Imaging the Female Pelvis: When Should MRI be Considered?

Ovarian Malignancies

Ovarian carcinoma remains the leading cause of gynecological cancer-related deaths in the United States, and it is estimated to comprise 6% of all cancer-related deaths in 2006.^[14] Approximately 75% of women have advanced disease at the time of diagnosis with a 5-year survival of only 29% in those with metastases.^[12,13,14]

No effective screening method currently exists for the detection of ovarian cancer, in part because the preclinical phase is estimated to be <2 years. Current methods include transvaginal ultrasound and determining serum CA-125 levels. Unfortunately, CA-125 is not specifc for ovarian cancers. Although MRI is clearly not cost-effective as a screening tool, it has become quite valuable for patients in whom sonographic results are indeterminate. As previously discussed, MRI can accurately characterize benign masses such as teratomas and endometriomas; this has proven to be a cost-effective approach, since unnecessary surgery can be avoided.^[10,11,12] MRI is also superior to CT in the diagnosis of peritoneal implants and has superior accuracy in diagnosing ovarian malignancy compared with CT and Doppler sonography. Gadolinium-enhanced MRI has a rate of depiction of benign lesions of 93% and of malignant lesions of 95%.^[10,11,12]

Primary ovarian neoplasms are classifed as epithelial tumors (60% to 70%), germ cell tumors (15% to 20%), and sexcord stromal tumors (5% to 10%). However, no imaging modality can differentiate between neoplastic subtypes. A study by Hricak et al^[3] found that the 2 most signifcant predictors of malignancy were the presence of vegetations in a cystic lesion and the presence of necrosis in a solid lesion.^[14] Other predictors of malignancy include wall or septal thickness >3 mm, presence of ascites, and a maximum diameter greater than 4 to 6 cm (Figure 6).^{[14,15,16,17]} On T2W images, an ovarian mass of high signal intensity that is found in conjunction with implants in the abdomen and pelvis is suggestive of mucinous cystadenocarcinoma with peritoneal metastatic disease. Because of the inherent wide feld of view of MRI relative to pelvic ultrasound, a single MRI examination can not only characterize an ovarian mass but can also be used in staging when a mass is noted to have malignant features. The presence of ascites, peritoneal, or serosal metastases as well as hydronephrosis may be detected.

(Enlarge Image)

Ovarian cystadenocarcinoma. (A) Sagittal T2-weighted fast spin-echo fat-suppressed, (B) postcontrast axial T1-weighted (T1W) fat-suppressed 3-dimensional (3D) gradient-recalled echo (GRE), and (C) sagittal T1W fat-suppressed 3D GRE contrast-enhanced images show a large midline pelvic cystic mass with papillary excrescence (arrowheads), which is consistent with ovarian cystadenocarcinoma.

Appl Radiol. 2008;37(1):9-24. © 2008  Anderson Publishing, Ltd.

Cite this: Imaging the Female Pelvis: When Should MRI be Considered? - Medscape - Jan 01, 2008.