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Assesment of subtraction CT scan with injection in pulmonary embolism diagnosis

Introduction: Pulmonary embolism (PE) is a common and potentially severe disease. The diagnosis is most often performed by post-contrast computed tomography (CT). The purpose of this study was to assess a new CT scan technique, the lung subtraction iodine mapping (LSIM) for the diagnosis of PE.

Materials and Methods: A prospective monocentric study was conducted between January 2018 and August 2019 including patients with PE suspicion. All CT scans were performed with LSIM protocole. January 2018 and August 2019. The acquisition protocol consisted of a low-dose pre-contrast scan followed by an arterial contrast-enhanced scan. By subtraction between pre and post contrast acquisition, color map representing iodine local concentration were generated automatically. Density measurements in Region of Interest (ROI) were carried out in pulmonary zones with PE and compared to healthy pulmonary zones.

Results: Sixty-one patients were included (37 men, 24 females, mean age 67 year-old, range 30-91 year-old). Twelve of them had a PE (8 men, 4 females, mean age 65, range 46-91 year-old), for corresponding to a total of 24 areas measured. Compared to the non PE zones, a significant decrease of density was observed in the PE zones (mean difference 37 UH, confidence interval of{18.5-55.55}, p < 0.001). The density in the non infarcted zones in the group of PE was not different than the density in the control group without PE.

Conclusion: The LSIM technique might help the diagnosis of PE by showing hypodensity in zones of PE compared to normal zones.