Complications after liver transplantation: evaluation with magnetic resonance imaging, magnetic resonance cholangiography, and 3-dimensional contrast-enhanced magnetic resonance angiography in a single session.

OBJECTIVE: To evaluate a comprehensive magnetic resonance imaging (MRI) protocol as noninvasive diagnostic modality for simultaneous detection of parenchymal, biliary, and vascular complications after liver transplantation. METHODS: Fifty-two liver transplant recipients suspected to have parenchymal, biliary, and (or) vascular complications underwent our MRI protocol at 1.5T unit using a phased array coil. After preliminary acquisition of axial T1w and T2w sequences, magnetic resonance cholangiography (MRC) was performed through a breath-hold, thin- and thick-slab, single-shot T2w sequence in the coronal plane. Contrast-enhanced magnetic resonance angiography (CEMRA) was obtained using a 3-dimensional coronal spoiled gradient-echo sequence, which enabled acquisition of 32 partitions 2.0 mm thick. A fixed dose of 20 ml gadobenate dimeglumine was administered at 2 mL/s. A post-contrast T1w sequence was also performed. Two observers in conference reviewed source images and 3-dimensional reconstructions to determine the presence of parenchymal, biliary, and vascular complications. MRI findings were correlated with surgery, endoscopic retrograde cholangiography (ERC), biopsy, digital subtraction angiography (DSA), and imaging follow-up. RESULTS: MRI revealed abnormal findings in 32 out of 52 patients (61%), including biliary complications (anastomotic and nonanastomotic strictures, and lithiasis) in 31, vascular disease (hepatic artery stenosis and thrombosis) in 9, and evidence of hepatic abscess and hematoma in 2. ERC confirmed findings of MRC in 30 cases, but suggested disease underestimation in 2. DSA confirmed 7 magnetic resonance angiogram (MRA) findings, but suggested disease overestimation in 2. CONCLUSION: MRI combined with MRC and CEMRA can provide a comprehensive assessment of parenchymal, biliary, and vascular complications in most recipients of liver transplantation

Gadoxetate disodium-enhanced MR cholangiography for evaluation of biliary-enteric anastomoses: Added value beyond conventional T2-Weighted images

OBJECTIVE. The objective of our study was to evaluate image quality and reader confidence in MR cholangiography of bile ducts using conventional T2-weighted MR cholangiography alone in comparison with T2-weighted MR cholangiography and gadoxetate disodium- enhanced MR cholangiography in a series of patients with biliary-enteric anastomosis (BEA). SUBJECTS AND METHODS. Fifty patients with BEA and clinically and sonographically suspected complications underwent 1.5-T MRI. After acquisition of T1- and T2-weighted images, conventional MR cholangiography was performed using 3D fast relaxation fast spinecho (FRFSE) and single-shot fast spin-echo (SSFSE) T2-weighted sequences (image set 1). In each patient, a 3D fat-suppressed Liver Acquisition with Volume Acceleration (LAVA) sequence was performed before and 15, 20, 25, 30, and 40 minutes after IV administration of 0.1 mL/kg of gadoxetate disodium (Primovist) (image set 2). Two radiologists in consensus evaluated image quality in the anatomic segments of the biliary tract and recorded diagnostic confidence scores for image set 1 alone and image sets 1 and 2 together. MRI findings were compared with postsurgical specimen if surgery was performed, conventional cholangiography, or 12 months of imaging follow-up. RESULTS. A significant improvement in image quality for visualization of all biliary segments was found using gadoxetate disodium-enhanced MR cholangiography in comparison with T2-weighted MR cholangiography alone. Readers judged diagnostic confidence of image set 1 alone and image sets 1 and 2 together as very confident in three and 37 cases, confident in 30 and 11, not confident in 14 and one, and not confident at all in three and 1, respectively. Concordance between image set 1 alone and image sets 1 and 2 together and the reference standard results was present in 23 of 50 cases (46%) and 47 of 50 cases (94%), respectively (p < 0.0001). CONCLUSION. Gadoxetate disodium-enhanced MR cholangiography can improve image quality for visualization of the biliary tract and further enhanced the diagnostic performance of conventional T2-weighted MR cholangiography in the evaluation of patients with BEA

Photovoltaic Power Forecasting with Ensemble of Learners: Large Test Case from PV Plants in Italy, Zambia and Australia

Photovoltaic power forecasting is nowadays a very active research topic both for industries and academia [1- 10]. In this paper a hourly day-ahead forecasting approach for photovoltaic (PV) power is described, which is based on a number of machine learning techniques independently trained and then combined in a cooperative ensemble fashion. The results of the single techniques have been in depth analysed and compared, resulting in a superior performance of the cooperative ensemble. A strong contribution of this work is the application to a very large number of PV plants (42 at the date of this paper), for an overall installed nominal power over 110 MW in Italy and over 140 MW in Zambia and Australia. Another contribution is the large historic dataset dimension comprehending years of hourly data from 2014 to 2019, allowing in most cases to test the algorithms in large periods, taking into account seasonality and time varying factors. Moreover the large test case leads to a number of different PV technologies (monocrystalline silicon, polycrystalline silicon, thin-film amorphous silicon and flexible amorphous thin-film silicon) and installations (ground and roof mounting, axis tracking). Examples of studies in the literature that include so large test cases are scarce. This work extends the results of a previous work of the authors [11], where a smaller test case was used and tracking installations were not present

