Title:

Multiphysics Simulation Study for Real-Time 4D CT Development

Speaker:

Dr. Hank Lee

Affiliation:

Interim Chair of the Nuclear Engineering Department at the University of New Mexico

When:

Thursday, October 23, 2025 at 11:00:00 AM   Add to Calendar

Where:

Boggs Building, Room 3-47

Host:

Shaheen Dewji
shaheen.dewji@gatech.edu

Abstract

To perform computed tomography imaging in real time, the rotation time for the gantry must be as low as 30 ms. The gantry rotation time in the conventional computed tomography architecture is limited to approximately 300 ms because of mechanical and material limitations. To address this problem, researchers are developing a stationary architecture where the mechanical rotation of the gantry is replicated electronically. This electronic replication is accomplished using two stationary, separate arrays: one for distributed x-ray sources and the other for detectors. The open design challenge is to develop tightly packed, yet high-intensity, distributed x-ray sources. The work presented herein shows our updated design for such distributed x-ray sources. We utilize an unconventional rotating cylindrical anode, a hot-cathode emitter with a focusing cup for grid-switching, and electromagnets for controlling the electron beam. We report our results from a series of physics-based simulation studies on the thermal analysis of the cylindrical anode and electron beam optics for switching, steering, and focusing a high-energy electron beam. We found that the cylindrical anode was capable of withstanding thermal loads expected from a typical cardiac computed tomography scan without degradation of the tungsten target on the anode. The rotation of the cylindrical anode proved to be effective at dissipating the heat generated from electron impact. Three different methods of electron beam scanning were studied, and we determined that using a step-and-shoot method performed better than continuous sweeping. The electron beam optics studies centered around using magnetic fields to steer and focus a high-energy electron beam and electrostatic fields to switch the electron beam on and off. We found that the grid switching technique could allow the focusing cup to stop the flow of electrons from the cathode, effectively turning the electron beam on and off. A dipole magnet was able to steer the electron beam across the length of the cylindrical anode, which was approximately 450 mm in our design. A quadrupole magnet was found to be able to dynamically focus the electron beam to our desired focal spot size 1 mm x 7 mm on the anode surface, 1 mm x 1mm projected.

Biography

Dr. Hank Lee is a Professor and Interim Chair of the Nuclear Engineering Department at the University of New Mexico. He received his B.S. and M.S. in Nuclear Engineering from Seoul National University in Korea and his Ph.D. in Nuclear Engineering from the University of California at Berkeley. He was a founding faculty member of the Department of Biomedical Engineering at the Catholic University of Korea. He joined the Nuclear Engineering Program at Missouri University of Science and Technology in 2009 and chaired the program for six years. In 2020, he joined the Nuclear Engineering Department at UNM as the Chair.

Notes

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