MR Imaging of the Female Pelvic Region1 Mary C. Olson, MD Harold V. Posniak, MD Clare M. Tempany, MD ChristineM. Dudiak, MD

Magnetic resonance (MR) imaging is a valuable technique for noninvasive evaluation of the female pelvic region. This article presents the normal anatomy and abnormalities of the female pelvis. MR imaging may be more useful than clinical evaluation or other imaging modalities in diagnosing or staging developmental anomalies, leiomyomas, adenomyosis, endometrial or cervical carcinoma, vaginal neoplasms, ovarian cysts, endometriosis, teratomas, polycystic ovaries, or other ovarian masses. It could potentially replace laparoscopy as a more useful tool in the diagnosis ofuterine anomalies. MR imaging is generally capable of helping determine whether a pelvic mass is uterine or adnexal in origin and may be used to characterize some adnexal masses. In some cases, MR imaging is used to differentiate recurrent disease from posttreatment fibrosis, which aids in treatment planning. INTRODUCTION

U

Magnetic resonance (MR) imaging has become a valuable technique for noninvasive evaluation of the female pelvis. It offers advantages over computed tomography (CT) and sonography in the evaluation of many pelvic abnormalities. In this article, we present normal MR anatomy of the female pelvis and discuss the role of MR in the evaluation of congenital anomalies of the uterus and vagina, staging of gynecologic malignancies, diagnosis of uterine leiomyomas and adenomyosis, differentiation

of uterine

and

diagnosis

and

extrauterine

of recurrent

masses,

characterization

of several

adnexal

masses,

tumor.

TECHNIQUE Patients are usually supine and breathing quietly during examination. Partial distention of the bladder is preferred, as this displaces small bowel loops from the pelvis. Glucagon (1 mg intramuscularly or intravenously) may be administered to reduce motion artifact produced by bowel peristalsis. Routine use of a vaginal tampon is not necessary and may obscure details ofvaginal anatomy. Occasionally additional U

Abbreviation:

FIGO

Index

terms:

sans,

neoplasms,

Endometriosis,

RadloGraphics I

From

H.V.P., tific

assembly.

C

RSNA,

reprint

and

Federation

85.3192

Pelvic

#{149}

ofGynecology organs,

and

abnormalities,

Obstetrics 85.14

#{149} Pelvic

organs,

MR. 85.1214

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or-

85.32 12:445-465

Department

C.M.D.)

Address

85.31, 1992;

the

International

=

ofRadiology, Department

Received requests

Loyola ofRadiology,

August

27;

revision

University Johns requested

Medical Hopkins October

Center, University, 2 and

2160

S First

Baltimore received

Aye,

Maywood,

(C.M.T.).

December

From 20;

accepted

IL 60153 the

1990

(M.C.O., RSNA

December

scien30.

to M.C.O.

1992

445

Figure coronal uterine metrium tiguous

1. Normal uterus in a patient ofreproductive age not taking oral contraceptives. Sagittal (a) and (b) T2-weighted (2,000/80 [repetition time msec/echo time msec]) MR images demonstrate three zones. High-signal-intensity endometrium (E) is separated from the medium-signal-intensity myo(M) by the junctional zone (small arrows). Low-signal-intensity cervical stroma (large arrows) is conwith the junctional zone.

information may be obtained by imaging the patient prone with rectal air insufflation. A complete examination requires both Ti(short repetition and echo times) and T2weighted (long repetition and echo times) pulse sequences. T2-weighted MR images delineate the internal anatomy of the uterus, cervix, and vagina. Ti-weighted images are useful in detecting tumor extension into adjacent fat and lymph node enlargement. Evaluation of signal intensity of pelvic masses on these two pulse sequences aids in tissue characterization. The use of fat suppression pulse sequences may be helpful in some patients to differentiate subacute hemorrhage from fat. Imaging is performed in more than one plane. We generally obtain axial Ti-weighted MR images and sagittal T2-weighted images in all patients.

Additional

the axial, coronal, tamed, depending amination.

The

T2-weighted

images

in

or oblique planes are obon the purpose of the exuterus,

cervix,

vagina,

cul-de-

sac, and tumor extension into the bladder or rectum are best evaluated sagittally. Coronal or axial images are best for evaluating the ovaries, parametria, and adnexae. Axial images are most useful for evaluating the lymph

nodes and developmental anomalies of the vagina. Oblique images that are parallel or perpendicular to the axis of the uterus may

useful U

in some

NORMAL

be

cases. ANATOMY

Uterus On Ti-weighted MR images, the normal uterus has homogeneous low to medium signal intensity. Uterine zonal anatomy is appreciated on T2-weighted images with three discemible signal intensities (Fig 1) (1-6). The S

endometrium

has high

signal

intensity

similar

to or greater than that of fat. The myometrium has medium signal intensity. Between them is the thin, low-signal-intensity junctional zone that is thought to correspond to the innermost portion of the myometrium (5-7). The junctional zone may not be visible as a distinct structure in premenarchal and postmenopausal female patients. The MR appearance of the normal uterus is variable and is influenced by the hormonal status of the patient. During the reproductive years, there is a distinct temporal variation in

uterine

appearance

in different

phases

of the

menstrual cycle (1-3). During the follicular phase, endometrial width typically is 1-3 mm. The endometrial zone is widest during the middle of the secretory phase when it usually

446

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2.

3.

Figures

2, 3. (2) Normal cervix and parametria. Axial oblique T2-weighted MR image (2,000/80) obtained the cervix (black arrow) demonstrates triangular moderate signal intensity of normal parametria arrows). (3) Normal vagina in a patient ofchildbearing age. Axial T2-weighted MR image (2,000/80) at the level of the pubic symphysis shows a normal vagina (large arrows) with peripheral low- and medium-signal-intensity areas. Short arrows = urethra.

through (white obtained central

measures (1,2,6). ing

the

5-7 mm Myometrial

but may increase signal intensity

menstrual

cycle

and

to iO mm varies dur-

is maximal

during

the

secretory phase (8). In patients taking oral contraceptives, uterme zonal anatomy is less distinct and the endometrial width is usually 4 mm or less (1,2, 6).

