Normative Measurements and Apparent Diffusion Coefficient Values of Parotid Lymph Nodes on Magnetic Resonance Imaging

To determine the morphological features and apparent diffusion coefficient (ADC) values of normal intraparotid lymph nodes (IPLNs) obtained from the MRI examination.

Cross-sectional descriptive study.

Health Sciences University, Diskapi Yildirim Beyazit Training and Research Hospital, Department of Radiology, Ankara, Turkey, from January 2018 to December 2021.

The study included 232 patients who underwent neck MRI examination. The long axis diameter (LAD) was measured as the largest diameter of the IPLN, and the short axis diameter (SAD) was measured perpendicular to the LAD. ADC measurements were undertaken by placing the largest region of interest suitable for the size of the IPLNs.

A total of 394 lymph nodes were evaluated. The median LAD and SAD of the lymph nodes were 5.50 (2.50) mm and 3.50 (2.00) mm, respectively. The LAD was 9 mm or lower in 95.7% of the lymph nodes; the SAD was 6 mm or lower in 94.7%. The ADC map was evaluated in 275 IPLNs, with the median ADC value being calculated as 0.77(0.18)x10-3 mm2/s. The ADC value was 1.05x10-3 mm2/s or lower in 96.3% of the lymph nodes.

A SAD of 6 mm; and a LAD of 9 mm could be used as normalcy criteria in IPLNs. Normal IPLNs may have an ADC of 1.05x10-3 mm2/s or lower. Considering that benign IPLNs may have low ADC values, those can prevent false-positive results in terms of malignancy.

Parotid glands, Lymph nodes, Magnetic resonance imaging, Apparent diffusion coefficient.