Simultaneous MR quantification of hepatic fat content, fatty acid composition, transverse relaxation time and magnetic susceptibility for the diagnosis of non-alcoholic steatohepatitis.

Non-alcoholic steatohepatitis (NASH) is characterized at histology by steatosis, hepatocyte ballooning and inflammatory infiltrates, with or without fibrosis. Although diamagnetic material in fibrosis and inflammation can be detected with quantitative susceptibility imaging, fatty acid composition changes in NASH relative to simple steatosis have also been reported. Therefore, our aim was to develop a single magnetic resonance (MR) acquisition and post-processing scheme for the diagnosis of steatohepatitis by the simultaneous quantification of hepatic fat content, fatty acid composition, T2 * transverse relaxation time and magnetic susceptibility in patients with non-alcoholic fatty liver disease. MR acquisition was performed at 3.0 T using a three-dimensional, multi-echo, spoiled gradient echo sequence. Phase images were unwrapped to compute the B0 field inhomogeneity (ΔB0 ) map. The ΔB0 -demodulated real part images were used for fat-water separation, T2 * and fatty acid composition quantification. The external and internal fields were separated with the projection onto dipole field method. Susceptibility maps were obtained after dipole inversion from the internal field map with single-orientation Bayesian regularization including spatial priors. Method validation was performed in 32 patients with biopsy-proven, non-alcoholic fatty liver disease from which 12 had simple steatosis and 20 NASH. Liver fat fraction and T2 * did not change significantly between patients with simple steatosis and NASH. In contrast, the saturated fatty acid fraction increased in patients with NASH relative to patients with simple steatosis (48 ± 2% versus 44 ± 4%; p < 0.05) and the magnetic susceptibility decreased (-0.30 ± 0.27 ppm versus 0.10 ± 0.14 ppm; p < 0.001). The area under the receiver operating characteristic curve for magnetic susceptibility as NASH marker was 0.91 (95% CI: 0.79-1.0). Simultaneous MR quantification of fat content, fatty acid composition, T2 * and magnetic susceptibility is feasible in the liver. Our preliminary results suggest that quantitative susceptibility imaging has a high diagnostic performance for the diagnosis of NASH.

[Diffusion-weighted MR imaging of the liver]. / Imagerie de diffusion hépatique.

Diffusion-weighted imaging studies the motion of water molecules within a given tissue. Initially used for neuroradiological applications, it is now routinely used for abdominal imaging, especially liver imaging. The diffusion pulse sequence is a T2 echo-planar sequence where diffusion gradients are applied. In this article, we will review the sequence itself and the parameters used to optimize the sequence, quantitative and qualitative image evaluation, and the main applications for liver imaging: characterization of focal lesions, detection of focal lesions, evaluation of response to therapy and quantification of liver fibrosis.

MR elastography.

Magnetic resonance (MR) elastography is an emerging method for measuring the viscoelastic properties of tissues. Hepatic fibrosis, which increases the elasticity or stiffness of the liver, can be detected and staged by MR elastography. The technique has several advantages compared with transient ultrasound elastography (FibroScan): it can evaluate much larger liver volumes; it can be performed in obese patients and in those with ascites; and it can assess the full three-dimensional displacement vector, allowing a more precise analysis of viscoelastic parameters. These technical advantages mean that MR elastography is more accurate forstaging liver fibrosis than is transient ultrasound elastography. Moreover, it has been shown in animal studies using MR elastography that parameters other than fibrosis can also increase liver elasticity, including inflammation and myofibroblast activation before extracellular matrix deposition. Because of its greater accuracy-but also its higher cost-MR elastography will probably have a complementary role alongside ultrasound elastography. Nevertheless, this role should be further studied, especially in terms of response to treatment and the early detection of chronic liver diseases such as steatohepatitis.

[Magnetic resonance imaging of angiogenesis in tumors]. / Imagerie par résonance magnétique de l'angiogenèse tumorale.

Tumor angiogenesis induces the proliferation of immature blood vessels that are both heterogeneous and leaky. These characteristics can be demonstrated by measuring the perfusion parameters with MRI. Perfusion MRI is usually performed with in T1-weighted dynamic imaging after bolus injection of an exogenous contrast agent such as gadolinium chelate. The perfusion parameters are obtained by semi-quantitative or quantitative analysis of the enhancement curves in the tumor and the arterial input. Perfusion can also be assessed without injecting a contrast agent using arterial spin labeling techniques, diffusion MRI, or BOLD (blood oxygen level dependent) MRI. However, these latter methods are limited by a low signal-to-noise ratio and problems with quantification. The main indication for perfusion MRI is the assessment of antiangiogenic and antivascular treatments. New possibilities for demonstrating angiogenic blood vessels are being opened by molecular imaging.

