子宮內膜厚度之測量

子宮內膜厚度之測量,
外層密度較高more echogenic
內層密度較低more hypoechoic, homogenously echogenic
中央為前後子宮內膜interface

http://radiographics.rsna.org/content/32/6/1575.full

Normal endometrium in the middle to late phases of the menstrual cycle. (a) Midsagittal endovaginal US image obtained near midcycle shows a normal striated pattern. The endometrial thickness is correctly obtained from the anterior endometrial-myometrial interface to the posterior endometrial-myometrial interface (calipers). At midcycle, this measurement includes the more echogenic outer layer and more hypoechoic inner layer. The thin central hyperechoic line (arrow) is not a layer of endometrium but represents the interface between the anterior and posterior endometrial aspects; it should be continuous when imaged parallel to the long axis of the uterus. (b) Sagittal endovaginal US image obtained in a different woman in the secretory phase of the menstrual cycle shows homogeneously echogenic endometrium, which makes visualization of the central interface more difficult. For this reason, assessment of the endometrium for focal abnormalities is best performed in the early phase of the menstrual cycle.

Figure 9a

Figure 9b

 Endometrial thickness is best assessed with endovaginal US and represents the sum of the thicknesses of the two endometrial layers. The measurement is obtained on midline longitudinal images by placing cursors at the anterior and posterior endometrial-myometrial interfaces where the endometrium is widest, usually near the fundus. The central thin hyperechoic line represents the interface between the opposing anterior and posterior endometrial layers and should be continuous. Disruption of the central hyperechoic line, or heterogeneity of the endometrium, may indicate an underlying intracavitary lesion such as a polyp, myoma, or adhesion.

The hypoechoic layer peripheral to the endometrium, which is not always visible at US, represents the compact inner layer of myometrium and should not be included in endometrial thickness measurements (26) (Fig 8). A small amount of hypoechoic fluid or mucus within the endometrial cavity or cervical canal is a normal finding, but sizable fluid collections or retained echogenic blood clots may indicate obstructed menstrual flow, as seen with adhesions, cervical stenosis, or excessive bleeding. When fluid is noted in the endometrial cavity, it is excluded from the measurement of the endometrial thickness. In women taking oral contraceptives or using other hormonal contraceptives, such as progesterone-releasing intrauterine devices, the endometrium is generally thin throughout the menstrual cycle.