with physiologic parameters at different heart rates and cardiac outputs for small-sized aortic Omnicarbon tilting disc valves (19 - 21 mm). RESULTS: In all adjustments the Doppler gradient significantly overestimated the net transvalvular gradient. The amount of pressure recovery averaged 59.3 %. CONCLUSIONS: Doppler echocardiography does not allow for pressure recovery, which is a significant phenomenon in the hemodynamic function of the Omnicarbon tilting disc valve. Valve performance is much better than expected from Doppler gradients.

Aortic Valve↗
PubMed2006

CFD simulation of a novel bileaflet mechanical heart valve prosthesis: an estimation of the Venturi passage formed by the leaflets.

The aim of this study was to validate the flow characteristics of the novel Helmholtz-Institute Aachen Bileaflet (HIA-BL) heart valve prosthesis. The curved leaflets of the HIA-BL valve form a Venturi passage between the leaflets at peak systole. By narrowing the cross section the flow accelerates and the static pressure at the central passage decreases according to the Venturi effect. The low-pressure zone between the leaflets is expected to stabilize the leaflets in fully open position at peak systole. To investigate the Venturi passage, the flow fields of two valve geometries were investigated by CFD (Computational Fluid Dynamics): one geometry exhibits curved leaflets resulting in a Venturi passage; the other geometry features straight leaflets. The flow profiles, pressure distribution and resulting torque of both passages were compared and investigated. Although flow profiles downstream of both valves were similar, the flow passages between the leaflets were different for the investigated leaflet geometries. The straight leaflet passage showed a large boundary layer separation zone near the leaflets and the lowest pressure at the leading edge of the leaflet. The Venturi passage showed a reduction of the boundary layer separation zones and the lowest pressure between the leaflets could be found in the narrowest flow cross section of the Venturi passage. Additionally, the resulting torque showed that the Venturi passage produced an opening momentum. The results demonstrate that the Venturi passage stabilizes the leaflets in open position at peak systole.

Blood Flow Velocity↗
PubMed2005

Treatment of wide-necked aneurysms with balloon-expandable polyurethane-covered stentgrafts: experience in an animal model.

OBJECTIVE: Endovascular treatment of intracranial wide-necked aneurysms employing stentgrafts might constitute a promising alternative to established neurosurgical or endovascular treatment options. However, there is uncertainity concerning long-term vessel patency and biocompatibility of the covering material used for these stentgrafts. The objective of our study was, therefore, to evaluate in an animal model of wide necked aneurysms, which changes within the parent vessel wall are present after stentgraft placement using polyurethane as the covering material. METHODS: Wide-necked aneurysms were created in rabbits by distal ligation and intraluminal incubation of the right common carotid artery with elastase. All 10 animals were treated with polyurethane covered stentgrafts. Angiography and histological analyses were performed including immunohistochemical investigations for estimating the proliferation of the intima and possible inflammatory infiltration of the vessel wall after one (n = 5) and three months (n = 5) observation. RESULTS: Stentgrafts led to a complete and stable aneurysm occlusion in all but one animal in which the stent was initially misplaced. In one animal, the stentgraft was completely occluded as visible both at angiography and on histological examination. Here, old thrombus was found within the stent although the animal was on antiplatelet therapy. The other stentgrafts remained patent and demonstrated only minimal proliferative carrier vessel wall changes and no in-stent stenosis. CONCLUSIONS: In previous animal models using Dacron covered stentgrafts, a poor short term patency rate due to the limited biocompatibility was found. We found, that Polyurethane seemed to have less adverse effects upon the vessel wall. However, a longer follow-up period is necessary to exclude delayed stenosis of the parent vessels. Stentgrafts may, therefore, play a role in broad based aneurysms, dissecting aneurysms or pseudoaneurysms, however, vessel sacrifice using permanent balloon occlusion may be a safer and better established alternative compared to the use of stentgrafts.

Aneurysm↗
PubMed2005

New optional IVC filter for percutaneous retrieval--in vitro evaluation of embolus capturing efficiency.

