Dr. Agrawal is a Nuclear Medicine Fellow, Division of Nuclear Medicine, Mallinckrodt Institute of Radiology, St. Louis, MO; Dr. Sethi is a Research Associate, Department of Radiology, and Dr. Oto is a Professor, Department of Radiology, Biological Sciences Division, University of Chicago, Chicago, IL.
The multiplanar capabilities and excellent soft-tissue contrast on
magnetic resonance imaging (MRI) of the pelvis provide superb depiction
of the female pelvic anatomy and often lead to specific diagnosis
without ionizing radiation. MRI is often used as a problem-solving tool
in patients where ultrasound is inconclusive or suboptimal. It is a
modality of choice particularly for preoperative characterization and
staging of endometrial and cervical cancer and, hence, it plays an
important role in stratifying patients into appropriate treatment
options. MR imaging is uniquely well suited to the evaluation of
gynecologic conditions that occur during pregnancy and in the postpartum
period. The development of new, faster imaging sequences with parallel
imaging has enabled acquisition of images of a moving fetus and dynamic
evaluation of the entire female pelvic floor.
The goal of this
article is to familiarize the reader with techniques and applications of
MR imaging in the female pelvis, including recent advances, and discuss
imaging features of various abnormal conditions affecting the female
patient should fast for at least 4 hours and empty the bladder and
bowel just before examination to reduce blurring from motion artifacts
and ghosting due to bowel peristalsis and bladder motion. Other measures
may include antispasmodics, such as glucagon (0.5-1.0 mgIV/IM) or
hyoscine butylbromide 20-40 mg IM/IV. Intravenous administration of
these antiperistaltic agents has been shown to improve image quality and
lesion visualization in oncological pelvic MRI and is recommended for
MRI imaging protocol
phase-array surface coil is used to increase signal-to-noise ratio
(SNR). A basic imaging protocol must include a high-resolution,
free-breathing T2W sequences in the axial, oblique sagittal, and coronal
planes and an axial T1-weighted imaging (T1WI) sequence with and
without fat suppression. Recently developed high-resolution
3-dimensional, T2-weighted images appear promising and may decrease
total scan time. For benign disease, fast breath-hold sequences are
often enough despite slightly decreased resolution. However, evaluating
pelvic malignancies requires long duration, high-resolution, T2-weighted
FSE sequences. Optional sequences include contrast-enhanced fat
suppressed, T1WI. This can be obtained in dynamic fashion using
3-dimensional GRE-T1WI sequences. The fat-saturated T1WI sequence is
specifically necessary to characterize fat or hemorrhage within the
adnexa when there is a clinical suspicion of dermoid or
endometriosis.Other optional sequences depending on indication include
diffusion imaging, dynamic contrast-enhanced MRI,2 and peristalsis and pelvic-floor imaging.
imaging improves not only the detection and potentially the
characterization of small uterine tumors and complex ovarian cancer, but
also the visualization of small implants of peritoneal carcinomatosis,
which could significantly impact patient management. ADC measurement may
be useful for monitoring the therapeutic outcome after uterine arterial
embolization (UAE), chemotherapy and/or radiation therapy.3-8
has the potential to improve tumor detection and local staging, and can
also provide quantitative information about tumor perfusion, which may
be useful for both monitoring therapeutic effects and predicting
Protocols should be optimized
and tailored to address a specific indication for pelvic imaging.
Optimal protocol for a specific condition will be discussed further in
the text when each condition is addressed in detail.
Normal uterine anatomy on MRI imaging
uterus can be divided into the uterine corpus and cervix. On T1WI the
entire uterus is isointense to muscle and different anatomic zones
cannot be identified. The premenopausal uterine corpus on T2-weighted
images (T2WI) show 3 distinct zones (Figure 1):
- The central
high-signal intensity endometrium and secretions measure 3 to 6 mm in
the proliferative phase and 5 to 13 mm in the secretory phase.
middle low-signal intensity junctional zone measures 2 to 8 mm and is
the innermost layer of myometrium (less water, more smooth muscle and
greater percentage of nuclear area). The appearance of the junctional
zone changes with sustained myometrial contractions or uterine
peristalsis are important to distinguish from leiomyomas or adenomyosis.