Pancreaticopleural fistula: diagnosis with magnetic resonance pancreatography.

Pancreaticopleural fistula secondary to chronic pancreatitis is a rare cause of recurrent pleural effusion. The demonstration of the fistula with endoscopic retrograde pancreatography and CT is invasive or limited. We report in two patients the use of magnetic resonance pancreatography as a noninvasive alternative to endoscopic retrograde pancreatography for the diagnosis of pancreaticopleural fistula.

Comparison of gadolinium-DTPA and polylysine-gadolinium-DTPA--enhanced magnetic resonance imaging of hepatocarcinoma in the rat.

RATIONALE AND OBJECTIVES: To compare the magnetic resonance (MR) imaging characteristics of gadolinium-DTPA (Gd-DTPA), a low-molecular-weight contrast agent, and polylysine-Gd-DTPA, a macromolecular contrast agent, in two types of hepatocarcinomas (HCC) in the rat. METHODS: T1-weighted spin-echo images were obtained in 13 rats with chemically induced HCC and 26 rats with Novikoff HCC before and 3 minutes to 60 hours after administration of either Gd-DTPA or polylysine-Gd-DTPA. RESULTS: Three minutes after polylysine-Gd-DTPA administration, the tumor-to-liver contrast of the two types of HCC increased significantly (positive contrast for chemically induced HCC and negative contrast for Novikoff HCC). At 30 minutes and 60 hours, the tumor-to-liver contrast remained above baseline values in chemically induced HCC and returned progressively to baseline values in Novikoff HCC. No significant increase in tumor-to-liver contrast was observed after Gd-DTPA administration. CONCLUSIONS: These results suggest that polylysine-Gd-DTPA provides a higher and more prolonged increase in tumor-to-liver contrast than Gd-DTPA.

Comparison of unenhanced and gadoxetate disodium-enhanced spin-echo magnetic resonance imaging for the detection of experimental hepatocellular carcinoma in the rat.

RATIONALE AND OBJECTIVES: The authors compare the potential value of unenhanced and gadoxetate disodium-enhanced spin-echo images for the detection of hepatocellular carcinoma in a rat model. METHODS: Eleven rats with chemically induced hepatocellular carcinoma underwent unenhanced T2-weighted fast spin-echo imaging followed by T1-weighted spin-echo imaging before and at 5 minutes, 30 minutes, 3 hours, 1 day, and 3 days after intravenous administration of 60 micromol/kg gadoxetate disodium at 4.7 tesla. Tumor and liver enhancement, and tumor-to-liver contrast-to-noise (C/N) ratio were calculated. RESULTS: After gadoxetate disodium administration, the tumors showed less enhancement than the liver. Tumor-to-liver C/N ratio increased from 5.5 +/- 0.8% on unenhanced T1-weighted images to 12.9 +/- 2.4% on gadoxetate-enhanced T1-weighted images (P = 0.02). However, the C/N ratio on unenhanced T2-weighted images (23.5 +/- 3.6%) remained higher than that on gadoxetate-enhanced T1-weighted images, a difference that is statistically significant (P < 0.01). CONCLUSIONS: In the experimental setting of our study, the higher tumor-to-liver C/N ratio on unenhanced T2-weighted spin-echo images suggests that unenhanced T2-weighted spin-echo images are superior to gadoxetate disodium-enhanced T1-weighted spin-echo images for the detection of hepatocellular carcinoma.

Laparoscopic splenectomy in adults and children: experience with 31 patients.

BACKGROUND: Open surgery is the standard approach for splenectomy in hematologic disorders, but a few cases of successful laparoscopic splenectomy have been reported. METHODS: Thirty-one patients (18 adults, group 1; and 13 children, group 2) underwent laparoscopic splenectomy. Indications for surgery included idiopathic thrombocytopenic purpura (25 patients), congenital spherocytosis (4 patients), and hemolytic anemia (2 patients). In 97% of the patients the diameter of the spleen was less than 15 cm. RESULTS: Laparoscopic splenectomy was successful in 94% of the patients; conversion to open surgery was mainly related to hemorrhage. Accessory spleen was found in 39% in group 1 and 8% in group 2. Two adults received intraoperative autotransfusion. Postoperative morbidity was minimal. The median postoperative stay was 3 days (range, 2 to 12 days) in group 1 and 2 days (range, 2 to 5 days) in group 2. CONCLUSIONS: Laparoscopic splenectomy is safe in both adults and children. Adequate selection of patients (small-size spleen, splenic destruction on preoperative scanning of platelets), appropriate preparation in patients with idiopathic thrombocytopenic purpura (immunoglobulin G), and meticulous surgical technique (with routine opening of the gastrocolic ligament to search for accessory spleen) are key factors in obtaining the same long-term results as with open surgery.

