Laurent Huwart

Magnetic Resonance Elastography for the Noninvasive Staging of Liver Fibrosis

BACKGROUND & AIMS The purpose of our study was to prospectively compare the success rate and diagnostic accuracy of magnetic resonance elastography, ultrasound elastography, and aspartate aminotransferase to platelets ratio index (APRI) measurements for the noninvasive staging of fibrosis in patients with chronic liver disease. METHODS We performed a prospective blind comparison of magnetic resonance elastography, ultrasound elastography, and APRI in a consecutive series of patients who underwent liver biopsy for chronic liver disease in a university-based hospital. Histopathologic staging of liver fibrosis according to the METAVIR scoring system served as the reference. RESULTS A total of 141 patients were assessed. The technical success rate of magnetic resonance elastography was higher than that of ultrasound elastography (133/141 [94%] vs 118/141 [84%]; P = .016). Magnetic and ultrasound elastography, APRI measurements, and histopathologic analysis of liver biopsy specimens were technically successful in 96 patients. The areas under the receiver operating characteristic curves of magnetic resonance elasticity (0.994 for F >or= 2; 0.985 for F >or= 3; 0.998 for F = 4) were larger (P < .05) than those of ultrasound elasticity, APRI, and the combination of ultrasound elasticity and APRI (0.837, 0.709, and 0.849 for F >or= 2; 0.906, 0.816, and 0.936 for F >or= 3; 0.930, 0.820, and 0.944 for F = 4, respectively). CONCLUSIONS Magnetic resonance elastography has a higher technical success rate than ultrasound elastography and a better diagnostic accuracy than ultrasound elastography and APRI for staging liver fibrosis.

Transvascular and interstitial transport in rat hepatocellular carcinomas: dynamic contrast-enhanced MRI assessment with low- and high-molecular weight agents.

To assess which MRI‐derived kinetic parameters reflect decreased transvascular and interstitial transport when low‐ and high‐molecular‐weight agents are used in rat hepatocellular carcinomas.

Le stercolithe est-il un signe fiable d'appendicite ?

Resume Objectif Determiner la frequence de detection des stercolithes sur appendice normal en scanner multibarrette. Materiels et methodes Un radiologue senior, n’ayant pas connaissance de l’histoire chirurgicale du patient, a examine prospectivement les scanners abdomino-pelviens de 85 patients adultes consecutifs non suspects d’appendicite. La plupart des patients ont eu une injection iodee intraveineuse. Mais aucun n’a eu d’opacification digestive. Toutes les coupes (1 et 5 mm) et les reconstructions multiplanaires etaient analysees sur une console de traitement. La position de l’appendice, son diametre externe, la presence ou non de gaz intraluminal et de stercolithe etaient notes. Resultats Parmi les 85 patients, 57 n’avaient pas ete appendicectomises. Un stercolithe etait detecte dans 13 %, l’air intraluminal dans 87 %. La position etait retrocaecale (47 %), mediocaecale (19 %) ou pelvienne (32 %). Le diametre externe moyen etait de 6,7 mm +/- 1,2 (ecart-type). Conclusion Le stercolithe a ete retrouve en tomodensitometrie multibarrette chez un nombre significatif de sujets sans appendicite aigue et ne represente pas un signe specifique d’appendicite.

MR elastographyElastographie par résonance magnétique

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.

Quelle est l’épaisseur de l’appendice normal au scanner multibarrette ?

Resume Objectif Determiner les valeurs de l’epaisseur parietale et du diametre externe de l’appendice normal au scanner multibarrette. Materiels et methodes Un radiologue senior, n’ayant pas connaissance de l’histoire chirurgicale du patient, a examine prospectivement les scanners abdomino-pelviens de 57 patients adultes consecutifs non suspects d’appendicite. La plupart des patients (50/57) ont eu une injection iodee intraveineuse. Mais aucun n’a eu d’opacification digestive. Toutes les coupes (1 et 5 mm) et les reconstructions multiplanaires etaient analysees sur une console de traitement. Le diametre externe de l’appendice, l’epaisseur des deux parois appendiculaires, et la presence ou non de gaz intraluminal etaient notes. Resultats L’appendice a ete visualise dans 82 % des cas (47/57). Le diametre externe moyen etait de 6,7 mm ± 1,2 (echelle de 5,0 a 11,0 mm). L’epaisseur moyenne des deux parois etait de 4,8 mm ± 1,0 (echelle de 2,6 a 6,4 mm). L’air intraluminal etait visualise dans 87 % des cas (41/47). Conclusion Contrairement au diametre externe, l’epaisseur biparietale de l’appendice normal en ne depassant quasiment pas le seuil de 6 mm semble une mesure fiable pour identifier un appendice normal au scanner multibarrette.

