Lambertus W. Bartels

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An automated method for segmenting the outer boundary of abdominal aortic aneurysms in MR images is presented. The method is based on the well known Active Shape Models (ASM), which fit a global landmark-based shape model on the basis of local boundary appearance models. The original three-dimensional ASM scheme is modified to deal with multi-spectral image(More)
In high-field MRI severe problems with respect to B(1) (+) uniformity and specific absorption rate (SAR) deposition pose a great challenge to whole-body imaging. In this study the potential of a phased array transmit coil is investigated to simultaneously reduce B(1) (+) nonuniformity and SAR deposition. This was tested by performing electromagnetic(More)
In internal radiation therapy of unresectable liver tumors, microspheres containing a radionuclide are injected in the hepatic artery to achieve a preferential deposition of microspheres in the lesions. In this study, MR imaging techniques for qualitative and quantitative assessment of the biodistribution of holmium-loaded microspheres (HoMS) were(More)
Perfusion imaging with pulsed arterial spin labeling techniques, like flow-sensitive alternating inversion recovery (FAIR), may suffer from inflow of fresh, i.e., unlabeled, spins. Inflow of fresh spins is caused by the arrival of unlabeled spins in the image slice and can lead to underestimation of the perfusion if not taken into account. In this study it(More)
OBJECTIVE The purpose of this prospective multicenter study was to assess the safety and technical feasibility of volumetric Magnetic Resonance-guided High Intensity Focused Ultrasound (MR-HIFU) ablation for treatment of patients with symptomatic uterine fibroids. METHODS Thirty-three patients with 36 fibroids were treated with volumetric MR-HIFU(More)
PURPOSE During MR-guided high-intensity focused ultrasound (HIFU) therapy, ultrasound absorption in the near field represents a safety risk and limits efficient energy deposition at the target. In this study, we investigated the feasibility of using T2 mapping to monitor the temperature change in subcutaneous adipose tissue layers. METHODS The T2(More)
In this study, a method is proposed for MRI of the lumen of metallic vascular implants, like stents or vena cava filters. The method is based on the reduction of artifacts caused by flow, susceptibility, and RF eddy currents. Whereas both flow artifacts and susceptibility artifacts are well understood and documented, RF artifacts are not. Therefore, the(More)
MRI allows for absolute temperature measurements in substances containing two spectral resonances of which the frequency difference Delta f(T) is related to absolute temperature. This frequency difference can be extracted from spectroscopic data. An image-based MR technique that allows for the acquisition of spectroscopic data at high temporal and spatial(More)
The advantage of 2D-3D image registration methods versus direct image-to-patient registration, is that these methods generally do not require user interaction (such as manual annotations), additional machinery or additional acquisition of 3D data. A variety of intensity-based similarity measures has been proposed and evaluated for different applications.(More)
BACKGROUND AND PURPOSE Time-of-flight (TOF) magnetic resonance angiography (MRA) is commonly used to visualize the carotid arteries; however, flow void artifacts can appear. Our purpose was to determine the frequency and diagnostic meaning of flow voids by using real patient data, as part of a larger study of MRA compared with the criterion standard,(More)