MRI of the anal canal: correlation with histologic examination.

The purpose of this study was to correlate the MRI features of the anal canal with histologic findings. T1- and T2-weighted MR images of nine anal canals were obtained after fixation in 10% formalin. In three specimens, imaging was repeated after removal of histologic layers with a dissecting microscope. Corresponding histologic slices were stained with hematoxylin-eosin, Masson trichrome, and periodic acid-Schiff. Four layers were visualized on T2-weighted images. An inner layer of high signal intensity and a second layer of low signal intensity corresponded to the mucosa as well as mucous secretions and to the submucosa. The high signal intensity layer vanished at the distal part of the anal canal in accordance with the lack of mucus-secreting epithelium below the level of the dentate line. A third layer of intermediate signal intensity corresponded to the internal sphincter. A fourth layer of low signal intensity corresponded to the longitudinal muscle and external sphincter. T2-weighted MRI is capable of showing the internal architecture of the wall of the anal canal. In particular, the internal sphincter can be differentiated from the external sphincter and longitudinal muscle.

The surgical management of congenital liver cysts.

BACKGROUND: Most series that report the results of surgical treatment for congenital liver cysts focus more on the technical aspects of the operation than on the late outcome of these patients. In this paper, we emphasize the importance of appropriate patient selection and adequate surgical technique for successful long-term outcome. METHODS: Twenty-four consecutive patients with congenital liver cysts were selected for surgical treatment. According to our own classification, 13 patients had simple liver cysts, nine had multicystic liver disease, and two had type I polycystic liver disease. All of these patients were treated by the fenestration technique. An open approach was used for five patients (group 1) treated between 1984 and 1990. In 19 patients (group 2) treated since 1991, a laparoscopic approach was used. The incidence of complicated liver cysts was 40% in group 1 and 68% in group 2. RESULTS: There were no treatment-related deaths in this series. The mean postoperative hospital stay was significantly shorter for patients who underwent successful laparoscopic fenestration (p < 0.05). In the open group (group 1), there were no postoperative complications, and all patients were alive and free of symptoms during a mean follow-up of 130 months, without any sign of cyst recurrence. In the laparoscopic group (group 2), four patients were converted to open surgery. One of these patients had an inaccessible posterior cyst; another had bile within the cystic cavity. A further two cases had complicated liver cysts with an uncertain diagnosis between congenital and neoplastic cysts. Four patients (21%) developed peri- or postoperative complications. During a mean follow-up time of 38.5 months, none of the patients with simple liver cysts incurred late symptoms or signs of cyst recurrence. In the six patients with multicystic liver disease, one developed disease-related cyst progression (17%) and required reoperation. One of the two patients with type I polycystic liver disease (50%) developed asymptomatic disease-related cyst progression. CONCLUSIONS: When patients are carefully selected and a proper surgical technique is employed, excellent long-term results with a low morbidity rate can be achieved in patients with congenital liver cysts. Patients with multicystic liver disease or type I polycystic liver disease are more prone to late cyst recurrence. A tailored approach is thus indicated for patients with congenital liver cystic disease. However, the laparoscopic approach appears to be the gold standard for the treatment of highly symptomatic or complicated simple liver cysts.

Detection of reperfused ischemia of the rat intestine: value of magnetic resonance imaging with small-molecular-weight dysprosium and gadolinium chelates.

