Occupational exposure to static magnetic fields during medical procedures on a 3 T MRI scanner

Abstract

MRI is a medical image device that can produce high resolution images using only three different types of electromagnetic fields. These are a static magnetic field, a gradient magnetic field and a radiofrequency pulse. The human body is electrically conductive and current is induced when any part of it moves through a magnetic field, as explained by Faraday's law of induction. This interaction can result in transient biological symptoms such as magneto phosphenes. The international commission for non-ionising radiation protection recommends exposure to fields not exceeding 2 T for the head and 8 T for limbs. The aim of this study was to assess the workers' exposure at Mater Dei hospital to the static magnetic fields produced by the 3 T MRI scanner. Three class of volunteers were recruited: radiographers, engineers and cleaners. Measurements of magnetic field exposure of the head, torso and wrist were carried out while workers performed their routine tasks around the scanner. The results obtained show that in the case of radiographers and cleaners all measurements recorded are within the stipulated limits. The only incidence when this limit was exceeded was when the engineer was cleaning the inside of the MRI scanner.