Benign and Malignant Diseases of the Endometrium

NORMAL ANATOMY T2-weighted magnetic resonance imaging sequences In premenopausal women, three distinct zones are visible within the uterine corpus on T2-weighted images: the outer myometrium, the inner myometrium or junctional zone, and the endometrial complex (Fig. 1A). The outer myometrium is of intermediate signal intensity on T2-weighted images. The inner myometrium or junctional zone forms a well-defined band of low signal intensity and normally measures from 2–8 mm in maximum thickness (1). The cause of this low signal on T2-weighted sequences likely is multifactorial, and a number of hypotheses have been put forth. For example, the inner fibers of the myometrium are arranged in a more compact, organized manner, parallel to the basal layer of the endometrium, in contrast to the outer fibers of the myometrium, which are arranged more randomly (2). In addition, studies have shown that the fibers of the inner myometrium have a higher nuclear-to-cytoplasm ratio and a lower water content compared with the fibers of the outer layer (3,4). The contrast between the outer myometrium and junctional zone typically becomes less marked in the postmenopausal uterus as the myometrial signal intensity progressively decreases.FIG. 1.: Normal uterine anatomy in a premenopausal woman. A: Sagittal T2W FSE image depicting zonal anatomy. Central high-signal-intensity stripe (E) represents the endometrium. Hypointense zone immediately subjacent represents the junctional zone (JZ) or inner myometrium (white arrowheads). Band of low signal intensity within the cervix (Cx) represents the fibrous stroma. The outer myometrium is of intermediate signal intensity. B: Transverse SGE postgadolinium image obtained during the early phase shows greater enhancement of the inner myometrium (white arrows). Note that the endometrium remains hypointense. C: Sagittal SGE postgadolinium image obtained during the delayed phase shows homogeneous enhancement of the myometrium. The endometrium (white arrowheads) shows enhancement and appears minimally hyperintense relative to the myometrium. This enhancement pattern is seen most commonly during the proliferative phase of the menstrual cycle.The endometrium and fluid within the endometrial cavity correspond to the central high-signal-intensity stripe on T2-weighted magnetic resonance (MR) images. The endometrial thickness varies widely, depending on both the phase of the menstrual cycle and the age of the patient. The endometrial complex is thinnest during menstruation, but it increases progressively during the proliferative phase and continues to increase during the secretory phase, as a result of both estrogen and progesterone stimulation (5,6). The thickness of the endometrial complex varies considerably, typically ranging from 3–6 mm in the proliferative phase and from 5–13 mm in the secretory phase. The endometrial complex in the postmenopausal patient (not receiving exogenous hormones) should not exceed 5 mm (3,7,8). Postmenopausal women taking tamoxifen prophylaxis typically show widening of the endometrial complex. Conversely, the endometrium becomes thin in women taking oral contraceptives (average 2 mm) and shows little temporal variation. T1-weighted magnetic resonance imaging sequences T1-weighted images are used to evaluate the uterine contour because of the high inherent contrast between fat and the uterine soft tissue. T1-weighted images are not suitable for evaluating the internal anatomy because the uterus is of uniformly low signal intensity on these images. However, during the mid-secretory phase of the menstrual cycle, the endometrium may be of slightly greater intensity than the myometrium (9,10). T1-weighted images also are needed to diagnose the presence of hematometra. Postcontrast magnetic resonance imaging sequences The enhancement pattern of the uterus, and particularly the endometrium, also depends on the hormonal status of the patient. During the proliferative phase, there is early enhancement of a thin subendometrial layer (Fig. 1B), followed by enhancement of the remaining myometrium (Fig. 1C). This pattern also is observed in postmenopausal women (Fig. 2) (11). The junctional zone demonstrates early enhancement during the menstrual period (11). On the other hand, the secretory phase is characterized by early enhancement of the outer myometrium. The endometrium shows little enhancement on dynamic imaging but demonstrates significant delayed enhancement, becoming isointense or hyperintense relative to the myometrium. In some patients, delayed postcontrast images may simulate T2-weighted MR images, with a high-signal-intensity endometrium, low-signal-intensity