Geir Torheim

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PURPOSE To compare perfusion magnetic resonance imaging (MRI) and ventilation-perfusion scintigraphy (V-P scan) in the study of perfusion abnormalities in pulmonary embolism (PE) and to compare the PE results to the findings previously reported for pneumonia and chronic obstructive pulmonary disease (COPD), in terms of perfusion abnormalities. MATERIALS(More)
Colon cancer prevention currently relies on colonoscopy using white light to detect and remove polyps, but small and flat polyps are difficult to detect and frequently missed when using this technique. Fluorescence colonoscopy combined with a fluorescent probe specific for a polyp biomarker may improve polyp detection. Here we describe GE-137, a(More)
UNLABELLED The relatively low specificity of dynamic contrast-enhanced T1-weighted magnetic resonance imaging (MR) imaging of breast cancer has lead several groups to investigate different approaches to data acquisition, one of them being the use of rapid T2*-weighted imaging. Analyses of such data are difficult due to susceptibility artifacts and breathing(More)
A computer program to create magnetic resonance images simulating the main features of a magnetic resonance imaging (MR) machine was developed on a personal computer. The simulated MR images are calculated using the relevant equations describing a chosen pulse sequence on the basis of proton density,T 1 andT 2 images acquired from whole-body MR equipment.(More)
Perfusion magnetic resonance (MR) imaging is a promising new method for detection of perfusion defects in the diagnosis of pulmonary embolism. In the present study we evaluated the first-pass characteristics of perfusion MR imaging in patients with pneumonia or chronic obstructive pulmonary disease (COPD), frequent differential diagnoses to pulmonary(More)
Recent studies have demonstrated the potential of dynamic contrast-enhanced magnetic resonance imaging (MRI) describing pulmonary perfusion. However, breathing motion, susceptibility artifacts, and a low signal-to-noise ratio (SNR) make automatic pixel-by-pixel analysis difficult. In the present work, we propose a novel method to compensate for breathing(More)
PURPOSE To evaluate the feasibility of using dynamic contrast-enhanced MR imaging with a new intravascular contrast agent in grading human breast cancer. MATERIAL AND METHODS 23 patients with 27 breast tumors (21 carcinomas and 6 fibroadenomas) were examined with dynamic MR imaging after administration of Clariscan, an iron oxide nanoparticle with large(More)
Myocardial perfusion images can be affected by the dark rim artifact. This study aimed to evaluate the effects of the spatial resolution and heart rate on the transmural extent of the artifact. Six pigs under anesthesia were scanned at 1.5T using an echo-planar imaging/fast gradient echo sequence with a nonselective saturation preparation pulse. Three(More)
We propose a method for restoring the underlying true signal in noisy functional images. The Nadaraya-Watson (NW) estimator described in, e.g., [1] is a classical nonparametric estimator for this problem. Since the true scene in many applications contains abrupt changes between pixels of different types, a modification of the NW estimator is needed. In the(More)
A simple two-compartment model was used to study the effects of water exchange on the signal produced by an inversion recovery prepared rapid gradient-echo sequence during the first passage of a low dose of an intravascular contrast agent. Water exchange at intermediate rates of exchange (1-10 Hz) between the vascular and extravascular spaces caused the(More)