[Diffusion-weighted echo-planar sequences for the evaluation of the upper abdomen: technique optimization]. / Utilizzazione delle sequenze echo-planari pesate in diffusione per lo studio dell'addome superiore. Ottimizzazione della tecnica.

PURPOSE: To optimize the technique for the evaluation of molecular diffusion in the abdomen. MATERIAL AND METHODS: Fifteen healthy volunteers, 6 males and 9 females, ranging in age between 24 and 31 years underwent an MRI evaluation of the upper abdomen, using a superconductive 1.5T magnet (maximum gradient strength, 25 mT/m; minimum rise time 600 ms), equipped with phased array abdominal multicoil. Diffusion study was performed with a single-shot Inversion Recovery Spin-Echo Echo-planar sequence (IR-SE-EPI) with the following parameters: TR = infinite; TE=101 ms; matrix 128 yen 128; receiver bandwidth 2080 Hz/pixel; slices: n.20; slice thickness: 8 mm; acquisition time: 5.41 s. For diffusion weighting the following b values were employed: b=30 mm/s2, b=300 mm/s2 e b=500 mm/s2. Both qualitative and quantitative (calculation of linear regression analysis and of apparent diffusion coefficient) image analysis was performed. RESULTS: Image quality was graded as diagnostic in all the cases. Image quality decreased with the increase of b values: at low b values, the anatomy of upper abdominal organs was easily recognized, whereas, at high b values, the same organs could not be adequately assessed unless the images were compared with those obtained with low b values. Magnetic susceptibility artifacts were observed in all the cases; no significant chemical-shift artifacts were observed as the fat saturation pre-pulse was employed. Quantitative analysis demonstrated an apparent diffusion coefficient of 1.58 s/mm2 for the liver, 1.61 s/mm2 for the spleen and 5,14 s/mm2 for the gallbladder. A statistically significant difference (p<0.001) was observed between parenchymatous organs (liver and spleen) and gallbladder, presenting as a stationary fluid. CONCLUSIONS: Diffusion-weighted MR sequences may be implemented for abdominal studies, but the optimization of same parameters is slightly different compared with neuroradiologic applications. The potential applications are interesting above all as regards the characterization of focal liver lesions. Further developments are awaited in both sequence optimization (greater stability and lower sensitivity to magnetic susceptibility artifacts) and data analysis, with more complex algorithms able to better quantify the real diffusion coefficient.

Role of MR venography in the evaluation of deep venous thrombosis.

PURPOSE: MR venography has been recommended for the evaluation of deep venous thrombosis. The purpose of our study was to determine the role of MR venography, in particular at the level of the pelvis where other diagnostic modalities show major limitations. MATERIALS AND METHODS: Forty-three patients with clinical suspicion of deep venous thrombosis were examined by means of pelvic MR venography. In all cases, a 2D-TOF sequence was used with cranial arterial presaturation. In selected cases, i.e. when a small intraluminal filling defect was present, a cine-PC sequence was used in addition in order to exclude the presence of a pulsatility artifact as causing the filling defect. In all cases, contrast venography was also performed and considered to be the standard of reference. RESULTS: MR venography showed 26 patients to be positive for deep venous thrombosis at the pelvic level. These positive results were correct in 25 cases. The analysis of the results provided values of sensitivity and specificity of respectively 100% and 94%, with an overall accuracy of 97.6%. CONCLUSIONS: Our results indicate that MR can provide highly accurate images, similar to those of contrast venography, in a noninvasive fashion. It is particularly useful in the pelvic region where the limitations of other imaging modalities are more evident.

[Usefulness of the new sequences of magnetic resonance in the study of hepatic hydatidosis]. / Utilità delle nuove sequenze di Risonanza Magnetica nello studio della idatidosi epatica.

We investigated the role of new MR Imaging techniques for the diagnosis, characterization and staging of hepatic hydatid disease. We examined 21 patients (30 hydatid cysts), 7 men and 14 women, ranging in age 26 to 74 years, with known hydatid disease. MR examinations were carried out on a 0.5T superconductive magnet (Philips Gyroscan T5, Philips Medical System) with the following imaging protocol: T1w (TR/TE/NEX: 300/10/4) SE, T2w (TR/TE/NEX: 3000/120/6) TSE and fat suppressed (SPIR technique) T2w (TR/TE/NEX: 3000/120/6) sequences. MR Angiography examinations were performed with 2D Time of Flight sequences (TR = 33 ms; TE = 6.9 ms; flip angle = 60 degrees; slice thickness = 4.0 mm with 2.0 mm overlapping; matrix = 256 x 256; number of slices = 45-50; acquisition time = 4 min 19 s), while MR cholangiography was performed with 3D, fat suppressed (SPIR) Turbo Spin-echo (TSE) sequences (TR = 3000 ms, TE = 700 ms, ETL = 12, acq. time = 5 min 48 s). MRI correctly detected all the hydatid cysts on both T1- and T2-weighted images. Characterization was correct in all the cysts larger than 3 cm, where typical signs consistent with hydatid disease were detected. MRA images always showed the inferior vena cava and the splenoportal system. The portal vessels were demonstrated only up to the first branches. In 3 cases an extrinsic compression of the inferior vena cava was diagnosed. MRC, performed in 7 cases, showed normal main bile duct caliber in 6 cases, while in another case, where a cyst ruptured inside the bile ducts, the communication between the cyst and the bile ducts was clearly demonstrated. In conclusion, MR Imaging is a valuable tool in the study of liver hydatid disease. Moreover, the availability of such new MR techniques as MRC and MRA, greatly improves the diagnostic role of MR imaging, especially when studying complications and before surgery.

[Quantification of mesenteric flow with magnetic resonance imaging before and after a meal: results in healthy volunteers]. / Quantificazione del flusso mesenterico con Risonanza Magnetica prima e dopo pasto: risultati nei volontari sani.

Several literature studies showed that total intestinal blood flow approximates superior mesenteric vein flow. Today, new accurate techniques can be used to measure blood flow. We investigated MR capabilities in measuring mesenteric vein flow, to assess total intestinal blood flow. Nine healthy volunteers were examined before and after a meal with a phase-contrast technique to measure blood flow. Flow speed and quantity can be measured positioning a ROI inside the vessel for speed evaluation and around the vessel for flow quantitation. Superior mesenteric blood flow exhibited a three-fold increase after a meal relative to pre-meal values. Cine phase-contrast MRI was a useful tool to measure mesenteric flow in healthy volunteers both before and after a meal and can therefore be suggested for the noninvasive examination of patients with a suspected chronic mesenteric blood supply deficiency.