Feasibility of diffusion tensor imaging (DTI) with fibre tractography of the normal female pelvic floor

To prospectively determine the feasibility of diffusion tensor imaging (DTI) with fibre tractography as a tool for the three-dimensional (3D) visualisation of normal pelvic floor anatomy. Five young female nulliparous subjects (mean age 28 ± 3 years) underwent DTI at 3.0T. Two-dimensional diffusion-weighted axial spin-echo echo-planar (SP-EPI) pulse sequence of the pelvic floor was performed, with additional T2-TSE multiplanar sequences for anatomical reference. Fibre tractography for visualisation of predefined pelvic floor and pelvic wall muscles was performed offline by two observers, applying a consensus method. Three eigenvalues (λ1, λ2, λ3), fractional anisotropy (FA) and mean diffusivity (MD) were calculated from the fibre trajectories. In all subjects fibre tractography resulted in a satisfactory anatomical representation of the pubovisceral muscle, perineal body, anal - and urethral sphincter complex and internal obturator muscle. Mean FA values ranged from 0.23 ± 0.02 to 0.30 ± 0.04, MD values from 1.30 ± 0.08 to 1.73 ± 0.12 × 10(-)³ mm²/s. Muscular structures in the superficial layer of the pelvic floor could not be satisfactorily identified. This study demonstrates the feasibility of visualising the complex three-dimensional pelvic floor architecture using 3T-DTI with fibre tractography. DTI of the deep female pelvic floor may provide new insights into pelvic floor disorder

Value of MRI performed with phased-array coil in the diagnosis and pre-operative classification of perianal and anal fistulas (Ruolo della RM eseguita con bobina phased array nella diagnosi e stadiazione preoperatoria delle fistole anali e perianali)

PURPOSE: To assess the value of MRI performed with phased-array coil in the diagnosis and preoperative staging of perianal and anal fistulas. MATERIALS AND METHODS: 20 patients (13 with Crohn's disease) with clinical evidence or suspicion of anal fistulas underwent pelvic MRI (1.5 T) performed with phased-array coil. Images were obtained in the axial and coronal planes using TSE T2-weighted high resolution sequences with and without fat suppression, T2-weighted HASTE and T1-weighted FLASH sequences, with and without fat suppression, before and after gadolinium enhancement. The following parameters were considered: presence of a fistula and relation with the sphincters, and presence of abscesses or complications. All patients underwent surgery. The MRI and surgical findings were assessed using the Park's fistula-in-ano classification and the St. James MR imaging classification of perianal fistulas. Surgery was considered the gold standard. RESULTS: MRI documented no evidence of fistula in 2 patients, intersphinteric fistulas in 5 (grade 1 and 2 St. James), trans-sphincteric fistulas in 9 (grade 3 and 4 St. James), translevator in 2 (grade 5) and complex ano-rectum-vaginal fistulas in 2. Concordance with surgery was 90%. CONCLUSIONS: MRI is an accurate technique for the identification and classification of anal and perianal fistulas and their complications. In our experience the phased-array coil offers both high field of view and spatial resolution, enabling the demonstration of perianal pathology

MR imaging in patients with Crohn disease: value of T2- versus T1-weighted gadolinium-enhanced MR sequences with use of an oral superparamagnetic contrast agent.

To prospectively compare oral contrast-enhanced T2-weighted half-Fourier rapid acquisition with relaxation enhancement (RARE) magnetic resonance (MR) imaging with T1-weighted gadolinium-enhanced fast low-angle shot (FLASH) MR and standard examinations in the evaluation of Crohn disease.Institutional review board approval and informed consent were obtained. Fifty-nine patients with Crohn disease underwent MR imaging after oral administration of a superparamagnetic contrast agent; RARE plain and fat-suppressed sequences and FLASH sequences were performed before and after intravenous injection of gadolinium chelate. References were endoscopic, small-bowel barium, computed tomographic, ultrasonographic, and clinical-biochemical scoring of disease activity. Two radiologists analyzed MR images for presence and extent of Crohn disease lesions, presence of strictures or other complications, and degree of local inflammation. MR findings were correlated with endoscopic, radiologic, and clinical data ( statistic and Spearman rank correlation test). T2-weighted MR was 95% accurate, 98% sensitive, and 78% specific for detection of ileal lesions. Agreement between T1- and T2-weighted images ranged from 0.77 for ileal lesions to 1.00 for colic lesions. T2-weighted MR enabled detection of 26 of 29 severe strictures, 17 of 24 enteroenteric fistulas, and all adhesions and abscesses; T1-weighted MR enabled detection of 20 of 29 severe strictures, 16 of 24 enteroenteric fistulas, and all adhesions and abscesses. Complications leading to surgery were found in 12 (20%) patients; these were assessed correctly with either T1- or T2-weighted images. T2-weighted signal intensities of the wall and mesentery correlated with biologic activity. Interobserver agreement was 0.642–1.00 for T2-weighted and 0.711–1.00 for T1-weighted images. T2-weighted MR can depict Crohn disease lesions and help assess mural and transmural inflammation with the same accuracy as gadolinium-enhanced T1-weighted MR. Combination of gadolinium-enhanced T1- and T2-weighted sequences is useful in the assessment of Crohn disease