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Christophe Aubé

Publications and source records attributed to Christophe Aubé.

13 recordsLinked to original sources
PubMed2006

MR-guided radiofrequency ablation: do magnetic fields influence extent of coagulation in ex vivo bovine livers?

PURPOSE: To prospectively determine if static magnetic fields of magnetic resonance (MR) imagers affect radiofrequency (RF) ablation coagulation volume and shape. MATERIALS AND METHODS: Ex vivo RF ablations of bovine livers were performed with magnetic field strengths of 0.2, 1.5, and 3.0 T and were compared with ablations performed outside the magnetic field in a control group. Two MR-compatible monopolar RF devices (internally cooled single and cluster electrodes) were systematically tested. Length of long axis (y-axis), length of two short axes (x- and z-axes), and coagulation volume and shape measured outside and inside different magnetic fields were compared with the Dunnett test. Significance level was set to .05. RESULTS: For the single electrode, no significant difference was observed between length of short axes and coagulation volume and shape measured inside and outside the magnetic field. Mean x- and z-axis lengths were 2.3 and 2.6 cm, respectively, outside the magnetic field; 2.4 and 2.4 cm, respectively, at 0.2 T; 2.5 and 2.6 cm, respectively, at 1.5 T; and 2.2 and 2.5 cm, respectively, at 3.0 T. Differences between length of long axis, length of short axis perpendicular to static magnetic field, and coagulation volume and shape achieved with the cluster electrode inside and outside the magnetic field were not significant. Mean x- and z-axis lengths were 3.9 and 3.9 cm, respectively, outside the magnetic field; 3.7 and 3.8 cm, respectively, at 0.2 T; 4.0 and 4.3 cm, respectively, at 1.5 T; and 3.8 and 3.8 cm, respectively, at 3.0 T. Differences between ablations performed at 1.5 T and those performed in the control group with the cluster electrode were significant (P = .026). In this case, a difference of 4 mm in the length of the short axis parallel to the magnetic field was detected, but there was no significant difference in coagulation volume. CONCLUSION: No significant differences in coagulation volume and shape could be recorded between RF ablations performed outside and those performed inside the static magnetic field.

Animals↗
PubMed2006

Percutaneous MR-guided radiofrequency ablation of recurrent sacrococcygeal chordomas.

OBJECTIVE: Radiofrequency ablation is emerging as a therapeutic technique for the treatment of an increasing variety of tumors. Exact visual guidance to the tumor and controlled delivery of energy is pivotal for ablation success. CONCLUSION: Introducing MRI as a guidance technique ideally uses tumor-specific tissue characteristics, allows direct multiplanar reconstruction for precise needle positioning, and permits real-time monitoring and assessment of treatment-induced tissue signal changes to increase the safety of the procedure.

Aged↗
PubMed2005

MR cholangiopancreatography versus endoscopic sonography in suspected common bile duct lithiasis: a prospective, comparative study.

OBJECTIVE: Our purpose was to compare the accuracy of MR cholangiopancreatography and endoscopic sonography for the diagnosis of common bile duct stones in patients with a mild to moderate clinical suspicion of common bile duct stones. SUBJECTS AND METHODS: Forty-seven patients were prospectively enrolled. Inclusion criteria included acute pancreatitis, subclinical jaundice, and clinical features of common bile duct stone migration. Radial endoscopic sonography and MR cholangiopancreatography with the single-shot fast spin-echo technique were performed a maximum of 48 hr apart. The gold-standard diagnosis was obtained with ERCP (n = 20) or intraoperative cholangiography (n = 14) if the results of endoscopic sonography or MR cholangiopancreatography were abnormal or if a cholecystectomy was performed, or by clinical and biochemical follow-up (n = 11) if the results of endoscopic sonography and MR cholangiopancreatography were normal. RESULTS: The final diagnosis was common bile duct stones in 16 patients, malignant obstructions in four, and another biliary disease in two (lithiasis migration aspect with papillary edema); 23 patients had no biliary disease. The sensitivity and specificity of MR cholangiopancreatography were, respectively, 90.5% and 87.5% for etiologic diagnosis and 87.5% and 96.6% for the detection of common bile duct stones. The corresponding values for endoscopic sonography were 86.4% and 91.3% for etiologic diagnosis and 93.8% and 96.6% for visualization of choledocholithiasis. Accuracy did not significantly differ between the techniques. CONCLUSION: In cases of mild to moderate suspicion of choledocholithiasis, the accuracies of endoscopic sonography and MR cholangiopancreatography are similar. Because MR cholangiopancreatography is noninvasive, it may be preferred for this indication.

Adult↗
PubMed2004

New Doppler ultrasound signs improve the non-invasive diagnosis of cirrhosis or severe liver fibrosis.

