Quantification of X-ray opacity of the maxillary sinus in the Waters' view.

Plain X-ray filming such as that in the Waters' view is a simple and inexpensive method used in daily practice to briefly evaluate the severity of inflammation of the paranasal sinuses. The maxillary sinus is the largest and simplest in shape among all sinuses and is usually clearly observed on a film in the Waters' view. We attempted to obtain a quantitative index of the X-ray opacity of the maxillary sinus using X-ray films in the Waters' view. A copper wedge was placed to the left side of the subject's face and was filmed simultaneously. The X-ray film was digitized with an image digitizer. The X-ray density of each pixel was then converted to an absolute value for the copper thickness with a medical image processor. The mean pixel value in the region of interest at the maxillary sinus (M(R)) and that at the ipsilateral orbit (O) were determined. The difference, M(R) - O, was found to have a significant correlation with the average visual grading of the severity of inflammation of the maxillary sinus by 10 otolaryngologists. Thus M(R) - O Can serve as an objective measure of the X-ray opacity of the maxillary sinus. The use of this index during the follow-up period is advisable, especially in children, because of greatly reduced amount of X-ray exposure compared with that in computed tomography.