67-4

21/90

PTE: pulmonary thromboembolism. Unenhanced CT (+), patients who underwent enhanced and unenhanced CT; Unenhanced CT (-): patients who underwent only enhanced CT (not unenhanced CT); Central type: clot in the pulmonary trunk or main, lobar, and segmental pulmonary arteries; Peripheral type: clot in the subsegmental and other peripheral arteries; Hyperdense lumen sign (+): the presence of a hyperdense lumen sign; Hyperdense lumen sign (-): the absence of a hyperdense lumen sign.patient’s hematocrit (Ht) and hemoglobin (Hb) levels4, 5). Therefore, we also assessed the ratio of the attenuation value of thrombus (T) to Hb (T/Hb ratio), Ht (T/Ht ratio), and PA (T/P ratio). Receiver operating characteristic (ROC) analysis was performed to set the threshold of the diag-nostic performance of unenhanced CT in detecting PTE. Sensitivity, specificity, positive and negative predictive values (PPV and NPV, respectively), and positive and negative likelihood ratios (PLR and NLR, respectively) as well as their 95% confi-dence intervals (CIs) for the diagnosis of PTE were calculated for each unenhanced CT finding. Continuous variables were tested by t-test or Mann-Whitney U test, discontinuous variables were tested by Fisher’s exact test, and p-values <0.05 were considered significant. All statistical analyses were performed using EZR® (Saitama Medical Center, Jichi Medical University, Saitama, Japan). This study protocol was approved by the ethics committee of Showa General Hospital (approval number REC-240m). All patients provided written Figure 4　Patient enrollment protocolinformed consent.A total of 260 patients were enrolled in the study; 200 were diagnosed with PTE and 60 were not, confirmed based on enhanced CT examination. Of the 200 patients with PTE, 151 did not undergo unenhanced CT examination and were excluded. Among the 49 patients with PTE who underwent both enhanced and unenhanced CT, 33 were of the central type, of whom 9 showed a hyperdense lumen sign and were also excluded. From the 60 patients in the non-PTE group, 17 underwent both enhanced and unenhanced CT, of whom 1 showed a hyperdense lumen sign and was excluded. After applying the exclusion criteria, a total of 40 patients were included in the analyses. Twenty-four of these patients had an acute central PTE (thrombi group), and sixteen had no thrombi in the PA (non-thrombi group) (Figure 4). There was no significant difference in age, renal function, or Hb values at the time of imaging between the two groups. D-dimer, fibrin, and fibrinogen degenera-341Results