Percutaneous Facet Screw Fixation of Lumbar Spine with CT and Fluoroscopic Guidance: A Feasibility Study

PURPOSE To assess the feasibility of computed tomography (CT)- and fluoroscopy-guided percutaneous facet screw fixation following anterior lumbar interbody fusion (ALIF) or anterior pseudarthrosis in adults. MATERIALS AND METHODS Institutional review board approval and informed consent were obtained for this study. One hundred seven consecutive adult patients (46 men, 61 women; mean age ± standard deviation: 56.3 years ± 12.9) with ALIF (n = 79) or anterior pseudarthrosis (n = 28) were prospectively treated by means of percutaneous facet screw fixation with CT and fluoroscopic guidance. Two 4.0-mm cannulated screws were placed per level to fix facet joints by using either a translaminar facet or transfacet pedicle pathway. Only local anesthesia was used during these procedures. Procedural time was noted for each patient. Postoperative follow-up ranging from 1 year to 3 years was assessed by using Macnab and radiologic criteria. RESULTS The mean procedure times for a lumbar single-level and a double-level fusion ranged from 15 to 25 minutes and from 40 to 50 minutes, respectively. All the transfacet pedicle (n = 182) and translaminar facet (n = 56) screws were successfully placed in one attempt. Radiographic fusion was observed within the year following posterior fixation in all patients despite one translaminar screw failure. According to the Macnab criteria, the clinical results were classified as excellent in 92 (86%) and good in 15 (14%) of 107 patients at the time of their last follow-up examination. CONCLUSION This feasibility study showed that CT- and fluoroscopy-guided percutaneous facet screw fixation is a rapid, safe, and effective method.

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.

Vertebral split fractures: technical feasibility of percutaneous vertebroplasty.

OBJECTIVE The treatment of vertebral split fractures remains controversial, consisting of either corset or internal fixation. The aim of this study was to evaluate the technical feasibility of CT- and fluoroscopy-guided percutaneous vertebroplasty in the treatment of vertebral split fractures. MATERIALS AND METHODS Institutional review board approval and informed consent were obtained for this study. Sixty-two consecutive adult patients who had post-traumatic vertebral split fractures (A2 according to the AO classification) without neurological symptoms were prospectively treated by percutaneous vertebroplasty. All these procedures were performed by an interventional radiologist under computed tomography (CT) and fluoroscopy guidance by using only local anaesthesia. Postoperative outcome was assessed using the visual analogue scale (VAS) and Oswestry disability index (ODI) scores. RESULTS Vertebroplasty was performed on thoracic and lumbar vertebrae, creating a cement bridge between the displaced fragment and the rest of the vertebral body. Seven discal cement leakages (11%) were observed, without occurrence of adjacent vertebral compression fractures. The mean VAS measurements ± standard deviation (SD) significantly decreased from 7.9 ± 1.5 preoperatively to 3.3 ± 2.1 at 1 day, 2.2 ± 2.0 at 1 month, and 1.8 ± 1.4 at 6 months (P<0.001). The mean ODI scores ± SD had also a significant improvement: 62.3 ± 17.2 preoperatively and 15.1 ± 6.0 at the 6-month follow-up (P<0.001). CONCLUSION This study suggests that type A2 vertebral fractures could be successfully treated by CT- and fluoroscopy-guided percutaneous vertebroplasty.

Sémiologie des métastases osseuses en radiologie conventionnelle

Bone metastases are detected at initial diagnosis of cancer in 25% of cases and bone metastases are common in the course of a majority of cancer types. The spine and proximal long bones are the most affected sites. Knowledge of the basic radiological semiology is important to make the proper diagnosis of metastasis(s) bone(s), especially in situations in which the clinical context is not suggestive of metastases (such as cases where bone metastases are inaugural or cases of peripheral solitary metastasis). Tumor aggressiveness can be assessed at the level of the cortical bone and periosteum. Lodwick criteria are useful for the diagnosis of malignancy and tumor aggressiveness at initial diagnosis on plain radiographs, which are very important in the context of bone metastases. A CT scanner is required to confirm the malignancy of a bone lesion. MRI is complementary to the scanner including for the assessment of bone marrow involvement and tumor extensions.

Sémiologie des métastases osseuses en radiologie conventionnelleImaging of bone metastases

Bone metastases are detected at initial diagnosis of cancer in 25% of cases and bone metastases are common in the course of a majority of cancer types. The spine and proximal long bones are the most affected sites. Knowledge of the basic radiological semiology is important to make the proper diagnosis of metastasis(s) bone(s), especially in situations in which the clinical context is not suggestive of metastases (such as cases where bone metastases are inaugural or cases of peripheral solitary metastasis). Tumor aggressiveness can be assessed at the level of the cortical bone and periosteum. Lodwick criteria are useful for the diagnosis of malignancy and tumor aggressiveness at initial diagnosis on plain radiographs, which are very important in the context of bone metastases. A CT scanner is required to confirm the malignancy of a bone lesion. MRI is complementary to the scanner including for the assessment of bone marrow involvement and tumor extensions.