Objective   To explore the signal characteristics of MR imaging after ultrasound ablation for uterine fibroids.    Methods   Totally 65 patients (41.2±6.5 years old

before menopause) with 80 uterine fibroids who were admitted in our hospital from January 2007 to February 2008 were subjected in this study. They received MR imaging 1 week before and 4 to 8 weeks after ultrasound ablation. T1-weighted/T2-weighted signals before and after the therapy were compared.    Results   The filling rate was 98.8% (79/80) before therapy

but 8.8% (7/80) after therapy on contrast-enhanced scanning. Before therapy on T1-weighted scanning: high-signal 1.2%

intermediate-signal 91.3%

low-signal 7.5%; after therapy 83.8%

16.2% and 0 in turn; high-signal fibroids 100% (67/67) showed necrosis; intermediate-signal fibroids 46.2% (6/13) showed necrosis（P0.05); signal of 66 fibroids increased to high-signal

and 100% (67/67) showed necrosis. Signal of 14 fibroids had no change

and 50% (7/14) showed necrosis (P0.05); relationship of volume between high-signal area on T1-weighted and necrosis area had linear correlation (r=0.93

P0.05). There was not obviously relationship between change of signal of T2-weighted and necrosis (P0.05).    Conclusion   High-signal of MR T1-weighted imaging indicates coagulation necrosis of the fibroids in early period after ultrasound ablation．