This

appearance

premenarchal

is similar

and

Postmenopausal estrogen

may

greater

.

than

to that

postmenopausal women

taking

an

endometrial

has

homogeneous,

have

seen

in

patients.

normal

mediate

width

4 mm.

cervix signal

intensity

on

inter-

Ti-weighted

MR

images. Zonal anatomy of the cervix is appreciated on T2-weighted images (Figs ia, 2). The central zone has high signal intensity similar to that of the endometrium. This is believed to represent cervical epithelium and mucus

(6,8).

Surrounding

this

is the

homoge-

neous, low-signal-intensity cervical stroma, which is contiguous with and similar in appearance to the junctional zone. In some women, a third, outer zone of intermediate signal intensity and contiguous with the myometrium is seen (8). The parametria have moderate signal intensity on T2-weighted MR images

May

(Fig

1992

Vagina

On Ti-weighted MR images, the vagina has low signal intensity, which provides excellent contrast between it and the surrounding fat. On T2-weighted images, two zones are identifled (Fig 3): the low-signal-intensity vaginal wall and the higher-signal-intensity central epithelium and mucus (9). The vaginal wall is easily

differentiated

from

the

urethra

and

the

rectum on T2-weighted images. The hormonal status of the patient affects the size of the vagina, the thickness of the central portion, and the signal intensity characteristics of the vaginal wall (9). Changes in

exogenous

Cervix

The

.

thickness

of the

vaginal

epithelium

parallel

estrogen levels (9) . Pregnant patients, newborn girls, and patients in the middle of the secretory phase of the menstrual cycle demonstrate thick central portions on MR images. Signal

intensity

characteristics

of the

vaginal

wall reflect water content, which is dependent on hormonal stimulation. During pregnancy and the middle of the secretory phase of the menstrual cycle, the signal intensity of the vaginal wall increases. Low signal intensity is demonstrated during the early proliferative and late secretory phases (9).

2).

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a. Figure

b. 4.

(2,200/70)

Normal (b)

ovaries

in a patient

MR images

demonstrate

ofreproductive normal

ovaries

age. Axial Ti-weighted

(600/20)

(a) and T2-weighted

(arrows).

a. Figure

5.

patient with duplication.

the uterus

T2-weighted MR images (2,000/80) of a uterus didelphys and partial vaginal (a) Axial image obtained at the level of

demonstrates

uterine

two

horns

of simi-

with functioning endometrium (E). (b) Two cervices (arrows) are demonstrated 2 cm caudad to a. (c) A partially obstructed, fluid-filled, left vagina (arrow) is seen 6 cm caudad to a. It joins the right vagina distally. lar size

C.

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a

b

Figure 6. Septate (2,300/70) obtained divided by a septum caudad

to a demonstrates arrow = dilated,

straight

.

uterus in a patient with agenesis of the left kidney. (a) Axial T2-weighted MR image at the middle of the uterus shows a single uterine horn with two endometrial canals (large arrow). M = myometrium. (b) Axial T2-weighted image (2,300/70) obtained 2 cm extension of the atretic left ureter.

septum

(large

des

can

of reproductive usually

be

weighted

MR images,

the

is similar

ovary

Signal

with

intensity

the

with

follicles

ages.

are

identified

the to that

increases

signal

isointense

age,

intensity that

Identification

(6,10).

signal with

of fat

(Fig on

of follicles

ovaOn

Ti-

intensity

ofmuscle T2

of the

hyperintense

normal

(Fig

4b).

in a more

cost-effective

ing

women

stroma

If present, im-

useful

in

differentiating the ovary from fluid-filled small bowel and vessels. The ovaries in postmenopausal women are not consistently seen. Normal fallopian tubes are usually not identified at any age (6).

OF

ABNORMALITIES PELVIC REGION U

.

THE

FEMALE

Uterus

DevelopmentalAnomalies.-The lence of congenital in 200-600

(6).

uterine

Patients

anomalies with

uterine

pt-evais one anoma-

lies have an increased prevalence of infertility, spontaneous abortion, breech presentation, and premature labor. Findings from physical examination and imaging studies such as sonography and hysterosalpingography are often inconclusive, and many gynecologists rely on laparoscopy to help differentiate types

May

1992

the

of

T2-weighted

is very

into

4a).

weighting,

ovarian

arrow)

cervix

(curved

arrow).

Small

of uterine anomalies. MR imaging has the potential to replace laparoscopy in the identification of different types of uterine anomalies

Adnexa

In patients

straight

many

manner, an

invasive

thereby procedure

spar(6,

11,12). The female reproductive tract develops from the mUllerian ducts that fuse to form the fallopian tubes, uterus, and upper four-fifths of the vagina. Several fusion abnormalities may occur, and these can be differentiated with MR imaging. Partial or complete failure of the m#{252}llerian ducts to fuse results in a bicornuate or didelphic uterus (6). Two separate uterine horns and a fundal cleft are seen on MR images of these patients. Each uterine horn in the dideiphic uterus (Fig 5) has a cer‘ix, whereas a single cervix is present in the bicornuate uterus. Septate uteri result from failure of resorption of the midline fusion (6). The septum may be partial (within the endometnal canal) the endocervical gle uterine horn ofvariable length tour of the uterus

or complete (extending into canal). On MR images, a sinis seen containing a septum (Fig 6). The external conis normal.

