Nonovarian Adnexal Masses
Its relatively large feld of view also allows MRI to localize pelvic lesions and their origin more accurately. Identifcation of a pelvic mass separate from the uterus and ovary changes the differential diagnosis. Examples of such lesions that may be accurately diagnosed by MRI include peritoneal inclusion cysts (Figure 7), pedunculated fbroid cysts, para-ovarian cysts, paratubal cysts, or lymphadenopathy. Cystic midline lesions that are accurately characterized by MRI include Gartner´s duct cyst, Bartholin´s cyst, and urethral diverticula (Figure 8).
A peritoneal inclusion cyst. (A) An axial T2-weighted image and (B) a postcontrast axial T1-weighted 3-dimensional gradient-recalled echo fat-suppressed image show “geographical-shaped' fluid collections (arrowheads) in the left hemipelvis with no discernible wall and without internal enhancement.
Urethral diverticulum. (A) Sagittal T2-weighted (T2W) fast spin-echo and (B) axial T2W fast spin-echo images show a cystic lesion surrounding the urethra (arrows). The vagina is located posterior to this mass (arrowheads).
Uterine anatomy is well delineated by MRI. The 3 distinct zones (which are most clearly delineated on sagittal T2W images) are the outer myometrium (intermediate-to-high signal), the inner myometrium or junctional zone (low signal), and the endometrial complex (high fluid/near fluid signal). Endometrial thickness varies greatly, depending on the phase of the menstrual cycle and the age of the patient. It is generally<15 mm in premenopausal women and <8 mm in postmenopausal women, regardless of cycle or hormonal stimulation. The junctional zone appears as low signal intensity on T2W images and typically measures <12 mm. The intrinsic T2 contrast between the outer myometrium and the junctional zone becomes less marked in the postmenopausal uterus because of reduced fluid in the tissues.
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.