Characterization of ex vivo healthy human axillary lymph nodes with high resolution 7 Tesla MRI

Objective: To characterize ex vivo healthy human axillary lymph nodes on 7 Tesla MRI and to correlate the findings with pathological analysis as a first step towards non-invasive staging of breast cancer patients in the future. Methods: Four axillary lymph node dissection (ALND) specimens from 2 autopsy patients, who had no cancer, were examined on a clinical 7 Tesla MRI system. For morphological analysis a 3D T1-weighted fat-suppressed fast-field-echo [isotropic resolution 180 μm] was acquired. For quantitative analyses 2D T1-, 3D T2-, T2*- and diffusion-weighted images were acquired. The ALNDs were mapped and stained for precise correlation of MRI to pathology. Nodes were sliced in 3 μm sections, Haematoxylin & Eosin stained, and examined by an experienced pathologist. Results: MRI detected all 45 nodes and 6 additional nodes that were not detected at pathological analysis. B-cell follicles, efferent- and afferent lymph vessels and blood vessels were identified. Mean T1, T2, T2*, ADC values (± standard deviation) were 944∈±∈113 ms, 32∈±∈2 ms, 16∈± ∈2 ms, 0.39∈±∈0.09•10^-3 mm²/s, respectively. Conclusions: 7 Tesla MRI of ex vivo human axillary lymph nodes correlated well with pathology. MRI detected all nodes present in the specimens and allowed visualization of fine structural detail. Pathology-correlated quantitative MRI data are presented.