PURPOSE: In-vitro evaluation of a new caval filter (Cook Celect Filter) developed for delayed percutaneous retrieval in comparison to the Gunther Tulip filter. MATERIALS AND METHODS: The new Celect filter is constructed on the basis of the Tulip filter and consists of 4 primary anchoring legs and additional 8 thinner secondary wires to stabilize the filter and to guarantee adequate filtering efficiency. The filtering wires are of the same amount and equal distribution as the filtering wires of the Tulip filter. The secondary wires are arranged in such a way that percutaneous filter retrieval should be possible even if the wires are incorporated into the caval wall. In a flow model (tube size ø15-, ø22- and ø30 mm), the filter was exposed to single and multiple emboli (blood clots) of different sizes (3 x 5, 3 x 10, 5 x 10, 3 x 20, 5 x 20, 7 x 10, 7 x 20 to 10 x 24 mm) to analyse the embolus capturing efficiency under different conditions including eccentric and concentric, horizontal and vertical positions in comparison to the Tulip filter. All testing was carried out in SPSS analytic software; statistical significance was assumed for p-values < 0.05. RESULTS: The in-vitro embolus capturing efficiency of the Celect filter proved to be equivalent to the Tulip filter. In the single-embolus test, 91.6 % of the clots were captured by the Celect filter and 87.2 % by the Tulip filter (p = 0.042). Large clots ranging from 7 x 10 to 10 x 24 mm were captured in all cases, whereas the capture rates for the 3 x 5-mm and 3 x 10-mm clots were lower. The filters captured significantly more clots in the concentric than in the eccentric location. There was no significant difference between the overall capture rates of the two filters in the multi-clot test (72.2 % vs. 75.1 %), which showed deterioration of filter function during multiple clot exposure. With the 15-mm tube, the Celect filter had a significantly higher capture rate than the Tulip filter, whereas it was lower with the ø30-mm tube. There was no significant difference between the filters in a ø22-mm tube. The pressure gradient across the filters when exposed to blood clots ranged from 4.9 - 7.4 mm Hg for the Celect filter and 5.7 - 6.8 mm Hg for the Tulip filter in the single-embolus testing. There was no significant difference in the multi-clot tests. CONCLUSION: The new Celect filter showed similar in-vitro capture properties as the Gunther Tulip filter and deserves further in-vivo testing.

Blood Flow Velocity↗
PubMed2004

Semicircular canal dehiscence: comparison of T2-weighted turbo spin-echo MRI and CT.

We assessed the value of MRI for delineation of dehiscence of the superior or posterior semicircular canal, as compared with CT, the current standard study for this entity. We reviewed heavily T2-weighted fast spin-echo images and high-resolution CT of the temporal bones of 185 patients independently semicircular canal dehiscence and its extent. In 30 patients (19 men, 11 women) we identified dehiscence of the bone over the superior and/or posterior semicircular canal on MRI. In 27 of these cases CT also showed circumscribed bone defects. In one patient dehiscence of the superior semicircular canal was initially overlooked on MRI, but seen on CT. MRI imaging thus had a sensitivity of 96% and specificity of 98%. Knowledge of the appearances of this entity on MRI may contribute to early diagnosis in patients with vertigo due to semicircular canal dehiscence.

Adult↗
PubMed2004

[Fluoroscopically guided fallopian tube recanalization with a simplified set of instruments].

PURPOSE: Fluoroscopically guided transcervical fallopian tube recanalization is recognized as an important step in the workup of female infertility. In the present study, a simplified set of recanalization instruments was tested. MATERIALS AND METHODS: Forty-two women with infertility and sonographically confirmed or suspected uni- or bilateral tubal occlusion were examined. After vaginal placement of a plastic speculum and fixation of a tenaculum, a 4F glide catheter with a 0.89 mm glidewire was advanced transcervically. After documentation of tubal occlusion by hysterosalpingography, the uterotubal junction was catheterized with the same instruments. Under fluoroscopic guidance, the glidewire was negotiated beyond the intramural portion of the tube. Selective salpingography documented the outcome of the recanalization. RESULTS: Hysterosalpingography confirmed tubal occlusions in 26 of 42 patients (in 12 cases unilateral and in 14 cases bilateral). Fallopian tube recanalization was successful in 23 of 26 patients (technical success rate of 88 %). The resulting fertility rate was 30 % (7/23), without any ectopic pregnancy. Complications such as tubal perforation, infection, or bleeding did not occur. Tubal catheterization was straightforward and smooth in 17/23 cases. For a hyperflexed uterus (6/23), a curved tip of the catheter was helpful in tubal probing. CONCLUSION: Fluoroscopically guided transcervical fallopian tube recanalization is a patient-friendly alternative to tubal microsurgery and in-vitro fertilization. Tubal catheterization with 4F glide catheter and glidewire further streamlines the procedure.

Adult↗
PubMed2003

Posterior semicircular canal dehiscence: a morphologic cause of vertigo similar to superior semicircular canal dehiscence.

