**3. Radiologic evaluation of endometriosis**

Radiologists are often involved in the diagnosis and pre-operative assessment of the disease: an accurate pre-operative evaluation of the endometrial implants (location, size and depth of penetration) could help the surgeon to perform a radical surgical excision in cases in which severe fibrosis and adhesions hide deep lesions and impede laparoscopic evaluation.

Imaging methods that are used in the daily practice to diagnose endometriosis are ecotomografy, especially Transvaginal Ultrasound (TVUS) and Magnetic Resonance Imaging (MRI).

TVUS provides high resolution images of the pelvic organs, providing reliable information in patients with both acute and chronic pelvic pain [7].

The classic endometrioma on TVUS appears as an area of low and homogenous echoes.

TVUS has been reported to be the best method for discriminating between endometriotic and non-endometriotic cysts, with a sensitivity of 83% and a false positive rate of 7%. The addition of CA-125 evaluation does not improve the diagnostic accuracy of TVUS, thus indicating TVUS alone to be the least expensive instrument for identifying the presence of endometriomas [8,9].

The role of TVUS for the assessment of deep pelvic endometriosis has been recently reported, with conflicting results. TVUS is apparently more accurate than Rectal Endoscopic Ultrasound (RES) for predicting deep pelvic endometriosis in specific locations and should be the first line imaging method in this setting [10]. RES appears to be the best technique for evaluating the depth of bowel infiltration by endometriosis [11].

The role of MRI in the diagnosis of endometriosis has increased after 1987, when Nishimura *et al. [12]* demonstrated the value of this imaging method in the diagnosis of endometriomas. Then the use of MRI for the evaluation of deep endometriosis was proposed by Siegelman *et al. [13]*, who studied its role in analysing solid pelvic masses. More recently other investigators [14] showed the promising results of MRI for the specific evaluation of deep endometriosis.

Also dynamic MR imaging has been tested for this purpose, showing a good accuracy in the differential diagnosis of nodular endometriosis from other pathologic conditions of abdominal wall and pelvis [15].

Pelvic Endometriosis: A MR Pictorial Review 451

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

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

chronic bleeding with accumulation of high concentration of iron and protein in

endometriomas (arrows in A).

mass proved to be a dermoid syst.