junctional zone, and an intermediate signal intensity outer myometrium. The contrast difference, however, is considerably less marked than on the T2-weighted images, and in most patients the junctional zone and outer myometrium become isointense on delayed contrast-enhanced images.FIG. 2.: Normal uterine anatomy in a postmenopausal woman. A: Sagittal T2W FSE image shows the endometrium to be thin and hyperintense (white arrowheads). B: Sagittal SGE postgadolinium image obtained during the early phase demonstrates the hypointense endometrium (black arrowheads) and a thin layer of subendometrial enhancement (black arrow) immediately subjacent.TECHNIQUE Patient preparation The objective of patient preparation is to obtain the best possible image quality while making the examination as comfortable as possible for the patient. To minimize motion artifacts induced by bowel peristaltism, patients are advised to fast from 6–8 hours before the procedure. In addition, patients are given glucagon 1 mg or hyoscine-N-butylbromide (Buscopan) 40 mg intramuscularly to further reduce bowel peristaltism (12). An empty urinary bladder minimizes ghosting artifact from patient motion. In addition, an empty urinary bladder maintains the uterus in a more caudal position in the pelvis, away from small bowel loops. When claustrophobia is a concern, prone scanning or intravenous sedation may be helpful. Surface coils Imaging of the endometrium should be performed using the smallest possible field of view (20–24 cm), thin sections of 4–5 mm, and the largest possible matrix size appropriate to each individual sequence. To achieve these high-resolution images, patients are ideally scanned using a dedicated phased-array pelvic multicoil, which greatly improves the signal-to-noise ratio (13,14). Although not used in routine clinical practice, endovaginal coils or endocavitary coils placed directly into the endometrial cavity can depict the anatomy of the endometrium in greater detail (15). Magnetic resonance imaging pulse sequences Pulse sequences used to image the endometrium include T2-weighted, precontrast fat-suppressed T1-weighted, and dynamic contrast-enhanced sequences. Following a single-shot fast spin-echo (SSFSE) T2-weighted localizer in the sagittal plane, fast spin-echo T2-weighted images are acquired in the transverse, sagittal, and coronal oblique (short-axis) planes. The short-axis coronal oblique is particularly valuable for staging endometrial carcinoma because it allows assessment of the depth of myometrial invasion in two orthogonal planes. Typical imaging parameters for the fast spin-echo T2-weighted MR images include TR/TE 4,000–7,500/102 milliseconds (repetition time/echo time), 20–24 cm field of view, four signals acquired, 512 × 256 matrix, echo train length of 16, bandwidth of 32, and a 4-mm section thickness with a 1-mm intersection gap. SSFSE sequences, as they are currently implemented, are not well suited for imaging the endometrium and particularly should not be used for staging endometrial carcinoma. The role of breath-hold fast spin-echo T2-weighted sequences in imaging endometrial pathology is still being evaluated. T1-weighted sequences in the transverse plane without fat suppression are used primarily to detect lymph node metastases in patients with documented uterine malignancies. Coverage should extend cranially to include the renal hila. T1-weighted spin-echo images are performed with the following parameters: TR/TE 600/9 milliseconds, 20–24 cm field of view, two signals acquired, 256 ×160 matrix, and 5-mm section thickness with a 2-mm gap. Respiratory ordered phase encoding to minimize breathing motion artifacts typically is applied. Alternatively, a breath-hold T1-weighted two-dimensional spoiled gradient echo (SGE) sequence may be obtained as follows: TR/TE 250/4.2 milliseconds, 20–24 cm field of view, one signal acquired, 256 × 160 matrix, and 5-mm section thickness with a 2-mm gap. Contrast-enhanced sequences are mandatory when evaluating endometrial pathology. They accurately distinguish between a hematometra and true endometrial pathology. In addition, they improve the detection and characterization of endometrial pathology, particularly endometrial polyps. Contrast-enhanced sequences also are helpful for endometrial carcinoma staging. Dynamic contrast-enhanced sequences using a gadolinium chelate typically are acquired in the sagittal or coronal oblique plane. Dynamic scanning is performed using a fat-suppressed two-dimensional SGE sequence, in three sequential acquisitions, after intravenous contrast administration. A preinjection run confirms the accuracy of the slice locations and facilitates quantitative and qualitative assessment