3.0 T relaxation time measurements of human lymph nodes in adults with and without lymphatic insufficiency: Implications for magnetic resonance lymphatic imaging.

The purpose of this work was to quantify 3.0 T (i) T(1) and T(2) relaxation times of in vivo human lymph nodes (LNs) and (ii) LN relaxometry differences between healthy LNs and LNs from patients with lymphatic insufficiency secondary to breast cancer treatment-related lymphedema (BCRL). MR relaxometry was performed over bilateral axillary regions at 3.0 T in healthy female controls (105 LNs from 20 participants) and patients with BCRL (108 LNs from 20 participants). Quantitative T(1) maps were calculated using a multi-flip-angle (20, 40, 60°) method with B(1) correction (dual-T(R) method, T(R1) /T(R2)  = 30/130 ms), and T(2) maps using a multi-echo (T(E)  = 9-189 ms; 12 ms intervals) method. T(1) and T(2) were quantified in the LN cortex and hilum. A Mann-Whitney U-test was applied to compare LN relaxometry values between patients and controls (significance, two sided, p < 0.05). Linear regression was applied to evaluate how LN relaxometry varied with age, BMI, and clinical indicators of disease. LN substructure relaxation times (mean ± standard deviation) in healthy controls were T(1) cortex, 1435 ± 391 ms; T(1) hilum, 714 ± 123 ms; T(2) cortex, 102 ± 12 ms, and T(2) hilum, 119 ± 21 ms. T(1) of the LN cortex was significantly reduced in the contralateral axilla of BCRL patients compared with the axilla on the surgical side (p < 0.001) and compared with bilateral control values (p < 0.01). The LN cortex T(1) asymmetry discriminated cases from controls (p = 0.004) in a multiple linear regression, accounting for age and BMI. Human 3.0 T T(1) and T(2) relaxation times in axillary LNs were quantified for the first time in vivo. Measured values are relevant for optimizing acquisition parameters in anatomical lymphatic imaging sequences, and can serve as a reference for novel functional and molecular LN imaging methods that require quantitative knowledge of LN relaxation times.