Biomedical subjects

Roman Fischbach

Publications and source records attributed to Roman Fischbach.

29 records · Page 2Linked to original sources

PubMed2003

Thoracic aortic stent graft: comparison of contrast-enhanced MR angiography and CT angiography in the follow-up: initial results.

The objective of this study was to compare contrast-enhanced magnetic resonance angiography (CE MRA) and multislice computed tomographic angiography (MS CTA) in the follow-up of thoracic stent-graft placement. The CE MRA and MS CTA were performed following nitinol stent-graft treatment due to thoracic aneurysm ( n=4), intramural bleeding ( n=2) and type-B aortic dissection ( n=5). Corresponding evaluation of arterial-phase imaging characteristics focused on the stent-graft morphology and leakage assessment. Stent-graft and aneurysm extensions were comparable between both techniques. Complete exclusion (aneurysm, n=4; dissection, n=2) was assessed with high confidence with CE MRA and MS CTA. Incomplete exclusion (intramural bleeding, n=2; dissection, n=3) was assigned to lower confidence scores on CE MRA compared with MS CTA. On CE MRA the stent-graft lumen demonstrated an inhomogeneous signal, the stent struts could not be assessed. The CE MRA can be used as alternative non-invasive imaging for follow-up of nitinol stent grafts. Arterial-phase leak assessment can be less evident in CE MRA compared with MS CTA studies; therefore, the use of late-phase imaging seems to be necessary. The diagnostic gap of stent-graft fracture evaluation using MRA may be filled with plain radiographs.

Aged↗

PubMed2003

Hazardous situation in the MR bore: induction in ECG leads causes fire.

There is a potential hazard during examinations of patients with attached or implanted long conductors, e.g. ECG leads: an MR exam of the lumbar spine of a patient was performed in a 1.5-T scanner under ECG monitoring using equipment marked as MR compatible. Standard cabling of 370-cm length was guided without loops from the electrodes through the caudal opening of the magnet bore. During a sagittal T1-weighted turbo-spin-echo scan suddenly a flame of approximately 3 cm arose from the patient's shirt, close to the position of the electrodes. The supervising anaesthesiologist extinguished the flames with his hands. A subsequent physical examination revealed second- to third-degree burns. The analysis of the incident revealed that high voltages can be induced in straight conductors without loops as ECG cables by coupling with the electric component of the HF field. Local heating or sparking can cause an open flame at the position of the electrodes. This danger exists even with ECG equipment that is specifically marked as MR compatible.

Electrocardiography↗

PubMed2003

Evaluation of global left ventricular myocardial function with electrocardiogram-gated multidetector computed tomography: comparison with magnetic resonance imaging.

RATIONALE AND OBJECTIVES: Electrocardiogram-gated 3D volume data from multidetector computed tomography coronary angiography (MDCT-CA) enable image reconstruction in any phase of the cardiac cycle. The objective was to determine left ventricular (LV) function parameters by MDCT in comparison to cine magnetic resonance imaging (MRI). METHOD: Thirty patients with known or suspected coronary artery disease (CAD) underwent MDCT-CA. From multiplanar reformations in short axis orientation end-diastolic and end-systolic LV volumes (LVEDV, LVESV) were determined to calculate LV stroke volume and ejection fraction (LVSV, LVEF) and compared with MRI measurements. RESULTS: LVEDV (147 +/- 27 mL) and LVESV (65 +/- 22 mL) determined by MDCT correlated well to the respective MRI measurements (LVEDV 133 +/- 27 mL, r = 0.80, P < 0.001; LVESV 48 +/- 19 mL, r = 0.89, P < 0.001). LVSV (MDCT 82 +/- 15 mL; MRI 85 +/- 17 mL; r = 0.77, P < 0.001) and LVEF (MDCT 56 +/- 9%; MRI 65 +/- 8%; r = 0.85, P < 0.001) showed a good correlation as well. LVEF was significantly underestimated by MDCT (-8.5 +/- 4.7%, P < 0.001). CONCLUSIONS: Initial experience in patients evaluated for CAD shows that spiral MDCT studies may provide LV functional data in good correlation to Cine MRI.

Adult↗

PubMed2003

Improved coronary artery stent visualization and in-stent stenosis detection using 16-slice computed-tomography and dedicated image reconstruction technique.