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449

Figures 7-9. (7) Uterine leiomyomas. Sagittal T2weighted MR image (2,200/80) shows two large, welldefined intramural leiomyomas (black arrows) displacing the endometrial canal (white arrow) posteriorly. (8) Multiple leiomyomas in a patient with endometrial carcinoma. Axial T2-weighted MR image (2,300/70) demonstrates multiple intensity, and

ened

leiomyomas location. The

as a result

ofvarying endometrial

of endometrial

carcinoma.

size, signal canal (*) is wid-

White

ar-

row = submucosal leiomyoma, lower black arrows = intramural leiomyoma, higher black arrows = subserosal leiomyomas. (9) Large, degenerated leiomyoma. Sagittal

T2-weighted MR image (2,000/80) defined leiomyoma (arrows) with tensity

caused

demonstrates areas ofhigh

a wellsignal in-

by degeneration.

Asymmetric duplications may occur, and, in these cases, a rudimentary uterine horn that is variable in size is present. The rudimentary horn may communicate with the normal horn or cervix or be noncommunicating. The vagina and cervix are usually normal (6). Distinction among these anomalies is important because they are treated differently. Rudimentary uterine horns are generally excised. Septate uteri can be treated in an outpatient setting with transvaginal resection of the septum. The bicornuate uterus is not always repaired, but, if it is, a laparotomy is necessary.

Leiomyomas. -Leiomyomas are the most common uterine tumors, with an approximate prevalence of 30%-40% in women of reproductive age (i 3) . The tumors are classifled on the basis of their location. Submucosal lesions project into the endometrial cavity, intramural lesions are within the substance of

450

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the myometrium, and subserosal lesions project outside of the uterus. The cervix is involved in less than 5% ofpatients (13). The location of uterine leiomyomas is of clinical significance, since symptoms and treatment differ among the types (13). Subserosal lesions may be asymptomatic but may simulate an adnexal mass precipitating unnecessary surgery. Intramural lesions near the internal os may obstruct labor or, if near the ostium of the fallopian tube, may cause infertility. Submucosal lesions may cause hypermenorrhea and predispose the patient to spontaneous abortion. Submucosal leiomyomas may be treated with hysteroscopic removal, but treatment of intramural and subserosal lesions requires a laparotomy. MR imaging helps accurately assess the number, location, and size of uterine leiomyomas (Figs 7-9) (14-i8). This is useful for those patients who will undergo either surgi-

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12

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Figure 10. Adenomyosis. Sagittal T2-weighted MR image (2,500/80) obtained through the uterus shows a poorly defined low-signal-intensity mass (curved arrows) caused by diffuse adenomyosis involving most of the posterior myometrium. A second smaller lesion is present anteriorly (straight arrow).

nant extrauterine tumor. In this situation, a specific diagnosis ofleiomyoma should not be made unless its origin within the myometrium is unequivocal (18). Assessing the relation of the serosa of the uterus to the adnexal mass is important. occurs in premenopausal women and clinically may mimic leiomyoma. The frequency of adenomyosis found in specimens obtained at hysterectomy is reported to be i5%-27% (i7). Typically, women present with hypermenorrhea, dysmenorrhea, and an enlarged uterus. An exact diagnosis is usually not possible until the resected uterus is examined pathologically. Preoperative differentiation from leiomyomas may be important, since the definitive treatment for adenomyosis is hysterectomy, whereas leiomyomas can be treated with myo-

Adenomyosis.-Adenomyosis

cal or medical treatment. The sensitivity and accuracy of MR imaging in depicting the location of uterine leiomyomas have been shown to be greater than either ultrasound (US) or hysterosalpingography (14). Preoperative localization of leiomyomas is important in planning myomectomy and in determining whether sufficient myometrium will remain after reconstruction so that the childbearing function can be preserved. Response to hormonal therapy may be quantitatively assessed with MR imaging. On MR images, uterine leiomyomas are well-circumscribed masses that have medium or low signal intensity on Ti-weighted images. Signal intensity on T2-weighted images varies from low to high (13-15). Histologically, the homogeneous low-signal-intensity leiomyomas consist of dense whorls of smooth muscle without degeneration. These tend to be smaller than the inhomogeneous leiomyomas that increase in signal intensity on T2-weighted images. This increase in signal intensity in the larger leiomyomas is due to degeneration intensity

and

(Fig lack

9) (14).

of signal

Very change

low

signal

with

dif-

ferent repetition and echo times are highly suggestive of calcification. MR has proved useful in distinguishing leiomyomas from other solid pelvic masses when sonographic findings are indeterminate (18). If the mass is completely or predominately of low signal intensity on T2-weighted images, the diagnosis ofleiomyoma is highly likely. If a mass adjacent to the uterus is primarily hyperintense on T2-weighted images, it may be a degenerated leiomyoma or a benign or malig-

May

1992

mectomy if uterine preservation is desired. Histologically, adenomyosis is defined as the presence of endometrial glands and stroma within the myometrium (17,19). The endometrial foci are surrounded by hypertrophic smooth muscle. The endometrial glands of adenomyosis are basal and are resistant to hormonal stimulation. This is in contrast to endometriosis, which follows the same cyclic changes as the normal endometrium. Accumulation of blood, which is typical of endometriosis, is an unusual occurrence in adenomyosis. Adenomyosis may be diffuse, involving a large portion of the uterus, or focal. In contradistinction to leiomyomas, the boundaries between areas of adenomyosis and myometrium are irregular and indistinct. On Tiweighted MR images, no abnormality may be apparent. On T2-weighted images, adenomyosis typically exhibits low signal intensity similar to that of the junctional zone and is subjacent to the endometrium (Fig 10) (16,17, 19). Occasionally, small foci of high signal intensity on both Ti- and T2-weighted images resulting from hemorrhage may be seen within the lesions.

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451

Table 1 FIGO staging

of Endometrial

Carcinoma

FIGO Stage

Criteria

IA Gi,2,3 lB Gi,2,3

Tumor Invasion

IC Gi,2,3

Invasion

hA Gi,2,3 lIB Gi,2,3

limited to endometrium to less than halfofthe

to more

than

Endocervical glandular Cervical stromal invasion

lilA

Gi,2,3

Tumor

IIIB IIIC

Gi,2,3 Gi,2,3

Vaginal metastases Metastases to pelvic

WA G1,2,3

Tumor Distant

WB

invades

serosa

invasion metastases

Figures

widening of the endometrial region of the fundus. There myometrial

invasion

canal (arrow) is no evidence

or cervical

involvement.

