Clinical Significance of Late Phase of Lung Perfusion Blood Volume (Lung Perfusion Blood Volume) Quantified by Dual-Energy Computed Tomography in Patients With Pulmonary Thromboembolism

Purpose: Using dual-energy computed tomography (DECT), we quantified the lung perfusion blood volume (PBV) in the late phase, which may reflect both the pulmonary artery and systemic collateral flow. We then investigated the clinical significance of latephase lung PBV values. Materials and Methods: We retrospectively studied 206 patients (266 scans) who underwent early-phase and late-phase DECT. The patients were divided into 2 groups depending on whether or not they had pulmonary thromboembolism (PTE) (n = 94 and 112). Patients with PTE were further divided into 2 subgroups, depending on whether they had acute PTE or chronic PTE (n = 66 and 28). Pulmonary artery enhancement (PA(enh)) was measured on DECT. We then calculated the [lung PBV/PA(enh)] ratio in all patients during both the early and late phases for adjustment of timing. Results: The [late-phase lung PBV/PA(enh)] ratio was 0.092 +/- 0.029 in the group with PTE and 0.108 +/- 0.030 in the group without PTE, showing a significant difference between the 2 groups (P < 0.0001). The [early-phase lung PBV values/PA(enh)]/[late-phase lung PBV values/PA(enh)] ratio was 0.68 +/- 0.19 and 0.84 +/- 0.20, respectively, also showing a significant difference between the 2 groups (P < 0.0001). Finally, the [early-phase lung PBV/PA(enh)]/[late-phase lung PBV/PA(enh)] ratio was 0.71 +/- 0.19 in patients with acute PTE and 0.56 +/- 0.16 in patients with chronic PTE, and there was a significant difference between these 2 subgroups (P = 0.0004). Conclusions: It may be useful to determine late-phase lung PBV values in patients with PTE, because this parameter may reflect the systemic collateral flow, which is increased in chronic PTE.