**5. Spectrum of MRI findings**

The diagnosis of endometriosis by means of MRI is based on the combination of two aspects: presence abdominal areas with morphologic and signal intensity abnormalities. Endometriotic lesions appear hyperintense on T1-weighted images and mildly hypointense or hyperintense on T2-weighted images (**Fig. 2A, B**). Gradual variation of signal intensity on T2-weighted images has been described as the "shading" sign (**Fig. 2A**) and it is due to chronic bleeding with accumulation of high concentration of iron and protein in the endometrioma.

Fat saturation allows differentiation between hemorrhagic (endometriomas) and fatty (dermoid cyst) content of cystic lesions (**Fig. 3**). Moreover, it increases detection of small implants.

Use of contrast-enhanced imaging is required to identify solid enhancing nodules within endometriotic cysts when malignant transformation is suspected or to define the extent of inflammation associated with endometriosis.

In our experience, MRI studies are performed with a 1.5 T magnet (Magnetom Symphony; Siemens Erlangen, Germany) and a surface phased-array coil. Patient preparation requires intravenous injection of an antispasmodic drug prior to study in order to reduce artefacts

On the basis of the characteristics of our system, the standard imaging protocol includes a coronal T2-weighted HASTE sequence (half-Fourier single shot turbo spin echo: TR 700 ; TE 89; section thickness 6.0 mm; field of view 350x450 mm; matrix 320; time of acquisition 21 s), transverse T1-weighted turbo spin echo sequences from the iliac crest to the pubic sinfisis (TR 771; TE 9.7; section thickness 4.0 mm; field of view 400 x 219 mm; matrix 512x512; time of acquisition 2:46), transverse, sagittal and coronal T2-weighted turbo spin echo sequences. These sequences allow an initial complete analysis of the pelvic region and a preliminary evaluation of endometriotic lesions, which appear as hyperintense lesions in T1-weighted sequences and mildly hypointense or hyperintense in T2 weighted sequences. The FLASH T1-weighted sequences with fat suppression in transverse, coronal and sagittal plane (Fast Low-Angle Shot 2D: TR 357; TE 4.76; FA 70°; section thikness 4.5 mm; field of view 300x300 mm; matrix 256x256; time of acquisition 1:31) (T1 flash 2d fat sat ) are performed to evaluate adnexal masses because they allow a distinction between a fatty content lesion (for example a teratoma, which appear hypointense in fat-suppressed T1 weighted sequences) and endometriomal cyst (that exhibits a typical hyperintense signal in such sequences). Fatsuppressed MRI is also useful in enhancing the contrast between hemorrhagic implants and

Contrast-enhanced FLASH T1-weighted sequences (gadolinium Gd-DTPA 0.1 mmol/kg is administrated intravenously) are performed in selected cases, expecially when a mural nodule within a hyperintense endometrioma is observed. Finally, the contrast agent is administrated when the initial images carry the suspicion of ureteral infiltration. In such cases we perform FLASH 3D T1 weighted sequences in the coronal plane with MIP recostruction of 1 mm (MR Urography) (TR: 2.96; TE 1.21; section thickness 1.40 mm; field of

The diagnosis of endometriosis by means of MRI is based on the combination of two aspects: presence abdominal areas with morphologic and signal intensity abnormalities. Endometriotic lesions appear hyperintense on T1-weighted images and mildly hypointense or hyperintense on T2-weighted images (**Fig. 2A, B**). Gradual variation of signal intensity on T2-weighted images has been described as the "shading" sign (**Fig. 2A**) and it is due to chronic bleeding with accumulation of high concentration of iron and protein in the

Fat saturation allows differentiation between hemorrhagic (endometriomas) and fatty (dermoid cyst) content of cystic lesions (**Fig. 3**). Moreover, it increases detection of small

Use of contrast-enhanced imaging is required to identify solid enhancing nodules within endometriotic cysts when malignant transformation is suspected or to define the extent of

view 350x490 mm; matrix 384; time of acquisition 20 sec).

**5. Spectrum of MRI findings** 

inflammation associated with endometriosis.

**4. MRI technique** 

from bowel motion.

normal tissue.

endometrioma.

implants.

Fig. 2. Endometriotic lesions appear mildly hypointense or hyperintense on T2-weighted images (A) and hyperintense on T1-weighted images (arrows in B). Gradual variation of signal intensity on T2-weighted images has been described as "shading" sign and is due to chronic bleeding with accumulation of high concentration of iron and protein in endometriomas (arrows in A).

Fig. 3. T1-weighted-fat-suppressed image showing a hyperintense mass on the left ovary and a disomogenous hypointense mass on the right one (A). On T2-weighted sequence (B) the left mass appear hypointense. The left mass proved to be an endometrioma with recent hemorrhage; on the contrary, owing to its appeareance on fat-suppressed sequence, the right mass proved to be a dermoid syst.

Pelvic Endometriosis: A MR Pictorial Review 453

Uterus is usually anteflexed and the anterior cul-de-sac is obliterated due to extensive

Two types of bladder endometriosis have been recognised. One develops exclusively after cesarean section and is considered to result from iatrogenic implantation of decidua. The other, a primary form, is found in women who have not previously undergone surgery on the uterus. Various hypotheses have been proposed to explain the pathogenesis in the latter case. Microscopically, the typical pattern is a focus of endometriosis scattered in the bladder

MRI is reliable for the diagnosis of bladder endometriosis. Endocavitary coil MRI is reliable

On MRI images, bladder endometriosis can be diagnosed as a localized or diffuse bladder wall thickening, or as focal signal intensity abnormality. T2 and T1 weighted images can show a nodular hypointense mass usually located on the anterior upper or posterior bladder

**C D**

Fig. 5. Coronal (A) and sagittal (B) T2-weighted images showing localized bladder wall thickening in the anterior upper bladder wall (blue circles). On fat suppressed T1-weighted coronal (C) and axial (D) images some high signal intensity intra-lesion spots indicating

On fat suppressed T1-weighted FLASH 2d images, some high signal intensity intralesional

adhesions. The patient often complain pain, especially while urinating.

wall. The main feature is the paucity of endometrial-type stroma [17].

wall (**Fig. 5**).

recent haemorrage.

spots are present in some cases.

for establishing the depth of the lesions penetrating into the bladder wall [18].
