Diffusion-weighted imaging in ectopic pregnancy: Ring of restriction sign

Objective: To demonstrate the diffusion-weighted imaging (DWI) findings of ectopic pregnancy (EP) and introduce the "ring of restriction" sign by discussing possible causes. Methods: Between January 2014 and January 2017, patients with EP and examined by MRI on a 3T scanner were retrospectively evaluated. MRI and DWI findings were recorded. Results: A total of 40 patients were diagnosed with EP at our university hospital, 8 of whom (20%) were evaluated by MRI and DWI. All of them were haemodynamically and clinically stable and could be imaged adequately. Locations were ovary (n = 3, 37.5%), tuba (n = 2, 25%), Caesarean section scar (n = 2, 25%) and parauterine (n = 1, 12.5%). In all eight EPs, the gestational sac diameter was compatible with 7-9 weeks. With DWI, the gestational sac was seen as a thick-walled cyst-like structure. The thick wall showed diffusion restrictions in all patients (ring of restriction sign). Conclusions: DWI through its cellular and molecular evidence may contribute diagnosis of EP.