Study of normal breast tissue by in vivo volume localized proton MR Spectroscopy: variation of Water-Fat ratio in relation to the heterogeneity of the breast and the menstrual cycle

Abstract

Purpose: To investigate the alterations in water-fat (W-F) ratio of the normal breast tissue of female volunteers as a function of the histological phases of the menstrual cycle. Methods: Image-guided volume localized in vivo proton (¹H) magnetic resonance spectroscopy (MRS) at 1.5 T was carried out in the para-areolar region and the upper and lower quadrants of the normal breast tissue of volunteers (n=29; mean age 33.7±6 years) during five histological phases of the menstrual cycle. Results: A W-F value of 0.90±0.41 was observed for the para-areolar region during the proliferative phase, which reduced to 0.46±0.21 and 0.45±0.25 during follicular and luteal phases, respectively. The value increased to 0.76±0.61 during secretory and to 0.87±0.37 during menstrual phases. No significant difference was observed in the W-F value for the upper and the lower quadrants of the breast during various phases of the menstrual cycle. However, the W-F ratio of the para-areolar region was significantly higher compared to the upper and the lower quadrants during all phases. This reflects the dependence of W-F value on the amount of glandular and adipose tissues and the heterogeneous nature of the breast. Conclusions: Our results indicate that changes in the normal breast tissue characteristics occur due to physiological factors like menstrual cycle that strongly influences the W-F value especially the para-areolar region in a cyclic manner. Thus any assessment of breast pathology using W-F values should be carried out carefully taking into consideration the location of the tumor within the breast as well as the time of menstruation.