5.1

muscle and varying amounts of connective tissue.

Leiomyomas may occur as single or multiple lesions and are most typically located in the uterine corpus (90%) and only rarely in the cervix (5%) or uterine liga- ments and vagina. They are distinguished by location as either submucosal, intramural, or subserosal leiomyo- mas. Five to 10% of leiomyomas arise submucosally or protrude into the uterine cavity. Subserosal leiomyomas may occasionally mimic a solid mass of the ovaries.

Typically, a myomatous uterus is diagnosed by the gynecologic examination and leiomyomas are detected by ultrasound. MR imaging is currently considered the most accurate imaging technique for the detection, characterization and localization of leiomyomas (Ta- ble 2). The high spatial resolution with visualization of even the smallest leiomyomas (e.g., at the angle of a fal- lopian tube), reliable characterization (e.g., subserosal leiomyoma), and not least the precise morphologic de- piction make MR imaging an excellent modality prior to organ-preserving surgical or nonsurgical interven- tions and also for lesion characterization [1–3].

Introduction

Each diagnostic modality used for assessing gynecolog- ic disorders has its strengths and limitations. The use of all imaging modalities available in a serial diagnostic procedure is time-consuming and does not help to re- duce health care spending. Proper selection of imaging modalities can improve management of gynecologic disorders and preclude unnecessary procedures. In gen- eral, sonography is the diagnostic modality of first choice in most benign gynecologic disorders, whereas MR imaging and CT are best used for gynecologic ma- lignancies (Table 1).

To make optimal use of the diagnostic potential of CT and above all of MR imaging in the evaluation of gy- necologic disorders, the radiologist needs a thorough knowledge of the pathologic-anatomic changes and how they affect imaging. This article discusses the use of MR imaging and CT of benign and malignant tumors of the uterus and ovaries with special emphasis on radio- logic-pathologic correlation.

Leiomyomas

Leiomyomas are the most common tumors of the uter- us. They are benign and are present in 30%–40% of women of child-bearing age. They consist of smooth Contents

Introduction . . . 535

Leiomyomas . . . 535

Adenomyosis . . . 539

Endometrial Polyps . . . 540

Endometrial Carcinoma . . . 541

Cervical Carcinoma . . . 542

Benign Adnexal Masses . . . 546

Ovarian Carcinoma . . . 548

References . . . 550

MRI and CT

of the Female Pelvis

Bernd Hamm, Rahel A. Kubik-Huch, Claudia Kluner

5.1

Table 1. Imaging modalities for various gynecologic disorders

Disorder 1st Modality 2nd Modality

Endometrial carcinoma TVUS MRI

Cervical carcinoma MRI

Leiomyoma/adenomyosis TVUS MRI

Adnexal masses TAUS/TVUS MRI

Ovarian cancer TVUS CT/MRI

TVUS transvaginal ultrasound, TAUS transabdominal ultrasound

Table 2. Sensitivity of imaging modalities for benign disorders of the uterus

Disorder Sensitivity

MRI TVUS

Adenomyosis 0.73 0.59–0.74

Leiomyoma 0.97–1.0 0.49–0.83

Polyps 0.48 0.48

TVUS transvaginal ultrasound

From [2, 3]

536 Bernd Hamm, Rahel A. Kubik-Huch, Claudia Kluner

Lesion characterization and assessment of the mor- phologic relationship is best achieved on T2-weighted pulse sequences, which should be obtained in two planes, whereas T1-weighted images are particularly useful in demonstrating hemorrhage. Contrast-en- hanced MR imaging does not add to the characteriza- tion of leiomyomas but is a useful diagnostic tool for as- sessing the degree of infarction after treatment by ute- rine artery embolization (Fig. 1) [4, 5].