of contrast the dynamic run is a delayed in a plane to the dynamic run is The dynamic run can be performed using the following imaging parameters: milliseconds, 20–24 cm field of view, one signal acquired, 256 × 160 matrix, and 5-mm section thickness without an intersection gap. fast sequences currently are being and may two-dimensional fast sequences for dynamic imaging of the and is a of estrogen or sequential in postmenopausal women in the uterus been the in the of in the endometrium endometrial may be seen in premenopausal women, in with and also may be with as and typically with uterine In postmenopausal women, endometrial can endometrial carcinoma both and on with of endometrial with an increase in the ratio of to can be into three without of with complex characterized by and with and with a high of The of in patients with from The of in patients without is low with endometrial typically are with because of the high of with or complex a of progesterone with endovaginal endometrial to a in the endometrial studies show that and may Magnetic resonance imaging Magnetic resonance imaging role in the routine of patients with endometrial should be used as a for patients with on in or endometrial is not In this can the thickness of the endometrium and the presence of on to a uterus or In some can of endometrial as and carcinoma from by an endometrial it is to in that the imaging of endometrial is not and with that of endometrial and endometrial polyps. On the thickness of the postmenopausal endometrium on T2-weighted images been to be However, to mm may be in patients on some hormonal with the of there is a relative of in the on the endometrial thickness for the the endometrium. On endometrial as less of the endometrial complex (Fig. The remains well The signal intensity is isointense or slightly hypointense relative to the endometrium on T2-weighted sequences. the endometrium, is hypointense relative to the myometrium during the early postcontrast images (Fig. and becomes isointense or hyperintense relative to the myometrium on delayed contrast-enhanced images (Fig. However, it may slightly hypointense to the myometrium on delayed images. In addition, small hypointense may be seen within the endometrial complex on delayed sequences. This imaging is and with that of other endometrial endometrial carcinoma and endometrial A: Sagittal T2W FSE The uterus is and shows the endometrium (E) to be and hypointense. Sagittal SGE postgadolinium images obtained during the early and show enhancement of the endometrial complex Note that the junctional zone is This imaging is and with early endometrial carcinoma is not and are the most of the uterine Although are they may result in postmenopausal or are in of They can be or with a thin may in or in the of endometrial or less commonly carcinoma are a more cause of endometrial than or carcinoma The of endometrial is higher in postmenopausal women with tamoxifen than in women in patients with an endometrial thickness of 5 mm or greater In the endometrial typically cm in a of three in of fibrous and endometrial with postmenopausal and endometrial endometrial and of the for the following of the of of carcinoma may be in and endometrial and carcinoma may in the patient Magnetic resonance imaging are of intermediate signal intensity on T1-weighted images On T2-weighted images, as that are slightly hypointense relative to the endometrium (Fig. However, may be isointense on T2-weighted sequences and as or endometrial are in signal intensity The presence of a central fibrous and the of a On T2-weighted sequences, the fibrous is seen as a hypointense within a are well-defined of size and are seen as high-signal-intensity on T2-weighted images The presence of is however, and these also may be in endometrial and endometrial carcinoma may a However, hypointense relative to the endometrium on T2-weighted sequence (Fig. in with myometrial are to from endometrial A: Sagittal T2W FSE is of the endometrial complex with an of (white the endometrium. B: Sagittal SGE postgadolinium image obtained during the early phase shows a of enhancement (white to the of low signal on the T2W images. Note that the endometrium not show enhancement on early contrast-enhanced images.FIG. uterine Sagittal T2W FSE is a hypointense the endometrium (white sequences improves the detection of endometrial show a of enhancement after gadolinium administration. early and are well the hypointense endometrial complex on early dynamic (Fig. In addition, a can be during the phase. 