Date of Award

Spring 5-15-2022

Author's School

Graduate School of Arts and Sciences

Author's Department


Degree Name

Doctor of Philosophy (PhD)

Degree Type



Emerging distributed x-ray source technology enables new designs for x-ray imaging systems. The multi-pixel thermionic emission X-ray (MPTEX) source, a distributed x-ray source developed in our lab, was assembled and tested. With a multi-row CdTe photon-counting detector, forty-eight x-ray fan beams of MPTEX source were able to cover a 25-cm cross-sectional and 8-cm axial field of view. Tetrahedron-beam x-ray imaging techniques using MPTEX source were demonstrated.

Ultra-high dose rate radiotherapy or FLASH radiotherapy (RT) potentially can reduce normal tissue toxicity in radiation treatments. A compact irradiator that can deliver FLASH-RT treatments similar to conventional RT treatments is needed for preclinical studies. Based on our MPTEX source, we designed and optimized a ring-shaped x-ray small animal FLASH irradiator (SAFI) with 51 focal spots. The dose rate characteristics in a 4-cm cylindrical water phantom and operating power limitations of SAFI were discussed. Forward and inverse treatment planning, as well as an inverse-geometry CT using the SAFI circular sources, were demonstrated.

The power of MPTEX sources with a fixed anode is limited by the focal spot power density. We optimized the design of tungsten(W)-diamond target and predicted its performance in MPTEX sources via Monte Carlo and finite-element analysis simulations. The maximum tube power and x-ray output intensities were predicted for both transmission and reflection target configurations. We showed a significant tube power and x-ray output enhancement when using a W-diamond target with the optimal W film thickness. Furthermore, a fabricated W-diamond sample was tested in an experimental x-ray tube. It can be potentially used in the next version of MPTEX source.


English (en)

Chair and Committee

Tiezhi Zhang

Committee Members

Erik A. Henriksen

Available for download on Sunday, June 16, 2024

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