- The outer intermediate-signal intensity of the myometrium.
postmenopausal uterus has an indistinct zonal anatomy, and the
junctional zone is not consistently visualized. It should be kept in
mind that Tamoxifen intake may induce endometrial hyperplasia, polyps,
Cervix on T2WI shows the following distinct zones (Figure 1):
- Central hyperintense mucous
intensity endocervical mucosa and glands (contains numerous folds and
clefts as the plicae palmate). Combined thickness of zones 1 and 2 is 2
to 3 mm
- Hypointense fibrous stroma is 3 to 8-mm thick
- Outer intermediate signal intensity loose stroma
Congenital uterine anomalies
occur in almost 1% of women within the reproductive age group. Although
hysterosalpingography and ultrasound may suggest aMüllerian duct
anomaly, further evaluation with MRI is often required, especially for
complex cases. MRI is the best imaging method available because of its
superior ability to reliably visualize and characterize complex
uterovaginal anatomy. For evaluation of uterine anomalies, coronal
oblique fast spin echo T2-weighted images parallel to the long axis of
the uterine corpus are very useful.10-11
Uterine agenesis or hypoplasia may or may not be a small uterine remnant without identifiable zonal anatomy.
Unicornuate uterus has
a reduced uterine volume, but normal endometrial—myometrial width ratio
with a banana-shaped configuration of uterus (Figure 2). A rudimentary
horn with or without endometrium may be present and may or may not show
communication with the uterine cavity. Urologic anomalies like
ipsilateral renal agenesis and ipsilateral pelvic kidney are often
associated with unicornuate uterus.
Bicornuate uterus results
from incomplete fusion of the uterine horns. On MR imaging, a fundal
indentation deeper than 1 cm and a muscular and fibrous septum
separating the divergent uterine horns greatly favors a bicornuate over
septate uterus. When the septum extends all the way down to the cervix,
causing its duplication, it is called bicollis, while it is a unicollis
when septum does not reach the external os.
Uterus didelphys results
from the arrest of midline fusion of Mullerian ducts and is
characterized by complete/partial duplication of the uterus, cervix, and
vagina. Patients are usually asymptomatic until menarche, unless
obstruction is present. This may lead to hematocolpos, hematometra, and
hematosalpinx. MR imaging demonstrates 2 widely separated horns and 2
cervices. The zonal anatomy is preserved in each hemiuterus (Figure 3).
Septate uterus results
from the failure of resorption of the fibrous septum between the
Mullerian ducts. MRI shows a fibrous septum, arising in the midline
fundus, and variable in length. It is considered complete when it
extends to the external cervical os. In approximately 25%of cases, the
septum can extend to the upper vagina. The external uterine contour may
be convex, flat, or mildly (<1.0 cm) concave and the indentation of
the myometrium or septum into the endometrial canal is more than 1 cm.
Arcuate uterus is
often considered a normal variant and not a congenital uterine anomaly.
On MRI, the normal external uterine contour is maintained. There is
smooth, broad and minimal indentation of myometrium or fibrous component
into the endometrial canal (<1 cm).12, 13
Benign uterine conditions
Endometrial hyperplasia usually
occurs in perimenopausal women, women taking estrogen without
progesterone, women takingTamoxifen for breast cancer, or those with
estrogen secreting tumors like granulosa cell tumors. Endometrial biopsy
is diagnostic and is needed to exclude malignant transformation, which
can be seen in 1% to 22% cases.14 MR imaging is helpful when
transvaginal sonography is indeterminate and biopsy is limited by
difficult anatomy or cervical stenosis. T2-weighted images demonstrate
diffuse thickening of endometrial stripe, which appears iso- to slightly
hypointense, compared with normal endometrium.