RATIONALE AND OBJECTIVES: The authors assessed whether the small-molecular-weight magnetic resonance (MR) imaging contrast agents dysprosium diethylenetriamepentaacetic acid bismethylamide (sprodiamide injection), which enhances T2*, and gadolinium diethylenetriamepentaacetic acid bismethylamide (gadodiamide injection), which enhances T1, could improve the detection of reperfused ischemia of the rat intestine. METHODS: Eighteen rats were subjected to vascular occlusion of the distal ileum for 30 minutes, followed by reperfusion. Ten minutes after reperfusion, T1- and T2-weighted spin-echo (SE) images were obtained before and after administration of sprodiamide, gadodiamide, or both. The same imaging protocol was applied in another group of 18 rats subjected to 10 minutes of occlusion and reperfusion. Histologic examination of the intestine was performed after MR imaging. RESULTS: Villous injury (ie, denudation) was observed in most cases after 30 minutes of occlusion, but not after 10 minutes of occlusion. After 30 minutes of occlusion, the superficial part of the ischemic intestine was hyperintense to the normal intestine on unenhanced T2-weighted images. Administration of sprodiamide improved the contrast between the normal and ischemic intestine on T2-weighted images, and administration of both gadodiamide and sprodiamide improved the contrast on T1- and T2-weighted images. After 10 minutes of occlusion, no contrast was discernible before or after contrast material administration. CONCLUSION: These results suggest that the detection of reperfused intestinal ischemia of sufficient duration to cause villous injury can be improved by using sprodiamide injection alone or in combination with gadodiamide.

Oral magnetic particles (ferristene) as a contrast medium in abdominal magnetic resonance imaging.

RATIONALE AND OBJECTIVES: In this phase III study, we evaluated the efficacy and safety of a negative contrast medium, ferristene (oral magnetic particles), among 277 patients undergoing magnetic resonance (MR) imaging of the abdomen. METHODS: Enhanced (800 ml ferristene) MR images were compared with unenhanced MR images in an intraindividual-patient control design. Adverse events were recorded. The examinations were performed on 1.5-T MR systems (T1- and T2-weighted sequences). RESULTS: Ferristene increased the diagnostic information in 50.9% of the patients, particularly in those with abdominal masses, lymphoma, or pancreatic disease. Distribution of ferristene in the stomach, duodenum, jejunum, and ileum was complete or sufficient in 70.5-85% of the studies. In 64% of the patients, we were confident in the MR findings after the use of ferristene, and ferristene disclosed additional findings in 22% of the patients. The incidence of adverse events was 9.0%, but only 3.6% of all patients experienced ferristene-related adverse events (e.g., nausea, vomiting). Most events were mild or moderate in intensity. CONCLUSION: Ferristene was well tolerated, and for 50% of the patients it added useful diagnostic information.

Focal bowel wall changes detected with colour Doppler ultrasound: diagnostic value in acute non-diverticular diseases of the colon.

We performed a study to determine if colour Doppler findings may help to identify the cause of wall thickening in acute non-diverticular diseases of the colon. The study group included 66 patients admitted to the emergency department with a final diagnosis of infectious colitis (n=23), inflammatory colitis (n=10), ischaemic colitis (n=23) and malignant tumours (n=10). The following ultrasound features were assessed: maximal wall thickness, wall stratification, arterial flow in the colonic wall and arteriolar resistive index. Higher values of wall thickness were observed in malignant tumour (18.2+/-6.2 mm, p<0.001). Moderately thickened wall (6.6+/-1.3 mm, p< or =0.06), preserved stratification (90% versus 46% in the remainder of the study population) and lower resistive index (0.51+/-0.10, p< or =0.05) were significantly related to inflammatory colitis. Absence of arterial flow was more frequently observed in ischaemia (43% versus 12% in the remainder of the study population). In conclusion, despite some overlap, both ultrasound and colour Doppler features are helpful in the differential diagnosis of colonic thickening related to non-diverticular colonic lesions.

Early diagnosis of acute intestinal ischaemia: contribution of colour Doppler sonography.

The aim of this study was to evaluate the contribution of colour Doppler sonography in the diagnosis of acute intestinal ischaemia. In a two years experience, all patients admitted for acute abdominal pain in our emergency department were evaluated with colour Doppler sonography of the abdomen. The final diagnosis based on clinical evolution, endoscopic or surgical findings and further radiological investigations was compared to the sonographic results. Therapy and final outcome of the patients with acute intestinal ischaemia were also evaluated. In twenty-one patients a final diagnosis of acute intestinal ischaemia (mesenteric ischaemia (n = 13) and ischaemic colitis (n = 8)) was made. Intestinal ischaemia was correctly diagnosed by initial clinical and biological data and further confirmed by sonography in eight cases (mesenteric ischaemia (n = 2) and ischaemic colitis (n = 6)). Eleven other cases were detected by suggestive colour Doppler sonography features (mesenteric ischaemic (n = 10) and ischaemic colitis (n = 1)). Sixteen of the 21 patients had a final favourable outcome (mesenteric ischaemia (10/ 13) and ischaemic colitis (6/8)). We conclude that sonography has a place in the diagnosis of acute intestinal ischaemia and has to be integrated in the diagnostic algorithm of this acute condition. By this way, this diagnosis may be suspected earlier and may allow a prompt and adapted treatment with possible improvement in survival rate.

