Sylvia Kinzel

Molecular magnetic resonance imaging of atrial clots in a swine model.

Background—The detection and differentiation of intracardiac masses is still challenging and may include neoplasms and thrombi. The aim of this study was the investigation of a targeted, fibrin-specific contrast agent (EP-2104R) for molecular targeted magnetic resonance imaging (MRI) of left atrial clots. Methods and Results—Chronic human thrombi were surgically implanted in the left atrial appendage of 5 swine. Molecular MRI was performed with a navigator-gated, free-breathing, cardiac-triggered 3D inversion-recovery, black-blood, gradient-echo sequence before and after systemic administration of 4 &mgr;mol/kg EP-2104R. MR images were analyzed by 2 investigators, and the contrast-to-noise ratio was calculated. Location of clots was confirmed by autopsy, and the gadolinium concentration in the clots was assessed. Before contrast agent administration, thrombi were not visible on black-blood MR images. After contrast administration, all atrial clots (n=5) were selectively visualized as white spots with a high contrast-to-noise ratio (clot/blood, 29.7±8.0). The gadolinium concentration in the clots averaged 74±45 &mgr;mol/L. Conclusions—The fibrin-specific MR contrast agent EP-2104R allows for selective and high-contrast visualization of left atrial clots by means of molecular targeted MRI.

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

Abstract.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.

Use of a nonmetallic guide wire for magnetic resonance-guided coronary artery catheterization.

Rationale and Objectives:Metallic guide wires can be subject to substantial heating when used in the magnetic resonance (MR) environment. Therefore, animal experiments were performed to test the feasibility of a non-metallic and MR-safe guide wire with passive markers for catheterization of coronary arteries under MR guidance. Materials and Methods:Self-made guide wires consisting of a resin-microparticle compound covered by polytetrafluoroethylene were used to catheterize both coronary arteries of swine together with a non-braided catheter. Time needed for catheterization was recorded. Results:MR-guided coronary artery catheterization with passive visualization of a self-made non-metallic guide wire is possible. In average 141 seconds (SD 68) were needed to manipulate the guide wire together with a catheter from the carotid artery into the left or right coronary artery ostium. Conclusion:Standard nitinol guide wires have to be considered unsafe for MR-guided interventions due to possible heating of electrical conducting structures in the MR environment. Passive visualization techniques allow MR-guided catheterization of small arteries like coronaries. However, there is the substantial disadvantage of obscuring the underlying anatomy of small vessels by the passive markers needed for real-time MR guidance.

New metallic MR Stents for artifact-free coronary MR angiography: Feasibility study in a swine model

Rationale and Objectives:The objective of this study was to investigate the potential for artifact-free coronary magnetic resonance angiography (cMRA) in the presence of dedicated metallic MR stents in vitro and in a swine model. Methods:All investigations were performed at 1.5 T, applying a standard cMRA gradient echo sequence with a T2 preparation pulse. Two prototypes of each hand-woven, mechanically woven, and lasered Aachen Resonance Coronary MR Stents made out of an MR-compatible metallic alloy and dilated to 2.5 mm and 4 mm were examined in a water bath. Results:Artifact behavior was judged independently by 2 radiologists as showing “no artifacts” for all tested stent types. Signal-to-noise ratios inside and outside of the stents were measured yielding a Pearson correlation coefficient of 0.98 (y = 1.22 + 0.92x). Nineteen stents (8 hand woven, 3 mechanically woven, 8 lasered) were deployed in coronary arteries of 19 domestic pigs and were examined by cMRA. Artifact behavior of the stents was analyzed by measuring the signal-to-noise ratio at the stent positions and compared with signal-to-noise ratio measurements outside of the stents, yielding a Pearson correlation coefficient of 0.90 (y = −0.75 + 1.06x). Conclusions:All 3 prototypes of coronary MR stents allowed complete visualization of the stent lumen and consequently determination of stent patency by cMRA.

Magnetic Resonance-Guided Angioplasty With Delivery of Contrast-Media Doped Solutions to the Vessel Wall : An Experimental Study in Swine