Endometrial polyps are
typically seen in postmenopausal women. These may be asymptomatic or
associated with irregular/persistent bleeding. On T2-weighted images,
they can be readily distinguished from submucosal leiomyomas by their
appearance. They are isointense or slightly hypointense to normal
endometrium. The presence of a stalk or cystic area favors polyp over
carcinoma or hyperplasia. Polyps show pronounced early enhancement that
persist on delayed imaging compared to carcinoma, which shows only mild
Leiomyomas are the most common benign uterine
tumors and are usually asymptomatic, but symptoms may range from
abnormal bleeding to mass effect, infertility, second trimester
abortions, torsion, infection, acute degeneration, or sarcomatous
degeneration. They can be classified by their location into submucosal,
intramural, subserosal, or cervical. Ultrasound is often used for the
diagnosis. MR imaging provides amore accurate determination of location,
number, size, and degree of degeneration (Figure 4). These features are
important for selecting patients before minimally-invasive treatments.
MR imaging also evaluates arterial supply before UAE to assess for
parasitized ovarian arteries that may lead to a poor response. MRI can
also be helpful in identification of fibroids with a stalk, malignancy,
and adenomyosis. On MRI, leiomyomastypically are well circumscribed,
isointense to muscle on T1-weighted images, and homogeneously
hypointense on T2-weighted images. A thin hyperintense rim of dilated
lymphatic clefts, dilated veins, and edema may be seen on T2-weighted
images and helps differentiate leiomyomas from focal adenomyosis. This
rim may enhance with gadolinium administration.
degeneration may show heterogeneous high-signal intensity on T2-weighted
images with lack of contrast-enhancement. Hemorrhagic (red)
degeneration of pregnancy or after uterine artery embolization
demonstrates high-signal areas on T1-weighted images. MR imaging is also
very accurate in differentiating a subserosal leiomyoma from an ovarian
tumor. A mass that is homogenously low-signal intensity on T2 is likely
to be a leiomyoma and the only ovarian tumors that could mimic this
appearance are ovarian fibroma and Brenner’s tumor; also benign lesions.15
The dynamic-contrast MR enhancement rate is higher for uterine
leiomyomas than for ovarian fibromas in terms of both maximal
enhancement (P < 0.001) and enhancement rate at 30 (P = 0.009), 60 (P
= 0.007), and 90 seconds (P =0.0009).16
endometrial stroma and glands within the myometrium in women of
reproductive age and may be microscopic, focal (adenomyoma), or diffuse.
Adenomyosis is usually asymptomatic, but may cause pain and
dysfunctional uterine bleeding. MR imaging is a highly accurate
noninvasive technique for the diagnosis with a high sensitivity (78% to
88%) and specificity (67% to 93%).17,18 On T2-weighted
images, there is a thickening of the junctional zone to 12 mm or more.
There may be either diffuse or focal thickening of the junctional zone
forming an ill-defined area of low-signal intensity, occasionally with
embedded bright foci on T2-weighted images (Figure 5). The presence of
tiny hyperintense foci representing small deposits of ectopic
endometrium, cystically dilated endometrial glands, or hemorrhagic fluid
on T2-weighted images is pathognomonic of adenomyosis. If extensive
hemorrhage is present, the imaging reveals larger, well-circumscribed,
myometrial cysts containing blood products of different ages.
Contrast-enhanced sequences may show uniform enhancement or a speckled
appearance, with numerous nonenhancing foci corresponding to the
punctate hyperintensities seen on T2-weighted images.
both of these conditions is important, as it changes the treatment.
Focal adenomyoma has characteristic features including a poorly defined
border, minimal mass effect on the endometrium compared to a leiomyoma
of same size, an elliptical rather than round configuration, may display
linear striations radiating out from endometrium, and shows no dilated
vessels at the margin of the lesion.19
Benign disease of the cervix
Nabothian cysts are
the most common benign cervical lesions and are usually asymptomatic
despite growth as large as 4 cm. These are caused by distension of
endocervical glands or cleft with mucus. MR imaging demonstrate well
defined margins and very high signal intensity lesions on T2-weighted
images. Solid components within the cyst should raise suspicion for
Cervical leiomyomas are easily distinguished by their well-defined margin and low signal intensity on T2-weighted images.