The aim of this study was to assess imaging findings of posterior semicircular dehiscence on computed tomography and to evaluate incidence of posterior and superior semicircular canal dehiscence in patients presenting with vertigo, sensorineuronal hearing loss or in a control group without symptoms related to the inner ear. Computed tomography was performed in 507 patients presenting either with vertigo ( n=128; 23 of these patients suffered also from sensorineuronal hearing loss), other symptoms related to the inner ear, such as hearing loss or tinnitus ( n=183) or symptoms unrelated to the labyrinth ( n=196). All images were reviewed for presence of dehiscence of the bone, overlying the semicircular canals. Twenty-nine patients had superior semicircular canal dehiscence. Of these patients, 83% presented with vertigo, 10% with hearing loss or tinnitus and the remaining 7% with symptoms unrelated to the inner ear. In 23 patients dehiscence of the posterior semicircular canal was encountered. Of these patients, 86% presented with vertigo, 9% with hearing loss or tinnitus and 5% with symptoms unrelated to the inner ear. Defects of the bony overly are found at the posterior semicircular canal, in addition to the recently introduced superior canal dehiscence syndrome. Significant prevalence of vertigo in these patients suggests that posterior semicircular canal dehiscence can cause vertigo, similar to superior semicircular canal dehiscence.

Case-Control Studies↗
PubMed2003

Vascular capsule for telemetric monitoring of blood pressure.

PURPOSE: Development and experimental evaluation of an intravascular monitoring system for telemetric measurement of blood pressure and heart rate. MATERIALS AND METHODS: The monitoring system consists of an implantable silicone capsule (diameter 2.3 mm), containing a dedicated microchip with pressure sensors and signal-processing circuits as well as an antenna for wireless data and energy transfer using 6.78 MHz transponder technology. Three self-expanding legs at one end of the capsule served as a mechanism to lock the capsule at an arterial branch. A flow model, driven by a ventricular assist system, was used for testing and optimizing the implantation equipment, for checking the anchoring mechanism and for ensuring transmission of the measured pressure to the readout unit. In-vivo experiments were performed in 8 minipigs (weight 25 to 30 kg), with three capsules placed in each minipig via the femoral artery using a dedicated 8-F sheath/pusher system. Follow-up was by CT angiography for up to 6 months after implantation. RESULTS: Flow model tests revealed a maximum deviation of pressure and heart rate measurements of 5% from the reference measurements. Signal transmission was reliable over a distance of 3 to 4 cm. Fluoroscopically guided in-vivo implantation of the capsules was simple and straightforward. In arteries with a diameter of 5 to 6 mm, the capsules were permanently fixed with one or two legs interlocked in side branches and without occlusion within 6 months. Three capsules developed a small non-occlusive appositional thrombus attached to the downstream (leg) part of the capsule. CONCLUSION: Our in-vitro and in-vivo experiments demonstrate the feasibility of wireless transmission from a capsule with a sufficient resolution of the sensor output signals to determine blood pressure and pulse rate. As long as the vessel diameter is wide enough, arterial fixation of the capsule does not induce thrombotic occlusion of the parent artery. With respect to future clinical applications, further refinements of the transmission technology are needed to extend the transmission distance between capsule and reader antenna. The technology of intelligent implants has further implications, such as monitoring of other physiological parameters, and the design of a control loop, which may be used for therapeutic feedback.

Animals↗
PubMed2003

[Refinement of cytopathology of CT-guided fine needle aspiration biopsies with additional histologic examination of formalin-fixed blood-clots].

PURPOSE: To evaluate formalin-fixed blood-clot for diagnostic efficacy and safety in percutaneous CT-guided fine needle aspiration biopsy (FNAB) in addition to cytopathology. MATERIALS AND METHODS: 61 CT-guided FNABs were entered into a prospective trial. FNAB was performed in 22 female and 39 male patients (32 - 83 years, m = 62.8 +/- 10.9 y) using 20- (n = 7) and 22-gauge (n = 54) needles. After correct placement within the tumor, material for cytopathological work-up was harvested. Additional material was sampled by needling (stirring and aspirating) within the lesion. These blood-clots were fixed in buffered formalin and delivered for histopathological work-up along with the smears. All results were correlated with the clinical course of the patient; cases of negative biopsies underwent surgery or were followed clinically for a minimum of 13 months (m = 14.8 +/- 1.4 months). Finally, all puncture-related side-effects and complications were analyzed and compared with data from 108 transthoracic FNABs performed over a two-year period before using this technique. RESULTS: Tissue samples adequate for pathological diagnosis were obtained in 93.4 % (57 of 61 patients). Malignant cells were found in 50 samples, and 7 biopsy results were negative. The relevant pathological changes were depicted on both smear and blood-clot in 47 cases (82.4 %). In the remaining patients, the diagnoses were exclusively established by cytopathology (n = 6) and histopathology (n = 4). Altogether, additional information was obtained in 20 of the 57 FNABs (35.1 %). In the 47 cases with relevant findings obtained with both methods, the routine stain already led to the correct diagnosis in 9 cases by showing cohesive layers of malignant cells, and immunocytochemistry allowed subclassification of the biopsy material in additional 7 cases. Pneumothorax occurred in 12 of 38 transpleural punctures (31.6 %), hemoptysis in one patient (2.6 %). Four pneumothoraces required further treatment (3 thoracocenteses, 1 chest tube placement). Hemorrhagic complications requiring further treatment were not seen, but two minor hematomas were observed in the 19 abdominal punctures. The overall rate for pneumothorax was 38.9 % (42 of 108 interventions) for the FNAB performed in standard technique. CONCLUSION: Histological work-up of sampled blood-clots yielded a higher accuracy of CT-guided FNABs. Additional immunocytochemical studies allowed subclassification of tumor material. The complication rate of this technique was not higher than for FNAB alone.

