Diffusion-weighted imaging improves the diagnostic accuracy of conventional 3.0-T breast MR imaging.

PURPOSE: To evaluate the incremental value of diffusion-weighted (DW) imaging and apparent diffusion coefficient (ADC) mapping in relation to conventional breast magnetic resonance (MR) imaging in the characterization of benign versus malignant breast lesions at 3.0 T. MATERIALS AND METHODS: This retrospective HIPAA-compliant study was approved by the institutional review board, with the requirement for informed patient consent waived. Of 550 consecutive patients who underwent bilateral breast MR imaging over a 10-month period, 93 women with 101 lesions met the following study inclusion criteria: They had undergone three-dimensional (3D) high-spatial-resolution T1-weighted contrast material-enhanced MR imaging, dynamic contrast-enhanced MR imaging, and DW imaging examinations at 3.0 T and either had received a pathologic analysis-proven diagnosis (96 lesions) or had lesion stability confirmed at more than 2 years of follow-up (five lesions). DW images were acquired with b values of 0 and 600 sec/mm(2). Regions of interest were drawn on ADC maps of breast lesions and normal glandular tissue. Morphologic features (margin, enhancement pattern), dynamic contrast-enhanced MR results (semiquantitative kinetic curve data), absolute ADCs, and glandular tissue-normalized ADCs were included in multivariate models to predict a diagnosis of benign versus malignant lesion. RESULTS: Forty-one (44%) of the 93 patients were premenopausal, and 52 (56%) were postmenopausal. Thirty-three (32.7%) of the 101 lesions were benign, and 68 (67.3%) were malignant. Normalized ADCs were significantly different between the benign (mean ADC, 1.1 x 10(-3) mm(2)/sec +/- 0.4 [standard deviation]) and malignant (mean ADC, 0.55 x 10(-3) mm(2)/sec +/- 0.16) lesions (P < .001). Adding normalized ADCs to the 3D T1-weighted and dynamic contrast-enhanced MR data improved the diagnostic performance of MR imaging: The area under the receiver operating characteristic curve improved from 0.89 to 0.98, and the false-positive rate decreased from 36% (nine of 25 lesions) to 24% (six of 25 lesions). CONCLUSION: DW imaging with glandular tissue-normalized ADC assessment improves the characterization of breast lesions beyond the characterization achieved with conventional 3D T1-weighted and dynamic contrast-enhanced MR imaging at 3.0 T.

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 non-invasive, quantitative sodium ((23)Na) magnetic resonance imaging (MRI) in patients with benign and malignant breast tumors. METHODS: (23)Na and (1)H MRI of the breast was performed on 22 women with suspicious breast lesions (> or =1 cm) at 1.5 Tesla. A commercial proton ((1)H) phased array breast coil and custom solenoidal (23)Na coil were used to acquire (1)H and (23)Na images during the same MRI examination. Quantitative 3-dimensional (23)Na projection imaging was implemented with negligible signal loss from MRI relaxation, or from radio-frequency field inhomogeneity, in less than 15 min. Co-registered (1)H and (23)Na images permitted quantification of TSC in normal and suspicious tissues on the basis of (1)H 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 (23)Na 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.