Endocervical polyps appear on MRI as a cystic or solid polypoidal mass within the lumen that protrudes into the endometrial cavity.
Malignant uterine disease
Endometrial carcinoma is
the most common malignancy of the female genital tract that primarily
occurs in postmenopausal women (sarcomas account for 2% to 5% of uterine
malignancy). Ninety percent are adenocarcinoma; others types include
adenocarcinoma with squamous differentiation, clear cell or papillary
serous carcinoma. It is primarily staged surgically. MR imaging may
greatly optimize the surgical procedure and therapeutic strategy. The
role of MRI in endometrial cancer includes the evaluation of depth of
myometrial invasion,cervical invasion, and nodal metastasis.
spectrum of MRI findings include thickening of endometrium, foci of
either low or high-signal intensity on T2-weighted images with less
enhancement than the surrounding myometrium (Figure 6). Myometrial
invasion is assessed based on thickness of the remaining myometrium
(Table 1). Caution should be paid in the presence of adenomyosis, which
can lead to diagnostic confusion.
Malignant disease of cervix
cancer is the second most common gynecological malignancy worldwide.
The International Federation of Obstetrics and Gynecology (FIGO) (Table
2) recommends clinical staging based on physical exam, lesion biopsy,
chest radiography, cystoscopy, and sonography if indicated. This
approach has inherent inaccuracies (34%-39% discrepancy between clinical
and surgical staging) in advanced stage disease and does not address
nodal involvement. MR imaging has proven to be an excellent modality to
evaluate tumor size, extent, and nodal involvement(Figure 7).21
The real strength of MR imaging for cervical carcinoma is the high negative predictive value of 95% for parametrial invasion.23 A
study has documented 100% negative predictive value of MR imaging for
bladder or rectal invasion, suggesting that MR imaging can obviate
invasive procedures, such as cystoscopy, proctoscopy, and sigmoidoscopy,
and thus can reduce staging costs and morbidity.24 For the
detection of advanced stage disease, sensitivities for MR imaging (53%)
and CT (42%) are much higher than FIGO clinical staging (29%).25
With a criterion of a minimal axial diameter of more than 1 cm,
improved accuracy of 93.0% with a sensitivity of 62.2% and specificity
of 97.9%has been reported.26
knowledge of the spectrum of MR imaging features of various physiologic
variations and pathologic conditions that affect the female pelvis is
essential for establishing an accurate diagnosis and guiding further
management. MR is a reliable staging method for preoperative assessment
of endometrial and cervical carcinoma.
Part 2 of this article is available in the May 2012 issue on the Applied Radiology website: www.appliedradiology.com.
- Johnson W, Taylor MB, Carrington BM, et al. The value of hyoscine butylbromide in pelvic MRI. Clin Radiol. 2007;62:1087-1093.
- Punwani S. Contrast enhanced MR imaging of female pelvic cancers: Established methods and emerging applications. Eur J Radiol. 2011;78:2-11.
- Namimoto T, Awai K, Nakaura T, et al. Role of diffusion-weighted imaging in the diagnosis of gynecological diseases. Eur Radiol. 2009;19:745-760.
- Thomassin-Naggara I, Fournier LS, Roussel A, et al. [Diffusion-weighted MR imaging of the female pelvis]. J Radiol. 2010;91:431-438;quiz 439-440.
VN, Semple SI, Gilbert FJ, Parkin DE. Diffusion-weighted magnetic
resonance imaging in the early detection of response to chemoradiation
in cervical cancer. Gynecol Oncol. 2008;111:213-220.
M, Matsuzaki K, Nishitani H. Diffusion-weighted magnetic resonance
imaging of endometrial cancer: Differentiation from benign endometrial
lesions and preoperative assessment of myometrial invasion. Acta Radiol. 2009;50:947-953.
