CT scan attenuation value measurement as a tool for differential diagnosis between empyema, haemothorax and hydrothorax

Abstract

Aims and objectives Fluid in the pleural cavity is a common clinical problem with many potential causes. Despite the clinical and radiological findings providing important data about the cause(s) of content in the pleural cavity, tube thoracostomy is still required to relieve the pressure and characterize the fluid. These procedures could be avoided by applying a non-invasive method such as measurement of fluid CT attenuation values (CT - AV). Aim of the study was to evaluate CT attenuation values as a diagnostic tool to distinguish between hydrothorax, pyothorax and haemothorax. Methods and materials Fig. 1: 44 year old patient with right pyothorax and empyema. CT scan shows separated... During period 2012-2017 for observational study we reviewed 89 patient chest CT scans performed. Patients with the diagnosis of either haemothorax, pyothorax or hydrothorax were included. In every CT scan (before and after intravenous contrast media administration) we located three slices with the largest pleural effusion volume and measured the attenuation values in Hounsfield Units (HU) using the circular or ellipse region of interest (ROI) tool to mark the area containing only the fluid. We situated the ROI, so the measurements would not include bone, fat, lung, thickened pleural tissue or air (Fig.1). For statistical analysis, we recorded and used the mean of three attenuation values. We analysed all data using IBM SPSS Statistics v. 23.0. Normally distributed data was expressed as the mean value (95% confidence intervals) and non-normally distributed data as the median (minimum - maximum values). The Scheffe method in the one-way analysis of variances (ANOVA) was used to assess the differences of normally distributed attenuation values between haemothorax, pyothorax, and hydrothorax groups. We calculated the mean CT - AV for study participants and evaluated the accuracy to distinguish pleural contents between haemothorax, [...]