Objective  Analyse the patterns of physiological uptake of ¹⁸F-fluorodeoxyglucose (FDG) in the lumbar vertebral bodies of adults.

Methods  A retrospective analysis was performed for 323 healthy adults who underwent ¹⁸F-FDG PET/CT examination at the First Hospital of Shanxi Medical University from June 2010 to June 2018. Among the participants, there were 161 males and 162 females, with an average age of 54.8 ± 13.9 years, spanning from 30 to 78 years. The subjects were categorised into 30~39 year-old group, 40~49 year-old group, 50~59 year-old group, 60~69 year-old group, and 70~79 year-old group according to their age groups. The number of males and females in each group were 30 and 30, 36 and 40, 31 and30, 32 and 30, and 32 and 32, respectively. The regions of interest were delineated on the lumbar 2, lumbar 3 and lumbar 4 vertebrae, and their mean standardized uptake value (SUV_mean) were measured. Lumbar vertebral bone marrow SUV_mean, defined as the average of these three vertebral bodies, was used to indicate the degree of ¹⁸F-FDG uptake of the lumbar vertebral bone marrow. Pearson or Spearman rank correlation analysis was employed to assess the correlation between participants' age and SUV_mean. Additionally, differences in SUV_mean among various age and gender groups were compared, with within-group comparisons conducted using independent samples t-test or Mann-Whitney U test, and between-group comparisons performed using the Kruskal-Wallis H test and the Bonferroni method.

Results  The lumbar vertebral bone marrow SUV_mean were negatively correlated with age in all participants, males and females (r=−0.520, −0.451、−0.579, all P<0.001), but SUV_mean values did not decrease uniformly and linearly with age. Among female participants, the comparison of lumbar vertebral bone marrow SUV_mean across various age groups revealed that the 50~59 year-old group was lower than that of the 40~49 year-old group, and the 70~79 year-old group was lower than that of the 60~69 year-old group, with both differences being statistically significant (H=2.848, 3.114, both P<0.05). In contrast, between the 30~39 year-old group and the 40~49 year-old group, as well as between the 50~59 year-old group and the 60~69 year-old group, two plateau periods were observed, where the lumbar vertebral bone marrow SUV_mean did not decrease with age (H=0.371, 0.220, both P>0.05). Among male participants, the lumbar vertebral bone marrow SUV_mean of the 70~79 year-old group was lower than that of the 60~69 year-old group, and the difference was statistically significant (H=3.210, P<0.05). There was no significant difference among the other adjacent age groups (H=1.631、0.724、0.585, all P>0.05). The differences in the lumbar vertebral bone marrow SUV_mean between males and females under 50 years old (30~39 year-old group and 40~49 year-old group) were statistically significant (Z=−2.204, −2.918, both P<0.05). However, in the age groups of 50 years and above (50~59 year-old group 、60~69 year-old group and 70~79 year-old group), the differences in the lumbar vertebral bone marrow SUV_mean between males and females were not statistically significant (Z=−0.483, −0.592, −0.847, all P>0.05).

Conclusion Physiological uptake of ¹⁸F-FDG in adult lumbar vertebral bone marrow decreases with age but does not decline uniformly and linearly, and is slightly different in males and females.