Concurrent water T₂ and fat fraction mapping of the breast using the radial gradient and spin echo (RADGRASE) pulse sequence

This work describes and evaluates an efficient radial gradient- and spin-echo (RADGRASE) pulse sequence and reconstruction algorithm for concurrent measurement of proton-density weighted fat fraction (FF) and water component T₂ (T_2w) within breast tissues. The ability to estimate T_2w in breast tissues, where fat can be highly abundant, is demonstrated using oil/gel phantoms across a wide range of FF values (0.1–0.7). Successful T_2w mapping of breast tissues is also demonstrated in vivo by comparison with fat suppressed T₂ values. The sensitivity of RADGRASE to detect changes in the breast was assessed by tracking T_2w in 3 healthy volunteers through their menstrual cycle, demonstrating T_2w values in the late luteal phase to be 18–29 ms higher than in the follicular phase. The technique is also applied to a cohort of 68 patients taking tamoxifen for breast cancer risk reduction, where significant positive correlation between the FF parameter Frac50 and T_2w (p = 0.035) was observed in premenopausal subjects (n = 20). Our findings demonstrate the ability and efficacy of RADGRASE for simultaneously mapping FF and T_2w within breast tissues, and the potential utility of the technique in studying breast tissue changes in clinical applications.