Abstract 15060: New Diagnostic Method Using Latest Spectral Computed Tomography With Dual-Layer Detector to Diagnose Pulmonary Thromboembolism and Pulmonary Infarcted Tissue Changes

Abstract

Introduction: Spectral CT with a dual-layer detector generates CT images at any keV (range: 40-200) after ordinary acquisition using virtual monoenergetic settings (VMS). An appropriate keV improves the contrast of a pulmonary artery (PA) thrombus (PAT). On iodine no water (INW) display, areas with decreased PA blood flow are visualized. With effective atomic number display (Z effective), infarcted and normal lung tissues are distinguished. Hypothesis: Spectral CT improves the detection of PAT, areas with decreased PA blood flow, and infarcted lung tissue, increasing diagnostic accuracy. Methods: We performed enhanced 128 slice Spectral CT 7500 (Philips) scans with a dual-layer detector in 23 patients (11 males, 61±13 years) with clinically suspected PAT. VMS images at various keV values were created from spectral-based images. We developed an INW display to detect decrements in PA blood flow and also made Z effective displays to distinguish infarcted from normal lung tissue. We measured patent PA lumens, PAT, lung areas with decrements in PA flow and infarcted lung tissue. Results: 19 patients had PAT. Of the remaining 4 patients, two revealed decrements in PA flow on INW display and lung tissue changes on Z effective display. On a spectral profile analysis using images in the early phases using contrast, lower keV values were associated with markedly and slightly increased mean CT values for the patent PA lumen and PAT, respectively. Lower keV values were associated with markedly increased mean CT values for normal lung tissue, however, mean CT values were constant at various keV values for an area related to decrements in PA blood flow by INW display and also infarcted lung tissue by Z profile, simultaneously, respectively (Figure). Conclusions: A small PAT may be missed in enhanced CT. However, spectral CT can detect PAT, an area corresponding to decrements in PA blood flow on INW display, and also distinguish infarcted from normal lung tissue on a Z profile, simultaneously.