OBJECTIVE: The aim of this study was to compare the visualization of different coronary artery stents and the detectability of in-stent stenoses during 4-slice and 16-slice computed tomography (CT) angiography in a vessel phantom. MATERIAL AND METHODS: Ten coronary stents were introduced in a coronary artery vessel phantom (plastic tubes with an inner diameter of 3 mm, filled with iodinated contrast material diluted to 220 Hounsfiled Units [HU], surrounded by oil [60 HU]). CT scans were obtained perpendicular to the stent axes on a 4-slice scanner (detector collimation 4x1 mm; table feed 1.5 mm/rotation, mAs 300, kV 120, medium-smooth kernel) and a 16-slice scanner (detector collimation 12x0.75 mm; table feed 2.8 mm/rotation, mAs 370, kV 120, reconstruction with a standard and an optimized sharp kernel). Longitudinal multiplanar reformations were evaluated regarding visible lumen diameters and intraluminal attenuation values. Additionally, the stents were scanned with the same parameters after implantation of 60% stenoses (HU 30). RESULTS: Using the same medium-smooth kernel reconstruction with 4-slice and 16-slice CT, there was a slight increase in the average visible lumen area (26% versus 31%) and less increase of average intraluminal attenuation values (380 HU versus 349 HU). Significant improvement of lumen visualization (54%, P<0.01) and attenuation values (250, P<0.01) was observed for the 16-slice scans using the sharp kernel reconstruction. In-stent stenoses could be more reliably identified (or ruled out) by 16-slice CT and sharp reconstruction kernel when compared with the other 2 methods. CONCLUSION: 16-slice CT using a dedicated sharp kernel for image reconstruction facilitates improved visualization of coronary artery stent lumen and detection of in-stent stenoses.

Coronary Angiography↗

PubMed2003

CT colonography: Protocol optimization with multi-detector row CT--study in an anthropomorphic colon phantom.

PURPOSE: To determine optimal detector collimation, section thickness, and tube current for multi-detector row computed tomography (CT) colonography. MATERIALS AND METHODS: An anthropomorphic colon phantom with simulated polyps of varying size (2, 6, 8, 10, and 12 mm) was examined by using multi-detector row CT with varying combinations of detector collimation (4 x 1.0 mm and 4 x 2.5 mm), dose per section (10, 20, 40, 60, 80, 100, and 140 mAs), and section thickness/reconstruction interval (1.25/0.6, 2.0/1.0, 3.0/1.0, and 5.0/2.0 mm). Polyp depiction, longitudinal polyp distortion, and presence of rippling artifacts were assessed on reformatted three-dimensional endoluminal images by three reviewers. RESULTS: Longitudinal distortion and rippling artifacts increased with increasing section thickness and use of broader detector collimation. Polyps 8 mm or larger were depicted with any combination of section thickness, detector collimation, and tube current. Depiction of polyps 6 mm or smaller depended on the detector collimation/reconstructed section thickness and was rated optimal for the 4 x 1.0-mm detector collimation with a section thickness of 1.25 mm. This was also observed for low-dose protocols. Polyps 6 mm or smaller that were not detected with 3-mm section thickness and 4 x 2.5-mm detector collimation were detected with 1.25-mm section thickness and 10 mAs. CONCLUSION: A narrow detector collimation with thin-section imaging (4 x 1.0-mm detector collimation, 1.25-mm section thickness) is a prerequisite for low-dose (10-mAs) multi-detector row CT colonography.

Artifacts↗

PubMed2002

Imaging of coronary artery stents using multislice computed tomography: in vitro evaluation.

The aim of this study was to evaluate imaging features of different coronary artery stents during multislice CT Angiography (MSCTA). Nineteen stents made of varying material (steel, nitinol, tantalum) and of varying stent design were implanted in plastic tubes with an inner diameter of 3 mm to simulate a coronary artery. The tubes were filled with iodinated contrast material diluted to 200 Hounsfield units (HU), closed at both ends and positioned in a plastic container filled with oil (-70 HU). The MSCT scans were obtained perpendicular to the stent axes (detector collimation 4x1 mm, table feed 2 mm/rotation, 300 mAs, 120 kV). Axial images and multiplanar reformations were evaluated regarding artifact size, lumen visibility, and intraluminal attenuation values. Artifacts characterized by artifactual thickening of the stent struts leading to apparent reduction in the lumen diameter and increased intraluminal attenuation values were observed in all cases. The stent lumen was totally obscured in the Wiktor stent, the Wallgraft stent, and the Nir Royal stent. Partial residual of the stent lumen could be visualized in all other utilized stent products (artificial lumen reductions ranged from 62% in the V-Flex stent to 94% in the Bx Velocity stent). Parts of the stent lumen can be visualized in most coronary artery stents; however, detectability of in-stent stenoses remains to be evaluated for each stent type.

Artifacts↗

PubMed2002

Coronary magnetic resonance angiography for assessment of the stent lumen: a phantom study.

PURPOSE: To evaluate the feasibility of visualizing the stent lumen using coronary magnetic resonance angiography in vitro. MATERIAL AND METHODS: Nineteen different coronary stents were implanted in plastic tubes with an inner diameter of 3 mm. The tubes were positioned in a plastic container filled with gel and included in a closed flow circuit (constant flow 18 cm/sec). The magnetic resonance images were obtained with a dual inversion fast spin-echo sequence. For intraluminal stent imaging, subtraction images were calculated from scans with and without flow. Subsequently, intraluminal signal properties were objectively assessed and compared. RESULTS: As a function of the stent type, various degrees of in-stent signal attenuation were observed. Tantalum stents demonstrated minimal intraluminal signal attenuation. For nitinol stents, the stent lumen could be identified, but the intraluminal signal was markedly reduced. Steel stents resulted in the most pronounced intraluminal signal voids. CONCLUSIONS: With the present technique, radiofrequency penetration into the stents is strongly influenced by the stent material. Thesefindings may have important implicationsforfuture stent design and stent imaging strategies.

