Uterine zonal anatomy in MRI

Uterine zonal anatomy in MRI is best depicted with T2-weighted imaging. Three distinct zones are seen :

• The central, high-signal-intensity zone represents the endometrium and its cavity. During the menstrual cycle, the width of this stripe ranges from 5 mm early in the cycle to 10 mm late in the cycle.
• The layer of low signal intensity that underlies the endometrium, called the junctional zone, corresponds to the inner layer of the myometrium. Its width does not vary during the menstrual cycle.
• The peripheral intermediate-signal-intensity zone represents the outer portion of the myometrium. The latter varies in width and signal intensity during the menstrual cycle, reaching a maximum width of 25 mm and its highest signal intensity during the midsecretory stage.45,46 In postmenopausal women, both endometrium and myometrium decrease in thickness, with a consequent decrease in uterine size. At this stage, the endometrium should not exceed 5 mm in width

 Uterine zonal anatomy with endometrium (arrowhead), which is hyperintense; junctional zone (short arrow) as hypointense band; and outer myometrium (long arrow) with intermediate signal