MRI Screening of the Breast in Less than 2 Minutes: A Prelude to Extend MR Breast Screening Possibilities

PURPOSE To evaluate time to enhancement (TTE) as a parameter to differentiate benign from malignant lesions in MR Mammography using an ultrafast DCE protocol. METHOD AND MATERIALS 42 patients with 43 lesions (20 malignant, 23 benign, size range 3mm - 7 cm) were scanned at 3.0T (Siemens, Magneton Trio and Skyra) using a 16 channel bilateral breast coil. An interleaved protocol was used, in which a TWIST (Time-resolved angiography With Stochastic Trajectories) sequence was performed during and immediately after IV administration of 30 ml Gd-DOTA (20 time points, spatial resolution 10.92.5 mm, temporal resolution 4.32 seconds), preceded 1x and followed 5x by high resolution VIBE acquisitions (spatial resolution: 0.90.91 mm) lasting 107 seconds each. Consequently, the TWIST acquisitions could be used to assess TTE, whereas relative-enhancement versus time curves could be derived from the VIBE acquisitions. All evaluations were performed on a DynaCad workstation (InVivo), using primarily the maximum intensity projections (MIPs) of the subtracted series. TTE was defined as AC/a,!A"the timepoint were the lesion started to enhanceA-A?A 1/2 ? AC/a,!aEURoe AC/a,!A"the timepoint were the aorta started to enhanceA-A?A 1/2 ?. Lesions with TTE $AC/aEURdegA$?$ 12 seconds were considered malignant, Lesions with TTE $>$ 12 were considered benign. Similarly, based upon the curves we considered lesions with wash-out malignant and lesions with continuous enhancement benign. RESULTS Due to its speed the TWIST sequence showed less movement artifacts than the VIBE and -later- enhancing glandular tissue did not interfere with -earlier- enhancing lesions, making detection of the lesions on the MIPs easier. 19/23 malignancies had TTE $AC/aEURdegA$?$ 12 seconds, 17/20 benign lesions showed TTE $>$ 12 seconds. Using the curves, 19/ 23 malignancies showed wash-out and 13/20 benign lesions had continuous enhancement. Corresponding accuracy, sensitivity, specificity, PPV and NPV for TTE were 84, 83, 85, 86 and 81, compared to 74, 83, 65, 74 and 75 for curve analysis. CONCLUSION TTE is a strong discriminator between benign and malignant breast disease and appears to improve especially the specificity of the exam when compared to curve analysis. CLINICAL RELEVANCE/APPLICATION Ultrafast MRI, allowing evaluation of both inflow of contrast and morphology can be used to substantially shorten current MRI protocols. This may allow MRI screening at substantially lower costs.