OBJECTIVES: To determine whether ultrasound and, particularly, new Doppler signs increased the diagnostic accuracy of the most accurate, currently available markers for the diagnosis of cirrhosis or severe fibrosis. METHODS: Thirty-two clinical (n = 4), biochemical (n = 11) and Doppler ultrasound (n = 17) variables were recorded in 106 patients with compensated chronic liver disease. Diagnostic accuracy was evaluated by discriminant analysis; first, globally, using all variables then by stepwise analysis. RESULTS: (A) Diagnosis of cirrhosis. Using Doppler ultrasound, diagnostic accuracy was 92% (95% confidence interval 81-98) globally, and 89% (76-95) with three variables (spleen length, hepatic vein spectrum and maximum portal vein velocity). Based upon clinical signs, diagnostic accuracy was 86% (77-92) globally, and 85% (76-91) with one variable (firm liver). Based upon biochemical parameters, diagnostic accuracy was 80% (70-88) globally, and 81% (72-88) with two variables (hyaluronate and platelet count). Based upon all parameters, diagnostic accuracy was 91% (79-96.5) globally, and 91% (79-96.5) with four variables (firm liver, hyaluronate, platelet and hepatic vein spectrum). On an intention to diagnose basis, Doppler ultrasound provided a lower independent contribution due to missing data. (B) In the diagnosis of severe fibrosis, diagnostic accuracy was 83% (69-92) globally, and 77% (62-87) with one variable. CONCLUSIONS: Cirrhosis can be correctly diagnosed in approximately 90% of patients with compensated chronic liver disease using a few Doppler ultrasound signs including a new sign, the hepatic vein spectrum. Doppler ultrasound could be used for the first line diagnosis and biochemical markers, such as hyaluronate, in patients with missing Doppler ultrasound data.

Adult↗
PubMed2004

Magnetic resonance imaging characteristics of six radiofrequency electrodes in a phantom study.

PURPOSE: To evaluate and compare visibility and artifacts in magnetic resonance (MR) compatible radiofrequency (RF) electrodes for MR-guided RF ablation. MATERIAL AND METHODS: Six different MR compatible electrodes for RF ablation including two internally cooled single needles, one internally cooled cluster needle, two expandable needles and one perfused needle were tested in a phantom study at 0.2 Tesla and at 1.5 Tesla field strength. Fluoroscopic, T1- and T2-weighted fast spin echo (FSE) and gradient echo (GE) sequences, which are usually used for MR-guided interventions, were evaluated. Qualitative and quantitative evaluations were performed. Length, width, noise, tip artifacts, global artifacts and global visualization of the RF electrodes that showed all sequences at different angles. RESULTS: Qualitative analysis showed that electrodes were well visualized at all angles and sequences and on both MR imagers. Quantitative analysis showed that artifact-induced widening of the shaft was increased in all electrodes by: a). use of fluoroscopic sequences, GE sequences, and fat saturation, b). increasing the angle between the needle and main magnetic field, and c). high field strength (1.5 T). Expandable needles produced fewer tip artifacts but broader signal voids along the shaft compared to nonexpandable needles. Cluster electrodes produced less widening than the other electrodes. CONCLUSION: Visibility and artifacts in all six MR compatible RF electrodes are satisfactory and these electrodes could be used for MR-guided radiofrequency ablation procedures.

Artifacts↗
PubMed2003

Inter-observer and intra-observer variability in hepatology.

OBJECTIVES: A determination of the inter-observer variability is an important step before determining diagnostic accuracy and requires a specific methodology and statistical tests. The aim of this study was to report the results, characteristics and methodological quality of agreement studies performed in hepatology. METHODS: A search of published studies yielded 42 that could be used in this evaluation: three were clinical studies, 11 were in the field of endoscopy, 12 in histopathology and 16 in radiology. The studies were described with a grid of 28 items and evaluated with a quality score (QUAS; maximum, 35) including 22 items. RESULTS: The following agreement level was noted: intra-observer > inter-observer > inter-centre. The following signs had good agreement. Endoscopy: size and red signs of oesophageal varices; histopathology: cirrhosis, fibrosis and steatosis; Doppler: mean portal vein and superior mesenteric artery velocities, hepatic artery area and perfusion indexes. Frequent methodological weaknesses were noted. The real agreement (such as the kappa index excluding chance), and the prevalence of signs and biases were rarely assessed. Standardized observations (67% of the studies), blind assessment (48%), simultaneous observations (7%), and the recording technique were not frequently used. The mean QUAS was 13 +/- 6 with 17 +/- 4 in histopathology versus 11 +/- 6 in radiology (P < 0.05). Using multiple regression, four variables independently predicted the QUAS with R2 = 0.77: adapted tests, multiple observations, intra-class correlation coefficient and agreement proportion. CONCLUSIONS: Methodology was often insufficient. Agreement is often measured under biased conditions. Some areas were not or were rarely studied, e.g., biology and ultrasound. The agreement and QUAS were often poor, suggesting the need for studies with improved observation and methodological quality of agreement.

Esophageal and Gastric Varices↗
PubMed2003

In vivo efficiency of four commercial monopolar radiofrequency ablation systems: a comparative experimental study in pig liver.

