A better understanding of computed tomographic (CT) numbers of normal salivary glands might help make CT diagnosis more accurate. The CT numbers of the parotid and submandibular salivary glands were measured using both non-enhanced and enhanced CT images by setting a circular region of interest (ROI). The normal range of CT numbers, the difference between the CT numbers of right and left glands, and the correlation with age were all investigated. There was a close correlation between the CT numbers of right and left glands. No significant difference was seen between the average of right and left CT numbers in both glands, on either non-enhanced or enhanced CT images. The difference between right and left numbers on enhanced CT were larger than those on non-enhanced CT. A significant difference was seen between the CT numbers of the parotid and submandibular glands. A sex difference was seen on both non-enhanced and enhanced CT images in the parotid gland, while it was only seen on enhanced CT in the submandibular gland. The range as well as the mean of CT numbers in all cases of enhanced CT were larger than those of non-enhanced CT. CT numbers of the parotid glands tended to decrease proportionally with age, up to the age of 40 years; over the age of 40, no relationship could be detected. In the submandibular gland, the difference in the correlation coefficient was not significant between the two age groups. Further investigation into the factors affecting the CT numbers of normal glands is required before they can be used for diagnostic purposes.
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