Elevated tissue sodium concentration in malignant breast lesions detected with non-invasive 23Na MRI

Background The hypothesis that physiological and biochemical changes associated with proliferating malignant tumors may cause an increase in total tissue sodium concentration ( TSC) was tested with noninvasive, quantitative sodium ( Na-23) magnetic resonance imaging (MRI) in patients with benign and malignant breast tumors. Methods Na-23 and H-1 MRI of the breast was performed on 22 women with suspicious breast lesions ( 1 cm) at 1.5 Tesla. A commercial proton ( H-1) phased array breast coil and custom solenoidal Na-23 coil were used to acquire H-1 and Na-23 images during the same MRI examination. Quantitative 3-dimensional Na-23 projection imaging was implemented with negligible signal loss from MRI relaxation, or from radio-frequency field inhomogeneity, in less than 15 min. Co-registered H-1 and Na-23 images permitted quantification of TSC in normal and suspicious tissues on the basis of H-1 MRI contrast enhancement and anatomy, with histology confirmed by biopsy. Results Sodium concentrations were consistently elevated in ( N = 19) histologically proven malignant breast lesions by an average of 63% compared to glandular tissue. The increase in sodium concentration in malignant tissue was highly significant compared to unaffected glandular tissue ( P < 0.0001, paired t- test), adipose tissue, and TSC in three patients with benign lesions. Conclusion Elevated TSC in breast lesions measured by non- invasive Na-23 MRI appears to be a cellular-level indicator associated with malignancy. This method may have potential to improve the specificity of breast MRI with only a modest increase in scan time per patient.