Assessing the stability of photon-counting CT: insights from a 2-year longitudinal study

Leening P Liu; Pouyan Pasyar; Fang Liu; Quy Cao; Olivia F Sandvold; Martin V Rybertt; Pooyan Sahbaee; Russell T Shinohara; Harold I Litt; Peter B Noël

doi:10.1007/s00330-024-11244-y

Assessing the stability of photon-counting CT: insights from a 2-year longitudinal study

Eur Radiol. 2024 Dec 19. doi: 10.1007/s00330-024-11244-y. Online ahead of print.

Authors

Leening P Liu^{1

2}, Pouyan Pasyar^{3

4}, Fang Liu^{5

6}, Quy Cao^{5

6}, Olivia F Sandvold^{3

4}, Martin V Rybertt^{3

4}, Pooyan Sahbaee⁷, Russell T Shinohara^{5

6}, Harold I Litt³, Peter B Noël⁸

Affiliations

¹ Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA. leening.liu@pennmedicine.upenn.edu.
² Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA. leening.liu@pennmedicine.upenn.edu.
³ Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
⁴ Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA.
⁵ Penn Statistics in Imaging and Visualization Center, Department of Biostatistics, Epidemiology, and Informatics, University of Pennsylvania, Philadelphia, PA, USA.
⁶ Center for Biomedical Imaging Computing and Analytics, Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA.
⁷ Siemens Medical Solutions, Malvern, PA, USA.
⁸ Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA. peter.noel@pennmedicine.upenn.edu.

PMID: 39702629
DOI: 10.1007/s00330-024-11244-y

Abstract

Objective: Among the advancements in computed tomography (CT) technology, photon-counting computed tomography (PCCT) stands out as a significant innovation, providing superior spectral imaging capabilities while simultaneously reducing radiation exposure. Its long-term stability is important for clinical care, especially longitudinal studies, but is currently unknown. This study sets out to comprehensively analyze the long-term stability of a first-generation clinical PCCT scanner.

Methods: Over a 2-year period, from November 2021 to November 2023, we conducted weekly identical experiments utilizing the same multi-energy CT protocol. Throughout this period, notable software and hardware modifications were meticulously recorded. Various tissue-mimicking inserts were scanned weekly to rigorously assess the stability of Hounsfield Units (HU) and image noise in Virtual Monochromatic Images (VMIs) and iodine density maps.

Results: Spectral results consistently demonstrated the quantitative stability of PCCT. VMIs exhibited stable HU values, such as variation in relative error for VMI 70 keV measuring 0.11% and 0.30% for single-source and dual-source modes, respectively. Similarly, noise levels remained stable with slight fluctuations linked to software changes for VMI 40 and 70 keV that corresponded to changes of 8 and 1 HU, respectively. Furthermore, iodine density quantification maintained stability and showed significant improvement with software and hardware changes, especially in dual-source mode with nominal errors decreasing from 1.44 to 0.03 mg/mL.

Conclusion: This study provides the first long-term reproducibility assessment of quantitative PCCT imaging, highlighting its potential for the clinical arena.

Key points: Question Photon-counting CT (PCCT) provides critical spectral imaging for improved diagnostic accuracy, but its long-term quantitative stability over time is still unknown. Findings The clinical PCCT system demonstrated stable Hounsfield Units (HU) and image noise over 2 years, ensuring reliable quantitative imaging and improving diagnostic accuracy. Clinical relevance This study showcased the exceptional value of PCCT in diagnostic radiology, particularly for its application in longitudinal studies.

Keywords: CT; Photon-counting CT; Quantitative stability; Spectral CT.

Grants and funding

R01EB030494/EB/NIBIB NIH HHS/United States