Objectives:To assess the feasibility of magnetic resonance (MR)-guided delivery of a solution containing contrast-medium and immediate online monitoring of its distribution to the vessel wall during MR-guided angioplasty in peripheral arteries. Materials and Methods:In 3 pigs, the feasibility of MR-guided atraumatic delivery of a solution containing contrast-medium and tissue dye (0.05 mmol/mL Gd-DTPA, 3% Evans blue dye) into the vessel wall of the iliac arteries was tested using a permeable balloon catheter (8 mm). Catheter placement was monitored using a steady-state free precession real-time imaging sequence. Additionally, in 5 pigs, surgically created bilateral stenoses in the external iliac artery were dilatated with the porous balloon. In these animals, contrast-enhanced MR angiography was performed before and after the interventions to assess the degree of the stenosis. In all animals, the vessel wall was delineated before and after dilatation using a T1-weighted gradient echo (GE) sequence. Results:In the 3 animals without stenosis, contrast medium was successfully applied to the vessel wall. On the GE images, the normalized signal intensity of the vessel wall was 0.95 ± 0.015 arbitrary units (a. u.) prior and 2.15 ± 0.105 a. u. after the intervention (P < 0.01). In the animals with stenosis, MR angiography performed before and after the intervention demonstrated successful dilatation of 9 of the 10 stenoses. Before the intervention, 7 stenoses were severe (76%–99%) and 3 moderate (50%–75%), and after the intervention, 4 stenoses were completely removed and 5 mild (<50%). Also in these 5 animals, the solution was visible in the vessel wall of the arteries on the T1-weighted GE MR images (normalized signal intensity prior the intervention 1.33 ± 0.16 a. u. and 2.97 ± 0.23 after angioplasty; P < 0.05). Histology demonstrated the distribution of the Evans blue dye within the vessel wall in all animals. Conclusions:MR-guided delivery of a contrast-medium containing solution and immediate online assessment of its distribution to the vessel wall during angioplasty in peripheral arteries is feasible.

Long-term retrieval of modified Günther Tulip vena cava Filters: an animal study.

We modified the Günther Tulip Filter to allow long-term retrieval and tested this modified filter design in an animal experiment. Fourteen modified Günther Tulip Filters (Celect filter) were inserted percutaneously into the inferior venae cavae of 7 domestic adult sheep (2 filters per animal). Before removal, 3 months after filter placement, cavography was performed and the filters were removed. Subsequently, cavography was obtained to check for any signs of bleeding. All venae cavae were prepared, removed, and macroscopically examined for bleeding. Filter placement was easy and successfully performed in all cases. No thrombi were detected inside the filters. All cases showed some narrowing of the vena cava at the level, where the filter legs were connected with the vessel wall. Neither cavograms after filter removal nor macroscopic examinations of the perivascular vena cava tissue showed any significant bleeding. The modified Günther Tulip Filter allowed for successful and uncomplicated filter removal up to 3 months after placement.

MSCT Vitalitätsdiagnostik in verschiedenen Phasen des Myokardinfarktes: tierexperimentelle Ergebnisse

Ziele: Intraindividueller Vergleich der myokardialen Spatanreicherung mittels Mehrschicht-Spiral CT (MSCT) und Kernspintomographie (MRT) fur die Beurteilung der verschiedenen Stadien der myokardialen Spatanreicherung. Methode: In acht Schweinen wurde ein akuter reperfundieter Myokardinfarkt durch Ballonokklusion der LAD induziert. MR und MSCT Vitalitatsdiagnostik mittels Kontrastmittelspatanreicherung erfolgten am Tag 0 sowie 7, 28 and 90 Tage nach Koronarokklusion. Anschliesend wurden die Tiere getotet, das Herz entnommen und mit 2,3,5-Triphenyltetrazolinchlorid (TTC) gefarbt. Mittels Bland-Altman Plots und Multivarianzanalyse wurde die Infarktgrose zwischen den verschiedenen Modalitaten sowie uber die Zeit verglichen. Ergebnis: Ein Tier verstarb wahrend der Infarktinduktion. In der MSCT (MRT) betrug die mittlere Infarktgrose am Tag 0 23,7±11,8% (24,5±10,6%) der linksventrikularen Myokardflache. Bis zu Tag 90 schrumpfte das Infarktareal auf 16,9±8,4% (MSCT) bzw. 18,9±8,0% (MRT). Im TTC gefarbten Sektionspraparat betrug die Infarktflache 16,8±8,2%. Hinsichtlich der Infarktausdehnung konnte zwischen MSCT und MRT kein signifikanter Unterschied gezeigt werden. Hingegen war die Anderung der Infarktgrose uber die Zeit statistisch signifikant (p=0,0019). Schlussfolgerung: Die myokardiale Kontrastmittelspatanreicherung in MSCT und MRT korrelieren wahrend der verschiedenen Stadien des reperfundierten Myokardinfarktes gut. Dies erlaubt eine zuverlassige Beurteilung der Ausdehnung reperfundierter Myokardinfarkte wahrend der akuten, subakuten und chronischen Phase. Korrespondierender Autor: Mahnken AH Universitatsklinikum Aachen, Klinik fur radiologische Diagnostik, Pauwelsstrasse 30, 52074 Aachen E-Mail: mahnken@rad.rwth-aachen.de