RESUMO
A technique has been developed, based on magnetic field measurements, to localize, in three dimensions, hypodermic and sewing needles lost in the human body. A theoretical model for the magnetic field generated by needles has been elaborated and experimentally validated. Using this model, the localization technique gives information about needle's centre, orientation and depth. The clinical measurements have been made using a SQUID system, with patients being moved under the sensor with the aid of an X-Y bed. The magnetic field associated with the remanent magnetization of the needle is acquired on-line and mapped over a plane. In all six cases that occurred, the technique allowed surgical localization of the needles with ease and high precision. This procedure can decrease the surgery time for extraction of foreign bodies by a large factor, and also reduce the generally high odds of failure.
Assuntos
Medicina Interna/instrumentação , Magnetismo , Agulhas , Radiografia/métodos , Adolescente , Algoritmos , Braço/diagnóstico por imagem , Criança , Pré-Escolar , Campos Eletromagnéticos , Corpos Estranhos , Humanos , Lactente , Modelos Estatísticos , Pelve/diagnóstico por imagem , Radiografia Abdominal , Aço , Fatores de Tempo , Raios XRESUMO
Com a finalidade de estudar o processo de ativação tecidual durante o "flutter atrial", foi desenvolvido um protocolo experimental para acompanhar de forma controlada a propagação circular da frente de onda de ativação elétrica em tecido isolado de coração de coelho através da técnica não-invasiva de detecção do campo magnético. As medidas foram feitas com blindagem magnética e com parâmetros de posição do tecido sob controle. Estudos da mgnitude e fase dos seis primeiros da série de Fourier foram realizados para melhorar a relação sinal/ruído e através de um processamento por mínimos quadráticos foi localizado o dipolo circular equivalente. A frente de onda de despolarização descreveu um movimento circular, caracterizando o padrão reentrante como mecanismo subjacente à arritmia
Abstract - ln order to study the tissue activation process during atrial flutter, an animal experimentation protocol has been developed to allow controlled studies of circular motion of the evolution front in rabbit atrium tissue through the non-invasive magnetic field detection technique. The measurement were performed inside a shielded chamber with the tissue position parameters under control. Noise-free time series were obtained by using the magnitude and phase of the first six harmonics of the Fourier Series and the position of the center of the equivalent circulating dipole were calculated using a least square procedure. The electrical activation of the tissue indeed appeared to move along a circular path, characterizing the rotating pattern of propagation as the underlying mechanism ofthe arrhythmia.