Clinical Report: Long-Term Quantitative Stability of Photon-Counting CT
Overview
A two-year longitudinal study evaluated the quantitative stability of a first-generation clinical photon-counting CT (PCCT) scanner using a multi-energy phantom. Results demonstrated consistent quantitative accuracy and noise stability across multiple spectral reconstructions, despite software and hardware updates, supporting PCCT's reliability for longitudinal clinical imaging.
Background
Computed tomography (CT) is critical for follow-up and surveillance in oncology, infectious, chronic, and cardiovascular diseases. Photon-counting CT (PCCT) is an innovative technology that improves spectral imaging, contrast resolution, and reduces radiation dose compared to conventional CT. Since its clinical introduction in 2021, PCCT's enhanced quantitative capabilities have shown promise, but long-term stability and precision require thorough evaluation. This study addresses the need to assess PCCT's robustness over extended periods to ensure reliable longitudinal imaging.
Data Highlights
Parameter
Measurement
Time Points
Results
Scan Frequency
Weekly scans
Nov 2021 - Nov 2023 (~2 years)
Average 1.3 weeks between scans
Phantom Inserts
Adipose, brain, blood variants, iodine, calcium
Multiple inserts
Measured mean and noise values
Energy Levels
VMI at 40, 70, 100, 190 keV
All scans
Consistent quantitative values over time
Reconstruction
Quantum Iterative Reconstruction (QIR) levels 0 and 2
All scans
Noise stability assessed with and without denoising
Software Updates
Weeks 8, 35, 69
During study
No significant impact on quantitative accuracy
Hardware Updates
Weeks 8, 19, 80
During study
Maintained quantitative stability
Key Findings
PCCT demonstrated stable quantitative accuracy across multiple tissue- and material-specific inserts over two years.
Virtual monoenergetic images (VMI) at 40, 70, 100, and 190 keV showed minimal deviation from ground truth values throughout the study period.
Noise levels remained consistent with and without quantum iterative reconstruction, indicating reliable image quality over time.
Software updates improving cross-scatter correction did not adversely affect quantitative measurements.
Hardware modifications, including cooling and temperature management adjustments, did not compromise scanner stability.
Phantom-based longitudinal monitoring is effective for assessing PCCT system performance and reliability.
Clinical Implications
The demonstrated long-term quantitative stability of PCCT supports its use for longitudinal patient monitoring in oncology, infectious, chronic, and cardiovascular diseases. Clinicians can rely on PCCT's consistent spectral imaging and quantitative accuracy for detecting subtle changes over time, potentially improving disease surveillance and treatment response assessment. Additionally, the robustness against software and hardware changes reduces concerns about variability in serial imaging studies.
Conclusion
This two-year longitudinal analysis confirms that first-generation clinical PCCT systems maintain consistent quantitative accuracy and noise stability, reinforcing their reliability for clinical applications requiring precise longitudinal imaging. These findings support the broader adoption of PCCT technology in routine patient follow-up and surveillance.
References
Siemens Healthineers 2021 -- Introduction of Clinical PCCT System
Gammex Multi-energy CT Phantom -- Phantom Description and Use
Photon-Counting CT Literature 2021-2023 -- Quantitative Imaging Advances
by 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