Leiomyomas of the uterus have a typical appearance at MR imaging. On T2-weighted images, they are depict- ed as roundish lesions of low signal intensity (in con- trast to malignant tumors) with smooth borders and are clearly demarcated from the higher signal intensity of the myometrium (Figs. 1–3) [6, 7]. The lesions are sur- Fig. 1A–D. Intramural leiomyoma (arrow) in the posterior wall of the uterus. A Transverse T2-weighted fast spin-echo (FSE) image depicting the large leiomyoma. The intranodular hyperintense ar- eas indicate degenerative changes. B Histologic specimen (H&E staining) with densely packed cellular bundles of smooth muscle without degenerative changes (not taken from this case). C Trans-

verse T1-weighted contrast-enhanced spin-echo image before ute- rine artery embolization showing well-perfused leiomyoma with- out any perfusion deficit. D Transverse T1-weighted contrast-en- hanced spin-echo image 3 months after uterine artery emboliza- tion. Significant volume reduction and loss of perfusion

Fig. 2. Multiple leiomyomas of the uterus. Sagittal T2-weighted

spin-echo (SE) image. The largest leiomyoma is of intramural lo-

cation, the smaller submucosal one protrudes into the uterine cav-

ity (white arrow). Submucosal, intramural, and subserosal leiom-

yomas in one patient

rounded by a pseudocapsule of compressed neighbor- ing tissue. The rim surrounding a leiomyoma may occa- sionally show dilated lymphatic clefts and veins as well as slight edema. These changes produce a narrow hy- perintense rim around the otherwise hypointense le- sion on T2-weighted images. Such a rim is present in about one-third of patients with leiomyomas [8]. T1-

weighted images only show an enlarged uterus and do not visualize the leiomyomas, which are isointense rela- tive to the surrounding uterus.

The anatomic localization of leiomyomas by MR im- aging is straightforward. Submucosal leiomyomas ele- vate the endometrium or they may be stalked and pro- trude into the uterine cavity (Fig. 4). Due to their low Fig. 3A, B. Multiple leiomyomas of the uterus. A Sagittal T2-weight-

ed spin-echo (SE) image of small leiomyomas in the anterior wall and one large myoma in submucosal location with protrusion into

the uterine cavity. B Gross specimen. Note the good morphologic correlation between MR imaging and the resected specimen

Fig. 4A–C. Submucosal leiomyomas in patients presenting with dysmenorrhea. A Sagittal T2-weighted spin-echo (SE) image. The low signal intensity suggests a leiomyoma rather than an endome- trial polyp. B Contrast-enhanced CT shows a submucosal lesion

but one cannot say whether it is a submucosal leiomyoma or an en-

dometrial polyp. C Gross specimen with large leiomyoma protrud-

ing into the uterine cavity

538 Bernd Hamm, Rahel A. Kubik-Huch, Claudia Kluner

signal intensity, leiomyomas are reliably distinguished from endometrial polyps or endometrial cancer. Intra- mural leiomyomas are easily demarcated from the high- intensity myometrium. Larger subserosal leiomyomas may initially be seen as pelvic masses. Their low signal intensity, however, should give rise to the suspicion of a

leiomyoma (differential diagnosis: ovarian fibroma).

The demonstration of a stalk-like connection to the uter- us (T2-weighted image) makes the diagnosis (Fig. 5).

Besides their location, leiomyomas may be distin- guished by the presence or absence of degenerative changes. Nondegenerated leiomyomas are of nearly ho- Fig. 4C.

Fig. 5. Subserosal leiomyoma. Sagittal T1-weighted contrast-en- hanced image. The stalk-like connection to the uterus and the sig- nal void vascular structures between the mass and the uterus (bridging vascular sign) (white arrow) proves the lesion to be a subserosal leiomyoma rather than an ovarian tumor

Fig. 6A, B. Leiomyoma with red degeneration. A Transverse T1- weighted contrast-enhanced FSE image of an intramural leiomyo- ma 24 days after uterine artery embolization detects no perfusion

of the leiomyoma. B Transverse unenhanced T1-weighted FSE im-

age of the same lesion demonstrates hemorrhages as areas of high

signal intensity (arrow)

mogeneous hypointensity on T2-weighted images. De- generative changes are depicted as hyperintense intra- tumoral areas (T2-weighted image) (Fig. 2). Such chang- es are seen in up to 60% of all leiomyomas, particularly in large ones. The most common types of degeneration seen in leiomyomas are hyalinization (hypointense on T2-weighted image), cystic and myxoid degeneration (hyperintense on T2-weighted image) [9]. Hemorrhages are less common (so-called red degeneration) and can be identified as areas of high signal intensity on T1- weighted images with high or varying signal intensity on T2-weighted images – depending on the time of bleeding (Fig. 6). The demonstration of typical calcifica- tions within the hypointense lesion is rather difficult by MR imaging, but this is irrelevant for the differential di- agnosis given the characteristic appearance of leiomyo- mas as described above.