Ischemic-type biliary lesions in liver transplant recipients: evaluation with magnetic resonance cholangiography

We assessed the diagnostic value of magnetic resonance cholangiography (MRC) when evaluating ischemic-type biliary lesions in the follow-up of liver transplant patients. We retrospectively reviewed magnetic resonance imaging and MRC of 28 liver transplant recipients with ischemic changes of the biliary tree. The MR examinations were performed at 1.5 T. After the acquisition of axial T1w and T2w sequences, MRC involved a coronal respiratory-triggered, fat-suppressed, two-dimensional, thin-slab, heavily T2w fast spin-echo sequence, and/or a coronal breath-hold, thin- and thick-slab, single-shot T2w sequence. Eleven patients underwent either surgical reconstruction of the biliary system (n = 4) or liver retransplantation (n = 7); the pathologic specimens were employed as standard of reference. The final diagnosis was obtained through direct cholangiography in the remaining cases. Without knowledge of the surgical, pathologic, and cholangiographic findings, two experienced investigators evaluated in conference the MR images to determine the presence of biliary tract abnormalities. MRC demonstrated strictures involving the hepatic bifurcation and the extrahepatic bile duct of the graft in 26 patients; a concomitant thickening of the biliary wall was described in 18 out of these 26 subjects. MRC also showed sludge or stones formation in the donor common bile duct in 16 out of these patients. In conclusion, MRC allows noninvasive, reliable, assessment of ischemic-type biliary lesions in liver transplant recipients

Secretin-stimulated multi-detector CT versus mangafodipir trisodium-enhanced MR imaging plus MRCP in characterization of non-metastatic solid pancreatic lesions

Background and aim: Our study was aimed to compare multiphasic multi-detector computed tomography after secretin stimulation and mangafodipir trisodium-enhanced magnetic resonance imaging plus MR cholangiopancreatography in the characterization of solid pancreatic lesions. Patients and methods: Forty patients with ultrasound diagnosis of solid pancreatic lesion prospectively underwent both multi-detector computed tomography and magnetic resonance imaging. Three minutes after intravenous administration of secretin, post-contrast computed tomography scans were performed 40, 80, and 180s after contrast medium injection. MR protocol included axial/coronal, thin/thick-slab, single-shot T2w sequences and axial/coronal T1w breath-hold spoiled gradient-echo images before and 30-40 min after intravenous infusion of manganese clipyri-doxal diphosphate. Different observers blindly evaluated the ability of computed tomography and magnetic resonance imaging to characterize focal pancreatic lesions. Surgery, biopsy, and/or follow-up were considered as our diagnostic gold standard. Results: Thirty-five focal pancreatic lesions (adenocarcinoma, n = 18; focal chronic pancreatitis, It = 4; endocrine tumor, n = 6; metastasis, n = 1; cystic tumor, n = 3; indeterminate cystic lesions, n = 3) were present in 34 patients since the remaining 6 subjects showed no pathological finding. Both multi-detector computed tomography and magnetic resonance imaging showed a statistically significant correlation with the gold standard and between themselves in the characterization of 29 solid lesions of the pancreas (p<0.05). Conclusion: Both imaging techniques well correlate to final diagnosis of non-metastatic solid pancreatic lesions and particularly of adenocarcinomas with a slight advantage for mangafodipir trisodiumenhanced magnetic resonance imaging plus MR cholangiopancreatography. (C) 2009 Editrice Gastroenterologica Italiana S.r.I. Published by Elsevier Ltd. All rights reserved

Secretin-stimulated MR cholangio-pancreatography in the evaluation of asymptomatic patients with non-specific pancreatic hyperenzymemia

PURPOSE: To assess the diagnostic value of secretin-stimulated MRCP (SS-MRCP) compared with conventional MRCP in asymptomatic patients with mild elevations of pancreatic enzymes. MATERIALS AND METHODS: Eighty asymptomatic patients with pancreatic hyperenzymemia underwent MR imaging at 1.5T-device (Signa EXCITE, GE Healthcare). After the acquisition of axial T1w,T2w sequences, and conventional MRCP, SS-MRCP was performed using a single-slice coronal breath-hold, thick-slab, SSFSE T2w sequence, repeated every 30s up to 15 min following intravenous injection of secretin (Secrelux, Sanochemia). RESULTS: On the basis of the standards of reference, our final diagnoses were: negative findings (n=23), pancreas divisum (n=22), mild chronic pancreatitis (n=14), inflammatory ampullary stenosis (n=3), juxtapapillary duodenal diverticulum (n=1), small cystic lesions (<1cm) (n=22; 5/22 cases associated with pancreas divisum). The image quality of SS-MRCP was significantly higher than that of conventional MRCP (p<0.0001). Standards of reference did not differ significantly from of SS-MRCP findings (p=0.5), while was statistically different from those of conventional MRCP (p<0.0001). A significant difference was found between conventional MRCP and SS-MRCP findings (p<0.0001). CONCLUSION: In asymptomatic patients with non-specific pancreatic hyperenzymemia SS-MRCP may represent the best non-invasive diagnostic technique, since it gives morphological and functional information