T2-weighting can be achieved in spin-echo imaging by setting TE to be similar to the T2 values of tissues of interest (50-90 ms for breast tissues), while minimizing T1-effects by making TR long relative to the T1 values of breast tissues (TR > 3 seconds). Spin-density weighting can be achieved by minimizing both T1 and T2 weighting. T1 weighting is minimized by making TR long (> 3 seconds) and by making TE short (< 20 ms).