Adenomyosis

Adenomyosis is defined as the presence of aberrant en- dometrium within the myometrium. Since the ectopic endometrium in adenomyosis consists nearly exclusive- ly of tissue of the basal layer, it is not affected by hormo- nal stimulation and, as a rule, does not contain blood (in contrast to endometriosis, which is characterized by the aberrant occurrence of functional endometrial tissue).

The incidence of adenomyosis of the uterus is higher than would be expected on clinical grounds; it is dem- onstrated histologically in up to 25% of all hysterecto- mies [10, 11]. In a quarter of all cases, adenomyosis is as- sociated with leiomyomas.

Symptoms typically manifest in the fourth to fifth decade of life, with a higher incidence in multiparous

women. The physical examination demonstrates an en- larged uterus, which is of a lower consistency compared to a myomatous uterus.

It is important to reliably differentiate adenomyosis from leiomyomas, since the latter can be removed by myomectomy with preservation of the uterus, whereas hysterectomy is the treatment of first choice in sympto- matic adenomyosis, though uterine artery embolization seems to be a promising nonsurgical alternative [12].

Differentiation of adenomyosis and leiomyomas by MR imaging is no problem. Adenomyosis is diagnosed on T2-weighted images. The decisive diagnostic criter- ion is a pathologic thickening of the low-intensity junc- tional zone to over 12 mm (Figs. 6, 7) [13, 14]. A thicken- ing of the junctional zone to 5 mm – as initially pro- posed – should no longer be used as the threshold for diagnosing adenomyosis, since such thickening may al- so be present in the normal uterus (e.g., transient con- tractions) and thus produce false-positive findings [15].

The thickened junctional zone frequently contains punctiform areas of hyperintensity (Fig. 7). If the latter are depicted on T2-weighted images only, they most likely correspond to cystic glandular tissue. If such small hyperintense foci are present on both T1- and T2- weighted images, they typically represent small hemor- rhages. Adenomyosis may be focal or diffuse. In the dif- fuse form, the changes affect the entire uterus (Fig. 7), which may show pronounced enlargement. The focal form is characterized by a circumscribed thickening of the junctional zone and blurring of its border towards the myometrium (Fig. 8).

Contrast-enhanced MR imaging does not yield any additional information for the diagnostic assessment of adenomyosis or for differentiation from leiomyomas [10].

Fig. 7A, B. Diffuse adenomyosis of the fundus uteri. A Sagittal T2- weighted SE image. Generalized thickening of the junctional zone with isolated hyperintense spots. B Histologic specimen (H&E

staining, not taken from this case) with ectopic endometrial tissue

in the myometrium showing glandular (arrow) and cystic portions

(curved arrow), which appear hyperintense on T2-weighted images

540 Bernd Hamm, Rahel A. Kubik-Huch, Claudia Kluner

Endometrial Polyps

Polyps of the endometrium are seen in about 10% of all uteri – typically in postmenopausal women. The major- ity of polyps arise in the fundus. Less than 1% of endo- metrial polyps show malignant transformation in the form of endometrial cancer. Symptoms are irregular or persistent bleeding. Postmenopausal bleeding is caused by endometrial polyps alone in over 20% of the cases. In many instances, however, endometrial polyps cause no symptoms at all.

Polyps are again best diagnosed on T2-weighted MR images, ideally in two planes (sagittal and transverse).

On T2-weighted images, polyps are isointense or slight- ly hypointense relative to the surrounding endometri- um (Fig. 9); large polyps may distend the uterine cavity.

Polyps are not depicted on T1-weighted images. Follow- ing intravenous administration of a contrast agent, en- dometrial polyps show pronounced enhancement, com- parable to the surrounding endometrium [10]. Endo- metrial polyps are differentiated from submucosal leiomyomas on the basis of their different signal inten- Fig. 8A, B. Focal adenomyosis. A Sagittal T2-weighted SE image. Focal thickening (arrow) of the junctional zone of the uterus. B Histolog- ic specimen (H&E staining, not taken from this case) with ectopic endometrial tissue in the myometrium

Fig. 9A, B. Endometrial polyp. A Sagittal T2-weighted SE image.

