Uso do contraste oral negativo em exames de colangiografia por ressonância magnética Use of oral negative contrast agent in magnetic resonance cholangiopancreatography examinations

OBJETIVO: Realizamos estudo prospectivo das vias biliares e pancreáticas através de colangiografia por ressonância magnética, com a utilização de meio de contraste oral negativo. Os nossos objetivos foram verificar se este novo meio de contraste melhora a visualização das vias biliar e pancreática, além de identificar a freqüência de efeitos colaterais ao contraste e sua aceitação pelo paciente. MATERIAL E MÉTODO: Quinze voluntários (oito homens e sete mulheres) com idades variando entre 18 e 54 anos (média de 29 anos), sem queixas ou cirurgias abdominais, foram submetidos a colangiografia por ressonância magnética. Foram realizadas duas seqüências colangiográficas em apnéia, antes e cinco minutos após a ingestão de 300 ml de contraste oral negativo. Os exames foram realizados em equipamento operando a 1,0 T. RESULTADOS: Setenta e três por cento dos voluntários consideraram o gosto ruim ou muito ruim, sugerindo uma aceitação discutível; 27% dos voluntários apresentaram náuseas; 20%, cólicas; 14%, azia ou parestesia labial; e 7%, diarréia. A visualização da via biliar extra-hepática foi considerada melhor após o contraste oral negativo em 9/15 voluntários (60%) e do ducto pancreático principal em todos os cinco em que havia interposição de alças. CONCLUSÃO: O contraste oral negativo melhora a visualização dos ductos hepatocolédoco e pancreático principal em exames de colangiografia por ressonância magnética, apesar da baixa aceitação e dos seus efeitos colaterais.<br>OBJECTIVE: The aim of this prospective study was to investigate the feasibility of using a negative oral contrast agent to null the bowel signal during magnetic resonance cholangiopancreatography. MATERIAL AND METHOD: Fifteen healthy volunteers with no previous history of pancreaticobiliary disease or surgery were imaged with a single-shot fast spin-echo pulse sequence, using a magnetic resonance imaging system operating at 1.0 T. Data acquisition was started before and after administration of oral contrast agent. Using the magnetic resonance images obtained before and after administration of oral contrast agent, the common bile duct, pancreatic duct and papilla were assessed and graded by two radiologists. The frequency of adverse effects and the tolerance of the contrast were also evaluated. RESULTS: All patients that found negative oral contrast agent unpleasant (73% of the cases) tolerated well the oral contrast agent. Adverse effects as abdominal pain and diarrhea were noted in 30% of the patients. In all patients the high signal intensity from the intestinal fluid was completely suppressed. The depictions of the common hepatic duct were slightly improved, whereas the depictions of the choledochus, papilla and pancreatic duct were markedly improved by the negative oral contrast agent administration. CONCLUSION: Negative oral magnetic resonance contrast agent can be an effective and safe contrast media in eliminating signal intensity of the gastrointestinal tract, thus improving the depiction of the biliary system in magnetic resonance cholangiopancreatography

Diagnostic efficacy of MnDPDP in MR imaging of the liver. A phase III multicentre study

PURPOSE: To assess the diagnostic efficacy, safety and tolerability of mangafodipir trisodium (MnDPDP, Teslascan) in MR imaging of the liver. MATERIAL AND METHODS: Eighty-two patients from 4 centres underwent MR imaging with pre-contrast sequences including T1-weighted SE and GRE, and T2-weighted turbo SE sequences. MnDPDP at a dose of 5 mumol/kg b.w. was administered by slow i.v. infusion, and 20-60 min after infusion the T1-weighted SE and GRE sequences were repeated. Diagnostic efficacy was evaluated by counting the number of lesions and by evaluating whether more information for lesion characterisation was available in post-contrast images. Safety and tolerability were assessed by recording adverse events and infusion-related discomfort. RESULTS: Significantly more lesions were found in MnDPDP-enhanced T1-weighted SE and GRE images than in unenhanced images of the same sequences. More lesions were also found in these images compared with T2-weighted images at a level of marginal significance. More information was obtained from MnDPDP-enhanced images in 40 cases. Mild to moderate adverse events were experienced by 17% of the patients. CONCLUSION: MnDPDP-enhanced images can improve lesion detection in the liver and are helpful for lesion characterisation. To obtain optimal diagnostic information of liver lesions T2-weighted images are also valuable. MnDPDP is a safe contrast agent for MR imaging of liver lesions

A Novel Multiscale Methodology forSimulating Tunnel Ventilation Flows duringFire

This paper applies a novel and fast modelling approach to simulate tunnel ventilation flows during fires. The complexity and high cost of full CFD models and the inaccuracies of simplistic zone or analytical models are avoided by efficiently combining mono-dimensional (1D) and CFD (3D) modelling techniques. A simple 1D network approach is used to model tunnel regions where the flow is fully developed (far field), and a detailed CFD representation is used where flow conditions require 3D resolution (near field). This multi-scale method has previously been applied to simulate tunnel ventilation systems including jet fans, vertical shafts and portals (Colella et al., Build Environ 44(12): 2357-2367, 2009) and it is applied here to include the effect of fire. Both direct and indirect coupling strategies are investigated and compared for steady state conditions. The methodology has been applied to a modern tunnel of 7 m diameter and 1.2 km in length. Different fire scenarios ranging from 10 MW to 100 MW are investigated with a variable number of operating jet fans. Comparison of cold flow cases with fire cases provides a quantification of the fire throttling effect, which is seen to be large and to reduce the flow by more than 30% for a 100 MW fire. Emphasis has been given to the discussion of the different coupling procedures and the control of the numerical error. Compared to the full CFD solution, the maximum flow field error can be reduced to less than few percents, but providing a reduction of two orders of magnitude in computational time. The much lower computational cost is of great engineering value, especially for parametric and sensitivity studies required in the design or assessment of ventilation and fire safety system