• Journal of KIISE:Software and Applications
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• v.31 no.4
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• pp.411-419
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• 2004

When the imaging object rotates in image plane during MRI scan, its rotation causes phase error and non-uniform sampling to MRI signal. The model of the problem including phase error non-uniform sampling of MRI signal showed that the MRI signals corrupted by rotations about an arbitrary center and the origin in image plane are different in their phases. Therefore the following methods are presented to improve the quality of the MR image which includes the artifact. The first, assuming that the angle of 2-D rotational motion is already known and the position of 2-D rotational center is unknown, an algorithm to correct the artifact which is based on the phase correction is presented. The second, in case of 2-D rotational motion with unknown rotational center and unknown rotational angle, an algorithm is presented to correct the MRI artifact. At this case, the energy of an ideal MR image is minimum outside the boundary of the imaging object to estimate unknown motion parameters and the measured energy increases when the imaging object has an rotation. By using this property, an evaluation function is defined to estimate unknown values of rotational angle at each phase encoding step. Finally, the effectiveness of this presented techniques is shown by using a phantom image with simulated motion and a real image with 2-D translational shift and rotation.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.05
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• pp.139-142
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• 1996

A remotly controlled interactive magnetic resonance imaging (MRI) has been tried using the World Wide Web. For this purpose, an HTTP server is developed on the host computer of the MRI system. Video and audio conferencing capability is also included for the experiment. Using the developed system, MRI imaging has been successfully carried out at the Signal Processing Lab in the Kwangwoon University with the remote MRI system located at the Medical Image Research Center in the KAIST in Daejon.

• The Journal of the Korean bone and joint tumor society
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• v.8 no.3
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• pp.83-89
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• 2002

Purpose: To analyze the postoperative functional and radiographic follow-up results in patients who underwent percutaneous radiofrequency ablation therapy after the diagnosis of osteoid osteoma. Materials and Methods: Seven patients, who were clinically and radiographically diagnosed with osteoid osteoma from July 1999 to January 2001, and received percutaneous radiofrequency ablation therapy. The average follow-up period was 15.5 months(range, 8~25 months). For the diagnosis and accurate localization of the lesion, simple radiography, computed tomography and magnetic resonance imaging(MRI) were performed preoperatively. Simple radiographs and MRI were taken periodically for the follow-up studies. Results: In all 7 patients, symptoms completely disappeared within 3 days after the operation. The average period of hospitalization was 2.4 days, excluding 1 patient who needed an additional burn treatment. The average postoperative night and day pain scores were 1.8 and 1.3, respectively. The average vocational and recreational activity scores were 1 and 0.6, respectively. Conclusions: Satisfactory functional results were obtained with percutaneous radiofrequency ablation therapy for the elimination of osteoid osteoma. Compared to conventional treatment, the advantages of this therapy were short hospitalization period, no internal fixation and bone graft for preventing fracture, and no limitation of joint motion by long fixation period.