| Objective:By using MRI technique, measure the normal value of the olfactory bulb (OB) volume of the healthy Chinese adults and discuss its variation with age and evaluate whether measuring olfactory bulb volume by MRI can be regarded as one of the important indicators for human olfactory functions.methods:One hundred and three healthy right-handed subjets(49 men, 54 women; ages ranging from 20 to 69) (mean age of 43.8±13.9) without any diseases which might cause smell dysfunction, were randomly selected to participate in our study for measuring OB volumes and evaluating the correlation between OB volume and age as well as between OB volume and olfactory functions. All subjects received a volumetric scan of the whole brain (MRI) and lateralized olfactory tests (Sniffin'Sticks).MRI data acquisition included axial plane T2-weighted fast spin-echo images and sagittal plane three-dimensional fast spoiled gradient-recalled sequence. Volumetric measurement of the OBT was performed by manual segmentation of the consecutive 1-mm thick coronal slices through the OBT in the left hemisphere and the right one separately. We used the "sudden" to segregate OB from OT and Sniffin'Sticks to judge of olfactory functions involving odor threshold, odor discrimination, and odor identification, which are collectively called TDI scores.Results:The left and right absolute OB volumes of men were 88.656±29.363cm3 and 92.543±30.632cm3; The left and right absolute OB volumes of women were 74.837±19.336cm3 and 72.634±20.707cm3.We confirmed the significant negative correlations between age and OB absolute volume(left:r=-0.237,p=0.017;right:r=-0.275, p=0.005).That is to say, as age went up, OB volume would become small. Furthermore, there was remarkable correlation between OB absolute volume and olfactory functions correspondingly(left:r=0.223, p=0.024; right:r=0.212, p=0.032). However, there was no correlation not only between left and right OBT absolute volume and age but also between OBT absolute volume and olfactory functions(p=0.153, p=0.223; p=0.024, p=0.032). There was correlation between OB or OBT relative volume and years as well as olfactory function. The males'absolute OB volumes of either left-side or right-side were respectively larger than females', and the differences reached statistical significance(t=2.849, p=0.006;t=3.794,p< 0.001), but there were no significant differences of relative OB volumes(100×absolute volumetric value/whole cerebral white matter) between males and females in left-side and right-side.(p=0.324; p=0.082). There were no significant differences of absolute OB volumes between left-side and right-side, but the right-side relative OB volumes were larger than the left-side one and the differences reached statistical significance(t=3.794,p=0.001).Conclusion:The present study provided the normal range of a relatively large sample size of the OB volumes in vivo MRI measurements among healthy Chinese adults, and found that the physiological variation of OB volumes decreased with age; these data confirmed that there were no significant differences of OB volumes between males and females in congenital development and also showed the right side predominance within the olfactory system. In agreement with previous research of foreign scholars, the study confirmed the correlation between OB volume and olfactory functions and OB volumes measured MRI were expected to be a gauge of olfactory functions. These data of different decades will be helpful in early diagnoses of diseases relevant to olfaction and their prognoses and follow-up investigations.
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