The endometrial polyp is of slightly lower signal intensity com- pared to the endometrium. MR imaging does not permit distinc-

tion of an endometrial polyp from a polypous endometrial carci-

noma. Regular and intact junctional zone of the myometrium. B

Gross specimen

sities on T2-weighted images (leiomyoma: hypoin- tense). In inconclusive cases, the differentiation is fur- ther facilitated by a contrast-enhanced study (leiomyo- ma: slighter enhancement).

Endometrial Carcinoma

Endometrial cancer is the most frequent malignancy of the female genital tract. The majority of patients are postmenopausal women; the incidence in women below the age of 40 years is only 2%–5%. The most common symptom of endometrial carcinoma is the occurrence of postmenopausal bleeding, which is often its only manifestation.

Endometrial carcinoma invades the myometrium but rarely extends through the serosa into the abdomi- nal cavity. The cervix is involved in about 10% of cases.

Lymphatic and hematogenous spread of endometrial cancer occurs later than in cervical carcinoma. There is a close correlation between lymphatic spread and the depth of myometrial invasion [16, 17]. Superficial infil- tration of the myometrium (stage Ib) is associated with lymph node metastases in 3% of cases only, whereas over 40% of patients with deep myometrial invasion (stage Ic) have lymph node metastases. Thus, the extent of myometrial invasion is an important prognostic fac- tor.

The most important examination for confirmation of endometrial cancer is fractional abrasion (fractionation in order to exclude or confirm involvement of the endo- cervix, corresponding to stage II disease). Transvaginal ultrasound reliably depicts the depth of myometrial in- filtration in stage I endometrial cancer but is unsuitable for general tumor staging (e.g., extension of the tumor to the uterine cervix) [18, 19].

Because of the excellent depiction of myometrial in- filtration and tumor staging as a whole, contrast-en- hanced MR imaging performs best in the pretreatment evaluation of endometrial carcinomas compared to ultrasonography and CT [20]. The MR imaging findings provide an optimal basis for therapeutic decision-mak- ing (e.g., hysterectomy with or without lymphadenecto- my, chemotherapy, or gestagen treatment).

T2-weighted images depict endometrial carcinomas as hyperintense masses, typically seen as pathologic thickening of the endometrium (Fig. 10), which may oc- casionally contain heterogeneous areas of decreased signal intensity. Since these changes are not specific for endometrial cancer but are also seen in endometrial hy- perplasia, endometrial polyps or coagulated blood, the diagnosis is based on the histologic findings [21]. A hy- perintense disruption of the junctional zone is indica- tive of myometrial infiltration, and the depth of infiltra- tion can likewise be assessed by MR imaging. T2- weighted imaging in two planes is essential for precise-

ly determining the depth of myometrial invasion. De- marcation of the tumor from surrounding myometrium may occasionally cause problems on T2-weighted imag- es. Errors in the staging of endometrial carcinoma pri- marily occur in large polypous endometrial carcinomas (which only rarefy the myometrium but do not invade it) and large leiomyomas, in the presence of congenital anomalies, if the uterus is small and atrophic and when the zonal anatomy is missing [22]. Intravenous adminis- tration of a contrast agent is generally indicated for MR imaging of endometrial carcinoma [4, 23–26]. The can- cer shows less pronounced enhancement than the sur- rounding myometrium, which improves the determina- tion of the tumor borders (Fig. 10). Contrast-enhanced imaging furthermore improves the differentiation of vi- tal tumor portions from areas of necrosis or fluid accu- mulation (e.g., hematometra or pyometra).

Staging of endometrial cancer by MR imaging is based on the International Federation of Gynecology and Obstetrics (FIGO) classification.

In stage I disease, the tumor is confined to the ute- rine corpus. Since there is considerable variation in prognosis, stage I is further subdivided as follows:

Ia Tumor confined to the endometrium

Ib Tumor infiltration of the inner half of the myometri- um (relative to the thickness of the myometrium) Ic Tumor extension to the outer half of the myometri-

um

Stage Ia disease is suggested when the hypointense junctional zone is intact. If there is insufficient delinea- tion of the junctional zone, which is typically the case in an atrophic uterus, a stage Ia tumor can be assumed when the lesion is smoothly and clearly demarcated from the myometrium. In stage Ib tumors, there is dis- ruption of the junctional zone or the border between the tumor and myometrium becomes irregular, with confinement of the pathologic process to the inner half of the myometrium (Fig. 10). Stage Ic disease is charac- terized by deep myometrial involvement extending to the outer half of the myometrium. Assessment of myo- metrial tumor infiltration is facilitated by contrast-en- hanced T1-weighted imaging.