Adult↗
PubMed2003

Value of 3D-volume rendering in the assessment of coronary arteries with retrospectively ECG-gated multislice spiral CT.

PURPOSE: To assess the diagnostic value and measurement precision of 3D volume rendering technique (3D-VRT) from retrospectively ECG-gated multislice spiral CT (MSCT) data sets for imaging of the coronary arteries. MATERIAL AND METHODS: In 35 patients, retrospectively ECG-gated MSCT of the heart using a four detector row MSCT scanner with a standardized examination protocol was performed as well as quantitative X-ray coronary angiography (QCA). The MSCT data was assessed on segmental basis using 3D-VRT exclusively. The coronary artery diameters were measured at the origin of each main coronary branch and 1 cm, 3 cm and 5 cm distally. The minimum, maximum and mean diameters were determined from MSCT angiography and compared to QCA. RESULTS: A total of 353 of 525 (67.2%) coronary artery segments were assessable by MSCT angiography. The proximal segments were more often assessable when compared to the distal segments. Stenoses were detected with a sensitivity of 82.6% and a specificity of 92.8%. According to the Bland-Altman method the mean differences between QCA and MSCT ranged from -0.55 to 1.07 mm with limits of agreement from -2.2 mm to -2.7 mm. CONCLUSION: When compared to QCA, the ability of 3D-VRT to quantitatively assess coronary artery diameters and coronary artery stenoses is insufficient for clinical purposes.

Coronary Angiography↗
PubMed2002

The petromastoid canal on computed tomography.

The objective was to assess visibility and anatomy of the petromastoid canal in high-resolution CT. Computed tomography images of 188 patients were reviewed for delineation of the petromastoid canal. This bony canal connects the mastoid antrum with the cranial cavity and houses the subarcuate artery and vein. The diameter, obtained in the middle portion of the canal, was compared with the diameter of the vestibular and cochlear aqueduct in all patients, and absolute values measured in 20 cases. Collimation was 1 mm in 164 and 2 mm in 24 examinations. Additionally, temporal bone of a cadaver was imaged and microdissected. The petromastoid canal was identified bilaterally in all 164 scans that were obtained with a slice thickness of 1 mm. In 5 of the 24 patients imaged with a collimation of 2 mm, the canal was not visible, most probably due to partial-volume effects. The petromastoid canal had the same diameter as the cochlear aqueduct in 42/44 (right/left), exceeded it in 66/61 and was smaller in 75/78 cases. In comparison to the vestibular aqueduct it had an equal diameter in 38/41 (right/left), exceeded it in 63/61, and was rated as smaller in 82/81 temporal bones. Diameters for the canals were: petromastoid canal 0.51+/-0.04 mm; cochlear aqueduct 0.57+/-0.03; and vestibular aqueduct 0.63+/-0.06 mm. Microdissection of the specimen revealed the entire course of the canal and demonstrated a similar appearance of the structure as in the images. The petromastoid canal can easily be identified on high-resolution, thin-slice CT images. Knowledge of the anatomy of this bony canal prevents misinterpretation as pathological structure, such as fracture line, which might occur if this structure is not known.

Adult↗
PubMed2002

[Selective CT mesentericography in the diagnostics of obscure overt intestinal bleeding: preliminary results].

