Magnetization Transfer Ratio as a Predictor of Malignancy in Breast Lesions: Preliminary Results Ruth Helena Morais Bonini, 1 Denise Zeotti, 1 Luciano Albuquerque Lima Saraiva, 1 Clovis Simao Trad, 1 Joaquim Moraes Sarmento Filho, 2 Helio Humberto Angotti Carrara, 2 Jurandyr Moreira de Andrade, 2 Antonio Carlos Santos, 1 and Valdair Francisco Muglia 1 * MRI is an important tool for investigating breast cancer. Al- though recognized as the method of choice for screening high- risk patients, and for other indications the role of MRI for lesion characterization remains controversial. Recently some authors have advocated the use of morphologic and postcontrast fea- tures for this purpose. Quantitative breast MRI techniques have not been applied extensively in breast diseases. Magnetization transfer (MT) is a quantitative MR technique commonly used to investigate neurological diseases. In breast diseases the use of MT has been limited to improving visualization of areas of enhancement in postcontrast images. The purpose of this study was to evaluate the feasibility and utility of MT in discriminating benign from malignant breast lesions. Fifty-two lesions, BI- RADS 4 and 5, from 49 patients, were prospectively evaluated using the MT ratio (MTR). Patients were divided into two groups: benign and malignant lesions. The MTR of fat, pecto- ralis major muscle, fibroglandular tissue, and breast lesions were calculated. A statistically significant difference was found between MTR from benign and malignant lesions (P < 0.001). Preliminary results suggest that MT can be used to evaluate breast lesions. Further studies are necessary to better define the utility and applicability of this technique. Magn Reson Med 59:1030 –1034, 2008. © 2008 Wiley-Liss, Inc. Key words: breast cancer; MRI; magnetization transfer MRI has emerged as an important tool for investigating breast cancer (1). The high sensitivity of 3D dynamic con- trast-enhanced MR images has brought this technique to a peculiar position in breast cancer (2). Although it has been recognized as the method of choice for screening high-risk patients (3), evaluating breast implants (4), searching for occult cancer (5), and evaluating neoadjuvant therapy (6), the role of MRI for lesion characterization remains contro- versial (7,8). Indeed, a few years earlier lesion character- ization was not included among indications for breast MRI (9). More recently, some authors have advocated the use of MRI for this purpose, using its morphologic and postcon- trast features (10). However, the results were very discrep- ant, and breast MRI specificity lies between 20% and 100% for diagnostic purposes, and in screening programs this parameter could be even lower (11). To discriminate between benign and malignant lesions using MRI, most of authors rely on morphologic criteria (12), the pattern of enhancement on dynamic postcontrast images (13,14) or a combination of both (15). Recently, a multicenter trial confirmed the superior diagnostic accu- racy of combined morphological and dynamic features (2). To date, quantitative breast MRI techniques have not been applied extensively in breast diseases, although the dynamic contrast technique could be considered a quan- titative one. Except for a few reports using MR spectros- copy (16), breast diseases are not a common application for quantitative MR imaging techniques. Magnetization trans- fer (MT) is a quantitative MR technique commonly used to investigate neurological diseases (17). In this field, a large spectrum of diseases is now being evaluated largely using the magnetization transfer ratio (MTR). Several reports describe the utility of MTR, especially in white matter diseases (18,19). However, in breast diseases, except from one “in vitro” study (20), the use of MT has been limited to improving visualization of areas of enhancement in post- contrast images (21). MT is sensitive to tissue macromol- ecules (and therefore reflects the chemical composition of tissues). MT imaging is based on interactions between protons in bulk water and those attached to macromole- cules. By using RF saturation pulses, one of the T 1 path- ways, which is the association of free water with macro- molecules, is removed, leading to an increase in spin T 1 relaxation times. The purpose of our study was to evaluate the feasibility and utility of MT in discriminating benign from malignant breast lesions. MATERIALS AND METHODS This study was conducted in the Imaging Center of Hos- pital Clinicas of Ribeirao Preto Medical School, University of Sao Paulo, Brazil, in association with the Breast Oncol- ogy Group of the same institution. The study protocol was approved by the institutional ethics committee on Novem- ber 2003. From January 2004 to April 2006, patients with breast abnormalities (asymmetric densities or masses) de- tected by mammography, classified in category 4 and 5 on BIRADS (Breast Imaging Reporting and Data System), were selected for entry into this study. Inclusion criteria were patients: 1) whose lesions were selected for tissue sam- pling; 2) whose lesions had not been previously manipu- lated or treated in any form; 3) who agreed to be included in this study and signed an informed consent. The exclu- 1 Imaging and Medical Physics Center, Ribeirao Preto School of Medicine, University of Sao Paulo, Brazil. 2 Department of Gynecology and Obstetrics, Mastology Division, Ribeirao Preto School of Medicine, University of Sao Paulo, Brazil. *Correspondence to: Valdair F. Muglia, Imaging Center, Hospital Clinicas, Ribeirao Preto School of Medicine, University of Sao Paulo, Av. Bandeirantes 3900, Campus Monte Alegre, Ribeirao Preto, Sao Paulo, 14048 –900 Brazil. E-mail: muglia@convex.com.br Received 15 June 2007; revised 14 November 2007; accepted 18 December 2007. DOI 10.1002/mrm.21555 Published online in Wiley InterScience (www.interscience.wiley.com). Magnetic Resonance in Medicine 59:1030 –1034 (2008) © 2008 Wiley-Liss, Inc. 1030