Characterizing the Automatic Tube Potential Selection Feature for a CT Simulator with the Mercury 4.0TM Phantom

Yuan, Li

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Year:: 2023
Contributor:: Yuan, Li (creator); Oumano, Michael (Advisor); Liu, Jian (Reader); Schwer, Michelle (Reader); Walsh, Edward (Reader); Brown University. Division of Biology and Medicine (sponsor)
Genre:: theses
Subject:: Tomography; Diagnostic imaging; Medical physics
Extent:: vii, 39 p.

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Abstract:: Objectives: To elaborate on the significance of enabling the automatic tube potential selection (ATPS) feature on Computed Tomography (CT) simulators. Furthermore, evaluate the effect of this change on optimal tube potential, radiation dose, and diagnostic quality with phantoms of various sizes. Propose the best approach to apply ATPS to routine CT scans from a radiation oncology perspective. Methods: Assessed the machine’s automated tube current modulation (ATCM) and analyzed the ATCM’s effect on image quality with the Mercury 4.0TM phantom. The five different diameter cylindrical sections of the phantom were scanned with a standard manually-selected 120 kilovoltage peak (kVp) protocol and an ATPS-enabled protocol, respectively. Radiation doses, contrast-to-noise ratios (CNRs), noise distributions, noise power spectra (NPS), and lesion detectabilities were compared between the standard and ATPS protocols. All phantom sections were also scanned with all available fixed tube potentials and the resultant changes in Hounsfield Unit (HU) values were compared. Results: The effective mAs has been modulated for different dimension of the sections by enabling the ATCM feature of the CT simulator. The tube potentials selected by the ATPS algorithm for the small and standard size sections (diameter < 360 mm) were less than 120 kV, while the largest section (diameter = 360 mm) resulted in a higher tube potential (140 kV). The radiation dose (CTDIvol) for all scans with ATPS were lower than the standard protocol by 2% to 33%. The variations of the HU values of the same materials acquired with different tube voltages are up to ±50 (for bone). Conclusions: In this thesis, we are the first to report AEC performance for any CT system at a kVp greater than 120. The lower potentials were automatically selected only for the phantom’s small and standard size sections. The magnitude of the CNR, the NPS plots, and the detectability of various materials showed the image quality was maintained. However, the variation of the HU value of the same materials scanned with different potentials was significant. A change of HU values > 50 HU for bone was observed for all kVp stations other than 120 kVp. The ATPS should therefore be disabled on this particular CT simulator unless accounted for via multiple kVp-specific electron density curves or other special software are applied.
Notes:: Thesis (Sc. M.)--Brown University, 2023

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Citation

Yuan, Li, "Characterizing the Automatic Tube Potential Selection Feature for a CT Simulator with the Mercury 4.0TM Phantom" (2023). Biology and Medicine Theses and Dissertations. Brown Digital Repository. Brown University Library. https://repository.library.brown.edu/studio/item/bdr:u25st3rx/

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Biology and Medicine Theses and Dissertations

Theses and Dissertations for the Biology and Medicine department.
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