MRI Characterisation of T2 Hypointense Ovarian Lesions

Abstract

The evaluation of sonographically indeterminate adnexal lesions should be performed with MRI (Magnetic Resonance Imaging). It is fundamental to determine the exact location of the lesion, since the differential diagnosis and therapeutic approach are distinct according to the organ of origin. Some signs that may indicate an ovarian origin are: the presence of ovarian follicles and normal ovarian parenchyma surrounding the lesion, without a cleavage plane (“embedded organ sign”); a change in the ovarian contour by the mass (“beak sign”); visualisation of a vascular pedicle or the gonadic veins leading to the lesion (“suspensory ligament sign”); deviation of the iliac vessels laterally and of the pelvic ureters posteriorly or postero-laterally.
The majority of ovarian lesions show cystic components with high signal-intensity on T2 weighted-imaging. Hypointense lesions on T2 are less frequent. The differential diagnosis for T2 hypointense ovarian lesions can be vast: haemorrhagic lesions (namely endometrioma); presence of smooth muscle (leiomyoma); presence of fibrous tissue (fibroma, thecoma and cystadenofibroma) and tumours with mixed cellularity (Brenner tumour, “struma ovarii” and Krukenberg tumour).
According to the ESUR recommendations published in 2017, diffusion-weighted imaging (DWI) should be applied for those lesions, using high b-values. The lesions that show low-signal intensity on DWI are classified as benign and do not require further investigation. On the other hand, for lesions that demonstrate intermediate or high signal on DWI, it is essential to administrate intravascular contrast, ideally with dynamic-contrast enhanced imaging (DCE).