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The age of is The in of patients is postmenopausal or which been by endometrial or and to early most women with and the is include estrogen endometrial and a been shown to have a with endometrial carcinoma also have been of endometrial carcinoma in the of of endometrial are from well to include and Although the is a the and have a than the of endometrial be on the of imaging The by or endometrial carcinoma the myometrium and the invasion of the or bowel to lymph may without pelvic lymph node the the the higher and greater than myometrial invasion are with an of pelvic and lymph node as well as and are most commonly to The most of metastases is the also may on the of the the and staging is for and assessment of patient of the depth of myometrial or both patient In the depth of myometrial invasion with the of metastases and and is the one most of patient and For example, patients with to the corpus or with myometrial invasion have a of with myometrial invasion have a of metastases with and with and with which may from The in patients with myometrial invasion is compared with for patients with 1 endometrial patients with of and and endometrial carcinoma are with and there is myometrial invasion some for or lymph node metastases more with and and lymph node as well as The presence of invasion also the is with of the to the low uterine or the The of to or cervix is by the A that patients with invasion of the should be to with and the in this the of Imaging of is as a in the patient and is a of the endometrial stripe on than 5 mm) is for endometrial pathology and endometrial of the subendometrial or into the myometrium been an of myometrial an subendometrial However, of to the pelvic and into the is and myometrial invasion may be in the of a or In addition, in evaluating the to the and lymph On contrast-enhanced the of endometrial carcinoma is a within the endometrial which is and can be by endometrial or Although of it accurately evaluate the of invasion or the depth of myometrial which is a significant in early of contrast and a role in staging endometrial that is to and can be performed in patients to evaluate on because of anatomy or as particularly well in myometrial invasion and in to and In addition, it is to in the of Although the of as a routine staging a it more than the of staging. the the number of lymph node studies have a significant between staging and staging The in patients with clinical of and in patients with T2-weighted MR images are best for the zonal anatomy of the uterus and are used to and endometrial They also to the from the myometrium In to sagittal and transverse T2-weighted images, obtain short-axis of the uterine corpus because they in evaluating myometrial T1-weighted images in the transverse plane are used to detect enhancement improves the detection and characterization of endometrial between and and the depth of myometrial it improves the staging accuracy because endometrial typically less than the endometrium and myometrium The and accuracy for from central uterine is and for contrast-enhanced T1-weighted images, and and for T2-weighted images, of and zonal anatomy is with fast spin-echo images. The ratio in endometrial carcinoma is higher than that in endometrial or endometrium the to a status while the best for early endometrial carcinoma staging. They that T2-weighted imaging more in premenopausal patients and T1-weighted imaging more in postmenopausal because is performed after and it should be after a as a of signal The of the uterine zonal however, is not most commonly as or widening of the endometrial complex on an can be seen the endometrial In patients with myometrial the are or are isointense to the myometrium on T1-weighted images. On T2-weighted sequences, the signal intensity is ranging from isointense or slightly hypointense relative to the endometrium, to a signal intensity that is isointense to the myometrium. to have a homogeneous On dynamic contrast-enhanced images, endometrial less than the myometrium. The in enhancement becomes less marked on delayed carcinoma is to the carcinoma and the is (Fig. The uterus may or the endometrial stripe may than 5 mm in postmenopausal not accurately of carcinoma from (Fig. or an endometrial (Fig. is for in endometrial an may be seen on early contrast-enhanced of the junctional zone is the of (Fig. appears and and it from carcinoma. The accuracy of in making this varies from On dynamic images, a thin layer of subendometrial enhancement may be in some patients when been to be in (11). In and there is myometrial invasion as or of the junctional zone by a on T2-weighted images. less than (Fig. and greater than (Fig. of the thickness of the myometrium. of the junctional zone be in two planes. In the of a junctional zone, of the is of invasion (1). the depth of myometrial invasion greatly patient have been