[Iron oxides as contrast agents for MRI of the liver]. / Les oxydes de fer comme agents de contraste en IRM hépatique.

Iron oxide particles are a potent class of MR contrast agents. Depending on their size and formulation, iron oxides are selectively taken up by the reticuloendothelial system or the hepatocytes. Experimental and clinical studies have shown that iron oxides can improve the detection and the characterization of liver tumors and can contribute to the detection of diffuse liver lesions. These tissue-specific MR contrast agents combine anatomic and functional information about liver lesions.

[Imaging of intestinal ischemia]. / Imagerie des ischémies intestinales.

Ischemic bowel disease includes acute and chronic mesenteric ischemia, and colon ischemia. Cross-sectional imaging, and more particularly computed tomography, has an increasing role in the detection of acute and chronic mesenteric ischemia. Vascular obstructions or stenoses and changes in the bowel wall can be observed. Functional information can be added with MRI by using sequences that are sensitive to oxygen saturation in the superior mesenteric vein. Arteriography remains the reference examination in patients with acute mesenteric ischemia.

[Cardiac imaging by means of four-detector row computed tomography and cardiac gating]. / Imagerie cardiaque en tomodensitométrie à quatre canaux d'acquisition et synchronisation cardiaque.

Electrocardiographically-assisted imaging is a recent development in multislice spiral computed tomography. In this article, we summarize the principles of four-detector row CT for cardiac applications. Following is an overview of the potential of this technique to evaluate the heart, the thoracic aorta, and the paracardiac pulmonary parenchyma. Technical considerations for optimal imaging are highlighted.

[Follow-up of TIPS: evaluation of signs of dysfunction with Doppler ultrasonography]. / Suivi des TIPS: evaluation des signes de dysfonctionnement en echographie doppler.

PURPOSE: to assess the signs of TIPS dysfunction at Doppler sonography. MATERIALS AND METHODS: retrospective study of signs observed in 106 TIPS including 31 TIPS with dysfunction (portoauricular pressure gradient > 12 mmHg). RESULTS: the signs of TIPS dysfunction were a decrease in the mean velocity in the TIPS (for a velocity < 40 cm/sec, 90% sensitivity, 96%), a hepatopetal intrahepatic portal flow (on the right 90% sensitivity, 100% specificity, on the left 95% sensitivity, 92% specificity), a lack of cardiac modulation of the signal in the TIPS (93% sensitivity, 65% specificity), a hepatic vein flow reversal (30% sensitivity, 100% specificity), and, the only direct sign of stenosis, an increase of the mean velocity in the stenosis (42% sensitivity, 95% specificity for a velocity > or = 1 m/sec). CONCLUSION: the most sensitive Doppler signs of tips dysfunction are the indirect signs of stenosis.

[Value of echography in the diagnosis of acute intestinal occlusion]. / Intérêt de l'échographie dans le diagnostic de l'occlusion intestinale aiguë.

OBJECTIVE: The aim of our study was to assess the value of sonography in the diagnosis of acute intestinal occlusion. MATERIAL AND METHODS: Sonographic findings were reviewed in 50 cases of intestinal occlusion (39 small bowel and 11 colonic occlusions). The final diagnosis was based on surgical findings (n = 40) or clinical course and further imaging findings (n = 10). RESULTS: Occlusion was correctly detected with sonography in 48 cases (96%). The location was correctly established with sonography in 43 cases (86%). The precise cause was suggested with sonography in 21 cases (42%). COMMENTARY: These results confirm the value of sonography for the diagnosis of intestinal occlusion and the identification of its level and its cause.

[Spiral CT of the bile ducts]. / La TDM spiralée des voies biliaires.

The multiplanar capability of spiral CT improves the evaluation of bile duct lesions. In particular, spiral CT after intravenous administration of a cholangiographic agent (spiral CT cholangiography) provides adequate 2D and 3D images of the bile ducts in patients with normal bilirubin levels. Spiral CT cholangiography may be particularly useful as a noninvasive imaging method to detect biliary anatomic variations and bile duct stones before or after laparoscopic cholecystectomy. This technique does not replace retrograde cholangiography which has therapeutic applications, but might help to select patients who need to undergo invasive procedures such as retrograde cholangiography.