MDCT for suspected appendicitis: effect of reconstruction section thickness on diagnostic accuracy, rate of appendiceal visualization, and reader confidence using axial images.

Abstract

The purpose of this study was to evaluate interpretative performance with different MDCT reconstruction parameters in adult patients with suspected appendicitis. MDCT scans of 212 adult patients obtained in an emergency department with a 64-MDCT scanner were prospectively collected. Acquisition technique included 24 x 1.2 mm detector configuration and IV contrast administration with or without oral contrast administration. Data sets were reconstructed with three techniques: 5 x 5 mm, 3 x 3 mm, and 2 x 1 mm (section thickness x interval). Each of the 212 sets of images (grouped by reconstruction technique) was reviewed retrospectively using axial sections by two independent readers blinded to diagnosis. Medical record review was conducted to identify patients with appendicitis. Visualization of the appendix, confidence in visualization, confidence for presence or absence of specific CT findings, diagnostic accuracy, and diagnostic confidence were compared across reconstruction techniques. Data were analyzed with simple and ordinal logistic regression with adjustment for multiple observations derived from each patient and for reader differences. Progressively thinner reconstruction section thickness was associated with a significant increase in the rate of visualization of the appendix (p < 0.001 for 5 x 5 vs 3 x 3; p = 0.03 for 3 x 3 vs 2 x 1), visualization confidence (p < 0.001 for 5 x 5 vs 3 x 3 and 3 x 3 vs 2 x 1), and confidence for presence or absence of findings. Seventeen subjects (8%) had appendicitis. Correctness of diagnosis was not significantly associated with reconstruction method. However, for correctly diagnosed cases interpreted as normal, impression confidence increased with progressively thinner section thickness (p < 0.001 for 5 x 5 vs 3 x 3 and 3 x 3 vs 2 x 1). In this investigation of contrast-enhanced MDCT of the appendix, visual ization of the appendix and confidence in interpretation of axial images progressively improved with use of thinner reconstruction sections.