In stage II disease, the tumor has invaded the cervix or endocervix.

Stage III and IV endometrial cancer can likewise be assessed by MR imaging. Both stages are characterized by extension of the tumor beyond the uterus (stage III:

tumor confined to the pelvis; stage IV: tumor invasion

extending beyond the true pelvis or infiltration of the

mucosa of the urinary bladder or rectum). An infiltra-

tion of the wall of the bladder or rectum is seen on T2-

weighted images as a focal and hyperintense disruption

of the otherwise hypointense muscular layer. Further

criteria for tumor growth beyond the uterus are an ir-

regular uterine surface and the presence of ascites.

542 Bernd Hamm, Rahel A. Kubik-Huch, Claudia Kluner

Lymph node assessment by MR imaging uses the same criteria as computed tomography and relies solely on an enlarged transverse nodal diameter (>1 cm).

However, MR imaging has a slight advantage over CT in that it is far better in T-stage assessment, from which in- direct conclusions can be drawn for differentiating re- active from tumorous lymph node enlargement.

Cervical Carcinoma

The incidence of cervical carcinoma shows two peaks, the first between 35 and 45 years of age and the second between 65 and 75 years. Invasive cervical carcinoma occurring in women younger than 35 years frequently is of a highly aggressive type. It is now commonly as- sumed that cervical carcinoma develops in several steps (dysplasia – carcinoma in situ – microinvasive carcino- ma). Dysplasia and carcinoma in situ together are Fig. 10A–D. Endometrial carcinoma; stage Ib.A Sagittal T2-weight-

ed SE image. Generalized pathologic thickening of the endometri- um. Additionally hyperintense mass in the anterior wall of the uterus, which disrupts the narrow hyperintense junctional zone and invades the inner half of the myometrium. B Sagittal T1-

weighted contrast-enhanced SE image. Significantly better demar-

cation of the hypointense invading carcinoma relative to the hy-

perintense intact myometrium. C , D Gross specimen confirms the

involvement of the inner half of the myometrium

termed cervical intraepithelial neoplasia (CIN). Micro- carcinoma (stage Ia2: invasion depth <5 mm and sur- face extension <7 mm) is already associated with lymph node metastases in up to 10% of cases [16].

The initial symptoms are bleeding outside menstru- ation and vaginal discharge. Regular screening is very helpful for detecting cervical cancer since no other gy- necological tumor is that easily accessible to physical examination.

Imaging is not used for detecting cervical carcinoma but for staging of already proven carcinoma. Because of the high soft-tissue contrast and the free selection of imaging planes, MR imaging is far superior to CT in staging cervical carcinoma. Most information is provid-

ed by T2-weighted imaging. On T2-weighted images, a cervical carcinoma is depicted as a lesion of high signal intensity, which is clearly seen against the low signal in- tensity of the cervical stroma (Fig. 11). On T1-weighted images, cervical cancer is not delineated adequately since it is of the same signal intensity as the cervical stroma, the myometrium, and the vagina. T1-weighted imaging, however, is suitable for assessment of larger tumor masses in the parametria and for lymph node staging. In contrast to endometrial cancer, intravenous administration of a contrast agent yields only little ad- ditional information for the detection and staging of cervical carcinoma [27–30]. However, dynamic con- trast-enhanced MR imaging seems to be a useful tool

Fig. 11A–C. Cervical carcinoma, stage Ib. A , B Sagittal and trans- verse T2-weighted FSE images. The cervical carcinoma is depicted as a hyperintense mass invading the cervix and uterine corpus.

Despite the huge size, both the sagittal and the transverse image

show that the cancer is still surrounded by a hypointense rim of

cervical stroma (arrows). Normal appearance of the hypointense

vaginal wall without signs of tumor infiltration. C Histologic spec-

imen (H&E staining, not taken from this case), lateral border of the

carcinoma surrounded by normal myometrium

544 Bernd Hamm, Rahel A. Kubik-Huch, Claudia Kluner

for predicting and objectively assessing the outcome of radiotherapy [31, 32].

