**4. MRI technique**

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 from bowel motion.

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 normal tissue.

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