RATIONALE AND OBJECTIVES: To evaluate the efficiency of 4 radiofrequency (RF) systems by assessing the amount of delivered energy for each thermal induced lesion after perfusion mediated RF ablation and to compare the influence of perfusion mediation types on the energy efficiency. METHODS: A total of 43 ablations in 16 male landrace pigs with 4 RF devices were performed strictly according to the manufacturers' instructions. Total absorbed energy was computed and then related to 3D volumetry obtained after histopathological evaluation. Sixteen ablations were performed under physiological liver perfusion and 27 ablations with occlusion of portal vein, hepatic artery, or both vessels. Energy efficiency values of the RF systems for different vascular occlusion techniques were compared and analyzed by a nonparametrical rank sum test. RESULTS: Under physiological perfusion, the average energy delivered to produce 1-cm3 lesion size was calculated to 1650 +/- 929, 3097 +/- 389, 8312 +/- 2068, and 5493 +/- 2306 Watt x s/cm3 for the Berchtold, Radionics, Radiotherapeutics, and RITA system, respectively. After perfusion-mediated RF ablation, artery occlusion was not as effective as portal vein occlusion, which reduced the energy to 587 +/- 148, 869 +/- 276, and 903 +/- 394 Watt. s/cm3 for the Berchtold, Radionics, and Radiotherapeutics system, respectively. The occlusion of vessels, portal vein, and artery or portal vein alone increased the energy efficiency compared with physiological liver perfusion or occlusion of the artery (P = 0,003). CONCLUSIONS: Under physiological liver perfusion the open perfused system and the internally cooled system provided the best efficiency values with lowest standard deviations. The energy efficiency was increased markedly for all systems after occlusion of the portal vein either alone or in combination with arterial occlusion. Occlusion of the hepatic artery did not improve the efficiency.

Animals↗
PubMedDate not supplied

Influence of NaCl concentrations on coagulation, temperature, and electrical conductivity using a perfusion radiofrequency ablation system: an ex vivo experimental study.

PURPOSE: To determine, by means of an ex vivo study, the effect of different NaCl concentrations on the extent of coagulation obtained during radiofrequency (RF) ablation performed using a digitally controlled perfusion device. METHOD: Twenty-eight RF ablations were performed with 40 W for 10 min using continuous NaCl infusion in fresh excised bovine liver. For perfusion, NaCl concentrations ranging from 0 (demineralized water) to 25% were used. Temperature, the amount of energy, and the dimensions of thermal-induced white coagulation were assessed for each ablation. These parameters were compared using the nonparametric Mann-Whitney test. Correlations were calculated according to the Spearman test. RESULTS: RF ablation performed with 0.9% to 25% concentrations of NaCl produced a mean volume of coagulation of 30.7 +/- 3.8 cm(3), with a mean short-axis diameter of 3.6 +/- 0.2 cm. The mean amount of energy was 21,895 +/- 1,674 W and the mean temperature was 85.4 +/- 12.8 degrees C. Volume of coagulation, short-axis diameter, and amount of energy did not differ significantly among NaCl concentrations (p > 0.5). A correlation was found between the NaCl concentration and the short-axis diameter of coagulation (r = 0.64) and between the NaCl concentration and the mean temperature (r = 0.67), but not between the NaCl concentration and volume of coagulation. CONCLUSION: In an ex vivo model, continuous perfusion with high NaCl concentrations does not significantly improve the volume of thermal-induced coagulation. This may be because the use of a low-power generator cannot sufficiently exploit the potential advantage of better tissue conductivity provided by NaCl perfusion.

Animals↗
PubMedDate not supplied

Normal and pathologic features of the postoperative biliary tract at 3D MR cholangiopancreatography and MR imaging.

Magnetic resonance (MR) imaging with cholangiopancreatographic sequences plays a critical role in evaluating alterations in the biliary tract after surgical procedures such as cholecystectomy, liver transplantation, hepatic resection, and the creation of a biliary-enteric anastomosis. MR cholangiopancreatography, a rapid, noninvasive, and accurate imaging technique for the assessment of early and late complications of hepatobiliary surgery, usually enables the identification of normal and abnormal postoperative changes. In cases of complete obstruction of the bile duct, MR cholangiopancreatography allows analysis of the biliary tract above and below the level of the obstruction, a capability essential for treatment planning and one that is not provided by either endoscopic retrograde cholangiopancreatography or percutaneous transhepatic cholangiography. MR cholangiopancreatography is particularly useful for the evaluation of biliary-enteric anastomoses, for which an endoscopic approach is generally precluded. It also can help detect and localize bile duct strictures and stones and can help accurately classify bile duct injuries. It is useful for detecting bile leaks, although it generally does not directly depict the extravasation of bile. In addition to MR cholangiopancreatography, T1- and T2-weighted MR imaging may be performed to depict extrabiliary soft-tissue structures and abnormalities such as an abscess, tumor recurrence or metastasis, hematoma, or hemobilia. Mangafodipir trisodium-enhanced MR cholangiopancreatography, a recently developed technique that provides a combination of anatomic and functional information, is particularly helpful for documenting bile leaks because it allows a functional evaluation of biliary excretion and may directly depict bile leakage from injured ducts.

Bile Duct Diseases↗