Diaphragm Thickness Measurement in Computed Tomography: Intra- and Inter-Observer Agreement

Abstract

Introduction: Diaphragm thickness (DT) measurement in computed tomography (CT) has become popular in recent years. Our aim was to assess the intraand inter-observer agreement of DT measurement and to investigate the best points for DT assessment in CT based on the most reliable measurement. Methods: Thoraco-abdominal CT angiography scans of 44 patients (23 males, mean age: 49.9±17.8 years) were retrospectively evaluated. All of the CT images were evaluated independently by four radiologists. Each observer evaluated images twice to assess intra-observer reproducibility. On both axial and coronal reconstructed CT images, the crura of 88 hemidiaphragms were measured at five different points. A p value less than 0.05 was considered to indicate statistical significance. Intraand inter-observer agreement was evaluated by using intraclass correlation coefficient (ICC) scores with a 95% confidence interval. Results: In intra-observer analysis, ICC scores demonstrated substantial to almost perfect agreement for all measurements (ICC score range: 0.758-1). When we analyzed the inter-observer agreement, there was a moderate to almost perfect agreement for each measurement point (ICC score range: 0.523-0.895). All axial measurements showed the highest inter-observer agreement (ICC scores were 0.926 and 0.886 for first and second measurements, respectively). The maximum interand intra-observer agreement for single point DT measurements were found in maximum DT at the level of the origin of the celiac artery and in anterior DT at the level of the upper part of the L1 vertebral body. Conclusion: CT is a reliable tool DT measurement with excellent intraand inter-observer agreement.