Staging of cervical carcinoma by MR imaging is based on the FIGO criteria. The preclinical form (stage Ia) can only be demonstrated microscopically and is not seen on MR images. Stage Ib carcinoma is restricted to the cervix (with or without involvement of the corpus

uteri). The most important criterion on T2-weighted MR images is a fully preserved hypointense rim of nor- mal cervical stroma surrounding the tumor (Fig. 11b).

Assessment of the preserved normal cervical stroma is facilitated by T2-weighted imaging in two planes. In ad- dition, the parametrial tissue appears inconspicuous and the normal border relative to the surrounding fatty

Fig. 12A, B. Cervical carcinoma, stage IIa. A Sagittal T2-weighted FSE image. Hyperintense mass, predominantly located in the ante- rior part of the cervix with obliteration of the anterior vaginal for- nix. Normal appearance of the posterior vaginal fornix. B Gross specimen: ulcerated cervical carcinoma infiltrating the anterior vagina (curved arrow), no infiltration of the posterior vaginal for- nix (arrow)

Fig. 13A, B. Cervical carcinoma; stage IIb. A, B Sagital and trans-

verse T2-weighted FSE images. The tumor has completely invaded

the cervical stroma on the right but leaves a narrow rim of hy-

pointense cervical stroma on the left (white arrow). Besides the

carcinoma invades the cranial two-thirds of the anterior vagina

meanwhile the posterior vaginal fornix seems to bee intact

tissue is preserved. In stage IIa disease, the tumor in- volves the upper and/or middle third of the vagina. In- filtration of the vaginal wall is visualized on T2-weight- ed images as a hyperintense disruption of the otherwise hypointense muscle layer (Fig. 12). Stage IIb cervical carcinoma is characterized by infiltration of the para- metria. Advanced parametrial invasion is depicted on

both T2- and T1-weighted images as a mass within the parametria. The most important criterion of possible parametrian infiltration is the complete disruption of the low-intensity cervical stroma by (hyperintense) tu- mor tissue (Fig. 13) [33].

In stage IIIa, the hyperintense tumor extends to the lower third of the vagina (because lymphatic drainage is different in this area, the inguinal lymph nodes should be examined as well in these cases!). Infiltration of the pelvic wall or obstruction of one or both ureters by the tumor corresponds to stage IIIb disease (Fig. 14). In- volvement of the muscle tissue of the pelvic wall can best be demonstrated on T2-weighted images as a hy- perintense infiltration.

Invasion of the urinary bladder and/or rectum (stage IVa) is seen on T2-weighted images as a hyperintense disruption of the otherwise hypointense muscle of the wall of the urinary bladder or rectum (Fig. 15). If the findings are inconclusive with regard to bladder or rec- tum infiltration, an additional contrast-enhanced study will show contrast enhancement in areas of tumor in- volvement. The FIGO classification only takes into ac- count involvement of the mucosa of the urinary bladder or rectum, since only this can be assessed endoscopical- ly. MR imaging, on the other hand, can also demonstrate tumorous infiltration in the underlying muscular layers.

In addition to allowing for T-stage assessment, MR imaging is able to depict lymph nodes, peritoneal seed- ing, and organ metastases (Fig. 16).

Fig. 14A, B. Cervical carcinoma, stage IIIb. A, B Sagittal and trans- verse T2-weighted FSE image. The tumor (black arrow) has invad- ed the right parametrium and caused obstruction of the right ure- ter (white arrow)

Fig. 15. Cervical carcinoma, stage IVa. Sagittal T2-weighted FSE

image. The cervical carcinoma has infiltrated the muscular layers

of the urinary bladder, depicted as a hyperintense disruption of

the otherwise hypointense muscle wall (arrow)

546 Bernd Hamm, Rahel A. Kubik-Huch, Claudia Kluner

Benign Adnexal Masses

The ovaries are divided into a cortex containing the fol- licle at different stages of maturation, and a medulla. In young women, the average ovary weighs 8 g and shrinks from age 30 to less than 2 g after menopause [24]. The ovaries can be visualized in virtually all premenopausal women by MR imaging with adequate spatial resolu-

tion. The cortex shows lower signal intensity than the medulla on T2-weighted images. Single functional cysts in the cortex are hypointense on T1-weighted images and hyperintense in T2-weighted sequences [34].

