Biomedical subjects

Evelyn A Firle

Publications and source records attributed to Evelyn A Firle.

3 recordsLinked to original sources

PubMed2006

Localizing calcifications in cardiac CT data sets using a new vessel segmentation approach.

The new generation of multislice computed tomography (CT) scanners allows for the acquisition of high-resolution images of the heart. Based on that image data, the heart can be analyzed in a noninvasive way-improving the diagnosis of cardiovascular malfunctions on one hand, and the planning of an eventually necessary intervention on the other. One important parameter for the evaluation of the severity of a coronary artery disease is the number and localization of calcifications (hard plaques). This work presents a method for localizing these calcifications by employing a newly developed vessel segmentation approach. This extraction technique has been developed for, and tested with, contrast-enhanced CT data sets of the heart. The algorithm provides enough information to compute the vessel diameter along the extracted segment. An approach for automatically detecting calcified regions that combines diameter information and gray value analysis is presented. In addition, specially adapted methods for the visualization of these analysis results are described.

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PubMed2006

Advantages and limitations of prospective head motion compensation for MRI using an optical motion tracking device.

RATIONALE AND OBJECTIVES: Subject motion appears to be a limiting factor in numerous magnetic resonance (MR) imaging (MRI) applications. In particular, head tremor, which often accompanies stroke, may render certain high-resolution two- (2D) and three-dimensional (3D) techniques inapplicable. The reason for that is head movement during acquisition. The study objective is to achieve a method able to compensate for complete motion during data acquisition. The method should be usable for every sequence and easily implemented on different MR scanners. MATERIALS AND METHODS: The possibility of interfacing the MR scanner with an external optical motion-tracking system capable of determining the object's position with submillimeter accuracy and an update rate of 60 Hz is shown. Movement information on the object position (head) is used to compensate for motion in real time by updating the field of view (FOV) by recalculating the gradients and radiofrequency parameter of the MR scanner during acquisition of k-space data, based on tracking data. RESULTS: Results of rotation phantom, in vivo experiments, and implementation of three different MRI sequences, 2D spin echo, 3D gradient echo, and echo planar imaging, are presented. Finally, the proposed method is compared with the prospective motion correction software available on the scanner software. CONCLUSION: A prospective motion correction method that works in real time only by updating the FOV of the MR scanner is presented. Results show the feasibility of using an external optical motion-tracking system to compensate for strong and fast subject motion during acquisition.

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PubMed2005

Prospective head motion compensation for MRI by updating the gradients and radio frequency during data acquisition.

Subject motion appears to be a limiting factor in numerous magnetic resonance imaging (MRI) applications. For head imaging the subject's ability to maintain the same head position for a considerable period of time places restrictions on the total acquisition time. For healthy individuals this time typically does not exceed 10 minutes and may be considerably reduced in case of pathology. In particular, head tremor, which often accompanies stroke, may render certain high-resolution 2D and 3D techniques inapplicable. Several navigator techniques have been proposed to circumvent the subject motion problem. The most suitable for head imaging appears to be the orbital or spherical navigator methods. Navigators, however, not only lengthen the measurement because of the time required for acquisition of the position information, but also require additional excitation radio frequency (RF) pulses to be incorporated into the sequence timing, which disturbs the steady state. Here we demonstrate the possibility of interfacing the MR scanner with an external optical motion tracking system, capable of determining the object's position with sub-millimeter accuracy and an update rate of 60Hz. The movement information on the object position (head) is used to compensate the motion in real time. This is done by updating the field of view (FOV) by recalculating the gradients and the RF-parameter of the MRI tomograph during the acquisition of k-space data based on the tracking data. Results of rotation phantom, in vivo experiments and the implementation in two different MRI sequences are presented.

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