Quantitative Magnetization Transfer Imaging of the Breast at 3.0 T: Reproducibility in Healthy Volunteers

Key Words: quantitative MR, breast cancer, pool size ratio, test-retest Abbreviations: Magnetic resonance imaging (MRI), Dynamic contrast-enhanced MRI (DCE-MRI), extracellular matrix (ECM), magnetization transfer MRI (MT-MRI), magnetization transfer (MT), MT ratio (MTR), quantitative MT (qMT), field of view (FOV), fibroglandular (FG), volume of interest (VOI), mean PSR (mPSR), mean T2 M (mT2 M ), mPSR from the first scanning session (mPSR1), mPSR from the second scanning session (mPSR2), confidence interval (CI), echo time (TE), repetition time (TR), pool size ratio (PSR), radiofrequency (RF) Quantitative magnetization transfer magnetic resonance imaging provides a means for indirectly detecting changes in the macromolecular content of tissue noninvasively. A potential application is the diagnosis and assessment of treatment response in breast cancer; however, before quantitative magnetization transfer imaging can be reliably used in such settings, the technique's reproducibility in healthy breast tissue must be established. Thus, this study aims to establish the reproducibility of the measurement of the macromolecular-tofree water proton pool size ratio (PSR) in healthy fibroglandular (FG) breast tissue. Thirteen women with no history of breast disease were scanned twice within a single scanning session, with repositioning between scans. Eleven women had appreciable FG tissue for test-retest measurements. Mean PSR values for the FG tissue ranged from 9.5% to 16.7%. The absolute value of the difference between 2 mean PSR measurements for each volunteer ranged from 0.1% to 2.1%. The 95% confidence interval for the mean difference was Ϯ0.75%, and the repeatability value was 2.39%. These results indicate that the expected measurement variability would be Ϯ0.75% for a cohort of a similar size and would be Ϯ2.39% for an individual, suggesting that future studies of change in PSR in patients with breast cancer are feasible