Y, Matsuki M, Nakai G, et al. Body diffusion-weighted MR imaging of
uterine endometrial cancer: Is it helpful in the detection of cancer in
nonenhanced MR imaging? Eur J Radiol. 2009;70:122-127.
Tamai K, Koyama T, Saga T, et al. The utility of diffusion-weighted MR
imaging for differentiating uterine sarcomas from benign leiomyomas. Eur Radiol. 2008;18:723-730.
- Koyama T, Togashi K. Functional MR imaging of the female pelvis. J Magn Reson Imaging. 2007;25:1101-1112.
- Chandler TM, Machan LS, Cooperberg PL, et al. Mullerian duct anomalies: From diagnosis to intervention. Br J Radiol. 2009;82:1034-1042.
- Olpin JD, Heilbrun M. Imaging of Müllerian duct anomalies. Clin Obstet Gynecol. 2009;52:40-56.
- Troiano RN, McCarthy SM. Mullerian duct anomalies: imaging and clinical issues. Radiology. 2004;233:19-34.
- Agrawal G, Riherd JM, Busse RF, et al. Evaluation of uterine anomalies: 3D FRFSE cube versus standard 2D FRFSE. AJR Am J Roentgenol. 2009;193:W558-562.
Kurman RJ, Kaminski PF, Norris HJ. The behavior of endometrial
hyperplasia. A long-term study of “untreated” hyperplasia in 170
patients. Cancer. 1985;56:403–412.
- Murase E, Siegelman
ES, Outwater EK, et al. Uterine leiomyomas: Histopathologic features, MR
imaging findings, differential diagnosis, and treatment. Radiographics. 1999;19:1179-1197.
I, Daraï E, Nassar-Slaba J, et al. Value of dynamic enhanced magnetic
resonance imaging for distinguishing between ovarian fibroma and
subserous uterine leiomyoma. J Comput Assist Tomogr. 2007;31:236-242.
- Bazot M, Cortez A, Darai E, et al. Ultrasonography compared with
magnetic resonance imaging for the diagnosis of adenomyosis: Correlation
with histopathology. Hum Reprod. 2001;16:2427-2433.
- Ascher SM, Arnold LL, Patt RH, et al. Adenomyosis: Prospective comparison of MR imaging and transvaginal sonography. Radiology. 1994;190:803-806.
K, Togashi K, Ito T, Morisawa N, et al. MR imaging findings of
adenomyosis: Correlation with histopathologic features and diagnostic
pitfalls. Radiographics. 2005;25:21-40.
- Koyama T, Tamai K, Togashi K. Staging of carcinoma of the uterine cervix and endometrium. Eur Radiol. 2007;17:2009–2019.
Nagell JR Jr, Roddick JW Jr, Lowin DM. The staging of cervical cancer:
Inevitable discrepancies between clinical staging and pathologic
findings. Am J Obstet Gynecol. 1971;110:973-978.
- Togashi K, Nishimura K, Sagoh T, et al. Carcinoma of the cervix: Staging with MR imaging. Radiology. 1989;171:245-251.
Kaji Y, Sugimura K, Kitao M, Ishida T. Histopathology of uterine
cervical carcinoma: Diagnostic comparison of endorectal surface coil and
standard body coil MRI. J Comput Assist Tomogr. 1994;18:785-792.
AG, Ghosh S, Alexander-Sefre F, et al. Can MRI rule out bladder and
rectal invasion in cervical cancer to help select patients for limited
EUA? Gynecol Oncol. 2006;101:244-249.
- Hricak H, Gatsonis C, Chi DS, et al. Role of imaging in pretreatment
evaluation of early invasive cervical cancer: Results of the intergroup
study American College of Radiology Imaging Network 6651-Gynecologic
Oncology Group 183. J Clin Oncol. 2005;23:9329-9337.
- Kim SH, Kim SC, Choi BI, Han MC. Uterine cervical carcinoma: Evaluation of pelvic lymph node metastasis with MR imaging. Radiology. 1994;190:807-811.