(a) and (b) STC index maps of patient 2. (c) Subtracted map of patient 2. (d) and (e) STC index maps of patient 5. (f) Subtracted map of patient 5. (g) and (h) STC index maps of patient 8. (i) Subtracted map of patient 8. (j) and (k) STC index maps of patient 9. (l) Subtracted map of patient 9. The STC index maps in (a), (d), (g), and (j) are obtained using the contralateral breast as reference. The STC index maps in (b), (e), (h), and (k) are obtained using the background tissue of the ipsilateral breast as reference.