Showing papers by "Eric G. Cavalcanti published in 2001"
TL;DR: In this paper, a technique was developed based on magnetic field measurements to localize hypodermic and sewing needles lost in the human body, with the purpose of surgical extraction.
Abstract: A technique was previously developed, based on magnetic field measurements, to localize hypodermic and sewing needles lost in the human body, with the purpose of surgical extraction. The measurements are performed using a SQUID magnetometer, which detects the magnetic field associated with the remanent magnetization of the needle. The technique allowed easy surgical localization of the needles with good precision in all six clinical cases studied so far. The procedure greatly decreases the surgery time for foreign body extraction, and also reduces the generally high odds of failure. This paper presents an improvement of the original algorithm, which is now independent of any constant magnetic field component, thus overcoming the main experimental difficulty usually found, namely that a SQUID system does not measure absolute fields.
13 citations
TL;DR: In this article, the authors evaluated the possibility of distinguishing between reentrant movement and focal excitation pulse propagation through non-invasive magnetic measurements using a SQUID system, and the results obtained agree with the expected magnetic field behavior according to previous simulated studies based on cellular automata models.
Abstract: The underlying electrical mechanism associated with self-sustained arrhythmias such as cardiac flutter and fibrillation is not completely elucidated. Most of the evidence points towards a reentry path, but the hypothesis of firing of an ectopic focus with high frequency is still being considered. This paper evaluates the possibility of distinguishing between reentrant movement and focal excitation pulse propagation through non-invasive magnetic measurements using a SQUID system. We present experiments performed on rabbit atrial tissues immersed in a nourishing solution and submitted to different propagation patterns. The magnetic measurements were made inside a shielded chamber, by a single-channel low- T c rf-SQUID magnetometer coupled to a second-order axial gradiometer with 1.5 cm diameter coils and 4 cm baseline. The magnetic signals have been processed to yield amplitude maps, which show distinct behavior for the two different propagation mechanisms. The results obtained agree with the expected magnetic field behavior according to previous simulated studies based on cellular automata models. Therefore, the potential of the non-invasive magnetocardiographic technique for distinguishing between the primary possibilities of propagation mechanisms is corroborated, with implications in electrophysiology and clinical diagnostic studies.
3 citations