[The investigation of the structures in the ethmoidal air cells on CT].

This paper reports a study on the pneumatization of the ethmoidal air cells using CT scans of 50 normal adults and 50 patients with the ethmoidal sinusitis. Transverse tomographic images 10 mm above the OM line were analyzed and investigated, based on the results obtained by the preliminary study of transverse and reconstructed sagittal tomographic images. The measurements were done for the longitudinal and lateral distance, total and individual areas occupied by ethmoidal air cell. The arrangement of air cells, site of the largest cell and the number of opaque cells and the cells with thickened mucosa were also studied. The results are as follows; 1) By normal ethmoidal cells, the total area by this transverse plane was 4.45 +/- 1.62 cm2, lateral distance 1.73 +/- 0.58 cm, longitudinal distance 4.46 +/- 0.92 cm, and the number of cells 6.4 +/- 3.0. The average area of each cell was 0.73 +/- 0.42 cm2 and the largest was 1.46 +/- 0.64 cm2. 2) The correlation with the total area was highest for the product of lateral X longitudinal distances (coefficient of correlation: 0.73), and the coefficient of correlation of the lateral distance was 0.70. 3) The single line type cell arrangement and the dual line cell arrangement were observed in many cases. 4) The largest cell was located in the posterior part of the ethmoid in many cases. 5) The measured values in cases with ethmoidal sinusitis were not significantly different from those of normal ethmoid cell. However, the product of the lateral X longitudinal distances was significantly smaller (p less than 0.01) in sinusitis group. 6) In compared studies of sinusitis cases with less than one year and more than one year affections, there were no significant differences in the measured distances. However, opaque cells were commoner in cases with more than one year affections, and cells with thickened mucosa were more common in those with less than one year, and the differences were significant. 7) Correlation coefficient of the total area of the ethmoidal air cells between the transverse image and the reconstructed sagittal image was 0.65.