(2,000/80) by tumor myometrium in a = incidental permission, from

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and/or and/or

adnexa paraaortic

only

and/or lymph

positive

peritoneal

cytologic

findings

nodes

and/or bowel mucosa to intraabdominal and/or

inguinal

lymph

nodes

carciT2slight

in the of deep (Re-

printed, with permission, from reference 30.) (12) Stage I endometrial carcinoma with deep sion. Sagittal (a) and coronal (b) T2-weighted images caused of the

myometrium

involvement

to bladder including

1 1, i2 (1 1) Stage I endometrial noma in a postmenopausal woman. Sagittal weighted MR image (2,300/70) demonstrates

myometrium

haffofthe

inva-

MR

show endometrial widening (*) with extension into the outer half (straight arrows). Curved arrow nabothian cyst. (Reprinted, with reference 30.)

Olson

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12

Number

3

Figures strates canal

30.)

13, 14. (13) the endometi-ial (large

arrows)

(14)

Stage

Stage II endometrial carcinoma. Sagittal T2-weighted MR image (2,200/70) demoncavity distended by tumor (T) with an intact junctional zone (small arrows). Cervical

is widened

as a result

III endometrial

fundal tumor with metastases the inner half of the myometrium the left ovary (0) has relatively

compatible caudad

with

to B. (D) A discrete

Endometrial

tumor

with

is the

in U.S.

invasive

high signal intensity but is less intense (C) No evidence of tumor in the uterine mass

(arrows)

permission,

from

is seen

reference

Carcinoma.-Endometrial

carcinoma

found

to the cervix (arrows),

a metastasis.

C. (A, B, D reprinted.

of tumor extension. (Reprinted, with permission, from reference Axial T2-weighted MR images (2,000/70) demonstrate a primary and left ovary. (A) At the uterine fundus, the tumor extends into indicating superficial invasion. (B) Four centimeters caudad to A

carcinoma.

fourth

women

most

and

malignancy

of the

(20).

Histologic

grade

ease,

and

ofmyometrial

depth

the

cancer

most

female

common genital

of tumor,

including

are

addressed

findings

shown

effective

in evaluating

from

in up to has been endome-

trial carcinoma ranging between

with overall accuracy rates 82% and 92% for staging (24-26) and between 74% and 87% for assessing depth of invasion (24-27). This has im-

tients

tion

implications clinicians would

therapy

in case in determining

benefit

and

from

assisting

the

most

frequently

encoun-

endometrium may have an irregular inhomogeneous signal intensity. Discrete tumor nodules, which may have low or medium signal intensity relative to the endometrium, may be seen within it (24,29). The low-signal-intensity junctional zone is important in evaluating myometrial invasion. If the zone is intact, invasion is essentially excluded. Segmental disruption is a reliable indicator ofmyometrial invasion (24,25,28). In the absence of a junctional zone, irregularity of the endometrium-myometrium interface is evidence of invasion (24). Superficial invasion is manifested as extension of the tumor into the inner haffofthe myometrium. Extension into the outer half indicates deep invasion

is inaccurate MR imaging

aiding

MR images,

tered manifestation of endometrial carcinoma is widening of the high-signal-intensity endometrial canal (24-29). This may be focal or diffuse and can be due to the tumor, uterine secretions,

curettage, (23).

portant

to

(21). lymph and

dilation and 51% ofpatients to be

1 cm caudad

are

and

staging,

stroma

invasion

in the revised staging system of the International Federation of Gynecology and Obstetrics (FIGO) (Table 1) (22). Clinical

cervical

of dis-

ultimately

survival

tract

of the

stage

features to regional recurrence,

5-year

most

in D. This is is seen 2 cm

30.)

On prevalent

the most important prognostic These factors directly relate node involvement, to tumor to

replacing

than that of the bladder isthmus (curved arrow)

management, which preoperative

in planning

pa-

(Fig

12)

or

both

(Figs

1 1-16)

(28).

The

(22).

radia-

surgical

procedures.

May

1992

Olson

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RadioGraphics

#{149}453

Figures 15, 16. (15) demonstrates bilateral dometrial

tumor

Stage

III endometrial

carcinoma.

iliac lymphadenopathy

(arrows).

carcinoma. Sagittal T2-weighted There is a large serosal metastasis with permission, from reference

(T).

(Reprinted,

MR image (straight 30.)

The cervix can be involved by direct extension of tumor from the endometrial cavity, or there may be discrete metastases (Figs 13, i4d) ens

(24,30). the

vical

Direct

cervical

extension

canal

of tumor may

interruption

may

manifest extension

of the

myometrium

the

(24,30).

teristics

cer-

with

on MR imof tumor

low-signal-intensity

or without

associated

sal masses or parametrial infiltration ovaries and adnexa may be involved spread or have discrete metastases pelvic of the

wid-

invade

stroma.

Stage III disease ages as transmyometrial with

and

As with

CT,

lymphadenopathy nodes (Fig i5). have

not

been

assessment

The

by direct (Fig 14)

of metastatic

is based on Signal intensity useful

sero(24).

the size charac-

in differenti-

ating metastatic from hyperplastic lymphadenopathy (3i). The role of MR imaging in evaluating invasion of the bladder or rectum in stage NA disease is unclear. Unless advanced, differentiation between contiguity and frank invasion is difficult. Pelvic manifestations of stage WB disease

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ascites,

Olson

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implants,

Axial *

=

(2,000/70) arrows),

proton-density-weighted widened endometrial shows ascites

the

canal.

