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Erik Morre Pedersen

Publications and source records attributed to Erik Morre Pedersen.

7 recordsLinked to original sources
PubMed2004

In vivo heating of pacemaker leads during magnetic resonance imaging.

AIMS: Magnetic resonance imaging (MRI) is well established as an important diagnostic tool in medicine. However, the presence of a cardiac pacemaker is usually regarded as a contraindication for MRI due to safety reasons. In this study, heating effects at the myocardium-pacemaker lead tip interface have been investigated in a chronic animal model during MRI at 1.5 Tesla. METHODS AND RESULTS: Pacemaker leads with additional thermocouple wires as temperature sensors were implanted in nine animals. Temperature increases of up to 20 degrees C were measured during MRI of the heart. Significant impedance and minor stimulation threshold changes could be seen. However, pathology and histology could not clearly demonstrate heat-induced damage. CONCLUSIONS: MRI may produce considerable heating at the lead tip. Changes of pacing parameters due to MRI could be seen in chronic experiments. Potential risk of tissue damage cannot be excluded even though no reproducible alterations at the histological level could be found.

Animals↗
PubMed2004

Operator-independent isotropic three-dimensional magnetic resonance imaging for morphology in congenital heart disease: a validation study.

BACKGROUND: Operator-independent isotropic 3D MRI may greatly simplify the assessment of complex morphology in congenital heart disease. We sought to evaluate the reliability of this new approach. METHODS AND RESULTS: In 31 adolescent and adult patients (age, 6 to 42 years; median, 16 years) with congenital heart disease, cardiac morphology was determined with free-breathing (navigator-gated), isotropic, 3D steady-state free-precession (3D SSFP) MRI and independently evaluated by 2 observers. Cardiac diagnoses and multiple distance measurements were compared with conventional MR reference sequences (ie, spin-echo, cine gradient-echo, contrast-enhanced MR angiography) and with echocardiography/cine cardioangiography or surgery. Of the 31 patients, 24 had native congenital heart defects or residual defects after repair that warranted immediate treatment. None of these defects was missed by 3D SSFP. Novel diagnostic issues were discovered in 4 of 31 patients (coronary anomalies, n=3; left juxtaposition of the right atrial appendage in double-outlet right ventricle and transposition of the great arteries, 1). For sizes of valves and vessels, we found minor mean differences of -1.1 to 1.6 mm, with SD ranging from 1.2 to 2.9 mm, demonstrating overall good agreement with standard MRI (Bland-Altman analysis). Interobserver variability of 3D SSFP distance measures was low; mean differences ranged from -1.5 to 1.0 mm, and SD ranged from 0.8 to 2.5 mm. Scatter was lower for extracardiac than intracardiac measures. CONCLUSIONS: In adolescents and adults, isotropic 3D SSFP MRI allows reliable assessment of complex cardiac morphology. Distance measurements are accurate and reproducible. Thus, a single operator-independent acquisition may substitute for conventional 2D MRI sequences to accelerate and simplify MR scanning in congenital heart disease.

Adolescent↗
PubMed2004

Three-dimensional phase contrast velocity mapping acquisition improves wall shear stress estimation in vivo.

The purpose of this study was to evaluate and apply high-resolution three-dimensional phase contrast mapping for estimation of wall shear stress in vivo. A silicon pipe of 8 mm diameter with a 8.3 ml/s steady flow and the entrance of the carotid bifurcation in 10 young healthy volunteers aged 23.6 +/- 3.1 years was studied. Very high resolution three-dimensional and two-dimensional phase contrast mapping sequences with spatial resolutions of 0.31 x 0.31 x 1.5 mm(3) and 0.31 x 0.31 x 3 mm(3), respectively, were compared in vivo and in vitro. Wall shear stress was calculated using multi-sectored, three-dimensional paraboloid fitting. In comparison to the two-dimensional measurements, the three-dimensional method with only half the slice thickness gave higher signal-to-noise ratio and velocity-to-noise ratios both in vivo and in vitro. Wall shear stress derived from the three-dimensional velocity measurements did not differ from the two-dimensional velocity measurements either in vitro or in vivo. Mean wall shear stress was lowest and oscillatory shear index was highest at the outer wall, towards the carotid bifurcation. Three-dimensional velocity mapping increases resolution and image quality and allows estimation of wall shear stress patterns circumferentially and longitudinally in human arteries.

Adult↗
PubMed2003

Visualization of morphological details in congenitally malformed hearts: virtual three-dimensional reconstruction from magnetic resonance imaging.

In recent years, three-dimensional imaging has provided new opportunities for visualizing congenital cardiac malformations. We present the initial clinical experience using a recently implemented system, which employs some of new interactive, real-time, techniques. We show how three-dimensional rendering based on magnetic resonance imaging can provide detailed spatial information on both intrinsic and extrinsic cardiac relations, and hence how a virtual examination can potentially provide new means to a better understanding of complex congenital cardiac malformations.

Adult↗
PubMedDate not supplied

Three-dimensional, isotropic MRI: a unified approach to quantification and visualization in congenital heart disease.

PURPOSE: Current standards in magnetic resonance imaging of congenital heart disease are based mostly on anisotropic protocols to image both morphology and function. Operator-dependent acquisition planning is typically needed to obtain the desired images. We propose to instead use operator-independent, three-dimensional, isotropic imaging protocols to acquire both morphology and function (cine and flow) of the entire heart in a few standardized acquisitions. Subsequently, due to the isotropic property of the data, any desired imaging plane can be "imaged" offline by interactive planar reformatting and used for qualitative and quantitative diagnostic evaluation. MATERIALS AND METHODS: Morphological data was acquired in patients using 3D steady state free precession (SSFP) protocols, and functional data in volunteers using multislice 2D or 3D cine SSFP as well as 3D, three-component phase-contrast velocity mapping with EPI readouts. Tools to integrate morphological and functional offline image evaluation based on interactive planar reformatting, volume rendering, and corresponding quantification tools were implemented and discussed. RESULTS: We successfully acquired and integrated morphology and flow and demonstrated potential clinical applications. CONCLUSION: User independent acquisitions of morphological and functional isotropic 3D datasets with real-time, interactive planar reformatting, volume rendering, and integration of morphology and function, have the potential to replace conventional, user dependent, anisotropic 2D imaging in patients with cardiac malformations.

Adolescent↗
PubMedDate not supplied

Two-phase active contour method for semiautomatic segmentation of the heart and blood vessels from MRI images for 3D visualization.

The paper presents an active-contour segmentation method for 2D structures in MR images. The method combines two approaches to active contour segmentation, known as balloons and snakes. This makes the method shape independent and accurate. New anti-tangling features were introduced to improve segmentation of very complex object shapes, e.g. the left ventricle with papillary muscles. The method was applied to segment all large structures in the cardiovascular system and its outcome was used for 3D visualization.

Blood Vessels↗