ORCID

http://orcid.org/0000-0001-5932-0824

Date of Award

Spring 5-15-2022

Author's School

Graduate School of Arts and Sciences

Author's Department

Physics

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

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.

Language

English (en)

Chair and Committee

Tiezhi Zhang

Committee Members

Erik A. Henriksen

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