MR image (2,000/20) (16) Stage IV en-

endometrial

(A), and omental

canal

cake

distended

(curved

by

arrow).

and omental “cakes” (Fig 16) (24,30). These are usually readily apparent on MR images. The diagnosis of endometrial carcinoma needs to be established histologically, as MR imaging cannot help differentiate between endometrial carcinoma and other causes of endometrial widening such as endometrial hyperplasia or blood clot (Fig 17) (24). In a series studied by Hricak et al (24), three of 51 patients with clinically suspected endometrial carcinoma had widening of the endometrium as a result ofbenign disease. Because of the potential for curative surgery in its early stages, the possibility ofendometrial carcinoma should be considered if expansion of the endometrial canal is detected on MR images ofthe female pelvis.

Cervical

Carcinoma.-Invasive cervical cancer is the third most common gynecologic malignancy (32). Treatment has been largely dependent on clinical staging, which is based on the FIGO staging classification (Table 2). Patients with stage lB and limited stage hA disease are usually surgical candidates. Some of these patients undergo preoperative radiation therapy if tumor volume is large. Treatment for more advanced stages (stage IIB or higher) consists of radiation therapy only.

Volume

12

Number

3

Table 2 FIGO staging

ofCervical

Carcinoma

FIGO

Stage

Criteria

0

In

I IA lB

Confined to cervix Microinvasive Clinically invasive

II IIB

Extending beyond cervix Vaginal involvement Parametrial involvement

III lIlA IIIB

Extending to pelvic wall Vaginal involvement Parametrial involvement

NA

Spread Spread

ILk

NB

situ

(before

invasion)

to bladder to distant

(extension

to corpus

but

not

should

to pelvic

or lower

third

to pelvic

wall

be disregarded)

or lower

wall

third

of vagina

of vagina

or rectum organs

Figure 17. Endometrial hyperplasia. Sagittal weighted MR image (2,200/80) of a postmenopausal

woman

metrial

canal

plasia. imaging

This

with marked (F) as a result case demonstrates

and the need

T2-

distention ofthe endoofendometrial hyperthe limitations of MR

for histologic

diagnosis.

Macroscopic tumor extension to the bladder, rectum, and pelvic sidewall is reliably excluded on MR images. As with endometrial carcinoma, MR imaging has not been proved to be more successful than CT in the detection

Clinical staging is known Many of the clinical staging patients

with

particularly

greater

to be inaccurate. errors occur in stage IIA disease,

than

in assessing

the

parametria,

pelvic

sidewalls, and lymph nodes. MR imaging is reported to be effective in staging, with accuracy in the range of 76%-83% (33-36). Accuracy for assessment of parametrial involvement is reported to be 82%-92% (34-37). In addition, the high predictive value of MR imaging

trial cal

May

in determining

disease

is a valuable

the

absence

contribution

of metastatic

disease

in normal-sized

lymph nodes. In a recent study of 30 patients with cervical carcinoma, the overall accuracy for detection of pelvic lymph node metastasis was 77% with CT and 78% with MR imaging (36). Currently, MR imaging may not be necessary for every patient with cervical carcinoma. If tumor volume is not a factor in treatment planning or can be accurately assessed clinically, MR imaging is not indicated. If tumor volume is large or the location is such that it is difficult to evaluate, MR imaging will be of value. MR imaging is particularly useful for patients with concomitant pelvic masses such as leiomyomas or adnexal masses and presently is the best imaging procedure for evaluating

the

pregnant

patient

with

cervical

carci-

U

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noma.

of parame-

to clini-

staging.

1992

Olson

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Figures (2,300/80)

18,

the cervix, strated on hysterectomy (2,300/20) invasion of vic sidewall.

19. (18) Stage hA cervical (b) MR images demonstrate

carcinoma. Sagittal Ti-weighted a poorly defined cervical mass

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signal

and axial T2-weighted in the posterior lip of

replacing the low-signal-intensity cervical stroma (curved arrow). Vaginal extension is not demonthese images. (19) Stage NA cervical carcinoma in a patient who previously underwent subtotal for benign disease. Sagittal T2-weighted (2,300/80) (a) and axial proton-density-weighted (b) MR images demonstrate extension ofthe tumor (T) into the lower third ofthe vagina and the posterior wall of the bladder (straight arrows). Curved arrow in b = extension to the left pel-

Cervical carcinoma is often not detectable on Ti-weighted MR images. On T2-weighted images, the tumor has high signal intensity that makes it easy to differentiate from the low

(600/20) (a) (straight arrow)

intensity

U

of the

Olson

Ct

surrounding

a!

cervi-

cal stroma (Figs 18, 19). Preservation of the low-signal-intensity outer stripe of the cervical stroma has been shown to be a reliable indicator that the tumor is confined to the cervix (34-37). If full-thickness stromal invasion is present, there is a relatively high frequency of microscopic parametrial invasion even if no parametrial abnormality is seen on MR images.

VolumC

12

Number

3

‘7 -

.

‘

0

b. a. Figure 20. Primary vaginal carcinoma. (a) Axial Ti-weighted MR image (600/20) demonstrates largement of the vaginal wall posterolaterally (large arrows) and infiltration into the paravaginal arrows). (b) Axial T2-weighted MR image (2,500/80) shows that the tumor (arrows) increases sity. Note poor definition between the tumor and the adjacent fat on this image.

.