Pelvic inflammatory disease is a largely clinical, bac- teriological and sometimes sonographic diagnosis, typ- ically made in women of childbearing age. Half of the cases result from ascending infection by sexually trans- Fig. 16A, B. Cervical carcinoma with peritoneal spread. A Sagittal

T2-weighted FSE image depicting a large volume of ascites. B Sag- ittal T1-weighed contrast-enhanced image depicts peritoneal

spread as generalized; pronounced enhancement of the thickened peritoneal layer

Fig. 17A, B. Pyosalpinx. A, B Coronal T2-weighted SE and T2- weighted contrast-enhanced SE image depicts a fluid collection at the right pelvic wall with contrast enhancement of surrounding

thickened adnexal wall. Two months later (after antibiotic thera-

py) the lesion was no longer detectable by MR imaging

mitted pathogens such as Neisseria gonorrhoeae and Chlamydia trachomatis, which migrate into the perito- neum from the cervix via the endometrium and fallo- pian tube [35, 36]. Known risk factors include multiple partners and use of an intrauterine contraceptive device (IUD). Women with an IUD have a three to seven times higher risk of acute salpingitis [37].

A pyosalpinx arises from infundibular adhesion and pus retention in a patient with salpingitis. Liquefaction and the pooling of pus between the organs of the true pelvis lead to abscesses of the pelvis, adnexa, and pouch of Douglas; suppurative infection of the fallopian tube and ovary results in the tubo-ovarian abscesses [38, 39]

seen in up to one-third of admissions for acute salpin- gitis [40]. Tubo-ovarian abscess is clinically almost in- distinguishable from adnexitis and is normally diag- nosed by ultrasound [41–43].

The typical CT image of an ovarian abscess is that of central liquefaction (i.e., fluid-equivalent density) sur- rounded by a rim of increased contrast uptake; inflam- mation may also involve the surrounding fatty tissue [43] (Fig. 18). The MR image is heterogeneous, general- ly showing iso- or slight hypointensity compared to urine in T1-weighted sequences [44] and hyperintensity on T2-weighted images (Fig. 17). However, if the abscess contains blood or high protein levels, it may be visual- ized with varying signal intensities, even on T1-weight- ed images. Delineation of the abscess border is usually unclear, though the wall shows increased signal inten- sity on contrast-enhanced images. Edema and inflam- matory infiltration give a heterogeneous appearance to the surrounding fat. A chronic untreated or antibiotic- resistant abscess leads to an increase in the number of visible blood vessels [45].

A benign ovarian cyst, whether a functional follicu- lar cyst, single cyst, cystadenoma, dermoid (mature te- ratoma), endometrioma or polycystic ovary, is typically

thin-walled and sharply delineated (Figs. 19–21). The purpose of CT and MRI is to differentiate these lesions from ovarian carcinoma. The primary criteria of malig- nancy are a diameter greater than 4 cm, intralesional solid elements or septations, wall thickening, and necro- sis; ancillary criteria include lymph node hypertrophy, ascites and infiltration of surrounding structures [46].

CT or MRI evidence of intralesional fat is indicative of a dermoid cyst, accounting for 10%–25% of all ovar- ian neoplasms. On MRI, the fat component can be dis- tinguished from hemorrhage – both are hyperintense Fig. 18. Tubo-ovarian abscess. Contrast-enhanced CT: multilocu-

lated left adnexal lesion with central liquefaction and contrast-en- hancing thickened wall (arrow). There is a fluid collection in the pouch of Douglas. (+: uterine cavity)

Fig. 19A, B. Functional hemorrhagic ovarian cyst. A Contrast-en-

hanced CT. Small cystic, thin-walled lesion of the right ovary with-

out septations. B Axial T1-weithted SE image: small circumscribed

thin-walled cystic adnexal lesion on the left with hyperintense

content

548 Bernd Hamm, Rahel A. Kubik-Huch, Claudia Kluner

on T1-weighted images – by using fat suppression. Fat–

fluid levels may be visualized, together with a solid nod- ule arising from the tumor wall (Rokitansky nodule or dermoid plug) [45]. The protuberance contains mature differentiated tissue such as hair, fat, and teeth or other calcifications, the latter being clearer on CT than MRI (Fig. 21).