Blood Vessel Prosthesis Implantation↗

PubMed2002

Revealing in-stent stenoses of the iliac arteries: comparison of multidetector CT with MR angiography and digital radiographic angiography in a Phantom model.

OBJECTIVE: Our objective was to evaluate the detectability of in-stent stenoses in iliac artery stents using multidetector CT angiography in comparison with MR angiography and digital radiographic angiography. MATERIALS AND METHODS: Ten different metallic stents (made of steel, nitinol, tantalum, or cobalt) were implanted in plastic tubes (8 mm). The stent lumina were partially obstructed by wax (CT density, -30 H) resulting in 50-60% in-stent stenoses. The tubes were filled with diluted contrast material (25 mmol/L of gadopentetate dimeglumine or 6 mg I/mL of iodinated contrast material) and placed in a plastic container filled with oil or water, respectively. CT angiography was performed on a four-detector CT scanner (detector collimation, 4 x 1 mm; slice thickness, 1.25 mm; table feed, 4 mm per rotation). MR angiography was performed on a 1.5-T system with a three-dimensional gradient-echo sequence (TR/TE, 4.6/1.8; flip angle, 30 degrees; slice thickness, 1.88 mm). Axial and longitudinal reformations of CT and MR imaging data were evaluated regarding the in-stent attenuation and signal intensity, the visible lumen diameter inside the stent, and the delineation of the stenoses. For comparison, digital radiographic angiography was performed as the gold standard. RESULTS: The degree and character of stent-related artifacts differed in CT angiography and MR angiography. In CT angiography, only the tantalum stent caused artifacts that obscured the stenosis; in all other cases, the stenoses were visible. In MR angiography, depiction of stenoses was impaired in two steel stents but possible in the tantalum and most nitinol stents. CONCLUSION: CT angiography is suited for detection of relevant stenoses in steel, cobalt-based, and nitinol stents. MR angiography is superior only in tantalum products.

Angiography↗

PubMed2002

Using ECG-gated multidetector CT to evaluate global left ventricular myocardial function in patients with coronary artery disease.

OBJECTIVE: Retrospectively ECG-gated three-dimensional volume data from multidetector CT (MDCT) coronary angiography enable image reconstruction of the cardiac cycle in the diastolic and systolic phases. The objective of our study was to investigate the feasibility of determining left ventricular function from MDCT coronary angiography data sets in 22 patients with coronary artery disease and to study the correlation of MDCT results with those of functional data from biplane cineventriculography. CONCLUSION: Multiplanar reformations from three-dimensional MDCT data allowed good delineation of endocardial and epicardial left ventricular contours. In patients evaluated for coronary artery disease, MDCT coronary angiography with retrospective ECG gating provides functional data in an acceptable correlation (r = 0.8; p < 0.05) to biplane cineventriculography.

Adult↗

PubMed2001

Coronary artery aneurysm and type-A aortic dissection demonstrated by retrospectively ECG-gated multislice spiral CT.

The case of a 40-year-old male patient with a coronary aneurysm of the proximal left descending artery (LAD) combined with circumferential type-A dissection of the ascending aorta is reported. Computed tomography angiography of the coronary arteries was performed using multislice spiral computed tomography (MSCT) with retrospective ECG gating. Anatomical relations of the LAD aneurysm as well as the origin of the left coronary artery from the false lumen of the dissection were well depicted for planning of the surgical intervention using this new noninvasive imaging modality.

Adult↗

PubMedDate not supplied

Transbrachial thrombolysis, PTA and stenting in the lower extremities.

We present an analysis of 37 interventions in the arteries of the lower limbs via a transbrachial arterial approach. Twenty-six patients (42-79 years) underwent 37 interventional procedures in the lower extremities (iliac n = 6, iliac + femoro-popliteal n = 1, femoro-popliteal n = 30) with a vascular approach via the brachial artery (33 left sided, 4 right sided, introducer sheath 4-7 F). The transbrachial approach was chosen to avoid puncture of femoral bypass graft material. Technical success could be achieved in 11/13 thrombolyses, 8/9 PTAs, 7/10 combinations of thrombolysis and percutaneous transluminar angioplasty (PTA) and in the placement of two stents. One patient suffered from periprocedural severe re-thrombosis due to insufficient anticoagulation during fibrinolysis, and twice thrombolysis was incomplete. One puncture-related false aneurysm of the brachial artery had to be corrected surgically. One transient ischemic attack (TIA) and four minor complications occurred. Transbrachial vascular approach for arterial interventions in iliac and femoro-popliteal pathologies is a reasonable alternative to the transaxillary access if transfemoral puncture has to be avoided. The technical success rate is comparable with the results of the transaxillary and transfemoral approach. To minimize, at least theoretically, the risk of cerebral complications, the left-sided approach should be preferred and intravenous heparin should be administered routinely.

Adult↗