Room temperature semiconductor detector performance enhancement for multi-energy spect imaging system development and its application in alpha emitter radiopharmaceutical therapy

Yang, Can

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https://hdl.handle.net/2142/125787 Copy

Description

Title

Room temperature semiconductor detector performance enhancement for multi-energy spect imaging system development and its application in alpha emitter radiopharmaceutical therapy

Author(s)

Yang, Can

Issue Date

2024-07-10

Director of Research (if dissertation) or Advisor (if thesis)

Meng, Ling-Jian

Doctoral Committee Chair(s)

Meng, Ling-Jian

Committee Member(s)

• Fulvio, Angela Di
• Du, Yong
• Uddin, Rizwan

Department of Study

Nuclear, Plasma, & Rad Engr

Discipline

Nuclear, Plasma, Radiolgc Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• SPECT
• CZT
• CdTe
• High resolution
• Performance Enhancement

Abstract

Single Photon Emission Computed Tomography (SPECT) has traditionally played an essential role in nuclear medicine imaging. However, conventional SPECT systems, primarily reliant on scintillation detectors, have limitations, such as low energy resolution and sensitivity to environmental conditions, resulting in higher imaging noise and maintenance costs. The emergence of room temperature semiconductor detectors, such as cadmium zinc telluride (CZT), cadmium telluride (CdTe), and CsPbBr3, coupled with machine learning techniques, offers a unique opportunity to revolutionize multi-energy SPECT imaging providing the opportunity to image multiple radionuclides simultaneously. Despite the superior energy resolution of room temperature semiconductors compared to scintillators, in small pixelated CdTe/CZT detectors, energy resolution and detector sensitivity are degraded because of charge sharing and charge loss. In this dissertation, a charge-sharing reconstruction algorithm is proposed and applied to the small pixel CdTe/CZT detector to recover the energy deposition and position information. The implementation of this algorithm yields improvements in both energy resolution by recovering the charge loss and spatial resolution by sub-pixel positioning. Like high energy resolution CdTe/CZT detector, CsPbBr3 perovskite has been investigated as a promising room-temperature semiconductor detector material for next-generation gamma-ray sensors. Despite its potential, current CsPbBr3 detectors face challenges such as material defects, fabrication imperfections, and electric field inhomogeneity, all of which contribute to the detector's spectral performance degradation. A waveform clustering method is proposed to improve the planar and guard ring CsPbBr3 detector energy resolution and provide a potential way to investigate detector physics. Notably, the CsPbBr3 guard-ring detector exhibits a Full Width Half Maximum (FWHM) of 1.4% at 662keV post-correction compared to the original 5.4% before correction. These performance enhancements with pixelated CdTe/CZT detector and CsPbBr3 detector serve as the foundation of a high-resolution SPECT imaging system. Exploiting the capabilities of pixelated CdTe/CZT detectors, a simulation of the Intraoperative SPECT (I-SPECT) system is conducted, featuring a transformable system geometry to accommodate SPECT/CT imaging scenarios. The I-SPECT system achieves a <6 mm spatial resolution, and a cardiac phantom simulation study was performed to demonstrate the system imaging capability under full ring coverage and 270 degrees angular coverage. Moreover, a system focusing on high energy/spatial resolution preclinical imaging target, the Alpha-SPECT-Mini system, was fully developed and evaluated based on 24 1-mm CdTe detectors with 96 pinholes as the inverted compound eye design. The Alpha-SPECT-Mini system achieves a spatial resolution of <0.75 mm at 140 keV. Spectral optimization procedures, including dynamic energy windowing, energy-specific scattering correction, and charge-sharing reconstruction, are proposed and performed on the system imaging studies. As one of the major imaging applications of multi-energy SPECT systems, alpha-emitter radiopharmaceutical therapy (α-RPT) has been demonstrated as a promising therapy modality for cancer treatment. However, the low-dose administration makes imaging of Ac-225 or other alpha-emitters challenging. We have carried out in-phantom, ex-vivo, and in-vivo mice studies to demonstrate the effectiveness of spectral correction techniques. With the spectral optimization procedures, decay and washout of Ac-225 and its daughters in the tumor are demonstrated with 1, 4, and 6 days post-administration imaging results. Furthermore, a comparative analysis of kidney and tumor imaging of Ac-225 and its daughters illustrates one of the significant migration patterns of the Ac-225 decay products. In conclusion, energy and spatial resolution enhancement algorithms for room-temperature semiconductor detectors and high-resolution SPECT systems were designed, developed, and evaluated in this dissertation. The sub-keV intrinsic energy resolution, <6 mm resolution in the clinical SPECT system and <0.75 mm in the preclinical SPECT system, allow for precise differentiation of gamma-ray energies from various radionuclides, improving accuracy in imaging and quantification. This capability enables imaging studies of complex radiopharmaceuticals and targeted therapies to optimize their protocols and understanding further.

Graduation Semester

2024-08

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/125787

Copyright and License Information

Copyright 2024 Can Yang

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