AIM: To evaluate intra-arterial CT mesentericography (CTM) in the diagnostics of severe obscure overt intestinal bleeding in comparison with conventional mesentericography (MG) and surgery. METHODS: In 8 patients (23 - 82 years, mean 59 years), CTM was performed via the catheter left in the superior mesenteric artery after MG to detect the source of bleeding. Early and late-phase spiral CT scans were acquired after administration of contrast medium. Active bleeding was considered to be present if extravasation of contrast medium into the bowel was found. The results of MG and CTM were compared with the results of surgery. RESULTS: With MG active bleeding was found in one patient, with CTM in five patients. In three patients, both MG and CTM were negative. Six patients underwent surgery. Five cases of bleeding detected with CTM were confirmed by surgery. In one case, bleeding found with CTM was not confirmed by surgery. One patient underwent surgery although all imaging procedures were negative. The source of bleeding remained unknown. Surgically, the site of bleeding was located in the jejunum in 3 patients (jejunitis, jejunal ulcers, carcinoid), one patient had a diverticulum in the ascending colon. The colonic bleeding site was correctly localized with CTM, whereas the small bowel bleeding could only roughly be assigned to the proximal or distal jejunum or jejunoileal transition area. CONCLUSION: Preliminary results indicate that selective CTM is superior to MG in the evaluation of severe obscure overt intestinal bleeding.

Adult↗
PubMed2002

Axial flow catheter pump for circulatory support.

AIM: The development of a percutaneously insertable catheter pump for temporary left ventricular and circulatory support in patients with acute ischemic cardiomyopathy. MATERIAL AND METHODS: The expandable axial flow pump (introduction diameter 9-F, expanded diameter 6.5 mm) is mounted at the tip of a catheter, designed to be placed in aortic transvalvular position. Hydrodynamic tests were performed in a static flow model and in a pulsatile mock circuit (Medos VAD, Stolberg, Germany). Cardiogenic shock was simulating in vitro and in vivo. RESULTS: At a rotation speed of 32,000 rpm the catheter pump delivered a maximum flow of more than 4.0 L/min against a systemic mean pressure of 60 mmHg. Under shock simulation the pump significantly improved output and systemic pressure. CONCLUSION: A percutaneously insertable catheter pump is technically feasible. Hydrodynamic efficacy allows sufficient cardiac support under simulated shock condition.

Animals↗
PubMed2002

Multidetector CT of the spine in multiple myeloma: comparison with MR imaging and radiography.

OBJECTIVE: The purpose of this study was to compare multidetector CT (MDCT) of the thoracic and lumbar segments of the spine with MR imaging and conventional radiography for bone lesion detection and for evaluating the risk of vertebral fracture in multiple myeloma. SUBJECTS AND METHODS: Eighteen patients with multiple myeloma stage III (according to the criteria of Durie and Salmon) underwent MDCT, conventional radiography, and MR imaging of the lumbar and thoracic spine. MDCT was performed using a standard protocol with no contrast material. Source images were reconstructed using an effective slice thickness of 3 mm with an overlapping reconstruction increment (0.8 mm). Secondary coronal and sagittal multiplanar reformations were exclusively used for establishing the diagnosis. Findings were compared with those of MR imaging and conventional radiography. RESULTS: In all patients, coronal and sagittal multiplanar reformations depicted the extent of osseous destruction and provided detailed information about osseous infiltration and potential bone instability. Compared with conventional radiography, an additional 24 affected vertebrae, 15 additional vertebral fractures, and six vertebrae at further risk of fracture were detected on MDCT. Compared with MR imaging, three additional endangered vertebrae were detected on MDCT. MR imaging alone would have lead to an understaging of five (27.8%) of 18 patients. Using combined radiography and MR imaging, disease in three (16.7%) of 18 patients would have been understaged. CONCLUSION: MDCT seems to be preferable to conventional radiography in evaluating bone destruction in multiple myeloma. In combination with MR imaging, detailed information for staging these tumors is obtained. For the initial staging in patients with multiple myeloma, MDCT in combination with MR imaging seems to be the method of choice.

Aged↗
PubMed2001

Fragmentation of massive pulmonary embolism by pigtail rotation catheter: possible complication.

Fragmentation by pigtail rotation catheter may be a therapeutic option in acute massive pulmonary embolism, especially in patients with high risk of right ventricular failure. We report a patient with an occlusion of the right intermediate pulmonary artery by a large embolus, slightly protruding into the perfused right upper lobe artery. After initial catheter fragmentation, part of the embolus dislocated and produced an additional occlusion of the upper lobe artery. Hemodynamic parameters deteriorated. Continuation of catheter fragmentation finally provided for a hemodynamic stabilization and partial recanalization. Inadvertent occlusion of a major pulmonary arterial branch by dislocated embolus material may be considered as a complication of catheter fragmentation, which can be successfully managed by continuation of the fragmentation therapy.

Adult↗