At the end, this method is applied in a real electromagnetic interference ... The tags with radio frequency identification (RFId) have several advantages in the ...
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Methodology of testing Electromagnetic Interference caused by active RFId applied with Electrocardiography A. P. S. Silva1, A.M. Fukuoka2, C.G. Ribeiro3, F. Tomoda4, K. Camacho5, R. M. A. Almeida6 A. Gibertoni7 1-5
Instituto de Ensino e Pesquisa Israelita Albert Einstein, São Paulo SP 6 Universidade Federal de Itajubá, Itajubá MG 7 Hospital Israelita Albert Einstein, São Paulo SP
The purpose of this study is to describe a test method, based in an ANSI standard, to measure the electromagnetic interference caused by several active RFId tags in medical equipment. At the end, this method is applied in a real electromagnetic interference (EMI) test with an electrocardiograph device (ECG). This study was developed during Clinical Engineer Specialization course as a final work.
Keywords –– ECG, Electrocardiograph, Electromagnetic Interference, RFId. The tags with radio frequency identification (RFId) have several advantages in the control of equipment, especially when concerning traceability and reliability. Their ability to have their content updated without physical contact, open control options that would not be feasible or even it would be impossible in a conventional system. Their use in hospitals is increasing, as the authors can attest in the hospital under this study. This fact carries with it some concerns: how the EMI generated by these tags impacts on the normal operation of electrical equipment? And which are the associated risks using them with medical devices? [1]. This paper presents the testing methodology for EMI as described in the ANSIC63.18-1997[2] and its application due a case study of radiation emanating from RFId tags on an ECG. The standard presents a test to evaluate the susceptibility of medical devices to EMI. The variables involved in the test are the distances from the source and the equipment, the power emanated from the source and the relative position between them [3]. Testers must ensure that each operation mode of the equipment (stand-by, setup and on) is tested. If there is any interference it should be noted. The equipment tested was an ECG (Page Trim Phillips III with a Fluke cardiac simulator). As an acquisition system designed for small electrical potential, the signal received by the ECG may be easily influenced by the electromagnetic field. Because of this sensitivity it is one of the most critical equipment concerning electromagnetic interference. For EMI sources for the test, there were used two AeroScout active tags, with transmission power of 81mW. In the first test a tag was positioned following the standard orientation: at first placed on the left of the equipment at 1m apart from it. It was observed if, during the broadcasts, there was any interference or improper operation. The procedure was repeated for the tag in front and to the right of the equipment. In the second set of tests, the tag was placed at a distance of 0.25m, at all three positions (left, front, right), which represents the minimum safe distance. Because it is common attached the tags to the equipment, we chose to proceed with a third test with no distance at all (0m). It is important to mention that the equipment was tested in three different modes: standby, waiting for configuration and online. Another point investigated was the impact of the variation in the number of tags on the equipment. Thus we chose to redo all the tests with two tags and note if there was any change in the results obtained so far. Counting all the possible variations (3 distances, 3 positions, 3 modes of operation and 2 amounts of tags) were performed a total of 54 tests. In neither of them it was observed any improper operation from the ECG. Small noises were observed by a medical specialist in the ECG exam. Nevertheless, these noises did not cause any impact on the test results to the patient. As conclusions, the authors realize that the ANSIC63.18-1997, presents itself as a simple and easy to perform alternative for searching for EMI problems. However, EMI radiation and its interaction with the equipment are dependent on several external factors so that the non-detection of failure is not synonymous with immunity. Some failures may go unnoticed or even be self corrected by the embedded electronic system. Thus, the authors support the use of the procedure with the exception that this is not sufficient to define a system's immunity to RFId induced noise. REFERENCES [1] B. Christe, E. Cooney, G. Maggioli, D. Doty, R. Frye, J. Short “Testing Potential Interference with RFID Usage in the Patient Care Environment”. Biomedical Instrumentation & Technology 479-484. Nov-Dec 2008. [2] ANSIC63.18-1997 - Ad Hoc Test Method for Estimating EMC of Medical Devices to Specific Radio-Frequency Transmitters – Section 6. [3] E. Iadanza, F. Dori, R. Miniati, E. Corrado “Electromagnetic Interferences (EMI) from Active RFId on Critical Care Equipment” Department of Electronics and Telecommunications, University of Florence, Florence, Italy MEDICON 2010, IFMBE Proceedings 29, pp. 991–994, 2010. MARCH 28 - APRIL 1, 2011, RIO DE JANEIRO, BRAZIL 978-1-61284-918-8/11/$26.00 ©2011 IEEE
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ISBN: 978-1-61284-918-8 IEEE Catalog Number: CFP1118G-ART
