The role of STIR MRI sequence in the evaluation of the breast following conservative surgery and radiotherapy.

The purpose of the study was to define the value of fat suppressed STIR sequence in the MRI of the conserved breast. To our knowledge, this study is the first clinical evaluation of STIR sequence in post-therapy conditions. Forty patients with early (T1-2, N0-1) invasive breast cancer underwent conservative surgery and postoperative radiotherapy. Routine follow-up examinations, including physical examination and mammography were supplemented with breast MRI in all cases 6-166 months (mean 27.6) after initial treatments. Three patients had bilateral cancer. Including follow-up (9 patients) MRI examinations, altogether 53 MRIs were available for analysis. An 0.5 T MRI (Elscint, Haifa, Israel) was used with double breast coil. Axial T1 and T2 weighted spin echo, STIR and 3D gradient echo dynamic sequences were performed. Pre- and postcontrast slices underwent serial subtraction. Twenty-eight circumscribed lesions were identified. All were well visualised on STIR sequence, regardless of histologic nature of lesions. One low grade DCIS was not detected by any sequence. Differential diagnosis between benign and malignant lesions was not possible by STIR sequence alone. STIR sequence was found to be more sensitive in the detection of treatment related breast edema and fluid collection, than T2 SE (spin-echo) sequence. Even the patients who were not good candidates for subtracted contrast enhanced dynamic studies - because of motion artefacts - could have been examined with satisfactory results. STIR is a very sensitive sequence for depicting circumscribed lesions and post-therapy complications, but not suitable for differentiation. It is a useful tool in the follow-up of patients with conserved breast subjected to radiotherapy.