Maxillary air density measurements for differentiating between acute and chronic rhinosinusitis

OBJECTIVE. Maxillary sinus air-fluid levels and sinus opacification may appear similar in cases of acute and chronic rhinosinusitis. Our aim was to evaluate whether air density analysis in addition to air-fluid level can be used as a metric to differentiate between cases of acute and chronic rhinosinusitis. SUBJECTS AND METHODS. A prospective study of three patient groups (n = 73) who underwent sinus CT was performed. A study group composed of 23 patients with clinical acute rhinosinusitis was compared with two different control groups (one with chronic rhinosinusitis and the other with healthy sinuses) with 25 patients in each. In each case air density within the maxillary sinus was measured using a region of interest of 1 cm2, 0.5 cm away from the sinus wall. The mean and SD of air density of each maxillary sinus were calculated from five sequential CT slices. We compared the results of each group using a paired Student t test and analysis of variance. RESULTS. Mean air density was significantly higher in the acutely inflamed sinuses compared with chronic sinusitis and healthy aerated sinuses (-846.6 vs -980 and -975.8 HU, respectively; p < 0.05). Sinus air density SD was greater in the acutely inflamed sinus than in chronic sinusitis and healthy sinuses (78.3 vs 17.9 and 6.8 HU, respectively; p < 0.05). CONCLUSION. Increased sinus air density and heterogeneity may help differentiate acute from chronic rhinosinusitis.