"Um biossusceptômetro supercondutor AC para quantificar o ferro hepático". / A Superconductor AC Susceptometer to Quantify Liver Iron.
AUTOR(ES)
Antonio Adilton Oliveira Carneiro
DATA DE PUBLICAÇÃO
2001
RESUMO
This work consisted in the development of a system to measure the magnetization of large paramagnetic and diamagnetic samples. The main application was susceptometric measurements of the hepatic tissue for quantification of the iron overload. Iron excess is commonly observed in thalassemic and sickle cell anemia patients who have repeatedly received red blood cell transfusions for prevention or treatment of chronic complications and in patients with hemocromatosis. In normal subjects, iron concentration is usually between 0.1 and 0.5 mg of ferritin by gram of wet tissue (mg ftn/gwet tissue). However, in individuals with the above diseases, it can reach up to 30 mg ftn/gwet tissue. The diamagnetic contribution due to the presence of biological tissues (water, skin, fat, muscle, nerve, bone, etc) is equivalent to the paramagnetic contribution due to the presence of approximately 6 mg ftn/gwet tissue distributed in the hepatic tissue. This intense diamagnetic contribution was makedly reduced by using a water bag coupled to the subjects torso. Measurements in vitro were performed in a phantom composed of a cylindrical acrylic tube, filled with pure water containing a plastic sphere placed off axis to simulate the liver position. The sphere was filled with a Fe3+ solution to simulate different iron concentration present in the liver. Measurements in vivo were performed in thalassemic patients undergoing treatment at the Hemocentro de Ribeirão Preto (HRP) and in normal subjects using two different modalities: with and without the use of the water bag on the torso. The measurements of the magnetization were made using a second order axial gradiometer coupled to a RF SQUID. The sample was magnetized using a homogeneous AC magnetic field. The results confirmed the sensitivity of the technique to quantify levels of hepatic iron in patients with overload, with efficiency of differentiating iron levels equivalent to that found in normal subjects. Automation of instrumentation and data acquisition were done in LabView (National Instruments) and susceptometric models simulations and the signal processing were done in MatLab environment.
ASSUNTO(S)
susceptometry paramagnetism diamagnetismotecido diamagnetism ferro hepático liver iron thalassemia and hemochromatose. susceptometria paramagnetismo talassemia e hemocromatose.
