Ultrasmall superparamagnetic iron oxides enhanced MR imaging in rats with experimentally induced endometriosis

PURPOSE: The purpose of our study was to evaluate the feasibility of magnetic resonance imaging (MRI) using ultrasmall superparamagnetic iron oxides (USPIO) in the detection of experimentally induced endometriosis. MATERIALS AND METHODS: Endometriosis was surgically induced in rats by transplanting an autologous fragment of uterine tissue onto the inner surface of the abdominal wall, the posterior surface of the uterine body and the arterial cascades of the small intestines adjacent to mesenteric blood vessels. Six weeks later, MRI using Gd-DTPA and USPIO was performed for the evaluation of the ectopic uterine tissue (EUT). A scoring system was developed for image interpretation (0=absence, 1=probably absence, 2=probably presence and 3=presence). We defined MR index (MRIx) as the sum of T1-weighted and enhanced T1-weighted and T2-weighted image scores, and USPIO MRIx (MRIx(+USPIO)) as the MRIx score plus the score of USPIO-enhanced T2-weighted image. RESULTS: The MRIx(+USPIO) was also higher in the successfully autotransplanted group than in the failed group (6.19±1.72 versus 3.94±1.20, P<.001). There was also a significant linear relationship between MRIx(+USPIO) and pathologic status (R(2)=0.494, P<.001). Thirty-one (64.6%) of the 48 implanted uterine tissues were histologically confirmed on pathologic review. The area of MRIx and MRIx(+USPIO) in the detection of EUT more than 3 mm in size was 0.739 and 0.913, respectively. CONCLUSION: Our results suggest that USPIO-enhanced MRI could be a novel diagnostic tool for diagnosis in experimentally induced peritoneal endometriosis.