Magnetic resonance Diffusion-Weighted Imaging (DWI) analysis of the anatomical distribution characteristics and the imaging of lateral retropharyngeal lymph nodes

Purpose: The characteristics of lymph node distribution in the normal lateral retropharyngeal lymph nodes and the quantitative analysis of ADC value were explored by magnetic resonance imaging, which provides a reference for clinical identification of lymph node lesions in the lateral retropharyngeal lymph nodes. Methods: : A retrospective analysis was performed in our hospital from January 1, 2019 to January 1, 2021. A total of 920 patients were randomly selected for 1.5T MRI scans and they were divided into groups based on age and gender. The following analysis was performed：(1) Lymph node size and anatomical location in the retropharyngeal group; (2) Differences between gender and age; (3) Quantification of ADC values. Results: : A total of 3017 lateral retropharyngeal lymph nodes were counted, which were oval and irregular triangles, isointense on T1WI, high signal on T2WI, FS-FLAIR-T2WI, and DWI ( b = 1 000), and measured on ADC map, which can be unilateral or bilateral, with one or more lymph nodes. (1) The average value of the longest and short-axis diameters of lymph nodes in the retropharyngeal group was larger in children and adolescents (group A) than in adults (group B) and in female than in male; (2) The average number of lymph nodes in children and adolescents was higher than that in adults. Compared with the same age, there are more females than males. The comparison between the left and right position arrays showed no difference ( p = 0.645); (3) The number of lateral retropharyngeal lymph nodes with the longest diameter ≥ 10 mm was highest in the children and adolescent female group (B1), followed by children and adolescent male group (A1), adult male group (A2), adult female group (B2) and the difference was statistically significant ( p < 0.001); (4) There was no statistical significance between the groups of lymph nodes with short-axis diameter ≥ 10 mm; (5) When b = 1000 s/mm 2 , the ADC values of lateral retropharyngeal lymph nodes were (0.789 ± 0.179) × 10 -3 mm 2 /s to (0.819 ± 0.150) × 10 -3 mm 2 /s, the difference between groups was not statistically significant. Conclusions: : The number and size of lateral retropharyngeal lymph nodes are related to age and gender. There is no significant difference in the distribution of left and right positions. When b =1 000 s/mm 2 , the ADC values are different among the groups, but it is not statistically significant, which can be used as a basis for judging the nature of lymph nodes by magnetic resonance imaging.