Photon-counting CT for dynamic lung perfusion: validation of a low-dose protocol in a porcine lung transplantation model

Objective Photon-counting CT (PCCT) combines improved dose efficiency with spectral imaging, enabling dynamic functional imaging at chest CT dose levels. Dual energy CT typically uses perfused blood volume (PBV) as a static perfusion surrogate. This study compared low-dose dynamic PCCT compared with reference-dose PCCT and static PBV imaging. Materials and methods Six minipigs with left lung transplants underwent dynamic perfusion imaging using PCCT at reference and low-dose settings, along with a static PBV scan. Perfusion metrics—Blood Flow Deconvolution (BFD), Mean Transit Time Deconvolution (MTTD), Flow Extraction Product (FEP), and Time to Start Deconvolution (TTSD)—were normalized and analyzed across six lung regions using Kruskal-Wallis tests and Bland-Altman analysis. Results Low-dose and reference-dose dynamic PCCT showed strong agreement across perfusion parameters (BVP bias: 0.03; BVD bias: 0.04), with no significant differences in BVP ( p = 0.995) or BVD ( p = 0.374). Kinetic metrics were stable across dose levels (all p > 0.2). While low-dose imaging showed slightly greater perfusion heterogeneity, BVP remained robust. Static PBV differed significantly from dynamic BVP (reference dose: p < 0.001; low-dose: p = 0.04). Left-right perfusion differences were detected in two animals by all methods. Estimated doses were 2.37 mSv (reference-dose) and 1.36 mSv (low-dose), comparable to chest CT (1.49 mSv) and below conventional CT perfusion (3–10 mSv). Conclusion Dynamic PCCT enables quantitative lung perfusion imaging at radiation doses comparable to standard chest CT. Low-dose dynamic PCCT shows strong agreement with reference-dose acquisitions, while dynamic parameters reveal functional differences not captured by static PBV imaging. Relevance statement Dynamic low-dose photon-counting computed tomography enables lung perfusion quantification at radiation doses comparable to standard chest CT, facilitating dose-efficient functional imaging in pulmonary disease. Key Points Low-dose PCCT (~ 1.36 mSv) is feasible, comparable to single chest CT (1.49 mSv). Strong agreement was seen between low- and reference-dose PCCT (BVP bias 0.03; BVD bias 0.04). Kinetic perfusion metrics remained stable across dose levels (all p > 0.2).