Vagina

Developmental Anomalies. -Several developmental abnormalities may affect the vagina. Vaginal agenesis, which may be partial or complete, occurs in one in 4,000-5,000 women (38) . Partial agenesis is most commonly associated with a functioning midline uterus and cervix. Patients with complete agenesis may or may not have a uterine body or cervix (38). Duplication anomalies of the vagina most commonly occur with other m#{252}llerian duct fusion anomalies and are associated with uterine and cervical duplication (Fig 5c). Because a portion of the vagina develops from the urogenital sinus, abnormalities of the urogenital sinus may affect the vagina. Patients

with

may

present

lies

symptoms

developmental

with

that

are

often

vaginal

confusing

anoma-

signs

dependent

and on

how

the anomaly has affected the other portions of the genital tract. Abnormalities of sexual differentiation may be particularly difficult to evaluate with physical examination alone. In almost

often nosis.

every

case,

laparoscopy MR imaging

tion

of the

with

a single,

vagina

cal management ofMR findings

May

1992

some

form

of imaging

are needed to make can be useful in the and

noninvasive

may (9,38).

other

genital

organs

examination.

be planned

and

a diagevaluaSurgi-

on the

VaginalNeopkwns.-Primary the vagina constitutes logic malignancies

only (Fig 20)

diffuse enfat (small in signal inten-

carcinoma of i%-2% of gyneco(39). Neoplastic

disease of the vagina is most often the result of a metastasis (Fig 2 i) or direct extension (Fig 22) from a primary cervical, vulvar, or rectal carcinoma. Although MR imaging has been shown to be useful in determining the location and extension of primary carcinomas, the accuracy of MR staging has not been reported. In assessing metastatic disease, MR imaging has demonstrated a sensitivity of 95%, specificity of9O%, and an overall accuracyof92% (39). On Ti-weighted MR images, both primary and metastatic tumor often have medium to low signal intensity similar to that of the vaginal wall. Enlargement of the vagina may be detected, but intravaginal extent of the tumor is difficult to determine. Extravaginal tumor extension is well demonstrated because of the difference in signal intensity of the tumor and paravaginal fat. T2-weighted images help provide the best assessment of tumor size and location within the vagina. Both primary and metastatic tumors have high signal intensity in contrast to the medium to low signal intensity of the vaginal wall.

basis

Olson

Ct

a!

U

RadioGrapbics

U

457

‘I

a

T

‘

--

-,

iL

.

-

21a. Figures 21, 22 (21) Vaginal cuffmetastasis. Sagittal (a) and axial (b) T2-weighted MR images (2,000/ 70) demonstrate a large metastasis (T) from a primary colonic carcinoma in the vaginal cuff of a patient who previously underwent a hysterectomy for benign disease. Note metal artifact from wire sutures

in the

anterior

abdominal

wall.

(22)

P--,

-

Direct

invasion of the vagina by rectal carcinoma. Sagittal T2-weighted MR image (2,000/70) shows a large rectal carcinoma (T) invading the proximal vagina (large straight arrows) and posterior lip ofthe cervix (small straight arrow). E = endometrium, curved open arrow = normal distal vagina, curved solid arrow = incidental perineural cyst.

.

Adnexa

The appearance of adnexal masses on MR images is variable depending on content (water, fat, hair, fibrous tissue, or pus) and pulse sequence. MR imaging generally enables the determination of whether a pelvic mass is uterine or adnexal in origin, but there is considerable overlap between the MR appearance ofvarious adnexal masses, both benign and malignant (i8). Several adnexal masses including ovarian cysts, polycystic ovaries, cystic teratomas, and some endometriomas have been reported to have characteristic MR features that may aid in differential diagnosis (40-45). Ovarian Cysts.-One ofthe strengths of MR imaging with regard to tissue characterization is its usefulness in distinguishing unequivocally between simple fluid (low protein con-

458

U

RadioGrapbics

U

Olson

Ct

a!

L 22.

tent, no hemorrhage) lesions. Simple cysts circumscribed,

and

signal intensity on and homogeneous lar to that of urine, (Fig 23). The signal intensity the cyst contains a

and all other are thin walled, have

homogeneous

types are

of well low

Ti-weighted MR images high signal intensity, simion T2-weighted images of ovarian hemorrhage.

cysts varies if Hemorrhagic cysts are usually well circumscribed and homogeneous. Their walls are smooth and typically thin, but wall thickness is variable. They usually have high signal intensity on both Tiand T2-weighted MR images (Fig 24). Fat suppression pulse sequences may be useful in differentiating them from tumors containing fat.

Volume

12

Number

3

23.

24.

Figures 23, 24. (23) (2,000/70) demonstrates ovary

(large

arrows).

cyst. Axial T2-weighted mass (arrows) . High differentiating it from

Simple ovarian cysts in a patient of reproductive age. Axial T2-weighted MR image several well-defined, homogeneous high-signal-intensity follicular cysts in the left Small arrow = incidental intramural uterine leiomyoma. (24) Hemorrhagic ovarian MR image (600/25) demonstrates a well-defined homogeneous high-signal-intensity signal intensity was also seen on T2-weighted images. Spontaneous resolution occurred, an endometrioma.

Figure 25. Endometriosis. Coronal Ti-weighted MR image (600/20) demonstrates multiple endometriomas ofdifferent sizes and signal intensities (arrows).

Endometriosis.-Endometriosis is a common disease in patients of reproductive age; it is found in one-third to one-half of all patients during gynecologic surgery (40). Ectopic endometrial implants most commonly involve the ovaries but may involve many other pelvic structures

including

the

uterine

serosa,

cut-

de-sac, uterine ligaments, fallopian tubes, bowel, and bladder. Endometrial cysts vary in size from millimeters to many centimeters. Multiplicity of lesions and adhesions between lesions and other adjacent structures is char-

May

1992

acteristic (Fig 25) (40-43). Histologically, the lesions consist of endometrial glands, endomenial stroma, and blood that may be new or old. Laparoscopy is the primary procedure used for the diagnosis and staging of endometriosis. MR imaging is very accurate in helping differentiate endometrial cysts from other adnexal masses but does not routinely help identify small implants and adhesions, which are criteria used in staging (40-43). MR imaging may be used to monitor response to treatment or document extent of disease in patients with dense adhesions in whom laparoscopic evaluation is limited. MR imaging has been reported to have a sensitivity of 64%-7i% and a specificity of 60%-80% in detecting endometriosis in patients with known or suspected disease (40, 4 i). In a recent series of 371 patients with a clinically suspected adnexal mass, MR imaging

Olson

Ct

a!

