Among the etiology of acute pelvic pain, ovarian torsion  due golden time for treatment the early and  accurate diagnosis  is very important.
TVS  with color Doppler is first step of imaging with some specific character  of ovaries such as enlargement of size with peripheral location of follicles which have echogenic border  and free fluid of culde  sac and high end diastolic flow pattern
are suggestive of torsion of ovaries.
sometime the torsion is not complete and findings are not straight forward pelvic MRI is the best chose as complimentary  imaging for accurate  diagnosis of  torsion.
within last 2 years we have few cases which are approved with surgery and pathology of ovarian torsion we find some MRI and sonogram  specific finding of ovarian images which help up for accurate diagnosis.