Ovarian Carcinoma

Carcinoma of the ovary is the third most common ma- lignancy of the female genital tract after carcinoma of the cervix and endometrium. However, its poor progno- sis means that it accounts for approximately half of all deaths from gynecologic malignancy [47, 48]. Manage- ment of clinically suspected disease involves a staging laparotomy with histologic confirmation of the diagno- sis, identification of tumor spread, and debulking prior to chemotherapy. The latter is usually followed by a sec- ond-look laparotomy to assess the response.

The strength of MRI lies in its ability, first, to deter- mine the origin of a pelvic mass using multiplanar im- aging and high soft-tissue contrast and, secondly, to dif- ferentiate between malignant and benign lesions with a Fig. 20. Benign cystadenoma of the ovary. Sagittal T2-weighted FSE image showing a large, thin-walled adnexal cystic structure with numerous septations. Pathology after surgery confirmed the diagnosis of benign cystadenoma

Fig. 21A–C. Mature teratomas. A Contrast-enhanced CT clearly

demonstrates a fat-containing pelvic mass with surrounding cal-

cifications and a solid, contrast-enhancing nodule (arrow), the so-

called Rokitansky nodule or dermoid plug. B Axial contrast-en-

hanced T1-weighted SE image: adnexal lesion with a fat–fluid lev-

el and the so-called Rokitansky nodule.C Macroscopic specimen of

a mature teratoma containing fat and hair

60%–99% accuracy [49–55] using the above primary and ancillary criteria. MRI findings are not specific for the cell types of ovarian carcinoma, although some fea- tures are more typical of one histology rather than an- other. Mucinous tumors, for example, may mimic multi- ple simple cysts, but frequently display imaging features similar to those of other mucin-laden tumors, i.e., an intermediate to high signal intensity on T1- and T2- weighted images [56].

Imaging does not yet have a clearly defined place in the staging and management of ovarian carcinoma, since many centers still view surgical exploration as the diagnostic gold standard in both primary and recurrent disease. However, surgery can be avoided in cases where the laparoscopic and/or imaging diagnosis is unambig- uously benign. Imaging also helps in preoperative plan- ning and follow-up of chemotherapy by providing accu- rate information on tumor spread (Figs. 22–24).

In our view, CT is the modality of choice alongside transvaginal and abdominal ultrasound in staging ovar- ian carcinoma, as it is less expensive and more widely available than MRI. However, ovarian cancer metasta- sizes directly via peritoneal seeding and lymphatic para-aortic and peritoneal spread. Compared to solid viscera, imaging of peritoneal seeding presents particu- lar problems due to the extensive area of the peritone- um, anatomic variation, low tissue contrast, and motion artifacts. Gadolinium-enhanced MRI has proven super- ior to nonenhanced MRI and CT in demonstrating per- itoneal metastases with reported sensitivities of 62%–86% [57–61]. However, MRI is not only more ex- pensive, but also more demanding on the often weak- ened patients as well as time-consuming. Its advantages are that it can be used in renal failure and situations in

Fig. 22A, B. Serous papillary ovarian carcinoma. A Transverse T2- weighted FSE image showing an adnexal semi-solid cystic mass of the left ovary. The diagnosis of a malignant serous papillary ovar- ian adenocarcinoma was confirmed by the histologic examina- tion. B Histologic specimen (H&E staining) of a malignant serous papillary ovarian carcinoma (not taken from this case)

Fig. 23. Serous ovarian carcinoma sagital T2-weighted FSE image

showing an adnexal semi-solid/cystic structure, confirmed as a

serous cystadenocarcinoma

550 Bernd Hamm, Rahel A. Kubik-Huch, Claudia Kluner

which the radiation exposure associated with CT is con- traindicated, e.g., during pregnancy.

Up to 10% of ovarian tumors are metastatic with pri- maries typically in the gastrointestinal tract, breast, uterus, or thyroid. Metastases containing a significant amount of signet-ring cells are termed Krukenberg’s tu- mors. Bilateral contrast-enhanced lesions are generally seen on CT or MR imaging (Fig. 24). Prognosis is poor with a 1-year post-detection mortality of 90% [35, 44].

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