U

RadioGrapbics

U

459

Figure 26. Endometrioma. demonstrate a well-defined is seen on the T2-weighted

Coronal Ti-weighted high-signal-intensity image. Curved arrow

had a sensitivity of 90%, a specificity and an accuracy of 96% in helping endometrial cysts and in enabling tion

of them

from

other

gynecologic

(600/20) (a) and T2-weighted (2,000/70) mass (straight arrow) in the left adnexum. = vaginal tampon.

of 98%, diagnose differentiamasses

(43). In this series, 293 patients had a total of 86 endometrial cysts and 268 other gynecologic masses that were surgically confirmed. Signal intensity of endometrial cysts varies. Most commonly, individual cysts are hyperintense relative to the signal intensity of urine with all pulse sequences. Some are hyperintense on Ti-weighted MR images and hypointense on T2-weighted images (40-42). This is believed to reflect the age of the hemorrhagic fluid. Other features often observed are a hypointense rim and internal shading (a central or peripheral area oflow signal intensity) that are most prominent on T2-weighted images (Fig 26). Ancillary features that aid in MR diagnosis include multiplicity, multilocularity, and adherence of adjacent structures. Cystic Teratomas.-Cystic teratomas account for more than 20% of all ovarian neoplasms and are the most common ovarian tumor found in children and adolescents (6,44). Most occur during the reproductive years. Histologically, cystic teratomas are composed

460

U

RadioGraphics

U

Olson

Ct

a!

(b) MR images Internal shading

of a cyst lined by epithelium containing sebaceous and sweat glands. Tissue from all three germ layers is present, with ectoderm predominating (44). The combined use of US and radiography or CT helps suggest the correct diagnosis in most cases. On US images, many cases go unrecognized or their appearance is more typical ofother ovarian masses. MR imaging has the potential to help correctly diagnose most cystic teratomas without exposing patients to ionizing radiation (6,44). This may be particularly important for pregnant patients. Most cystic teratomas have a fatty component that is a useful distinguishing feature on MR images. This fatty component is isointense relative to subcutaneous fat with all pulse sequences (Fig 27). Chemical shift artifact within or around the lesion indicates the presence of a fat-water interface and is an important diagnostic feature. In a study with MR imaging, 20 of 23 cystic teratomas were prospectively identified (44). Signal intensity similar to that of fat was seen in 22 of 23 teratomas, chemical shift artifact was seen in 20 of 23, and a typical internal pattern consisting of layering or floating debris and palm tree or nodule-like protrusions was seen in 16 of 23. Calcification may be present and, if small, may not be detected with MR imaging. Components other than fat may have a wide variety of signal intensities.

Volume

12

Number

3

a.

b.

Figure 27. mass (large

Cystic straight

attributable T2-weighted

to fat. A larger area image (2,000/80)

neous

fat and

teratoma. (a) Sagittal Ti-weighted arrows in b also). There is a small

a fluid

component

of relatively demonstrates

(curved

low signal isointensity

arrow)

MR image (800/20) focus of high signal intensity ofthe

demonstrates a large adnexal intensity (small arrow) anteriorly,

is noted centrally fatty component

(curved arrow). (b) Sagittal (small arrow) with subcuta-

centrally.

Figure 28. Polycystic ovaries. Coronal T2weighted MR image (2,300/70) demonstrates bilateral ovarian enlargement (arrows) with multiple small subcapsular follicles and abundant central stroma.

The hallmark of polycystic ovarian disease is mild enlargement of both ovaries, which contam multiple small subcapsular follicles. Discrete cysts are often not resolved with transabdominal US or CT. The ovaries of patients with polycystic ovarian disease have been reported to have a characteristic MR appearance (45). On T2-weighted MR images, multiple, small peripheral cysts and abundant, low-signal-intensity central stroma are seen (Fig 28). This appearance, although typical of polycystic ovarian disease, is not pathognomonic and must be correlated with clinical findings. Polycystic Ovaries-Polycystic ovarian disease is a common cause of infertility. Clinical features include secondary amenorrhea, hirsutism, and obesity. Although the cause of polycystic ovarian disease has not been determined, it is believed to be due to a disturbance of the normal female hormonal reproductive feedback system. Follicles in these patients are stimulated long-term, but ovulation

does

May

1992

not

usually

occur

Other Ovarian Masses.-The MR appearance ofother adnexal masses is variable, depending on their cystic, solid, hemorrhagic, or necrotic components. Wide overlap can be seen in benign and malignant neoplasms, which, in many cases, does not allow a distinc-

(45).

Olson

Ct

a!

U

RadioGraphics

U

461

tion

to be

The

likelthood

increasing

made

based

on

MR

of malignancy amount

appearance.

rises

of solid

with

tissue,

but

an an

ovar-

ian carcinoma may have only cystic loculi and septations without solid elements (46). Solid malignant ovarian masses of low signal intensity

on

not

been Ovarian

both

Ti-

and

T2-weighted

images

have

cancer

is typically

postmenopausal ages. Over 70%

patients of patients

diagnosis

MR

seen

in pen-

but may affect have metastases

imaging

has

not

had

and

all at a ma-

jor impact on staging, since this type of cancer spreads primarily through peritoneal dissemination and MR cannot help identify small peritoneal ovarian

implants.

The

malignancies

solid

components

often

have

low

of to inter-

mediate signal intensity on Ti-weighted images and variable signal intensity on T2weighted images, ranging from intermediate

462

U

RadioGraphics

U

U

TUMOR

of malignancy of adjacent metastasis, or distant

RECURRENCE

can be pelvic orretroperitometastasis

VERSUS

FIBROSIS

reported.

(46).

to high. A diagnosis made if involvement gans, intraperitoneal neal lymphadenopathy, is identified.

Olson

Ct

a!