to detection of myometrial dynamic contrast-enhanced which can be when the junctional zone is on T2-weighted imaging The accuracy in myometrial invasion with T2-weighted, contrast-enhanced T1-weighted, and dynamic fast MR images are and The accuracy of in invasion from and from in the depth of myometrial invasion been to be higher with dynamic contrast-enhanced T1-weighted sequences than with T2-weighted or delayed contrast-enhanced sequences because of myometrial contrast Sagittal T2W FSE image shows (white of the endometrial complex. The junctional zone is The imaging are and with of endometrial A: Transverse T2W FSE image shows the to be hypointense relative to the endometrium. The junctional zone (white arrowheads) is by the and there is invasion of the inner of the myometrium. SGE postgadolinium images obtained during the early and delayed phase show that the to a than the myometrium. Note the of the inner myometrium with invasion (black A: Sagittal T2W FSE The is hypointense relative to the endometrium and slightly hyperintense relative to the outer myometrium. The junctional zone is by the and more than of the myometrium (black arrowheads). B: SGE postgadolinium image obtained during the early phase confirms outer myometrial invasion (black arrowheads) by the invasion of the seen on T2-weighted imaging as widening of the internal and (Fig. is by invasion of the fibrous (Fig. On T2-weighted images, the appears the hypointense fibrous stroma. enhancement may from and In addition, dynamic is helpful for the of as the to a greater than the and fibrous stroma. In dynamic can on T2-weighted imaging or oblique are the best for evaluating invasion may invasion when and and clinical are This because patient Sagittal T2W FSE image shows a hematometra with low-signal-intensity The the outer myometrium (black arrow) and to the (white arrowheads). The fibrous however, remains A: Sagittal T2W FSE image shows an into the Note the of the fibrous and (white arrowheads). B: Sagittal SGE postgadolinium image obtained during the early phase shows of the (black arrowheads) with into the fibrous endometrial carcinoma the uterus but remains to the pelvic of the hypointense signal of the outer on T2-weighted images (Fig. invasion may be to detect of the signal intensity of the fat the uterus on T1-weighted images. the by and are seen most commonly with from the uterine The also may be in a and as an intermediate signal intensity within the The presence of is and pelvic is The signal of lymph are not of and on size of the between the two not to be for in are on T1-weighted 1 cm or greater in the are Contrast-enhanced fat-suppressed echo T1-weighted or fat-suppressed echo T2-weighted images also are hyperintense in the of hypointense in the may in the of pelvic lymph node the the FSE shows of the the on the Note the uterine is of both to invasion of the with visible in the the or bladder is as the presence of of include and (1). or are of intermediate signal intensity on T1-weighted images and hyperintense on T2-weighted images of or less than 1 are not visible with of staging with include the of the myometrium by a or contrast between and myometrium on T2-weighted or T1-weighted contrast-enhanced and the presence of and some of the by the or may simulate may when invasion is endometrial carcinoma may as a pelvic the signal as the or as pelvic or it may as pelvic or metastases are possible but are with a high or are for of uterine malignancies. are endometrial typically as is than for staging is the most for The are characterized by show early and to been imaging of endometrial The used for staging uterine is the as that for endometrial carcinoma. sequences with and without fat suppression are performed to contrast to the presence of fat in (1). In a two observed in endometrial In the a pelvic which low to intermediate signal on T1-weighted imaging with of The and of intermediate signal intensity and of on T2-weighted images (Fig. correspond to the of myometrium on examination The pattern that of an endometrial with myometrial which is or This pattern may be from an endometrial carcinoma. to be and more than endometrial In addition, to show significant enhancement (Fig. in one of the On dynamic contrast-enhanced images, may show enhancement This of enhancement from A: Sagittal is a the endometrial B: SGE postgadolinium image obtained during the phase shows enhancement of the with invasion of the inner myometrium (white to have an with the is seen more in of endometrial than in of endometrial carcinoma. or is of of endometrial with of may uterine with or uterine should be in the of in the myometrium The for in this

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