Inter-Institutional Quantification of Spectral Results with First-Generation Clinical Photon-Counting CT
Abstract
Purpose
Photon-counting CT (PCCT) incorporates detector technology that supports quantitative imaging in routine diagnostic evaluation by reducing scanner- and patient-specific effects, thereby enabling more reliable material quantification and characterization. Previous studies have demonstrated PCCT’s quantitative stability with tube voltage and dose as well as longitudinally. However, the quantitative consistency of spectral results across institutions has not been evaluated for PCCT.
Methods
To evaluate inter-institutional quantification of PCCT, four institutions with the same clinical PCCT (NAEOTOM Alpha, Siemens Healthineers) scanned a commercially available multi-energy CT phantom with tissue-mimicking and material-specific inserts. At each institution, three scans were performed in single-source mode at a tube voltage of 140 kVp and CTDIvol of 10 mGy. Virtual monoenergetic images (VMIs) from 40 to 190 keV, iodine maps, and virtual non-contrast maps (VNC) were analyzed to calculate the average and standard deviation of the error relative to the expected value for each institution and spectral result. To quantify inter-institutional variability, inter-institutional standard deviation was determined as the standard deviation of the error across institutions for each insert and spectral result.
Results
Across all inserts, VMI 70 keV exhibited errors of 6 ± 3, 4 ± 2, 10 ± 7, and 11 ± 8 HU for each institution, corresponding to an average inter-institutional standard deviation of 3 ± 1 HU across inserts. As keV increased from 50 to 150 keV, the average inter-institutional standard deviation across inserts decreased from 5 ± 2 to 2 ± 1 HU. For VNC and iodine maps, inter-institutional standard deviations averaged 2 ± 2 HU and 0.1 ± 0.1 mg/mL, respectively.
Conclusion
PCCT demonstrated comparable quantification across institutions for different insert materials and spectral results. The consistent inter-institutional quantification promotes widespread clinical utility and translation of quantitative imaging across a range of applications and establishes a foundation for multi-center clinical studies.