The clinical and CT distinction between residual or recurrent tumor and posttreatment fibrosis may be very difficult. MR imaging has been reported to enable the differentiation between tumor and fibrosis on the basis of signal intensity (47-49). Both have low signal intensity on Ti-weighted images. On T2weighted images, fibrosis has low signal intensity and tumor has high signal intensity (Fig 29). This distinction may be employed for most patients 12-18 months after treatment (47-49). Before this period, inflammation and edema associated with acute radiation change may cause high signal intensity on T2-

Volume

12

Number

3

30.

31.

32a. 32b. Figures 30-32. (30) Peritoneal inclusion cyst (loculated ascites). Sagittal T2-weighted MR image (2,300/ 80) demonstrates homogeneous high-signal-intensity fluid in the cul-de-sac (arrows). E = endometrium. (31) Pelvic abscess. Sagittal T2-weighted MR image demonstrates a fluid collection (large arrows) containing gas (small arrows) in the cul-de-sac. Note large uterus with atypical diffuse medium-signal-intensity myometrium (M) caused by a recent pregnancy. (32) Carcinoma ofthe rectum with parametrial metastasis. Axial Ti-weighted (800/20) (a) and T2-weighted (2,000/70) (b) MR images show the rectal wall (R) diffusely thickened as a result of primary carcinoma. There is direct extension into the pararectal fat (large straight arrows) and a discrete right-sided parametrial metastasis (small arrows) adjacent to the cervix (curved arrow).

weighted images, resulting in an incorrect diagnosis (49). MR imaging has particular value for patients with numerous pelvic cal clips whose CT images are degraded artifact. U

OTHER

Inflammatory

surgiby

PATHOLOGIC

CONDITIONS Many other pathologic processes exist that may be encountered during MR evaluation the female pelvis. Fluid collections including ascites,

peritoneal

celes,

and

May

1992

hematomas

inclusion

may

cysts,

lympho-

be seen

(Fig

of

disease

originating

from

the

female pelvic organs or secondarily involving the pelvis from other sites may be identified (Fig 31). Clinical history and MR findings often allow a correct diagnosis to be made. Extragonadal pelvic malignancies including bladder and colon cancer may be evaluated with MR imaging. Local extent of these lesions can be demonstrated with MR imaging, and involvement of the female pelvic organs can be defined (Fig 32). Pelvic metastases can also be evaluated.

30).

OlsonCta!

U

RadioGraphics

U

463

6.

CONCLUSION

U

MR imaging is a valuable technique evaluation of many abnormalities male pelvis. Congenital anomalies productive tract can be diagnosed sively.

Uterine

leiomyomas

and

can be differentiated and involvement defined. MR imaging is a reliable ing

endometrial

for the of the feof the renoninva-

the

technique and

9.

the

depth of tumor invasion into the myometrium. Radiographic staging ofcervical and vaginal carcinoma can be improved with the use of MR imaging. Uterine and adnexal masses can usually be differentiated when sonographic findings are inconclusive. Several common adnexal masses often have a characteristic MR appearance that may allow a specific

diagnosis

to be

in the

12.

yet

may from

fibrosis and aid in further The exact role MR imaging evaluation

1 1.

made.

In some patients, MR imaging to differentiate recurrent tumor treatment planning.

10.

of the

female

pelvic

be used post-

her assistance script.

in the

preparation

Linda

is

of this

Schomer

1988; Dooms nexal 1986; Mintz

169:169-174. GC, Hricak structures:

If. 1987;

MR evaluation 148:287-290.

2.

3.

4.

Demas

BE, Hricak

imaging:

effects

H, Jaffee

of hormonal diology 1986; 159:123-126. Janus CL, Wiczyk HP, Laufer

i58:639-646. MC, Thickman

Carrington

BM, Hricak

Uterine

N.

Ra-

17.

MR imaging.

RadioGraphics

U

Olson

18.

a!

with

leiomyomas:

Radi-

et at.

SK,

infertile

localization

uterus.

patient:

Uterpre-

MR imaging

versus

Radiology Heinrichs

U, et at.

correlation

of MR, histo-

with

between adeMR imaging.

Radiology 1989; 171:531-534. Mark AS, Hricak H, Heinrichs LW, et al. Adenomyosis and leiomyoma: differential diagno-

MR imaging.

WeinrebJC, poulos R. guishing masses

19.

Radiology

20.

Ct

anoma1990;

pathologic findings, and symptoms. Radiology 1986; 158:385-391. Togashi K, Ozasa H, Konishi I, et al. En-

Radiology

1987;

163:

BarkoffND,

MegibowA,

Demo-

The value of MR imaging in distinleiomyomas from other solid pelvic when sonography is indeterminate.

AJR 1990; Togashi K, nomyosis: ogy 1988;

American figures: ety,

U

RN, Secaf

527-529.

2 1.

464

of the

DA, Patel

in the

US and hysterosalpingography. 1988; 167:627-630. Hricak H, TscholakoffD,

sis with

171:241-243.

findings and 179:409-413.

D, Kressel anomalies. AJR

H, Nuruddin

larged uterus: differentiation nomyosis and leiomyoma

Magnetic

Brown HK, Stoll BS, Nicosia SV, et al. Uterme junctional zone: correlation between histologic 1991;

16.

MR

stimulation.

Ad-

EC. M#{252}llerian duct evaluation. Radiology

CM, Turner

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operative

160:119-123.

RB.

DI, Gussman of uterine

Dudiak

manu-

resonance imaging of the menstrual cycle. Magn Reson Imaging 1988; 6:669-674. McCarthy 5, Scott G, Majumdar S, et al. Uterine junctional zone: MR study of water content and relaxation properties. Radiology 1989;

5.

1986;

H, TscholakoffD. MR imaging. Radiology

14.

for

McCarthy 5, Tauber C, Gore J. Female pelvic anatomy: MR assessment ofvariations during the menstrual cycle and with use of oral conRadiology

JKT.

McCarthy S. MR imaging ology i989; 171:321-322.

15.

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Lee

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Ct

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U

RadioGraphics

U

465